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AuthorTitleYearJournal/ProceedingsReftypeDOI/URL
Daskalakis, E., Aslan, E., Liu, F., Cooper, G., Weightman, A., Koç, B., Blunn, G. and Bartolo, P.J. Composite Scaffolds for Large Bone Defects 2020 Progress in Digital and Physical Manufacturing, pp. 250-257  inproceedings  
Abstract: This paper investigates the use of polymer-ceramic composite scaffolds for bone regeneration. Different ratios between Poly-ε caprolactone (PCL) and Hydroxyapatite (HA) were considered. Scaffolds were produced using two different lay-down patterns (0/90° and 0/45°), and pore sizes (350 µm, 500 µm and 700µm). Compressive and cell proliferation tests are reported. Human adipose derived stem cells (hADSCs) were used for the biological characterization.
BibTeX:
@inproceedings{Daskalakis2020,
  author = {Daskalakis, Evangelos and Aslan, Enes and Liu, Fengyuan and Cooper, Glen and Weightman, Andrew and Koç, Bahattin and Blunn, Gordon and Bartolo, P. J.},
  title = {Composite Scaffolds for Large Bone Defects},
  booktitle = {Progress in Digital and Physical Manufacturing},
  publisher = {Springer International Publishing},
  year = {2020},
  pages = {250--257}
}
Bertana, V., Catania, F., Cocuzza, M., Ferrero, S., Scaltrito, L. and Pirri, C. Medical and biomedical applications of 3D and 4D printed polymer nanocomposites 2020 3D and 4D Printing of Polymer Nanocomposite Materials, pp. 325 - 366  incollection DOI URL 
Abstract: In the last years, 3D printing has found applications in the field of biomedicine thanks to its intrinsic versatile nature. Indeed, since additive manufacturing offers the possibility to manipulate and transform a considerable range of materials under many different conditions, both not-colonized and cells-populated structures can be grown. In detail, nanoparticle-enriched polymeric matrixes have attracted the attention of biologists interested in additively building structures that are able to correctly mimic the extracellular environment. This means not only 3D printing scaffolds for cells maintenance and survival, but also allowing 4D real biological microenvironments in which cells can be actively or passively stimulated and parts of human tissues regenerated by inducing natural cellular behavior.
BibTeX:
@incollection{Bertana2020,
  author = {V. Bertana and F. Catania and M. Cocuzza and S. Ferrero and L. Scaltrito and C.F. Pirri},
  title = {Medical and biomedical applications of 3D and 4D printed polymer nanocomposites},
  booktitle = {3D and 4D Printing of Polymer Nanocomposite Materials},
  publisher = {Elsevier},
  year = {2020},
  pages = {325 - 366},
  url = {http://www.sciencedirect.com/science/article/pii/B9780128168059000119},
  doi = {https://doi.org/10.1016/B978-0-12-816805-9.00011-9}
}
Freeman, FE, Browe, DC, Nulty, J, Von Euw, S, Grayson, WL and Kelly, DJ Biofabrication of multiscale bone extracellular matrix scaffolds for bone tissue engineering. 2019 European Cells & Materials  article DOI URL 
Abstract: Interconnected porosity is critical to the design of regenerative scaffolds, as it permits cell migration, vascularisation and diffusion of nutrients and regulatory molecules inside the scaffold. 3D printing is a promising strategy to achieve this as it allows the control over scaffold pore size, porosity and interconnectivity. Thus, the aim of the present study was to integrate distinct biofabrication strategies to develop a multiscale porous scaffold that was not only mechanically functional at the time of implantation, but also facilitated rapid vascularisation and provided stem cells with appropriate cues to enable their differentiation into osteoblasts. To achieve this, polycaprolactone (PCL) was functionalised with decellularised bone extracellular matrix (ECM), to produce osteoinductive filaments for 3D printing. The addition of bone ECM to the PCL not only increased the mechanical properties of the resulting scaffold, but also increased cellular attachment and enhanced osteogenesis of mesenchymal stem cells (MSCs). In vivo, scaffold pore size determined the level of vascularisation, with a larger filament spacing supporting faster vessel in-growth and more new bone formation. By freeze-drying solubilised bone ECM within these 3D-printed scaffolds, it was possible to introduce a matrix network with microscale porosity that further enhanced cellular attachment in vitro and increased vessel infiltration and overall levels of new bone formation in vivo. To conclude, an "off-the-shelf" multiscale bone-ECM-derived scaffold was developed that was mechanically stable and, once implanted in vivo, will drive vascularisation and, ultimately, lead to bone regeneration.
BibTeX:
@article{Freeman2019,
  author = {Freeman FE, Browe DC, Nulty J, Von Euw S, Grayson WL, Kelly DJ},
  title = {Biofabrication of multiscale bone extracellular matrix scaffolds for bone tissue engineering.},
  journal = {European Cells & Materials},
  year = {2019},
  url = {https://www.ecmjournal.org/papers/vol038/vol038a12.php},
  doi = {https://doi.org/10.22203/eCM.v038a12}
}
Loai, S., Kingston, B.R., Wang, Z., Philpott, D.N., Tao, M. and Cheng, H.-L.M. Clinical Perspectives on 3D Bioprinting Paradigms for Regenerative Medicine 2019 Regen Med Front.
Vol. 1(e190004), pp. e190004 
article DOI URL 
BibTeX:
@article{Loai2019,
  author = {Loai, Sadi and Kingston, Benjamin R. and Wang, Zongjie and Philpott, David N. and Tao, Mingyang and Cheng, Hai-Ling Margaret},
  title = {Clinical Perspectives on 3D Bioprinting Paradigms for Regenerative Medicine},
  journal = {Regen Med Front.},
  publisher = {Hapres},
  year = {2019},
  volume = {1},
  number = {e190004},
  pages = {e190004},
  url = {https://rmf.hapres.com/htmls/RMF_1058_Detail.html},
  doi = {https://doi.org/10.20900/rmf20190004}
}
Geetha Bai, R., Muthoosamy, K., Manickam, S. and Hilal-Alnaqbi, A. Graphene-based 3D scaffolds in tissue engineering: fabrication, applications, and future scope in liver tissue engineering 2019 International journal of nanomedicine
Vol. 14(31413573), pp. 5753-5783 
article URL 
Abstract: Tissue engineering embraces the potential of recreating and replacing defective body parts by advancements in the medical field. Being a biocompatible nanomaterial with outstanding physical, chemical, optical, and biological properties, graphene-based materials were successfully employed in creating the perfect scaffold for a range of organs, starting from the skin through to the brain. Investigations on 2D and 3D tissue culture scaffolds incorporated with graphene or its derivatives have revealed the capability of this carbon material in mimicking in vivo environment. The porous morphology, great surface area, selective permeability of gases, excellent mechanical strength, good thermal and electrical conductivity, good optical properties, and biodegradability enable graphene materials to be the best component for scaffold engineering. Along with the apt microenvironment, this material was found to be efficient in differentiating stem cells into specific cell types. Furthermore, the scope of graphene nanomaterials in liver tissue engineering as a promising biomaterial is also discussed. This review critically looks into the unlimited potential of graphene-based nanomaterials in future tissue engineering and regenerative therapy.
BibTeX:
@article{GeethaBai2019,
  author = {Geetha Bai, Renu and Muthoosamy, Kasturi and Manickam, Sivakumar and Hilal-Alnaqbi, Ali},
  title = {Graphene-based 3D scaffolds in tissue engineering: fabrication, applications, and future scope in liver tissue engineering},
  journal = {International journal of nanomedicine},
  publisher = {Dove},
  year = {2019},
  volume = {14},
  number = {31413573},
  pages = {5753--5783},
  url = {https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6662516/}
}
Zhuang, P., Ng, W.L., An, J., Chua, C.K. and Tan, L.P. Layer-by-layer ultraviolet assisted extrusion-based (UAE) bioprinting of hydrogel constructs with high aspect ratio for soft tissue engineering applications 2019 PLOS ONE
Vol. 14(6), pp. 1-21 
article DOI  
Abstract: One of the major challenges in the field of soft tissue engineering using bioprinting is fabricating complex tissue constructs with desired structure integrity and mechanical property. To accomplish such requirements, most of the reported works incorporated reinforcement materials such as poly(ϵ-caprolactone) (PCL) polymer within the 3D bioprinted constructs. Although this approach has made some progress in constructing soft tissue-engineered scaffolds, the mechanical compliance mismatch and long degradation period are not ideal for soft tissue engineering. Herein, we present a facile bioprinting strategy that combines the rapid extrusion-based bioprinting technique with an in-built ultraviolet (UV) curing system to facilitate the layer-by-layer UV curing of bioprinted photo-curable GelMA-based hydrogels to achieve soft yet stable cell-laden constructs with high aspect ratio for soft tissue engineering. GelMA is supplemented with a viscosity enhancer (gellan gum) to improve the bio-ink printability and shape fidelity while maintaining the biocompatibility before crosslinking via a layer-by-layer UV curing process. This approach could eventually fabricate soft tissue constructs with high aspect ratio (length to diameter) of ≥ 5. The effects of UV source on printing resolution and cell viability were also studied. As a proof-of-concept, small building units (3D lattice and tubular constructs) with high aspect ratio are fabricated. Furthermore, we have also demonstrated the ability to perform multi-material printing of tissue constructs with high aspect ratio along both the longitudinal and transverse directions for potential applications in tissue engineering of soft tissues. This layer-by-layer ultraviolet assisted extrusion-based (UAE) Bioprinting may provide a novel strategy to develop soft tissue constructs with desirable structure integrity.
BibTeX:
@article{Zhuang2019,
  author = {Zhuang, Pei AND Ng, Wei Long AND An, Jia AND Chua, Chee Kai AND Tan, Lay Poh},
  title = {Layer-by-layer ultraviolet assisted extrusion-based (UAE) bioprinting of hydrogel constructs with high aspect ratio for soft tissue engineering applications},
  journal = {PLOS ONE},
  publisher = {Public Library of Science},
  year = {2019},
  volume = {14},
  number = {6},
  pages = {1-21},
  doi = {https://doi.org/10.1371/journal.pone.0216776}
}
Noor, N., Shapira, A., Edri, R., Gal, I., Wertheim, L. and Dvir, T. 3D Printing of Personalized Thick and Perfusable Cardiac Patches and Hearts 2019 Advanced Science
Vol. 0(0), pp. 1900344 
article DOI  
Abstract: Abstract Generation of thick vascularized tissues that fully match the patient still remains an unmet challenge in cardiac tissue engineering. Here, a simple approach to 3D-print thick, vascularized, and perfusable cardiac patches that completely match the immunological, cellular, biochemical, and anatomical properties of the patient is reported. To this end, a biopsy of an omental tissue is taken from patients. While the cells are reprogrammed to become pluripotent stem cells, and differentiated to cardiomyocytes and endothelial cells, the extracellular matrix is processed into a personalized hydrogel. Following, the two cell types are separately combined with hydrogels to form bioinks for the parenchymal cardiac tissue and blood vessels. The ability to print functional vascularized patches according to the patient's anatomy is demonstrated. Blood vessel architecture is further improved by mathematical modeling of oxygen transfer. The structure and function of the patches are studied in vitro, and cardiac cell morphology is assessed after transplantation, revealing elongated cardiomyocytes with massive actinin striation. Finally, as a proof of concept, cellularized human hearts with a natural architecture are printed. These results demonstrate the potential of the approach for engineering personalized tissues and organs, or for drug screening in an appropriate anatomical structure and patient-specific biochemical microenvironment.
BibTeX:
@article{Noor2019,
  author = {Noor, Nadav and Shapira, Assaf and Edri, Reuven and Gal, Idan and Wertheim, Lior and Dvir, Tal},
  title = {3D Printing of Personalized Thick and Perfusable Cardiac Patches and Hearts},
  journal = {Advanced Science},
  year = {2019},
  volume = {0},
  number = {0},
  pages = {1900344},
  doi = {https://doi.org/10.1002/advs.201900344}
}
Markstedt, K., Håkansson, K., Toriz, G. and Gatenholm, P. Materials from trees assembled by 3D printing – Wood tissue beyond nature limits 2019 Applied Materials Today
Vol. 15, pp. 280 - 285 
article DOI URL 
Abstract: Materials from trees have the potential to replace fossil based and other non-sustainable materials in everyday products, thus transforming the society back to a bioeconomy. This paper presents a 3D printing platform which mimics wood biogenesis for the assembly of wood biopolymers into wood-like hierarchical composites. The genome was substituted with G-code, the programming language which controls how the 3D printer assembles material. The rosette was replaced by the printer head for extrusion of cellulose. Instead of microtubules guiding the alignment of cellulose, the printing direction was guided by an x/y stage, thus mimicking the microfibril angle. The printed structures were locked by an enzymatic crosslinking reaction similar to what occurs in the cell wall upon lignification. Hierarchical structures characteristic for wood were designed and printed with control of density, swelling and directional strength. Accelerating the development of the 3D printing technology helps realize the circular bioeconomy where garments, packaging, furniture and entire houses are manufactured by 3D printing wood.
BibTeX:
@article{Markstedt2019,
  author = {Kajsa Markstedt and Karl Håkansson and Guillermo Toriz and Paul Gatenholm},
  title = {Materials from trees assembled by 3D printing – Wood tissue beyond nature limits},
  journal = {Applied Materials Today},
  year = {2019},
  volume = {15},
  pages = {280 - 285},
  url = {http://www.sciencedirect.com/science/article/pii/S2352940718304918},
  doi = {https://doi.org/10.1016/j.apmt.2019.02.005}
}
Huang, B., Vyas, C., Roberts, I., Poutrel, Q.-A., Chiang, W.-H., Blaker, J.J., Huang, Z. and Bártolo, P. Fabrication and characterisation of 3D printed MWCNT composite porous scaffolds for bone regeneration 2019 Materials Science and Engineering: C
Vol. 98, pp. 266 - 278 
article DOI URL 
Abstract: Carbon nanotubes (CNTs) with exceptional physical and chemical properties are attracting significant interest in the field of tissue engineering. Several reports investigated CNTs biocompatibility and their impact in terms of cell attachment, proliferation and differentiation mainly using polymer/CNTs membranes. However, these 2D membranes are not able to emulate the complex in vivo environment. In this paper, additive manufacturing (3D printing) is used to create composite 3D porous scaffolds containing different loadings of multi-walled carbon nanotubes (MWCNT) (0.25, 0.75 and 3 wt%) for bone tissue regeneration. Pre-processed and processed materials were extensively characterised in terms of printability, morphological and topographic characteristics and thermal, mechanical and biological properties. Scaffolds with pore sizes ranging between 366 μm and 397 μm were successfully produced and able to sustain early-stage human adipose-derived mesenchymal stem cells attachment and proliferation. Results show that MWCNTs enhances protein adsorption, mechanical and biological properties. Composite scaffolds, particularly the 3 wt% loading of MWCNTs, seem to be good candidates for bone tissue regeneration.
BibTeX:
@article{Huang2019,
  author = {Boyang Huang and Cian Vyas and Iwan Roberts and Quentin-Arthur Poutrel and Wei-Hung Chiang and Jonny J. Blaker and Zhucheng Huang and Paulo Bártolo},
  title = {Fabrication and characterisation of 3D printed MWCNT composite porous scaffolds for bone regeneration},
  journal = {Materials Science and Engineering: C},
  year = {2019},
  volume = {98},
  pages = {266 - 278},
  url = {http://www.sciencedirect.com/science/article/pii/S0928493118317491},
  doi = {https://doi.org/10.1016/j.msec.2018.12.100}
}
Gonzalez-Fernandez, T., Rathan, S., Hobbs, C., Pitacco, P., Freeman, F., Cunniffe, G., Dunne, N., McCarthy, H., Nicolosi, V., O'Brien, F. and Kelly, D. Pore-forming bioinks to enable Spatio-temporally defined gene delivery in bioprinted tissues 2019 Journal of Controlled Release  article DOI URL 
Abstract: The regeneration of complex tissues and organs remains a major clinical challenge. With a view towards bioprinting such tissues, we developed a new class of pore-forming bioink to spatially and temporally control the presentation of therapeutic genes within bioprinted tissues. By blending sacrificial and stable hydrogels, we were able to produce bioinks whose porosity increased with time following printing. When combined with amphipathic peptide-based plasmid DNA delivery, these bioinks supported enhanced non-viral gene transfer to stem cells in vitro. By modulating the porosity of these bioinks, it was possible to direct either rapid and transient (pore-forming bioinks), or slower and more sustained (solid bioinks) transfection of host or transplanted cells in vivo. To demonstrate the utility of these bioinks for the bioprinting of spatially complex tissues, they were next used to zonally position stem cells and plasmids encoding for either osteogenic (BMP2) or chondrogenic (combination of TGF-β3, BMP2 and SOX9) genes within networks of 3D printed thermoplastic fibers to produce mechanically reinforced, gene activated constructs. In vivo, these bioprinted tissues supported the development of a vascularised, bony tissue overlaid by a layer of stable cartilage. When combined with multiple-tool biofabrication strategies, these gene activated bioinks can enable the bioprinting of a wide range of spatially complex tissues.
BibTeX:
@article{Gonzalez-Fernandez2019,
  author = {T. Gonzalez-Fernandez and S. Rathan and C. Hobbs and P. Pitacco and F.E. Freeman and G.M. Cunniffe and N.J. Dunne and H.O. McCarthy and V. Nicolosi and F.J. O'Brien and D.J. Kelly},
  title = {Pore-forming bioinks to enable Spatio-temporally defined gene delivery in bioprinted tissues},
  journal = {Journal of Controlled Release},
  year = {2019},
  url = {http://www.sciencedirect.com/science/article/pii/S0168365919301440},
  doi = {https://doi.org/10.1016/j.jconrel.2019.03.006}
}
Gloria, A., Frydman, B., Lamas, M.L., Serra, A.C., Martorelli, M., Coelho, J.F., Fonseca, A.C. and Domingos, M. The influence of poly(ester amide) on the structural and functional features of 3D additive manufactured poly(ε-caprolactone) scaffolds 2019 Materials Science and Engineering: C
Vol. 98, pp. 994 - 1004 
article DOI URL 
Abstract: The current research reports for the first time the use of blends of poly(ε-caprolactone) (PCL) and poly(ester amide) (PEA) for the fabrication of 3D additive manufactured scaffolds. Tailor made PEA was synthesized to afford fully miscible blends of PCL and PEA using different percentages (5, 10, 15 and 20% w/w). Stability, characteristic temperatures and material's compatibility were studied through thermal analyses (i.e., TGA, DSC). Even though DMTA and static compression tests demonstrated the possibility to improve the storage modulus, Young's modulus and maximum stress by increasing the amount of PEA, a decrease of hardness was found beyond a threshold concentration of PEA as the lowest values were achieved for PCL/PEA (20% w/w) scaffolds (from 0.39 ± 0.03 GPa to 0.21 ± 0.02 GPa in the analysed load range). The scaffolds presented a controlled morphology and a fully interconnected network of internal channels. The water contact angle measurements showed a clear increase of hydrophilicity resulting from the addition of PEA. This result was further corroborated with the improved adhesion and proliferation of human mesenchymal stem cells (hMSCs). The presence of PEA also influenced the cell morphology. Better cell spreading and a much higher and homogenous number of cells were observed for PCL/PEA scaffolds when compared to PCL ones.
BibTeX:
@article{Gloria2019,
  author = {Antonio Gloria and B. Frydman and Miguel L. Lamas and Armenio C. Serra and Massimo Martorelli and Jorge F.J. Coelho and Ana C. Fonseca and M. Domingos},
  title = {The influence of poly(ester amide) on the structural and functional features of 3D additive manufactured poly(ε-caprolactone) scaffolds},
  journal = {Materials Science and Engineering: C},
  year = {2019},
  volume = {98},
  pages = {994 - 1004},
  url = {http://www.sciencedirect.com/science/article/pii/S0928493118323944},
  doi = {https://doi.org/10.1016/j.msec.2019.01.063}
}
Apelgren, P., Karabulut, E., Amoroso, M., Mantas, A., Martínez Ávila, H., Kölby, L., Kondo, T., Toriz, G. and Gatenholm, P. In Vivo Human Cartilage Formation in Three-Dimensional Bioprinted Constructs with a Novel Bacterial Nanocellulose Bioink 2019 ACS Biomater. Sci. Eng.
Vol. 5(5), pp. 2482-2490 
article DOI  
Abstract: Bacterial nanocellulose (BNC) is a 3D network of nanofibrils exhibiting excellent biocompatibility. Here, we present the aqueous counter collision (ACC) method of BNC disassembly to create bioink with suitable properties for cartilage-specific 3D-bioprinting. BNC was disentangled by ACC, and fibril characteristics were analyzed. Bioink printing fidelity and shear-thinning properties were evaluated. Cell-laden bioprinted grid constructs (5 × 5 × 1 mm3) containing human nasal chondrocytes (10 M mL-1) were implanted in nude mice and explanted after 30 and 60 days. Both ACC and hydrolysis resulted in significantly reduced fiber lengths, with ACC resulting in longer fibrils and fewer negative charges relative to hydrolysis. Moreover, ACC-BNC bioink showed outstanding printability, postprinting mechanical stability, and structural integrity. In vivo, cell-laden structures were rapidly integrated, maintained structural integrity, and showed chondrocyte proliferation, with 32.8 ± 13.8 cells per mm2 observed after 30 days and 85.6 ± 30.0 cells per mm2 at day 60 (p = 0.002). Furthermore, a full-thickness skin graft was attached and integrated completely on top of the 3D-bioprinted construct. The novel ACC disentanglement technique makes BNC biomaterial highly suitable for 3D-bioprinting and clinical translation, suggesting cell-laden 3D-bioprinted ACC-BNC as a promising solution for cartilage repair.
Bacterial nanocellulose (BNC) is a 3D network of nanofibrils exhibiting excellent biocompatibility. Here, we present the aqueous counter collision (ACC) method of BNC disassembly to create bioink with suitable properties for cartilage-specific 3D-bioprinting. BNC was disentangled by ACC, and fibril characteristics were analyzed. Bioink printing fidelity and shear-thinning properties were evaluated. Cell-laden bioprinted grid constructs (5 × 5 × 1 mm3) containing human nasal chondrocytes (10 M mL-1) were implanted in nude mice and explanted after 30 and 60 days. Both ACC and hydrolysis resulted in significantly reduced fiber lengths, with ACC resulting in longer fibrils and fewer negative charges relative to hydrolysis. Moreover, ACC-BNC bioink showed outstanding printability, postprinting mechanical stability, and structural integrity. In vivo, cell-laden structures were rapidly integrated, maintained structural integrity, and showed chondrocyte proliferation, with 32.8 ± 13.8 cells per mm2 observed after 30 days and 85.6 ± 30.0 cells per mm2 at day 60 (p = 0.002). Furthermore, a full-thickness skin graft was attached and integrated completely on top of the 3D-bioprinted construct. The novel ACC disentanglement technique makes BNC biomaterial highly suitable for 3D-bioprinting and clinical translation, suggesting cell-laden 3D-bioprinted ACC-BNC as a promising solution for cartilage repair.
BibTeX:
@article{Apelgren2019,
  author = {Apelgren, Peter and Karabulut, Erdem and Amoroso, Matteo and Mantas, Athanasios and Martínez Ávila, Héctor and Kölby, Lars and Kondo, Tetsuo and Toriz, Guillermo and Gatenholm, Paul},
  title = {In Vivo Human Cartilage Formation in Three-Dimensional Bioprinted Constructs with a Novel Bacterial Nanocellulose Bioink},
  journal = {ACS Biomater. Sci. Eng.},
  publisher = {American Chemical Society},
  year = {2019},
  volume = {5},
  number = {5},
  pages = {2482--2490},
  doi = {https://doi.org/10.1021/acsbiomaterials.9b00157}
}
Mehrotra, S., Moses, J.C., Bandyopadhyay, A. and Mandal, B.B. 3D Printing/Bioprinting Based Tailoring of in Vitro Tissue Models: Recent Advances and Challenges 2019 ACS Appl. Bio Mater.
Vol. 2(4), pp. 1385-1405 
article DOI  
Abstract: Prodigious progress in the past decade has pronounced 3D printing as one of the most promising technique for assembling biological materials in a complex layout that mimics native human tissues. With the advent of technology, several improvements in printing techniques have facilitated the development of intricate strategies and designs that were imaginably distant due to the conventional top-down approaches. Most of these advanced strategies generally follow a thorough coordination and an elaborate biomimetic blueprint due to which it is now possible to fabricate in vitro tissue models with ease. However, much remains to be accomplished at several forefronts for utilizing this technology to its full potential. With several printing strategies at the lead, it has now become essential to systematically analyze and learn from several endeavors such that shortcomings can be understood and future efforts can be made toward negating them. Taking account of all the recent tissue specific developments in this field, this review serves as a framework for bringing together in discussion several strategies and constraints in developing small scaled in vitro tissues. Highlighting the growing popularity of the organ and body on chip platforms and their easy scale up using 3D printing, latest advancements, and the challenges in this field are also discussed.
Prodigious progress in the past decade has pronounced 3D printing as one of the most promising technique for assembling biological materials in a complex layout that mimics native human tissues. With the advent of technology, several improvements in printing techniques have facilitated the development of intricate strategies and designs that were imaginably distant due to the conventional top-down approaches. Most of these advanced strategies generally follow a thorough coordination and an elaborate biomimetic blueprint due to which it is now possible to fabricate in vitro tissue models with ease. However, much remains to be accomplished at several forefronts for utilizing this technology to its full potential. With several printing strategies at the lead, it has now become essential to systematically analyze and learn from several endeavors such that shortcomings can be understood and future efforts can be made toward negating them. Taking account of all the recent tissue specific developments in this field, this review serves as a framework for bringing together in discussion several strategies and constraints in developing small scaled in vitro tissues. Highlighting the growing popularity of the organ and body on chip platforms and their easy scale up using 3D printing, latest advancements, and the challenges in this field are also discussed.
BibTeX:
@article{Mehrotra2019,
  author = {Mehrotra, Shreya and Moses, Joseph Christakiran and Bandyopadhyay, Ashutosh and Mandal, Biman B.},
  title = {3D Printing/Bioprinting Based Tailoring of in Vitro Tissue Models: Recent Advances and Challenges},
  journal = {ACS Appl. Bio Mater.},
  publisher = {American Chemical Society},
  year = {2019},
  volume = {2},
  number = {4},
  pages = {1385--1405},
  doi = {https://doi.org/10.1021/acsabm.9b00073}
}
Allig, S., Mayer, M., Arrizabalaga, O., Ritter, S., Schroeder, I. and Thielemann, C. Effect of extrusion-based bioprinting on neurospheres 2019 GSI-FAIR SCIENTIFIC REPORT 2017School: University of Applied Sciences, BioMEMS Lab, Aschaffenburg, Germany  techreport URL 
BibTeX:
@techreport{Allig2019,
  author = {Allig, Sebastian and Mayer, Margot and Arrizabalaga, Onetsine and Ritter, Sylvia and Schroeder, Insa and Thielemann, Christiane},
  title = {Effect of extrusion-based bioprinting on neurospheres},
  booktitle = {GSI-FAIR SCIENTIFIC REPORT 2017},
  school = {University of Applied Sciences, BioMEMS Lab, Aschaffenburg, Germany},
  year = {2019},
  url = {https://www.researchgate.net/publication/332672473_Effect_of_extrusion-based_bioprinting_on_neurospheres}
}
Marques, C.F., Diogo, G.S., Pina, S., Oliveira, J.M., Silva, T.H. and Reis, R.L. Collagen-based bioinks for hard tissue engineering applications: a comprehensive review 2019 Journal of Materials Science: Materials in Medicine
Vol. 30(3), pp. 32 
article DOI  
Abstract: In the last few years, additive manufacturing (AM) has been gaining great interest in the fabrication of complex structures for soft-to-hard tissues regeneration, with tailored porosity, and boosted structural, mechanical, and biological properties. 3D printing is one of the most known AM techniques in the field of biofabrication of tissues and organs. This technique opened up opportunities over the conventional ones, with the capability of creating replicable, customized, and functional structures that can ultimately promote effectively different tissues regeneration. The uppermost component of 3D printing is the bioink, i.e. a mixture of biomaterials that can also been laden with different cell types, and bioactive molecules. Important factors of the fabrication process include printing fidelity, stability, time, shear-thinning properties, mechanical strength and elasticity, as well as cell encapsulation and cell-compatible conditions. Collagen-based materials have been recognized as a promising choice to accomplish an ideal mimetic bioink for regeneration of several tissues with high cell-activating properties. This review presents the state-of-art of the current achievements on 3D printing using collagen-based materials for hard tissue engineering, particularly on the development of scaffolds for bone and cartilage repair/regeneration. The ultimate aim is to shed light on the requirements to successfully print collagen-based inks and the most relevant properties exhibited by the so fabricated scaffolds. In this regard, the adequate bioprinting parameters are addressed, as well as the main materials properties, namely physicochemical and mechanical properties, cell compatibility and commercial availability, covering hydrogels, microcarriers and decellularized matrix components. Furthermore, the fabrication of these bioinks with and without cells used in inkjet printing, laser-assisted printing, and direct in writing technologies are also overviewed. Finally, some future perspectives of novel bioinks are given.
BibTeX:
@article{Marques2019,
  author = {Marques, C. F. and Diogo, G. S. and Pina, S. and Oliveira, J. M. and Silva, T. H. and Reis, R. L.},
  title = {Collagen-based bioinks for hard tissue engineering applications: a comprehensive review},
  journal = {Journal of Materials Science: Materials in Medicine},
  year = {2019},
  volume = {30},
  number = {3},
  pages = {32},
  doi = {https://doi.org/10.1007/s10856-019-6234-x}
}
Zhou, M., Lee, B.H., Tan, Y.J. and Tan, L.P. Microbial transglutaminase induced controlled crosslinking of gelatin methacryloyl to tailor rheological properties for 3D printing 2019 Biofabrication
Vol. 11(2), pp. 025011 
article DOI  
Abstract: Gelatin methacryloyl (GelMA) is a versatile biomaterial that has been shown to possess many advantages such as good biocompatibility, support for cell growth, tunable mechanical properties, photocurable capability, and low material cost. Due to these superior properties, much research has been carried out to develop GelMA as a bioink for bioprinting. However, there are still many challenges, and one major challenge is the control of its rheological properties to yield good printability. Herein, this study presents a strategy to control the rheology of GelMA through partial enzymatic crosslinking. Unlike other enzymatic crosslinking strategies where the rheological properties could not be controlled once reaction takes place, we could, to a large extent, keep the rheological properties stable by introducing a deactivation step after obtaining the optimized rheological properties. Ca2+-independent microbial transglutaminase (MTGase) was introduced to partially catalyze covalent bond formation between chains of GelMA. The enzyme was then deactivated to prevent further uncontrolled crosslinking that would render the hydrogel not printable. After printing, a secondary post-printing crosslinking step (photo crosslinking) was then introduced to ensure long-term stability of the printed structure for subsequent cell studies. Biocompatibility studies carried out using cells encapsulated in the printed structure showed excellent cell viability for at least 7 d. This strategy for better control of rheological properties of GelMA could more significantly enhance the usability of this material as bioink for bioprinting of cell-laden structures for soft tissue engineering.
BibTeX:
@article{Zhou2019,
  author = {Miaomiao Zhou and Bae Hoon Lee and Yu Jun Tan and Lay Poh Tan},
  title = {Microbial transglutaminase induced controlled crosslinking of gelatin methacryloyl to tailor rheological properties for 3D printing},
  journal = {Biofabrication},
  publisher = {IOP Publishing},
  year = {2019},
  volume = {11},
  number = {2},
  pages = {025011},
  doi = {https://doi.org/10.1088/1758-5090/ab063f}
}
Rotbaum, Y., Puiu, C., Rittel, D. and Domingos, M. Quasi-static and dynamic in vitro mechanical response of 3D printed scaffolds with tailored pore size and architectures 2019 Materials Science and Engineering: C
Vol. 96, pp. 176 - 182 
article DOI URL 
Abstract: Scaffold-based Tissue Engineering represents the most promising approach for the regeneration of load bearing skeletal tissues, in particular bone and cartilage. Scaffolds play major role in this process by providing a physical template for cells to adhere and proliferate whilst ensuring an adequate biomechanical support at the defect site. Whereas the quasi static mechanical properties of porous polymeric scaffolds are well documented, the response of these constructs under high strain compressive rates remain poorly understood. Therefore, this study investigates, for the first time, the influence of pore size and geometry on the mechanical behaviour of Polycaprolactone (PCL) scaffolds under quasi static and dynamic conditions. 3D printed scaffolds with varied pore sizes and geometries were obtained using different filament distances (FD) and lay-down patterns, respectively. In particular, by fixing the lay-down pattern at 0/90° and varying the FD between 480 and 980 μm it was possible to generate scaffolds with square pores with dimensions in the range of 150–650 μm and porosities of 59–79%. On the other hand, quadrangular, hexagonal, triangular and complex pore geometries with constant porosity (approx. 70%) were obtained at a fixed FD of 680 μm and imposing four different lay-down patterns of 0/90, 0/60/120, 0/45/90/135 and 0/30/60/90/120/150°, respectively. The mechanical response of printed scaffolds was assessed under two different compression loading regimes spanning five distinct strain rates, from 10−2 to 2000 s−1, using two different apparatus: a conventional screw-driven testing machine (Instron 4483) and a Split Hopkinson pressure bar (SHPB) equipped with a set of A201 Flexi-force™ (FF) force sensors and a pulse shaper. Our results show that the mechanical properties of PCL scaffolds are not strain rate sensitive between 1300 and 2000 s−1 and these strongly depend on the pore size (porosity) rather than pore geometry. Those findings are extremely relevant for the engineering of bone tissue scaffolds with enhanced mechanical stability by providing new data describing the mechanical response of these constructs at high strain rates as well as the at the transition between quasi static and dynamic regimes.
BibTeX:
@article{Rotbaum2019,
  author = {Y. Rotbaum and C. Puiu and D. Rittel and M. Domingos},
  title = {Quasi-static and dynamic in vitro mechanical response of 3D printed scaffolds with tailored pore size and architectures},
  journal = {Materials Science and Engineering: C},
  year = {2019},
  volume = {96},
  pages = {176 - 182},
  url = {http://www.sciencedirect.com/science/article/pii/S0928493118326651},
  doi = {https://doi.org/10.1016/j.msec.2018.11.019}
}
Pedrotty, D.M., Volodymyr, K., Erdem, K., Sugrue Alan, M., Christopher, L., Vaidya Vaibhav, R., McLeod Christopher, J., Asirvatham Samuel, J., Paul, G. and Suraj, K. Three-Dimensional Printed Biopatches With Conductive Ink Facilitate Cardiac Conduction When Applied to Disrupted Myocardium 2019 Circulation: Arrhythmia and Electrophysiology
Vol. 12(3), pp. e006920 
article DOI  
BibTeX:
@article{Pedrotty2019,
  author = {Pedrotty, Dawn M. and Volodymyr, Kuzmenko and Erdem, Karabulut and Sugrue Alan, M. and Christopher, Livia and Vaidya Vaibhav, R. and McLeod Christopher, J. and Asirvatham Samuel, J. and Paul, Gatenholm and Suraj, Kapa},
  title = {Three-Dimensional Printed Biopatches With Conductive Ink Facilitate Cardiac Conduction When Applied to Disrupted Myocardium},
  journal = {Circulation: Arrhythmia and Electrophysiology},
  publisher = {American Heart Association},
  year = {2019},
  volume = {12},
  number = {3},
  pages = {e006920},
  doi = {https://doi.org/10.1161/circep.118.006920}
}
Jiang, T., Munguía López, J., Flores-Torres, S., Kort-Mascort, J. and Kinsella, J. Extrusion bioprinting of soft materials: An emerging technique for biological model fabrication 2019 Applied Physics Reviews
Vol. 6, pp. 011310 
article DOI  
BibTeX:
@article{Jiang2019,
  author = {Jiang, Tao and Munguía López, Jose and Flores-Torres, Salvador and Kort-Mascort, Jacqueline and Kinsella, Joseph},
  title = {Extrusion bioprinting of soft materials: An emerging technique for biological model fabrication},
  journal = {Applied Physics Reviews},
  year = {2019},
  volume = {6},
  pages = {011310},
  doi = {https://doi.org/10.1063/1.5059393}
}
Filardo, G., Petretta, M., Cavallo, C., Roseti, L., Durante, S., Albisinni, U. and Grigolo, B. Patient-specific meniscus prototype based on 3D bioprinting of human cell-laden scaffold 2019 Bone & Joint Research
Vol. 8(2), pp. 101-106 
article DOI  
Abstract: Objectives Meniscal injuries are often associated with an active lifestyle. The damage of meniscal tissue puts young patients at higher risk of undergoing meniscal surgery and, therefore, at higher risk of osteoarthritis. In this study, we undertook proof-of-concept research to develop a cellularized human meniscus by using 3D bioprinting technology. Methods A 3D model of bioengineered medial meniscus tissue was created, based on MRI scans of a human volunteer. The Digital Imaging and Communications in Medicine (DICOM) data from these MRI scans were processed using dedicated software, in order to obtain an STL model of the structure. The chosen 3D Discovery printing tool was a microvalve-based inkjet printhead. Primary mesenchymal stem cells (MSCs) were isolated from bone marrow and embedded in a collagen-based bio-ink before printing. LIVE/DEAD assay was performed on realized cell-laden constructs carrying MSCs in order to evaluate cell distribution and viability. Results This study involved the realization of a human cell-laden collagen meniscus using 3D bioprinting. The meniscus prototype showed the biological potential of this technology to provide an anatomically shaped, patient-specific construct with viable cells on a biocompatible material. Conclusion This paper reports the preliminary findings of the production of a custom-made, cell-laden, collagen-based human meniscus. The prototype described could act as the starting point for future developments of this collagen-based, tissue-engineered structure, which could aid the optimization of implants designed to replace damaged menisci. Cite this article: G. Filardo, M. Petretta, C. Cavallo, L. Roseti, S. Durante, U. Albisinni, B. Grigolo. Patient-specific meniscus prototype based on 3D bioprinting of human cell-laden scaffold. Bone Joint Res 2019;8:101–106. DOI: 10.1302/2046-3758.82.BJR-2018-0134.R1.
BibTeX:
@article{Filardo2019,
  author = {Filardo, G. and Petretta, M. and Cavallo, C. and Roseti, L. and Durante, S. and Albisinni, U. and Grigolo, B.},
  title = {Patient-specific meniscus prototype based on 3D bioprinting of human cell-laden scaffold},
  journal = {Bone & Joint Research},
  year = {2019},
  volume = {8},
  number = {2},
  pages = {101-106},
  doi = {https://doi.org/10.1302/2046-3758.82.BJR-2018-0134.R1}
}
Athanasiadis, M., Pak, A., Afanasenkau, D. and Minev, I.R. Direct Writing of Elastic Fibers with Optical, Electrical, and Microfluidic Functionality 2019 Advanced Materials Technologies
Vol. 0(0), pp. 1800659 
article DOI  
Abstract: Abstract Direct Ink Writing is an additive fabrication technology that allows the integration of a diverse range of functional materials into soft and bioinspired devices such as robots and human-machine interfaces. Typically, a viscoelastic ink is extruded from a nozzle as a continuous filament of circular cross section. Here it is shown that a careful selection of printing parameters such as nozzle height and speed can produce filaments with a range of cross-sectional geometries. Thus, elliptic cylinder-, ribbon-, or groove-shaped filaments can be printed. By using the nozzle as a stylus for postprint filament modification, even filaments with an embedded microfluidic channel can be produced. This strategy is applied to directly write freeform and elastic optical fibers, electrical interconnects, and microfluidics. The integration of these components into simple sensor-actuator systems is demonstrated. Prototypes of an optical fiber with steerable tip and a thermal actuation system for soft tissues are presented.
BibTeX:
@article{Athanasiadis2019,
  author = {Athanasiadis, Markos and Pak, Anna and Afanasenkau, Dzmitry and Minev, Ivan R.},
  title = {Direct Writing of Elastic Fibers with Optical, Electrical, and Microfluidic Functionality},
  journal = {Advanced Materials Technologies},
  year = {2019},
  volume = {0},
  number = {0},
  pages = {1800659},
  doi = {https://doi.org/10.1002/admt.201800659}
}
Sharma, A., Desando, G., Petretta, M., Chawla, S., Bartolotti, I., Manferdini, C., Paolella, F., Gabusi, E., Trucco, D., Ghosh, S. and Lisignoli, G. Investigating the Role of Sustained Calcium Release in Silk-Gelatin-Based Three-Dimensional Bioprinted Constructs for Enhancing the Osteogenic Differentiation of Human Bone Marrow Derived Mesenchymal Stromal Cells 2019 ACS Biomater. Sci. Eng.  article DOI  
BibTeX:
@article{Sharma2019,
  author = {Sharma, Aarushi and Desando, Giovanna and Petretta, Mauro and Chawla, Shikha and Bartolotti, Isabella and Manferdini, Cristina and Paolella, Francesca and Gabusi, Elena and Trucco, Diego and Ghosh, Sourabh and Lisignoli, Gina},
  title = {Investigating the Role of Sustained Calcium Release in Silk-Gelatin-Based Three-Dimensional Bioprinted Constructs for Enhancing the Osteogenic Differentiation of Human Bone Marrow Derived Mesenchymal Stromal Cells},
  journal = {ACS Biomater. Sci. Eng.},
  publisher = {American Chemical Society},
  year = {2019},
  doi = {https://doi.org/10.1021/acsbiomaterials.8b01631}
}
Pan, H.M., Chen, S., Jang, T.-S., Han, W.T., Jung, H.-d., Li, Y. and Song, J. Plant seed-inspired cell protection, dormancy, and growth for large-scale biofabrication 2019 Biofabrication
Vol. 11(2), pp. 025008 
article DOI  
Abstract: Biofabrication technologies have endowed us with the capability to fabricate complex biological constructs. However, cytotoxic biofabrication conditions have been a major challenge for their clinical application, leading to a trade-off between cell viability and scalability of biofabricated constructs. Taking inspiration from nature, we proposed a cell protection strategy which mimicks the protected and dormant state of plant seeds in adverse external conditions and their germination in response to appropriate environmental cues. Applying this bioinspired strategy to biofabrication, we successfully preserved cell viability and enhanced the seeding of cell-laden biofabricated constructs via a cytoprotective pyrogallol (PG)-alginate encapsulation system. Our cytoprotective encapsulation technology utilizes PG-triggered sporulation and germination processes to preserve cells, is mechanically robust, chemically resistant, and highly customizable to adequately match cell protectability with cytotoxicity of biofabrication conditions. More importantly, the facile and tunable decapsulation of our PG-alginate system allows for effective germination of dormant cells, under typical culture conditions. With this approach, we have successfully achieved a biofabrication process which is reproducible, scalable, and provided a practical solution for off-the-shelf availability, shipping and temporary storage of fabricated bio-constructs.
BibTeX:
@article{Pan2019,
  author = {Houwen Matthew Pan and Shengyang Chen and Tae-Sik Jang and Win Tun Han and Hyun-do Jung and Yaning Li and Juha Song},
  title = {Plant seed-inspired cell protection, dormancy, and growth for large-scale biofabrication},
  journal = {Biofabrication},
  publisher = {IOP Publishing},
  year = {2019},
  volume = {11},
  number = {2},
  pages = {025008},
  doi = {https://doi.org/10.1088/1758-5090/ab03ed}
}
Dooley, M., Prasopthum, A., Liao, Z., Sinjab, F., McLaren, J., Rose, F.R.A.J., Yang, J. and Notingher, I. Spatially-offset Raman spectroscopy for monitoring mineralization of bone tissue engineering scaffolds: feasibility study based on phantom samples 2019 Biomed. Opt. Express
Vol. 10(4), pp. 1678-1690 
article DOI URL 
Abstract: Using phantom samples, we investigated the feasibility of spatially-offset Raman spectroscopy (SORS) as a tool for monitoring non-invasively the mineralization of bone tissue engineering scaffold in-vivo. The phantom samples consisted of 3D-printed scaffolds of poly-caprolactone (PCL) and hydroxyapatite (HA) blends, with varying concentrations of HA, to mimic the mineralisation process. The scaffolds were covered by a 4 mm layer of skin to simulate the real in-vivo measurement conditions. At a concentration of HA approximately 1/3 that of bone ( 0.6 g/cm3), the characteristic Raman band of HA (960 cm&x2212;1) was detectable when the PCL:HA layer was located at 4 mm depth within the scaffold (i.e. 8 mm below the skin surface). For the layers of the PCL:HA immediately under the skin (i.e. top of the scaffold), the detection limit of HA was 0.18 g/cm3, which is approximately one order of magnitude lower than that of bone. Similar results were also found for the phantoms simulating uniform and inward gradual mineralisation of the scaffold, indicating the suitability of SORS to detect early stages of mineralisation. Nevertheless, the results also show that the contribution of the materials surrounding the scaffold can be significant and methods for subtraction need to be investigated in the future. In conclusion, these results indicate that spatially-offset Raman spectroscopy is a promising technique for in-vivo longitudinal monitoring scaffold mineralization and bone re-growth.
BibTeX:
@article{Dooley2019,
  author = {Max Dooley and Aruna Prasopthum and Zhiyu Liao and Faris Sinjab and Jane McLaren and Felicity R. A. J. Rose and Jing Yang and Ioan Notingher},
  title = {Spatially-offset Raman spectroscopy for monitoring mineralization of bone tissue engineering scaffolds: feasibility study based on phantom samples},
  journal = {Biomed. Opt. Express},
  publisher = {OSA},
  year = {2019},
  volume = {10},
  number = {4},
  pages = {1678--1690},
  url = {http://www.osapublishing.org/boe/abstract.cfm?URI=boe-10-4-1678},
  doi = {https://doi.org/10.1364/BOE.10.001678}
}
Zhang, D., Peng, E., Borayek, R. and Ding, J. Controllable Ceramic Green-Body Configuration for Complex Ceramic Architectures with Fine Features 2019 Advanced Functional Materials
Vol. 0(0), pp. 1807082 
article DOI  
Abstract: Abstract Fabrication of dense ceramic articles with intricate fine features and geometrically complex morphology by using a relatively simple and the cost-effective process still remains a challenge. Ceramics, either in its green- or sintered-form, are known for being hard yet brittle which limits further shape reconfiguration. In this work, a combinatorial process of ceramic robocasting and photopolymerization is demonstrated to produce either flexible and/or stretchable ceramic green-body (Flex-Body or Stretch-Body) that can undergo a postprinting reconfiguration process. Secondary shaping may proceed through: i) self-assembly-assisted shaping and ii) mold-assisted shaping process, which allows a well-controlled ceramic structure morphology. With a proposed well-controlled thermal heating process, the ceramic Sintered-Body can achieve >99.0% theoretical density with good mechanical rigidity. Complex and dense ceramic articles with fine features down to 65 μm can be fabricated. When combined with a multi-nozzle deposition process, i) self-shaping ceramic structures can be realized through anisotropic shrinkage induced by suspensions' composition variation and ii) technical and functional multiceramic structures can be fabricated. The simplicity of the proposed technique and its inexpensive processing cost make it an attractive approach for fabricating geometrically complex ceramic articles with unique macrostructures, which complements the existing state of-the-art ceramic additive manufacturing techniques.
BibTeX:
@article{Zhang2019,
  author = {Zhang, Danwei and Peng, Erwin and Borayek, Ramadan and Ding, Jun},
  title = {Controllable Ceramic Green-Body Configuration for Complex Ceramic Architectures with Fine Features},
  journal = {Advanced Functional Materials},
  year = {2019},
  volume = {0},
  number = {0},
  pages = {1807082},
  doi = {https://doi.org/10.1002/adfm.201807082}
}
Rathan, S., Dejob, L., Schipani, R., Haffner, B., Möbius, M.E. and Kelly, D.J. Fiber Reinforced Cartilage ECM Functionalized Bioinks for Functional Cartilage Tissue Engineering 2019 Advanced Healthcare Materials
Vol. 0(0), pp. 1801501 
article DOI  
Abstract: Abstract Focal articular cartilage (AC) defects, if left untreated, can lead to debilitating diseases such as osteoarthritis. While several tissue engineering strategies have been developed to promote cartilage regeneration, it is still challenging to generate functional AC capable of sustaining high load-bearing environments. Here, a new class of cartilage extracellular matrix (cECM)-functionalized alginate bioink is developed for the bioprinting of cartilaginous tissues. The bioinks are 3D-printable, support mesenchymal stem cell (MSC) viability postprinting and robust chondrogenesis in vitro, with the highest levels of COLLII and ACAN expression observed in bioinks containing the highest concentration of cECM. Enhanced chondrogenesis in cECM-functionalized bioinks is also associated with progression along an endochondral-like pathway, as evident by increases in RUNX2 expression and calcium deposition in vitro. The bioinks loaded with MSCs and TGF-β3 are also found capable of supporting robust chondrogenesis, opening the possibility of using such bioinks for direct “print-and-implant” cartilage repair strategies. Finally, it is demonstrated that networks of 3D-printed polycaprolactone fibers with compressive modulus comparable to native AC can be used to mechanically reinforce these bioinks, with no loss in cell viability. It is envisioned that combinations of such biomaterials can be used in multiple-tool biofabrication strategies for the bioprinting of biomimetic cartilaginous implants.
BibTeX:
@article{Rathan2019,
  author = {Rathan, Swetha and Dejob, Léa and Schipani, Rossana and Haffner, Benjamin and Möbius, Matthias E. and Kelly, Daniel J.},
  title = {Fiber Reinforced Cartilage ECM Functionalized Bioinks for Functional Cartilage Tissue Engineering},
  journal = {Advanced Healthcare Materials},
  year = {2019},
  volume = {0},
  number = {0},
  pages = {1801501},
  doi = {https://doi.org/10.1002/adhm.201801501}
}
Alison, L., Menasce, S., Bouville, F., Tervoort, E., Mattich, I., Ofner, A. and Studart, A.R. 3D printing of sacrificial templates into hierarchical porous materials 2019 Scientific Reports
Vol. 9(1), pp. 409 
article DOI  
Abstract: Hierarchical porous materials are widespread in nature and find an increasing number of applications as catalytic supports, biological scaffolds and lightweight structures. Recent advances in additive manufacturing and 3D printing technologies have enabled the digital fabrication of porous materials in the form of lattices, cellular structures and foams across multiple length scales. However, current approaches do not allow for the fast manufacturing of bulk porous materials featuring pore sizes that span broadly from macroscopic dimensions down to the nanoscale. Here, ink formulations are designed and investigated to enable 3D printing of hierarchical materials displaying porosity at the nano-, micro- and macroscales. Pores are generated upon removal of nanodroplets and microscale templates present in the initial ink. Using particles to stabilize the droplet templates is key to obtain Pickering nanoemulsions that can be 3D printed through direct ink writing. The combination of such self-assembled templates with the spatial control offered by the printing process allows for the digital manufacturing of hierarchical materials exhibiting thus far inaccessible multiscale porosity and complex geometries.
BibTeX:
@article{Alison2019,
  author = {Alison, Lauriane and Menasce, Stefano and Bouville, Florian and Tervoort, Elena and Mattich, Iacopo and Ofner, Alessandro and Studart, André R.},
  title = {3D printing of sacrificial templates into hierarchical porous materials},
  journal = {Scientific Reports},
  year = {2019},
  volume = {9},
  number = {1},
  pages = {409},
  doi = {https://doi.org/10.1038/s41598-018-36789-z}
}
Yilmaz, B, Tahmasebifar, A and Baran, ET Bioprinting Technologies in Tissue Engineering 2019 Adv Biochem Eng Biotechnol  article DOI  
BibTeX:
@article{Yilmaz2019,
  author = {Yilmaz B, Tahmasebifar A, Baran ET},
  title = {Bioprinting Technologies in Tissue Engineering},
  journal = {Adv Biochem Eng Biotechnol},
  year = {2019},
  doi = {https://doi.org/10.1007/10_2019_108}
}
Xu, Y., Peng, J., Richards, G., Lu, S. and Eglin, D. Optimization of electrospray fabrication of stem cell–embedded alginate–gelatin microspheres and their assembly in 3D-printed poly(ε-caprolactone) scaffold for cartilage tissue engineering 2019 Journal of Orthopaedic Translation
Vol. 18, pp. 128 - 141 
article DOI URL 
Abstract: Objective
Our study reports the optimization of electrospray human bone marrow stromal cell (hBMSCs)–embedded alginate–gelatin (Alg-Gel, same as following) microspheres for the purpose of their assembly in 3D-printed poly(ε-caprolactone) (PCL) scaffold for the fabrication of a mechanically stable and biological supportive tissue engineering cartilage construct.
Methods
The fabrication of the Alg-Gel microspheres using an electrospray technique was optimized in terms of polydispersity, yield of microspheres and circularity and varying fabrication conditions. PCL scaffolds were designed and printed by melt extrusion. Then, four groups were set: Alg-hBMSC microspheres cultured in the 2D well plate (Alg-hBMSCs+2D) group, Alg-Gel-hBMSC microspheres cultured in the 2D well plate (Alg-Gel-hBMSCs+2D) group, Alg-Gel-hBMSC microspheres embedded in PCL scaffold cultured in the 2D well plate (Alg-Gel-hBMSCs+2D) group and Alg-Gel-hBMSCs microspheres cultured in the 3D bioreactor (Alg-Gel-hBMSCs+3D) group. Cell viability, proliferation and chondrogenic differentiation were evaluated, and mechanical test was performed.
Results
Nonaggregated, low polydispersity and almost spherical microspheres of average diameter of 200–300 μm were produced with alginate 1.5 w: v%, gelatin (Type B) concentration of 0.5 w: v % and CaCl2 coagulating bath concentration of 3.0 w: v %, using 30G needle size and 8 kV and 0.6 bar voltage and air pressure, respectively. Alginate with gelatin hydrogel improved viability and promoted hBMSC proliferation better than alginate microspheres. Interestingly, hBMSCs embedded in microspheres assembled in 3D-printed PCL scaffold and cultured in a 3D bioreactor were more proliferative in comparison to the previous two groups (p < 0.05). Similarly, the GAG content, GAG/DNA ratio as well as Coll 2 and Aggr gene expression were increased in the last two groups.
Conclusion
Optimization of hBMSC-embedded Alg-Gel microspheres produced by electrospray has been performed. The Alg-Gel composition selected allows conservation of hBMSC viability and supports proliferation and matrix deposition. The possibility to seed and assemble microspheres in designed 3D-printed PCL scaffolds for the fabrication of a mechanically stable and biological supportive tissue engineering cartilage construct was demonstrated.
Translational potential of this article
We optimize and demonstrate that electrospray microsphere fabrication is a cytocompatible and facile process to produce the hBMSC-embedded microsize tissue-like particles that can easily be assembled into a stable construct. This finding could have application in the development of mechanically competent stem cell–based tissue engineering of cartilage regeneration.
BibTeX:
@article{Xu2019,
  author = {Yichi Xu and Jiang Peng and Geoff Richards and Shibi Lu and David Eglin},
  title = {Optimization of electrospray fabrication of stem cell–embedded alginate–gelatin microspheres and their assembly in 3D-printed poly(ε-caprolactone) scaffold for cartilage tissue engineering},
  journal = {Journal of Orthopaedic Translation},
  year = {2019},
  volume = {18},
  pages = {128 - 141},
  url = {http://www.sciencedirect.com/science/article/pii/S2214031X19300518},
  doi = {https://doi.org/10.1016/j.jot.2019.05.003}
}
Wang, W., Junior, J.R.P., Nalesso, P.R.L., Musson, D., Cornish, J., Mendonça, F., Caetano, G.F. and Bártolo, P. Engineered 3D printed poly(ɛ-caprolactone)/graphene scaffolds for bone tissue engineering 2019 Materials Science and Engineering: C
Vol. 100, pp. 759 - 770 
article DOI URL 
Abstract: Scaffolds are important physical substrates for cell attachment, proliferation and differentiation. Multiple factors could influence the optimal design of scaffolds for a specific tissue, such as the geometry, the materials used to modulate cell proliferation and differentiation, its biodegradability and biocompatibility. The optimal design of a scaffold for a specific tissue strongly depends on both materials and manufacturing processes. Previous studies of human adipose-derived stem cells (hADSCs) seeded on poly(ε-caprolactone) (PCL)/graphene scaffolds have proved that the addition of small concentrations of graphene to PCL scaffolds improves cell proliferation. Based on such results, this paper further investigates, for the first time, both in vitro and in vivo characteristics of 3D printed PCL/graphene scaffolds. Scaffolds were evaluated from morphological, biological and short term immune response points of view. Results show that the produced scaffolds induce an acceptable level of immune response, suggesting high potential for in vivo applications. Finally, the scaffolds were used to treat a rat calvaria critical size defect with and without applying micro electrical stimulation (10 μA). Quantification of connective and new bone tissue formation and the levels of ALP, RANK, RANKL, OPG were considered. Results show that the use of scaffolds containing graphene and electrical stimulation seems to increase cell migration and cell influx, leading to new tissue formation, well-organized tissue deposition and bone remodelling.
BibTeX:
@article{Wang2019a,
  author = {Weiguang Wang and José Roberto Passarini Junior and Paulo Roberto Lopes Nalesso and David Musson and Jillian Cornish and Fernanda Mendonça and Guilherme Ferreira Caetano and Paulo Bártolo},
  title = {Engineered 3D printed poly(ɛ-caprolactone)/graphene scaffolds for bone tissue engineering},
  journal = {Materials Science and Engineering: C},
  year = {2019},
  volume = {100},
  pages = {759 - 770},
  url = {http://www.sciencedirect.com/science/article/pii/S092849311930308X},
  doi = {https://doi.org/10.1016/j.msec.2019.03.047}
}
Wang, W., Huang, B., Byun, J.J. and Bártolo, P. Assessment of PCL/carbon material scaffolds for bone regeneration 2019 Journal of the Mechanical Behavior of Biomedical Materials
Vol. 93, pp. 52 - 60 
article DOI URL 
Abstract: Biomanufacturing is a relatively new research domain focusing on the use of additive manufacturing technologies, biomaterials, cells and biomolecular signals to produce tissue constructs for tissue engineering. For bone regeneration, researchers are focusing on the use of polymeric and polymer/ceramic scaffolds seeded with osteoblasts or mesenchymal stem cells. However, the design of high-performance scaffolds in terms of mechanical, cell-stimulation and biological performance is still required. This is the first paper investigating the use of an extrusion additive manufacturing system to produce poly(ε-caprolactone) (PCL), PCL/graphene nanosheet (GNS) and PCL/carbon nanotube (CNT) scaffolds for bone applications. Scaffolds with regular and reproducible architecture were produced and evaluated from chemical, physical and biological points of view. Results suggest that the addition of both graphene and CNT allow the fabrication of scaffolds with improved properties. It also shows that scaffolds containing graphene present better mechanical properties and high cell-affinity improving cell attachment, proliferation and differentiation.
BibTeX:
@article{Wang2019,
  author = {Weiguang Wang and Boyang Huang and Jae Jong Byun and Paulo Bártolo},
  title = {Assessment of PCL/carbon material scaffolds for bone regeneration},
  journal = {Journal of the Mechanical Behavior of Biomedical Materials},
  year = {2019},
  volume = {93},
  pages = {52 - 60},
  url = {http://www.sciencedirect.com/science/article/pii/S1751616118314759},
  doi = {https://doi.org/10.1016/j.jmbbm.2019.01.020}
}
Valot, L., Martinez, J., Mehdi, A. and Subra, G. Chemical insights into bioinks for 3D printing 2019 Chem. Soc. Rev.
Vol. 48, pp. 4049-4086 
article DOI  
Abstract: 3D printing has triggered the acceleration of numerous research areas in health sciences, which traditionally used cells as starting materials, in particular tissue engineering, regenerative medicine and also in the design of more relevant bioassays for drug discovery and development. While cells can be successfully printed in 2D layers without the help of any supporting biomaterial, the obtainment of more complex 3D architectures requires a specific bioink, i.e. a material in which the cells are embedded during and after the printing process helping to support them while they are arranged in superimposed layers. The bioink plays a critical role in bioprinting: first, it must be adapted to the 3D printing technology; then, it must fulfil the physicochemical and mechanical characteristics of the target construct (e.g. stiffness, elasticity, robustness, transparency); finally it should guarantee cell viability and eventually induce a desired behaviour. This review focuses on the nature of bioink components of natural or synthetic origin, and highlights the chemistry required for the establishment of the 3D network in conditions compatible with the selected 3D printing technique and cell survival.
BibTeX:
@article{Valot2019,
  author = {Valot, Laurine and Martinez, Jean and Mehdi, Ahmad and Subra, Gilles},
  title = {Chemical insights into bioinks for 3D printing},
  journal = {Chem. Soc. Rev.},
  publisher = {The Royal Society of Chemistry},
  year = {2019},
  volume = {48},
  pages = {4049-4086},
  doi = {https://doi.org/10.1039/C7CS00718C}
}
Tondera, C., Akbar, T.F., Thomas, A.K., Lin, W., Werner, C., Busskamp, V., Zhang, Y. and Minev, I.R. Highly Conductive, Stretchable, and Cell-Adhesive Hydrogel by Nanoclay Doping 2019 Small
Vol. 0(0), pp. 1901406 
article DOI  
Abstract: Abstract Electrically conductive materials that mimic physical and biological properties of tissues are urgently required for seamless brain–machine interfaces. Here, a multinetwork hydrogel combining electrical conductivity of 26 S m−1, stretchability of 800 and tissue-like elastic modulus of 15 kPa with mimicry of the extracellular matrix is reported. Engineering this unique set of properties is enabled by a novel in-scaffold polymerization approach. Colloidal hydrogels of the nanoclay Laponite are employed as supports for the assembly of secondary polymer networks. Laponite dramatically increases the conductivity of in-scaffold polymerized poly(ethylene-3,4-diethoxy thiophene) in the absence of other dopants, while preserving excellent stretchability. The scaffold is coated with a layer containing adhesive peptide and polysaccharide dextran sulfate supporting the attachment, proliferation, and neuronal differentiation of human induced pluripotent stem cells directly on the surface of conductive hydrogels. Due to its compatibility with simple extrusion printing, this material promises to enable tissue-mimetic neurostimulating electrodes.
BibTeX:
@article{Tondera2019,
  author = {Tondera, Christoph and Akbar, Teuku Fawzul and Thomas, Alvin Kuriakose and Lin, Weilin and Werner, Carsten and Busskamp, Volker and Zhang, Yixin and Minev, Ivan R.},
  title = {Highly Conductive, Stretchable, and Cell-Adhesive Hydrogel by Nanoclay Doping},
  journal = {Small},
  year = {2019},
  volume = {0},
  number = {0},
  pages = {1901406},
  doi = {https://doi.org/10.1002/smll.201901406}
}
Shen, J., Wang, W., Zhai, X., Chen, B., Qiao, W., Li, W., Li, P., Zhao, Y., Meng, Y., Qian, S., Liu, X., Chu, P.K. and Yeung, K.W. 3D-printed nanocomposite scaffolds with tunable magnesium ionic microenvironment induce in situ bone tissue regeneration 2019 Applied Materials Today
Vol. 16, pp. 493 - 507 
article DOI URL 
Abstract: Local tissue microenvironment is able to regulate cell-to-cell interaction that leads to effective tissue repair. This study aims to demonstrate a tunable magnesium ionic (Mg2+) microenvironment in bony tissue that can significantly induce bone defect repair. The concept can be realized by using a newly fabricated nanocomposite comprising of custom-made copolymer polycaprolactone-co-poly(ethylene glycol)-co-polycaprolactone (PCL-PEG-PCL) and surface-modified magnesium oxide (MgO) nanoparticles. In this study, additive manufacturing (AM) technology had been adopted to help design the porous three-dimensional (3D) scaffolds with tunable Mg2+ microenvironment. We found that the wettability and printability of new copolymer had been improved as compared with that of PCL polymer. Additionally, when MgO nanoparticles incorporated into the newly synthesized hydrophilic copolymer matrix, it could lead to increased compressive moduli significantly. In the in vitro studies, the fabricated nanocomposite scaffold with low concentration of Mg2+ microenvironment not only demonstrated better cytocompatibility, but also remarkably enhanced osteogenic differentiation in vitro as compared with the pure PCL and PCL-PEG-PCL co-polymer controls. In the animal studies, we also found that superior and early bone formation and tissue mineralization could be observed in the same 3D printed scaffold. However, the nanocomposite scaffold with high concentration of Mg2+ jeopardized the in situ bony tissue regeneration capability due to excessive magnesium ions in bone tissue microenvironment. Lastly, this study demonstrates that the nanocomposite 3D scaffold with controlled magnesium concentration in bone tissue microenvironment can effectively promote bone defect repair.
BibTeX:
@article{Shen2019,
  author = {Jie Shen and Wenhao Wang and Xinyun Zhai and Bo Chen and Wei Qiao and Wan Li and Penghui Li and Ying Zhao and Yuan Meng and Shi Qian and Xuanyong Liu and Paul K. Chu and Kelvin W.K. Yeung},
  title = {3D-printed nanocomposite scaffolds with tunable magnesium ionic microenvironment induce in situ bone tissue regeneration},
  journal = {Applied Materials Today},
  year = {2019},
  volume = {16},
  pages = {493 - 507},
  url = {http://www.sciencedirect.com/science/article/pii/S2352940719305542},
  doi = {https://doi.org/10.1016/j.apmt.2019.07.012}
}
Schipani, R., Nolan, D.R., Lally, C. and Kelly, D.J. Integrating finite element modelling and 3D printing to engineer biomimetic polymeric scaffolds for tissue engineering 2019 Connective Tissue Research
Vol. 0(0), pp. 1-16 
article DOI  
Abstract: ABSTRACTThe suitability of a scaffold for tissue engineering is determined by a number of interrelated factors. The biomaterial should be biocompatible and cell instructive, with a porosity and pore interconnectivity that facilitates cellular migration and the transport of nutrients and waste products into and out of the scaffolds. For the engineering of load bearing tissues, the scaffold may also be required to possess specific mechanical properties and/or ensure the transfer of mechanical stimuli to cells to direct their differentiation. Achieving these design goals is challenging, but could potentially be realised by integrating computational tools such as finite element (FE) modelling with three-dimensional (3D) printing techniques to assess how scaffold architecture and material properties influence the performance of the implant. In this study we first use Fused Deposition Modelling (FDM) to modulate the architecture of polycaprolactone (PCL) scaffolds, exploring the influence of varying fibre diameter, spacing and laydown pattern on the structural and mechanical properties of such scaffolds. We next demonstrate that a simple FE modelling strategy, which captures key aspects of the printed scaffold’s actual geometry and material behaviour, can be used to accurately model the mechanical characteristics of such scaffolds. We then show the utility of this strategy by using FE modelling to help design 3D printed scaffolds with mechanical properties mimicking that of articular cartilage. In conclusion, this study demonstrates that a relatively simple FE modelling approach can be used to inform the design of 3D printed scaffolds to ensure their bulk mechanical properties mimic specific target tissues.
BibTeX:
@article{Schipani2019,
  author = {Rossana Schipani and David R. Nolan and Caitrίona Lally and Daniel J. Kelly},
  title = {Integrating finite element modelling and 3D printing to engineer biomimetic polymeric scaffolds for tissue engineering},
  journal = {Connective Tissue Research},
  publisher = {Taylor & Francis},
  year = {2019},
  volume = {0},
  number = {0},
  pages = {1-16},
  note = {PMID: 31495233},
  doi = {https://doi.org/10.1080/03008207.2019.1656720}
}
Roopavath, U.K., Soni, R., Mahanta, U., Deshpande, A.S. and Rath, S.N. 3D printable SiO2 nanoparticle ink for patient specific bone regeneration 2019 RSC Adv.
Vol. 9, pp. 23832-23842 
article DOI  
Abstract: Sodium alginate and gelatin are biocompatible & biodegradable natural polymer hydrogels, which are widely investigated for application in tissue engineering using 3D printing and 3D bioprinting fabrication techniques. The major challenge of using hydrogels for tissue fabrication is their lack of regeneration ability, uncontrolled swelling, degradation and inability to hold 3D structure on their own. Free hydroxyl groups on the surface of SiO2 nanoparticles have the ability to chemically interact with alginate–gelatin polymer network, which can be explored to achieve the above parameters. Hence validating the incorporation of SiO2 nanoparticles in a 3D printable hydrogel polymer network, according to the patient's critical defects has immense scope in bone tissue engineering. In this study, SiO2 nanoparticles are loaded into alginate–gelatin composite hydrogels and chemically crosslinked with CaCl2 solution. The effect of SiO2 nanoparticles on the viscosity, swelling, degradation, compressive modulus (MPa), biocompatibility and osteogenic ability were evaluated on lyophilized scaffolds and found to be desirable for bone tissue engineering. A complex irregular patient-specific virtual defect was created and the 3D printing process to fabricate such structures was evaluated. The 3D printing of SiO2 nanoparticle hydrogel composite ink to fabricate a bone graft using a patient-specific virtual defect was successfully validated. Hence this type of hydrogel composite ink has huge potential and scope for its application in tissue engineering and nanomedicine.
BibTeX:
@article{Roopavath2019,
  author = {Roopavath, Uday Kiran and Soni, Raghav and Mahanta, Urbashi and Deshpande, Atul Suresh and Rath, Subha Narayan},
  title = {3D printable SiO2 nanoparticle ink for patient specific bone regeneration},
  journal = {RSC Adv.},
  publisher = {The Royal Society of Chemistry},
  year = {2019},
  volume = {9},
  pages = {23832-23842},
  doi = {https://doi.org/10.1039/C9RA03641E}
}
Romanazzo, S., Nemec, S. and Roohani, I. iPSC Bioprinting: Where are We at? 2019 Materials
Vol. 12(15) 
article DOI URL 
Abstract: Here, we present a concise review of current 3D bioprinting technologies applied to induced pluripotent stem cells (iPSC). iPSC have recently received a great deal of attention from the scientific and clinical communities for their unique properties, which include abundant adult cell sources, ability to indefinitely self-renew and differentiate into any tissue of the body. Bioprinting of iPSC and iPSC derived cells combined with natural or synthetic biomaterials to fabricate tissue mimicked constructs, has emerged as a technology that might revolutionize regenerative medicine and patient-specific treatment. This review covers the advantages and disadvantages of bioprinting techniques, influence of bioprinting parameters and printing condition on cell viability, and commonly used iPSC sources, and bioinks. A clear distinction is made for bioprinting techniques used for iPSC at their undifferentiated stage or when used as adult stem cells or terminally differentiated cells. This review presents state of the art data obtained from major searching engines, including Pubmed/MEDLINE, Google Scholar, and Scopus, concerning iPSC generation, undifferentiated iPSC, iPSC bioprinting, bioprinting techniques, cartilage, bone, heart, neural tissue, skin, and hepatic tissue cells derived from iPSC.
BibTeX:
@article{Romanazzo2019,
  author = {Romanazzo, Sara and Nemec, Stephanie and Roohani, Iman},
  title = {iPSC Bioprinting: Where are We at?},
  journal = {Materials},
  year = {2019},
  volume = {12},
  number = {15},
  url = {https://www.mdpi.com/1996-1944/12/15/2453},
  doi = {https://doi.org/10.3390/ma12152453}
}
Prendergast, M.E. and Burdick, J.A. Recent Advances in Enabling Technologies in 3D Printing for Precision Medicine 2019 Advanced Materials
Vol. 0(0), pp. 1902516 
article DOI  
Abstract: Abstract Advances in areas such as data analytics, genomics, and imaging have revealed individual patient complexities and exposed the inherent limitations of generic therapies for patient treatment. These observations have also fueled the development of precision medicine approaches, where therapies are tailored for the individual rather than the broad patient population. 3D printing is a field that intersects with precision medicine through the design of precision implants with patient-directed shapes, structures, and materials or for the development of patient-specific in vitro models that can be used for screening precision therapeutics. Toward their success, advances in 3D printing and biofabrication technologies are needed with enhanced resolution, complexity, reproducibility, and speed and that encompass a broad range of cells and materials. The overall goal of this progress report is to highlight recent advances in 3D printing technologies that are helping to enable advances important in precision medicine.
BibTeX:
@article{Prendergast2019,
  author = {Prendergast, Margaret E. and Burdick, Jason A.},
  title = {Recent Advances in Enabling Technologies in 3D Printing for Precision Medicine},
  journal = {Advanced Materials},
  year = {2019},
  volume = {0},
  number = {0},
  pages = {1902516},
  doi = {https://doi.org/10.1002/adma.201902516}
}
Mestre, R., Patiño, T., Barceló, X., Anand, S., Pérez-Jiménez, A. and Sánchez, S. Force Modulation and Adaptability of 3D-Bioprinted Biological Actuators Based on Skeletal Muscle Tissue 2019 Advanced Materials Technologies
Vol. 4(2), pp. 1800631 
article DOI  
Abstract: Abstract The integration of biological systems into robotic devices might provide them with capabilities acquired from natural systems and significantly boost their performance. These abilities include real-time bio-sensing, self-organization, adaptability, or self-healing. As many muscle-based bio-hybrid robots and bio-actuators arise in the literature, the question of whether these features can live up to their expectations becomes increasingly substantial. Herein, the force generation and adaptability of skeletal-muscle-based bio-actuators undergoing long-term training protocols are analyzed. The 3D-bioprinting technique is used to fabricate bio-actuators that are functional, responsive, and have highly aligned myotubes. The bio-actuators are 3D-bioprinted together with two artificial posts, allowing to use it as a force measuring platform. In addition, the force output evolution and dynamic gene expression of the bio-actuators are studied to evaluate their degree of adaptability according to training protocols of different frequencies and mechanical stiffness, finding that their force generation could be modulated to different requirements. These results shed some light into the fundamental mechanisms behind the adaptability of muscle-based bio-actuators and highlight the potential of using 3D bioprinting as a rapid and cost-effective tool for the fabrication of custom-designed soft bio-robots.
BibTeX:
@article{Mestre2019,
  author = {Mestre, Rafael and Patiño, Tania and Barceló, Xavier and Anand, Shivesh and Pérez-Jiménez, Ariadna and Sánchez, Samuel},
  title = {Force Modulation and Adaptability of 3D-Bioprinted Biological Actuators Based on Skeletal Muscle Tissue},
  journal = {Advanced Materials Technologies},
  year = {2019},
  volume = {4},
  number = {2},
  pages = {1800631},
  doi = {https://doi.org/10.1002/admt.201800631}
}
Marchiori, G., Berni, M., Boi, M., Petretta, M., Grigolo, B., Bellucci, D., Cannillo, V., Garavelli, C. and Bianchi, M. Design of a novel procedure for the optimization of the mechanical performances of 3D printed scaffolds for bone tissue engineering combining CAD, Taguchi method and FEA 2019 Medical Engineering & Physics
Vol. 69, pp. 92 - 99 
article DOI URL 
Abstract: In order to increase manufacturing and experimental efficiency, a certain degree of control over design performances before realization phase is recommended. In this context, this paper presents an integrated procedure to design 3D scaffolds for bone tissue engineering. The procedure required a combination of Computer Aided Design (CAD), Finite Element Analysis (FEA), and Design methodologies Of Experiments (DOE), firstly to understand the influence of the design parameters, and then to control them. Based on inputs from the literature and limitations imposed by the chosen manufacturing process (Precision Extrusion Deposition), 36 scaffold architectures have been drawn. The porosity of each scaffold has been calculated with CAD. Thereafter, a generic scaffold material was considered and its variable parameters were combined with the geometrical ones according to the Taguchi method, i.e. a DOE method. The compressive response of those principal combinations was simulated by FEA, and the influence of each design parameter on the scaffold compressive behaviour was clarified. Finally, a regression model was obtained correlating the scaffold's mechanical performances to its geometrical and material parameters. This model has been applied to a novel composite material made of polycaprolactone and innovative bioactive glass. By setting specific porosity (50%) and stiffness (0.05 GPa) suitable for trabecular bone substitutes, the model selected 4 of the 36 initial scaffold architectures. Only these 4 more promising geometries will be realized and physically tested for advanced indications on compressive strength and biocompatibility.
BibTeX:
@article{Marchiori2019,
  author = {Gregorio Marchiori and Matteo Berni and Marco Boi and Mauro Petretta and Brunella Grigolo and Devis Bellucci and Valeria Cannillo and Chiara Garavelli and Michele Bianchi},
  title = {Design of a novel procedure for the optimization of the mechanical performances of 3D printed scaffolds for bone tissue engineering combining CAD, Taguchi method and FEA},
  journal = {Medical Engineering & Physics},
  year = {2019},
  volume = {69},
  pages = {92 - 99},
  url = {http://www.sciencedirect.com/science/article/pii/S1350453319300773},
  doi = {https://doi.org/10.1016/j.medengphy.2019.04.009}
}
Li, J., Liu, X., Crook, J. and Wallace, G. 3D graphene-containing structures for tissue engineering 2019 Materials Today Chemistry
Vol. 14, pp. 100199 
article DOI URL 
Abstract: Graphene and its derivatives have been extensively explored in various fields and have shown great promise toward energy harvesting, environmental protection, and health care. 3D graphene-containing structures (3DGCSs) are especially endowed with useable features relating to physicochemical properties within the hierarchical architectures. Thus, 3DGCSs are increasingly being applied for tissue engineering because of their supportability of human cells and functionalization potential. This review focuses on recent progress in tissue engineering utilizing 3DGCSs, providing insights into fabrication, application, and constraints in bionic research.
BibTeX:
@article{Li2019,
  author = {J. Li and X. Liu and J.M. Crook and G.G. Wallace},
  title = {3D graphene-containing structures for tissue engineering},
  journal = {Materials Today Chemistry},
  year = {2019},
  volume = {14},
  pages = {100199},
  url = {http://www.sciencedirect.com/science/article/pii/S2468519419302113},
  doi = {https://doi.org/10.1016/j.mtchem.2019.100199}
}
Kleger, N., Cihova, M., Masania, K., Studart, A.R. and Löffler, J.F. 3d printing of salt as a template for magnesium with structured porosity 2019 advanced materials
Vol. 0(0), pp. 1903783 
article DOI  
Abstract: Abstract Porosity is an essential feature in a wide range of applications that combine light weight with high surface area and tunable density. Porous materials can be easily prepared with a vast variety of chemistries using the salt-leaching technique. However, this templating approach has so far been limited to the fabrication of structures with random porosity and relatively simple macroscopic shapes. Here, a technique is reported that combines the ease of salt leaching with the complex shaping possibilities given by additive manufacturing (AM). By tuning the composition of surfactant and solvent, the salt-based paste is rheologically engineered and printed via direct ink writing into grid-like structures displaying structured pores that span from the sub-millimeter to the macroscopic scale. As a proof of concept, dried and sintered NaCl templates are infiltrated with magnesium (Mg), which is typically highly challenging to process by conventional AM techniques due to its highly oxidative nature and high vapor pressure. Mg scaffolds with well-controlled, ordered porosity are obtained after salt removal. The tunable mechanical properties and the potential to be predictably bioresorbed by the human body make these Mg scaffolds attractive for biomedical implants and demonstrate the great potential of this additive technique.
BibTeX:
@article{Kleger2019,
  author = {Kleger, Nicole and Cihova, Martina and Masania, Kunal and Studart, André R. and Löffler, Jörg F.},
  title = {3d printing of salt as a template for magnesium with structured porosity},
  journal = {advanced materials},
  year = {2019},
  volume = {0},
  number = {0},
  pages = {1903783},
  doi = {https://doi.org/10.1002/adma.201903783}
}
Kjar, A. and Huang, Y. Application of Micro-Scale 3D Printing in Pharmaceutics 2019 Pharmaceutics
Vol. 11(8) 
article DOI URL 
Abstract: 3D printing, as one of the most rapidly-evolving fabrication technologies, has released a cascade of innovation in the last two decades. In the pharmaceutical field, the integration of 3D printing technology has offered unique advantages, especially at the micro-scale. When printed at a micro-scale, materials and devices can provide nuanced solutions to controlled release, minimally invasive delivery, high-precision targeting, biomimetic models for drug discovery and development, and future opportunities for personalized medicine. This review aims to cover the recent advances in this area. First, the 3D printing techniques are introduced with respect to the technical parameters and features that are uniquely related to each stage of pharmaceutical development. Then specific micro-sized pharmaceutical applications of 3D printing are summarized and grouped according to the provided benefits. Both advantages and challenges are discussed for each application. We believe that these technologies provide compelling future solutions for modern medicine, while challenges remain for scale-up and regulatory approval.
BibTeX:
@article{Kjar2019,
  author = {Kjar, Andrew and Huang, Yu},
  title = {Application of Micro-Scale 3D Printing in Pharmaceutics},
  journal = {Pharmaceutics},
  year = {2019},
  volume = {11},
  number = {8},
  url = {https://www.mdpi.com/1999-4923/11/8/390},
  doi = {https://doi.org/10.3390/pharmaceutics11080390}
}
Fenton, O.S., Paolini, M., Andresen, J.L., Müller, F.J. and Langer, R. Outlooks on Three-Dimensional Printing for Ocular Biomaterials Research 2019 Journal of Ocular Pharmacology and Therapeutics
Vol. 0(0), pp. null 
article DOI  
Abstract: Abstract Given its potential for high-resolution, customizable, and waste-free fabrication of medical devices and in vitro biological models, 3-dimensional (3D) bioprinting has broad utility within the biomaterials field. Indeed, 3D bioprinting has to date been successfully used for the development of drug delivery systems, the recapitulation of hard biological tissues, and the fabrication of cellularized organ and tissue-mimics, among other applications. In this study, we highlight convergent efforts within engineering, cell biology, soft matter, and chemistry in an overview of the 3D bioprinting field, and we then conclude our work with outlooks toward the application of 3D bioprinting for ocular research in vitro and in vivo.
BibTeX:
@article{Fenton2019,
  author = {Fenton, Owen S. and Paolini, Marion and Andresen, Jason L. and Müller, Florence J. and Langer, Robert},
  title = {Outlooks on Three-Dimensional Printing for Ocular Biomaterials Research},
  journal = {Journal of Ocular Pharmacology and Therapeutics},
  year = {2019},
  volume = {0},
  number = {0},
  pages = {null},
  note = {PMID: 31211652},
  doi = {https://doi.org/10.1089/jop.2018.0142}
}
Derr, K., Zou, J., Luo, K., Song, M.J., Sittampalam, G.S., Zhou, C., Michael, S., Ferrer, M. and Derr, P. Fully 3D Bioprinted Skin Equivalent Constructs with Validated Morphology and Barrier Function 2019 Tissue Engineering Part C: Methods
Vol. 0(ja), pp. null 
article DOI  
Abstract: Development of high throughput, reproducible, three-dimensional bioprinted skin equivalents that are morphologically and functionally comparable to native skin tissue is advancing research in skin diseases, and providing a physiologically relevant platform for the development of therapeutics, transplants for regenerative medicine, and testing of skin products like cosmetics. Current protocols for the production of engineered skin rafts are limited in their ability to control three dimensional geometry of the structure and contraction leading to variability of skin function between constructs. Here we describe a method for the biofabrication of skin equivalents that are fully bioprinted using an open market bioprinter, made with commercially available primary cells and natural hydrogels. The unique hydrogel formulation allows for the production of a human-like skin equivalent with minimal lateral tissue contraction in a multiwell plate format, thus making them suitable for high throughput bioprinting in a single print with fast print and relatively short incubation times. The morphology and barrier function of the fully three-dimensional bioprinted skin equivalents are validated by immunohistochemistry staining, optical coherence tomography, and permeation assays.
BibTeX:
@article{Derr2019,
  author = {Derr, Kristy and Zou, Jinyun and Luo, Keren and Song, Min Jae and Sittampalam, G. Sitta and Zhou, Chao and Michael, Samuel and Ferrer, Marc and Derr, Paige},
  title = {Fully 3D Bioprinted Skin Equivalent Constructs with Validated Morphology and Barrier Function},
  journal = {Tissue Engineering Part C: Methods},
  year = {2019},
  volume = {0},
  number = {ja},
  pages = {null},
  note = {PMID: 31007132},
  doi = {https://doi.org/10.1089/ten.TEC.2018.0318}
}
Daly, A.C. and Kelly, D.J. Biofabrication of spatially organised tissues by directing the growth of cellular spheroids within 3D printed polymeric microchambers 2019 Biomaterials
Vol. 197, pp. 194 - 206 
article DOI URL 
Abstract: Successful tissue engineering requires the generation of human scale implants that mimic the structure, composition and mechanical properties of native tissues. Here, we report a novel biofabrication strategy that enables the engineering of structurally organised tissues by guiding the growth of cellular spheroids within arrays of 3D printed polymeric microchambers. With the goal of engineering stratified articular cartilage, inkjet bioprinting was used to deposit defined numbers of mesenchymal stromal cells (MSCs) and chondrocytes into pre-printed microchambers. These jetted cell suspensions rapidly underwent condensation within the hydrophobic microchambers, leading to the formation of organised arrays of cellular spheroids. The microchambers were also designed to provide boundary conditions to these spheroids, guiding their growth and eventual fusion, leading to the development of stratified cartilage tissue with a depth-dependant collagen fiber architecture that mimicked the structure of native articular cartilage. Furthermore, the composition and biomechanical properties of the bioprinted cartilage was also comparable to the native tissue. Using multi-tool biofabrication, we were also able to engineer anatomically accurate, human scale, osteochondral templates by printing this microchamber system on top of a hypertrophic cartilage region designed to support endochondral bone formation and then maintaining the entire construct in long-term bioreactor culture to enhance tissue development. This bioprinting strategy provides a versatile and scalable approach to engineer structurally organised cartilage tissues for joint resurfacing applications.
BibTeX:
@article{Daly2019,
  author = {Andrew C. Daly and Daniel J. Kelly},
  title = {Biofabrication of spatially organised tissues by directing the growth of cellular spheroids within 3D printed polymeric microchambers},
  journal = {Biomaterials},
  year = {2019},
  volume = {197},
  pages = {194 - 206},
  url = {http://www.sciencedirect.com/science/article/pii/S0142961218308639},
  doi = {https://doi.org/10.1016/j.biomaterials.2018.12.028}
}
Creusen, G., Roshanasan, A., Garcia Lopez, J., Peneva, K. and Walther, A. Bottom-up design of model network elastomers and hydrogels from precise star polymers 2019 Polym. Chem., pp. -  article DOI  
Abstract: We introduce a platform for the simultaneous design of model network hydrogels and bulk elastomers based on well-defined water-soluble star polymers with a low glass transition temperature (Tg). This platform is enabled via the development of a synthetic route to a new family of 4-arm star polymers based on water-soluble poly(triethylene glycol methyl ether acrylate) (p(mTEGA)), which after quantitative introduction of functional end-groups can serve as suitable building blocks for model network formation. We first describe in detail the synthesis of highly defined star polymers using light and Cu-wire mediated Cu-based reversible deactivation radical polymerization. The resulting polymers exhibit narrow dispersities and controlled arm length at very high molecular weights, and feature a desirable low Tg of −55 °C. Subsequently, we elucidate the rational design of the stiffness and elasticity in covalent model network elastomers and hydrogels formed by fast photo-crosslinking for different arm lengths, and construct thermally reversible model network hydrogels based on dynamic supramolecular bonds. In addition, we describe preliminary 3D-printing applications. This work provides a key alternative to commonly used star-poly(ethylene glycol) (PEG) for model hydrogel networks, and demonstrates access to new main and side chain chemistries, thus chain stiffnesses and entanglement molecular weight, and, critically, enables the simultaneous study of the mechanical behavior of bulk network elastomers and swollen hydrogels with the same network topology. In a wider perspective, this work also highlights the need for advancing precision polymer chemistry to allow for an understanding of architectural control for the rational design of functional mechanical network materials.
BibTeX:
@article{Creusen2019,
  author = {Creusen, Guido and Roshanasan, Ardeshir and Garcia Lopez, Javier and Peneva, Kalina and Walther, Andreas},
  title = {Bottom-up design of model network elastomers and hydrogels from precise star polymers},
  journal = {Polym. Chem.},
  publisher = {The Royal Society of Chemistry},
  year = {2019},
  pages = {-},
  doi = {https://doi.org/10.1039/C9PY00731H}
}
Costa, P.F. Translating Biofabrication to the Market 2019 Trends in Biotechnology  article DOI URL 
Abstract: Biofabrication holds great potential to revolutionize important industries in the health, food, and textile sectors, but its translation to market is still challenging. I analyze the current state of innovation and commercialization in biofabrication and try to assess its limitations, strengths, and future progress.
BibTeX:
@article{Costa2019,
  author = {Pedro F. Costa},
  title = {Translating Biofabrication to the Market},
  journal = {Trends in Biotechnology},
  year = {2019},
  url = {http://www.sciencedirect.com/science/article/pii/S0167779919300915},
  doi = {https://doi.org/10.1016/j.tibtech.2019.04.013}
}
Cofiño, C., Perez-Amodio, S., Semino, C.E., Engel, E. and Mateos-Timoneda, M.A. Development of a Self-Assembled Peptide/Methylcellulose-Based Bioink for 3D Bioprinting 2019 Macromolecular Materials and Engineering
Vol. 0(0), pp. 1900353 
article DOI  
Abstract: Abstract The introduction of 3D bioprinting to fabricate living constructs with tailored architecture has provided a new paradigm for biofabrication, with the potential to overcome several drawbacks of conventional scaffold-based tissue regeneration strategies. Hydrogel-based materials are suitable candidates regarding cell biocompatibility but often display poor mechanical properties. Self-assembling peptides are a promising source of biomaterials to be used as 3D scaffolds based on their similarity to extracellular matrices (structurally and mechanically). In this study, an advanced bioink for biofabrication is presented based on the optimization of a RAD16-I-based biomaterial. The strategy followed to build 3D predefined structures by 3D printing is based on an enhancement of bioink viscosity by adding methylcellulose (MC) to a RAD16-I solution. The resultant constructs display high shape fidelity and stability and embedded human mesenchymal stem cells present high viability after 7 days of culture. Moreover, cells are also able to differentiate to the adipogenic lineage, suggesting the suitability of this novel biomaterial for soft tissue engineering applications.
BibTeX:
@article{Cofino2019,
  author = {Cofiño, Carla and Perez-Amodio, Soledad and Semino, Carlos E. and Engel, Elisabeth and Mateos-Timoneda, Miguel A.},
  title = {Development of a Self-Assembled Peptide/Methylcellulose-Based Bioink for 3D Bioprinting},
  journal = {Macromolecular Materials and Engineering},
  year = {2019},
  volume = {0},
  number = {0},
  pages = {1900353},
  doi = {https://doi.org/10.1002/mame.201900353}
}
Cernencu, A.I., Lungu, A., Stancu, I.-C., Serafim, A., Heggset, E., Syverud, K. and Iovu, H. Bioinspired 3D printable pectin-nanocellulose ink formulations 2019 Carbohydrate Polymers
Vol. 220, pp. 12 - 21 
article DOI URL 
Abstract: The assessment of several ink formulations for 3D printing based on two natural macromolecular compounds is presented. In the current research we have exploited the fast crosslinking potential of pectin and the remarkable shear-thinning properties of carboxylated cellulose nanofibrils, which is known to induce a desired viscoelastic behavior. Prior to 3D printing, the viscoelastic properties of the polysaccharide inks were evaluated by rheological measurements and injectability tests. The reliance of the printing parameters on the ink composition was established through one-dimensional lines printing, the base units of 3D-structures. The performance of the 3D-printed structures after ionic cross-linking was evaluated in terms of mechanical properties and rehydration behavior. MicroCT was also used to evaluate the morphology of the 3D-printed objects regarding the effect of pectin/nanocellulose ratio on the geometrical features of scaffolds. The proportionality between the two polymers proved to be the determining factor for the firmness and strength of the printed objects.
BibTeX:
@article{Cernencu2019,
  author = {Alexandra I. Cernencu and Adriana Lungu and Izabela-Cristina Stancu and Andrada Serafim and Ellinor Heggset and Kristin Syverud and Horia Iovu},
  title = {Bioinspired 3D printable pectin-nanocellulose ink formulations},
  journal = {Carbohydrate Polymers},
  year = {2019},
  volume = {220},
  pages = {12 - 21},
  url = {http://www.sciencedirect.com/science/article/pii/S0144861719305314},
  doi = {https://doi.org/10.1016/j.carbpol.2019.05.026}
}
Caetano, G., Wang, W., Murashima, A., Passarini, J.R., Bagne, L., Leite, M., Hyppolito, M., Al-Deyab, S., El-Newehy, M., Bártolo, P. and Frade, M.A.C. Tissue Constructs with Human Adipose-Derived Mesenchymal Stem Cells to Treat Bone Defects in Rats 2019 Materials
Vol. 12(14) 
article DOI URL 
Abstract: The use of porous scaffolds created by additive manufacturing is considered a viable approach for the regeneration of critical-size bone defects. This paper investigates the xenotransplantation of polycaprolactone (PCL) tissue constructs seeded with differentiated and undifferentiated human adipose-derived mesenchymal stem cells (hADSCs) to treat calvarial critical-sized defect in Wistar rats. PCL scaffolds without cells were also considered. In vitro and in vivo biological evaluations were performed to assess the feasibility of these different approaches. In the case of cell seeded scaffolds, it was possible to observe the presence of hADSCs in the rat tissue contributing directly (osteoblasts) and indirectly (stimulation by paracrine factors) to tissue formation, organization and mineralization. The presence of bone morphogenetic protein-2 (BMP-2) in the rat tissue treated with cell-seeded PCL scaffolds suggests that the paracrine factors of undifferentiated hADSC cells could stimulate BMP-2 production by surrounding cells, leading to osteogenesis. Moreover, BMP-2 acts synergistically with growth factors to induce angiogenesis, leading to higher numbers of blood vessels in the groups containing undifferentiated and differentiated hADSCs.
BibTeX:
@article{Caetano2019,
  author = {Caetano, Guilherme and Wang, Weiguang and Murashima, Adriana and Passarini, José Roberto and Bagne, Leonardo and Leite, Marcel and Hyppolito, Miguel and Al-Deyab, Salem and El-Newehy, Mohamed and Bártolo, Paulo and Frade, Marco Andrey Cipriani},
  title = {Tissue Constructs with Human Adipose-Derived Mesenchymal Stem Cells to Treat Bone Defects in Rats},
  journal = {Materials},
  year = {2019},
  volume = {12},
  number = {14},
  url = {https://www.mdpi.com/1996-1944/12/14/2268},
  doi = {https://doi.org/10.3390/ma12142268}
}
Azim, N., Hart, C., Sommerhage, F., Aubin, M., Hickman, J.J. and Rajaraman, S. Precision Plating of Human Electrogenic Cells on Microelectrodes Enhanced With Precision Electrodeposited Nano-Porous Platinum for Cell-Based Biosensing Applications 2019 Journal of Microelectromechanical Systems
Vol. 28(1), pp. 50-62 
article DOI URL 
Abstract: Microelectrode Arrays are established platforms for biosensing applications; however, limitations in electrode impedance and cell-electrode coupling still exist. In this paper, the SNR of 25 μm diameter gold (Au) microelectrodes was improved by decreasing the impedance with precision electrodeposition. SEM determined that N-P Pt. microelectrodes had nanoporous structures that filled the insulation cylinders. EIS, CV, and RMS noise measurements concluded that the optimized electrodeposition of N-P Pt. led to a lowered impedance of 18.36 kΩ ± 2.6 kΩ at 1 kHz, a larger double layer capacitance of 73 nF, and lowered RMS noise of 2.08±0.16 μV as compared to the values for Au of 159 kΩ ± 28 kΩ at 1 kHz, 17nF, and 3.14 ± 0.42 μV, respectively. Human motoneurons and human cardiomyocytes were cultured on N-P Pt. devices to assess their biocompatibility and signal quality. In order to improve the cell-electrode coupling, a precision plating technique was used. Both cell types were electrically active on devices for up to 10 weeks, demonstrated improved SNR, and expected responses to precision chemical and electrical stimulation. The modification of Au microelectrodes with nanomaterials in combination with precision culturing of human cell types provides cost effective, highly sensitive, well coupled and relevant biosensing platforms for medical and pharmaceutical research.
BibTeX:
@article{Azim2019,
  author = {Azim, N. and Hart, C. and Sommerhage, F. and Aubin, M. and Hickman, J. J. and Rajaraman, S.},
  title = {Precision Plating of Human Electrogenic Cells on Microelectrodes Enhanced With Precision Electrodeposited Nano-Porous Platinum for Cell-Based Biosensing Applications},
  journal = {Journal of Microelectromechanical Systems},
  year = {2019},
  volume = {28},
  number = {1},
  pages = {50--62},
  url = {https://ieeexplore.ieee.org/abstract/document/8604145/authors#authors},
  doi = {https://doi.org/10.1109/JMEMS.2018.2879577}
}
Angelopoulos, I., Allenby, M.C., Lim, M. and Zamorano, M. Engineering inkjet bioprinting processes toward translational therapies 2019 Biotechnology and Bioengineering
Vol. 0(0) 
article DOI  
Abstract: Abstract Bioprinting is the assembly of three-dimensional (3D) tissue constructs by layering cell-laden biomaterials using additive manufacturing techniques, offering great potential for tissue engineering and regenerative medicine. Such a process can be performed with high resolution and control by personalized or commercially available inkjet printers. However, bioprinting's clinical translation is significantly limited due to process engineering challenges. Upstream challenges include synthesis, cellular incorporation, and functionalization of “bioinks,” and extrusion of print geometries. Downstream challenges address sterilization, culture, implantation, and degradation. In the long run, bioinks must provide a microenvironment to support cell growth, development, and maturation and must interact and integrate with the surrounding tissues after implantation. Additionally, a robust, scaleable manufacturing process must pass regulatory scrutiny from regulatory bodies such as U.S. Food and Drug Administration, European Medicines Agency, or Australian Therapeutic Goods Administration for bioprinting to have a real clinical impact. In this review, recent advances in inkjet-based 3D bioprinting will be presented, emphasizing on biomaterials available, their properties, and the process to generate bioprinted constructs with application in medicine. Current challenges and the future path of bioprinting and bioinks will be addressed, with emphasis in mass production aspects and the regulatory framework bioink-based products must comply to translate this technology from the bench to the clinic.
BibTeX:
@article{Angelopoulos2019,
  author = {Angelopoulos, Ioannis and Allenby, Mark C. and Lim, Mayasari and Zamorano, Mauricio},
  title = {Engineering inkjet bioprinting processes toward translational therapies},
  journal = {Biotechnology and Bioengineering},
  year = {2019},
  volume = {0},
  number = {0},
  doi = {https://doi.org/10.1002/bit.27176}
}
Almeida, H.A., Costa, A.F., Ramos, C., Torres, C., Minondo, M., Bártolo, P.J., Nunes, A., Kemmoku, D. and da Silva, J.V.L. Additive Manufacturing Systems for Medical Applications: Case Studies 2019 Additive Manufacturing -- Developments in Training and Education, pp. 187-209  inbook DOI URL 
Abstract: Additive manufacturing is a growing technology and has become part of mankind's daily life, namely, at a technological, economic and social level. It i s a main topic of university lectures worldwide and it is applied by every industrial sector; in particular, it has been promoted in the medical field where its impact has increased and more and more systems are being acquired and developed for healthcare applications. Due to its capability to produce complex geometric parts directly from medical imaging data using biocompatible materials, additive manufacturing is a key technology for the fabrication of external (e.g. exoskeletons, or orthoses) and internal (permanent or temporary tissue implants) medical devices. This chapter introduces the main additive manufacturing techniques being used in the medical field, discusses main process steps and also presents several case studies including the development of a hand-wrist-forearm and finger orthosis, mandibular reconstruction, cranial prostheses, personalized insoles and bone composite scaffolds for tissue engineering.
BibTeX:
@inbook{Almeida2019,
  author = {Almeida, Henrique Amorim and Costa, Ana Filipa and Ramos, Carina and Torres, Carlos and Minondo, Mauricio and Bártolo, Paulo J. and Nunes, Amanda and Kemmoku, Daniel and da Silva, Jorge Vicente Lopes},
  title = {Additive Manufacturing Systems for Medical Applications: Case Studies},
  booktitle = {Additive Manufacturing -- Developments in Training and Education},
  publisher = {Springer International Publishing},
  year = {2019},
  pages = {187--209},
  url = {https://doi.org/10.1007/978-3-319-76084-1_13},
  doi = {https://doi.org/10.1007/978-3-319-76084-1_13}
}
Khaled, S.A., Alexander, M.R., Irvine, D.J., Wildman, R.D., Wallace, M.J., Sharpe, S., Yoo, J. and Roberts, C.J. Extrusion 3D Printing of Paracetamol Tablets from a Single Formulation with Tunable Release Profiles Through Control of Tablet Geometry 2018 AAPS PharmSciTech
Vol. 19(8), pp. 3403-3413 
article DOI  
Abstract: An extrusion-based 3D printer was used to fabricate paracetamol tablets with different geometries (mesh, ring and solid) from a single paste-based formulation formed from standard pharmaceutical ingredients. The tablets demonstrate that tunable drug release profiles can be achieved from this single formulation even with high drug loading (>thinspace80% w/w). The tablets were evaluated for drug release using a USP dissolution testing type I apparatus. The tablets showed well-defined release profiles (from immediate to sustained release) controlled by their different geometries. The dissolution results showed dependency of drug release on the surface area/volume (SA/V) ratio and the SA of the different tablets. The tablets with larger SA/V ratios and SA had faster drug release. The 3D printed tablets were also evaluated for physical and mechanical properties including tablet dimension, drug content, weight variation and breaking force and were within acceptable range as defined by the international standards stated in the US Pharmacopoeia. X-ray powder diffraction, differential scanning calorimetry and attenuated total reflectance Fourier transform infrared spectroscopy were used to identify the physical form of the active and to assess possible drug-excipient interactions. These data again showed that the tablets meet USP requirement. These results clearly demonstrate the potential of 3D printing to create unique pharmaceutical manufacturing, and potentially clinical, opportunities. The ability to use a single unmodified formulation to achieve defined release profiles could allow, for example, relatively straightforward personalization of medicines for individuals with different metabolism rates for certain drugs and hence could offer significant development and clinical opportunities.
BibTeX:
@article{Khaled2018a,
  author = {Khaled, Shaban A. and Alexander, Morgan R. and Irvine, Derek J. and Wildman, Ricky D. and Wallace, Martin J. and Sharpe, Sonja and Yoo, Jae and Roberts, Clive J.},
  title = {Extrusion 3D Printing of Paracetamol Tablets from a Single Formulation with Tunable Release Profiles Through Control of Tablet Geometry},
  journal = {AAPS PharmSciTech},
  year = {2018},
  volume = {19},
  number = {8},
  pages = {3403--3413},
  doi = {https://doi.org/10.1208/s12249-018-1107-z}
}
Zamani, Y., Mohammadi, J., Amoabediny, G., Visscher, D.O., Helder, M.N., Zandieh-Doulabi, B. and Klein-Nulend, J. Enhanced osteogenic activity by MC3T3-E1 pre-osteoblasts on chemically surface-modified poly(upepsilon-caprolactone) 3D-printed scaffolds compared to RGD immobilized scaffolds 2018 Biomedical Materials
Vol. 14(1), pp. 015008 
article DOI  
Abstract: In bone tissue engineering, the intrinsic hydrophobicity and surface smoothness of three-dimensional (3D)-printed poly(ε-caprolactone) scaffolds hamper cell attachment, proliferation and differentiation. This intrinsic hydrophobicity of poly(ε-caprolactone) can be overcome by surface modifications, such as surface chemical modification or immobilization of biologically active molecules on the surface. Moreover, surface chemical modification may alter surface smoothness. Whether surface chemical modification or immobilization of a biologically active molecule on the surface is more effective to enhance pre-osteoblast proliferation and differentiation is currently unknown. Therefore, we aimed to investigate the osteogenic response of MC3T3-E1 pre-osteoblasts to chemically surface-modified and RGD-immobilized 3D-printed poly(ε-caprolactone) scaffolds. Poly(ε-caprolactone) scaffolds were 3D-printed consisting of strands deposited layer by layer with alternating 0°/90° lay-down pattern. 3D-printed poly(ε-caprolactone) scaffolds were surface-modified by either chemical modification using 3 M sodium hydroxide (NaOH) for 24 or 72 h, or by RGD-immobilization. Strands were visualized by scanning electron microscopy. MC3T3-E1 pre-osteoblasts were seeded onto the scaffolds and cultured up to 14 d. The strands of the unmodified poly(ε-caprolactone) scaffold had a smooth surface. NaOH treatment changed the scaffold surface topography from smooth to a honeycomb-like surface pattern, while RGD immobilization did not alter the surface topography. MC3T3-E1 pre-osteoblast seeding efficiency was similar (44%–54%) on all scaffolds after 12 h. Cell proliferation increased from day 1 to day 14 in unmodified controls (1.9-fold), 24 h NaOH-treated scaffolds (3-fold), 72 h NaOH-treated scaffolds (2.2-fold), and RGD-immobilized scaffolds (4.5-fold). At day 14, increased collagenous matrix deposition was achieved only on 24 h NaOH-treated (1.8-fold) and RGD-immobilized (2.2-fold) scaffolds compared to unmodified controls. Moreover, 24 h, but not 72 h, NaOH-treated scaffolds, increased alkaline phosphatase activity by 5-fold, while the increase by RGD immobilization was only 2.5-fold. Only 24 h NaOH-treated scaffolds enhanced mineralization (2.0-fold) compared to unmodified controls. In conclusion, RGD immobilization (0.011 μg mg−1 scaffold) on the surface and 24 h NaOH treatment of the surface of 3D-printed PCL scaffold both enhance pre-osteoblast proliferation and matrix deposition while only 24 h NaOH treatment results in increased osteogenic activity, making it the treatment of choice to promote bone formation by osteogenic cells.
BibTeX:
@article{Zamani2018,
  author = {Yasaman Zamani and Javad Mohammadi and Ghassem Amoabediny and Dafydd O Visscher and Marco N Helder and Behrouz Zandieh-Doulabi and Jenneke Klein-Nulend},
  title = {Enhanced osteogenic activity by MC3T3-E1 pre-osteoblasts on chemically surface-modified poly(upepsilon-caprolactone) 3D-printed scaffolds compared to RGD immobilized scaffolds},
  journal = {Biomedical Materials},
  publisher = {IOP Publishing},
  year = {2018},
  volume = {14},
  number = {1},
  pages = {015008},
  doi = {https://doi.org/10.1088/1748-605x/aaeb82}
}
Li, H., Tan, Y.J. and Li, L. A strategy for strong interface bonding by 3D bioprinting of oppositely charged κ-carrageenan and gelatin hydrogels 2018 Carbohydrate Polymers
Vol. 198, pp. 261-269 
article URL 
Abstract: A promising approach for improving the interfacial bonding of a three-dimensionally (3D) printed multilayered structure has been investigated by taking advantage of the electrostatic interactions between two hydrogels with oppositely charges. Here, two hydrogels namely gelatin and κ-carrageenan, which are the cationic and anionic hydrogels respectively, are used. It is found that the interfacial bonding strength between these two oppositely charged hydrogels is significantly higher than that of a bilayered gelatin or a bilayered κ-carrageenan. The bioprinted multilayered κ-carrageenan-gelatin hydrogel construct demonstrates a very good biocompatibility and a good structure integrity at 37 °C. Our strategy also overcomes the limitation of using gelatin for bio-fabrication at 37 °C, without further post crosslinking.
BibTeX:
@article{Li2018b,
  author = {Li, Huijun and Tan, Yu Jun and Li, Lin},
  title = {A strategy for strong interface bonding by 3D bioprinting of oppositely charged κ-carrageenan and gelatin hydrogels},
  journal = {Carbohydrate Polymers},
  year = {2018},
  volume = {198},
  pages = {261--269},
  url = {http://www.sciencedirect.com/science/article/pii/S0144861718307355}
}
Petta, D., Armiento, A.R., Grijpma, D., Alini, M., Eglin, D. and D'Este, M. 3D bioprinting of a hyaluronan bioink through enzymatic-and visible light-crosslinking 2018 Biofabrication
Vol. 10(4), pp. 044104 
article DOI  
Abstract: Extrusion-based three-dimensional bioprinting relies on bioinks engineered to combine viscoelastic properties for extrusion and shape retention, and biological properties for cytocompatibility and tissue regeneration. To satisfy these conflicting requirements, bioinks often utilize either complex mixtures or complex modifications of biopolymers. In this paper we introduce and characterize a bioink exploiting a dual crosslinking mechanism, where an enzymatic reaction forms a soft gel suitable for cell encapsulation and extrusion, while a visible light photo-crosslinking allows shape retention of the printed construct. The influence of cell density and cell type on the rheological and printability properties was assessed correlating the printing outcomes with the damping factor, a rheological characteristic independent of the printing system. Stem cells, chondrocytes and fibroblasts were encapsulated, and their viability was assessed up to 14 days with live/dead, alamar blue and trypan blue assays. Additionally, the impact of the printing parameters on cell viability was investigated. Owing to its straightforward preparation, low modification, presence of two independent crosslinking mechanisms for tuning shear-thinning independently of the final shape fixation, the use of visible green instead of UV light, the possibility of encapsulating and sustaining the viability of different cell types, the hyaluronan bioink here presented is a valid biofabrication tool for producing 3D printed tissue-engineered constructs.
BibTeX:
@article{Petta2018,
  author = {D Petta and A R Armiento and D Grijpma and M Alini and D Eglin and M D'Este},
  title = {3D bioprinting of a hyaluronan bioink through enzymatic-and visible light-crosslinking},
  journal = {Biofabrication},
  publisher = {IOP Publishing},
  year = {2018},
  volume = {10},
  number = {4},
  pages = {044104},
  doi = {https://doi.org/10.1088/1758-5090/aadf58}
}
García-Lizarribar, A., Fernández-Garibay, X., Velasco-Mallorquí, F., G. Castaño, A., Samitier, J. and Ramón-Azcón, J. Composite Biomaterials as Long-Lasting Scaffolds for 3D Bioprinting of Highly Aligned Muscle Tissue 2018 Macromolecular Bioscience
Vol. 18, pp. 1800167 
article DOI  
BibTeX:
@article{Garcia-Lizarribar2018,
  author = {García-Lizarribar, Andrea and Fernández-Garibay, Xiomara and Velasco-Mallorquí, Ferran and G. Castaño, Albert and Samitier, Josep and Ramón-Azcón, Javier},
  title = {Composite Biomaterials as Long-Lasting Scaffolds for 3D Bioprinting of Highly Aligned Muscle Tissue},
  journal = {Macromolecular Bioscience},
  year = {2018},
  volume = {18},
  pages = {1800167},
  doi = {https://doi.org/10.1002/mabi.201800167}
}
Gleadall, A., Visscher, D., Yang, J., Thomas, D. and Segal, J. Review of additive manufactured tissue engineering scaffolds: relationship between geometry and performance 2018 Burns & Trauma
Vol. 6(1), pp. 19 
article DOI  
Abstract: Material extrusion additive manufacturing has rapidly grown in use for tissue engineering research since its adoption in the year 2000. It has enabled researchers to produce scaffolds with intricate porous geometries that were not feasible with traditional manufacturing processes. Researchers can control the structural geometry through a wide range of customisable printing parameters and design choices including material, print path, temperature, and many other process parameters. Currently, the impact of these choices is not fully understood. This review focuses on how the position and orientation of extruded filaments, which sometimes referred to as the print path, lay-down pattern, or simply ``scaffold design'', affect scaffold properties and biological performance. By analysing trends across multiple studies, new understanding was developed on how filament position affects mechanical properties. Biological performance was also found to be affected by filament position, but a lack of consensus between studies indicates a need for further research and understanding. In most research studies, scaffold design was dictated by capabilities of additive manufacturing software rather than free-form design of structural geometry optimised for biological requirements. There is scope for much greater application of engineering innovation to additive manufacture novel geometries. To achieve this, better understanding of biological requirements is needed to enable the effective specification of ideal scaffold geometries.
BibTeX:
@article{Gleadall2018,
  author = {Gleadall, Andrew and Visscher, Dafydd and Yang, Jing and Thomas, Daniel and Segal, Joel},
  title = {Review of additive manufactured tissue engineering scaffolds: relationship between geometry and performance},
  journal = {Burns & Trauma},
  year = {2018},
  volume = {6},
  number = {1},
  pages = {19},
  doi = {https://doi.org/10.1186/s41038-018-0121-4}
}
Gullo, M.R., Koeser, J., Ruckli, O., Eigenmann, A. and Hradetzky, D. Rapid Prototyping Method for 3D Printed Biomaterial Constructs with Vascular Structures 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), pp. 5729-5732  inproceedings DOI  
Abstract: This paper presents a fabrication method for rapid prototyping of 3D biomaterial constructs with vascular structures. The method relies on poloxamer fugitive ink, which is over casted with a custom-made alginate based model extracellular matrix (ECM). The presented method is simple to implement and compatible with standard cell culture workflows used in biomedical research and pharmaceutical development. We present the material preparation, gelation properties and printing methods in detail. First experiments demonstrate the suitability of the ECM constructs for 3D tissue culture.
BibTeX:
@inproceedings{Gullo2018,
  author = {Gullo, Maurizio R. and Koeser, J. and Ruckli, O. and Eigenmann, A. and Hradetzky, D.},
  title = {Rapid Prototyping Method for 3D Printed Biomaterial Constructs with Vascular Structures},
  booktitle = {40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)},
  year = {2018},
  pages = {5729-5732},
  doi = {https://doi.org/10.1109/EMBC.2018.8513630}
}
Gill, E.L., Li, X., Birch, M.A. and Huang, Y.Y.S. Multi-length scale bioprinting towards simulating microenvironmental cues 2018 Bio-Design and Manufacturing
Vol. 1(2), pp. 77-88 
article DOI  
Abstract: It is envisaged that the creation of cellular environments at multiple length scales, that recapitulate in vivo bioactive and structural roles, may hold the key to creating functional, complex tissues in the laboratory. This review considers recent advances in biofabrication and bioprinting techniques across different length scales. Particular focus is placed on 3D printing of hydrogels and fabrication of biomaterial fibres that could extend the feature resolution and material functionality of soft tissue constructs. The outlook from this review discusses how one might create and simulate microenvironmental cues in vitro. A fabrication platform that integrates the competencies of different biofabrication technologies is proposed. Such a multi-process, multiscale fabrication strategy may ultimately translate engineering capability into an accessible life sciences toolkit, fulfilling its potential to deliver in vitro disease models and engineered tissue implants.
BibTeX:
@article{Gill2018,
  author = {Gill, Elisabeth L. and Li, Xia and Birch, Mark A. and Huang, Yan Yan Shery},
  title = {Multi-length scale bioprinting towards simulating microenvironmental cues},
  journal = {Bio-Design and Manufacturing},
  year = {2018},
  volume = {1},
  number = {2},
  pages = {77--88},
  doi = {https://doi.org/10.1007/s42242-018-0014-1}
}
Choudhury, D., Anand, S. and Win Naing, M. The Arrival of Commercial Bioprinters - Towards 3D Bioprinting Revolution! 2018 International Journal of Bioprinting
Vol. 4 
article DOI  
BibTeX:
@article{Choudhury2018,
  author = {Choudhury, Deepak and Anand, Shivesh and Win Naing, May},
  title = {The Arrival of Commercial Bioprinters - Towards 3D Bioprinting Revolution!},
  journal = {International Journal of Bioprinting},
  year = {2018},
  volume = {4},
  doi = {https://doi.org/10.18063/IJB.v4i2.139}
}
Agarwala, S., Lee, J.M., Ng, W.L., Layani, M., Yeong, W.Y. and Magdassi, S. A novel 3D bioprinted flexible and biocompatible hydrogel bioelectronic platform 2018 Biosensors and Bioelectronics
Vol. 102(Supplement C), pp. 365 - 371 
article DOI URL 
Abstract: Abstract Bioelectronics platforms are gaining widespread attention as they provide a template to study the interactions between biological species and electronics. Decoding the effect of the electrical signals on the cells and tissues holds the promise for treating the malignant tissue growth, regenerating organs and engineering new-age medical devices. This work is a step forward in this direction, where bio- and electronic materials co-exist on one platform without any need for post processing. We fabricate a freestanding and flexible hydrogel based platform using 3D bioprinting. The fabrication process is simple, easy and provides a flexible route to print materials with preferred shapes, size and spatial orientation. Through the design of interdigitated electrodes and heating coil, the platform can be tailored to print various circuits for different functionalities. The biocompatibility of the printed platform is tested using C2C12 murine myoblasts cell line. Furthermore, normal human dermal fibroblasts (primary cells) are also seeded on the platform to ascertain the compatibility.
BibTeX:
@article{Agarwala2018,
  author = {Shweta Agarwala and Jia Min Lee and Wei Long Ng and Michael Layani and Wai Yee Yeong and Shlomo Magdassi},
  title = {A novel 3D bioprinted flexible and biocompatible hydrogel bioelectronic platform},
  journal = {Biosensors and Bioelectronics},
  year = {2018},
  volume = {102},
  number = {Supplement C},
  pages = {365 - 371},
  url = {http://www.sciencedirect.com/science/article/pii/S0956566317307698},
  doi = {https://doi.org/10.1016/j.bios.2017.11.039}
}
Monzón, M., Liu, C., Ajami, S., Oliveira, M., Donate, R., Ribeiro, V. and Reis, R.L. Functionally graded additive manufacturing to achieve functionality specifications of osteochondral scaffolds 2018 Bio-Design and Manufacturing
Vol. 1(1), pp. 69-75 
article DOI  
BibTeX:
@article{Monzon2018,
  author = {Monzón, Mario and Liu, Chaozong and Ajami, Sara and Oliveira, Miguel and Donate, Ricardo and Ribeiro, Viviana and Reis, Rui L.},
  title = {Functionally graded additive manufacturing to achieve functionality specifications of osteochondral scaffolds},
  journal = {Bio-Design and Manufacturing},
  year = {2018},
  volume = {1},
  number = {1},
  pages = {69--75},
  doi = {https://doi.org/10.1007/s42242-018-0003-4}
}
Tognato, R., Armiento, A.R., Bonfrate, V., Levato, R., Malda, J., Alini, M., Eglin, D., Giancane, G. and Serra, T. A Stimuli-Responsive Nanocomposite for 3D Anisotropic Cell-Guidance and Magnetic Soft Robotics 2018 Adv. Funct. Mater.
Vol. 29(9), pp. 1804647 
article DOI  
Abstract: Abstract Stimuli-responsive materials have the potential to enable the generation of new bioinspired devices with unique physicochemical properties and cell-instructive ability. Enhancing biocompatibility while simplifying the production methodologies, as well as enabling the creation of complex constructs, i.e., via 3D (bio)printing technologies, remains key challenge in the field. Here, a novel method is presented to biofabricate cellularized anisotropic hybrid hydrogel through a mild and biocompatible process driven by multiple external stimuli: magnetic field, temperature, and light. A low-intensity magnetic field is used to align mosaic iron oxide nanoparticles (IOPs) into filaments with tunable size within a gelatin methacryloyl matrix. Cells seeded on top or embedded within the hydrogel align to the same axes of the IOPs filaments. Furthermore, in 3D, C2C12 skeletal myoblasts differentiate toward myotubes even in the absence of differentiation media. 3D printing of the nanocomposite hydrogel is achieved and creation of complex heterogeneous structures that respond to magnetic field is demonstrated. By combining the advanced, stimuli-responsive hydrogel with the architectural control provided by bioprinting technologies, 3D constructs can also be created that, although inspired by nature, express functionalities beyond those of native tissue, which have important application in soft robotics, bioactuators, and bionic devices.
BibTeX:
@article{Tognato2018,
  author = {Tognato, Riccardo and Armiento, Angela R. and Bonfrate, Valentina and Levato, Riccardo and Malda, Jos and Alini, Mauro and Eglin, David and Giancane, Gabriele and Serra, Tiziano},
  title = {A Stimuli-Responsive Nanocomposite for 3D Anisotropic Cell-Guidance and Magnetic Soft Robotics},
  journal = {Adv. Funct. Mater.},
  publisher = {John Wiley & Sons, Ltd},
  year = {2018},
  volume = {29},
  number = {9},
  pages = {1804647},
  doi = {https://doi.org/10.1002/adfm.201804647}
}
Schaffner, M., Faber, J.A., Pianegonda, L., Rühs, P.A., Coulter, F. and Studart, A.R. 3D printing of robotic soft actuators with programmable bioinspired architectures 2018 Nature Communications
Vol. 9(1), pp. 878 
article DOI  
Abstract: Soft actuation allows robots to interact safely with humans, other machines, and their surroundings. Full exploitation of the potential of soft actuators has, however, been hindered by the lack of simple manufacturing routes to generate multimaterial parts with intricate shapes and architectures. Here, we report a 3D printing platform for the seamless digital fabrication of pneumatic silicone actuators exhibiting programmable bioinspired architectures and motions. The actuators comprise an elastomeric body whose surface is decorated with reinforcing stripes at a well-defined lead angle. Similar to the fibrous architectures found in muscular hydrostats, the lead angle can be altered to achieve elongation, contraction, or twisting motions. Using a quantitative model based on lamination theory, we establish design principles for the digital fabrication of silicone-based soft actuators whose functional response is programmed within the material's properties and architecture. Exploring such programmability enables 3D printing of a broad range of soft morphing structures.
BibTeX:
@article{Schaffner2018,
  author = {Schaffner, Manuel and Faber, Jakob A. and Pianegonda, Lucas and Rühs, Patrick A. and Coulter, Fergal and Studart, André R.},
  title = {3D printing of robotic soft actuators with programmable bioinspired architectures},
  journal = {Nature Communications},
  year = {2018},
  volume = {9},
  number = {1},
  pages = {878},
  doi = {https://doi.org/10.1038/s41467-018-03216-w}
}
Raghunath, M., Rimann, M., Kopanska, K. and Laternser, S. TEDD Annual Meeting with 3D Bioprinting Workshop 2018 CHIMIA
Vol. 72CHIMIA International Journal for Chemistry, pp. 76-79 
article URL 
Abstract: Bioprinting is the technology of choice for realizing functional tissues such as vascular system, muscle, cartilage and bone. In the future, bioprinting will influence the way we engineer tissues and bring it to a new level of physiological relevance. That was the topic of the 2017 TEDD Annual Meeting at ZHAW Waedenswil on 8th and 9th November. In an exciting workshop, the two companies regenHU Ltd. and CELLINK gave us an insight
into highly topical applications and collaborations in this domain.
BibTeX:
@article{Raghunath2018,
  author = {Raghunath, Michael and Rimann, Markus and Kopanska, Katarzyna and Laternser, Sandra},
  title = {TEDD Annual Meeting with 3D Bioprinting Workshop},
  booktitle = {CHIMIA International Journal for Chemistry},
  journal = {CHIMIA},
  year = {2018},
  volume = {72},
  pages = {76-79},
  url = { https://doi.org/10.2533/chimia.2018.76}
}
Prasopthum, A., Shakesheff, K.M. and Yang, J. Direct three-dimensional printing of polymeric scaffolds with nanofibrous topography 2018 Biofabrication
Vol. 10(2), pp. 025002 
article DOI  
Abstract: Three-dimensional (3D) printing is a powerful manufacturing tool for making 3D structures with well-defined architectures for a wide range of applications. The field of tissue engineering has also adopted this technology to fabricate scaffolds for tissue regeneration. The ability to control architecture of scaffolds, e.g. matching anatomical shapes and having defined pore size, has since been improved significantly. However, the material surface of these scaffolds is smooth and does not resemble that found in natural extracellular matrix (ECM), in particular, the nanofibrous morphology of collagen. This natural nanoscale morphology plays a critical role in cell behaviour. Here, we have developed a new approach to directly fabricate polymeric scaffolds with an ECM-like nanofibrous topography and defined architectures using extrusion-based 3D printing. 3D printed tall scaffolds with interconnected pores were created with disparate features spanning from nanometres to centimetres. Our approach removes the need for a sacrificial mould and subsequent mould removal compared to previous methods. Moreover, the nanofibrous topography of the 3D printed scaffolds significantly enhanced protein absorption, cell adhesion and differentiation of human mesenchymal stem cells when compared to those with smooth material surfaces. These 3D printed scaffolds with both defined architectures and nanoscale ECM-mimicking morphologies have potential applications in cartilage and bone regeneration.
BibTeX:
@article{Prasopthum2018,
  author = {Aruna Prasopthum and Kevin M Shakesheff and Jing Yang},
  title = {Direct three-dimensional printing of polymeric scaffolds with nanofibrous topography},
  journal = {Biofabrication},
  publisher = {IOP Publishing},
  year = {2018},
  volume = {10},
  number = {2},
  pages = {025002},
  doi = {https://doi.org/10.1088/1758-5090/aaa15b}
}
Allig, S., Mayer, M. and Thielemann, C. Workflow for bioprinting of cell-laden bioink 2018 Lekar a Technika
Vol. 48, pp. 46-51 
article URL 
BibTeX:
@article{Allig2018,
  author = {Allig, Sebastian and Mayer, Margot and Thielemann, Christiane},
  title = {Workflow for bioprinting of cell-laden bioink},
  journal = {Lekar a Technika},
  year = {2018},
  volume = {48},
  pages = {46-51},
  url = {https://ojs.cvut.cz/ojs/index.php/CTJ/article/view/4972}
}
Wang, H., das Neves Domingos, M.A. and Scenini, F. Advanced mechanical and thermal characterization of 3D bioextruded poly(ε-caprolactone)-based composites 2018 Rapid Prototyping Journal
Vol. 0(ja), pp. 00-00 
article DOI  
Abstract: Purpose The main purpose of the present work is to study the effect of nano hydroxyapatite (HA) and graphene oxide (GO) particles on thermal and mechanical performances of 3D printed poly(ε-caprolactone) (PCL) filaments used in Bone Tissue Engineering (BTE). Design/methodology/approach Raw materials were prepared by melt blending, followed by 3D printing via 3D Discovery (regenHU Ltd., CH) with all fabricating parameters kept constant. Filaments, including pure PCL, PCL/HA, and PCL/GO, were tested under the same conditions. Several techniques were used to mechanically, thermally, and microstructurally evaluate properties of these filaments, including Differential Scanning Calorimetry (DSC), tensile test, nano indentation, and Scanning Electron Microscope (SEM). Findings Results show that both HA and GO nano particles are capable of improving mechanical performance of PCL. Enhanced mechanical properties of PCL/HA result from reinforcing effect of HA, while a different mechanism is observed in PCL/GO, where degree of crystallinity plays an important role. In addition, GO is more efficient at enhancing mechanical performance of PCL compared with HA. Originality/value For the first time, a systematic study about effects of nano HA and GO particles on bioactive scaffolds produced by Additive Manufacturing (AM) for bone tissue engineering applications is conducted in this work. Mechanical and thermal behaviors of each sample, pure PCL, PCL/HA and PCL/GO, are reported, correlated, and compared with literature.
BibTeX:
@article{Wang2018,
  author = {Hanxiao Wang and Marco Andre das Neves Domingos and Fabio Scenini},
  title = {Advanced mechanical and thermal characterization of 3D bioextruded poly(ε-caprolactone)-based composites},
  journal = {Rapid Prototyping Journal},
  year = {2018},
  volume = {0},
  number = {ja},
  pages = {00-00},
  doi = {https://doi.org/10.1108/RPJ-10-2016-0165}
}
Visscher, D.O., Gleadall, A., Buskermolen, J.K., Burla, F., Segal, J., Koenderink, G.H., Helder, M.N. and van Zuijlen, P.P.M. Design and fabrication of a hybrid alginate hydrogel/poly(ε-caprolactone) mold for auricular cartilage reconstruction 2018 Journal of Biomedical Materials Research Part B: Applied Biomaterials
Vol. 0(0) 
article DOI  
Abstract: Abstract The aim of this study was to design and manufacture an easily assembled cartilage implant model for auricular reconstruction. First, the printing accuracy and mechanical properties of 3D-printed poly-ε-caprolactone (PCL) scaffolds with varying porosities were determined to assess overall material properties. Next, the applicability of alginate as cell carrier for the cartilage implant model was determined. Using the optimal outcomes of both experiments (in terms of (bio)mechanical properties, cell survival, neocartilage formation, and printing accuracy), a hybrid auricular implant model was developed. PCL scaffolds with 600 μm distances between strands exhibited the best mechanical properties and most optimal printing quality for further exploration. In alginate, chondrocytes displayed high cell survival ( 83% after 21 days) and produced cartilage-like matrix in vitro. Alginate beads cultured in proliferation medium exhibited slightly higher compressive moduli (6 kPa) compared to beads cultured in chondrogenic medium (3.5 kPa, p > .05). The final auricular mold could be printed with 300 μm pores and high fidelity, and the injected chondrocytes survived the culture period of 21 days. The presented hybrid auricular mold appears to be an adequate model for cartilage tissue engineering and may provide a novel approach to auricular cartilage regeneration for facial reconstruction. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res B Part B: Appl Biomater, 2018.
BibTeX:
@article{Visscher2018,
  author = {Visscher, D. O. and Gleadall, A. and Buskermolen, J. K. and Burla, F. and Segal, J. and Koenderink, G. H. and Helder, M. N. and van Zuijlen, P. P. M.},
  title = {Design and fabrication of a hybrid alginate hydrogel/poly(ε-caprolactone) mold for auricular cartilage reconstruction},
  journal = {Journal of Biomedical Materials Research Part B: Applied Biomaterials},
  year = {2018},
  volume = {0},
  number = {0},
  doi = {https://doi.org/10.1002/jbm.b.34264}
}
Shi, P., Tan, Y.S.E., Yeong, W.Y., Li, H.Y. and Laude, A. A bilayer photoreceptor‐retinal tissue model with gradient cell density design: A study of microvalve‐based bioprinting 2018 Journal of Tissue Engineering and Regenerative Medicine
Vol. 12(5), pp. 1297-1306 
article DOI  
Abstract: Abstract ARPE‐19 and Y79 cells were precisely and effectively delivered to form an in vitro retinal tissue model via 3D cell bioprinting technology. The samples were characterized by cell viability assay, haematoxylin and eosin and immunofluorescent staining, scanning electrical microscopy and confocal microscopy, and so forth. The bioprinted ARPE‐19 cells formed a high‐quality cell monolayer in 14 days. Manually seeded ARPE‐19 cells were poorly controlled during and after cell seeding, and they aggregated to form uneven cell layer. The Y79 cells were subsequently bioprinted on the ARPE‐19 cell monolayer to form 2 distinctive patterns. The microvalve‐based bioprinting is efficient and accurate to build the in vitro tissue models with the potential to provide similar pathological responses and mechanism to human diseases, to mimic the phenotypic endpoints that are comparable with clinical studies, and to provide a realistic prediction of clinical efficacy.
BibTeX:
@article{Shi2018,
  author = {Shi ,Pujiang and Tan, Yong Sheng Edgar and Yeong, Wai Yee and Li, Hoi Yeung and Laude, Augustinus},
  title = {A bilayer photoreceptor‐retinal tissue model with gradient cell density design: A study of microvalve‐based bioprinting},
  journal = {Journal of Tissue Engineering and Regenerative Medicine},
  year = {2018},
  volume = {12},
  number = {5},
  pages = {1297-1306},
  doi = {https://doi.org/10.1002/term.2661}
}
Schmieg, B., Schimek, A. and Franzreb, M. Development and performance of a 3D‐printable Polyethylenglycol‐Diacrylate hydrogel suitable for enzyme entrapment and long‐term biocatalytic applications 2018 Engineering in Life Sciences
Vol. 0(ja) 
article DOI URL 
Abstract: Physical entrapment of enzymes within a porous matrix is a fast and gentle process to immobilize biocatalysts to enable their recycling and long‐term use. This study introduces the development of a biocompatible 3D‐printing material suitable for enzyme entrapment, while having good rheological and UV‐hardening properties. Three different viscosity‐enhancing additives have been tested in combination with a polyethylenglycol‐diacrylate‐based hydrogel system. The addition of polyxanthan or hectorite clay particles results in hydrogels that degrade over hours or days, releasing entrapped compounds. In contrast, the addition of nanometer‐sized silicate particles ensures processability while preventing disintegration of the hydrogel. Lattice structures with a total height of 6 mm consisting of 40 layers were 3D‐printed with all materials and characterized by image analysis. Rheological measurements identified a shear stress window of 200 < τ < 500 Pa at shear rates of 25 s−1 and 25°C for well‐defined geometries with an extrusion‐based printhead. Enzymes immobilized in these long‐term stable hydrogel structures retained an effective activity of approximately 10% compared to the free enzyme in solution. It could be shown that the reduction of effective activity isn't caused by a significant reduction of the intrinsic enzyme activity but by mass transfer limitations within the printed hydrogel structures. This article is protected by copyright. All rights reserved
BibTeX:
@article{Schmieg2018,
  author = {Schmieg, Barbara and Schimek, Adrian and Franzreb, Matthias},
  title = {Development and performance of a 3D‐printable Polyethylenglycol‐Diacrylate hydrogel suitable for enzyme entrapment and long‐term biocatalytic applications},
  journal = {Engineering in Life Sciences},
  year = {2018},
  volume = {0},
  number = {ja},
  url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/elsc.201800030},
  doi = {https://doi.org/10.1002/elsc.201800030}
}
de Ruijter Mylène, Alexandre, R., Inge, D., Miguel, C. and Jos, M. Simultaneous Micropatterning of Fibrous Meshes and Bioinks for the Fabrication of Living Tissue Constructs 2018 Advanced Healthcare Materials
Vol. 0(0), pp. 1800418 
article DOI URL 
Abstract: Abstract Fabrication of biomimetic tissues holds much promise for the regeneration of cells or organs that are lost or damaged due to injury or disease. To enable the generation of complex, multicellular tissues on demand, the ability to design and incorporate different materials and cell types needs to be improved. Two techniques are combined: extrusion-based bioprinting, which enables printing of cell-encapsulated hydrogels; and melt electrowriting (MEW), which enables fabrication of aligned (sub)-micrometer fibers into a single-step biofabrication process. Composite structures generated by infusion of MEW fiber structures with hydrogels have resulted in mechanically and biologically competent constructs; however, their preparation involves a two-step fabrication procedure that limits freedom of design of microfiber architectures and the use of multiple materials and cell types. How convergence of MEW and extrusion-based bioprinting allows fabrication of mechanically stable constructs with the spatial distributions of different cell types without compromising cell viability and chondrogenic differentiation of mesenchymal stromal cells is demonstrated for the first time. Moreover, this converged printing approach improves freedom of design of the MEW fibers, enabling 3D fiber deposition. This is an important step toward biofabrication of voluminous and complex hierarchical structures that can better resemble the characteristics of functional biological tissues.
BibTeX:
@article{Ruijter2018,
  author = {de Ruijter Mylène and Ribeiro Alexandre and Dokter Inge and Castilho Miguel and Malda Jos},
  title = {Simultaneous Micropatterning of Fibrous Meshes and Bioinks for the Fabrication of Living Tissue Constructs},
  journal = {Advanced Healthcare Materials},
  year = {2018},
  volume = {0},
  number = {0},
  pages = {1800418},
  url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adhm.201800418},
  doi = {https://doi.org/10.1002/adhm.201800418}
}
Romanazzo, S., Vedicherla, S., Moran, C. and Kelly, D.J. Meniscus ECM‐functionalised hydrogels containing infrapatellar fat pad‐derived stem cells for bioprinting of regionally defined meniscal tissue 2018 Journal of Tissue Engineering and Regenerative Medicine
Vol. 12(3), pp. e1826-e1835 
article DOI  
Abstract: Abstract Injuries to the meniscus of the knee commonly lead to osteoarthritis. Current therapies for meniscus regeneration, including meniscectomies and scaffold implantation, fail to achieve complete functional regeneration of the tissue. This has led to increased interest in cell and gene therapies and tissue engineering approaches to meniscus regeneration. The implantation of a biomimetic implant, incorporating cells, growth factors, and extracellular matrix (ECM)‐derived proteins, represents a promising approach to functional meniscus regeneration. The objective of this study was to develop a range of ECM‐functionalised bioinks suitable for 3D bioprinting of meniscal tissue. To this end, alginate hydrogels were functionalised with ECM derived from the inner and outer regions of the meniscus and loaded with infrapatellar fat pad‐derived stem cells. In the absence of exogenously supplied growth factors, inner meniscus ECM promoted chondrogenesis of fat pad‐derived stem cells, whereas outer meniscus ECM promoted a more elongated cell morphology and the development of a more fibroblastic phenotype. With exogenous growth factors supplementation, a more fibrogenic phenotype was observed in outer ECM‐functionalised hydrogels supplemented with connective tissue growth factor, whereas inner ECM‐functionalised hydrogels supplemented with TGFβ3 supported the highest levels of Sox‐9 and type II collagen gene expression and sulfated glycosaminoglycans (sGAG) deposition. The final phase of the study demonstrated the printability of these ECM‐functionalised hydrogels, demonstrating that their codeposition with polycaprolactone microfibres dramatically improved the mechanical properties of the 3D bioprinted constructs with no noticeable loss in cell viability. These bioprinted constructs represent an exciting new approach to tissue engineering of functional meniscal grafts.
BibTeX:
@article{Romanazzo2018,
  author = {Romanazzo S. and Vedicherla S. and Moran C. and Kelly D.J.},
  title = {Meniscus ECM‐functionalised hydrogels containing infrapatellar fat pad‐derived stem cells for bioprinting of regionally defined meniscal tissue},
  journal = {Journal of Tissue Engineering and Regenerative Medicine},
  year = {2018},
  volume = {12},
  number = {3},
  pages = {e1826-e1835},
  doi = {https://doi.org/10.1002/term.2602}
}
Rayate, A. and Jain, P.K. A Review on 4D Printing Material Composites and Their Applications 2018 Materials Today: Proceedings
Vol. 5(9, Part 3), pp. 20474 - 20484 
article DOI URL 
Abstract: 4D printing is an extension of 3D printing in which stimuli-responsive active smart materials are used to produce the static structure. This static structure then converts into another structure when it is exposed to the stimulus. Type of stimulus may be light, heat, pH, water, magnetic field etc. depending upon the material selected for 3D printing. In recent advances, these dynamic structures developed by 3D printing process are used for actuators, smart devices, aesthetic primitives, smart textiles, and also in biomedical applications. This paper is about the brief overview of the advanced materials for 4D printing and their applications.
BibTeX:
@article{Rayate2018,
  author = {Amol Rayate and Prashant K. Jain},
  title = {A Review on 4D Printing Material Composites and Their Applications},
  journal = {Materials Today: Proceedings},
  year = {2018},
  volume = {5},
  number = {9, Part 3},
  pages = {20474 - 20484},
  note = {Materials Processing and characterization, 16th – 18th March 2018},
  url = {http://www.sciencedirect.com/science/article/pii/S2214785318315542},
  doi = {https://doi.org/10.1016/j.matpr.2018.06.424}
}
Pereira, F.D.A.S., Parfenov, V., Khesuani, Y.D., Ovsianikov, A. and Mironov, V. Commercial 3D Bioprinters 2018 3D Printing and Biofabrication, pp. 535-549  inbook DOI  
Abstract: The bioprinters are robotic devices, which enable 3D bioprinting. In this chapter, we provide classification of already existing commercially available 3D bioprinters and outline basic principles of their construction and functionalities. The emerging trends in the design and development of 3D bioprinters, perspectives of creation of new types of commercial 3D bioprinters based on new physical principles, including in situ bioprinters, as well as completely integrated organ biofabrication lines or ``human organ factories'' will be also discussed.
BibTeX:
@inbook{Pereira2018,
  author = {Pereira, Frederico David A. S. and Parfenov, Vladislav and Khesuani, Yusef D. and Ovsianikov, Aleksandr and Mironov, Vladimir},
  title = {Commercial 3D Bioprinters},
  booktitle = {3D Printing and Biofabrication},
  publisher = {Springer International Publishing},
  year = {2018},
  pages = {535--549},
  doi = {https://doi.org/10.1007/978-3-319-45444-3_12}
}
Peiffer, Q.C. Biofabrication: Tools for new therapeutics in regenerative medicine and drug delivery 2018 School: Queensland University of Technology  mastersthesis DOI URL 
Abstract: This thesis highlights how 3D fabrications techniques could revolutionize modern medicine, notably in the field of regenerative medicine and drug delivery. Two potential therapeutic usages of 3D fabricated polycaprolactone scaffolds are presented, the first project focuses on the regeneration of auricular cartilage while the second focus on implantable drug delivery system. If this work gives a glimpse of the potential of new fabrication methods, it remains clear from the results that significant steps are still to be undertaken to produce functional scaffolds able to regenerate tissue or to deliver drugs efficiently over an extended period.
BibTeX:
@mastersthesis{Peiffer2018,
  author = {Quentin C. Peiffer},
  title = {Biofabrication: Tools for new therapeutics in regenerative medicine and drug delivery},
  school = {Queensland University of Technology},
  year = {2018},
  url = {https://eprints.qut.edu.au/119359/},
  doi = {https://doi.org/10.5204/thesis.eprints.119359}
}
Park, H.S., Lee, J.S., Jung, H., Kim, D.Y., Kim, S.W., Sultan, M.T. and Park, C.H. An omentum-cultured 3D-printed artificial trachea: in vivo bioreactor 2018 Artificial Cells, Nanomedicine, and Biotechnology
Vol. 46(sup3), pp. S1131-S1140 
article DOI  
Abstract: AbstractThe purpose of this study was to evaluate whether the prior implantation of a 3D-printed polycaprolactone (PCL) artificial trachea in the omentum is beneficial for revascularization of the scaffold and reduces associated complications in the reconstruction of a circumferential tracheal defect. Ten New Zealand rabbits were divided into 2 groups: (1) PCL-OC group (PCL scaffold cultured in omentum for 2 weeks before transplantation) and (2) PCL group. In the PCL-OC group, newly formed connective tissue completely covered the luminal surface of the scaffold with mild inflammation at 2 weeks postoperatively; a minor degree of stenosis was noted at 8 weeks postoperatively. The PCL group showed scaffold exposure without any tissue regeneration at 2 weeks postoperatively, and a moderate degree of luminal stenosis 6 weeks after implantation. Histology revealed highly organized regenerated tissue composed of ciliated respiratory epithelium, and submucosal layer in the PCL-OC group. Neo-cartilage regeneration was noted in part of the regenerated tissue. The PCL group demonstrated severe inflammation and an unorganized structure compared to that of the PCL-OC group. In vivo omentum culture of the tracheal scaffold before transplantation is beneficial for rapid re-epithelialization and revascularization of the scaffold. It also prevents postoperative luminal stenosis.
BibTeX:
@article{Park2018,
  author = {Hae Sang Park and Ji Seung Lee and Harry Jung and Do Yeon Kim and Sang Wook Kim and Md. Tipu Sultan and Chan Hum Park},
  title = {An omentum-cultured 3D-printed artificial trachea: in vivo bioreactor},
  journal = {Artificial Cells, Nanomedicine, and Biotechnology},
  publisher = {Taylor & Francis},
  year = {2018},
  volume = {46},
  number = {sup3},
  pages = {S1131-S1140},
  note = {PMID: 30451550},
  doi = {https://doi.org/10.1080/21691401.2018.1533844}
}
Ng, W.L., Qi, J.T.Z., Yeong, W.Y. and Naing, M.W. Proof-of-concept: 3D bioprinting of pigmented human skin constructs 2018 Biofabrication
Vol. 10(2), pp. 025005 
article URL 
Abstract: Three-dimensional (3D) pigmented human skin constructs have been fabricated using a 3D bioprinting approach. The 3D pigmented human skin constructs are obtained from using three different types of skin cells (keratinocytes, melanocytes and fibroblasts from three different skin donors) and they exhibit similar constitutive pigmentation (pale pigmentation) as the skin donors. A two-step drop-on-demand bioprinting strategy facilitates the deposition of cell droplets to emulate the epidermal melanin units (pre-defined patterning of keratinocytes and melanocytes at the desired positions) and manipulation of the microenvironment to fabricate 3D biomimetic hierarchical porous structures found in native skin tissue. The 3D bioprinted pigmented skin constructs are compared to the pigmented skin constructs fabricated by conventional a manual-casting approach; in-depth characterization of both the 3D pigmented skin constructs has indicated that the 3D bioprinted skin constructs have a higher degree of resemblance to native skin tissue in term of the presence of well-developed stratified epidermal layers and the presence of a continuous layer of basement membrane proteins as compared to the manually-cast samples. The 3D bioprinting approach facilitates the development of 3D in vitro pigmented human skin constructs for potential toxicology testing and fundamental cell biology research.
BibTeX:
@article{Ng2018,
  author = {Wei Long Ng and Jovina Tan Zhi Qi and Wai Yee Yeong and May Win Naing},
  title = {Proof-of-concept: 3D bioprinting of pigmented human skin constructs},
  journal = {Biofabrication},
  year = {2018},
  volume = {10},
  number = {2},
  pages = {025005},
  url = {http://stacks.iop.org/1758-5090/10/i=2/a=025005}
}
Ng, W.L., Goh, M.H., Yeong, W.Y. and Naing, M.W. Applying macromolecular crowding to 3D bioprinting: fabrication of 3D hierarchical porous collagen-based hydrogel constructs 2018 Biomater. Sci.
Vol. 6, pp. 562-574 
article DOI URL 
Abstract: Native tissues and/or organs possess complex hierarchical porous structures that confer highly-specific cellular functions. Despite advances in fabrication processes, it is still very challenging to emulate the hierarchical porous collagen architecture found in most native tissues. Hence, the ability to recreate such hierarchical porous structures would result in biomimetic tissue-engineered constructs. Here, a single-step drop-on-demand (DOD) bioprinting strategy is proposed to fabricate hierarchical porous collagen-based hydrogels. Printable macromolecule-based bio-inks (polyvinylpyrrolidone, PVP) have been developed and printed in a DOD manner to manipulate the porosity within the multi-layered collagen-based hydrogels by altering the collagen fibrillogenesis process. The experimental results have indicated that hierarchical porous collagen structures could be achieved by controlling the number of macromolecule-based bio-ink droplets printed on each printed collagen layer. This facile single-step bioprinting process could be useful for the structural design of collagen-based hydrogels for various tissue engineering applications.
BibTeX:
@article{Ng2018a,
  author = {Ng, Wei Long and Goh, Min Hao and Yeong, Wai Yee and Naing, May Win},
  title = {Applying macromolecular crowding to 3D bioprinting: fabrication of 3D hierarchical porous collagen-based hydrogel constructs},
  journal = {Biomater. Sci.},
  publisher = {The Royal Society of Chemistry},
  year = {2018},
  volume = {6},
  pages = {562-574},
  url = {http://dx.doi.org/10.1039/C7BM01015J},
  doi = {https://doi.org/10.1039/C7BM01015J}
}
Mouser, V.H.M., Levato, R., Mensinga, A., Dhert, W.J.A., Gawlitta, D. and Malda, J. Bio-ink development for three-dimensional bioprinting of hetero-cellular cartilage constructs 2018 Connective Tissue Research
Vol. 0(0), pp. 1-15 
article DOI  
Abstract: ABSTRACTBioprinting is a promising tool to fabricate organized cartilage. This study aimed to investigate the printability of gelatin-methacryloyl/gellan gum (gelMA/gellan) hydrogels with and without methacrylated hyaluronic acid (HAMA), and to explore (zone-specific) chondrogenesis of chondrocytes, articular cartilage progenitor cells (ACPCs), and multipotent mesenchymal stromal cells (MSCs) embedded in these bio-inks.The incorporating of HAMA in gelMA/gellan bio-ink increased filament stability, as measured using a filament collapse assay, but did not influence (zone-specific) chondrogenesis of any of the cell types. Highest chondrogenic potential was observed for MSCs, followed by ACPCs, which displayed relatively high proteoglycan IV mRNA levels. Therefore, two-zone constructs were printed with gelMA/gellan/HAMA containing ACPCs in the superficial region and MSCs in the middle/deep region. Chondrogenic differentiation was confirmed, however, printing influence cellular differentiation.ACPC- and MSC-laden gelMA/gellan/HAMA hydrogels are of interest for the fabrication of cartilage constructs. Nevertheless, this study underscores the need for careful evaluation of the effects of printing on cellular differentiation.
BibTeX:
@article{Mouser2018,
  author = {Vivian H. M. Mouser and Riccardo Levato and Anneloes Mensinga and Wouter J. A. Dhert and Debby Gawlitta and Jos Malda},
  title = {Bio-ink development for three-dimensional bioprinting of hetero-cellular cartilage constructs},
  journal = {Connective Tissue Research},
  publisher = {Taylor & Francis},
  year = {2018},
  volume = {0},
  number = {0},
  pages = {1-15},
  note = {PMID: 30526130},
  doi = {https://doi.org/10.1080/03008207.2018.1553960}
}
Liu, F., Hinduja, S. and Bártolo, P. User interface tool for a novel plasma-assisted bio-additive extrusion system 2018 Rapid Prototyping Journal
Vol. 24(2), pp. 368-378 
article DOI  
Abstract: Purpose This paper aims to describe the control software of a novel manufacturing system called plasma-assisted bio-extrusion system (PABS), designed to produce complex multi-material and functionally graded scaffolds for tissue engineering applications. This fabrication system combines multiple pressure-assisted and screw-assisted printing heads and plasma jets. Control software allows the users to create single or multi-material constructs with uniform pore size or pore size gradients by changing the operation parameters, such as geometric parameters, lay-down pattern, filament distance, feed rate and layer thickness, and to produce functional graded scaffolds with different layer-by-layer coating/surface modification strategies by using the plasma modification system. Design/methodology/approach MATLAB GUI is used to develop the software, including the design of the user interface and the implementation of all mathematical programing for both multi-extrusion and plasma modification systems. Findings Based on the user definition, G programing codes are generated, enabling full integration and synchronization with the hardware of PABS. Single, multi-material and functionally graded scaffolds can be obtained by manipulating different materials, scaffold designs and processing parameters. The software is easy to use, allowing the efficient control of the PABS even for the fabrication of complex scaffolds. Originality/value This paper introduces a novel additive manufacturing system for tissue engineering applications describing in detail the software developed to control the system. This new fabrication system represents a step forward regarding the current state-of-the-art technology in the field of biomanufacturing, enabling the design and fabrication of more effective scaffolds matching the mechanical and surface characteristics of the surrounding tissue and enabling the incorporation of high number of cells uniformly distributed and the introduction of multiple cell types with positional specificity.
BibTeX:
@article{Liu2018,
  author = {Fengyuan Liu and Srichand Hinduja and Paulo Bártolo},
  title = {User interface tool for a novel plasma-assisted bio-additive extrusion system},
  journal = {Rapid Prototyping Journal},
  year = {2018},
  volume = {24},
  number = {2},
  pages = {368-378},
  doi = {https://doi.org/10.1108/RPJ-07-2016-0115}
}
Lim, S.H., Kathuria, H., Tan, J.J.Y. and Kang, L. 3D printed drug delivery and testing systems — a passing fad or the future? 2018 Advanced Drug Delivery Reviews
Vol. 132, pp. 139 - 168 
article DOI URL 
Abstract: The US Food and Drug Administration approval of the first 3D printed tablet in 2015 has ignited growing interest in 3D printing, or additive manufacturing (AM), for drug delivery and testing systems. Beyond just a novel method for rapid prototyping, AM provides key advantages over traditional manufacturing of drug delivery and testing systems. These includes the ability to fabricate complex geometries to achieve variable drug release kinetics; ease of personalising pharmacotherapy for patient and lowering the cost for fabricating personalised dosages. Furthermore, AM allows fabrication of complex and micron-sized tissue scaffolds and models for drug testing systems that closely resemble in vivo conditions. However, there are several limitations such as regulatory concerns that may impede the progression to market. Here, we provide an overview of the advantages of AM drug delivery and testing, as compared to traditional manufacturing techniques. Also, we discuss the key challenges and future directions for AM enabled pharmaceutical applications.
BibTeX:
@article{Lim2018,
  author = {Seng Han Lim and Himanshu Kathuria and Justin Jia Yao Tan and Lifeng Kang},
  title = {3D printed drug delivery and testing systems — a passing fad or the future?},
  journal = {Advanced Drug Delivery Reviews},
  year = {2018},
  volume = {132},
  pages = {139 - 168},
  note = {3D-Bioprinting and Micro-/Nano-Technology: Emerging Technologies in Biomedical Sciences},
  url = {http://www.sciencedirect.com/science/article/pii/S0169409X18301091},
  doi = {https://doi.org/10.1016/j.addr.2018.05.006}
}
Li, H., Tan, Y.J., Liu, S. and Li, L. Three-Dimensional Bioprinting of Oppositely Charged Hydrogels with Super Strong Interface Bonding 2018 ACS Applied Materials & Interfaces
Vol. 10(13), pp. 11164-11174 
article DOI  
Abstract: A novel strategy to improve the adhesion between printed layers of three-dimensional (3D) printed constructs is developed by exploiting the interaction between two oppositely charged hydrogels. Three anionic hydrogels [alginate, xanthan, and κ-carrageenan (Kca)] and three cationic hydrogels [chitosan, gelatin, and gelatin methacrylate (GelMA)] are chosen to find the optimal combination of two oppositely charged hydrogels for the best 3D printability with strong interface bonding. Rheological properties and printability of the hydrogels, as well as structural integrity of printed constructs in cell culture medium, are studied as functions of polymer concentration and the combination of hydrogels. Kca2 (2 wt % Kca hydrogel) and GelMA10 (10 wt % GelMA hydrogel) are found to be the best combination of oppositely charged hydrogels for 3D printing. The interfacial bonding between a Kca layer and a GelMA layer is proven to be significantly higher than that of the bilayered Kca or bilayered GelMA because of the formation of polyelectrolyte complexes between the oppositely charged hydrogels. A good cell viability of >96% is obtained for the 3D-bioprinted Kca–GelMA construct. This novel strategy has a great potential for 3D bioprinting of layered constructs with a strong interface bonding.
BibTeX:
@article{Li2018,
  author = {Li, Huijun and Tan, Yu Jun and Liu, Sijun and Li, Lin},
  title = {Three-Dimensional Bioprinting of Oppositely Charged Hydrogels with Super Strong Interface Bonding},
  journal = {ACS Applied Materials & Interfaces},
  year = {2018},
  volume = {10},
  number = {13},
  pages = {11164-11174},
  note = {PMID: 29517901},
  doi = {https://doi.org/10.1021/acsami.7b19730}
}
Li, H., Tan, C. and Li, L. Review of 3D printable hydrogels and constructs 2018 Materials & Design
Vol. 159, pp. 20 - 38 
article DOI URL 
Abstract: Three dimensional (3D) bioprinting technologies with appropriate bioinks are potentially able to fabricate artificial tissues or organs with precise control. A bioink is a mixture of biomaterial and living cells, which is a biomaterial for bioprinting. Hydrogels are the most appealing candidates of biomaterials because they have many similar features of the natural extracellular matrix and could also provide a highly hydrated environment for cell proliferation. In this field of bio-fabrication, particularly in bioprinting, the lack of suitable hydrogels remains a major challenge. Thus, choosing appropriate hydrogels for bioprinting is the key to print self-supporting 3D constructs. Most importantly, the considerations regarding the bioinks and the obtained constructs should be made clear. This review aims to provide the specific considerations regarding the important properties of a potential bioink and the generated 3D construct, including rheological, interfacial, structural, biological, and degradation properties, which are crucial for printing of complex and functional 3D structures. Among all of the above considerations, interfacial bonding is one of the important considerations of successfully obtaining a 3D structure. Unfortunately, it is rarely mentioned in the prior literature. This review also points out, for the first time, the characterization of a potential bioink from a rheological point of view. To provide readers with an understanding of the background, the review will first present current technologies for bioprinting and their limitations. Following this will be a summary and discussion of some frequently used hydrogels for bioprinting, and their respective limitations as well. The readers will be informed on the current limitations and achievements in 3D bioprinting. This review ultimately intends to help researchers to select or develop suitable bioinks for successfully bioprinting 3D constructs.
BibTeX:
@article{Li2018a,
  author = {Huijun Li and Cavin Tan and Lin Li},
  title = {Review of 3D printable hydrogels and constructs},
  journal = {Materials & Design},
  year = {2018},
  volume = {159},
  pages = {20 - 38},
  url = {http://www.sciencedirect.com/science/article/pii/S0264127518306385},
  doi = {https://doi.org/10.1016/j.matdes.2018.08.023}
}
Lee, M., Bae, K., Guillon, P., Chang, J., Arlov, Ø. and Zenobi-Wong, M. Exploitation of Cationic Silica Nanoparticles for Bioprinting of Large-Scale Constructs with High Printing Fidelity 2018 ACS Applied Materials & Interfaces
Vol. 10(44), pp. 37820-37828 
article DOI  
Abstract: Three-dimensional (3D) bioprinting allows the fabrication of 3D structures containing living cells whose 3D shape and architecture are matched to a patient. The feature is desirable to achieve personalized treatment of trauma or diseases. However, realization of this promising technique in the clinic is greatly hindered by inferior mechanical properties of most biocompatible bioink materials. Here, we report a novel strategy to achieve printing large constructs with high printing quality and fidelity using an extrusion-based printer. We incorporate cationic nanoparticles in an anionic polymer mixture, which significantly improves mechanical properties, printability, and printing fidelity of the polymeric bioink due to electrostatic interactions between the nanoparticles and polymers. Addition of cationic-modified silica nanoparticles to an anionic polymer mixture composed of alginate and gellan gum results in significantly increased zero-shear viscosity (1062 as well as storage modulus (486. As a result, it is possible to print a large (centimeter-scale) porous structure with high printing quality, whereas the use of the polymeric ink without the nanoparticles leads to collapse of the printed structure during printing. We demonstrate such a mechanical enhancement is achieved by adding nanoparticles within a certain size range (<100 nm) and depends on concentration and surface chemistry of the nanoparticles as well as the length of polymers. Furthermore, shrinkage and swelling of the printed constructs during cross-linking are significantly suppressed by addition of nanoparticles compared with the ink without nanoparticles, which leads to high printing fidelity after cross-linking. The incorporated nanoparticles do not compromise biocompatibility of the polymeric ink, where high cell viability (>90 and extracellular matrix secretion are observed for cells printed with nanocomposite inks. The design principle demonstrated can be applied for various anionic polymer-based systems, which could lead to achievement of 3D bioprinting-based personalized treatment.
BibTeX:
@article{Lee2018,
  author = {Lee, Mihyun and Bae, Kraun and Guillon, Pierre and Chang, Jin and Arlov, Øystein and Zenobi-Wong, Marcy},
  title = {Exploitation of Cationic Silica Nanoparticles for Bioprinting of Large-Scale Constructs with High Printing Fidelity},
  journal = {ACS Applied Materials & Interfaces},
  year = {2018},
  volume = {10},
  number = {44},
  pages = {37820-37828},
  doi = {https://doi.org/10.1021/acsami.8b13166}
}
Laternser, S., Keller, H., Leupin, O., Rausch, M., Graf-Hausner, U. and Rimann, M. A Novel Microplate 3D Bioprinting Platform for the Engineering of Muscle and Tendon Tissues 2018 SLAS TECHNOLOGY: Translating Life Sciences Innovation
Vol. 0(0), pp. 2472630318776594 
article DOI URL 
Abstract: Two-dimensional (2D) cell cultures do not reflect the in vivo situation, and thus it is important to develop predictive three-dimensional (3D) in vitro models with enhanced reliability and robustness for drug screening applications. Treatments against muscle-related diseases are becoming more prominent due to the growth of the aging population worldwide. In this study, we describe a novel drug screening platform with automated production of 3D musculoskeletal-tendon-like tissues. With 3D bioprinting, alternating layers of photo-polymerized gelatin-methacryloyl-based bioink and cell suspension tissue models were produced in a dumbbell shape onto novel postholder cell culture inserts in 24-well plates. Monocultures of human primary skeletal muscle cells and rat tenocytes were printed around and between the posts. The cells showed high viability in culture and good tissue differentiation, based on marker gene and protein expressions. Different printing patterns of bioink and cells were explored and calcium signaling with Fluo4-loaded cells while electrically stimulated was shown. Finally, controlled co-printing of tenocytes and myoblasts around and between the posts, respectively, was demonstrated followed by co-culture and co-differentiation. This screening platform combining 3D bioprinting with a novel microplate represents a promising tool to address musculoskeletal diseases.
BibTeX:
@article{Laternser2018,
  author = {Sandra Laternser and Hansjoerg Keller and Olivier Leupin and Martin Rausch and Ursula Graf-Hausner and Markus Rimann},
  title = {A Novel Microplate 3D Bioprinting Platform for the Engineering of Muscle and Tendon Tissues},
  journal = {SLAS TECHNOLOGY: Translating Life Sciences Innovation},
  year = {2018},
  volume = {0},
  number = {0},
  pages = {2472630318776594},
  note = {PMID: 29895208},
  url = { 

https://doi.org/10.1177/2472630318776594

}, doi = {https://doi.org/10.1177/2472630318776594} }
Kuzmenko, V., Karabulut, E., Pernevik, E., Enoksson, P. and Gatenholm, P. Tailor-made conductive inks from cellulose nanofibrils for 3D printing of neural guidelines 2018 Carbohydrate Polymers
Vol. 189, pp. 22 - 30 
article DOI URL 
Abstract: Neural tissue engineering (TE), an innovative biomedical method of brain study, is very dependent on scaffolds that support cell development into a functional tissue. Recently, 3D patterned scaffolds for neural TE have shown significant positive effects on cells by a more realistic mimicking of actual neural tissue. In this work, we present a conductive nanocellulose-based ink for 3D printing of neural TE scaffolds. It is demonstrated that by using cellulose nanofibrils and carbon nanotubes as ink constituents, it is possible to print guidelines with a diameter below 1 mm and electrical conductivity of 3.8 × 10−1 S cm−1. The cell culture studies reveal that neural cells prefer to attach, proliferate, and differentiate on the 3D printed conductive guidelines. To our knowledge, this is the first research effort devoted to using cost-effective cellulosic 3D printed structures in neural TE, and we suppose that much more will arise in the near future.
BibTeX:
@article{Kuzmenko2018,
  author = {Volodymyr Kuzmenko and Erdem Karabulut and Elin Pernevik and Peter Enoksson and Paul Gatenholm},
  title = {Tailor-made conductive inks from cellulose nanofibrils for 3D printing of neural guidelines},
  journal = {Carbohydrate Polymers},
  year = {2018},
  volume = {189},
  pages = {22 - 30},
  url = {http://www.sciencedirect.com/science/article/pii/S0144861718301231},
  doi = {https://doi.org/10.1016/j.carbpol.2018.01.097}
}
Kumari, S., Bargel, H., Anby, M.U., Lafargue, D. and Scheibel, T. Recombinant Spider Silk Hydrogels for Sustained Release of Biologicals 2018 ACS Biomaterials Science & Engineering
Vol. 4(5), pp. 1750-1759 
article DOI  
Abstract: Therapeutic biologics (i.e., proteins) have been widely recognized for the treatment, prevention, and cure of a variety of human diseases and syndromes. However, design of novel protein-delivery systems to achieve a nontoxic, constant, and efficient delivery with minimal doses of therapeutic biologics is still challenging. Here, recombinant spider silk-based materials are employed as a delivery system for the administration of therapeutic biologicals. Hydrogels made of the recombinant spider silk protein eADF4(C16) were used to encapsulate the model biologicals BSA, HRP, and LYS by direct loading or through diffusion, and their release was studied. Release of model biologicals from eADF4(C16) hydrogels is in part dependent on the electrostatic interaction between the biological and the recombinant spider silk protein variant used. In addition, tailoring the pore sizes of eADF4(C16) hydrogels strongly influenced the release kinetics. In a second approach, a particles-in-hydrogel system was used, showing a prolonged release in comparison with that of plain hydrogels (from days to week). The particle-enforced spider silk hydrogels are injectable and can be 3D printed. These initial studies indicate the potential of recombinant spider silk proteins to design novel injectable hydrogels that are suitable for delivering therapeutic biologics.
BibTeX:
@article{Kumari2018,
  author = {Kumari, Sushma and Bargel, Hendrik and Anby, Mette U. and Lafargue, David and Scheibel, Thomas},
  title = {Recombinant Spider Silk Hydrogels for Sustained Release of Biologicals},
  journal = {ACS Biomaterials Science & Engineering},
  year = {2018},
  volume = {4},
  number = {5},
  pages = {1750-1759},
  doi = {https://doi.org/10.1021/acsbiomaterials.8b00382}
}
Kokkinis, D., Bouville, F. and Studart, A.R. 3D Printing of Materials with Tunable Failure via Bioinspired Mechanical Gradients 2018 Advanced Materials
Vol. 30(19), pp. 1705808 
article DOI  
Abstract: Abstract Mechanical gradients are useful to reduce strain mismatches in heterogeneous materials and thus prevent premature failure of devices in a wide range of applications. While complex graded designs are a hallmark of biological materials, gradients in manmade materials are often limited to 1D profiles due to the lack of adequate fabrication tools. Here, a multimaterial 3D‐printing platform is developed to fabricate elastomer gradients spanning three orders of magnitude in elastic modulus and used to investigate the role of various bioinspired gradient designs on the local and global mechanical behavior of synthetic materials. The digital image correlation data and finite element modeling indicate that gradients can be effectively used to manipulate the stress state and thus circumvent the weakening effect of defect‐rich interfaces or program the failure behavior of heterogeneous materials. Implementing this concept in materials with bioinspired designs can potentially lead to defect‐tolerant structures and to materials whose tunable failure facilitates repair of biomedical implants, stretchable electronics, or soft robotics.
BibTeX:
@article{Kokkinis2018,
  author = {Dimitri Kokkinis and Florian Bouville and André R. Studart},
  title = {3D Printing of Materials with Tunable Failure via Bioinspired Mechanical Gradients},
  journal = {Advanced Materials},
  year = {2018},
  volume = {30},
  number = {19},
  pages = {1705808},
  doi = {https://doi.org/10.1002/adma.201705808}
}
Khaled, S.A., Alexander, M.R., Wildman, R.D., Wallace, M.J., Sharpe, S., Yoo, J. and Roberts, C.J. 3D extrusion printing of high drug loading immediate release paracetamol tablets 2018 International Journal of Pharmaceutics
Vol. 538(1), pp. 223 - 230 
article DOI URL 
Abstract: The manufacture of immediate release high drug loading paracetamol oral tablets was achieved using an extrusion based 3D printer from a premixed water based paste formulation. The 3D printed tablets demonstrate that a very high drug (paracetamol) loading formulation (80% w/w) can be printed as an acceptable tablet using a method suitable for personalisation and distributed manufacture. Paracetamol is an example of a drug whose physical form can present challenges to traditional powder compression tableting. Printing avoids these issues and facilitates the relatively high drug loading. The 3D printed tablets were evaluated for physical and mechanical properties including weight variation, friability, breaking force, disintegration time, and dimensions and were within acceptable range as defined by the international standards stated in the United States Pharmacopoeia (USP). X-ray Powder Diffraction (XRPD) was used to identify the physical form of the active. Additionally, XRPD, Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC) were used to assess possible drug-excipient interactions. The 3D printed tablets were evaluated for drug release using a USP dissolution testing type I apparatus. The tablets showed a profile characteristic of the immediate release profile as intended based upon the active/excipient ratio used with disintegration in less than 60 s and release of most of the drug within 5 min. The results demonstrate the capability of 3D extrusion based printing to produce acceptable high-drug loading tablets from approved materials that comply with current USP standards.
BibTeX:
@article{Khaled2018,
  author = {Shaban A. Khaled and Morgan R. Alexander and Ricky D. Wildman and Martin J. Wallace and Sonja Sharpe and Jae Yoo and Clive J. Roberts},
  title = {3D extrusion printing of high drug loading immediate release paracetamol tablets},
  journal = {International Journal of Pharmaceutics},
  year = {2018},
  volume = {538},
  number = {1},
  pages = {223 - 230},
  url = {http://www.sciencedirect.com/science/article/pii/S037851731830036X},
  doi = {https://doi.org/10.1016/j.ijpharm.2018.01.024}
}
Kelder, C., Bakker, A.D., Klein-Nulend, J. and Wismeijer, D. The 3D Printing of Calcium Phosphate with K-Carrageenan under Conditions Permitting the Incorporation of Biological Components—A Method 2018 Journal of Functional Biomaterials
Vol. 9(4) 
article DOI URL 
Abstract: Critical-size bone defects are a common clinical problem. The golden standard to treat these defects is autologous bone grafting. Besides the limitations of availability and co-morbidity, autografts have to be manually adapted to fit in the defect, which might result in a sub-optimal fit and impaired healing. Scaffolds with precise dimensions can be created using 3-dimensional (3D) printing, enabling the production of patient-specific, &lsquo;tailor-made&rsquo; bone substitutes with an exact fit. Calcium phosphate (CaP) is a popular material for bone tissue engineering due to its biocompatibility, osteoconductivity, and biodegradable properties. To enhance bone formation, a bioactive 3D-printed CaP scaffold can be created by combining the printed CaP scaffold with biological components such as growth factors and cytokines, e.g., vascular endothelial growth factor (VEGF), bone morphogenetic protein-2 (BMP-2), and interleukin-6 (IL-6). However, the 3D-printing of CaP with a biological component is challenging since production techniques often use high temperatures or aggressive chemicals, which hinders/inactivates the bioactivity of the incorporated biological components. Therefore, in our laboratory, we routinely perform extrusion-based 3D-printing with a biological binder at room temperature to create porous scaffolds for bone healing. In this method paper, we describe in detail a 3D-printing procedure for CaP paste with K-carrageenan as a biological binder.
BibTeX:
@article{Kelder2018,
  author = {Kelder, Cindy and Bakker, Astrid Diana and Klein-Nulend, Jenneke and Wismeijer, Daniël},
  title = {The 3D Printing of Calcium Phosphate with K-Carrageenan under Conditions Permitting the Incorporation of Biological Components—A Method},
  journal = {Journal of Functional Biomaterials},
  year = {2018},
  volume = {9},
  number = {4},
  url = {http://www.mdpi.com/2079-4983/9/4/57},
  doi = {https://doi.org/10.3390/jfb9040057}
}
Huang, Y.-A., Ho, C.T., Lin, Y.-H., Lee, C.-J., Ho, S.-M., Li, M.-C. and Hwang, E. Nanoimprinted Anisotropic Topography Preferentially Guides Axons and Enhances Nerve Regeneration 2018 Macromolecular Bioscience
Vol. 0(0), pp. 1800335 
article DOI  
Abstract: Abstract Surface topography has a profound effect on the development of the nervous system, such as neuronal differentiation and morphogenesis. While the interaction of neurons and the surface topography of their local environment is well characterized, the neuron–topography interaction during the regeneration process remains largely unknown. To address this question, an anisotropic surface topography resembling linear grooves made from poly(ethylene-vinyl acetate) (EVA), a soft and biocompatible polymer, using nanoimprinting, is established. It is found that neurons from both the central and peripheral nervous system can survive and grow on this grooved surface. Additionally, it is observed that axons but not dendrites specifically align with these grooves. Furthermore, it is demonstrated that neurons on the grooved surface are capable of regeneration after an on-site injury. More importantly, these injured neurons have an accelerated and enhanced regeneration. Together, the data demonstrate that this anisotropic topography guides axon growth and improves axon regeneration. This opens up the possibility to study the effect of surface topography on regenerating axons and has the potential to be developed into a medical device for treating peripheral nerve injuries.
BibTeX:
@article{Huang2018,
  author = {Huang, Yun-An and Ho, Chris T. and Lin, Yu-Hsuan and Lee, Chen-Ju and Ho, Szu-Mo and Li, Ming-Chia and Hwang, Eric},
  title = {Nanoimprinted Anisotropic Topography Preferentially Guides Axons and Enhances Nerve Regeneration},
  journal = {Macromolecular Bioscience},
  year = {2018},
  volume = {0},
  number = {0},
  pages = {1800335},
  doi = {https://doi.org/10.1002/mabi.201800335}
}
Gungor-Ozkerim, P.S., Inci, I., Zhang, Y.S., Khademhosseini, A. and Dokmeci, M.R. Bioinks for 3D bioprinting: an overview 2018 Biomater. Sci.
Vol. 6, pp. 915-946 
article DOI  
Abstract: Bioprinting is an emerging technology with various applications in making functional tissue constructs to replace injured or diseased tissues. It is a relatively new approach that provides high reproducibility and precise control over the fabricated constructs in an automated manner, potentially enabling high-throughput production. During the bioprinting process, a solution of a biomaterial or a mixture of several biomaterials in the hydrogel form, usually encapsulating the desired cell types, termed the bioink, is used for creating tissue constructs. This bioink can be cross-linked or stabilized during or immediately after bioprinting to generate the final shape, structure, and architecture of the designed construct. Bioinks may be made from natural or synthetic biomaterials alone, or a combination of the two as hybrid materials. In certain cases, cell aggregates without any additional biomaterials can also be adopted for use as a bioink for bioprinting processes. An ideal bioink should possess proper mechanical, rheological, and biological properties of the target tissues, which are essential to ensure correct functionality of the bioprinted tissues and organs. In this review, we provide an in-depth discussion of the different bioinks currently employed for bioprinting, and outline some future perspectives in their further development.
BibTeX:
@article{Gungor-Ozkerim2018,
  author = {Gungor-Ozkerim, P. Selcan and Inci, Ilyas and Zhang, Yu Shrike and Khademhosseini, Ali and Dokmeci, Mehmet Remzi},
  title = {Bioinks for 3D bioprinting: an overview},
  journal = {Biomater. Sci.},
  publisher = {The Royal Society of Chemistry},
  year = {2018},
  volume = {6},
  pages = {915-946},
  doi = {https://doi.org/10.1039/C7BM00765E}
}
Gretzinger, S., Beckert, N., Gleadall, A., Lee-Thedieck, C. and Hubbuch, J. 3D bioprinting – Flow cytometry as analytical strategy for 3D cell structures 2018 Bioprinting
Vol. 11, pp. e00023 
article DOI URL 
Abstract: The importance of 3D printing technologies increased significantly over the recent years. They are considered to have a huge impact in regenerative medicine and tissue engineering, since 3D bioprinting enables the production of cell-laden 3D scaffolds. Transition from academic research to pharmaceutical industry or clinical applications, however, is highly dependent on developing a robust and well-known process, while maintaining critical cell characteristics. Hence, a directed and systematic approach to 3D bioprinting process development is required, which also allows for the monitoring of these cell characteristics. This work presents the development of a flow cytometry-based analytical strategy as a tool for 3D bioprinting research. The development was based on a model process using a commercially available alginate-based bioink, the β-cell line INS-1E, and direct dispensing as 3D bioprinting method. We demonstrated that this set-up enabled viability and proliferation analysis. Additionally, use of an automated sampler facilitated high-throughput screenings. Finally, we showed that each process step, e.g. suspension of cells in bioink or 3D printing, cross-linking of the alginate scaffold after printing, has a crucial impact on INS-1E viability. This reflects the importance of process optimization in 3D bioprinting and the usefulness of the flow cytometry-based analytical strategy described here. The presented strategy has a great potential as a cell characterisation tool for 3D bioprinting and may contribute to a more directed process development.
BibTeX:
@article{Gretzinger2018,
  author = {Sarah Gretzinger and Nicole Beckert and Andrew Gleadall and Cornelia Lee-Thedieck and Jürgen Hubbuch},
  title = {3D bioprinting – Flow cytometry as analytical strategy for 3D cell structures},
  journal = {Bioprinting},
  year = {2018},
  volume = {11},
  pages = {e00023},
  url = {http://www.sciencedirect.com/science/article/pii/S2405886618300034},
  doi = {https://doi.org/10.1016/j.BPRINT.2018.e00023}
}
Fortunato, G.M., Maria, C.D., Eglin, D., Serra, T. and Vozzi, G. An ink-jet printed electrical stimulation platform for muscle tissue regeneration 2018 Bioprinting
Vol. 11, pp. e00035 
article DOI URL 
Abstract: Conducting polymeric materials have been used to modulate response of cells seeded on their surfaces. However, there is still major improvement to be made related to their biocompatibility, conductivity, stability in biological milieu, and processability toward truly tissue engineered functional device. In this work, conductive polymer, poly(3,4-ethylene-dioxythiophene):polystyrene-sulfonate (PEDOT:PSS), and its possible applications in tissue engineering were explored. In particular PEDOT:PSS solution was inkjet printed onto a gelatin substrate for obtaining a conductive structure. Mechanical and electrical characterizations, structural stability by swelling and degradation tests were carried out on different PEDOT-based samples obtained by varying the number of printed PEDOT layers from 5 to 50 on gelatin substrate. Biocompatibility of substrates was investigated on C2C12 myoblasts, through metabolic activity assay and imaging analysis during a 7-days culture period, to assess cell morphology, differentiation and alignment. The results of this first part allowed to proceed with the second part of the study in which these substrates were used for the design of an electrical stimulation device, with the aim of providing the external stimulus (3 V amplitude square wave at 1 and 2 Hz frequency) to guide myotubes alignment and enhance differentiation, having in this way promising applications in the field of muscle tissue engineering.
BibTeX:
@article{Fortunato2018,
  author = {Gabriele Maria Fortunato and Carmelo De Maria and David Eglin and Tiziano Serra and Giovanni Vozzi},
  title = {An ink-jet printed electrical stimulation platform for muscle tissue regeneration},
  journal = {Bioprinting},
  year = {2018},
  volume = {11},
  pages = {e00035},
  url = {http://www.sciencedirect.com/science/article/pii/S2405886618300344},
  doi = {https://doi.org/10.1016/j.bprint.2018.e00035}
}
Firth, J., Basit, A.W. and Gaisford, S. The Role of Semi-Solid Extrusion Printing in Clinical Practice 2018 3D Printing of Pharmaceuticals, pp. 133-151  inbook DOI  
Abstract: Residing under the umbrella term of `material extrusion', semi-solid extrusion (SSE) 3D printing deposits gels or pastes in sequential layers to create a solid object. The physical nature of the feedstock allows SSE to print quickly at low temperatures with little compromise in accuracy. As a result, the technology has been extensively adopted in the field of bioprinting in which SSE can print living cells able to create large, complex structures of human tissue. In terms of pharmaceutical formulation, SSE is relatively unused. By building on the advancements made in other fields, the unique attributes of SSE printing are beginning to come to the fore. In particular, the ability of SSE to create complex tablets at a low heat means the technology has the potential to make on demand, personalised dosages within a clinical setting. As a result, the infancy of SSE in pharmaceutics should not be seen as a sign of inferiority but rather a real opportunity to bring 3D printing into the clinic.
BibTeX:
@inbook{Firth2018,
  author = {Firth, Jack and Basit, Abdul W. and Gaisford, Simon},
  title = {The Role of Semi-Solid Extrusion Printing in Clinical Practice},
  booktitle = {3D Printing of Pharmaceuticals},
  publisher = {Springer International Publishing},
  year = {2018},
  pages = {133--151},
  doi = {https://doi.org/10.1007/978-3-319-90755-0_7}
}
Daly, A.C., Pitacco, P., Nulty, J., Cunniffe, G.M. and Kelly, D.J. 3D printed microchannel networks to direct vascularisation during endochondral bone repair 2018 Biomaterials
Vol. 162, pp. 34 - 46 
article DOI URL 
Abstract: Bone tissue engineering strategies that recapitulate the developmental process of endochondral ossification offer a promising route to bone repair. Clinical translation of such endochondral tissue engineering strategies will require overcoming a number of challenges, including the engineering of large and often anatomically complex cartilage grafts, as well as the persistence of core regions of avascular cartilage following their implantation into large bone defects. Here 3D printing technology is utilized to develop a versatile and scalable approach to guide vascularisation during endochondral bone repair. First, a sacrificial pluronic ink was used to 3D print interconnected microchannel networks in a mesenchymal stem cell (MSC) laden gelatin-methacryloyl (GelMA) hydrogel. These constructs (with and without microchannels) were next chondrogenically primed in vitro and then implanted into critically sized femoral bone defects in rats. The solid and microchanneled cartilage templates enhanced bone repair compared to untreated controls, with the solid cartilage templates (without microchannels) supporting the highest levels of total bone formation. However, the inclusion of 3D printed microchannels was found to promote osteoclast/immune cell invasion, hydrogel degradation, and vascularisation following implantation. In addition, the endochondral bone tissue engineering strategy was found to support comparable levels of bone healing to BMP-2 delivery, whilst promoting lower levels of heterotopic bone formation, with the microchanneled templates supporting the lowest levels of heterotopic bone formation. Taken together, these results demonstrate that 3D printed hypertrophic cartilage grafts represent a promising approach for the repair of complex bone fractures, particularly for larger defects where vascularisation will be a key challenge.
BibTeX:
@article{Daly2018,
  author = {Andrew C. Daly and Pierluca Pitacco and Jessica Nulty and Gráinne M. Cunniffe and Daniel J. Kelly},
  title = {3D printed microchannel networks to direct vascularisation during endochondral bone repair},
  journal = {Biomaterials},
  year = {2018},
  volume = {162},
  pages = {34 - 46},
  url = {http://www.sciencedirect.com/science/article/pii/S0142961218300772},
  doi = {https://doi.org/10.1016/j.biomaterials.2018.01.057}
}
Couck, S., Saint-Remi, J.C., der Perre, S.V., Baron, G.V., Minas, C., Ruch, P. and Denayer, J.F. 3D-printed SAPO-34 monoliths for gas separation 2018 Microporous and Mesoporous Materials
Vol. 255(Supplement C), pp. 185 - 191 
article DOI URL 
Abstract: Abstract A 3D printing method (the Direct Ink writing, DIW, method) is applied to produce SAPO-34 zeolite based structured adsorbents with the shape of a honeycomb-like monolith. The use of the 3D printing technique gives this structure a well-defined and easily adaptable geometry. As binder material, methyl cellulose was used. The SAPO-34 monolith was characterized by SEM as well as Ar and Hg porosimetry. The CO2 adsorption affinity, capacity and heat of adsorption were determined by recording high pressure adsorption isotherms at different temperatures, using the gravimetric technique. The separation potential was investigated by means of breakthrough experiments with mixtures of CO2 and N2. The experimental selectivity of CO2/N2 separation was compared to the selectivity as predicted by the Ideal Adsorbed Solution Theory. A drop in capacity was noticed during the experiments and N2 capacities were close to zero or slightly negative due to the very low adsorption, meaning absolute selectivity values could not be determined. However, due to the low N2 capacity, experimental selectivity is estimated to be excellent as was predicted with IAST. While the 3D printing is found to be a practical, fast and flexible route to generate monolithic adsorbent structures, improvements in formulation are required in terms of sample robustness for handling purposes and heat transfer characteristics of the obtained monoliths during gas separation.
BibTeX:
@article{Couck2018,
  author = {Sarah Couck and Julien Cousin-Saint-Remi and Stijn Van der Perre and Gino V. Baron and Clara Minas and Patrick Ruch and Joeri F.M. Denayer},
  title = {3D-printed SAPO-34 monoliths for gas separation},
  journal = {Microporous and Mesoporous Materials},
  year = {2018},
  volume = {255},
  number = {Supplement C},
  pages = {185 - 191},
  url = {http://www.sciencedirect.com/science/article/pii/S1387181117304869},
  doi = {https://doi.org/10.1016/j.micromeso.2017.07.014}
}
Chinga-Carrasco, G. Potential and Limitations of Nanocelluloses as Components in Biocomposite Inks for Three-Dimensional Bioprinting and for Biomedical Devices 2018 Biomacromolecules
Vol. 19(3), pp. 701-711 
article DOI  
Abstract: Three-dimensional (3D) printing has rapidly emerged as a new technology with a wide range of applications that includes biomedicine. Some common 3D printing methods are based on the suitability of biopolymers to be extruded through a nozzle to construct a 3D structure layer by layer. Nanocelluloses with specific rheological characteristics are suitable components to form inks for 3D printing. This review considers various nanocelluloses that have been proposed for 3D printing with a focus on the potential advantages, limitations, and requirements when used for biomedical devices and when used in contact with the human body.
BibTeX:
@article{Chinga-Carrasco2018,
  author = {Chinga-Carrasco, Gary},
  title = {Potential and Limitations of Nanocelluloses as Components in Biocomposite Inks for Three-Dimensional Bioprinting and for Biomedical Devices},
  journal = {Biomacromolecules},
  year = {2018},
  volume = {19},
  number = {3},
  pages = {701-711},
  note = {PMID: 29489338},
  doi = {https://doi.org/10.1021/acs.biomac.8b00053}
}
Caetano, G.F., Wang, W., Chiang, W.-H., Cooper, G., Diver, C., Blaker, J.J., Frade, M.A. and Bártolo, P. 3D-Printed Poly(ɛ-caprolactone)/Graphene Scaffolds Activated with P1-Latex Protein for Bone Regeneration 2018 3D Printing and Additive Manufacturing
Vol. 0(0), pp. null 
article DOI URL 
Abstract: Abstract Biomanufacturing is a relatively new research domain focusing on the use of additive manufacturing technologies, biomaterials, cells, and biomolecular signals to produce tissue constructs for tissue engineering. For bone regeneration, researchers are focusing on the use of polymeric and polymer/ceramic scaffolds seeded with osteoblasts or mesenchymal stem cells. However, high-performance scaffolds in terms of mechanical, cell stimulation, and biological performance are still required. This article investigates the use of an extrusion additive manufacturing system to produce poly(ɛ-caprolactone) (PCL) and PCL/graphene nanosheet scaffolds for bone applications. Scaffolds with regular and reproducible architecture and uniform dispersion of graphene were produced and coated with P1-latex protein extracted from the Hevea brasiliensis rubber tree. Results show that the obtained scaffolds cultivated with human adipose-derived stem cells present no toxicity effects. The presence of graphene nanosheet and P1-latex protein in the scaffolds increased cell proliferation compared with PCL scaffolds. Moreover, the presence of P1-latex protein promotes earlier osteogenic differentiation, suggesting that PCL/graphene/P1-latex protein scaffolds are suitable for bone regeneration applications.
BibTeX:
@article{Caetano2018,
  author = {Caetano, Guilherme Ferreira and Wang, Weiguang and Chiang, Wei-Hung and Cooper, Glen and Diver, Carl and Blaker, Jonny James and Frade, Marco Andrey and Bártolo, Paulo},
  title = {3D-Printed Poly(ɛ-caprolactone)/Graphene Scaffolds Activated with P1-Latex Protein for Bone Regeneration},
  journal = {3D Printing and Additive Manufacturing},
  year = {2018},
  volume = {0},
  number = {0},
  pages = {null},
  url = { 

https://doi.org/10.1089/3dp.2018.0012

}, doi = {https://doi.org/10.1089/3dp.2018.0012} }
Bastola, A., Paudel, M. and Li, L. Development of hybrid magnetorheological elastomers by 3D printing 2018 Polymer
Vol. 149, pp. 213 - 228 
article DOI URL 
Abstract: Intelligent or smart materials have one or more properties that can be significantly changed in a controlled fashion by external stimuli, such as temperature, pH, electric or magnetic fields, etc. Magnetorheological (MR) materials are a class of smart materials whose properties can be varied by applying an external magnetic field. In this work, the possibility of employing a suitable 3D printing technology for the development of one of the smart MR materials, the magnetorheological elastomer (MRE) has been explored. In order to achieve such 3D printing, a multi-material printing is implemented, where a controlled volume of MR fluid is encapsulated within an elastomer matrix in the layer-by-layer fashion. The choice of printing materials determines the final structure of the 3D printed hybrid MR elastomer. Printing with a vulcanizing MR suspension produces the solid MR structure inside the elastomer matrix while printing with a non-vulcanizing MR suspension (MR fluid) results in the structures that the MR fluid is encapsulated inside the elastomer matrix. The 3D printability of different materials has been studied by measuring their rheological properties and we found that the highly shear thinning and thixotropic properties are important for 3D printability. The quality of the printed filaments strongly depends on the key printing parameters such as extrusion pressure, initial height and feed rate. The experimental results from the forced vibration testing show that the 3D printed MR elastomers could change their elastic and damping properties when exposed to the external magnetic field. Furthermore, the 3D printed MR elastomer also exhibits the anisotropic behavior when the direction of the magnetic field is changed with respect to the orientation of the printed filaments. This study has demonstrated that the 3D printing is viable for fabrication of hybrid MR elastomers with controlled structures of magnetic particles or MR fluids.
BibTeX:
@article{Bastola2018,
  author = {A.K. Bastola and M. Paudel and L. Li},
  title = {Development of hybrid magnetorheological elastomers by 3D printing},
  journal = {Polymer},
  year = {2018},
  volume = {149},
  pages = {213 - 228},
  url = {http://www.sciencedirect.com/science/article/pii/S0032386118305809},
  doi = {https://doi.org/10.1016/j.polymer.2018.06.076}
}
Banerjee, H. and Ren, H. Electromagnetically Responsive Soft-Flexible Robots and Sensors for Biomedical Applications and Impending Challenges 2018 Electromagnetic Actuation and Sensing in Medical Robotics, pp. 43-72  inbook DOI  
Abstract: Advantages of flexible polymer materials with developments in refined magnetic actuation can be intertwined for a promising platform to work on a resilient, adaptable manipulator aimed at a range of biomedical applications. Moreover, soft magnetic material has an inherent property of high remanence like the permanent magnets which can be further refined to meet ever-increasing demands in untethered and safe-regulated medical environments. In this chapter, we focus mostly on different avenues and facets of flexible polymer materials in adaptable actuation and sensing in the context of magnetic field for range of biomedical applications.
BibTeX:
@inbook{Banerjee2018,
  author = {Banerjee, Hritwick and Ren, Hongliang},
  title = {Electromagnetically Responsive Soft-Flexible Robots and Sensors for Biomedical Applications and Impending Challenges},
  booktitle = {Electromagnetic Actuation and Sensing in Medical Robotics},
  publisher = {Springer Singapore},
  year = {2018},
  pages = {43--72},
  doi = {https://doi.org/10.1007/978-981-10-6035-9_3}
}
Aied, A., Song, W., Wang, W., Baki, A. and Sigen, A. 3D Bioprinting of stimuli-responsive polymers synthesised from DE-ATRP into soft tissue replicas 2018 Bioprinting  article DOI URL 
Abstract: Synthetic polymers possess more reproducible physical and chemical properties than their naturally occurring counterparts. They have also emerged as an important alternative for fabricating tissue substitutes because they can be molecularly tailored to have vast array of molecular weights, block structures, active functional groups, and mechanical properties. To this date however, there has been very few successful and fully functional synthetic tissue and organ substitutes and with the rapidly spreading 3D printing technology beginning to reshape the tissue engineering and regenerative field, the need for an effective, safe, and bio printable biomaterial is becoming more and more urgent. Here, we have developed a synthetic polymer from controlled living radical polymerisation that can be printed into well-defined structures. The polymer showed low cytotoxicity before and after printing. Additionally, the incorporation of gelatine-methacrylate coated PLGA microparticles within the hydrogel provided cell adhesion surfaces for cell proliferation. The results point to possible application of the microparticle seeded, synthetic hydrogel as a direct printable tissue or organ substitute.
BibTeX:
@article{Aied2018,
  author = {Ahmed Aied and Wenhui Song and Wenxin Wang and Abdulrahman Baki and A. Sigen},
  title = {3D Bioprinting of stimuli-responsive polymers synthesised from DE-ATRP into soft tissue replicas},
  journal = {Bioprinting},
  year = {2018},
  url = {http://www.sciencedirect.com/science/article/pii/S2405886617300210},
  doi = {https://doi.org/10.1016/j.bprint.2018.02.002}
}
Suntornnond, R., Tan, E., An, J. and Chua, C. A highly printable and biocompatible hydrogel composite for direct printing of soft and perfusable vasculature-like structures 2017 Scientific Reports
Vol. 7(16902) 
article DOI URL 
Abstract: Vascularization is one major obstacle in bioprinting and tissue engineering. In order to create thick tissues or organs that can function like original body parts, the presence of a perfusable vascular system is essential. However, it is challenging to bioprint a hydrogel-based three-dimensional vasculature-like structure in a single step. In this paper, we report a new hydrogel-based composite that offers impressive printability, shape integrity, and biocompatibility for 3D bioprinting of a perfusable complex vasculature-like structure. The hydrogel composite can be used on a non-liquid platform and is printable at human body temperature. Moreover, the hydrogel composite supports both cell proliferation and cell differentiation. Our results represent a potentially new vascularization strategy for 3D bioprinting and tissue engineering.
BibTeX:
@article{Suntornnond2017,
  author = {Suntornnond, R. and Tan, E.Y.S. and An, J. and Chua, C.K.},
  title = {A highly printable and biocompatible hydrogel composite for direct printing of soft and perfusable vasculature-like structures},
  journal = {Scientific Reports},
  year = {2017},
  volume = {7},
  number = {16902},
  url = {http://www.nature.com/articles/s41598-017-17198-0},
  doi = {https://doi.org/10.1038/s41598-017-17198-0}
}
Schroeder, T.B.H., Guha, A., Lamoureux, A., VanRenterghem, G., Sept, D., Shtein, M., Yang, J. and Mayer, M. An electric-eel-inspired soft power source from stacked hydrogels 2017 Nature
Vol. 552, pp. 214 
article DOI  
Abstract: Progress towards the integration of technology into livingo ganisms requires electrical power sources that are biocompatible, mechanically flexible, and able to harness the chemical energy available inside biological systems. Conventional batteries were not designed with these criteria in mind. The electric organ of the knifefish Electrophorus electricus (commonly known as the electric eel) is, however, an example of an electrical power source that operates within biological constraints while featuring power characteristics that include peak potential differences of 600 volts and currents of 1 ampere1,2. Here we introduce an electric eel-inspired power concept that uses gradients of ions between miniature polyacrylamide hydrogel compartments bounded by a repeating sequence of cation- and anion-selective hydrogel membranes. The system uses a scalable stacking or folding geometry
that generates 110 volts at open circuit or 27 milliwatts per square
metre per gel cell upon simultaneous, self-registered mechanical
contact activation of thousands of gel compartments in series while
circumventing power dissipation before contact. Unlike typical
batteries, these systems are soft, flexible, transparent, and potentially
biocompatible. These characteristics suggest that artificial electric
organs could be used to power next-generation implant materials
such as pacemakers, implantable sensors, or prosthetic devices in
hybrids of living and non-living systems3–6.�
BibTeX:
@article{Schroeder2017,
  author = {Schroeder, Thomas B. H. and Guha, Anirvan and Lamoureux, Aaron and VanRenterghem, Gloria and Sept, David and Shtein, Max and Yang, Jerry and Mayer, Michael},
  title = {An electric-eel-inspired soft power source from stacked hydrogels},
  journal = {Nature},
  publisher = {Macmillan Publishers Limited, part of Springer Nature. All rights reserved.},
  year = {2017},
  volume = {552},
  pages = {214},
  doi = {https://doi.org/10.1038/nature24670}
}
Nguyen, D., Hägg, D., Forsman, A., Ekholm, J., Nimkingratana, P., Brantsing, C., Kalogeropoulos, T., Zaunz, S., Concaro, S., Brittberg, M., Lindahl, A., Gatenholm, P., Enejder, A. and Simonsson, S. Cartilage Tissue Engineering by the 3D Bioprinting of iPS Cells in a Nanocellulose/Alginate Bioink 2017 Scientific Reports
Vol. 7Scientific Reports 
article DOI  
Abstract: Cartilage lesions can progress into secondary osteoarthritis and cause severe clinical problems in numerous patients. As a prospective treatment of such lesions, human-derived induced pluripotent stem cells (iPSCs) were shown to be 3D bioprinted into cartilage mimics using a nanofibrillated cellulose (NFC) composite bioink when co-printed with irradiated human chondrocytes. Two bioinks were investigated: NFC with alginate (NFC/A) or hyaluronic acid (NFC/HA). Low proliferation and phenotypic changes away from pluripotency were seen in the case of NFC/HA. However, in the case of the 3D-bioprinted NFC/A (60/40, dry weight % ratio) constructs, pluripotency was initially maintained, and after five weeks, hyaline-like cartilaginous tissue with collagen type II expression and lacking tumorigenic Oct4 expression was observed in 3D -bioprinted NFC/A (60/40, dry weight % relation) constructs. Moreover, a marked increase in cell number within the cartilaginous tissue was detected by 2-photon fluorescence microscopy, indicating the importance of high cell densities in the pursuit of achieving good survival after printing. We conclude that NFC/A bioink is suitable for bioprinting iPSCs to support cartilage production in co-cultures with irradiated chondrocytes.
BibTeX:
@article{Nguyen2017,
  author = {Nguyen, Duong and Hägg, Daniel and Forsman, Alma and Ekholm, Josefine and Nimkingratana, Puwapong and Brantsing, Camilla and Kalogeropoulos, Theodoros and Zaunz, Samantha and Concaro, Sebastian and Brittberg, Mats and Lindahl, Anders and Gatenholm, Paul and Enejder, Annika and Simonsson, Stina},
  title = {Cartilage Tissue Engineering by the 3D Bioprinting of iPS Cells in a Nanocellulose/Alginate Bioink},
  booktitle = {Scientific Reports},
  journal = {Scientific Reports},
  year = {2017},
  volume = {7},
  doi = {https://doi.org/10.1038/s41598-017-00690-y}
}
Freeman, F.E. and Kelly, D.J. Tuning Alginate Bioink Stiffness and Composition for Controlled Growth Factor Delivery and to Spatially Direct MSC Fate within Bioprinted Tissues 2017 Scientific Reports
Vol. 7(1), pp. 17042 
article DOI  
Abstract: Alginate is a commonly used bioink in 3D bioprinting. Matrix stiffness is a key determinant of mesenchymal stem cell (MSC) differentiation, suggesting that modulation of alginate bioink mechanical properties represents a promising strategy to spatially regulate MSC fate within bioprinted tissues. In this study, we define a printability window for alginate of differing molecular weight (MW) by systematically varying the ratio of alginate to ionic crosslinker within the bioink. We demonstrate that the MW of such alginate bioinks, as well as the choice of ionic crosslinker, can be tuned to control the mechanical properties (Young’s Modulus, Degradation Rate) of 3D printed constructs. These same factors are also shown to influence growth factor release from the bioinks. We next explored if spatially modulating the stiffness of 3D bioprinted hydrogels could be used to direct MSC fate inside printed tissues. Using the same alginate and crosslinker, but varying the crosslinking ratio, it is possible to bioprint constructs with spatially varying mechanical microenvironments. Moreover, these spatially varying microenvironments were found to have a significant effect on the fate of MSCs within the alginate bioinks, with stiffer regions of the bioprinted construct preferentially supporting osteogenesis over adipogenesis.
BibTeX:
@article{Freeman2017,
  author = {Freeman, Fiona E. and Kelly, Daniel J.},
  title = {Tuning Alginate Bioink Stiffness and Composition for Controlled Growth Factor Delivery and to Spatially Direct MSC Fate within Bioprinted Tissues},
  journal = {Scientific Reports},
  year = {2017},
  volume = {7},
  number = {1},
  pages = {17042},
  doi = {https://doi.org/10.1038/s41598-017-17286-1}
}
Levato, R., Webb, W.R., Otto, I.A., Mensinga, A., Zhang, Y., van Rijen, M., van Weeren, R., Khan, I.M. and Malda, J. The bio in the ink: cartilage regeneration with bioprintable hydrogels and articular cartilage-derived progenitor cells 2017 Acta Biomaterialia
Vol. 61(Supplement C), pp. 41-53 
article URL 
BibTeX:
@article{Levato2017,
  author = {Levato, Riccardo and Webb, William R. and Otto, Iris A. and Mensinga, Anneloes and Zhang, Yadan and van Rijen, Mattie and van Weeren, René and Khan, Ilyas M. and Malda, Jos},
  title = {The bio in the ink: cartilage regeneration with bioprintable hydrogels and articular cartilage-derived progenitor cells},
  journal = {Acta Biomaterialia},
  year = {2017},
  volume = {61},
  number = {Supplement C},
  pages = {41--53},
  url = {http://www.sciencedirect.com/science/article/pii/S1742706117304956}
}
Bertlein, S., Brown, G., Lim, K., Jungst, T., Boeck, T., Blunk, T., Tessmar, J., J. Hooper, G., Woodfield, T. and Groll, J. Thiol-Ene Clickable Gelatin: A Platform Bioink for Multiple 3D Biofabrication Technologies 2017 Advanced Materials  article DOI  
Abstract: Bioprinting can be defined as the art of combining materials and cells to fabricate designed, hierarchical 3D hybrid constructs. Suitable materials, so called bioinks, have to comply with challenging rheological processing demands and rapidly form a stable hydrogel postprinting in a cytocompatible manner. Gelatin is often adopted for this purpose, usually modified with (meth-)acryloyl functionalities for postfabrication curing by free radical photopolymerization, resulting in a hydrogel that is cross-linked via nondegradable polymer chains of uncontrolled length. The application of allylated gelatin (GelAGE) as a thiol-ene clickable bioink for distinct biofabrication applications is reported. Curing of this system occurs via dimerization and yields a network with flexible properties that offer a wider biofabrication window than (meth-)acryloyl chemistry, and without additional nondegradable components. An in-depth analysis of GelAGE synthesis is conducted, and standard UV-initiation is further compared with a recently described visible-light-initiator system for GelAGE hydrogel formation. It is demonstrated that GelAGE may serve as a platform bioink for several biofabrication technologies by fabricating constructs with high shape fidelity via lithography-based (digital light processing) 3D printing and extrusion-based 3D bioprinting, the latter supporting long-term viability postprinting of encapsulated chondrocytes.
BibTeX:
@article{Bertlein2017a,
  author = {Bertlein, Sarah and Brown, Gabriella and Lim, Khoon and Jungst, Tomasz and Boeck, Thomas and Blunk, Torsten and Tessmar, Joerg and J. Hooper, Gary and Woodfield, Tim and Groll, Jürgen},
  title = {Thiol-Ene Clickable Gelatin: A Platform Bioink for Multiple 3D Biofabrication Technologies},
  journal = {Advanced Materials},
  year = {2017},
  doi = {https://doi.org/10.1002/adma.201703404}
}
Mancini, I., Vindas Bolaños, R., Brommer, H., Castilho, M., Ribeiro, A., van Loon, J., Mensinga, A., Rijen, M., Malda, J. and van Weeren, P. Fixation of hydrogel constructs for cartilage repair in the equine model: a challenging issue 2017 Tissue Engineering Part C: Methods  article DOI  
Abstract: u> Objective To evaluate the use of commercial and autologous fibrin glue and of an alternative method based on a 3D-printed polycaprolactone (PCL) anchor for the fixation of hydrogel-based scaffolds in an equine model for cartilage repair. Methods In a first study, three different hydrogel-based materials were orthotopically implanted in nine horses for 1-4 weeks in 6mm diameter full thickness cartilage defects in the medial femoral trochlear ridge and fixated with commercially available fibrin glue (CFG). One defect was filled with CFG only as a control. In a second study, CFG and autologous fibrin glue (AFG) were compared in an ectopic equine model. The third study compared the efficacy of AFG and a 3D-printed PCL-based osteal anchor for fixation of PCL-reinforced hydrogels in 3 horses for 2 weeks, with a 4 week follow-up to evaluate integration of bone with the PCL anchor. Short-term scaffold integration and cell infiltration were evaluated by micro-CT and histology as outcome parameters. Results The first study showed signs of subchondral bone resorption in all defects, including the controls filled with CFG only, with significant infiltration of neutrophils. Ectopically, CFG induced clear inflammation with strong neutrophil accumulation, AFG was less reactive, showing fibroblast infiltration only. In the third study the fixation potential for PCL-reinforced hydrogels of AFG was inferior to the PCL anchor. PCL-reinforcement had disappeared from two defects and showed signs of dislodging in the remaining four. All 6 constructs fixated with the PCL anchor were still in place after 2 weeks. At 4 weeks, the PCL anchor showed good integration and signs of new bone formation. Conclusions The use of AFG should be preferred to xenogeneic products in the horse, but AFG is subject to individual variations and laborious to make. The PCL anchor provide the best fixation, however this technique involves the whole osteochondral unit, which entails a different conceptual approach to cartilage repair.
BibTeX:
@article{Mancini2017,
  author = {Mancini, Irina and Vindas Bolaños, Rafael and Brommer, Harold and Castilho, Miguel and Ribeiro, Alexandro and van Loon, Johannes and Mensinga, Anneloes and Rijen, Mattie and Malda, Jos and van Weeren, Paul},
  title = {Fixation of hydrogel constructs for cartilage repair in the equine model: a challenging issue},
  journal = {Tissue Engineering Part C: Methods},
  year = {2017},
  doi = {https://doi.org/10.1089/ten.TEC.2017.0200}
}
Cunniffe, G., Gonzalez-Fernandez, T., Daly, A., Nelson Sathy, B., Jeon, O., Alsberg, E. and J. Kelly, D. Three-Dimensional Bioprinting of Polycaprolactone Reinforced Gene Activated Bioinks for Bone Tissue Engineering 2017 Tissue Engineering Part ATissue Engineering Part A  article DOI  
Abstract: Regeneration of complex bone defects remains a significant clinical challenge. Multi-tool biofabrication has permitted the combination of various biomaterials to create multifaceted composites with tailorable mechanical properties and spatially controlled biological function. In this study we sought to use bioprinting to engineer nonviral
gene activated constructs reinforced by polymeric micro-filaments. A gene activated bioink was developed using RGD-g-irradiated alginate and nano-hydroxyapatite (nHA) complexed to plasmid DNA (pDNA). This ink was combined with bonemarrow-derived mesenchymal stemcells (MSCs) and then co-printed with a polycaprolactone supporting mesh to provide mechanical stability to the construct. Reporter genes were first used to demonstrate successful cell transfection using this system, with sustained expression of the transgene detected over 14 days postbioprinting. Delivery of a combination of therapeutic genes encoding for bone morphogenic protein and transforming growth factor promoted robust osteogenesis of encapsulated MSCs in vitro, with enhanced levels of matrix deposition and mineralization observed following the incorporation of therapeutic pDNA. Gene activated MSC-laden constructs were then implanted subcutaneously, directly postfabrication, and were found to support superior levels of vascularization andmineralization compared to cell-free controls. These results validate the use of a gene activated bioink to impart biological functionality to three-dimensional bioprinted constructs.
BibTeX:
@article{Cunniffe2017,
  author = {Cunniffe, Gráinne and Gonzalez-Fernandez, Tomas and Daly, Andrew and Nelson Sathy, Binulal and Jeon, Oju and Alsberg, Eben and J. Kelly, Daniel},
  title = {Three-Dimensional Bioprinting of Polycaprolactone Reinforced Gene Activated Bioinks for Bone Tissue Engineering},
  booktitle = {Tissue Engineering Part A},
  journal = {Tissue Engineering Part A},
  year = {2017},
  doi = {https://doi.org/10.1089/ten.tea.2016.0498}
}
Abbadessa, A., Landín, M., Oude Blenke, E., Hennink, W.E. and Vermonden, T. Two-component thermosensitive hydrogels: Phase separation affecting rheological behavior 2017 European Polymer Journal
Vol. 92(Supplement C), pp. 13-26 
article URL 
Abstract: Abstract Extracellular matrices are mainly composed of a mixture of different biopolymers and therefore the use of two or more building blocks for the development of tissue-mimicking hydrogels is nowadays an attractive strategy in tissue-engineering. Multi-component hydrogel systems may undergo phase separation, which in turn can lead to new, unexpected material properties. The aim of this study was to understand the role of phase separation on the mechanical properties and 3D printability of hydrogels composed of triblock copolymers of polyethylene glycol (PEG) and methacrylated poly(N-(2-hydroxypropyl) methacrylamide-mono/dilactate) (pHPMAlac) blended with methacrylated hyaluronic acid (HAMA). To this end, hydrogels composed of different concentrations of PEG/pHPMAlac and HAMA, were analyzed for phase behavior and rheological properties. Subsequently, phase separation and rheological behavior as function of the two polymer concentrations were mathematically processed to generate a predictive model. Results showed that PEG/pHPMAlac/HAMA hydrogels were characterized by hydrophilic, HAMA-richer internal domains dispersed in a more hydrophobic continuous phase, composed of PEG/pHPMAlac, and that the volume fraction of the dispersed phase increased by increasing HAMA concentration. Storage modulus, yield stress and viscosity increased with increasing HAMA concentration for low/medium HAMA contents (≤0.75% w/w), while a further increase of HAMA resulted in a decrease of the mentioned properties. On the other hand, by increasing the concentration of PEG/pHPMAlac these rheological properties were enhanced. The generated models showed a good fitting with experimental data, and were used to identify an exemplary 3D printability window for PEG/pHPMAlac/HAMA hydrogels, which was verified by rheological characterization and preparation of 3D printed scaffolds. In conclusion, a clear relationship between phase separation and rheological behavior in these two-component hydrogels can be described by complex functions of the two polymer concentrations. The predictive model generated in this study can be used as a valid tool for the identification of hydrogel compositions with desired, selected characteristics.
BibTeX:
@article{Abbadessa2017,
  author = {Abbadessa, Anna and Landín, Mariana and Oude Blenke, Erik and Hennink, Wim E. and Vermonden, Tina},
  title = {Two-component thermosensitive hydrogels: Phase separation affecting rheological behavior},
  journal = {European Polymer Journal},
  year = {2017},
  volume = {92},
  number = {Supplement C},
  pages = {13--26},
  url = {http://www.sciencedirect.com/science/article/pii/S0014305716317086}
}
D'Amora, U., D'Este, M., Eglin, D., Safari, F., Sprecher, C., Gloria, A., De Santis, R., Alini, M. and Ambrosio, L. Collagen Density Gradient on 3D Printed Poly(ε-Caprolactone) Scaffolds for Interface Tissue Engineering 2017 Journal of tissue engineering and regenerative medicine
Vol. 12 
article DOI  
BibTeX:
@article{DAmora2017,
  author = {D'Amora, Ugo and D'Este, Matteo and Eglin, David and Safari, Fatemeh and Sprecher, Christoph and Gloria, Antonio and De Santis, Roberto and Alini, Mauro and Ambrosio, Luigi},
  title = {Collagen Density Gradient on 3D Printed Poly(ε-Caprolactone) Scaffolds for Interface Tissue Engineering},
  journal = {Journal of tissue engineering and regenerative medicine},
  year = {2017},
  volume = {12},
  doi = {https://doi.org/10.1002/term.2457}
}
Bastola, A.K., Hoang, V.T. and Li, L. A novel hybrid magnetorheological elastomer developed by 3D printing 2017 Materials & Design
Vol. 114(Supplement C), pp. 391-397 
article URL 
Abstract: Abstract In this study, a novel magnetorheological (MR) hybrid elastomer has been developed using a 3D printing method. In such an MR hybrid elastomer, a controlled volume of an MR fluid was encapsulated layer by layer into an elastomer matrix by means of a 3D printer and each layer was a composite structure consisting of an MR fluid and an elastomer. Similar to current MR fluids and MR elastomers, mechanical properties of 3D printed MR hybrid elastomers could be controlled via an externally applied magnetic field. The experimental results showed that the relative change in the damping capability of the new MR elastomer was more pronounced than the change in its stiffness when exposed to an external magnetic field. The study demonstrated that the 3D printing technique is feasible for fabrication of MR elastomers with controlled microstructures including magnetic particles or MR fluids. The 3D printed MR hybrid elastomer is also a potential material as a tunable spring-damper element.
BibTeX:
@article{Bastola2017,
  author = {Bastola, A. K. and Hoang, V. T. and Li, L.},
  title = {A novel hybrid magnetorheological elastomer developed by 3D printing},
  journal = {Materials & Design},
  year = {2017},
  volume = {114},
  number = {Supplement C},
  pages = {391--397},
  url = {http://www.sciencedirect.com/science/article/pii/S0264127516313922}
}
Zeng, Q., Macri, L., Prasad, A., Clark, R., Zeugolis, D., Hanley, C., Garcia, Y., Pandit, A., Leavesley, D., Stupar, D., Fernandez, M., Fan, C. and Upton, Z. 6.20 Skin Tissue Engineering☆ 2017 Comprehensive Biomaterials II\, pp. 334 - 382  incollection DOI URL 
Abstract: Abstract The integration of healing, cell biology, and skin tissue engineering research has been ongoing for nearly one century. In this chapter, we provide a bird’s eye view of skin anatomy and functions, wound healing processes, the challenges and solutions to wound healing. Many techniques and biomaterials have been examined for their potential utility as skin substitutes. Notwithstanding evidence that some strategies have been more successful than others, the ideal skin substitute does not exist. Existing skin substitutes suffer from poor mechanical properties, poor biocompatibility, poor immunocompatibility, poor integration, limited vascularization (poor survival), and fibrosis (scarring). However, the results from collaborative efforts between skin biologists, materials engineers and surgeons is providing transforming advances in this field and is delivering improvements for skin repair and regeneration. The combination of stem cells, vascularization, smart materials and customized bioprinting means that authentic skin substitutes that support skin regeneration are visible on the horizon.
BibTeX:
@incollection{Zeng2017,
  author = {Q. Zeng and L.K. Macri and A. Prasad and R.A.F. Clark and D.I. Zeugolis and C. Hanley and Y. Garcia and A. Pandit and D.I. Leavesley and D. Stupar and M.L. Fernandez and C. Fan and Z. Upton},
  title = {6.20 Skin Tissue Engineering☆},
  booktitle = {Comprehensive Biomaterials II\},
  publisher = {Elsevier},
  year = {2017},
  pages = {334 - 382},
  url = {https://www.sciencedirect.com/science/article/pii/B9780128035818101572},
  doi = {https://doi.org/10.1016/B978-0-12-803581-8.10157-2}
}
Thamm, C., DeSimone, E. and Scheibel, T. Characterization of Hydrogels Made of a Novel Spider Silk Protein eMaSp1s and Evaluation for 3D Printing 2017 Macromolecular Bioscience
Vol. 17(11), pp. 1700141-n/a 
article DOI URL 
Abstract: Recombinantly produced spider silk proteins have high potential for bioengineering and various biomedical applications because of their biocompatibility, biodegradability, and low immunogenicity. Here, the recently described small spider silk protein eMaSp1s is assembled into hydrogels, which can be 3D printed into scaffolds. Further, blending with a recombinantly produced MaSp2 derivative eADF4(C16) alters the mechanical properties of the resulting hydrogels. Different spider silk hydrogels also show a distinct recovery after a high shear stress deformation, exhibiting the tunability of their features for selected applications.
BibTeX:
@article{Thamm2017,
  author = {Thamm, Christopher and DeSimone, Elise and Scheibel, Thomas},
  title = {Characterization of Hydrogels Made of a Novel Spider Silk Protein eMaSp1s and Evaluation for 3D Printing},
  journal = {Macromolecular Bioscience},
  year = {2017},
  volume = {17},
  number = {11},
  pages = {1700141--n/a},
  note = {1700141},
  url = {http://dx.doi.org/10.1002/mabi.201700141},
  doi = {https://doi.org/10.1002/mabi.201700141}
}
Sultan, S., Siqueira, G., Zimmermann, T. and Mathew, A.P. 3D printing of nano-cellulosic biomaterials for medical applications 2017 Current Opinion in Biomedical Engineering
Vol. 2(Supplement C), pp. 29 - 34 
article DOI URL 
Abstract: Abstract Nanoscaled versions of cellulose viz. cellulose nanofibers (CNF) or cellulose nanocrystals (CNC) isolated from natural resources are being used extensively since the past decade in the biomedical field e.g. for tissue engineering, implants, drug delivery systems, cardiovascular devices, and wound healing due to their remarkable mechanical, chemical and biocompatible properties. In the recent years, 3D printing of nanocellulose in combination with polymers is being studied as a viable route to future regenerative therapy. The printability of nanocellulose hydrogels owing to their shear thinning behavior and the possibility to support living cells allows 3D bioprinting using nanocellulose, a recent development which holds tremendous potential.
BibTeX:
@article{Sultan2017,
  author = {Sahar Sultan and Gilberto Siqueira and Tanja Zimmermann and Aji P. Mathew},
  title = {3D printing of nano-cellulosic biomaterials for medical applications},
  journal = {Current Opinion in Biomedical Engineering},
  year = {2017},
  volume = {2},
  number = {Supplement C},
  pages = {29 - 34},
  note = {Additive Manufacturing},
  url = {http://www.sciencedirect.com/science/article/pii/S2468451117300132},
  doi = {https://doi.org/10.1016/j.cobme.2017.06.002}
}
Stichler, S., Böck, T., Paxton, N.C., Bertlein, S., Levato, R., Schill, V., Smolan, W., Malda, J., Tessmar, J., Blunk, T. and Groll, J. Double printing of hyaluronic acid / poly(glycidol) hybrid hydrogels with poly(ε-caprolactone) for MSC chondrogenesis 2017 Biofabrication  article DOI  
Abstract: Abstract This study investigates the use of allyl-functionalized poly(glycidol)s (P(AGE-co-G)) as cytocompatible cross-linker for thiol-functionalized hyaluronic acid (HA-SH) and the optimization of this hybrid hydrogel as bioink for 3D bioprinting. Chemical cross-linking of gels with 10 wt.% overall polymer concentration was achieved by UV-induced radical thiol-ene coupling between the thiol and allyl groups. Addition of unmodified high molecular weight HA (1.36 MDa) allowed tuning of the rheology for extrusion based bioprinting. Incorporation of additional HA resulted in hydrogels with lower Young’s modulus and higher swelling ratio especially in the first 24 h, but a comparable equilibrium swelling for all gels after 24 h. Embedding of human and equine mesenchymal stem cells (MSCs) in the gels and subsequent in vitro culture showed promising chondrogenic differentiation after 21 d for cells from both origins. Moreover, cells could be printed with these gels, and embedded hMSCs showed good cell survival for at least 21 d in culture. To achieve mechanical stable and robust constructs for the envisioned application in articular cartilage, the formulations were adjusted for double printing with the thermoplastic poly--caprolactone (PCL).
BibTeX:
@article{Stichler2017,
  author = {Simone Stichler and Thomas Böck and Naomi Claire Paxton and Sarah Bertlein and Riccardo Levato and Verena Schill and Willi Smolan and Jos Malda and Joerg Tessmar and Torsten Blunk and Juergen Groll},
  title = {Double printing of hyaluronic acid / poly(glycidol) hybrid hydrogels with poly(ε-caprolactone) for MSC chondrogenesis},
  journal = {Biofabrication},
  year = {2017},
  doi = {https://doi.org/10.1088/1758-5090/aa8cb7}
}
Sommer, M.R., Alison, L., Minas, C., Tervoort, E., Ruhs, P.A. and Studart, A.R. 3D printing of concentrated emulsions into multiphase biocompatible soft materials 2017 Soft Matter
Vol. 13, pp. 1794-1803 
article DOI  
Abstract: 3D printing via direct ink writing (DIW) is a versatile additive manufacturing approach applicable to a variety of materials ranging from ceramics over composites to hydrogels. Due to the mild processing conditions compared to other additive manufacturing methods, DIW enables the incorporation of sensitive compounds such as proteins or drugs into the printed structure. Although emulsified oil-in-water systems are commonly used vehicles for such compounds in biomedical, pharmaceutical, and cosmetic applications, printing of such emulsions into architectured soft materials has not been fully exploited and would open new possibilities for the controlled delivery of sensitive compounds. Here, we 3D print concentrated emulsions into soft materials, whose multiphase architecture allows for site-specific incorporation of both hydrophobic and hydrophilic compounds into the same structure. As a model ink, concentrated emulsions stabilized by chitosan-modified silica nanoparticles are studied, because they are sufficiently stable against coalescence during the centrifugation step needed to create a bridging network of droplets. The resulting ink is ideal for 3D printing as it displays high yield stress, storage modulus and elastic recovery, through the formation of networks of droplets as well as of gelled silica nanoparticles in the presence of chitosan. To demonstrate possible architectures, we print biocompatible soft materials with tunable hierarchical porosity containing an encapsulated hydrophobic compound positioned in specific locations of the structure. The proposed emulsion-based ink system offers great flexibility in terms of 3D shaping and local compositional control, and can potentially help address current challenges involving the delivery of incompatible compounds in biomedical applications.
BibTeX:
@article{Sommer2017,
  author = {Sommer, Marianne R. and Alison, Lauriane and Minas, Clara and Tervoort, Elena and Ruhs, Patrick A. and Studart, Andre R.},
  title = {3D printing of concentrated emulsions into multiphase biocompatible soft materials},
  journal = {Soft Matter},
  publisher = {The Royal Society of Chemistry},
  year = {2017},
  volume = {13},
  pages = {1794-1803},
  doi = {https://doi.org/10.1039/C6SM02682F}
}
Siqueira, G., Kokkinis, D., Libanori, R., Hausmann, M.K., Gladman, A.S., Neels, A., Tingaut, P., Zimmermann, T., Lewis, J.A. and Studart, A.R. Cellulose Nanocrystal Inks for 3D Printing of Textured Cellular Architectures 2017 Advanced Functional Materials
Vol. 27(12), pp. 1604619-n/a 
article DOI  
Abstract: 3D printing of renewable building blocks like cellulose nanocrystals offers an attractive pathway for fabricating sustainable structures. Here, viscoelastic inks composed of anisotropic cellulose nanocrystals (CNC) that enable patterning of 3D objects by direct ink writing are designed and formulated. These concentrated inks are composed of CNC particles suspended in either water or a photopolymerizable monomer solution. The shear-induced alignment of these anisotropic building blocks during printing is quantified by atomic force microscopy, polarized light microscopy, and 2D wide-angle X-ray scattering measurements. Akin to the microreinforcing effect in plant cell walls, the alignment of CNC particles during direct writing yields textured composites with enhanced stiffness along the printing direction. The observations serve as an important step forward toward the development of sustainable materials for 3D printing of cellular architectures with tailored mechanical properties.
BibTeX:
@article{Siqueira2017,
  author = {Siqueira, Gilberto and Kokkinis, Dimitri and Libanori, Rafael and Hausmann, Michael K. and Gladman, Amelia Sydney and Neels, Antonia and Tingaut, Philippe and Zimmermann, Tanja and Lewis, Jennifer A. and Studart, André R.},
  title = {Cellulose Nanocrystal Inks for 3D Printing of Textured Cellular Architectures},
  journal = {Advanced Functional Materials},
  year = {2017},
  volume = {27},
  number = {12},
  pages = {1604619--n/a},
  note = {1604619},
  doi = {https://doi.org/10.1002/adfm.201604619}
}
Schaffner, M., Rühs, P.A., Coulter, F., Kilcher, S. and Studart, A.R. 3D printing of bacteria into functional complex materials 2017 Science Advances
Vol. 3(12) 
article DOI URL 
Abstract: Despite recent advances to control the spatial composition and dynamic functionalities of bacteria embedded in materials, bacterial localization into complex three-dimensional (3D) geometries remains a major challenge. We demonstrate a 3D printing approach to create bacteria-derived functional materials by combining the natural diverse metabolism of bacteria with the shape design freedom of additive manufacturing. To achieve this, we embedded bacteria in a biocompatible and functionalized 3D printing ink and printed two types of “living materials” capable of degrading pollutants and of producing medically relevant bacterial cellulose. With this versatile bacteria-printing platform, complex materials displaying spatially specific compositions, geometry, and properties not accessed by standard technologies can be assembled from bottom up for new biotechnological and biomedical applications.
BibTeX:
@article{Schaffner2017,
  author = {Schaffner, Manuel and Rühs, Patrick A. and Coulter, Fergal and Kilcher, Samuel and Studart, André R.},
  title = {3D printing of bacteria into functional complex materials},
  journal = {Science Advances},
  publisher = {American Association for the Advancement of Science},
  year = {2017},
  volume = {3},
  number = {12},
  url = {http://advances.sciencemag.org/content/3/12/eaao6804},
  doi = {https://doi.org/10.1126/sciadv.aao6804}
}
Ribeiro, A., Blokzijl, M.M., Levato, R., Visser, C.W., Castilho, M., Hennink, W.E., Vermonden, T. and Malda, J. Assessing bioink shape fidelity to aid material development in 3D bioprinting 2017 Biofabrication  article DOI  
Abstract: Abstract During extrusion-based bioprinting, the deposited bioink filaments are subjected to deformations, such as collapse of overhanging filaments, which compromises the ability to stack several layers of bioink, and fusion between adjacent filaments, which compromises the resolution and maintenance of a desired pore structure. When developing new bioinks, approaches to assess their shape fidelity after printing would be beneficial to evaluate the degree of deformation of the deposited filament and to estimate how similar the final printed construct would be to the design. However, shape fidelity has been prevalently assessed qualitatively through visual inspection after printing, hampering the direct comparison of the printability of different bioinks. In this technical note, we propose a quantitative evaluation for shape fidelity of bioinks based on testing the filament collapse on overhanging structures and the filament fusion of parallel printed strands. Both tests were applied on a hydrogel platform based on poloxamer 407 and poly(ethylene glycol) (PEG) blends, providing a library of hydrogels with different yield stresses. The presented approach is an easy way to assess bioink shape fidelity, applicable to any filament-based bioprinting system and able to quantitatively evaluate this aspect of printability , based on the degree of deformation of the printed filament. In addition, we built a simple theoretical model that relates filament collapse with bioink yield stress. The results of both shape fidelity tests underline the role of yield stress as one of the parameters influencing the printability of a bioink. The presented quantitative evaluation will allow for reproducible comparisons between different bioink platforms.
BibTeX:
@article{Ribeiro2017,
  author = {Alexandre Ribeiro and Maarten Michiel Blokzijl and Riccardo Levato and Claas Willem Visser and Miguel Castilho and Wim E Hennink and Tina Vermonden and Jos Malda},
  title = {Assessing bioink shape fidelity to aid material development in 3D bioprinting},
  journal = {Biofabrication},
  year = {2017},
  doi = {https://doi.org/10.1088/1758-5090/aa90e2}
}
Reitmaier, S., Kovtun, A., Schuelke, J., Kanter, B., Lemm, M., Hoess, A., Heinemann, S., Nies, B. and Ignatius, A. Strontium(II) and mechanical loading additively augment bone formation in calcium phosphate scaffolds 2017 Journal of Orthopaedic Research, pp. n/a-n/a  article DOI  
Abstract:
Calcium phosphate cements (CPCs) are widely used for bone-defect treatment. Current developments comprise the fabrication of porous scaffolds by three-dimensional plotting and doting using biologically active substances, such as strontium. Strontium is known to increase osteoblast activity and simultaneously to decrease osteoclast resorption. This study investigated the short- and long-term in vivo performances of strontium(II)-doted CPC (SrCPC) scaffolds compared to non-doted CPC scaffolds after implantation in unloaded or load-bearing trabecular bone defects in sheep. After 6 weeks, both CPC and SrCPC scaffolds exhibited good biocompatibility and osseointegration. Fluorochrome labeling revealed that both scaffolds were penetrated by newly formed bone already after 4 weeks. Neither strontium doting nor mechanical loading significantly influenced early bone formation. In contrast, after 6 months, bone formation was significantly enhanced in SrCPC compared to CPC scaffolds. Energy dispersive X-ray analysis demonstrated the release of strontium from the SrCPC into the bone. Strontium addition did not significantly influence material resorption or osteoclast formation. Mechanical loading significantly stimulated bone formation in both CPC and SrCPC scaffolds after 6 months without impairing scaffold integrity. The most bone was found in SrCPC scaffolds under load-bearing conditions. Concluding, these results demonstrate that strontium doting and mechanical loading additively stimulated bone formation in CPC scaffolds and that the scaffolds exhibited mechanical stability under moderate load, implying good clinical suitability. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res
BibTeX:
@article{Reitmaier2017,
  author = {Reitmaier, Sandra and Kovtun, Anna and Schuelke, Julian and Kanter, Britta and Lemm, Madlin and Hoess, Andreas and Heinemann, Sascha and Nies, Berthold and Ignatius, Anita},
  title = {Strontium(II) and mechanical loading additively augment bone formation in calcium phosphate scaffolds},
  journal = {Journal of Orthopaedic Research},
  year = {2017},
  pages = {n/a--n/a},
  doi = {https://doi.org/10.1002/jor.23623}
}
Peng, W., Datta, P., Ayan, B., Ozbolat, V., Sosnoski, D. and Ozbolat, I.T. 3D bioprinting for drug discovery and development in pharmaceutics 2017 Acta Biomaterialia
Vol. 57, pp. 26 - 46 
article DOI URL 
Abstract: Successful launch of a commercial drug requires significant investment of time and financial resources wherein late-stage failures become a reason for catastrophic failures in drug discovery. This calls for infusing constant innovations in technologies, which can give reliable prediction of efficacy, and more importantly, toxicology of the compound early in the drug discovery process before clinical trials. Though computational advances have resulted in more rationale in silico designing, in vitro experimental studies still require gaining industry confidence and improving in vitro-in vivo correlations. In this quest, due to their ability to mimic the spatial and chemical attributes of native tissues, three-dimensional (3D) tissue models have now proven to provide better results for drug screening compared to traditional two-dimensional (2D) models. However, in vitro fabrication of living tissues has remained a bottleneck in realizing the full potential of 3D models. Recent advances in bioprinting provide a valuable tool to fabricate biomimetic constructs, which can be applied in different stages of drug discovery research. This paper presents the first comprehensive review of bioprinting techniques applied for fabrication of 3D tissue models for pharmaceutical studies. A comparative evaluation of different bioprinting modalities is performed to assess the performance and ability of fabricating 3D tissue models for pharmaceutical use as the critical selection of bioprinting modalities indeed plays a crucial role in efficacy and toxicology testing of drugs and accelerates the drug development cycle. In addition, limitations with current tissue models are discussed thoroughly and future prospects of the role of bioprinting in pharmaceutics are provided to the reader. Present advances in tissue biofabrication have crucial role to play in aiding the pharmaceutical development process achieve its objectives. Advent of three-dimensional (3D) models, in particular, is viewed with immense interest by the community due to their ability to mimic in vivo hierarchical tissue architecture and heterogeneous composition. Successful realization of 3D models will not only provide greater in vitro-in vivo correlation compared to the two-dimensional (2D) models, but also eventually replace pre-clinical animal testing, which has their own shortcomings. Amongst all fabrication techniques, bioprinting- comprising all the different modalities (extrusion-, droplet- and laser-based bioprinting), is emerging as the most viable fabrication technique to create the biomimetic tissue constructs. Notwithstanding the interest in bioprinting by the pharmaceutical development researchers, it can be seen that there is a limited availability of comparative literature which can guide the proper selection of bioprinting processes and associated considerations, such as the bioink selection for a particular pharmaceutical study. Thus, this work emphasizes these aspects of bioprinting and presents them in perspective of differential requirements of different pharmaceutical studies like in vitro predictive toxicology, high-throughput screening, drug delivery and tissue-specific efficacies. Moreover, since bioprinting techniques are mostly applied in regenerative medicine and tissue engineering, a comparative analysis of similarities and differences are also expounded to help researchers make informed decisions based on contemporary literature.
BibTeX:
@article{Peng2017,
  author = {Weijie Peng and Pallab Datta and Bugra Ayan and Veli Ozbolat and Donna Sosnoski and Ibrahim T. Ozbolat},
  title = {3D bioprinting for drug discovery and development in pharmaceutics},
  journal = {Acta Biomaterialia},
  year = {2017},
  volume = {57},
  pages = {26 - 46},
  url = {http://www.sciencedirect.com/science/article/pii/S1742706117303069},
  doi = {https://doi.org/10.1016/j.actbio.2017.05.025}
}
Paxton, N.C., Smolan, W., Böck, T., Melchels, F.P.W., Groll, J. and Juengst, T. Proposal to Assess Printability of Bioinks for Extrusion-Based Bioprinting and Evaluation of Rheological Properties Governing Bioprintability 2017 Biofabrication  article DOI  
Abstract: Abstract The development and formulation of printable inks for extrusion-based 3D bioprinting has been a major challenge in the field of biofabrication. Inks, often polymer solutions with the addition of crosslinking to form hydrogels, must not only display adequate mechanical properties for the chosen application, but also show high biocompatibility as well as printability. Here we describe a reproducible two-step method for the assessment of the printability of inks for bioprinting, focussing firstly on screening ink formulations to assess fibre formation and the ability to form 3D constructs before presenting a method for the rheological evaluation of inks to characterise the yield point, shear thinning and recovery behaviour. In conjunction, a mathematical model was formulated to provide a theoretical understanding of the pressure-driven, shear thinning extrusion of inks through needles in a bioprinter. The assessment methods were trialled with a commercially-available crème, poloxamer 407, alginate-based inks and an alginate-gelatin composite material. Yield stress was investigated by applying a stress ramp to a number of inks, which demonstrated the necessity of high yield for printable materials. The shear thinning behaviour of the inks was then characterised by quantifying the degree of shear thinning and using the mathematical model to predict the window of printer operating parameters in which the materials could be printed. Furthermore, the model predicted high shear conditions and high residence times for cells at the walls of the needle and effects on cytocompatibility at different printing conditions. Finally, the ability of the materials to recover to their original viscosity after extrusion was examined using rotational recovery rheological measurements. Taken together, these assessment techniques revealed significant insights into the requirements for printable inks and shear conditions present during the extrusion process and allow the rapid and reproducible characterisation of a wide variety of inks for bioprinting.
BibTeX:
@article{Paxton2017,
  author = {Naomi Claire Paxton and Willi Smolan and Thomas Böck and Ferry P W Melchels and Juergen Groll and Tomasz Juengst},
  title = {Proposal to Assess Printability of Bioinks for Extrusion-Based Bioprinting and Evaluation of Rheological Properties Governing Bioprintability},
  journal = {Biofabrication},
  year = {2017},
  doi = {https://doi.org/10.1088/1758-5090/aa8dd8}
}
Mouser, V.H.M., Abbadessa, A., Levato, R., Hennink, W.E., Vermonden, T., Gawlitta, D. and Malda, J. Development of a thermosensitive HAMA-containing bio-ink for the fabrication of composite cartilage repair constructs 2017 Biofabrication
Vol. 9(1), pp. 015026 
article URL 
Abstract: Fine-tuning of bio-ink composition and material processing parameters is crucial for the development of biomechanically relevant cartilage constructs. This study aims to design and develop cartilage constructs with tunable internal architectures and relevant mechanical properties. More specifically, the potential of methacrylated hyaluronic acid (HAMA) added to thermosensitive hydrogels composed of methacrylated poly[ N -(2-hydroxypropyl)methacrylamide mono/dilactate] (pHPMA-lac)/polyethylene glycol (PEG) triblock copolymers, to optimize cartilage-like tissue formation by embedded chondrocytes, and enhance printability was explored. Additionally, co-printing with polycaprolactone (PCL) was performed for mechanical reinforcement. Chondrocyte-laden hydrogels composed of pHPMA-lac-PEG and different concentrations of HAMA (0%–1% w/w) were cultured for 28 d in vitro and subsequently evaluated for the presence of cartilage-like matrix. Young’s moduli were determined for hydrogels with the different HAMA concentrations. Additionally, hydrogel/PCL constructs with different internal architectures were co-printed and analyzed for their mechanical properties. The results of this study demonstrated a dose-dependent effect of HAMA concentration on cartilage matrix synthesis by chondrocytes. Glycosaminoglycan (GAG) and collagen type II content increased with intermediate HAMA concentrations (0.25%–0.5%) compared to HAMA-free controls, while a relatively high HAMA concentration (1%) resulted in increased fibrocartilage formation. Young’s moduli of generated hydrogel constructs ranged from 14 to 31 kPa and increased with increasing HAMA concentration. The pHPMA-lac-PEG hydrogels with 0.5% HAMA were found to be optimal for cartilage-like tissue formation. Therefore, this hydrogel system was co-printed with PCL to generate porous or solid constructs with different mesh sizes. Young’s moduli of these composite constructs were in the range of native cartilage (3.5–4.6 MPa). Interestingly, the co-printing procedure influenced the mechanical properties of the final constructs. These findings are relevant for future bio-ink development, as they demonstrate the importance of selecting proper HAMA concentrations, as well as appropriate print settings and construct designs for optimal cartilage matrix deposition and final mechanical properties of constructs, respectively.
BibTeX:
@article{Mouser2017,
  author = {V H M Mouser and A Abbadessa and R Levato and W E Hennink and T Vermonden and D Gawlitta and J Malda},
  title = {Development of a thermosensitive HAMA-containing bio-ink for the fabrication of composite cartilage repair constructs},
  journal = {Biofabrication},
  year = {2017},
  volume = {9},
  number = {1},
  pages = {015026},
  url = {http://stacks.iop.org/1758-5090/9/i=1/a=015026}
}
Lorson, T., Jaksch, S., Lübtow, M.M., Jüngst, T., Groll, J., Lühmann, T. and Luxenhofer, R. A Thermogelling Supramolecular Hydrogel with Sponge-Like Morphology as a Cytocompatible Bioink 2017 Biomacromolecules
Vol. 18(7), pp. 2161-2171 
article DOI  
Abstract: Biocompatible polymers that form thermoreversible supramolecular hydrogels have gained great interest in biomaterials research and tissue engineering. When favorable rheological properties are achieved at the same time, they are particularly promising candidates as material that allow for the printing of cells, so-called bioinks. We synthesized a novel thermogelling block copolymer and investigated the rheological properties of its aqueous solution by viscosimetry and rheology. The polymers undergo thermogelation between room temperature and body temperature, form transparent hydrogels of surprisingly high strength (G′ > 1000 Pa) and show rapid and complete shear recovery after stress. Small angle neutron scattering suggests an unusual bicontinuous sponge-like gel network. Excellent cytocompatibility was demonstrated with NIH 3T3 fibroblasts, which were incorporated and bioplotted into predefined 3D hydrogel structures without significant loss of viability. The developed materials fulfill all criteria for future use as bioink for biofabrication.
BibTeX:
@article{Lorson2017,
  author = {Lorson, Thomas and Jaksch, Sebastian and Lübtow, Michael M. and Jüngst, Tomasz and Groll, Jürgen and Lühmann, Tessa and Luxenhofer, Robert},
  title = {A Thermogelling Supramolecular Hydrogel with Sponge-Like Morphology as a Cytocompatible Bioink},
  journal = {Biomacromolecules},
  year = {2017},
  volume = {18},
  number = {7},
  pages = {2161-2171},
  note = {PMID: 28653854},
  doi = {https://doi.org/10.1021/acs.biomac.7b00481}
}
Ligon, S.C., Liska, R., Stampfl, J., Gurr, M. and Mülhaupt, R. Polymers for 3D Printing and Customized Additive Manufacturing 2017 Chemical Reviews
Vol. 117(15), pp. 10212-10290 
article DOI  
Abstract: Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting. The range of polymers used in AM encompasses thermoplastics, thermosets, elastomers, hydrogels, functional polymers, polymer blends, composites, and biological systems. Aspects of polymer design, additives, and processing parameters as they relate to enhancing build speed and improving accuracy, functionality, surface finish, stability, mechanical properties, and porosity are addressed. Selected applications demonstrate how polymer-based AM is being exploited in lightweight engineering, architecture, food processing, optics, energy technology, dentistry, drug delivery, and personalized medicine. Unparalleled by metals and ceramics, polymer-based AM plays a key role in the emerging AM of advanced multifunctional and multimaterial systems including living biological systems as well as life-like synthetic systems.
BibTeX:
@article{Ligon2017,
  author = {Ligon, Samuel Clark and Liska, Robert and Stampfl, Jürgen and Gurr, Matthias and Mülhaupt, Rolf},
  title = {Polymers for 3D Printing and Customized Additive Manufacturing},
  journal = {Chemical Reviews},
  year = {2017},
  volume = {117},
  number = {15},
  pages = {10212-10290},
  note = {PMID: 28756658},
  doi = {https://doi.org/10.1021/acs.chemrev.7b00074}
}
Liao, Z., Sinjab, F., Nommeots-Nomm, A., Jones, J., Ruiz-Cantu, L., Yang, J., Rose, F. and Notingher, I. Feasibility of Spatially Offset Raman Spectroscopy for in Vitro and in Vivo Monitoring Mineralization of Bone Tissue Engineering Scaffolds 2017 Analytical Chemistry
Vol. 89(1), pp. 847-853 
article DOI  
Abstract: We investigated the feasibility of using spatially offset Raman spectroscopy (SORS) for nondestructive characterization of bone tissue engineering scaffolds. The deep regions of these scaffolds, or scaffolds implanted subcutaneously in live animals, are typically difficult to measure by confocal Raman spectroscopy techniques because of the limited depth penetration of light caused by the high level of light scattering. Layered samples consisting of bioactive glass foams (IEIC16), three-dimensional (3D)-printed biodegradable poly(lactic-co-glycolic acid) scaffolds (PLGA), and hydroxyapatite powder (HA) were used to mimic nondestructive detection of biomineralization for intact real-size 3D tissue engineering constructs. SORS spectra were measured with a new SORS instrument using a digital micromirror device (DMD) to allow software selection of the spatial offsets. The results show that HA can be reliably detected at depths of 0–2.3 mm, which corresponds to the maximum accessible spatial offset of the current instrument. The intensity ratio of Raman bands associated with the scaffolds and HA with the spatial offset depended on the depth at which HA was located. Furthermore, we show the feasibility for in vivo monitoring mineralization of scaffold implanted subcutaneously by demonstrating the ability to measure transcutaneously Raman signals of the scaffolds and HA (fresh chicken skin used as a top layer). The ability to measure spectral depth profiles at high speed (5 s acquisition time) and the ease of implementation make SORS a promising approach for noninvasive characterization of cell/tissue development in vitro, and for long-term in vivo monitoring the mineralization in 3D scaffolds subcutaneously implanted in small animals.
BibTeX:
@article{Liao2017,
  author = {Liao, Zhiyu and Sinjab, Faris and Nommeots-Nomm, Amy and Jones, Julian and Ruiz-Cantu, Laura and Yang, Jing and Rose, Felicity and Notingher, Ioan},
  title = {Feasibility of Spatially Offset Raman Spectroscopy for in Vitro and in Vivo Monitoring Mineralization of Bone Tissue Engineering Scaffolds},
  journal = {Analytical Chemistry},
  year = {2017},
  volume = {89},
  number = {1},
  pages = {847-853},
  note = {PMID: 27983789},
  doi = {https://doi.org/10.1021/acs.analchem.6b03785}
}
Kuzmenko, V. Cellulose-derived conductive nanofibrous materials for energy storage and tissue engineering Applications 2017 School: Department of Microtechnology and Nanoscience CHALMERS UNIVERSITY OF TECHNOLOGY  phdthesis URL 
BibTeX:
@phdthesis{Kuzmenko2017,
  author = {Kuzmenko, Volodymyr},
  title = {Cellulose-derived conductive nanofibrous materials for energy storage and tissue engineering Applications},
  school = {Department of Microtechnology and Nanoscience CHALMERS UNIVERSITY OF TECHNOLOGY},
  year = {2017},
  url = {http://publications.lib.chalmers.se/publication/248980-cellulose-derived-conductive-nanofibrous-materials-for-energy-storage-and-tissue-engineering-applica}
}
Huang, Y., Zhang, X.-F., Gao, G., Yonezawa, T. and Cui, X. 3D bioprinting and the current applications in tissue engineering 2017 Biotechnology Journal
Vol. 12(8), pp. 1600734-n/a 
article DOI  
Abstract: Bioprinting as an enabling technology for tissue engineering possesses the promises to fabricate highly mimicked tissue or organs with digital control. As one of the biofabrication approaches, bioprinting has the advantages of high throughput and precise control of both scaffold and cells. Therefore, this technology is not only ideal for translational medicine but also for basic research applications. Bioprinting has already been widely applied to construct functional tissues such as vasculature, muscle, cartilage, and bone. In this review, the authors introduce the most popular techniques currently applied in bioprinting, as well as the various bioprinting processes. In addition, the composition of bioink including scaffolds and cells are described. Furthermore, the most current applications in organ and tissue bioprinting are introduced. The authors also discuss the challenges we are currently facing and the great potential of bioprinting. This technology has the capacity not only in complex tissue structure fabrication based on the converted medical images, but also as an efficient tool for drug discovery and preclinical testing. One of the most promising future advances of bioprinting is to develop a standard medical device with the capacity of treating patients directly on the repairing site, which requires the development of automation and robotic technology, as well as our further understanding of biomaterials and stem cell biology to integrate various printing mechanisms for multi-phasic tissue engineering.
BibTeX:
@article{Huang2017,
  author = {Huang, Ying and Zhang, Xiao-Fei and Gao, Guifang and Yonezawa, Tomo and Cui, Xiaofeng},
  title = {3D bioprinting and the current applications in tissue engineering},
  journal = {Biotechnology Journal},
  publisher = {WILEY-VCH Verlag},
  year = {2017},
  volume = {12},
  number = {8},
  pages = {1600734--n/a},
  note = {1600734},
  doi = {https://doi.org/10.1002/biot.201600734}
}
Henriksson, I., Gatenholm, P. and Hägg, D.A. Increased lipid accumulation and adipogenic gene expression of adipocytes in 3D bioprinted nanocellulose scaffolds 2017 Biofabrication
Vol. 9(1), pp. 015022 
article URL 
Abstract: Compared to standard 2D culture systems, new methods for 3D cell culture of adipocytes could provide more physiologically accurate data and a deeper understanding of metabolic diseases such as diabetes. By resuspending living cells in a bioink of nanocellulose and hyaluronic acid, we were able to print 3D scaffolds with uniform cell distribution. After one week in culture, cell viability was 95%, and after two weeks the cells displayed a more mature phenotype with larger lipid droplets than standard 2D cultured cells. Unlike cells in 2D culture, the 3D bioprinted cells did not detach upon lipid accumulation. After two weeks, the gene expression of the adipogenic marker genes PPAR γ and FABP4 was increased 2.0- and 2.2-fold, respectively, for cells in 3D bioprinted constructs compared with 2D cultured cells. Our 3D bioprinted culture system produces better adipogenic differentiation of mesenchymal stem cells and a more mature cell phenotype than conventional 2D culture systems.
BibTeX:
@article{Henriksson2017,
  author = {I Henriksson and P Gatenholm and D A Hägg},
  title = {Increased lipid accumulation and adipogenic gene expression of adipocytes in 3D bioprinted nanocellulose scaffolds},
  journal = {Biofabrication},
  year = {2017},
  volume = {9},
  number = {1},
  pages = {015022},
  url = {http://stacks.iop.org/1758-5090/9/i=1/a=015022}
}
DeSimone, E., Schacht, K., Pellert, A. and Scheibel, T. Recombinant spider silk-based bioinks 2017 Biofabrication
Vol. 9(4), pp. 044104 
article URL 
Abstract: Bioinks, 3D cell culture systems which can be printed, are still in the early development stages. Currently, extensive research is going into designing printers to be more accommodating to bioinks, designing scaffolds with stiff materials as support structures for the often soft bioinks, and modifying the bioinks themselves. Recombinant spider silk proteins, a potential biomaterial component for bioinks, have high biocompatibility, can be processed into several morphologies and can be modified with cell adhesion motifs to enhance their bioactivity. In this work, thermally gelled hydrogels made from recombinant spider silk protein encapsulating mouse fibroblast cell line BALB/3T3 were prepared and characterized. The bioinks were evaluated for performance in vitro both before and after printing, and it was observed that unprinted bioinks provided a good platform for cell spreading and proliferation, while proliferation in printed scaffolds was prohibited. To improve the properties of the printed hydrogels, gelatin was given as an additive and thereby served indirectly as a plasticizer, improving the resolution of printed strands. Taken together, recombinant spider silk proteins and hydrogels made thereof show good potential as a bioink, warranting further development.
BibTeX:
@article{DeSimone2017,
  author = {Elise DeSimone and Kristin Schacht and Alexandra Pellert and Thomas Scheibel},
  title = {Recombinant spider silk-based bioinks},
  journal = {Biofabrication},
  year = {2017},
  volume = {9},
  number = {4},
  pages = {044104},
  url = {http://stacks.iop.org/1758-5090/9/i=4/a=044104}
}
Dalton, P.D. Melt electrowriting with additive manufacturing principles 2017 Current Opinion in Biomedical Engineering
Vol. 2(Supplement C), pp. 49 - 57 
article DOI URL 
Abstract: Abstract The recent development of electrostatic writing (electrowriting) with molten jets provides an opportunity to tackle some significant challenges within tissue engineering. The process uses an applied voltage to generate a stable fluid jet with a predictable path, that is continuously deposited onto a collector. The fiber diameter is variable during the process, and is applicable to polymers with a history of clinical use. Melt electrowriting therefore has potential for clinical translation if the biological efficacy of the implant can be improved over existing gold standards. It provides a unique opportunity for laboratories to perform low-cost, high resolution, additive manufacturing research that is well positioned for clinical translation, using existing regulatory frameworks.
BibTeX:
@article{Dalton2017,
  author = {Paul D. Dalton},
  title = {Melt electrowriting with additive manufacturing principles},
  journal = {Current Opinion in Biomedical Engineering},
  year = {2017},
  volume = {2},
  number = {Supplement C},
  pages = {49 - 57},
  note = {Additive Manufacturing},
  url = {http://www.sciencedirect.com/science/article/pii/S2468451117300156},
  doi = {https://doi.org/10.1016/j.cobme.2017.05.007}
}
Choi, Y., Yi, H., Kim, S. and Cho, D. 3D Cell Printed Tissue Analogues: A New Platform for Theranostics 2017 Theranostics  article URL 
Abstract: Stem cell theranostics has received much attention for noninvasively monitoring and tracing transplanted therapeutic stem cells through imaging agents and imaging modalities. Despite the excellent regenerative capability of stem cells, their efficacy has been limited due to low cellular retention, low survival rate, and low engraftment after implantation. Three-dimensional (3D) cell printing provides stem cells with the similar architecture and microenvironment of the native tissue and facilitates the generation of a 3D tissue-like construct that exhibits remarkable regenerative capacity and functionality as well as enhanced cell viability. Thus, 3D cell printing can overcome the current concerns of stem cell therapy by delivering the 3D construct to the damaged site. Despite the advantages of 3D cell printing, the in vivo and in vitro tracking and monitoring of the performance of 3D cell printed tissue in a noninvasive and real-time manner have not been thoroughly studied. In this review, we explore the recent progress in 3D cell technology and its applications. Finally, we investigate their potential limitations and suggest future perspectives on 3D cell printing and stem cell theranostics.
BibTeX:
@article{Choi2017,
  author = {Choi, Y.J. and Yi, H.G. and Kim, S.W. and Cho, D.W.},
  title = {3D Cell Printed Tissue Analogues: A New Platform for Theranostics},
  journal = {Theranostics},
  year = {2017},
  url = {http://www.thno.org/v07p3118}
}
Charbe, N.B., McCarron, P.A., Lane, M.E. and Tambuwala, M.M. Application of three-dimensional printing for colon targeted drug delivery systems 2017 International Journal of Pharmaceutical Investigation
Vol. 7(2), pp. 47-59 
article URL 
Abstract: Orally administered solid dosage forms currently dominate over all other dosage forms and routes of administrations. However, human gastrointestinal tract (GIT) poses a number of obstacles to delivery of the drugs to the site of interest and absorption in the GIT. Pharmaceutical scientists worldwide have been interested in colon drug delivery for several decades, not only for the delivery of the drugs for the treatment of colonic diseases such as ulcerative colitis and colon cancer but also for delivery of therapeutic proteins and peptides for systemic absorption. Despite extensive research in the area of colon targeted drug delivery, we have not been able to come up with an effective way of delivering drugs to the colon. The current tablets designed for colon drug release depend on either pH-dependent or time-delayed release formulations. During ulcerative colitis the gastric transit time and colon pH-levels is constantly changing depending on whether the patient is having a relapse or under remission. Hence, the current drug delivery system to the colon is based on one-size-fits-all. Fails to effectively deliver the drugs locally to the colon for colonic diseases and delivery of therapeutic proteins and peptides for systemic absorption from the colon. Hence, to overcome the current issues associated with colon drug delivery, we need to provide the patients with personalized tablets which are specifically designed to match the individual's gastric transit time depending on the disease state. Three-dimensional (3D) printing (3DP) technology is getting cheaper by the day and bespoke manufacturing of 3D-printed tablets could provide the solutions in the form of personalized colon drug delivery system. This review provides a bird's eye view of applications and current advances in pharmaceutical 3DP with emphasis on the development of colon targeted drug delivery systems.
BibTeX:
@article{Charbe2017,
  author = {Charbe, Nitin B. and McCarron, Paul A. and Lane, Majella E. and Tambuwala, Murtaza M.},
  title = {Application of three-dimensional printing for colon targeted drug delivery systems},
  journal = {International Journal of Pharmaceutical Investigation},
  publisher = {Medknow Publications & Media Pvt Ltd},
  year = {2017},
  volume = {7},
  number = {2},
  pages = {47--59},
  url = {http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5553264/}
}
Borovjagin, A.V., Ogle, B.M., Berry, J.L. and Zhang, J. From Microscale Devices to 3D Printing 2017 Circulation Research
Vol. 120(1), pp. 150-165 
article DOI URL 
Abstract: Current strategies for engineering cardiovascular cells and tissues have yielded a variety of sophisticated tools for studying disease mechanisms, for development of drug therapies, and for fabrication of tissue equivalents that may have application in future clinical use. These efforts are motivated by the need to extend traditional 2-dimensional (2D) cell culture systems into 3D to more accurately replicate in vivo cell and tissue function of cardiovascular structures. Developments in microscale devices and bioprinted 3D tissues are beginning to supplant traditional 2D cell cultures and preclinical animal studies that have historically been the standard for drug and tissue development. These new approaches lend themselves to patient-specific diagnostics, therapeutics, and tissue regeneration. The emergence of these technologies also carries technical challenges to be met before traditional cell culture and animal testing become obsolete. Successful development and validation of 3D human tissue constructs will provide powerful new paradigms for more cost effective and timely translation of cardiovascular tissue equivalents.
BibTeX:
@article{Borovjagin2017,
  author = {Borovjagin, Anton V. and Ogle, Brenda M. and Berry, Joel L. and Zhang, Jianyi},
  title = {From Microscale Devices to 3D Printing},
  journal = {Circulation Research},
  publisher = {American Heart Association, Inc.},
  year = {2017},
  volume = {120},
  number = {1},
  pages = {150--165},
  url = {http://circres.ahajournals.org/content/120/1/150},
  doi = {https://doi.org/10.1161/CIRCRESAHA.116.308538}
}
Baumann, B., Jungst, T., Stichler, S., Feineis, S., Wiltschka, O., Kuhlmann, M., Lindén, M. and Groll, J. Control of Nanoparticle Release Kinetics from 3D Printed Hydrogel Scaffolds 2017 Angewandte Chemie International Edition, pp. n/a-n/a  article DOI  
Abstract: The convergence of biofabrication with nanotechnology is largely unexplored but enables geometrical control of cell-biomaterial arrangement combined with controlled drug delivery and release. As a step towards integration of these two fields of research, this study demonstrates that modulation of electrostatic nanoparticle–polymer and nanoparticle–nanoparticle interactions can be used for tuning nanoparticle release kinetics from 3D printed hydrogel scaffolds. This generic strategy can be used for spatiotemporal control of the release kinetics of nanoparticulate drug vectors in biofabricated constructs.
BibTeX:
@article{Baumann2017,
  author = {Baumann, Bernhard and Jungst, Tomasz and Stichler, Simone and Feineis, Susanne and Wiltschka, Oliver and Kuhlmann, Matthias and Lindén, Mika and Groll, Jürgen},
  title = {Control of Nanoparticle Release Kinetics from 3D Printed Hydrogel Scaffolds},
  journal = {Angewandte Chemie International Edition},
  year = {2017},
  pages = {n/a--n/a},
  doi = {https://doi.org/10.1002/anie.201700153}
}
Aljohani, W., Ullah, M.W., Zhang, X. and Yang, G. Bioprinting and its applications in tissue engineering and regenerative medicine 2017 International Journal of Biological Macromolecules  article DOI URL 
Abstract: Abstract Bioprinting of three-dimensional constructs mimicking natural-like extracellular matrix has revolutionized biomedical technology. Bioprinting technology circumvents various discrepancies associated with current tissue engineering strategies by providing an automated and advanced platform to fabricate various biomaterials through precise deposition of cells and polymers in a premeditated fashion. However, few obstacles associated with development of 3D scaffolds including varied properties of polymers used and viability, controlled distribution, and vascularization, etc. of cells hinder bioprinting of complex structures. Therefore, extensive efforts have been made to explore the potential of various natural polymers (e.g. cellulose, gelatin, alginate, and chitosan, etc.) and synthetic polymers in bioprinting by tuning their printability and cross-linking features, mechanical and thermal properties, biocompatibility, and biodegradability, etc. This review describes the potential of these polymers to support adhesion and proliferation of viable cells to bioprint cell laden constructs, bone, cartilage, skin, and neural tissues, and blood vessels, etc. for various applications in tissue engineering and regenerative medicines. Further, it describes various challenges associated with current bioprinting technology and suggests possible solutions. Although at early stage of development, the potential benefits of bioprinting technology are quite clear and expected to open new gateways in biomedical, pharmaceutics and several other fields in near future.
BibTeX:
@article{Aljohani2017,
  author = {Waeljumah Aljohani and Muhammad Wajid Ullah and Xianglin Zhang and Guang Yang},
  title = {Bioprinting and its applications in tissue engineering and regenerative medicine},
  journal = {International Journal of Biological Macromolecules},
  year = {2017},
  url = {http://www.sciencedirect.com/science/article/pii/S0141813017325862},
  doi = {https://doi.org/10.1016/j.ijbiomac.2017.08.171}
}
Bastola, A., Hoang Tan, V. and Lin, L. Magnetorheological Elastomer: A novel approach of synthesis 2016 2ND INTERNATIONAL CONFERENCE IN SPORTS SCIENCE & TECHNOLOGY, At NTU, Singapore  conference URL 
Abstract: In this study, we have developed a new type of magnetorheological (MR) materials based on a combination of a magnetorheological fluid and an elastomer. 3D printing was employed as the ‘key’ technique to fabricate this type of materials. Our preliminary experimental results have shown a 50% increase of compression stiffness under a magnetic field strength of 0.3 T (tesla). Compared to the previous MR materials, this hybrid MREs possess good features of both MR fluids and MR elastomers. Therefore, the materials are potentially applicable for the smart suspension systems in bicycles and sport car
BibTeX:
@conference{Bastola2016,
  author = {Bastola, Anil and Hoang Tan, Vin and Lin, Li},
  title = {Magnetorheological Elastomer: A novel approach of synthesis},
  booktitle = {2ND INTERNATIONAL CONFERENCE IN SPORTS SCIENCE & TECHNOLOGY, At NTU, Singapore},
  year = {2016},
  url = {https://www.researchgate.net/publication/311738527_Magnetorheological_Elastomer_A_novel_approach_of_synthesis}
}
Durual, S. Impression 3D et régénération osseuse, un mariage plein d'avenir 2016 Biomateriaux Cliniques
Vol. 1BioMatériaux Cliniques, pp. 58-61 
article URL 
BibTeX:
@article{Durual2016,
  author = {Durual, Stéphane},
  title = {Impression 3D et régénération osseuse, un mariage plein d'avenir},
  booktitle = {BioMatériaux Cliniques},
  journal = {Biomateriaux Cliniques},
  year = {2016},
  volume = {1},
  pages = {58-61},
  url = {https://www.researchgate.net/publication/315837115_Impression_3D_et_regeneration_osseuse_un_mariage_plein_d%27avenir}
}
Gudapati, H., Dey, M. and Ozbolat, I. A comprehensive review on droplet-based bioprinting: Past, present and future. 2016 Biomaterials
Vol. 102, pp. 20-42 
article URL 
Abstract: Droplet-based bioprinting (DBB) offers greater advantages due to its simplicity and agility with precise control on deposition of biologics including cells, growth factors, genes, drugs and biomaterials, and has been a prominent technology in the bioprinting community. Due to its immense versatility, DBB technology has been adopted by various application areas, including but not limited to, tissue engineering and regenerative medicine, transplantation and clinics, pharmaceutics and high-throughput screening, and cancer research. Despite the great benefits, the technology currently faces several challenges such as a narrow range of available bioink materials, bioprinting-induced cell damage at substantial levels, limited mechanical and structural integrity of bioprinted constructs, and restrictions on the size of constructs due to lack of vascularization and porosity. This paper presents a first-time review of DBB and comprehensively covers the existing DBB modalities including inkjet, electrohydrodynamic, acoustic, and micro-valve bioprinting. The recent notable studies are highlighted, the relevant bioink biomaterials and bioprinters are expounded, the application areas are presented, and the future prospects are provided to the reader.
BibTeX:
@article{Gudapati2016,
  author = {Gudapati, Hemanth and Dey, Madhuri and Ozbolat, Ibrahim},
  title = {A comprehensive review on droplet-based bioprinting: Past, present and future.},
  journal = {Biomaterials},
  year = {2016},
  volume = {102},
  pages = {20--42},
  url = {https://doi.org/10.1016/j.biomaterials.2016.06.012}
}
Sears, N.A., Seshadri, D.R., Dhavalikar, P.S. and Cosgriff-Hernandez, E. A Review of Three-Dimensional Printing in Tissue Engineering 2016 Tissue Engineering Part B: Reviews
Vol. 22(4), pp. 298-310 
article DOI  
Abstract: Recent advances in three-dimensional (3D) printing technologies have led to a rapid expansion of applications from the creation of anatomical training models for complex surgical procedures to the printing of tissue engineering constructs. In addition to achieving the macroscale geometry of organs and tissues, a print layer thickness as small as 20 mm allows for reproduction of the microarchitectures of bone and other tissues. Techniques with even higher precision are currently being investigated to enable reproduction of smaller tissue features such as hepatic lobules. Current research in tissue engineering focuses on the development of compatible methods (printers) and materials (bioinks) that are capable of producing biomimetic scaffolds. In this review, an overview of current 3D printing techniques used in tissue engineering is provided with an emphasis on the printing mechanism and the resultant scaffold characteristics. Current practical challenges and technical limitations are emphasized and future trends of bioprinting are discussed.
BibTeX:
@article{Sears2016,
  author = {Sears, Nick A. and Seshadri, Dhruv R. and Dhavalikar, Prachi S. and Cosgriff-Hernandez, Elizabeth},
  title = {A Review of Three-Dimensional Printing in Tissue Engineering},
  journal = {Tissue Engineering Part B: Reviews},
  publisher = {Mary Ann Liebert, Inc., publishers},
  year = {2016},
  volume = {22},
  number = {4},
  pages = {298--310},
  doi = {https://doi.org/10.1089/ten.teb.2015.0464}
}
Wang, W., Caetano, G., Chiang, W.-H., Sousa, A.L., Blaker, J., Frade, M.A.R.C.O., Frade, C. and Jorge Bártolo, P. Morphological, mechanical and biological assessment of PCL/pristine graphene scaffolds for bone regeneration 2016 International Journal of Bioprinting
Vol. 2, pp. 95-105 
article URL 
Abstract: Scaffolds are physical substrates for cell attachment, proliferation, and differentiation, ultimately leading to the regeneration of tissues. They must be designed according to specific biomechanical requirements such as mechanical properties, surface characteristics, biodegradability, biocompatibility, and porosity. The optimal design of a scaffold for a specific tissue strongly depends on both materials and manufacturing processes. Polymeric scaffolds reinforced with electro-active particles could play a key role in tissue engineering by modulating cell proliferation and differentiation. This paper investigates the use of an extrusion additive manufacturing system to produce PCL/pristine graphene scaffolds for bone tissue applications. PCL/pristine graphene blends were prepared using a melt blending process. Scaffolds with regular and reproducible architecture were produced with different concentrations of pristine graphene. Scaffolds were evaluated from morphological, mechanical, and biological view. The results suggest that the addition of pristine graphene improves the mechanical performance of the scaffolds, reduces the hydrophobicity, and improves cell viability and proliferation.
BibTeX:
@article{Wang2016a,
  author = {Wang, Weiguang and Caetano, Guilherme and Chiang, Wei-Hung and Sousa, Ana Leticia and Blaker, Jonny and Frade, M. A. R. C. O. and Frade, Cipriani and Jorge Bártolo, Paulo},
  title = {Morphological, mechanical and biological assessment of PCL/pristine graphene scaffolds for bone regeneration},
  journal = {International Journal of Bioprinting},
  year = {2016},
  volume = {2},
  pages = {95--105},
  url = {http://ijb.whioce.com/index.php/int-j-bioprinting/article/view/85}
}
Visscher, D.O., Bos, E.J., Peeters, M., Kuzmin, N.V., Groot, M.L., Helder, M.N. and van Zuijlen, P.P.M. Cartilage Tissue Engineering: Preventing Tissue Scaffold Contraction Using a 3D-Printed Polymeric Cage. 2016 Tissue engineering Part C, Methods
Vol. 22, pp. 573-84 
article URL 
Abstract: Scaffold contraction is a common but underestimated problem in the field of tissue engineering. It becomes particularly problematic when creating anatomically complex shapes such as the ear. The aim of this study was to develop a contraction-free biocompatible scaffold construct for ear cartilage tissue engineering. To address this aim, we used three constructs: (i) a fibrin/hyaluronic acid (FB/HA) hydrogel, (ii) a FB/HA hydrogel combined with a collagen I/III scaffold, and (iii) a cage construct containing (ii) surrounded by a 3D-printed poly-varepsilon-caprolactone mold. A wide range of different cell types were tested within these constructs, including chondrocytes, perichondrocytes, adipose-derived mesenchymal stem cells, and their combinations. After in vitro culturing for 1, 14, and 28 days, all constructs were analyzed. Macroscopic observation showed severe contraction of the cell-seeded hydrogel (i). This could be prevented, in part, by combining the hydrogel with the collagen scaffold (ii) and prevented in total using the 3D-printed cage construct (iii). (Immuno)histological analysis, multiphoton laser scanning microscopy, and biomechanical analysis showed extracellular matrix deposition and increased Young's modulus and thereby the feasibility of ear cartilage engineering. These results demonstrated that the 3D-printed cage construct is an adequate model for contraction-free ear cartilage engineering using a range of cell combinations.
BibTeX:
@article{Visscher2016,
  author = {Visscher, Dafydd O. and Bos, Ernst J. and Peeters, Mirte and Kuzmin, Nikolay V. and Groot, Marie Louise and Helder, Marco N. and van Zuijlen, Paul P. M.},
  title = {Cartilage Tissue Engineering: Preventing Tissue Scaffold Contraction Using a 3D-Printed Polymeric Cage.},
  journal = {Tissue engineering Part C, Methods},
  year = {2016},
  volume = {22},
  pages = {573--84},
  url = {https://www.liebertpub.com/doi/abs/10.1089/ten.TEC.2016.0073?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dpubmed}
}
Stichler, S., Jungst, T., Schamel, M., Zilkowski, I., Kuhlmann, M., Bock, T., Blunk, T., Tessmar, J. and Groll, J. Thiol-ene Clickable Poly(glycidol) Hydrogels for Biofabrication. 2016 Annals of biomedical engineering  article URL 
Abstract: In this study we introduce linear poly(glycidol) (PG), a structural analog of poly(ethylene glycol) bearing side chains at each repeating unit, as polymer basis for bioink development. We prepare allyl- and thiol-functional linear PG that can rapidly be polymerized to a three-dimensionally cross-linked hydrogel network via UV mediated thiol-ene click reaction. Influence of polymer concentration and UV irradiation on mechanical properties and swelling behavior was examined. Thiol-functional PG was synthesized in two structural variations, one containing ester groups that are susceptible to hydrolytic cleavage, and the other one ester-free and stable against hydrolysis. This allowed the preparation of degradable and non-degradable hydrogels. Cytocompatibility of the hydrogel was demonstrated by encapsulation of human bone marrow-derived mesenchymal stem cells (hBMSCs). Rheological properties of the hydrogels were adjusted for dispense plotting by addition of high molecular weight hyaluronic acid. The optimized formulation enabled highly reproducible plotting of constructs composed of 20 layers with an overall height of 3.90 mm.
BibTeX:
@article{Stichler2016,
  author = {Stichler, Simone and Jungst, Tomasz and Schamel, Martha and Zilkowski, Ilona and Kuhlmann, Matthias and Bock, Thomas and Blunk, Torsten and Tessmar, Jorg and Groll, Jurgen},
  title = {Thiol-ene Clickable Poly(glycidol) Hydrogels for Biofabrication.},
  journal = {Annals of biomedical engineering},
  year = {2016},
  url = {https://link.springer.com/article/10.1007%2Fs10439-016-1633-3}
}
Kesti, M., Fisch, P., Pensalfini, M., Mazza, E. and Zenobi-Wong, M. Guidelines for standardization of bioprinting: a systematic study of process parameters and their effect on bioprinted structures 2016 BioNanoMaterials
Vol. 17(3-4), pp. 193-204 
article DOI  
Abstract: Biofabrication techniques including three-dimensional bioprinting could be used one day to fabricate living, patient-specific tissues and organs for use in regenerative medicine. Compared to traditional casting and molding methods, bioprinted structures can be much more complex, containing for example multiple materials and cell types in controlled spatial arrangement, engineered porosity, reinforcement structures and gradients in mechanical properties. With this complexity and increased function, however, comes the necessity to develop guidelines to standardize the bioprinting process, so printed grafts can safely enter the clinics. The bioink material must firstly fulfil requirements for biocompatibility and flow. Secondly, it is important to understand how process parameters affect the final mechanical properties of the printed graft. Using a gellan-alginate physically crosslinked bioink as an example, we show shear thinning and shear recovery properties which allow good printing resolution. Printed tensile specimens were used to systematically assess effect of line spacing, printing direction and crosslinking conditions. This standardized testing allowed direct comparison between this bioink and three commercially-available products. Bioprinting is a promising, yet complex fabrication method whose outcome is sensitive to a range of process parameters. This study provides the foundation for highly needed best practice guidelines for reproducible and safe bioprinted grafts.
BibTeX:
@article{Kesti2016,
  author = {Matti Kesti and Philipp Fisch and Marco Pensalfini and Edoardo Mazza and Marcy Zenobi-Wong},
  title = {Guidelines for standardization of bioprinting: a systematic study of process parameters and their effect on bioprinted structures},
  journal = {BioNanoMaterials},
  year = {2016},
  volume = {17},
  number = {3-4},
  pages = {193--204},
  doi = {https://doi.org/10.1515/bnm-2016-0004}
}
Durual, S. Emergence d'une nouvelle génération de substituts osseux synthétiques imprimés en 3D 2016 BIOMATERIAUX D’AUJOURD’HUI ET DE DEMAINBI
Vol. Hors-sérieJournal de parodontologie et d'implantologie orale, pp. 63-67 
article URL 
BibTeX:
@article{Durual2016a,
  author = {Durual, Stéphane},
  title = {Emergence d'une nouvelle génération de substituts osseux synthétiques imprimés en 3D},
  booktitle = {Journal de parodontologie et d'implantologie orale},
  journal = {BIOMATERIAUX D’AUJOURD’HUI ET DE DEMAINBI},
  year = {2016},
  volume = {Hors-série},
  pages = {63-67},
  url = {https://www.researchgate.net/publication/304791633_Emergence_d'une_nouvelle_generation_de_substituts_osseux_synthetiques_imprimes_en_3D}
}
Khati, V., Kellomäki, M. and Anderson, H.S. Development of a Robust Decellularized Extracellular Matrix Bioink for 3D Bioprinting 2016 School: Tampere University of Technology  mastersthesis  
Abstract: Tissue engineering is an interdisciplinary field that has revolutionized the medical world by using a combination of biomaterials, bioactive factors and living cells to reconstruct or regenerate the damaged/lost tissue. However, there is a crucial need to create a functional three dimensional (3D) microarchitecture to efficiently recreate or mimic the spatial and chemical complexity inherent to native tissues/organs. 3D bioprinting technology offers such unique prospect to produce biological substitutes, as it enables reproducible and automated production of complex living tissue constructs. Currently, various types of biomaterials have been used for 3D bioprinting, however, these materials are unable to exhibit the complexities of the natural extracellular matrix and thus, are incapable to provide a suitable microenvironment for seeded cells.

The aim of this thesis is to develop a robust decellularized liver matrix (dLM) bioink, which is both cytocompatible and 3D printable. By utilizing the intrinsic functional groups present in the decellularized liver matrix proteins, the dLM was modified into a 3D printable bioink by a cytocompatible gelation mechanism via protein crosslinking by homobifunctional Polyethylene glycol with Succinimidyl valerate (SVA-PEG-SVA). The active succinimidyl ester reacts with amine groups on gelatin and dLM to form a stable amide linkage when incubated at 37°C. The rheological property of this modified,
temperature responsive bioink measured under oscillatory conditions suggests the formation of crosslinked gel after incubation for 30 min and exhibited higher storage modulus than loss modulus. Therefore, after gelation, the bioink can retain its structure, which is a precondition for developing a cell laden structure.

The optimized bioink rheology, controllable gelation mechanism and bioprinting parameters were used to achieve high cell viability and activity. This method of bioink production is inexpensive and offers a unique path to generate tissue/organ models for screening novel drug compounds or to predict toxicity.
BibTeX:
@mastersthesis{Khati2016,
  author = {Vamakshi Khati and Minna Kellomäki and Helene Svahn Anderson},
  title = {Development of a Robust Decellularized Extracellular Matrix Bioink for 3D Bioprinting},
  school = {Tampere University of Technology},
  year = {2016}
}
Wu, C., Wang, B., Zhang, C., Wysk, R.A. and Chen, Y.-W. Bioprinting: an assessment based on manufacturing readiness levels 2016 Critical Reviews in Biotechnology
Vol. 0(0), pp. 1-22 
article DOI  
Abstract: AbstractOver the last decade, bioprinting has emerged as a promising technology in the fields of tissue engineering and regenerative medicine. With recent advances in additive manufacturing, bioprinting is poised to provide patient-specific therapies and new approaches for tissue and organ studies, drug discoveries and even food manufacturing. Manufacturing Readiness Level (MRL) is a method that has been applied to assess manufacturing maturity and to identify risks and gaps in technology-manufacturing transitions. Technology Readiness Level (TRL) is used to evaluate the maturity of a technology. This paper reviews recent advances in bioprinting following the MRL scheme and addresses corresponding MRL levels of engineering challenges and gaps associated with the translation of bioprinting from lab-bench experiments to ultimate full-scale manufacturing of tissues and organs. According to our step-by-step TRL and MRL assessment, after years of rigorous investigation by the biotechnology community, bioprinting is on the cusp of entering the translational phase where laboratory research practices can be scaled up into manufacturing products specifically designed for individual patients.
BibTeX:
@article{Wu2016,
  author = {Changsheng Wu and Ben Wang and Chuck Zhang and Richard A. Wysk and Yi-Wen Chen},
  title = {Bioprinting: an assessment based on manufacturing readiness levels},
  journal = {Critical Reviews in Biotechnology},
  year = {2016},
  volume = {0},
  number = {0},
  pages = {1--22},
  note = {PMID: 27023266},
  doi = {https://doi.org/10.3109/07388551.2016.1163321}
}
Wang, W.G., Chang, W.H. and Bartolo, P.J. Design, fabrication and evaluation of pcl-graphene scaffolds for bone regeneration 2016 Proceedings of the 2nd International Conference on Progress in Additive Manufacturing (Pro-AM 2016)  conference DOI  
Abstract: Scaffolds are physical substrates for cell attachment, proliferation and differentiation, ultimately leading to the regeneration of tissues. They must be designed according to specific biomechanical requirements such as mechanical properties, surface characteristics, biodegradability, biocompatibility and porosity. The optimal design of a scaffold for a specific tissue strongly depends on both materials and manufacturing processes. Polymeric scaffolds reinforced with electro-active particles could play a key role in tissue engineering by modulating cell proliferation and differentiation. This paper investigates the use of an extrusion additive manufacturing system to produce PCL/pristine graphene scaffolds for bone tissue applications. PCL/pristine graphene blends were prepared using a melt blend process. Scaffolds with the same architecture but different contents of pristine graphene were evaluated from a chemical, morphological and mechanical view. Scaffolds with regular and reproducible architecture and a uniform dispersion of pristine graphene flakes were produced. It was also possible to observe that the addition of pristine graphene improves the mechanical performance of the scaffolds.
BibTeX:
@conference{Wang2016,
  author = {Wang, W. G. and Chang, W. H. and Bartolo, P. J.},
  title = {Design, fabrication and evaluation of pcl-graphene scaffolds for bone regeneration},
  booktitle = {Proceedings of the 2nd International Conference on Progress in Additive Manufacturing (Pro-AM 2016)},
  year = {2016},
  doi = {https://dr.ntu.edu.sg/handle/10220/41798}
}
Visscher, D.O., Farré-Guasch, E., Helder, M.N., Gibbs, S., Forouzanfar, T., van Zuijlen, P.P. and Wolff, J. Advances in Bioprinting Technologies for Craniofacial Reconstruction 2016 Trends in Biotechnology
Vol. 34(9), pp. 700-710 
article DOI  
Abstract: Recent developments in craniofacial reconstruction have shown important advances in both the materials and methods used. While autogenous tissue is still considered to be the gold standard for these reconstructions, the harvesting procedure remains tedious and in many cases causes significant donor site morbidity. These limitations have subsequently led to the development of less invasive techniques such as 3D bioprinting that could offer possibilities to manufacture patient-tailored bioactive tissue constructs for craniofacial reconstruction. Here, we discuss the current technological and (pre)clinical advances of 3D bioprinting for use in craniofacial reconstruction and highlight the challenges that need to be addressed in the coming years.
Recent developments in craniofacial reconstruction have shown important advances in both the materials and methods used. While autogenous tissue is still considered to be the gold standard for these reconstructions, the harvesting procedure remains tedious and in many cases causes significant donor site morbidity. These limitations have subsequently led to the development of less invasive techniques such as 3D bioprinting that could offer possibilities to manufacture patient-tailored bioactive tissue constructs for craniofacial reconstruction. Here, we discuss the current technological and (pre)clinical advances of 3D bioprinting for use in craniofacial reconstruction and highlight the challenges that need to be addressed in the coming years.
BibTeX:
@article{Visscher2016b,
  author = {Visscher, Dafydd O. and Farré-Guasch, Elisabet and Helder, Marco N. and Gibbs, Susan and Forouzanfar, Tymour and van Zuijlen, Paul P. and Wolff, Jan},
  title = {Advances in Bioprinting Technologies for Craniofacial Reconstruction},
  journal = {Trends in Biotechnology},
  publisher = {Elsevier},
  year = {2016},
  volume = {34},
  number = {9},
  pages = {700--710},
  doi = {https://doi.org/10.1016/j.tibtech.2016.04.001}
}
Suntornnond, R., Tan, E.Y.S., An, J. and Chua, C.K. A Mathematical Model on the Resolution of Extrusion Bioprinting for the Development of New Bioinks 2016 Materials
Vol. 9(9), pp. 756 
article DOI URL 
Abstract: Pneumatic extrusion-based bioprinting is a recent and interesting technology that is very useful for biomedical applications. However, many process parameters in the bioprinter need to be fully understood in order to print at an adequate resolution. In this paper, a simple yet accurate mathematical model to predict the printed width of a continuous hydrogel line is proposed, in which the resolution is expressed as a function of nozzle size, pressure, and printing speed. A thermo-responsive hydrogel, pluronic F127, is used to validate the model predictions. This model could provide a platform for future correlation studies on pneumatic extrusion-based bioprinting as well as for developing new bioink formulations.
BibTeX:
@article{Suntornnond2016a,
  author = {Suntornnond, Ratima and Tan, Edgar Yong Sheng and An, Jia and Chua, Chee Kai},
  title = {A Mathematical Model on the Resolution of Extrusion Bioprinting for the Development of New Bioinks},
  journal = {Materials},
  year = {2016},
  volume = {9},
  number = {9},
  pages = {756},
  url = {http://www.mdpi.com/1996-1944/9/9/756},
  doi = {https://doi.org/10.3390/ma9090756}
}
Suntornnond, R., An, J. and Chua, C.K. A Preliminary Study on the Extrusion Resolution of Pluronic F127 for Bioprinting Thermo-responsive Hydrogel Constructs 2016 Proceedings of the 2nd International Conference on Progress in Additive Manufacturing (Pro-AM 2016)  conference URL 
Abstract: Thermo-responsive hydrogels have gained more attention recently due to their unique characteristic of tunable sol-gel transition when temperature is changed. They have been used for many biomedical applications from drug delivery to fabrication of soft tissue scaffolds via 3D bioprinting. In this paper, the preliminary investigation on bioprinted thermo-responsive hydrogels were conducted in order to find out the correlations between size of nozzle, stage moving speed and gas pressure for achieving optimum printing resolution. The hydrogel that was used in this study was pluronic F127 at 24.5 wt % concentration. Two sizes of nozzle were used (25G and 30G) while stage moving speed (printing speed) and gas pressure were designed to be three levels each. A total of 18 experiments were conducted. The results show that the thinnest continuous line (highest resolution) of hydrogel could be obtained even when a larger nozzle is used. This paper suggests a relationship of the main parameters with the size of nozzle on extrusion based bioprinter, and the results from this study may provide a platform for future correlation studies on extrusion based bioprinting.
BibTeX:
@conference{Suntornnond2016,
  author = {Suntornnond, R. and An, J. and Chua, C. K.},
  title = {A Preliminary Study on the Extrusion Resolution of Pluronic F127 for Bioprinting Thermo-responsive Hydrogel Constructs},
  booktitle = {Proceedings of the 2nd International Conference on Progress in Additive Manufacturing (Pro-AM 2016)},
  year = {2016},
  url = {https://dr.ntu.edu.sg/handle/10220/41814?show=full}
}
Sommer, M.R., Schaffner, M., Carnelli, D. and Studart, A.R. 3D Printing of Hierarchical Silk Fibroin Structures 2016 ACS Applied Materials & Interfaces
Vol. 8(50), pp. 34677-34685 
article DOI  
Abstract: Like many other natural materials, silk is hierarchically structured from the amino acid level up to the cocoon or spider web macroscopic structures. Despite being used industrially in a number of applications, hierarchically structured silk fibroin objects with a similar degree of architectural control as in natural structures have not been produced yet due to limitations in fabrication processes. In a combined top-down and bottom-up approach, we exploit the freedom in macroscopic design offered by 3D printing and the template-guided assembly of ink building blocks at the meso- and nanolevel to fabricate hierarchical silk porous materials with unprecedented structural control. Pores with tunable sizes in the range 40–350 μm are generated by adding sacrificial organic microparticles as templates to a silk fibroin-based ink. Commercially available wax particles or monodisperse polycaprolactone made by microfluidics can be used as microparticle templates. Since closed pores are generated after template removal, an ultrasonication treatment can optionally be used to achieve open porosity. Such pore templating particles can be further modified with nanoparticles to create a hierarchical template that results in porous structures with a defined nanotopography on the pore walls. The hierarchically porous silk structures obtained with this processing technique can potentially be utilized in various application fields from structural materials to thermal insulation to tissue engineering scaffolds.
BibTeX:
@article{Sommer2016,
  author = {Sommer, Marianne R. and Schaffner, Manuel and Carnelli, Davide and Studart, André R.},
  title = {3D Printing of Hierarchical Silk Fibroin Structures},
  journal = {ACS Applied Materials & Interfaces},
  year = {2016},
  volume = {8},
  number = {50},
  pages = {34677-34685},
  note = {PMID: 27933765},
  doi = {https://doi.org/10.1021/acsami.6b11440}
}
Ruiz-Cantu, L., Gleadall, A., Faris, C., Segal, J., Shakesheff, K. and Yang, J. Characterisation of the surface structure of 3D printed scaffolds for cell infiltration and surgical suturing 2016 Biofabrication
Vol. 8(1), pp. 015016 
article URL 
Abstract: 3D printing is of great interest for tissue engineering scaffolds due to the ability to form complex geometries and control internal structures, including porosity and pore size. The porous structure of scaffolds plays an important role in cell ingrowth and nutrition infusion. Although the internal porosity and pore size of 3D printed scaffolds have been frequently studied, the surface porosity and pore size, which are critical for cell infiltration and mass transport, have not been investigated. The surface geometry can differ considerably from the internal scaffold structure depending on the 3D printing process. It is vital to be able to control the surface geometry of scaffolds as well as the internal structure to fabricate optimal architectures. This work presents a method to control the surface porosity and pore size of 3D printed scaffolds. Six scaffold designs have been printed with surface porosities ranging from 3% to 21%. We have characterised the overall scaffold porosity and surface porosity using optical microscopy and microCT. It has been found that surface porosity has a significant impact on cell infiltration and proliferation. In addition, the porosity of the surface has been found to have an effect on mechanical properties and on the forces required to penetrate the scaffold with a surgical suturing needle. To the authors’ knowledge, this study is the first to investigate the surface geometry of extrusion-based 3D printed scaffolds and demonstrates the importance of surface geometry in cell infiltration and clinical manipulation.
BibTeX:
@article{Ruiz-Cantu2016,
  author = {Laura Ruiz-Cantu and Andrew Gleadall and Callum Faris and Joel Segal and Kevin Shakesheff and Jing Yang},
  title = {Characterisation of the surface structure of 3D printed scaffolds for cell infiltration and surgical suturing},
  journal = {Biofabrication},
  year = {2016},
  volume = {8},
  number = {1},
  pages = {015016},
  url = {http://stacks.iop.org/1758-5090/8/i=1/a=015016}
}
Raphael, B., Khalil, T., Workman, V.L., Smith, A., Brown, C.P., Streulli, C., Saiani, A. and Domingos, M. 3D cell bioprinting of self-assembling peptide-based hydrogels 2016 Materials Letters  article DOI URL 
Abstract: Abstract Bioprinting of 3D cell-laden constructs with well-defined architectures and controlled spatial distribution of cells is gaining importance in the field of Tissue Engineering. New 3D tissue models are being developed to study the complex cellular interactions that take place during both tissue development and in the regeneration of damaged and/or diseased tissues. Despite advances in 3D printing technologies, suitable hydrogels or 'bioinks' with enhanced printability and cell viability are lacking. Here we report a study on the 3D bioprinting of a novel group of self-assembling peptide-based hydrogels. Our results demonstrate the ability of the system to print well-defined 3D cell laden constructs with variable stiffness and improved structural integrity, whilst providing a cell-friendly extracellular matrix “like” microenvironment. Biological assays reveal that mammary epithelial cells remain viable after 7 days of in vitro culture, independent of the hydrogel stiffness.
BibTeX:
@article{Raphael2016,
  author = {Bella Raphael and Tony Khalil and Victoria L. Workman and Andrew Smith and Cameron P Brown and Charles Streulli and Alberto Saiani and Marco Domingos},
  title = {3D cell bioprinting of self-assembling peptide-based hydrogels},
  journal = {Materials Letters},
  year = {2016},
  url = {http://www.sciencedirect.com/science/article/pii/S0167577X16320122},
  doi = {https://doi.org/10.1016/j.matlet.2016.12.127}
}
Passamai, V.E., Dernowsek, J.A., Nogueira, J., Lara, V., Vilalba, F., Mironov, V.A., Rezende, R.A. and da Silva, J.V. From 3D Bioprinters to a fully integrated Organ Biofabrication Line 2016 Journal of Physics: Conference Series
Vol. 705(1), pp. 012010 
article URL 
Abstract: About 30 years ago, the 3D printing technique appeared. From that time on, engineers in medical science field started to look at 3D printing as a partner. Firstly, biocompatible and biodegradable 3D structures for cell seeding called “scaffolds” were fabricated for in vitro and in vivo animal trials. The advances proved to be of great importance, but, the use of scaffolds faces some limitations, such as low homogeneity and low density of cell aggregates. In the last decade, 3D bioprinting technology emerged as a promising approach to overcome these limitations and as one potential solution to the challenge of organ fabrication, to obtain very similar 3D human tissues, not only for transplantation, but also for drug discovery, disease research and to decrease the usage of animals in laboratory experimentation. 3D bioprinting allowed the fabrication of 3D alive structures with higher and controllable cell density and homogeneity. Other advantage of biofabrication is that the tissue constructs are solid scaffold-free. This paper presents the 3D bioprinting technology; equipment development, stages and components of a complex Organ Bioprinting Line (OBL) and the importance of developing a Virtual OBL.
BibTeX:
@article{Passamai2016,
  author = {V E Passamai and J A Dernowsek and J Nogueira and V Lara and F Vilalba and V A Mironov and R A Rezende and J V da Silva},
  title = {From 3D Bioprinters to a fully integrated Organ Biofabrication Line},
  journal = {Journal of Physics: Conference Series},
  year = {2016},
  volume = {705},
  number = {1},
  pages = {012010},
  url = {http://stacks.iop.org/1742-6596/705/i=1/a=012010}
}
Ozbolat, I.T., Peng, W. and Ozbolat, V. Application areas of 3D bioprinting 2016 Drug Discovery Today
Vol. 21(8), pp. 1257-1271 
article DOI URL 
Abstract: Three dimensional (3D) bioprinting has been a powerful tool in patterning and precisely placing biologics, including living cells, nucleic acids, drug particles, proteins and growth factors, to recapitulate tissue anatomy, biology and physiology. Since the first time of cytoscribing cells demonstrated in 1986, bioprinting has made a substantial leap forward, particularly in the past 10 years, and it has been widely used in fabrication of living tissues for various application areas. The technology has been recently commercialized by several emerging businesses, and bioprinters and bioprinted tissues have gained significant interest in medicine and pharmaceutics. This Keynote review presents the bioprinting technology and covers a first-time comprehensive overview of its application areas from tissue engineering and regenerative medicine to pharmaceutics and cancer research.
BibTeX:
@article{Ozbolat2016,
  author = {Ibrahim T. Ozbolat and Weijie Peng and Veli Ozbolat},
  title = {Application areas of 3D bioprinting},
  journal = {Drug Discovery Today},
  year = {2016},
  volume = {21},
  number = {8},
  pages = {1257--1271},
  url = {http://www.sciencedirect.com/science/article/pii/S1359644616301106},
  doi = {https://doi.org/10.1016/j.drudis.2016.04.006}
}
Ozbolat, I.T., Moncal, K.K. and Gudapati, H. Evaluation of bioprinter technologies 2016 Additive Manufacturing  article DOI URL 
Abstract: Abstract Since the first printing of biologics with cytoscribing as demonstrated by Klebe in 1986, three dimensional (3D) bioprinting has made a substantial leap forward, particularly in the last decade. It has been widely used in fabrication of living tissues for various application areas such as tissue engineering and regenerative medicine research, transplantation and clinics, pharmaceutics and high-throughput screening, and cancer research. As bioprinting has gained interest in the medical and pharmaceutical communities, the demand for bioprinters has risen substantially. A myriad of bioprinters have been developed at research institutions worldwide and several companies have emerged to commercialize advanced bioprinter technologies. This paper prefaces the evolution of the field of bioprinting and presents the first comprehensive review of existing bioprinter technologies. Here, a comparative evaluation is performed for bioprinters; limitations with the current bioprinter technologies are discussed thoroughly and future prospects of bioprinters are provided to the reader.
BibTeX:
@article{Ozbolat2016b,
  author = {Ibrahim T. Ozbolat and Kazim K. Moncal and Hemanth Gudapati},
  title = {Evaluation of bioprinter technologies},
  journal = {Additive Manufacturing},
  year = {2016},
  url = {http://www.sciencedirect.com/science/article/pii/S2214860416301312},
  doi = {https://doi.org/10.1016/j.addma.2016.10.003}
}
Ozbolat, I.T. and Hospodiuk, M. Current advances and future perspectives in extrusion-based bioprinting 2016 Biomaterials
Vol. 76, pp. 321-343 
article DOI URL 
Abstract: Abstract Extrusion-based bioprinting (EBB) is a rapidly growing technology that has made substantial progress during the last decade. It has great versatility in printing various biologics, including cells, tissues, tissue constructs, organ modules and microfluidic devices, in applications from basic research and pharmaceutics to clinics. Despite the great benefits and flexibility in printing a wide range of bioinks, including tissue spheroids, tissue strands, cell pellets, decellularized matrix components, micro-carriers and cell-laden hydrogels, the technology currently faces several limitations and challenges. These include impediments to organ fabrication, the limited resolution of printed features, the need for advanced bioprinting solutions to transition the technology bench to bedside, the necessity of new bioink development for rapid, safe and sustainable delivery of cells in a biomimetically organized microenvironment, and regulatory concerns to transform the technology into a product. This paper, presenting a first-time comprehensive review of EBB, discusses the current advancements in EBB\ technology and highlights future directions to transform the technology to generate viable end products for tissue engineering and regenerative medicine.
BibTeX:
@article{Ozbolat2016a,
  author = {Ibrahim T. Ozbolat and Monika Hospodiuk},
  title = {Current advances and future perspectives in extrusion-based bioprinting},
  journal = {Biomaterials},
  year = {2016},
  volume = {76},
  pages = {321--343},
  url = {http://www.sciencedirect.com/science/article/pii/S0142961215008868},
  doi = {https://doi.org/10.1016/j.biomaterials.2015.10.076}
}
Ng, W.L., Yeong, W.Y. and Naing, M.W. Polyelectrolyte gelatin-chitosan hydrogel optimized for 3D bioprinting in skin tissue engineering 2016 International Journal of Bioprinting
Vol. 2(1) 
article DOI URL 
Abstract: Bioprinting is a promising automated platform that enables the simultaneous deposition of multiple types of cells and biomaterials to fabricate complex three-dimensional (3D) tissue constructs. Most of the previous bioprinting works focused on collagen-based biomaterial, which has poor printability and long crosslinking time. This posed a immerse challenge to create a 3D construct with pre-determined shape and configuration. There is a need for a functional material with good printability in order to fabricate a 3D skin construct. Recently, the use of chitosan for wound healing applications has attracted huge attention due to its attractive traits such as its antimicrobial properties and ability to trigger hemostasis. In this paper, we report the modification of chitosan-based biomaterials for functional 3D bioprinting. Modification to the chitosan was carried out via the oppositely charged functional groups from chitosan and gelatin at a specific pH of  pH 6.5 to form polyelectrolyte complexes. The polyelectrolyte hydrogels were evaluated in terms of chemical interactions within polymer blend, rheological properties (viscosities, storage and loss modulus), printing resolution at varying pressures and feed rates and biocompatibility. The chitosan-based hydrogels formulated in this work exhibited good printability at room temperature, high shape fidelity of the printed 3D constructs and good biocompatibility with fibroblast skin cells.
BibTeX:
@article{Ng2016a,
  author = {Wei Long Ng and Wai Yee Yeong and May Win Naing},
  title = {Polyelectrolyte gelatin-chitosan hydrogel optimized for 3D bioprinting in skin tissue engineering},
  journal = {International Journal of Bioprinting},
  year = {2016},
  volume = {2},
  number = {1},
  url = {http://ijb.whioce.com/index.php/int-j-bioprinting/article/view/02009},
  doi = {https://doi.org/10.18063/IJB.2016.01.009}
}
Müller, M., Öztürk, E., Arlov, Ø., Gatenholm, P. and Zenobi-Wong, M. Alginate Sulfate--Nanocellulose Bioinks for Cartilage Bioprinting Applications 2016 Annals of Biomedical Engineering, pp. 1-14  article DOI  
Abstract: One of the challenges of bioprinting is to identify bioinks which support cell growth, tissue maturation, and ultimately the formation of functional grafts for use in regenerative medicine. The influence of this new biofabrication technology on biology of living cells, however, is still being evaluated. Recently we have identified a mitogenic hydrogel system based on alginate sulfate which potently supports chondrocyte phenotype, but is not printable due to its rheological properties (no yield point). To convert alginate sulfate to a printable bioink, it was combined with nanocellulose, which has been shown to possess very good printability. The alginate sulfate/nanocellulose ink showed good printing properties and the non-printed bioink material promoted cell spreading, proliferation, and collagen II synthesis by the encapsulated cells. When the bioink was printed, the biological performance of the cells was highly dependent on the nozzle geometry. Cell spreading properties were maintained with the lowest extrusion pressure and shear stress. However, extruding the alginate sulfate/nanocellulose bioink and chondrocytes significantly compromised cell proliferation, particularly when using small diameter nozzles and valves.
BibTeX:
@article{Mueller2016,
  author = {Müller, Michael and Öztürk, Ece and Arlov, Øystein and Gatenholm, Paul and Zenobi-Wong, Marcy},
  title = {Alginate Sulfate--Nanocellulose Bioinks for Cartilage Bioprinting Applications},
  journal = {Annals of Biomedical Engineering},
  year = {2016},
  pages = {1--14},
  doi = {https://doi.org/10.1007/s10439-016-1704-5}
}
Minas, C., Carnelli, D., Tervoort, E. and Studart, A.R. 3D Printing of Emulsions and Foams into Hierarchical Porous Ceramics 2016 Advanced Materials
Vol. 28(45), pp. 9993-9999 
article DOI  
Abstract: Bulk hierarchical porous ceramics with unprecedented strength-to-weight ratio and tunable pore sizes across three different length scales are printed by direct ink writing. Such an extrusion-based process relies on the formulation of inks in the form of particle-stabilized emulsions and foams that are sufficiently stable to resist coalescence during printing.
BibTeX:
@article{Minas2016,
  author = {Minas, Clara and Carnelli, Davide and Tervoort, Elena and Studart, André R.},
  title = {3D Printing of Emulsions and Foams into Hierarchical Porous Ceramics},
  journal = {Advanced Materials},
  year = {2016},
  volume = {28},
  number = {45},
  pages = {9993--9999},
  doi = {https://doi.org/10.1002/adma.201603390}
}
Melchels, F.P.W., Blokzijl, M.M., Levato, R., Peiffer, Q.C., de Ruijter, M., Hennink, W.E., Vermonden, T. and Malda, J. Hydrogel-based reinforcement of 3D bioprinted constructs 2016 Biofabrication
Vol. 8(3), pp. 035004 
article URL 
Abstract: Progress within the field of biofabrication is hindered by a lack of suitable hydrogel formulations. Here, we present a novel approach based on a hybrid printing technique to create cellularized 3D printed constructs. The hybrid bioprinting strategy combines a reinforcing gel for mechanical support with a bioink to provide a cytocompatible environment. In comparison with thermoplastics such as ##IMG## [http://ej.iop.org/images/1758-5090/8/3/035004/bfaa2f97ieqn1.gif] ε -polycaprolactone, the hydrogel-based reinforcing gel platform enables printing at cell-friendly temperatures, targets the bioprinting of softer tissues and allows for improved control over degradation kinetics. We prepared amphiphilic macromonomers based on poloxamer that form hydrolysable, covalently cross-linked polymer networks. Dissolved at a concentration of 28.6%w/w in water, it functions as reinforcing gel, while a 5%w/w gelatin-methacryloyl based gel is utilized as bioink. This strategy allows for the creation of complex structures, where the bioink provides a cytocompatible environment for encapsulated cells. Cell viability of equine chondrocytes encapsulated within printed constructs remained largely unaffected by the printing process. The versatility of the system is further demonstrated by the ability to tune the stiffness of printed constructs between 138 and 263 kPa, as well as to tailor the degradation kinetics of the reinforcing gel from several weeks up to more than a year.
BibTeX:
@article{Melchels2016,
  author = {Ferry P W Melchels and Maarten M Blokzijl and Riccardo Levato and Quentin C Peiffer and Mylène de Ruijter and Wim E Hennink and Tina Vermonden and Jos Malda},
  title = {Hydrogel-based reinforcement of 3D bioprinted constructs},
  journal = {Biofabrication},
  year = {2016},
  volume = {8},
  number = {3},
  pages = {035004},
  url = {http://stacks.iop.org/1758-5090/8/i=3/a=035004}
}
Hou, X., Liu, S., Wang, M., Wiraja, C., Huang, W., Chan, P., Tan, T. and Xu, C. Layer-by-Layer 3D Constructs of Fibroblasts in Hydrogel for Examining Transdermal Penetration Capability of Nanoparticles 2016 Journal of Laboratory Automation  article DOI URL 
Abstract: Nanoparticles are emerging transdermal delivery systems. Their size and surface properties determine their efficacy and efficiency to penetrate through the skin layers. This work utilizes three-dimensional (3D) bioprinting technology to generate a simplified artificial skin model to rapidly screen nanoparticles for their transdermal penetration ability. Specifically, this model is built through layer-by-layer alternate printing of blank collagen hydrogel and fibroblasts. Through controlling valve on-time, the spacing between printing lines could be accurately tuned, which could enable modulation of cell infiltration in the future. To confirm the effectiveness of this platform, a 3D construct with one layer of fibroblasts sandwiched between two layers of collagen hydrogel is used to screen silica nanoparticles with different surface charges for their penetration ability, with positively charged nanoparticles demonstrating deeper penetration, consistent with the observation from an existing study involving living skin tissue.
BibTeX:
@article{Hou2016,
  author = {Hou, Xiaochun and Liu, Shiying and Wang, Min and Wiraja, Christian and Huang, Wei and Chan, Peggy and Tan, Timothy and Xu, Chenjie},
  title = {Layer-by-Layer 3D Constructs of Fibroblasts in Hydrogel for Examining Transdermal Penetration Capability of Nanoparticles},
  journal = {Journal of Laboratory Automation},
  year = {2016},
  url = {http://jla.sagepub.com/content/early/2016/06/18/2211068216655753.abstract},
  doi = {https://doi.org/10.1177/2211068216655753}
}
Hölzl, K., Lin, S., Tytgat, L., Vlierberghe, S.V., Gu, L. and Ovsianikov, A. Bioink properties before, during and after 3D bioprinting 2016 Biofabrication
Vol. 8(3), pp. 032002 
article URL 
Abstract: Bioprinting is a process based on additive manufacturing from materials containing living cells. These materials, often referred to as bioink, are based on cytocompatible hydrogel precursor formulations, which gel in a manner compatible with different bioprinting approaches. The bioink properties before, during and after gelation are essential for its printability, comprising such features as achievable structural resolution, shape fidelity and cell survival. However, it is the final properties of the matured bioprinted tissue construct that are crucial for the end application. During tissue formation these properties are influenced by the amount of cells present in the construct, their proliferation, migration and interaction with the material. A calibrated computational framework is able to predict the tissue development and maturation and to optimize the bioprinting input parameters such as the starting material, the initial cell loading and the construct geometry. In this contribution relevant bioink properties are reviewed and discussed on the example of most popular bioprinting approaches. The effect of cells on hydrogel processing and vice versa is highlighted. Furthermore, numerical approaches were reviewed and implemented for depicting the cellular mechanics within the hydrogel as well as for prediction of mechanical properties to achieve the desired hydrogel construct considering cell density, distribution and material–cell interaction.
BibTeX:
@article{Hoelzl2016,
  author = {Katja Hölzl and Shengmao Lin and Liesbeth Tytgat and Sandra Van Vlierberghe and Linxia Gu and Aleksandr Ovsianikov},
  title = {Bioink properties before, during and after 3D bioprinting},
  journal = {Biofabrication},
  year = {2016},
  volume = {8},
  number = {3},
  pages = {032002},
  url = {http://stacks.iop.org/1758-5090/8/i=3/a=032002}
}
Heinzelmann, E. Olten Meeting 2015 Antibiotics and Bioprinting for a better life 2016 CHIMIA International Journal for Chemistry
Vol. 70(1), pp. 112-115 
article DOI URL 
Abstract: The ever lurking danger of antibiotic resistance and the potential of bioprinting are on everyone's lips. But where do we stand in the battle against antibiotic-resistant pathogens? And what are the opportunities for biotech in the 3D printing of biological tissues and organs through the layering of living cells? At the Olten Meeting 2015 scientists and entrepreneurs met to throw light on the current situation.
BibTeX:
@article{Heinzelmann2016,
  author = {Heinzelmann, Elsbeth},
  title = {Olten Meeting 2015 Antibiotics and Bioprinting for a better life},
  journal = {CHIMIA International Journal for Chemistry},
  year = {2016},
  volume = {70},
  number = {1},
  pages = {112--115},
  url = {http://www.ingentaconnect.com/content/scs/chimia/2016/00000070/00000001/art00021},
  doi = {https://doi.org/10.2533/chimia.2016.112}
}
Håkansson, K.M.O., Henriksson, I.C., de la Peña Vázquez, C., Kuzmenko, V., Markstedt, K., Enoksson, P. and Gatenholm, P. Solidification of 3D Printed Nanofibril Hydrogels into Functional 3D Cellulose Structures 2016 Advanced Materials Technologies
Vol. 1(7), pp. 1600096-n/a 
article DOI  
Abstract: Cellulose nanofibrils isolated from trees have the potential to be used as raw material for future sustainable products within the areas of packaging, textiles, biomedical devices, and furniture. However, one unsolved problem has been to convert the nanofibril-hydrogel into a dry 3D structure. In this study, 3D printing is used to convert a cellulose nanofibril hydrogel into 3D structures with controlled architectures. Such structures collapse upon drying, but by using different drying processes the collapse can be controlled and the 3D structure can be preserved upon solidification. In addition, a conductive cellulose nanofibril ink is fabricated by adding carbon nanotubes. These findings enable the use of wood derived materials in 3D printing for fabrication of sustainable commodities such as packaging, textiles, biomedical devices, and furniture with conductive parts. Furthermore, with the introduction of biopolymers into 3D printing, the 3D printing technology itself can finally be regarded as sustainable.
BibTeX:
@article{Haakansson2016,
  author = {Håkansson, Karl M. O. and Henriksson, Ida C. and de la Peña Vázquez, Cristina and Kuzmenko, Volodymyr and Markstedt, Kajsa and Enoksson, Peter and Gatenholm, Paul},
  title = {Solidification of 3D Printed Nanofibril Hydrogels into Functional 3D Cellulose Structures},
  journal = {Advanced Materials Technologies},
  year = {2016},
  volume = {1},
  number = {7},
  pages = {1600096--n/a},
  note = {1600096},
  doi = {https://doi.org/10.1002/admt.201600096}
}
Gu, B.K., Choi, D.J., Park, S.J., Kim, M.S., Kang, C.M. and Kim, C.-H. 3-dimensional bioprinting for tissue engineering applications 2016 Biomaterials Research
Vol. 20(1), pp. 12 
article DOI  
Abstract: The 3-dimensional (3D) printing technologies, referred to as additive manufacturing (AM) or rapid prototyping (RP), have acquired reputation over the past few years for art, architectural modeling, lightweight machines, and tissue engineering applications. Among these applications, tissue engineering field using 3D printing has attracted the attention from many researchers. 3D bioprinting has an advantage in the manufacture of a scaffold for tissue engineering applications, because of rapid-fabrication, high-precision, and customized-production, etc. In this review, we will introduce the principles and the current state of the 3D bioprinting methods. Focusing on some of studies that are being current application for biomedical and tissue engineering fields using printed 3D scaffolds.
BibTeX:
@article{Gu2016,
  author = {Gu, Bon Kang and Choi, Dong Jin and Park, Sang Jun and Kim, Min Sup and Kang, Chang Mo and Kim, Chun-Ho},
  title = {3-dimensional bioprinting for tissue engineering applications},
  journal = {Biomaterials Research},
  year = {2016},
  volume = {20},
  number = {1},
  pages = {12},
  doi = {https://doi.org/10.1186/s40824-016-0058-2}
}
Gross, B., Lockwood, S.Y. and Spence, D.M. Recent Advances in Analytical Chemistry by 3D Printing 2016 Analytical Chemistry
Vol. 0(0) 
article DOI  
BibTeX:
@article{Gross2016,
  author = {Gross, Bethany and Lockwood, Sarah Y. and Spence, Dana M.},
  title = {Recent Advances in Analytical Chemistry by 3D Printing},
  journal = {Analytical Chemistry},
  year = {2016},
  volume = {0},
  number = {0},
  doi = {https://doi.org/10.1021/acs.analchem.6b04344}
}
Geven, M.A., Sprecher, C., Guillaume, O., Eglin, D. and Grijpma, D.W. Micro-porous composite scaffolds of photo-crosslinked poly(trimethylene carbonate) and nano-hydroxyapatite prepared by low-temperature extrusion-based additive manufacturing 2016 Polymers for Advanced Technologies  article DOI  
Abstract: Complex bony defects such as those of the orbital floor are challenging to repair. Additive manufacturing techniques open up possibilities for the fabrication of implants with a designed macro-porosity for the reconstruction of such defects. Apart from a designed macro-porosity for tissue ingrowth, a micro-porosity in the implant struts will be beneficial for nutrient diffusion, protein adsorption and drug loading and release. In this work, we report on a low-temperature extrusion-based additive manufacturing method for the preparation of composite photo-crosslinked structures of poly(trimethylene carbonate) with bone-forming nano-hydroxyapatite and noricaritin (derived from bone growth stimulating icariin). In this method, we extrude a dispersion of nano-hydroxyapatite and noricaritin particles in a solution of photo-crosslinkable poly(trimethylene carbonate) in ethylene carbonate into defined three-dimensional structures. The ethylene carbonate is subsequently crystallized and extracted after photo-crosslinking. We show that this results in designed macro-porous structures with micro-pores in the struts. The dispersion used to fabricate these structures shows favorable properties for extrusion-based processing, such as a sharp crystallization response and shear thinning. The formed photo-crosslinked materials have a micro-porosity of up to 48%, and the E modulus, ultimate tensile strength and toughness are in excess of 24 MPa, 2.0 N/mm2 and 113 N/mm2 respectively. A sustained release of noricaritin from these materials was also achieved. The results show that the technique described here is promising for the fabrication of micro-porous photo-crosslinked composite structures of poly(trimethylene carbonate) with nano-hydroxyapatite and that these may be applied in the reconstruction of orbital floor defects. Copyright © 2016 John Wiley & Sons, Ltd.
BibTeX:
@article{Geven2016,
  author = {Geven, Mike A. and Sprecher, Christoph and Guillaume, Olivier and Eglin, David and Grijpma, Dirk W.},
  title = {Micro-porous composite scaffolds of photo-crosslinked poly(trimethylene carbonate) and nano-hydroxyapatite prepared by low-temperature extrusion-based additive manufacturing},
  journal = {Polymers for Advanced Technologies},
  year = {2016},
  note = {PAT-16-382},
  doi = {https://doi.org/10.1002/pat.3890}
}
Daly, A.C., Cunniffe, G.M., Sathy, B.N., Jeon, O., Alsberg, E. and Kelly, D.J. 3D Bioprinting of Developmentally Inspired Templates for Whole Bone Organ Engineering 2016 Advanced Healthcare Materials
Vol. 5(18), pp. 2353-2362 
article DOI  
Abstract: The ability to print defined patterns of cells and extracellular-matrix components in three dimensions has enabled the engineering of simple biological tissues; however, bioprinting functional solid organs is beyond the capabilities of current biofabrication technologies. An alternative approach would be to bioprint the developmental precursor to an adult organ, using this engineered rudiment as a template for subsequent organogenesis in vivo. This study demonstrates that developmentally inspired hypertrophic cartilage templates can be engineered in vitro using stem cells within a supporting gamma-irradiated alginate bioink incorporating Arg-Gly-Asp adhesion peptides. Furthermore, these soft tissue templates can be reinforced with a network of printed polycaprolactone fibers, resulting in a ≈350 fold increase in construct compressive modulus providing the necessary stiffness to implant such immature cartilaginous rudiments into load bearing locations. As a proof-of-principal, multiple-tool biofabrication is used to engineer a mechanically reinforced cartilaginous template mimicking the geometry of a vertebral body, which in vivo supported the development of a vascularized bone organ containing trabecular-like endochondral bone with a supporting marrow structure. Such developmental engineering approaches could be applied to the biofabrication of other solid organs by bioprinting precursors that have the capacity to mature into their adult counterparts over time in vivo.
BibTeX:
@article{Daly2016,
  author = {Daly, Andrew C. and Cunniffe, Gráinne M. and Sathy, Binulal N. and Jeon, Oju and Alsberg, Eben and Kelly, Daniel J.},
  title = {3D Bioprinting of Developmentally Inspired Templates for Whole Bone Organ Engineering},
  journal = {Advanced Healthcare Materials},
  year = {2016},
  volume = {5},
  number = {18},
  pages = {2353--2362},
  doi = {https://doi.org/10.1002/adhm.201600182}
}
Daly, A.C., Critchley, S.E., Rencsok, E.M. and Kelly, D.J. A comparison of different bioinks for 3D bioprinting of fibrocartilage and hyaline cartilage 2016 Biofabrication
Vol. 8(4), pp. 045002 
article URL 
Abstract: Cartilage is a dense connective tissue with limited self-repair capabilities. Mesenchymal stem cell (MSC) laden hydrogels are commonly used for fibrocartilage and articular cartilage tissue engineering, however they typically lack the mechanical integrity for implantation into high load bearing environments. This has led to increased interested in 3D bioprinting of cell laden hydrogel bioinks reinforced with stiffer polymer fibres. The objective of this study was to compare a range of commonly used hydrogel bioinks (agarose, alginate, GelMA and BioINK™) for their printing properties and capacity to support the development of either hyaline cartilage or fibrocartilage in vitro . Each hydrogel was seeded with MSCs, cultured for 28 days in the presence of TGF- β 3 and then analysed for markers indicative of differentiation towards either a fibrocartilaginous or hyaline cartilage-like phenotype. Alginate and agarose hydrogels best supported the development of hyaline-like cartilage, as evident by the development of a tissue staining predominantly for type II collagen. In contrast, GelMA and BioINK ™ (a PEGMA based hydrogel) supported the development of a more fibrocartilage-like tissue, as evident by the development of a tissue containing both type I and type II collagen. GelMA demonstrated superior printability, generating structures with greater fidelity, followed by the alginate and agarose bioinks. High levels of MSC viability were observed in all bioinks post-printing (∼80%). Finally we demonstrate that it is possible to engineer mechanically reinforced hydrogels with high cell viability by co-depositing a hydrogel bioink with polycaprolactone filaments, generating composites with bulk compressive moduli comparable to articular cartilage. This study demonstrates the importance of the choice of bioink when bioprinting different cartilaginous tissues for musculoskeletal applications.
BibTeX:
@article{Daly2016a,
  author = {Andrew C Daly and Susan E Critchley and Emily M Rencsok and Daniel J Kelly},
  title = {A comparison of different bioinks for 3D bioprinting of fibrocartilage and hyaline cartilage},
  journal = {Biofabrication},
  year = {2016},
  volume = {8},
  number = {4},
  pages = {045002},
  url = {http://stacks.iop.org/1758-5090/8/i=4/a=045002}
}
Carrel, J., Wiskott, A., Scherrer, S. and Durual, S. Large Bone Vertical Augmentation Using a Three‐Dimensional Printed TCP/HA Bone Graft: A Pilot Study in Dog Mandible 2016 Clinical Implant Dentistry and Related Research
Vol. 18(6), pp. 1183-1192 
article DOI  
Abstract: Abstract Background Osteoflux is a three‐dimensional printed calcium phosphate porous structure for oral bone augmentation. It is a mechanically stable scaffold with a well‐defined interconnectivity and can be readily shaped to conform to the bone bed's morphology. Purpose An animal experiment is reported whose aim was to assess the performance and safety of the scaffold in promoting vertical growth of cortical bone in the mandible. Materials and methods Four three‐dimensional blocks (10 mm length, 5 mm width, 5 mm height) were affixed to edentulous segments of the dog's mandible and covered by a collagen membrane. During bone bed preparation, particular attention was paid not to create defects 0.5 mm or more so that the real potential of the three‐dimensional block in driving vertical bone growth can be assessed. Histomorphometric analyses were performed after 8 weeks. Results At 8 weeks, the three‐dimensional blocks led to substantial vertical bone growth up to 4.5 mm from the bone bed. Between 0 and 1 mm in height, 44% of the surface was filled with new bone, at 1 to 3 mm it was 20% to 35 18% at 3 to 4, and ca. 6% beyond 4 mm. New bone was evenly distributed along in mesio‐distal direction and formed a new crest contour in harmony with the natural mandibular shape. Conclusions After two months of healing, the three‐dimensional printed blocks conducted new bone growth above its natural bed, up to 4.5 mm in a canine mandibular model. Furthermore, the new bone was evenly distributed in height and density along the block. These results are very promising and need to be further evaluated by a complete powerful study using the same model.
BibTeX:
@article{Carrel2016,
  author = {Carrel, Jean‐Pierre and Wiskott, Anselm and Scherrer, Susanne and Durual, Stéphane},
  title = {Large Bone Vertical Augmentation Using a Three‐Dimensional Printed TCP/HA Bone Graft: A Pilot Study in Dog Mandible},
  journal = {Clinical Implant Dentistry and Related Research},
  year = {2016},
  volume = {18},
  number = {6},
  pages = {1183-1192},
  doi = {https://doi.org/10.1111/cid.12394}
}
Caetano, G., Violante, R., Sant’Ana, A.B., Murashima, A.B., Domingos, M., Gibson, A., Bártolo, P. and Frade, M.A. Cellularized versus decellularized scaffolds for bone regeneration 2016 Materials Letters
Vol. 182, pp. 318-322 
article DOI URL 
Abstract: Abstract An optimal scaffold based strategy for in vivo repair of large bone defects and its associated problems is presented in this work. Three polymeric scaffolds produced by using an extrusion-based additive manufacturing system were examined in a rat critical bone defect model: scaffolds without cells, with undifferentiated Adipose-derived mesenchymal stem cells (ADSCs) and differentiated ADSCs\ (osteoblasts). Scaffolds with undifferentiated cells seem to be the best strategy as they exhibited around 22% more bone formation than natural bone healing, and around 15% more than the two other cases. Authors observed that scaffolds enabled cell migration and tissue formation. Results suggest that undifferentiated ADSCs\ strongly contribute to new bone formation with no rejection if scaffolds are used to support cell migration, proliferation and differentiation. Our long-term goal is to engineer high-quality cell seeded-scaffolds (autograft and allograft) for bone regeneration, mainly in elderly patients.
BibTeX:
@article{Caetano2016,
  author = {Guilherme Caetano and Ricardo Violante and Ana Beatriz Sant’Ana and Adriana Batista Murashima and Marco Domingos and Andrew Gibson and Paulo Bártolo and Marco Andrey Frade},
  title = {Cellularized versus decellularized scaffolds for bone regeneration},
  journal = {Materials Letters},
  year = {2016},
  volume = {182},
  pages = {318--322},
  url = {http://www.sciencedirect.com/science/article/pii/S0167577X16309211},
  doi = {https://doi.org/10.1016/j.matlet.2016.05.152}
}
Ávila, H.M., Schwarz, S., Rotter, N. and Gatenholm, P. 3D bioprinting of human chondrocyte-laden nanocellulose hydrogels for patient-specific auricular cartilage regeneration 2016 Bioprinting
Vol. 1–2, pp. 22-35 
article DOI URL 
Abstract: Abstract Auricular cartilage tissue engineering (TE) aims to provide an effective treatment for patients with acquired or congenital auricular defects. Bioprinting has gained attention in several TE\ strategies for its ability to spatially control the placement of cells, biomaterials and biological molecules. Although considerable advances have been made to bioprint complex 3D tissue analogues, the development of hydrogel bioinks with good printability and bioactive properties must improve in order to advance the translation of 3D bioprinting into the clinic. In this study, the biological functionality of a bioink composed of nanofibrillated cellulose and alginate (NFC-A) is extensively evaluated for auricular cartilage TE. 3D bioprinted auricular constructs laden with human nasal chondrocytes (hNC) are cultured for up to 28 days and the redifferentiation capacity of hNCs in NFC-A is studied on gene expression as well as on protein levels. 3D bioprinting with NFC-A bioink facilitates the biofabrication of cell-laden, patient-specific auricular constructs with an open inner structure, high cell density and homogenous cell distribution. The cell-laden NFC-A constructs exhibit an excellent shape and size stability as well as an increase in cell viability and proliferation during in vitro culture. Furthermore, NFC-A bioink supports the redifferentiation of hNCs and neo-synthesis of cartilage-specific extracellular matrix components. This demonstrated that NFC-A bioink supports redifferentiation of hNCs while offering proper printability in a biologically relevant aqueous 3D environment, making it a promising tool for auricular cartilage TE\ and many other biomedical applications.
BibTeX:
@article{Avila2016,
  author = {Héctor Martínez Ávila and Silke Schwarz and Nicole Rotter and Paul Gatenholm},
  title = {3D bioprinting of human chondrocyte-laden nanocellulose hydrogels for patient-specific auricular cartilage regeneration},
  journal = {Bioprinting},
  year = {2016},
  volume = {1–2},
  pages = {22--35},
  url = {http://www.sciencedirect.com/science/article/pii/S2405886616300045},
  doi = {https://doi.org/10.1016/j.bprint.2016.08.003}
}
Arslan-Yildiz, A., Assal, R.E., Chen, P., Guven, S., Inci, F. and Demirci, U. Towards artificial tissue models: past, present, and future of 3D bioprinting 2016 Biofabrication
Vol. 8(1), pp. 014103 
article URL 
Abstract: Regenerative medicine and tissue engineering have seen unprecedented growth in the past decade, driving the field of artificial tissue models towards a revolution in future medicine. Major progress has been achieved through the development of innovative biomanufacturing strategies to pattern and assemble cells and extracellular matrix (ECM) in three-dimensions (3D) to create functional tissue constructs. Bioprinting has emerged as a promising 3D biomanufacturing technology, enabling precise control over spatial and temporal distribution of cells and ECM. Bioprinting technology can be used to engineer artificial tissues and organs by producing scaffolds with controlled spatial heterogeneity of physical properties, cellular composition, and ECM organization. This innovative approach is increasingly utilized in biomedicine, and has potential to create artificial functional constructs for drug screening and toxicology research, as well as tissue and organ transplantation. Herein, we review the recent advances in bioprinting technologies and discuss current markets, approaches, and biomedical applications. We also present current challenges and provide future directions for bioprinting research.
BibTeX:
@article{Arslan-Yildiz2016,
  author = {Ahu Arslan-Yildiz and Rami El Assal and Pu Chen and Sinan Guven and Fatih Inci and Utkan Demirci},
  title = {Towards artificial tissue models: past, present, and future of 3D bioprinting},
  journal = {Biofabrication},
  year = {2016},
  volume = {8},
  number = {1},
  pages = {014103},
  url = {http://stacks.iop.org/1758-5090/8/i=1/a=014103}
}
Abbadessa, A., Mouser, V.H.M., Blokzijl, M.M., Gawlitta, D., Dhert, W.J.A., Hennink, W.E., Malda, J. and Vermonden, T. A Synthetic Thermosensitive Hydrogel for Cartilage Bioprinting and Its Biofunctionalization with Polysaccharides 2016 Biomacromolecules
Vol. 17(6), pp. 2137-2147 
article DOI  
Abstract: Hydrogels based on triblock copolymers of polyethylene glycol and partially methacrylated poly[N-(2-hydroxypropyl) methacrylamide mono/dilactate] make up an attractive class of biomaterials because of their biodegradability, cytocompatibility, and tunable thermoresponsive and mechanical properties. If these properties are fine-tuned, the hydrogels can be three-dimensionally bioprinted, to generate, for instance, constructs for cartilage repair. This study investigated whether hydrogels based on the polymer mentioned above with a 10% degree of methacrylation (M10P10) support cartilage formation by chondrocytes and whether the incorporation of methacrylated chondroitin sulfate (CSMA) or methacrylated hyaluronic acid (HAMA) can improve the mechanical properties, long-term stability, and printability. Chondrocyte-laden M10P10 hydrogels were cultured for 42 days to evaluate chondrogenesis. M10P10 hydrogels with or without polysaccharides were evaluated for their mechanical properties (before and after UV photo-cross-linking), degradation kinetics, and printability. Extensive cartilage matrix production occurred in M10P10 hydrogels, highlighting their potential for cartilage repair strategies. The incorporation of polysaccharides increased the storage modulus of polymer mixtures and decreased the degradation kinetics in cross-linked hydrogels. Addition of HAMA to M10P10 hydrogels improved printability and resulted in three-dimensional constructs with excellent cell viability. Hence, this novel combination of M10P10 with HAMA forms an interesting class of hydrogels for cartilage bioprinting.
BibTeX:
@article{Abbadessa2016,
  author = {Abbadessa, Anna and Mouser, Vivian H. M. and Blokzijl, Maarten M. and Gawlitta, Debby and Dhert, Wouter J. A. and Hennink, Wim E. and Malda, Jos and Vermonden, Tina},
  title = {A Synthetic Thermosensitive Hydrogel for Cartilage Bioprinting and Its Biofunctionalization with Polysaccharides},
  journal = {Biomacromolecules},
  year = {2016},
  volume = {17},
  number = {6},
  pages = {2137--2147},
  note = {PMID: 27171342},
  doi = {https://doi.org/10.1021/acs.biomac.6b00366}
}
Abbadessa, A., Blokzijl, M., Mouser, V., Marica, P., Malda, J., Hennink, W. and Vermonden, T. A thermo-responsive and photo-polymerizable chondroitin sulfate-based hydrogel for 3D printing applications 2016 Carbohydrate Polymers
Vol. 149, pp. 163-174 
article DOI URL 
Abstract: Abstract The aim of this study was to design a hydrogel system based on methacrylated chondroitin sulfate (CSMA) and a thermo-sensitive poly(N-(2-hydroxypropyl) methacrylamide-mono/dilactate)-polyethylene glycol triblock copolymer (M15P10) as a suitable material for additive manufacturing of scaffolds. CSMA\ was synthesized by reaction of chondroitin sulfate with glycidyl methacrylate (GMA) in dimethylsulfoxide at 50 °C and its degree of methacrylation was tunable up to 48.5%, by changing reaction time and GMA\ feed. Unlike polymer solutions composed of CSMA\ alone (20% w/w), mixtures based on 2% w/w of CSMA\ and 18% of M15P10\ showed strain-softening, thermo-sensitive and shear-thinning properties more pronounced than those found for polymer solutions based on M15P10\ alone. Additionally, they displayed a yield stress of 19.2 ± 7.0 Pa. The 3D printing of this hydrogel resulted in the generation of constructs with tailorable porosity and good handling properties. Finally, embedded chondrogenic cells remained viable and proliferating over a culture period of 6 days. The hydrogel described herein represents a promising biomaterial for cartilage 3D printing applications.
BibTeX:
@article{Abbadessa2016a,
  author = {A. Abbadessa and M.M. Blokzijl and V.H.M. Mouser and P. Marica and J. Malda and W.E. Hennink and T. Vermonden},
  title = {A thermo-responsive and photo-polymerizable chondroitin sulfate-based hydrogel for 3D printing applications},
  journal = {Carbohydrate Polymers},
  year = {2016},
  volume = {149},
  pages = {163--174},
  url = {http://www.sciencedirect.com/science/article/pii/S014486171630457X},
  doi = {https://doi.org/10.1016/j.carbpol.2016.04.080}
}
Kokkinis, D., Schaffner, M. and Studart, A.R. Multimaterial magnetically assisted 3D printing of composite materials 2015 Nature Communications
Vol. 6, pp. 8643 
article DOI  
BibTeX:
@article{Kokkinis2015,
  author = {Kokkinis, Dimitri and Schaffner, Manuel and Studart, André R.},
  title = {Multimaterial magnetically assisted 3D printing of composite materials},
  journal = {Nature Communications},
  publisher = {The Author(s)},
  year = {2015},
  volume = {6},
  pages = {8643},
  doi = {https://doi.org/10.1038/ncomms9643}
}
Rimann, M., Bono, E., Annaheim, H., Bleisch, M. and Graf-Hausner, U. Standardized 3D Bioprinting of Soft Tissue Models with Human Primary Cells. 2015 Journal of laboratory automation
Vol. 21, pp. 496-509 
article DOI  
Abstract: Cells grown in 3D are more physiologically relevant than cells cultured in 2D. To use 3D models in substance testing and regenerative medicine, reproducibility and standardization are important. Bioprinting offers not only automated standardizable processes but also the production of complex tissue-like structures in an additive manner. We developed an all-in-one bioprinting solution to produce soft tissue models. The holistic approach included (1) a bioprinter in a sterile environment, (2) a light-induced bioink polymerization unit, (3) a user-friendly software, (4) the capability to print in standard labware for high-throughput screening, (5) cell-compatible inkjet-based printheads, (6) a cell-compatible ready-to-use BioInk, and (7) standard operating procedures. In a proof-of-concept study, skin as a reference soft tissue model was printed. To produce dermal equivalents, primary human dermal fibroblasts were printed in alternating layers with BioInk and cultured for up to 7 weeks. During long-term cultures, the models were remodeled and fully populated with viable and spreaded fibroblasts. Primary human dermal keratinocytes were seeded on top of dermal equivalents, and epidermis-like structures were formed as verified with hematoxylin and eosin staining and immunostaining. However, a fully stratified epidermis was not achieved. Nevertheless, this is one of the first reports of an integrative bioprinting strategy for industrial routine application.
BibTeX:
@article{Rimann2015a,
  author = {Rimann, Markus and Bono, Epifania and Annaheim, Helene and Bleisch, Matthias and Graf-Hausner, Ursula},
  title = {Standardized 3D Bioprinting of Soft Tissue Models with Human Primary Cells.},
  journal = {Journal of laboratory automation},
  year = {2015},
  volume = {21},
  pages = {496--509},
  doi = {https://doi.org/10.1177/2211068214567146}
}
Ho, C.M.B., Ng, S.H. and Yoon, Y.-J. A review on 3D printed bioimplants 2015 International Journal of Precision Engineering and Manufacturing
Vol. 16(5), pp. 1035-1046 
article DOI  
Abstract: Additive manufacturing (AM) also known as 3D printing have been making inroads into medical applications such as surgical models and tools, tooling equipment, medical devices. One key area researchers are looking into is bioimplants. With the improvement and development of AM technologies, many different bioimplants can be made using 3D printing. Different biomaterials and various AM technologies can be used to create customized bioimplants to suit the individual needs. With the aid of 3D printing this could lead to new foam and design of bioimplants in the near further. Therefore, the purpose of this review articles is to (1) Describe the various AM technologies and process used to make bioimplants, (2) Different types of bioimplants printed with AM and (3) Discuss some of the challenges and future developments for 3D printed bioimplants.
BibTeX:
@article{Ho2015,
  author = {Ho, Chee Meng Benjamin and Ng, Sum Huan and Yoon, Yong-Jin},
  title = {A review on 3D printed bioimplants},
  journal = {International Journal of Precision Engineering and Manufacturing},
  year = {2015},
  volume = {16},
  number = {5},
  pages = {1035--1046},
  doi = {https://doi.org/10.1007/s12541-015-0134-x}
}
Moussa, M., Carrel, J.-P., Scherrer, S., Cattani-Lorente, M., Wiskott, A. and Durual, S. Medium-Term Function of a 3D Printed TCP/HA Structure as a New Osteoconductive Scaffold for Vertical Bone Augmentation: A Simulation by BMP-2 Activation 2015 Materials
Vol. 8Materials, pp. 2174 
article DOI URL 
Abstract: Introduction: A 3D-printed construct made of orthogonally layered strands of tricalcium phosphate (TCP) and hydroxyapatite has recently become available. The material provides excellent osteoconductivity. We simulated a medium-term experiment in a sheep calvarial model by priming the blocks with BMP-2. Vertical bone growth/maturation and material resorption were evaluated. Materials and methods: Titanium hemispherical caps were filled with either bare- or BMP-2 primed constructs and placed onto the calvaria of adult sheep (n = 8). Histomorphometry was performed after 8 and 16 weeks. Results: After 8 weeks, relative to bare constructs, BMP-2 stimulation led to a two-fold increase in bone volume (Bare: 22% ± 2.1%; BMP-2 primed: 50% ± 3%) and a 3-fold decrease in substitute volume (Bare: 47% ± 5%; BMP-2 primed: 18% ± 2%). These rates were still observed at 16 weeks. The new bone grew and matured to a haversian-like structure while the substitute material resorbed via cell- and chemical-mediation. Conclusion: By priming the 3D construct with BMP-2, bone metabolism was physiologically accelerated, that is, enhancing vertical bone growth and maturation as well as material bioresorption. The scaffolding function of the block was maintained, leaving time for the bone to grow and mature to a haversian-like structure. In parallel, the material resorbed via cell-mediated and chemical processes. These promising results must be confirmed in clinical tests.
BibTeX:
@article{Moussa2015,
  author = {Moussa, Mira and Carrel, Jean-Pierre and Scherrer, Susanne and Cattani-Lorente, Maria and Wiskott, Anselm and Durual, Stéphane},
  title = {Medium-Term Function of a 3D Printed TCP/HA Structure as a New Osteoconductive Scaffold for Vertical Bone Augmentation: A Simulation by BMP-2 Activation},
  booktitle = {Materials},
  journal = {Materials},
  year = {2015},
  volume = {8},
  pages = {2174},
  url = {http://www.mdpi.com/1996-1944/8/5/2174},
  doi = {https://doi.org/10.3390/ma8052174}
}
Markstedt, K., Mantas, A., Tournier, I., Martínez Ávila, H., Hägg, D. and Gatenholm, P. 3D Bioprinting Human Chondrocytes with Nanocellulose-Alginate Bioink for Cartilage Tissue Engineering Applications 2015 Biomacromolecules
Vol. 16(5), pp. 1489-1496 
article DOI  
Abstract: The introduction of 3D bioprinting is expected to revolutionize the field of tissue engineering and regenerative medicine. The 3D bioprinter is able to dispense materials while moving in X, Y, and Z directions, which enables the engineering of complex structures from the bottom up. In this study, a bioink that combines the outstanding shear thinning properties of nanofibrillated cellulose (NFC) with the fast cross-linking ability of alginate was formulated for the 3D bioprinting of living soft tissue with cells. Printability was evaluated with concern to printer parameters and shape fidelity. The shear thinning behavior of the tested bioinks enabled printing of both 2D gridlike structures as well as 3D constructs. Furthermore, anatomically shaped cartilage structures, such as a human ear and sheep meniscus, were 3D printed using MRI and CT images as blueprints. Human chondrocytes bioprinted in the noncytotoxic, nanocellulose-based bioink exhibited a cell viability of 73% and 86% after 1 and 7 days of 3D culture, respectively. On the basis of these results, we can conclude that the nanocellulose-based bioink is a suitable hydrogel for 3D bioprinting with living cells. This study demonstrates the potential use of nanocellulose for 3D bioprinting of living tissues and organs.
The introduction of 3D bioprinting is expected to revolutionize the field of tissue engineering and regenerative medicine. The 3D bioprinter is able to dispense materials while moving in X, Y, and Z directions, which enables the engineering of complex structures from the bottom up. In this study, a bioink that combines the outstanding shear thinning properties of nanofibrillated cellulose (NFC) with the fast cross-linking ability of alginate was formulated for the 3D bioprinting of living soft tissue with cells. Printability was evaluated with concern to printer parameters and shape fidelity. The shear thinning behavior of the tested bioinks enabled printing of both 2D gridlike structures as well as 3D constructs. Furthermore, anatomically shaped cartilage structures, such as a human ear and sheep meniscus, were 3D printed using MRI and CT images as blueprints. Human chondrocytes bioprinted in the noncytotoxic, nanocellulose-based bioink exhibited a cell viability of 73% and 86% after 1 and 7 days of 3D culture, respectively. On the basis of these results, we can conclude that the nanocellulose-based bioink is a suitable hydrogel for 3D bioprinting with living cells. This study demonstrates the potential use of nanocellulose for 3D bioprinting of living tissues and organs.
BibTeX:
@article{Markstedt2015,
  author = {Markstedt, Kajsa and Mantas, Athanasios and Tournier, Ivan and Martínez Ávila, Héctor and Hägg, Daniel and Gatenholm, Paul},
  title = {3D Bioprinting Human Chondrocytes with Nanocellulose-Alginate Bioink for Cartilage Tissue Engineering Applications},
  journal = {Biomacromolecules},
  publisher = {American Chemical Society},
  year = {2015},
  volume = {16},
  number = {5},
  pages = {1489--1496},
  doi = {https://doi.org/10.1021/acs.biomac.5b00188}
}
Knoll, S. Niere aus dem Drucker? Sag niemals nie 2015 Medizin&Technik
Vol. 01(02), pp. 44-47 
article URL 
Abstract: Auch wenn der Hype darum groß ist und das Potenzial ebenfalls: Bioprinting – also die additive Herstellung von menschlichem Gewebe – steckt noch in den Kinderschuhen. Zu wenig standardisiert sind Maschinen, Verfahren und Biomaterialien.
BibTeX:
@article{Knoll2015,
  author = {Sabine Knoll},
  title = {Niere aus dem Drucker? Sag niemals nie},
  journal = {Medizin&Technik},
  year = {2015},
  volume = {01},
  number = {02},
  pages = {44--47},
  url = {http://size.lehmanns.de/artikel/8819630-Medizin-Technik}
}
Rimann, M., Laternser, S., Keller, H., Leupin, O. and Graf-Hausner, U. 3D Bioprinted Muscle and Tendon Tissues for Drug Development 2015 CHIMIA International Journal for Chemistry
Vol. 69(1), pp. 65-67 
article DOI  
BibTeX:
@article{Rimann2015,
  author = {Markus Rimann and Sandra Laternser and Hansjörg Keller and Olivier Leupin and Ursula Graf-Hausner},
  title = {3D Bioprinted Muscle and Tendon Tissues for Drug Development},
  journal = {CHIMIA International Journal for Chemistry},
  publisher = {Swiss Chemical Society},
  year = {2015},
  volume = {69},
  number = {1},
  pages = {65--67},
  doi = {https://doi.org/10.2533/chimia.2015.65}
}
Horvath, L., Umehara, Y., Jud, C., Blank, F., Petri-Fink, A. and Rothen-Rutishauser, B. Engineering an in vitro air-blood barrier by 3D bioprinting. 2015 Scientific reports
Vol. 5, pp. 7974 
article  
Abstract: Intensive efforts in recent years to develop and commercialize in vitro alternatives in the field of risk assessment have yielded new promising two- and three dimensional (3D) cell culture models. Nevertheless, a realistic 3D in vitro alveolar model is not available yet. Here we report on the biofabrication of the human air-blood tissue barrier analogue composed of an endothelial cell, basement membrane and epithelial cell layer by using a bioprinting technology. In contrary to the manual method, we demonstrate that this technique enables automatized and reproducible creation of thinner and more homogeneous cell layers, which is required for an optimal air-blood tissue barrier. This bioprinting platform will offer an excellent tool to engineer an advanced 3D lung model for high-throughput screening for safety assessment and drug efficacy testing.
BibTeX:
@article{Horvath2015,
  author = {Horvath, Lenke and Umehara, Yuki and Jud, Corinne and Blank, Fabian and Petri-Fink, Alke and Rothen-Rutishauser, Barbara},
  title = {Engineering an in vitro air-blood barrier by 3D bioprinting.},
  journal = {Scientific reports},
  year = {2015},
  volume = {5},
  pages = {7974}
}
Tan, E.Y.S. and Yeong, W.Y. Concentric bioprinting of alginate-based tubular constructs using multi-nozzle extrusion-based technique 2015 International Journal of Bioprinting
Vol. 1, pp. 49-56 
article  
Abstract: Bioprinting is a layer-by-layer additive fabrication technique for making three-dimensional (3D) tissue and organ constructs using biological products. The capability to fabricate 3D tubular structure in free-form or vertical configuration is the first step towards the possibility of organ printing in three dimensions. In this study, alginate-based tubular structures of varying viscosity were printed vertically using multi-nozzle extrusion-based technique. Manufacturing challenges associated with the vertical printing configurations are also discussed here. We have also proposed measurable parameters to quantify the quality of printing for systematic investigation in bioprinting. This study lays a foundation for the successful fabrication of viable 3D tubular constructs.
BibTeX:
@article{Tan2015,
  author = {Tan, Edgar Y. S. and Yeong, Wai Yee},
  title = {Concentric bioprinting of alginate-based tubular constructs using multi-nozzle extrusion-based technique},
  journal = {International Journal of Bioprinting},
  year = {2015},
  volume = {1},
  pages = {49--56}
}
Schuddeboom, M. Biofabrication of Perfusable Liver Constructs 2015 School: Utrecht University - Faculty of Veterinary Medicine  mastersthesis URL 
BibTeX:
@mastersthesis{Schuddeboom2015,
  author = {Schuddeboom, Monique},
  title = {Biofabrication of Perfusable Liver Constructs},
  school = {Utrecht University - Faculty of Veterinary Medicine},
  year = {2015},
  url = {https://dspace.library.uu.nl/handle/1874/322746}
}
Schacht, K., Jüngst, T., Schweinlin, M., Ewald, A., Groll, J. and Scheibel, T. Biofabrication of Cell-Loaded 3D Spider Silk Constructs 2015 Angewandte Chemie International Edition
Vol. 54(9), pp. 2816-2820 
article DOI  
Abstract: Biofabrication is an emerging and rapidly expanding field of research in which additive manufacturing techniques in combination with cell printing are exploited to generate hierarchical tissue-like structures. Materials that combine printability with cytocompatibility, so called bioinks, are currently the biggest bottleneck. Since recombinant spider silk proteins are non-immunogenic, cytocompatible, and exhibit physical crosslinking, their potential as a new bioink system was evaluated. Cell-loaded spider silk constructs can be printed by robotic dispensing without the need for crosslinking additives or thickeners for mechanical stabilization. Cells are able to adhere and proliferate with good viability over at least one week in such spider silk scaffolds. Introduction of a cell-binding motif to the spider silk protein further enables fine-tuned control over cell–material interactions. Spider silk hydrogels are thus a highly attractive novel bioink for biofabrication.
BibTeX:
@article{Schacht2015,
  author = {Schacht, Kristin and Jüngst, Tomasz and Schweinlin, Matthias and Ewald, Andrea and Groll, Jürgen and Scheibel, Thomas},
  title = {Biofabrication of Cell-Loaded 3D Spider Silk Constructs},
  journal = {Angewandte Chemie International Edition},
  publisher = {WILEY-VCH Verlag},
  year = {2015},
  volume = {54},
  number = {9},
  pages = {2816--2820},
  doi = {https://doi.org/10.1002/anie.201409846}
}
Müller, M., Becher, J., Schnabelrauch, M. and Zenobi-Wong, M. Nanostructured Pluronic hydrogels as bioinks for 3D bioprinting 2015 Biofabrication
Vol. 7(3), pp. 035006 
article URL 
Abstract: Bioprinting is an emerging technology in the field of tissue engineering as it allows the precise positioning of biologically relevant materials in 3D, which more resembles the native tissue in our body than current homogenous, bulk approaches. There is however a lack of materials to be used with this technology and materials such as the block copolymer Pluronic have good printing properties but do not allow long-term cell culture. Here we present an approach called nanostructuring to increase the biocompatibility of Pluronic gels at printable concentrations. By mixing acrylated with unmodified Pluronic F127 it was possible to maintain the excellent printing properties of Pluronic and to create stable gels via UV crosslinking. By subsequent elution of the unmodified Pluronic from the crosslinked network we were able to increase the cell viability of encapsulated chondrocytes at day 14 from 62% for a pure acrylated Pluronic hydrogel to 86% for a nanostructured hydrogel. The mixed Pluronic gels also showed good printability when cells where included in the bioink. The nanostructured gels were, with a compressive modulus of 1.42 kPa, mechanically weak, but we were able to increase the mechanical properties by the addition of methacrylated hyaluronic acid. Our nanostructuring approach enables Pluronic hydrogels to have the desired set of properties in all stages of the bioprinting process.
BibTeX:
@article{Mueller2015,
  author = {Michael Müller and Jana Becher and Matthias Schnabelrauch and Marcy Zenobi-Wong},
  title = {Nanostructured Pluronic hydrogels as bioinks for 3D bioprinting},
  journal = {Biofabrication},
  year = {2015},
  volume = {7},
  number = {3},
  pages = {035006},
  url = {http://stacks.iop.org/1758-5090/7/i=3/a=035006}
}
Khaled, S.A., Burley, J.C., Alexander, M.R., Yang, J. and Roberts, C.J. 3D printing of tablets containing multiple drugs with defined release profiles 2015 International Journal of Pharmaceutics
Vol. 494(2), pp. 643-650 
article DOI URL 
Abstract: Abstract We have employed three-dimensional (3D) extrusion-based printing as a medicine manufacturing technique for the production of multi-active tablets with well-defined and separate controlled release profiles for three different drugs. This ‘polypill’ made by a 3D additive manufacture technique demonstrates that complex medication regimes can be combined in a single tablet and that it is viable to formulate and ‘dial up’ this single tablet for the particular needs of an individual. The tablets used to illustrate this concept incorporate an osmotic pump with the drug captopril and sustained release compartments with the drugs nifedipine and glipizide. This combination of medicines could potentially be used to treat diabetics suffering from hypertension. The room temperature extrusion process used to print the formulations used excipients commonly employed in the pharmaceutical industry. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and X-ray powder diffraction (XRPD) were used to assess drug–excipient interaction. The printed formulations were evaluated for drug release using USP\ dissolution testing. We found that the captopril portion showed the intended zero order drug release of an osmotic pump and noted that the nifedipine and glipizide portions showed either first order release or Korsmeyer–Peppas release kinetics dependent upon the active/excipient ratio used.
BibTeX:
@article{Khaled2015,
  author = {Shaban A. Khaled and Jonathan C. Burley and Morgan R. Alexander and Jing Yang and Clive J. Roberts},
  title = {3D printing of tablets containing multiple drugs with defined release profiles},
  journal = {International Journal of Pharmaceutics},
  year = {2015},
  volume = {494},
  number = {2},
  pages = {643--650},
  note = {The potential for 2D and 3D Printing to Pharmaceutical Development},
  url = {http://www.sciencedirect.com/science/article/pii/S0378517315300855},
  doi = {https://doi.org/10.1016/j.ijpharm.2015.07.067}
}
Khaled, S.A., Burley, J.C., Alexander, M.R., Yang, J. and Roberts, C.J. 3D printing of five-in-one dose combination polypill with defined immediate and sustained release profiles 2015 Journal of Controlled Release
Vol. 217, pp. 308-314 
article DOI URL 
Abstract: Abstract We have used three dimensional (3D) extrusion printing to manufacture a multi-active solid dosage form or so called polypill. This contains five compartmentalised drugs with two independently controlled and well-defined release profiles. This polypill demonstrates that complex medication regimes can be combined in a single personalised tablet. This could potentially improve adherence for those patients currently taking many separate tablets and also allow ready tailoring of a particular drug combination/drug release for the needs of an individual. The polypill here represents a cardiovascular treatment regime with the incorporation of an immediate release compartment with aspirin and hydrochlorothiazide and three sustained release compartments containing pravastatin, atenolol, and ramipril. X-ray powder diffraction (XRPD) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) were used to assess drug-excipient interaction. The printed polypills were evaluated for drug release using USP\ dissolution testing. We found that the polypill showed the intended immediate and sustained release profiles based upon the active/excipient ratio used.
BibTeX:
@article{Khaled2015a,
  author = {Shaban A. Khaled and Jonathan C. Burley and Morgan R. Alexander and Jing Yang and Clive J. Roberts},
  title = {3D printing of five-in-one dose combination polypill with defined immediate and sustained release profiles},
  journal = {Journal of Controlled Release},
  year = {2015},
  volume = {217},
  pages = {308--314},
  url = {http://www.sciencedirect.com/science/article/pii/S0168365915301292},
  doi = {https://doi.org/10.1016/j.jconrel.2015.09.028}
}
Kesti, M., Eberhardt, C., Pagliccia, G., Kenkel, D., Grande, D., Boss, A. and Zenobi-Wong, M. Bioprinting Complex Cartilaginous Structures with Clinically Compliant Biomaterials 2015 Advanced Functional Materials
Vol. 25(48), pp. 7406-7417 
article DOI  
Abstract: Bioprinting is an emerging technology for the fabrication of patient-specific, anatomically complex tissues and organs. A novel bioink for printing cartilage grafts is developed based on two unmodified FDA-compliant polysaccharides, gellan and alginate, combined with the clinical product BioCartilage (cartilage extracellular matrix particles). Cell-friendly physical gelation of the bioink occurs in the presence of cations, which are delivered by co-extrusion of a cation-loaded transient support polymer to stabilize overhanging structures. Rheological properties of the bioink reveal optimal shear thinning and shear recovery properties for high-fidelity bioprinting. Tensile testing of the bioprinted grafts reveals a strong, ductile material. As proof of concept, 3D auricular, nasal, meniscal, and vertebral disk grafts are printed based on computer tomography data or generic 3D models. Grafts after 8 weeks in vitro are scanned using magnetic resonance imaging and histological evaluation is performed. The bioink containing BioCartilage supports proliferation of chondrocytes and, in the presence of transforming growth factor beta-3, supports strong deposition of cartilage matrix proteins. A clinically compliant bioprinting method is presented which yields patient-specific cartilage grafts with good mechanical and biological properties. The versatile method can be used with any type of tissue particles to create tissue-specific and bioactive scaffolds.
BibTeX:
@article{Kesti2015,
  author = {Kesti, Matti and Eberhardt, Christian and Pagliccia, Guglielmo and Kenkel, David and Grande, Daniel and Boss, Andreas and Zenobi-Wong, Marcy},
  title = {Bioprinting Complex Cartilaginous Structures with Clinically Compliant Biomaterials},
  journal = {Advanced Functional Materials},
  year = {2015},
  volume = {25},
  number = {48},
  pages = {7406--7417},
  doi = {https://doi.org/10.1002/adfm.201503423}
}
Hockaday, L. 3D Bioprinting: A Deliberate Business 2015 Genetic Engineering & Biotechnology News
Vol. 35(1), pp. 14-17 
article DOI  
BibTeX:
@article{Hockaday2015,
  author = {Hockaday, Laura},
  title = {3D Bioprinting: A Deliberate Business},
  journal = {Genetic Engineering & Biotechnology News},
  year = {2015},
  volume = {35},
  number = {1},
  pages = {14-17},
  doi = {https://doi.org/10.1089/gen.35.01.09}
}
Graf-Hausner, U., Rimann, M., Bono, E., Laternser, S. and Bleisch, M. A novel multiwell device for drug development with bioprinted 3D human tendon and skeletal muscle tissues 2015   poster URL 
Abstract: There is a huge medical need for treatments of degenerative muscle and tendon diseases in our aging societies. Currently, there are no approved pharmaceutical therapies. A key component of successful drug development is the availability of organotypic cell culture disease models for efficient physiological compound screening. 3D Bioprinting is a new technology for the in vitro engineering of human living tissue using a 3D printer. We intend to develop a novel multiwell tissue culture system consisting of bioprinted human skeletal muscle and tendon tissues anchored between intelligent posts that allow mechanical stimulation and functional analysis. This system may also at least partially replace animal-based ex vivo muscle and tendon assays
BibTeX:
@poster{Graf-Hausner2015,
  author = {Graf-Hausner, Ursula and Rimann, Markus and Bono, Epifania and Laternser, Sandra and Bleisch, Matthias},
  title = {A novel multiwell device for drug development with bioprinted 3D human tendon and skeletal muscle tissues},
  year = {2015},
  url = {https://pd.zhaw.ch/publikation/upload/210958.pdf}
}
Chee Kai Chua, K.F.L. 3D Printing and Additive Manufacturing 2014   book URL 
BibTeX:
@book{CheeKaiChua2014,
  author = {Chee Kai Chua, Kah Fai Leong},
  title = {3D Printing and Additive Manufacturing},
  publisher = {World Scientific Publishing Company},
  year = {2014},
  url = {http://www.ebook.de/de/product/21845333/chee_kai_chua_kah_fai_leong_3d_printing_and_additive_manufacturing.html}
}
Rimann, M. and Graf-Hausner, U. Bioprinting und in vitro-Modelle zur Wirkstoffentwicklung 2014   poster URL 
Abstract: Die dreidimensionale (3D) Zellkultur liefert neuartige organähnliche Gewebemodelle, welche den dringenden Bedarf an relevanten in vitro-Testsystemen für die Wirkstoffentwicklung und Substanzprüf ung zu decken versuchen. Die innovative Bioprinting­Technologie zeigt das Potential am Beispiel eines humanen Muskel / Sehnen­Modells. Der hohe Stellenwert dieser 3D­Modelle für Forschung und Industrie widerspiegelte sich auch in der Rekordbeteiligung der diesjährigen Jahresversammlung des Kompetenzzentrums TEDD (Tissue Engineering for Drug Development).
BibTeX:
@poster{Rimann2014,
  author = {Rimann, Markus and Graf-Hausner, Ursula},
  title = {Bioprinting und in vitro-Modelle zur Wirkstoffentwicklung},
  year = {2014},
  url = {https://www.zhaw.ch/storage/lsfm/forschung/transfer/2014-3-icbc.pdf}
}
Markstedt, K., Tournier, I., Mantas, A., Hägg, D. and Gatenholm, P. 3D BIOPRINTING OF LIVING TISSUE WITH NANOCELLULOSE “INK”- CELLINK 2014   poster  
Abstract: The introduction of 3D bioprinting is expected to revolutionize the field of tissue engineering and regenerative medicine, which enables the reconstruction of living tissue and organs preferably using the patient’s own cells. This project aims at developing a new supporting material, CELLINK, for printing living tissue with cells. CELLINK is composed of a nanofibrillated cellulose dispersion and alginate, which is crosslinked during printing. Cytotoxicity and cell viability have been tested in order to print CELLINK with living cells. 3D shapes with complex architecture have been printed with human chondrocytes in one step procedure. More than 95%cell viability was registered 6 days after printing.
BibTeX:
@poster{Markstedt2014,
  author = {Markstedt, Kajsa and Tournier, Ivan and Mantas, Athanasios and Hägg, Daniel and Gatenholm, Paul},
  title = {3D BIOPRINTING OF LIVING TISSUE WITH NANOCELLULOSE “INK”- CELLINK},
  year = {2014}
}
Kesti, M., Müller, M., Becher, J., Schnabelrauch, M., D’Este, M., Eglin, D. and Zenobi-Wong, M. A versatile bioink for three-dimensional printing of cellular scaffolds based on thermally and photo-triggered tandem gelation 2014 Acta Biomaterialia
Vol. 11, pp. 162-172 
article DOI URL 
Abstract: Abstract Layer-by-layer bioprinting is a logical choice for the fabrication of stratified tissues like articular cartilage. Printing of viable organ replacements, however, is dependent on bioinks with appropriate rheological and cytocompatible properties. In cartilage engineering, photocrosslinkable glycosaminoglycan-based hydrogels are chondrogenic, but alone have generally poor printing properties. By blending the thermoresponsive polymer poly(N-isopropylacrylamide) grafted hyaluronan (HA-pNIPAAM) with methacrylated hyaluronan (HAMA), high-resolution scaffolds with good viability were printed. HA-pNIPAAM provided fast gelation and immediate post-printing structural fidelity, while HAMA\ ensured long-term mechanical stability upon photocrosslinking. The bioink was evaluated for rheological properties, swelling behavior, printability and biocompatibility of encapsulated bovine chondrocytes. Elution of HA-pNIPAAM from the scaffold was necessary to obtain good viability. HA-pNIPAAM can therefore be used to support extrusion of a range of biopolymers which undergo tandem gelation, thereby facilitating the printing of cell-laden, stratified cartilage constructs with zonally varying composition and stiffness.
BibTeX:
@article{Kesti2014,
  author = {Matti Kesti and Michael Müller and Jana Becher and Matthias Schnabelrauch and Matteo D’Este and David Eglin and Marcy Zenobi-Wong},
  title = {A versatile bioink for three-dimensional printing of cellular scaffolds based on thermally and photo-triggered tandem gelation},
  journal = {Acta Biomaterialia},
  year = {2014},
  volume = {11},
  pages = {162--172},
  url = {http://www.sciencedirect.com/science/article/pii/S1742706114004243},
  doi = {https://doi.org/10.1016/j.actbio.2014.09.033}
}
Carrel, J.-P., Wiskott, A., Moussa, M., Rieder, P., Scherrer, S. and Durual, S. A 3D printed TCP/HA structure as a new osteoconductive scaffold for vertical bone augmentation 2014 Clinical Oral Implants Research
Vol. 27(1), pp. 55-62 
article DOI  
Abstract:
Introduction
OsteoFlux® (OF) is a 3D printed porous block of layered strands of tricalcium phosphate (TCP) and hydroxyapatite. Its porosity and interconnectivity are defined, and it can be readily shaped to conform the bone bed's morphology. We investigated the performance of OF as a scaffold to promote the vertical growth of cortical bone in a sheep calvarial model.

Materials and methods
Six titanium hemispheres were filled with OF, Bio-Oss (particulate bovine bone, BO), or Ceros (particulate TCP, CO) and placed onto the calvaria of 12 adult sheep (6 hemispheres/sheep). Histomorphometric analyses were performed after 8 and 16 weeks.

Results
OF led to substantial vertical bone growth by 8 weeks and outperformed BO and CO by a factor 2 yielding OF 22% ± 2.1; BO 11.5% ± 1.9; and CO 12.9% ± 2.1 total new bone. 3 mm away from the bony bed, OF led to a fourfold increase in new bone relative to BO and CO (n = 8, P < 0.002). At 16 weeks, OF, BO, and CO behaved similarly and showed marked new bone synthesis. A moderate degradation was observed at 16 weeks for all bone substitutes.

Conclusion
When compared to existing bone substitutes, OF enhances vertical bone growth during the first 2 months after implantation in a sheep calvarial model. The controlled porous structure translated in a high osteoconductivity and resulted in a bone mass 3 mm above the bony bed that was four times greater than that obtained with standard substitutes. These results are promising but must be confirmed in clinical tests.
BibTeX:
@article{Carrel2014,
  author = {Carrel, Jean-Pierre and Wiskott, Anselm and Moussa, Mira and Rieder, Philippe and Scherrer, Susanne and Durual, Stéphane},
  title = {A 3D printed TCP/HA structure as a new osteoconductive scaffold for vertical bone augmentation},
  journal = {Clinical Oral Implants Research},
  year = {2014},
  volume = {27},
  number = {1},
  pages = {55--62},
  doi = {https://doi.org/10.1111/clr.12503}
}
Rezende, R.A., Selishchev, S.V., Kasyanov, V.A., da Silva, J.V.L. and Mironov, V.A. An Organ Biofabrication Line: Enabling Technology for Organ Printing. Part II: from Encapsulators to Biofabrication Line 2013 Biomedical Engineering
Vol. 47(4), pp. 213-218 
article DOI  
Abstract: The first part of this review was published in Biomedical Engineering, No. 3, 2013. This second part discusses development and application of tissue spheroid encapsulators, robotics bioprinters, bioreactors, and problems of computer design of biofabrication lines.
BibTeX:
@article{Rezende2013,
  author = {Rezende, R. A. and Selishchev, S. V. and Kasyanov, V. A. and da Silva, J. V. L. and Mironov, V. A.},
  title = {An Organ Biofabrication Line: Enabling Technology for Organ Printing. Part II: from Encapsulators to Biofabrication Line},
  journal = {Biomedical Engineering},
  year = {2013},
  volume = {47},
  number = {4},
  pages = {213--218},
  doi = {https://doi.org/10.1007/s10527-013-9374-1}
}
Müller, M., Becher, J., Schnabelrauch, M. and Zenobi-Wong, M. Printing thermoresponsive reverse molds for the creation of patterned two-component hydrogels for 3D cell culture. 2013 Journal of visualized experiments : JoVE, pp. 1-9  article URL 
Abstract: Bioprinting is an emerging technology that has its origins in the rapid prototyping industry. The different printing processes can be divided into contact bioprinting(1-4) (extrusion, dip pen and soft lithography), contactless bioprinting(5-7) (laser forward transfer, ink-jet deposition) and laser based techniques such as two photon photopolymerization(8). It can be used for many applications such as tissue engineering(9-13), biosensor microfabrication(14-16) and as a tool to answer basic biological questions such as influences of co-culturing of different cell types(17). Unlike common photolithographic or soft-lithographic methods, extrusion bioprinting has the advantage that it does not require a separate mask or stamp. Using CAD software, the design of the structure can quickly be changed and adjusted according to the requirements of the operator. This makes bioprinting more flexible than lithography-based approaches. Here we demonstrate the printing of a sacrificial mold to create a multi-material 3D structure using an array of pillars within a hydrogel as an example. These pillars could represent hollow structures for a vascular network or the tubes within a nerve guide conduit. The material chosen for the sacrificial mold was poloxamer 407, a thermoresponsive polymer with excellent printing properties which is liquid at 4 degrees C and a solid above its gelation temperature  20 degrees C for 24.5% w/v solutions(18). This property allows the poloxamer-based sacrificial mold to be eluted on demand and has advantages over the slow dissolution of a solid material especially for narrow geometries. Poloxamer was printed on microscope glass slides to create the sacrificial mold. Agarose was pipetted into the mold and cooled until gelation. After elution of the poloxamer in ice cold water, the voids in the agarose mold were filled with alginate methacrylate spiked with FITC labeled fibrinogen. The filled voids were then cross-linked with UV and the construct was imaged with an epi-fluorescence microscope.
BibTeX:
@article{Mueller2013,
  author = {Müller, Michael and Becher, Jana and Schnabelrauch, Matthias and Zenobi-Wong, Marcy},
  title = {Printing thermoresponsive reverse molds for the creation of patterned two-component hydrogels for 3D cell culture.},
  journal = {Journal of visualized experiments : JoVE},
  year = {2013},
  pages = {1--9},
  url = {https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3732096/}
}
RegenHU Product information: 3D organomimetic models for tissue engineering 2013 Biotechnology Journal
Vol. 8(3), pp. 283-283 
article DOI  
BibTeX:
@article{Productinformation2013,
  author = {RegenHU},
  title = {Product information: 3D organomimetic models for tissue engineering},
  journal = {Biotechnology Journal},
  publisher = {WILEY-VCH Verlag},
  year = {2013},
  volume = {8},
  number = {3},
  pages = {283--283},
  doi = {https://doi.org/10.1002/biot.201300048}
}
Müller, M., Studer, D., Maniura-Weber, K. and Zenobi-Wong, M. Novel bioprinted co-culture system fro investigating chondrogenesis 2012   poster  
BibTeX:
@poster{Mueller2012,
  author = {Michael Müller and Deborah Studer and Katharina Maniura-Weber and Marcy Zenobi-Wong},
  title = {Novel bioprinted co-culture system fro investigating chondrogenesis},
  year = {2012}
}
Graf-Hausner, U., Rimann, M. and Annaheim, H. Skin Bioprinting: an innovative approach to produce standardized skin models on demand 2012   poster URL 
Abstract: In the cosmetic industry the testing of cosmetic ingredients on animals is no longer tolerated as soon as appropriate in vitro skin test systems are available. Therefore artificial in vitro skin models are urgently needed. So far, skin model supplier use standard liquid handling robots to manufacture their product leading to very simple composed skin equivalents. In a previous CTI project (CTI No.: 12148.2) we used the upcoming bioprinting technology to print a dermal equivalent in a layer by layer fashion. With alternating layers of Bioink (matrix) and fibroblasts in suspension the tissue was formed. This technique allows the creation of a biological composite system by controlling the exact deposition of cells, growth factors and extracellular matrix (ECM) molecules in a spatiallycontrolled manner. In the frame of the former CTI-project a bioink was developed, which is printable, cyto-compatible and photo-polymerizable serving as a matrix to build up the tissue. Furthermore, an in situ quality control was integrated using an OCT-system. Figure 1 shows the bioprinter (BioFactory) and the printing mode.
BibTeX:
@poster{Graf-Hausner2012,
  author = {Graf-Hausner, Ursula and Rimann, Markus and Annaheim, Helene},
  title = {Skin Bioprinting: an innovative approach to produce standardized skin models on demand},
  year = {2012},
  url = {http://www.optolab.ti.bfh.ch/media/content/optolab/documents/2012/10/Bioink_poster_CTI_Medtech_event.pdf}
}
Bleisch, M., Kuster, M., Thurner, M., Meier, C., Bossen, A. and Graf-Hausner, U. Organomimetic skin model production based on a novel bioprinting technology 2012   poster URL 
Abstract: In march 2009, the EU commission has introduced new directives. A directive, that foresees a regulatory framework with the aim of phasing out animal testing. It establishes a prohibition to test finished cosmetic products and cosmetic ingredients on animals (testing ban), and a prohibition to market in the European Community of finished cosmetic products and ingredients included in cosmetic products which were tested on animals (marketing ban). Thus, there is an urgent demand by the cosmetic industry for standardized and customized artificial organomimetic skin models for substance testing. Nowadays, human skin models are manually manufactured in cell culture inserts by producing, in a first step, the dermal layer, where fibroblasts are embedded in a collagen I hydrogel. Afterwards, keratinocytes are placed on top of the collagen-embedded fibroblasts to differentiate into the different epidermal layers after an air-lift. These models are rather simple and not reflecting the complexity of native skin (Figure 1). Furthermore, quality control is only possible at the end of the production process, whereas it would be desirable to control the entire process in situ to select for properly built skin models at any time point thereby reducing costs.
BibTeX:
@poster{Bleisch2012,
  author = {Bleisch, Matthias and Kuster, Michael and Thurner, Marc and Meier, Christoph and Bossen, Anke and Graf-Hausner, Ursula},
  title = {Organomimetic skin model production based on a novel bioprinting technology},
  year = {2012},
  url = {https://pd.zhaw.ch/publikation/upload/201956.pdf}
}
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