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AuthorTitleYearJournal/ProceedingsReftypeDOI/URL
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}
}
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}
}
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} }
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
de Ruijter, M., Ribeiro, A., Dokter, I., Castilho, M. and Malda, J. 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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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.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}
}
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}
}
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}
}
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}
}
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/}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
Ng, W.L., Wang, S., Yeong, W.Y. and Naing, M.W. Skin Bioprinting: Impending Reality or Fantasy? 2016 Trends in Biotechnology
Vol. 34(9), pp. 689-699 
article DOI  
Abstract: Bioprinting provides a fully automated and advanced platform that facilitates the simultaneous and highly specific deposition of multiple types of skin cells and biomaterials, a process that is lacking in conventional skin tissue-engineering approaches. Here, we provide a realistic, current overview of skin bioprinting, distinguishing facts from myths. We present an in-depth analysis of both current skin bioprinting works and the cellular and matrix components of native human skin. We also highlight current limitations and achievements, followed by design considerations and a future outlook for skin bioprinting. The potential of bioprinting with converging opportunities in biology, material, and computational design will eventually facilitate the fabrication of improved tissue-engineered (TE) skin constructs, making bioprinting skin an impending reality.
Bioprinting provides a fully automated and advanced platform that facilitates the simultaneous and highly specific deposition of multiple types of skin cells and biomaterials, a process that is lacking in conventional skin tissue-engineering approaches. Here, we provide a realistic, current overview of skin bioprinting, distinguishing facts from myths. We present an in-depth analysis of both current skin bioprinting works and the cellular and matrix components of native human skin. We also highlight current limitations and achievements, followed by design considerations and a future outlook for skin bioprinting. The potential of bioprinting with converging opportunities in biology, material, and computational design will eventually facilitate the fabrication of improved tissue-engineered (TE) skin constructs, making bioprinting skin an impending reality.
BibTeX:
@article{Ng2016,
  author = {Ng, Wei Long and Wang, Shuai and Yeong, Wai Yee and Naing, May Win},
  title = {Skin Bioprinting: Impending Reality or Fantasy?},
  journal = {Trends in Biotechnology},
  publisher = {Elsevier},
  year = {2016},
  volume = {34},
  number = {9},
  pages = {689--699},
  doi = {https://doi.org/10.1016/j.tibtech.2016.04.006}
}
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}
}
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}
}
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., 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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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 URL 
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{Visscher,
  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},
  url = {http://dx.doi.org/10.1016/j.tibtech.2016.04.001},
  doi = {https://doi.org/10.1016/j.tibtech.2016.04.001}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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