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AUTHOR Kleger, Nicole and Cihova, Martina and Masania, Kunal and Studart, André R. and Löffler, Jörg F.
Title 3d printing of salt as a template for magnesium with structured porosity [Abstract]
Year 2019
Journal/Proceedings advanced materials
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Abstract Porosity is an essential feature in a wide range of applications that combine light weight with high surface area and tunable density. Porous materials can be easily prepared with a vast variety of chemistries using the salt-leaching technique. However, this templating approach has so far been limited to the fabrication of structures with random porosity and relatively simple macroscopic shapes. Here, a technique is reported that combines the ease of salt leaching with the complex shaping possibilities given by additive manufacturing (AM). By tuning the composition of surfactant and solvent, the salt-based paste is rheologically engineered and printed via direct ink writing into grid-like structures displaying structured pores that span from the sub-millimeter to the macroscopic scale. As a proof of concept, dried and sintered NaCl templates are infiltrated with magnesium (Mg), which is typically highly challenging to process by conventional AM techniques due to its highly oxidative nature and high vapor pressure. Mg scaffolds with well-controlled, ordered porosity are obtained after salt removal. The tunable mechanical properties and the potential to be predictably bioresorbed by the human body make these Mg scaffolds attractive for biomedical implants and demonstrate the great potential of this additive technique.
AUTHOR Zhang, Danwei and Jonhson, Win and Herng, Tun Seng and Ang, Yong Quan and Yang, Lin and Tan, Swee Ching and Peng, Erwin and He, Hui and Ding, Jun
Title A 3D-printing method of fabrication for metals{,} ceramics{,} and multi-materials using a universal self-curable technique for robocasting [Abstract]
Year 2019
Journal/Proceedings Materials Horizons
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Ceramics and metals are important materials that modern technologies are constructed from. The capability to produce such materials in a complex geometry with good mechanical properties can revolutionize the way we engineer our devices. Current curing techniques pose challenges such as high energy requirements{,} limitations of materials with high refractive index{,} tedious post-processing heat treatment processes{,} uneven drying shrinkages{,} and brittleness of green bodies. In this paper{,} a novel modified self-curable epoxide–amine 3D printing system is proposed to print a wide range of ceramics (metal oxides{,} nitrides{,} and carbides) and metals without the need for an external curing source. Through this technique{,} complex multi-material structures (with metal–ceramic and ceramic–ceramic combinations) can also be realized. Tailoring and matching the sintering temperatures of different materials through sintering additives and dopants{,} combined with a structural design providing maximum adhesion between interfaces{,} allow us to successfully obtain superior quality sintered multi-material structures. High-quality ceramic and metallic materials have been achieved (e.g.{,} zirconia with >98% theoretical density). Also{,} highly conductive metals and magnetic ceramics were printed and shaped uniquely without the need for a sacrificial support. With the addition of low molecular weight plasticizers and a multi-stage heat treatment process{,} crack-free and dense high-quality integrated multi-material structures fabricated by 3D printing can thus be a reality in the near future.
AUTHOR Kessel, Benjamin and Lee, Mihyun and Bonato, Angela and Tinguely, Yann and Tosoratti, Enrico and Zenobi-Wong, Marcy
Title 3D Bioprinting of Macroporous Materials Based on Entangled Hydrogel Microstrands [Abstract]
Year 2020
Journal/Proceedings Advanced Science
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Abstract Hydrogels are excellent mimetics of mammalian extracellular matrices and have found widespread use in tissue engineering. Nanoporosity of monolithic bulk hydrogels, however, limits mass transport of key biomolecules. Microgels used in 3D bioprinting achieve both custom shape and vastly improved permissivity to an array of cell functions, however spherical-microbead-based bioinks are challenging to upscale, are inherently isotropic, and require secondary crosslinking. Here, bioinks based on high-aspect-ratio hydrogel microstrands are introduced to overcome these limitations. Pre-crosslinked, bulk hydrogels are deconstructed into microstrands by sizing through a grid with apertures of 40–100 µm. The microstrands are moldable and form a porous, entangled structure, stable in aqueous medium without further crosslinking. Entangled microstrands have rheological properties characteristic of excellent bioinks for extrusion bioprinting. Furthermore, individual microstrands align during extrusion and facilitate the alignment of myotubes. Cells can be placed either inside or outside the hydrogel phase with >90% viability. Chondrocytes co-printed with the microstrands deposit abundant extracellular matrix, resulting in a modulus increase from 2.7 to 780.2 kPa after 6 weeks of culture. This powerful approach to deconstruct bulk hydrogels into advanced bioinks is both scalable and versatile, representing an important toolbox for 3D bioprinting of architected hydrogels.
AUTHOR Zhang, Danwei and Peng, Erwin and Borayek, Ramadan and Ding, Jun
Title Controllable Ceramic Green-Body Configuration for Complex Ceramic Architectures with Fine Features [Abstract]
Year 2019
Journal/Proceedings Advanced Functional Materials
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Abstract Fabrication of dense ceramic articles with intricate fine features and geometrically complex morphology by using a relatively simple and the cost-effective process still remains a challenge. Ceramics, either in its green- or sintered-form, are known for being hard yet brittle which limits further shape reconfiguration. In this work, a combinatorial process of ceramic robocasting and photopolymerization is demonstrated to produce either flexible and/or stretchable ceramic green-body (Flex-Body or Stretch-Body) that can undergo a postprinting reconfiguration process. Secondary shaping may proceed through: i) self-assembly-assisted shaping and ii) mold-assisted shaping process, which allows a well-controlled ceramic structure morphology. With a proposed well-controlled thermal heating process, the ceramic Sintered-Body can achieve >99.0% theoretical density with good mechanical rigidity. Complex and dense ceramic articles with fine features down to 65 μm can be fabricated. When combined with a multi-nozzle deposition process, i) self-shaping ceramic structures can be realized through anisotropic shrinkage induced by suspensions' composition variation and ii) technical and functional multiceramic structures can be fabricated. The simplicity of the proposed technique and its inexpensive processing cost make it an attractive approach for fabricating geometrically complex ceramic articles with unique macrostructures, which complements the existing state of-the-art ceramic additive manufacturing techniques.
AUTHOR Kokkinis, Dimitri and Bouville, Florian and Studart, André R.
Title 3D Printing of Materials with Tunable Failure via Bioinspired Mechanical Gradients [Abstract]
Year 2018
Journal/Proceedings Advanced Materials
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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.
AUTHOR Schaffner, Manuel and R{"u}hs, Patrick A. and Coulter, Fergal and Kilcher, Samuel and Studart, Andr{'e} R.
Title 3D printing of bacteria into functional complex materials [Abstract]
Year 2017
Journal/Proceedings Science Advances
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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 {textquotedblleft}living materials{textquotedblright} 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.
AUTHOR Govindharaj, Mano and Al Hashemi, Noura Sayed and Soman, Soja Saghar and Vijayavenkataraman, Sanjairaj
Title Bioprinting of bioactive tissue scaffolds from ecologically-destructive fouling tunicates [Abstract]
Year 2022
Journal/Proceedings Journal of Cleaner Production
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Urochordates are the closest invertebrate relative to humans and commonly referred to as tunicates, a name ascribed to their leathery outer “tunic”. The tunic is the outer covering of the organism which functions as the exoskeleton and is rich in carbohydrates and proteins. Invasive or fouling tunicates pose a great threat to the indigenous marine ecosystem and governments spend several hundred thousand dollars for tunicate management, considering the huge adverse economic impact it has on the shipping and fishing industries. In this work, the environmentally destructive colonizing tunicate species of Polyclinum constellatum was successfully identified in the coast of Abu Dhabi and methods of sustainably using it as wound-dressing materials, decellularized extra-cellular matrix (dECM) scaffolds for tissue engineering applications and bioinks for bioprinting of tissue constructs for regenerative medicine are proposed. The intricate three-dimensional nanofibrous cellulosic networks in the tunic remain intact even after the multi-step process of decellularization and lyophilization. The lyophilized dECM tunics possess excellent biocompatibility and remarkable tensile modulus of 3.85 ± 0.93 MPa compared to ∼0.1–1 MPa of other hydrogel systems. This work demonstrates the use of lyophilized tunics as wound-dressing materials, having outperformed the commercial dressing materials with a capacity of absorbing 20 times its weight in the dry state. This work also demonstrates the biocompatibility of dECM scaffold and dECM-derived bioink (3D bioprinting with Mouse Embryonic Fibroblasts (MEFs)). Both dECM scaffolds and bioprinted dECM-based tissue constructs show enhanced metabolic activity and cell proliferation over time. Sustainable utilization of dECM-based biomaterials from ecologically-destructive fouling tunicates proposed in this work helps preserve the marine ecosystem, shipping and fishing industries worldwide, and mitigate the huge cost spent for tunicate management.
AUTHOR Yan Li and Lijing Huang and Guangpin Tai and Feifei Yan and Lin Cai and Chenxing Xin and Shamoon {Al Islam}
Title Graphene Oxide-loaded magnetic nanoparticles within 3D hydrogel form High-performance scaffolds for bone regeneration and tumour treatment [Abstract]
Year 2022
Journal/Proceedings Composites Part A: Applied Science and Manufacturing
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The treatment of tumour-related bone defects should ideally combine bone regeneration with tumour treatment. Additive manufacturing (AM) could feasibly place functional bone-repair materials within composite materials with functional-grade structures, giving them bone repair and anti-tumour effects. Magnetothermal therapy is a promising non-invasive method of tumour treatment that has attracted increasing attention. In this study, we prepared novel hydrogel composite scaffolds of polyvinyl alcohol/sodium alginate/hydroxyapatite (PVA/SA/HA) at low temperature via AM. The scaffolds were loaded with various concentrations of magnetic graphene oxide (MGO) @Fe3O4 nanoparticles. The scaffolds were characterised by fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and thermal gravimetric analysis (TGA), which showed that the scaffolds have good moulding qualities and strong hydrogen bonding between the MGO/PVA/SA/HA components. TGA analysis demonstrated the expected thermal stability of the MGO and scaffolds. Thermal effects can be adjusted by varying the contents of MGO and the strength of an external alternating magnetic field. The prepared MGO hydrogel composite scaffolds enhance biological functions and support bone mesenchymal stem cell differentiation in vitro. The scaffolds also show favourable anti-tumour characteristics with effective magnetothermal conversion in vivo.
AUTHOR Cernencu, Alexandra I. and Lungu, Adriana and Dragusin, Diana M. and Stancu, Izabela C. and Dinescu, Sorina and Balahura, Liliana R. and Mereuta, Paul and Costache, Marieta and Iovu, Horia
Title 3D Bioprinting of Biosynthetic Nanocellulose-Filled GelMA Inks Highly Reliable for Soft Tissue-Oriented Constructs [Abstract]
Year 2021
Journal/Proceedings Materials
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Bioink-formulations based on gelatin methacrylate combined with oxidized cellulose nanofibrils are employed in the present study. The parallel investigation of the printing performance, morphological, swelling, and biological properties of the newly developed hydrogels was performed, with inks prepared using methacrylamide-modified gelatins of fish or bovine origin. Scaffolds with versatile and well-defined internal structure and high shape fidelity were successfully printed due to the high viscosity and shear-thinning behavior of formulated inks and then photo-crosslinked. The biocompatibility of 3D-scaffolds was surveyed using human adipose stem cells (hASCs) and high viability and proliferation rates were obtained when in contact with the biomaterial. Furthermore, bioprinting tests were performed with hASCs embedded in the developed formulations. The results demonstrated that the designed inks are a versatile toolkit for 3D bioprinting and further show the benefits of using fish-derived gelatin for biofabrication.
AUTHOR Rößler, Sina and Brückner, Andreas and Kruppke, Iris and Wiesmann, Hans-Peter and Hanke, Thomas and Kruppke, Benjamin
Title 3D Plotting of Silica/Collagen Xerogel Granules in an Alginate Matrix for Tissue-Engineered Bone Implants [Abstract]
Year 2021
Journal/Proceedings Materials
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Today, materials designed for bone regeneration are requested to be degradable and resorbable, bioactive, porous, and osteoconductive, as well as to be an active player in the bone-remodeling process. Multiphasic silica/collagen Xerogels were shown, earlier, to meet these requirements. The aim of the present study was to use these excellent material properties of silica/collagen Xerogels and to process them by additive manufacturing, in this case 3D plotting, to generate implants matching patient specific shapes of fractures or lesions. The concept is to have Xerogel granules as active major components embedded, to a large proportion, in a matrix that binds the granules in the scaffold. By using viscoelastic alginate as matrix, pastes of Xerogel granules were processed via 3D plotting. Moreover, alginate concentration was shown to be the key to a high content of irregularly shaped Xerogel granules embedded in a minimum of matrix phase. Both the alginate matrix and Xerogel granules were also shown to influence viscoelastic behavior of the paste, as well as the dimensionally stability of the scaffolds. In conclusion, 3D plotting of Xerogel granules was successfully established by using viscoelastic properties of alginate as matrix phase.
AUTHOR Leu Alexa, Rebeca and Ianchis, Raluca and Savu, Diana and Temelie, Mihaela and Trica, Bogdan and Serafim, Andrada and Vlasceanu, George Mihail and Alexandrescu, Elvira and Preda, Silviu and Iovu, Horia
Title 3D Printing of Alginate-Natural Clay Hydrogel-Based Nanocomposites [Abstract]
Year 2021
Journal/Proceedings Gels
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Biocompatibility, biodegradability, shear tinning behavior, quick gelation and an easy crosslinking process makes alginate one of the most studied polysaccharides in the field of regenerative medicine. The main purpose of this study was to obtain tissue-like materials suitable for use in bone regeneration. In this respect, alginate and several types of clay were investigated as components of 3D-printing, nanocomposite inks. Using the extrusion-based nozzle, the nanocomposites inks were printed to obtain 3D multilayered scaffolds. To observe the behavior induced by each type of clay on alginate-based inks, rheology studies were performed on composite inks. The structure of the nanocomposites samples was examined using Fourier Transform Infrared Spectrometry and X-ray Diffraction (XRD), while the morphology of the 3D-printed scaffolds was evaluated using Electron Microscopy (SEM, TEM) and Micro-Computed Tomography (Micro-CT). The swelling and dissolvability of each composite scaffold in phosfate buffer solution were followed as function of time. Biological studies indicated that the cells grew in the presence of the alginate sample containing unmodified clay, and were able to proliferate and generate calcium deposits in MG-63 cells in the absence of specific signaling molecules. This study provides novel information on potential manufacturing methods for obtaining nanocomposite hydrogels suitable for 3D printing processes, as well as valuable information on the clay type selection for enabling accurate 3D-printed constructs. Moreover, this study constitutes the first comprehensive report related to the screening of several natural clays for the additive manufacturing of 3D constructs designed for bone reconstruction therapy.
AUTHOR Leu Alexa, Rebeca and Iovu, Horia and Ghitman, Jana and Serafim, Andrada and Stavarache, Cristina and Marin, Maria-Minodora and Ianchis, Raluca
Title 3D-Printed Gelatin Methacryloyl-Based Scaffolds with Potential Application in Tissue Engineering [Abstract]
Year 2021
Journal/Proceedings Polymers
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The development of materials for 3D printing adapted for tissue engineering represents one of the main concerns nowadays. Our aim was to obtain suitable 3D-printed scaffolds based on methacrylated gelatin (GelMA). In this respect, three degrees of GelMA methacrylation, three different concentrations of GelMA (10%, 20%, and 30%), and also two concentrations of photoinitiator (I-2959) (0.5% and 1%) were explored to develop proper GelMA hydrogel ink formulations to be used in the 3D printing process. Afterward, all these GelMA hydrogel-based inks/3D-printed scaffolds were characterized structurally, mechanically, and morphologically. The presence of methacryloyl groups bounded to the surface of GelMA was confirmed by FTIR and 1H-NMR analyses. The methacrylation degree influenced the value of the isoelectric point that decreased with the GelMA methacrylation degree. A greater concentration of photoinitiator influenced the hydrophilicity of the polymer as proved using contact angle and swelling studies because of the new bonds resulting after the photocrosslinking stage. According to the mechanical tests, better mechanical properties were obtained in the presence of the 1% initiator. Circular dichroism analyses demonstrated that the secondary structure of gelatin remained unaffected during the methacrylation process, thus being suitable for biological applications.
AUTHOR Jiahui Lai and Xinliang Ye and Jia Liu and Chong Wang and Junzhi Li and Xiang Wang and Mingze Ma and Min Wang
Title 4D printing of highly printable and shape morphing hydrogels composed of alginate and methylcellulose [Abstract]
Year 2021
Journal/Proceedings Materials & Design
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4D printing of swellable/shrinkable hydrogels has been viewed as an appealing approach for fabricating dynamic structures for various biomedical applications. However, 4D printing of precise hydrogel structures is still highly challenging due to the relatively poor printability of hydrogels and high surface roughness of printed patterns, when micro extrusion-based 3D printers are used. In this study, a highly printable and shape morphing hydrogel was investigated for 4D printing by blending alginate (Alg) and methylcellulose (MC). The optimized Alg/MC hydrogel exhibited excellent rheological properties, extrudability and shape fidelity of printed structures. The printable Alg/MC hydrogel was 4D printed into a series of patterned 2D architectures which were encoded with anisotropic stiffness and swelling behaviors by strategically controlling the network density gradients vertical to the orientation of the patterned strips. By controlling the strip interspacing and angle, these 2D architectures could transform into various prescribed simple 3D morphologies (e.g., tube-curling and helix) and complex 3D morphologies (e.g., double helix and flowers) after immersion in a calcium chloride solution. This shape morphing Alg/MC hydrogel with excellent printability has high potential for 4D printing of delicate hydrogel patterns, which are increasingly needed in the tissue engineering, biomedical device and soft robotics fields.
AUTHOR Kwak, Chaesu and Young Ryu, Seoung and Park, Hyunsu and Lim, Sehyeong and Yang, Jeewon and Kim, Jieun and Hyung Kim, Jin and Lee, Joohyung
Title A pickering emulsion stabilized by chlorella microalgae as an eco-friendly extrusion-based 3D printing ink processable under ambient conditions [Abstract]
Year 2021
Journal/Proceedings Journal of Colloid and Interface Science
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Three-dimensional (3D) printing technology is actively utilized in various industrial fields because it facilitates effective and customizable fabrication of complex structures. An important processing route for 3D printing is the extrusion of inks in the form of colloidal suspensions or emulsions, which has recently attracted considerable attention because it allows for selection of a wide range of printing materials and is operable under ambient processing conditions. Herein, we investigate the 3D printability of complex fluids containing chlorella microalgae as an eco-friendly material for 3D printing. Two possible ink types are considered: aqueous chlorella suspensions and emulsions of oil and water mixtures. While the aqueous chlorella suspensions at high particle loading display the 3D-printable rheological properties such as high yield stress and good shape retention, the final structures after extruding and drying the suspensions under ambient conditions show a significant number of macroscopic defects, limiting their practical application. In contrast, the 3D structures produced from the oil-in-water Pickering emulsions stabilized by chlorella microalgae, which are amphiphilic and active at the oil–water interface, show significantly reduced defect formation. Addition of a fast-evaporable oil phase, hexane, is crucial in the mechanisms of enhanced cementation between the individual microalgae via increased inter-particle packing, capillary attraction, and hydrophobic interaction. Furthermore, addition of solid paraffin wax, which is crystalline but well-soluble in the hydrocarbon oil phase under ambient conditions, completely eliminates the undesirable defect formation via enhanced inter-particle binding, while maintaining the overall rheological properties of the emulsion. The optimal formulation of the Pickering emulsion is finally employed to produce a 3D scaffold of satisfactory structural integrity, suggesting that the chlorella-based ink, in the form of an emulsion, has potential as an eco-friendly 3D printing ink processable under ambient conditions.
AUTHOR Zuoxin Zhou and Mario Samperi and Lea Santu and Glenieliz Dizon and Shereen Aboarkaba and David Limón and David Limón and Christopher Tuck and Lluïsa Pérez-García and Derek J. Irvine and David B. Amabilino and Ricky Wildman
Title An Imidazolium-Based Supramolecular Gelator Enhancing Interlayer Adhesion in 3D Printed Dual Network Hydrogels [Abstract]
Year 2021
Journal/Proceedings Materials & Design
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The variety of UV-curable monomers for 3D printing is limited by a requirement for rapid curing after each sweep depositing a layer. This study proposes to trigger supramolecular self-assembly during the process by a gemini imidazolium-based low-molecular-weight gelator, allowing printing of certain monomers. The as-printed hydrogel structures were supported by a gelator network immobilising monomer:water solutions. A thixotropic hydrogel was formed with a recovery time of < 50 seconds, storage modulus = 8.1 kPa and yield stress = 18 Pa, processable using material-extrusion 3D printing. Material-extrusion 3D printed objects are usually highly anisotropic, but in this case the gelator network improved the isotropy by subverting the usual layer-by-layer curing strategy. The monomer in all printed layers was cured simultaneously during post-processing to form a continuous polymeric network. The two networks then physically interpenetrate to enhance mechanical performance. The double-network hydrogels fabricated with layers cured simultaneously showed 62-147 % increases in tensile properties compared to layer-by-layer cured hydrogels. The results demonstrated excellent inter- and intra-layered coalescence. Consequently, the tensile properties of 3D printed hydrogels were close to mould cast objects. This study has demonstrated the benefits of using gelators to expand the variety of 3D printable monomers and shown improved isotropy to offer excellent mechanical performances.
AUTHOR Yuanhao Wu and Gabriele Maria Fortunato and Babatunde O Okesola and Francesco Luigi Pellerej di Brocchetti and Ratima Suntornnond and John Connelly and Carmelo De Maria and Jose Carlos Rodriguez-Cabello and Giovanni Vozzi and Wen Wang and Alvaro Mata
Title An interfacial self-assembling bioink for the manufacturing of capillary-like structures with tuneable and anisotropic permeability [Abstract]
Year 2021
Journal/Proceedings Biofabrication
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Self-assembling bioinks offer the possibility to biofabricate with molecular precision, hierarchical control, and biofunctionality. For this to become a reality with widespread impact, it is essential to engineer these ink systems ensuring reproducibility and providing suitable standardization. We have reported a self-assembling bioink based on disorder-to-order transitions of an elastin-like recombinamer (ELR) to co-assemble with graphene oxide (GO). Here, we establish reproducible processes, optimize printing parameters for its use as a bioink, describe new advantages that the self-assembling bioink can provide, and demonstrate how to fabricate novel structures with physiological relevance. We fabricate capillary-like structures with resolutions down to ∼10 µm in diameter and ∼2 µm thick tube walls and use both experimental and finite element analysis to characterize the printing conditions, underlying interfacial diffusion-reaction mechanism of assembly, printing fidelity, and material porosity and permeability. We demonstrate the capacity to modulate the pore size and tune the permeability of the resulting structures with and without human umbilical vascular endothelial cells. Finally, the potential of the ELR-GO bioink to enable supramolecular fabrication of biomimetic structures was demonstrated by printing tubes exhibiting walls with progressively different structure and permeability.
AUTHOR Leu Alexa, Rebeca and Iovu, Horia and Trica, Bogdan and Zaharia, Catalin and Serafim, Andrada and Alexandrescu, Elvira and Radu, Ionut-Cristian and Vlasceanu, George and Preda, Silviu and Ninciuleanu, Claudia Mihaela and Ianchis, Raluca
Title Assessment of Naturally Sourced Mineral Clays for the 3D Printing of Biopolymer-Based Nanocomposite Inks [Abstract]
Year 2021
Journal/Proceedings Nanomaterials
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The present study investigated the possibility of obtaining 3D printed composite constructs using biomaterial-based nanocomposite inks. The biopolymeric matrix consisted of methacrylated gelatin (GelMA). Several types of nanoclay were added as the inorganic component. Our aim was to investigate the influence of clay type on the rheological behavior of ink formulations and to determine the morphological and structural properties of the resulting crosslinked hydrogel-based nanomaterials. Moreover, through the inclusion of nanoclays, our goal was to improve the printability and shape fidelity of nanocomposite scaffolds. The viscosity of all ink formulations was greater in the presence of inorganic nanoparticles as shear thinning occurred with increased shear rate. Hydrogel nanocomposites presented predominantly elastic rather than viscous behavior as the materials were crosslinked which led to improved mechanical properties. The inclusion of nanoclays in the biopolymeric matrix limited hydrogel swelling due the physical barrier effect but also because of the supplementary crosslinks induced by the clay layers. The distribution of inorganic filler within the GelMA-based hydrogels led to higher porosities as a consequence of their interaction with the biopolymeric ink. The present study could be useful for the development of soft nanomaterials foreseen for the additive manufacturing of customized implants for tissue engineering.
AUTHOR Silvestri, Alessandro and Criado, Alejandro and Poletti, Fabrizio and Wang, Faxing and Fanjul-Bolado, Pablo and González-García, María B. and García-Astrain, Clara and Liz-Marzán, Luis M. and Feng, Xinliang and Zanardi, Chiara and Prato, Maurizio
Title Bioresponsive, Electroactive, and Inkjet-Printable Graphene-Based Inks [Abstract]
Year 2021
Journal/Proceedings Advanced Functional Materials
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Abstract With the advent of flexible electronics, the old fashioned and conventional solid-state technology will be replaced by conductive inks combined with low-cost printing techniques. Graphene is an ideal candidate to produce conductive inks, due to its excellent conductivity and zero bandgap. The possibility to chemically modify graphene with active molecules opens up the field of responsive conductive inks. Herein, a bioresponsive, electroactive, and inkjet-printable graphene ink is presented. The ink is based on graphene chemically modified with selected enzymes and an electrochemical mediator, to transduce the products of the enzymatic reaction into an electron flow, proportional to the analyte concentration. A water-based formulation is engineered to be respectful with the enzymatic activity while matching the stringent requirements of inkjet printing. The efficient electrochemical performance of the ink, as well as a proof-of-concept application in biosensing, is demonstrated. The versatility of the system is demonstrated by modifying graphene with various oxidoreductases, obtaining inks with selectivity toward glucose, lactate, methanol, and ethanol.
AUTHOR Kamdem Tamo, Arnaud and Doench, Ingo and Walter, Lukas and Montembault, Alexandra and Sudre, Guillaume and David, Laurent and Morales-Helguera, Aliuska and Selig, Mischa and Rolauffs, Bernd and Bernstein, Anke and Hoenders, Daniel and Walther, Andreas and Osorio-Madrazo, Anayancy
Title Development of Bioinspired Functional Chitosan/Cellulose Nanofiber 3D Hydrogel Constructs by 3D Printing for Application in the Engineering of Mechanically Demanding Tissues [Abstract]
Year 2021
Journal/Proceedings Polymers
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Soft tissues are commonly fiber-reinforced hydrogel composite structures, distinguishable from hard tissues by their low mineral and high water content. In this work, we proposed the development of 3D printed hydrogel constructs of the biopolymers chitosan (CHI) and cellulose nanofibers (CNFs), both without any chemical modification, which processing did not incorporate any chemical crosslinking. The unique mechanical properties of native cellulose nanofibers offer new strategies for the design of environmentally friendly high mechanical performance composites. In the here proposed 3D printed bioinspired CNF-filled CHI hydrogel biomaterials, the chitosan serves as a biocompatible matrix promoting cell growth with balanced hydrophilic properties, while the CNFs provide mechanical reinforcement to the CHI-based hydrogel. By means of extrusion-based printing (EBB), the design and development of 3D functional hydrogel scaffolds was achieved by using low concentrations of chitosan (2.0–3.0% (w/v)) and cellulose nanofibers (0.2–0.4% (w/v)). CHI/CNF printed hydrogels with good mechanical performance (Young’s modulus 3.0 MPa, stress at break 1.5 MPa, and strain at break 75%), anisotropic microstructure and suitable biological response, were achieved. The CHI/CNF composition and processing parameters were optimized in terms of 3D printability, resolution, and quality of the constructs (microstructure and mechanical properties), resulting in good cell viability. This work allows expanding the library of the so far used biopolymer compositions for 3D printing of mechanically performant hydrogel constructs, purely based in the natural polymers chitosan and cellulose, offering new perspectives in the engineering of mechanically demanding hydrogel tissues like intervertebral disc (IVD), cartilage, meniscus, among others.
AUTHOR Curti, Filis and Drăgușin, Diana-Maria and Serafim, Andrada and Iovu, Horia and Stancu, Izabela-Cristina
Title Development of thick paste-like inks based on superconcentrated gelatin/alginate for 3D printing of scaffolds with shape fidelity and stability [Abstract]
Year 2021
Journal/Proceedings Materials Science and Engineering: C
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Shape fidelity and integrity are serious challenges in the 3D printing of hydrogel precursors, as they can influence the overall performance of 3D scaffolds. This work reports the development of superconcentrated inks based on sodium alginate and fish gelatin as an appealing strategy to satisfy such challenges and dictate the quality of the printed scaffolds, without using crosslinking strategies during 3D printing. SEM micrographs and micro-CT images indicate the homogeneous distribution of the polysaccharide in the gelatin-based matrix, suggesting its potential to act as a reinforcing additive. The high concentration of gelatin aqueous solution (50 wt%) and substantial incorporation of alginate have facilitated the highly accurate printability and influence the in vitro stability and mechanical properties of the printed scaffolds. An improvement of the stiffness is dictated by the increase of alginate concentration from 20 wt% to 25 wt%, and an increase of Young modulus with about 46% is reached, confirming the reinforcing effect of polysaccharide. This study highlights the potential of paste-type inks to provide high resolution 3D printed structures with appealing structural and dimensional stability, in vitro degradability and mechanical properties for biomedical applications.
AUTHOR Shiwarski,Daniel J. and Hudson,Andrew R. and Tashman,Joshua W. and Feinberg,Adam W.
Title Emergence of FRESH 3D printing as a platform for advanced tissue biofabrication
Year 2021
Journal/Proceedings APL Bioengineering
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AUTHOR Chen, Shengyang and Shi, Qian and Jang, Taesik and Ibrahim, Mohammed Shahrudin Bin and Deng, Jingyu and Ferracci, Gaia and Tan, Wen See and Cho, Nam-Joon and Song, Juha
Title Engineering Natural Pollen Grains as Multifunctional 3D Printing Materials [Abstract]
Year 2021
Journal/Proceedings Advanced Functional Materials
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Abstract The development of multifunctional 3D printing materials from sustainable natural resources is a high priority in additive manufacturing. Using an eco-friendly method to transform hard pollen grains into stimulus-responsive microgel particles, we engineered a pollen-derived microgel suspension that can serve as a functional reinforcement for composite hydrogel inks and as a supporting matrix for versatile freeform 3D printing systems. The pollen microgel particles enabled the printing of composite inks and improved the mechanical and physiological stabilities of alginate and hyaluronic acid hydrogel scaffolds for 3D cell culture applications. Moreover, the particles endowed the inks with stimulus-responsive controlled release properties. The suitability of the pollen microgel suspension as a supporting matrix for freeform 3D printing of alginate and silicone rubber inks was demonstrated and optimized by tuning the rheological properties of the microgel. Compared with other classes of natural materials, pollen grains have several compelling features, including natural abundance, renewability, affordability, processing ease, monodispersity, and tunable rheological features, which make them attractive candidates to engineer advanced materials for 3D printing applications.
AUTHOR Götz, Lisa-Marie and Holeczek, Katharina and Groll, Jürgen and Jüngst, Tomasz and Gbureck, Uwe
Title Extrusion-Based 3D Printing of Calcium Magnesium Phosphate Cement Pastes for Degradable Bone Implants [Abstract]
Year 2021
Journal/Proceedings Materials
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Abstract
This study aimed to develop printable calcium magnesium phosphate pastes that harden by immersion in ammonium phosphate solution post-printing. Besides the main mineral compound, biocompatible ceramic, magnesium oxide and hydroxypropylmethylcellulose (HPMC) were the crucial components. Two pastes with different powder to liquid ratios of 1.35 g/mL and 1.93 g/mL were characterized regarding their rheological properties. Here, ageing over the course of 24 h showed an increase in viscosity and extrusion force, which was attributed to structural changes in HPMC as well as the formation of magnesium hydroxide by hydration of MgO. The pastes enabled printing of porous scaffolds with good dimensional stability and enabled a setting reaction to struvite when immersed in ammonium phosphate solution. Mechanical performance under compression was approx. 8–20 MPa as a monolithic structure and 1.6–3.0 MPa for printed macroporous scaffolds, depending on parameters such as powder to liquid ratio, ageing time, strand thickness and distance.
AUTHOR Wibowo, Arie and Tajalla, Gusti U. N. and Marsudi, Maradhana A. and Cooper, Glen and Asri, Lia A.T.W. and Liu, Fengyuan and Ardy, Husaini and Bartolo, Paulo J.D.S.
Title Green Synthesis of Silver Nanoparticles Using Extract of Cilembu Sweet Potatoes (Ipomoea batatas L var. Rancing) as Potential Filler for 3D Printed Electroactive and Anti-Infection Scaffolds [Abstract]
Year 2021
Journal/Proceedings Molecules
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Electroactive biomaterials are fascinating for tissue engineering applications because of their ability to deliver electrical stimulation directly to cells, tissue, and organs. One particularly attractive conductive filler for electroactive biomaterials is silver nanoparticles (AgNPs) because of their high conductivity, antibacterial activity, and ability to promote bone healing. However, production of AgNPs involves a toxic reducing agent which would inhibit biological scaffold performance. This work explores facile and green synthesis of AgNPs using extract of Cilembu sweet potato and studies the effect of baking and precursor concentrations (1, 10 and 100 mM) on AgNPs’ properties. Transmission electron microscope (TEM) results revealed that the smallest particle size of AgNPs (9.95 ± 3.69 nm) with nodular morphology was obtained by utilization of baked extract and ten mM AgNO3. Polycaprolactone (PCL)/AgNPs scaffolds exhibited several enhancements compared to PCL scaffolds. Compressive strength was six times greater (3.88 ± 0.42 MPa), more hydrophilic (contact angle of 76.8 ± 1.7°), conductive (2.3 ± 0.5 × 10−3 S/cm) and exhibited anti-bacterial properties against Staphylococcus aureus ATCC3658 (99.5% reduction of surviving bacteria). Despite the promising results, further investigation on biological assessment is required to obtain comprehensive study of this scaffold. This green synthesis approach together with the use of 3D printing opens a new route to manufacture AgNPs-based electroactive with improved anti-bacterial properties without utilization of any toxic organic solvents.
AUTHOR Tan, Edgar Y. S. and Suntornnond, Ratima and Yeong, Wai Yee
Title High-Resolution Novel Indirect Bioprinting of Low-Viscosity Cell-Laden Hydrogels via Model-Support Bioink Interaction [Abstract]
Year 2021
Journal/Proceedings 3D Printing and Additive Manufacturing
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Abstract Bioprinting of unmodified soft extracellular matrix into complex 3D structures has remained challenging to fabricate. Herein, we established a novel process for the printing of low-viscosity hydrogel by using a unique support technique to retain the structural integrity of the support structure. We demonstrated that this process of printing could be used for different types of hydrogel, ranging from fast crosslinking gelatin methacrylate to slow crosslinking collagen type I. In addition, we evaluated the biocompatibility of the process by observing the effects of the cytotoxicity of L929 and the functionality of the human umbilical vein endothelium primary cells after printing. The results show that the bioprinted construct provided excellent biocompatibility as well as supported cell growth and differentiation. Thus, this is a novel technique that can be potentially used to enhance the resolution of the extrusion-based bioprinter.
AUTHOR Lechner, Annika and Trossmann, Vanessa T. and Scheibel, Thomas
Title Impact of Cell Loading of Recombinant Spider Silk Based Bioinks on Gelation and Printability [Abstract]
Year 2021
Journal/Proceedings Macromolecular Bioscience
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Abstract Printability of bioinks encompasses considerations concerning rheology and extrudability, characterization of filament formation, shape fidelity, cell viability and post-printing cellular development. Recombinant spider silk based hydrogels might be a suitable material to be used in bioinks, i.e. a formulation of cells and materials to be used for bioprinting. Here, the high shape fidelity of spider silk ink is shown by bioprinting the shape and size of a human aortic valve. Further the influence of the encapsulation of cells has been evaluated on spider silk hydrogel formation, hydrogel mechanics, and shape fidelity upon extrusion based bioprinting. It is shown that the presence of cells impacts gelation of spider silk proteins differently depending on the used silk variant. RGD-modified spider silk hydrogels are physically crosslinked by the cells, while there is no active interaction between cells and un-tagged spider silk proteins. Strikingly, even at cell densities up to ten million cells/ml, cell viability is high after extrusion based printing which is a significant prerequisite for future applications. Shape fidelity of the printed constructs is demonstrated using a filament collapse test in absence and presence of human cells. This article is protected by copyright. All rights reserved
AUTHOR Trucco, Diego and Sharma, Aarushi and Manferdini, Cristina and Gabusi, Elena and Petretta, Mauro and Desando, Giovanna and Ricotti, Leonardo and Chakraborty, Juhi and Ghosh, Sourabh and Lisignoli, Gina
Title Modeling and Fabrication of Silk Fibroin-Gelatin-Based Constructs Using Extrusion-Based Three-Dimensional Bioprinting [Abstract]
Year 2021
Journal/Proceedings ACS Biomater. Sci. Eng.
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Robotic dispensing-based 3D bioprinting represents one of the most powerful technologies to develop hydrogel-based 3D constructs with enormous potential in the field of regenerative medicine. The optimization of hydrogel printing parameters, proper geometry and internal architecture of the constructs, and good cell viability during the bioprinting process are the essential requirements. In this paper, an analytical model based on the hydrogel rheological properties was developed to predict the extruded filament width in order to maximize the printed structure’s fidelity to the design. Viscosity data of two natural hydrogels were imputed to a power-law model to extrapolate the filament width. Further, the model data were validated by monitoring the obtained filament width as the output. Shear stress values occurring during the bioprinting process were also estimated. Human mesenchymal stromal cells (hMSCs) were encapsulated in the silk fibroin-gelatin (G)-based hydrogel, and a 3D bioprinting process was performed to produce cell-laden constructs. Live and dead assay allowed estimating the impact of needle shear stress on cell viability after the bioprinting process. Finally, we tested the potential of hMSCs to undergo chondrogenic differentiation by evaluating the cartilaginous extracellular matrix production through immunohistochemical analyses. Overall, the use of the proposed analytical model enables defining the optimal printing parameters to maximize the fabricated constructs’ fidelity to design parameters before the process execution, enabling to achieve more controlled and standardized products than classical trial-and-error approaches in the biofabrication of engineered constructs. Employing modeling systems exploiting the rheological properties of the hydrogels might be a valid tool in the future for guaranteeing high cell viability and for optimizing tissue engineering approaches in regenerative medicine applications. Robotic dispensing-based 3D bioprinting represents one of the most powerful technologies to develop hydrogel-based 3D constructs with enormous potential in the field of regenerative medicine. The optimization of hydrogel printing parameters, proper geometry and internal architecture of the constructs, and good cell viability during the bioprinting process are the essential requirements. In this paper, an analytical model based on the hydrogel rheological properties was developed to predict the extruded filament width in order to maximize the printed structure’s fidelity to the design. Viscosity data of two natural hydrogels were imputed to a power-law model to extrapolate the filament width. Further, the model data were validated by monitoring the obtained filament width as the output. Shear stress values occurring during the bioprinting process were also estimated. Human mesenchymal stromal cells (hMSCs) were encapsulated in the silk fibroin-gelatin (G)-based hydrogel, and a 3D bioprinting process was performed to produce cell-laden constructs. Live and dead assay allowed estimating the impact of needle shear stress on cell viability after the bioprinting process. Finally, we tested the potential of hMSCs to undergo chondrogenic differentiation by evaluating the cartilaginous extracellular matrix production through immunohistochemical analyses. Overall, the use of the proposed analytical model enables defining the optimal printing parameters to maximize the fabricated constructs’ fidelity to design parameters before the process execution, enabling to achieve more controlled and standardized products than classical trial-and-error approaches in the biofabrication of engineered constructs. Employing modeling systems exploiting the rheological properties of the hydrogels might be a valid tool in the future for guaranteeing high cell viability and for optimizing tissue engineering approaches in regenerative medicine applications.
AUTHOR Iria Seoane-Viaño and Patricija Januskaite and Carmen Alvarez-Lorenzo and Abdul W. Basit and Alvaro Goyanes
Title Semi-solid extrusion 3D printing in drug delivery and biomedicine: Personalised solutions for healthcare challenges [Abstract]
Year 2021
Journal/Proceedings Journal of Controlled Release
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Three-dimensional (3D) printing is an innovative additive manufacturing technology, capable of fabricating unique structures in a layer-by-layer manner. Semi-solid extrusion (SSE) is a subset of material extrusion 3D printing, and through the sequential deposition of layers of gel or paste creates objects of any desired size and shape. In comparison to other extrusion-based technologies, SSE 3D printing employs low printing temperatures which makes it suitable for drug delivery and biomedical applications, and the use of disposable syringes provides benefits in meeting critical quality requirements for pharmaceutical use. Besides pharmaceutical manufacturing, SSE 3D printing has attracted increasing attention in the field of bioelectronics, particularly in the manufacture of biosensors capable of measuring physiological parameters or as a means to trigger drug release from medical devices. This review begins by highlighting the major printing process parameters and material properties that influence the feasibility of transforming a 3D design into a 3D object, and follows with a discussion on the current SSE 3D printing developments and their applications in the fields of pharmaceutics, bioprinting and bioelectronics. Finally, the advantages and limitations of this technology are explored, before focusing on its potential clinical applications and suitability for preparing personalised medicines.
AUTHOR Göckler, Tobias and Haase, Sonja and Kempter, Xenia and Pfister, Rebecca and Maciel, Bruna R. and Grimm, Alisa and Molitor, Tamara and Willenbacher, Norbert and Schepers, Ute
Title Tuning Superfast Curing Thiol-Norbornene-Functionalized Gelatin Hydrogels for 3D Bioprinting [Abstract]
Year 2021
Journal/Proceedings Advanced Healthcare Materials
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Abstract Photocurable gelatin-based hydrogels have established themselves as powerful bioinks in tissue engineering due to their excellent biocompatibility, biodegradability, light responsiveness, thermosensitivity and bioprinting properties. While gelatin methacryloyl (GelMA) has been the gold standard for many years, thiol-ene hydrogel systems based on norbornene-functionalized gelatin (GelNB) and a thiolated crosslinker have recently gained increasing importance. In this paper, a highly reproducible water-based synthesis of GelNB is presented, avoiding the use of dimethyl sulfoxide (DMSO) as organic solvent and covering a broad range of degrees of functionalization (DoF: 20% to 97%). Mixing with thiolated gelatin (GelS) results in the superfast curing photoclick hydrogel GelNB/GelS. Its superior properties over GelMA, such as substantially reduced amounts of photoinitiator (0.03% (w/v)), superfast curing (1–2 s), higher network homogeneity, post-polymerization functionalization ability, minimal cross-reactivity with cellular components, and improved biocompatibility of hydrogel precursors and degradation products lead to increased survival of primary cells in 3D bioprinting. Post-printing viability analysis revealed excellent survival rates of > 84% for GelNB/GelS bioinks of varying crosslinking density, while cell survival for GelMA bioinks is strongly dependent on the DoF. Hence, the semisynthetic and easily accessible GelNB/GelS hydrogel is a highly promising bioink for future medical applications and other light-based biofabrication techniques.
AUTHOR Chen, Shengyang and Jang, Tae-Sik and Pan, Houwen Matthew and Jung, Hyun-Do and Sia, Ming Wei and Xie, Shuying and Hang, Yao and Chong, Seow and Wong, Dongan
Title 3D Freeform Printing of Nanocomposite Hydrogels through in situ Precipitation in Reactive Viscous Fluid
Year 2020
Journal/Proceedings International Journal of Bioprinting
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AUTHOR Rupp, Harald and Binder, Wolfgang H.
Title 3D Printing of Core–Shell Capsule Composites for Post-Reactive and Damage Sensing Applications [Abstract]
Year 2020
Journal/Proceedings Advanced Materials Technologies
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Abstract 3D printing of multicomponent materials as an advantageous method over traditional mold casting methods is demonstrated, developing small core–shell capsule composites fabricated by a two-step 3D printing process. Using a two-print-head system (fused deposition modeling extruder and a liquid inkjet print head), micro-sized capsules are manufactured in sizes ranging from 100 to 800 µm. The thermoplastic polymer poly(ε-caprolactone) (PCL) is chosen as matrix/shell material due to its optimal interaction with the embedded hydrophobic liquids. First, the core–shell capsules are printed with model liquids and pure PCL to optimize the printing parameters and to ensure fully enclosed capsules inside the polymer. As a proof of concept, novel “click” reaction systems, used in self-healing and stress-detection applications, are manufactured in which PCL composites with nano- and micro-fillers are combined with reactive, encapsulated liquids. The so generated 3D printed core–shell capsule composite can be used for post-printing reactions and damage sensing when combined with a fluorogenic dye.
AUTHOR Jung, Harry and Lee, Ji Seung and Lee, Jun Ho and Park, Ki Joon and Lee, Jae Jun and Park, Hae Sang
Title A Feasibility Study for 3D-printed Poly(methyl methacrylate)-resin Tracheostomy Tube Using a Hamster Cheek Pouch Model
Year 2020
Journal/Proceedings In Vivo
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AUTHOR Lee, J. M. and Sing, S. L. and Yeong, W. Y.
Title Bioprinting of Multimaterials with Computer-aided Design/Computer -aided Manufacturing [Abstract]
Year 2020
Journal/Proceedings International Journal of Bioprinting; Vol 6, No 1 (2020)
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Multimaterials deposition, a distinct advantage in bioprinting, overcomes material’s limitation in hydrogel-based bioprinting. Multimaterials are deposited in a build/support configuration to improve the structural integrity of three-dimensional bioprinted construct. A combination of rapid cross-linking hydrogel has been chosen for the build/support setup. The bioprinted construct was further chemically cross-linked to ensure a stable construct after print. This paper also proposes a file segmentation and preparation technique to be used in bioprinting for printing freeform structures.
AUTHOR Müller, Michael and Fisch, Philipp and Molnar, Marc and Eggert, Sebastian and Binelli, Marco and Maniura-Weber, Katharina and Zenobi-Wong, Marcy
Title Development and thorough characterization of the processing steps of an ink for 3D printing for bone tissue engineering [Abstract]
Year 2020
Journal/Proceedings Materials Science and Engineering: C
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Achieving reproducibility in the 3D printing of biomaterials requires a robust polymer synthesis method to reduce batch-to-batch variation as well as methods to assure a thorough characterization throughout the manufacturing process. Particularly biomaterial inks containing large solid fractions such as ceramic particles, often required for bone tissue engineering applications, are prone to inhomogeneity originating from inadequate mixing or particle aggregation which can lead to inconsistent printing results. The production of such an ink for bone tissue engineering consisting of gellan gum methacrylate (GG-MA), hyaluronic acid methacrylate and hydroxyapatite (HAp) particles was therefore optimized in terms of GG-MA synthesis and ink preparation process, and the ink's printability was thoroughly characterized to assure homogeneous and reproducible printing results. A new buffer mediated synthesis method for GG-MA resulted in consistent degrees of substitution which allowed the creation of large 5 g batches. We found that both the new synthesis as well as cryomilling of the polymer components of the ink resulted in a decrease in viscosity from 113 kPa·s to 11.3 kPa·s at a shear rate of 0.1 s−1 but increased ink homogeneity. The ink homogeneity was assessed through thermogravimetric analysis and a newly developed extrusion force measurement setup. The ink displayed strong inter-layer adhesion between two printed ink layers as well as between a layer of ink with and a layer without HAp. The large polymer batch production along with the characterization of the ink during the manufacturing process allows ink production in the gram scale and could be used in applications such as the printing of osteochondral grafts.
AUTHOR Tan, Wen See and Juhari, Muhammad Aidil Bin and Shi, Qian and Chen, Shengyang and Campolo, Domenico and Song, Juha
Title Development of a new additive manufacturing platform for direct freeform 3D printing of intrinsically curved flexible membranes [Abstract]
Year 2020
Journal/Proceedings Additive Manufacturing
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The wearable technology market has been expanding from wearable medical devices for non-invasive continuous monitoring of patient vital signs to wearable devices for tracking fitness activities that any person can access. Regardless of their form or function, desirable characteristics of wearable devices are the ability to be flexible, conformal, and easily attachable to the human body. However, as the human body is intrinsically curved and irregular, flat devices often have poor interfacial adhesion with the human body. This often leads to interfacial delamination and eventual detachment of the device. Therefore, a new additive manufacturing (AM) platform, a direct freeform 3D printing process (DF3DP), is proposed to allow direct construction of intrinsically curved 3D surfaces during the material deposition phase without the need for any pre-shaped supporting molds or templates. This 3D freeform printing process involves a supporting matrix made up of calcium alginate microgels, printing material made from silicone ink, and freeform printing paths derived from customized G-codes that conform exactly to the scanned human surface profile. Curved meshes mimicking the human elbow were used as a demonstration. A static contact stability test showed that the printed 3D silicone mesh was highly conformal to the model elbow surface as compared to a 2D flat mesh. A dynamic contact stability test was also conducted by subjecting both meshes to 100 cycles of mechanical flexion and extension, proving that intrinsically curved surfaces can provide better contact stability for complex human body surfaces undergoing motion than can flat surfaces. These results have proven that intrinsically curved membranes or structures fabricated by DF3DP can reduce the interfacial shear stress and occurrence of cracks and delamination while maintaining structural integrity and stability during use without compromising the comfort of the users. Our approach can resolve interfacial issues in flexible substrates and has great potential for epidermal devices or soft robotics via its long-term sustainable performance.
AUTHOR Zhang, Hua and Cong, Yang and Osi, Amarachi Rosemary and Zhou, Yang and Huang, Fangcheng and Zaccaria, Remo P. and Chen, Jing and Wang, Rong and Fu, Jun
Title Direct 3D Printed Biomimetic Scaffolds Based on Hydrogel Microparticles for Cell Spheroid Growth [Abstract]
Year 2020
Journal/Proceedings Advanced Functional Materials
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Abstract Biocompatible hydrogel inks with shear-thinning, appropriate yield strength, and fast self-healing are desired for 3D bioprinting. However, the lack of ideal 3D bioprinting inks with outstanding printability and high structural fidelity, as well as cell-compatibility, has hindered the progress of extrusion-based 3D bioprinting for tissue engineering. In this study, novel self-healable pre-cross-linked hydrogel microparticles (pcHμPs) of chitosan methacrylate (CHMA) and polyvinyl alcohol (PVA) hybrid hydrogels are developed and used as bioinks for extrusion-based 3D printing of scaffolds with high fidelity and biocompatibility. The pcHμPs display excellent shear thinning when injected through a syringe and subsequently self-heal into gels as shear forces are removed. Numerical simulations indicate that the pcHμPs experience a plug flow in the nozzle with minimal disturbance, which favors a steady and continuous printing. Moreover, the pcHμPs show a self-supportive yield strength (540 Pa), which is critical for the fidelity of printed constructs. A series of biomimetic constructs with very high aspect ratio and delicate fine structures are directly printed by using the pcHμP ink. The 3D printed scaffolds support the growth of bone-marrow-derived mesenchymal stem cells and formation of cell spheroids, which are most important for tissue engineering.
AUTHOR Lee, Jia Min and Yeong, Wai Yee
Title Engineering macroscale cell alignment through coordinated toolpath design using support-assisted 3D bioprinting [Abstract]
Year 2020
Journal/Proceedings Journal of The Royal Society Interface
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Abstract
Aligned cells provide direction-dependent mechanical properties that influence biological and mechanical function in native tissues. Alignment techniques such as casting and uniaxial stretching cannot fully replicate the complex fibre orientation of native tissue such as the heart. In this study, bioprinting is used to direct the orientation of cell alignment. A 0°–90° grid structure was printed to assess the robustness of the support-assisted bioprinting technique. The variation in the angles of the grid pattern is designed to mimic the differences in fibril orientation of native tissues, where angles of cell alignment vary across the different layers. Through bioprinting of a cell–hydrogel mixture, C2C12 cells displayed directed alignment along the longitudinal axis of printed struts. Cell alignment is induced through firstly establishing structurally stable constructs (i.e. distinct 0°–90° structures) and secondly, allowing cells to dynamically remodel the bioprinted construct. Herein reports a method of inducing a macroscale level of controlled cell alignment with angle variation. This was not achievable both in terms of methods (i.e. conventional alignment techniques such as stretching and electrical stimulation) and magnitude (i.e. hydrogel features with less than 100 µm features).
AUTHOR Somasekharan, Lakshmi and Kasoju, Naresh and Raju, Riya and Bhatt, Anugya
Title Formulation and Characterization of Alginate Dialdehyde, Gelatin, and Platelet-Rich Plasma-Based Bioink for Bioprinting Applications [Abstract]
Year 2020
Journal/Proceedings Bioengineering
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Abstract
Layer-by-layer additive manufacturing process has evolved into three-dimensional (3D) “bio-printing” as a means of constructing cell-laden functional tissue equivalents. The process typically involves the mixing of cells of interest with an appropriate hydrogel, termed as “bioink”, followed by printing and tissue maturation. An ideal bioink should have adequate mechanical, rheological, and biological features of the target tissues. However, native extracellular matrix (ECM) is made of an intricate milieu of soluble and non-soluble extracellular factors, and mimicking such a composition is challenging. To this end, here we report the formulation of a multi-component bioink composed of gelatin and alginate -based scaffolding material, as well as a platelet-rich plasma (PRP) suspension, which mimics the insoluble and soluble factors of native ECM respectively. Briefly, sodium alginate was subjected to controlled oxidation to yield alginate dialdehyde (ADA), and was mixed with gelatin and PRP in various volume ratios in the presence of borax. The formulation was systematically characterized for its gelation time, swelling, and water uptake, as well as its morphological, chemical, and rheological properties; furthermore, blood- and cytocompatibility were assessed as per ISO 10993 (International Organization for Standardization). Printability, shape fidelity, and cell-laden printing was evaluated using the RegenHU 3D Discovery bioprinter. The results indicated the successful development of ADA–gelatin–PRP based bioink for 3D bioprinting and biofabrication applications.
AUTHOR Eltaher, Hoda M. and Abukunna, Fatima E. and Ruiz-Cantu, Laura and Stone, Zack and Yang, Jing and Dixon, James E.
Title Human-scale tissues with patterned vascular networks by additive manufacturing of sacrificial sugar-protein composites [Abstract]
Year 2020
Journal/Proceedings Acta Biomaterialia
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Combating necrosis, by supplying nutrients and removing waste, presents the major challenge for engineering large three-dimensional (3D) tissues. Previous elegant work used 3D printing with carbohydrate glass as a cytocompatible sacrificial template to create complex engineered tissues with vascular networks (Miller et al. 2012, Nature Materials). The fragile nature of this material compounded with the technical complexity needed to create high-resolution structures led us to create a flexible sugar-protein composite, termed Gelatin-sucrose matrix (GSM), to achieve a more robust and applicable material. Here we developed a low-range (25–37˚C) temperature sensitive formulation that can be moulded with micron-resolution features or cast during 3D printing to produce complex flexible filament networks forming sacrificial vessels. Using the temperature-sensitivity, we could control filament degeneration meaning GSM can be used with a variety of matrices and crosslinking strategies. Furthermore by incorporation of biocompatible crosslinkers into GSM directly, we could create thin endothelialized vessel walls and generate patterned tissues containing multiple matrices and cell-types. We also demonstrated that perfused vascular channels sustain metabolic function of a variety of cell-types including primary human cells. Importantly, we were able to construct vascularized human noses which otherwise would have been necrotic. Our material can now be exploited to create human-scale tissues for regenerative medicine applications. Statement of Significance Authentic and engineered tissues have demands for mass transport, exchanging nutrients and oxygen, and therefore require vascularization to retain viability and inhibit necrosis. Basic vascular networks must be included within engineered tissues intrinsically. Yet, this has been unachievable in physiologically-sized constructs with tissue-like cell densities until recently. Sacrificial moulding is an alternative in which networks of rigid lattices of filaments are created to prevent subsequent matrix ingress. Our study describes a biocompatible sacrificial sugar-protein formulation; GSM, made from mixtures of inexpensive and readily available bio-grade materials. GSM can be cast/moulded or bioprinted as sacrificial filaments that can rapidly dissolve in an aqueous environment temperature-sensitively. GSM material can be used to engineer viable and vascularized human-scale tissues for regenerative medicine applications.
AUTHOR Strauß, Svenja and Meutelet, Rafaela and Radosevic, Luka and Gretzinger, Sarah and Hubbuch, Jürgen
Title Image analysis as PAT-Tool for use in extrusion-based bioprinting [Abstract]
Year 2020
Journal/Proceedings Bioprinting
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The technology of bioprinting is arousing a growing interest in biopharmaceutical research and industry. In order to accelerate process development in the field of bioprinting, image-based analysis methods are non-invasive, time- and cost-saving tools which are usable for printer characterization, bioink printability evaluation, and process optimization. Image processing can also be used for the study of reproducibility, since reliable production is important in the transition from research to industrial application, and more precisely to clinical studies. This study revolves around the establishment of an automated and image-based line analysis method for bioprinting applications which enables an easy comparison of 3D-printed lines. Diverse rheological properties of bioinks and the printing process affect the geometry of the resulting object. The line represents a simple geometry, where the influence of the rheological properties and printing parameters is directly apparent. Therefore, a method for line analysis was developed on the basis of image recognition. At first, the method is tested for several substances such as Nivea®, pure and colored Kolliphor solutions, and two commercially available hydrogel formulations which can be used as bioinks. These are Biogelx™-ink-RGD by Biogelx and Cellink® Bioink by Cellink. The examination of limitations showed that transparent materials such as Kolliphor-based solutions cannot be analyzed with the developed method whereas opaque materials such as Nivea® and both bioinks can be analyzed. In the course of process characterization, the method was used to investigate the shrinkage behavior for both bionks. With the help of the line analysis tool, a shrinkage behavior of both bioinks was demonstrated and thus, process time could be identified as a critical process parameter.
AUTHOR Fisch, Philipp and Holub, Martin and Zenobi-Wong, Marcy
Title Improved accuracy and precision of bioprinting through progressive cavity pump-controlled extrusion [Abstract]
Year 2020
Journal/Proceedings bioRxiv
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Abstract
3D bioprinting has seen a tremendous growth in recent years in a variety of fields such as tissue and organ models, drug testing and regenerative medicine. This growth has led researchers and manufacturers to continuously advance and develop novel bioprinting techniques and materials. Although new bioprinting methods are emerging (e.g. contactless and volumetric bioprinting), micro-extrusion bioprinting remains the most widely used method. Micro-extrusion bioprinting, however, is still largely dependent on the conventional pneumatic extrusion process, which relies heavily on homogenous biomaterial inks and bioinks to maintain a constant material flowrate. Augmenting the functionality of the bioink with the addition of nanoparticles, cells or biopolymers can induce inhomogeneities resulting in uneven material flow during printing and/or clogging of the nozzle, leading to defects in the printed construct. In this work, we evaluated a novel extrusion technique based on a miniaturized progressive cavity pump. We compared the accuracy and precision of this system to the pneumatic extrusion system and tested both for their effect on cell viability after extrusion. The progressive cavity pump achieved a significantly higher accuracy and precision compared to the pneumatic system while maintaining good viability and was able to maintain its reliability independently of the bioink composition, printing speed or nozzle size. Progressive cavity pumps are a promising tool for bioprinting and could help provide standardized and validated bioprinted constructs while leaving the researcher more freedom in the design of the bioinks with increased functionality.
AUTHOR Rupp, Harald and Binder, Wolfgang H.
Title Multicomponent Stress-Sensing Composites Fabricated by 3D-Printing Methodologies [Abstract]
Year 2020
Journal/Proceedings Macromolecular Rapid Communications
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Abstract The preparation and characterization of mechanoresponsive, 3D-printed composites are reported using a dual-printing setup for both, liquid dispensing and fused-deposition-modeling. The here reported stress-sensing materials are based on high- and low molecular weight mechanophores, including poly(ε-caprolactone)-, polyurethane-, and alkyl(C11)-based latent copper(I)bis(N-heterocyclic carbenes), which can be activated by compression to trigger a fluorogenic, copper(I)-catalyzed azide/alkyne “click”-reaction of an azide-functionalized fluorescent dye inside a bulk polymeric material. Focus is placed on the printability and postprinting activity of the latent mechanophores and the fluorogenic “click”-components. The multicomponent specimen containing both, azide and alkyne, are manufactured via a 3D-printer to place the components separately inside the specimen into void spaces generated during the FDM-process, which subsequently are filled with liquids using a separate liquid dispenser, located within the same 3D-printing system. The low-molecular weight mechanophores bearing the alkyl-C11 chains display the best printability, yielding a mechanochemical response after the 3D-printing process.
AUTHOR Lee, Mihyun and Bae, Kraun and Levinson, Clara and Zenobi-Wong, Marcy
Title Nanocomposite bioink exploits dynamic covalent bonds between nanoparticles and polysaccharides for precision bioprinting [Abstract]
Year 2020
Journal/Proceedings Biofabrication
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Abstract
The field of bioprinting has made significant recent progress towards engineering tissues with increasing complexity and functionality. It remains challenging, however, to develop bioinks with optimal biocompatibility and good printing fidelity. Here, we demonstrate enhanced printability of a polymer-based bioink based on dynamic covalent linkages between nanoparticles (NPs) and polymers, which retains good biocompatibility. Amine-presenting silica NPs (ca. 45 nm) were added to a polymeric ink containing oxidized alginate (OxA). The formation of reversible imine bonds between amines on the NPs and aldehydes of OxA lead to significantly improved rheological properties and high printing fidelity. In particular, the yield stress increased with increasing amounts of NPs (14.5 Pa without NPs, 79 Pa with 2 wt% NPs). In addition, the presence of dynamic covalent linkages in the gel provided improved mechanical stability over 7 d compared to ionically crosslinked gels. The nanocomposite ink retained high printability and mechanical strength, resulting in generation of centimeter-scale porous constructs and an ear structure with overhangs and high structural fidelity. Furthermore, the nanocomposite ink supported both in vitro and in vivo maturation of bioprinted gels containing chondrocytes. This approach based on simple oxidation can be applied to any polysaccharide, thus the widely applicability of the method is expected to advance the field towards the goal of precision bioprinting.
AUTHOR Cernecu, Alexandra and Lungu, Adriana and Stancu, Izabela Cristina and Vasile, Eugeniu and Iovu, Horia
Title Polysaccharide-Based 3D Printing Inks Supplemented with Additives
Year 2020
Journal/Proceedings University Politechnica of Bucharest Scientific Bulletin
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AUTHOR Tan, Wen See and Shi, Qian and Chen, Shengyang and Bin Juhari, Muhammad Aidil and Song, Juha
Title Recyclable and biocompatible microgel-based supporting system for positive 3D freeform printing of silicone rubber [Abstract]
Year 2020
Journal/Proceedings Biomedical Engineering Letters
Reftype Tan2020
DOI/URL DOI
Abstract
Additive manufacturing (AM) of biomaterials has evolved from a rapid prototyping tool into a viable approach for the manufacturing of patient-specific implants over the past decade. It can tailor to the unique physiological and anatomical criteria of the patient’s organs or bones through precise controlling of the structure during the 3D printing. Silicone elastomers, which is a major group of materials in many biomedical implants, have low viscosities and can be printed with a special AM platform, known as freeform 3D printing systems. The freeform 3D printing systems are composed of a supporting bath and a printing material. Current supporting matrices that are either commercially purchased or synthesized were usually disposed of after retrieval of the printed part. In this work, we proposed a new and improved supporting matrix comprises of synthesized calcium alginate microgels produced via encapsulation which can be recycled, reused, and recovered for multiple prints, hence minimizing wastage and cost of materials. The dehydration tolerance of the calcium alginate microgels was improved through physical means by the addition of glycerol and chemical means by developing new calcium alginate microgels encapsulated with glycerol. The recyclability of the heated calcium alginate microgels was also enhanced by a rehydration step with sodium chloride solution and a recovery step with calcium chloride solution via the ion exchange process. We envisaged that our reusable and recyclable biocompatible calcium alginate microgels can save material costs, time, and can be applied in various freeform 3D printing systems.
AUTHOR Sanz-Fraile, Hector and Amorós, Susana and Mendizabal, Irene Isabel and Gálvez-Montón, Carolina and Prat-Vidal, Cristina and Bayés-Genís, Antoni and Navajas, Daniel and Farre, Ramon and Otero, Jorge
Title Silk-reinforced Collagen Hydrogels with Raised Multiscale Stiffness for Mesenchymal Cells 3D Culture [Abstract]
Year 2020
Journal/Proceedings Tissue Engineering Part A
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Abstract
Type I collagen hydrogels are of high interest in tissue engineering. With the evolution of 3D bioprinting technologies, a high number of collagen-based scaffolds have been reported for the development of 3D cell cultures. A recent proposal was to mix collagen with silk fibroin derived from Bombyx Mori silkworm. Nevertheless, due to the difficulties in the preparation and the characteristics of the protein, several problems like phase separation and collagen denaturation appears during the procedure. Therefore, the common solution is to diminish the concentration of collagen although in that way the most biologically relevant component is reduced. In the present work, we present a new, simple and effective method to develop a collagen-silk hybrid hydrogel with high collagen concentration and with increased stiffness approaching that of natural tissues, which could be of high interest for the development of cardiac patches for myocardial regeneration and for preconditioning of mesenchymal stem cells to improve their therapeutic potential. Sericin in the silk was preserved by using a physical solubilizing procedure which results in a preserved fibrous structure of type I collagen, as shown by ultrastructural imaging. The macro- and micromechanical properties of the hybrid hydrogels measured by tensile stretch and Atomic Force Microscopy respectively, showed a more than two-fold stiffening as compared with collagen-only hydrogels. Rheological measurements showed improved printability properties for the developed biomaterial. The suitability of the hydrogels for 3D cell culture was assessed by 3D bioprinting bone marrow-derived mesenchymal stem cells cultured within the scaffolds. The result was a biomaterial with improved printability characteristics that better resembled the mechanical properties of natural soft tissues while preserving biocompatibility owing to the high concentration of collagen.
AUTHOR Li, Huijun and Tan, Yu Jun and Kiran, Raj and Tor, Shu Beng and Zhou, Kun
Title Submerged and non-submerged 3D bioprinting approaches for the fabrication of complex structures with the hydrogel pair GelMA and alginate/methylcellulose [Abstract]
Year 2020
Journal/Proceedings Additive Manufacturing
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Abstract
The extrusion-based bioprinting of hydrogels such as gelatin methacrylate (GelMA) into structures with complex shape suffers from poor printability due to their low viscosity. The present study deals with hydrogel materials by using the mixture of cell-laden photopolymerizable GelMA as a main printing material and the mixture of alginate and methylcellulose (Alg/MC) as a support material because of its high viscosity and good thixotropic property. One extrusion-based approach is developed by printing the two mixtures into structures in an alternating layer-by-layer manner, with the electrostatic interactions between polycationic GelMA and polyanionic Alg/MC contributing to the integrity of the structures. The final printed structures are exposed to ultraviolet (UV) light to form crosslinks in GelMA through photopolymerization for further structural strengthening. The one-time UV exposure minimizes cell damage in cell-GelMA, demonstrating an advantage over those in previously reported studies that required repeated UV exposures upon the printing of each layer of a structure. The other approach is developed by submerging the extrusion nozzle into a bath of Alg/MC to print cell-laden GelMA structures, which, upon printing completion, are also subject to one-time UV exposure before the removal of the support material Alg/MC. A flower with living cells is printed to demonstrate the capability of the second approach of fabricating structures with geometric complexity. The structures printed using both approaches demonstrate a well-maintained shape fidelity, structural integrity and cell viability of over 93% up to five culturing days. The proposed two printing approaches based on the cell-GelMA and Alg/MC pair will be beneficial for exploring new opportunities in bioprinting.
AUTHOR Schwab, Andrea and Helary, Christophe and Richards, Geoff and Alini, Mauro and Eglin, David and D{textquoteright}Este, Matteo
Title Tissue mimetic hyaluronan bio-ink containing oriented collagen fibers to modulate hMSC spreading and differentiation [Abstract]
Year 2020
Journal/Proceedings bioRxiv
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Abstract
Biofabrication is providing scientists and clinicians the ability to produce engineered tissues with desired shapes, chemical and biological gradients. Typical resolutions achieved with extrusion-based bioprinting are at the macroscopic level. However, for capturing the fibrillar nature of the extracellular matrix (ECM), it is necessary to arrange ECM components at smaller scales, down to the sub-micron and the molecular level.In this study, we introduce a (bio)ink containing hyaluronan (HA) as tyramine derivative (THA) and collagen (Col). Similarly to other connective tissues, in this (bio)ink Col is present in fibrillar form and HA as viscoelastic space filler. THA was enzymatically crosslinked under mild conditions allowing simultaneous Col fibrillogenesis, thus achieving a homogeneous distribution of Col fibrils within the viscoelastic HA-based matrix. THA-Col composite displayed synergistic properties in terms of storage modulus and shear-thinning, translating into good printability.Shear-induced alignment of the Col fibrils along the printing direction was achieved and quantified via immunofluorescence and second harmonic generation.Cell-free and cell-laden constructs were printed and characterized, analyzing the influence of the controlled microscopic anisotropy on cell behavior and chondrogenic differentiation.THA-Col showed cell instructive properties modulating hMSC adhesion, morphology and sprouting from spheroids stimulated by the presence and the orientation of Col fibers. Actin filament staining showed that hMSCs embedded into aligned constructs displayed increased cytoskeleton alignment along the fibril direction. Based on gene expression of cartilage/bone markers and matrix production, hMSCs embedded into the bioink displayed chondrogenic differentiation comparable or superior to standard pellet culture by means of proteoglycan production (Safranin O staining and proteoglycan quantification) as well as increase in cartilage related genes.The possibility of printing matrix components with control over microscopic alignment brings biofabrication one step closer to capturing the complexity of native tissues.
AUTHOR Shapira, Assaf and Noor, Nadav and Oved, Hadas and Dvir, Tal
Title Transparent support media for high resolution 3D printing of volumetric cell-containing ECM structures [Abstract]
Year 2020
Journal/Proceedings Biomedical Materials
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Abstract
3D bioprinting may revolutionize the field of tissue engineering by allowing fabrication of bio-structures with high degree of complexity, fine architecture and heterogeneous composition. The printing substances in these processes are mostly based on biomaterials and living cells. As such, they generally possess weak mechanical properties and thus must be supported during fabrication in order to prevent the collapse of large, volumetric multi-layered printouts. In this work, we characterize a uniquely formulated media used to support printing of extracellular matrix-based biomaterials. We show that a hybrid material, comprised of calcium-alginate nanoparticles and xanthan gum, presents superb qualities that enable printing at high resolution of down to 10 microns, allowing fabrication of complex constructs and cellular structures. This hybrid also presents an exclusive combination of desirable properties such as biocompatibility, high transparency, stability at a wide range of temperatures and amenability to delicate extraction procedures. Moreover, as fabrication of large, volumetric biological structures may require hours and even days to accomplish, we have demonstrated that the hybrid medium can support prolonged, precise printing for at least 18 hours. All these qualities make it a promising support medium for 3D printing of tissues and organs.
AUTHOR Döhler, Diana and Kang, Jiheong and Cooper, Chris Brittain and Tok, Jeffrey B.-H. and Rupp, Harald and Binder, Wolfgang H. and Bao, Zhenan
Title Tuning the Self-Healing Response of Poly(dimethylsiloxane)-Based Elastomers [Abstract]
Year 2020
Journal/Proceedings ACS Appl. Polym. Mater.
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DOI/URL DOI
Abstract
We present a comprehensive investigation of mechanical properties of supramolecular polymer networks with rationally developed multistrength hydrogen-bonding interactions. Self-healing poly(dimethylsiloxane) (PDMS)-based elastomers with varying elasticity, fracture toughness, and the ability to dissipate strain energy through the reversible breakage and re-formation of the supramolecular interactions were obtained. By changing the ratio between isophorone diisocyanate (IU), 4,4′-methylenebis(cyclohexyl isocyanate) (MCU), and 4,4′-methylenebis(phenyl isocyanate) (MPU) and by varying the molecular weight of the PDMS precursor, we obtained a library of poly(urea)s to study the interplay of mechanical performance and self-healability. The Young’s moduli of the presented materials ranged between 0.4 and 13 MPa and increased with decreasing molecular weight of the PDMS precursor and increasing content of MCU or MPU units related to the formation of stronger hydrogen-bonding interactions. By exchanging MPU against MCU units, we achieved an optimum balance between mechanical properties and self-healing performance, and by the additional reduction of the molecular weight of the precursor polymer, a minimum recovery of 80% in stress within 12 h at room temperature was observed. Selected poly(urea)s could be processed via 3D printing by the conventional extrusion method, obtaining dimensionally stable and freestanding objects. We present a comprehensive investigation of mechanical properties of supramolecular polymer networks with rationally developed multistrength hydrogen-bonding interactions. Self-healing poly(dimethylsiloxane) (PDMS)-based elastomers with varying elasticity, fracture toughness, and the ability to dissipate strain energy through the reversible breakage and re-formation of the supramolecular interactions were obtained. By changing the ratio between isophorone diisocyanate (IU), 4,4′-methylenebis(cyclohexyl isocyanate) (MCU), and 4,4′-methylenebis(phenyl isocyanate) (MPU) and by varying the molecular weight of the PDMS precursor, we obtained a library of poly(urea)s to study the interplay of mechanical performance and self-healability. The Young’s moduli of the presented materials ranged between 0.4 and 13 MPa and increased with decreasing molecular weight of the PDMS precursor and increasing content of MCU or MPU units related to the formation of stronger hydrogen-bonding interactions. By exchanging MPU against MCU units, we achieved an optimum balance between mechanical properties and self-healing performance, and by the additional reduction of the molecular weight of the precursor polymer, a minimum recovery of 80% in stress within 12 h at room temperature was observed. Selected poly(urea)s could be processed via 3D printing by the conventional extrusion method, obtaining dimensionally stable and freestanding objects.
AUTHOR Alison, Lauriane and Menasce, Stefano and Bouville, Florian and Tervoort, Elena and Mattich, Iacopo and Ofner, Alessandro and Studart, André R.
Title 3D printing of sacrificial templates into hierarchical porous materials [Abstract]
Year 2019
Journal/Proceedings Scientific Reports
Reftype Alison2019
DOI/URL DOI
Abstract
Hierarchical porous materials are widespread in nature and find an increasing number of applications as catalytic supports, biological scaffolds and lightweight structures. Recent advances in additive manufacturing and 3D printing technologies have enabled the digital fabrication of porous materials in the form of lattices, cellular structures and foams across multiple length scales. However, current approaches do not allow for the fast manufacturing of bulk porous materials featuring pore sizes that span broadly from macroscopic dimensions down to the nanoscale. Here, ink formulations are designed and investigated to enable 3D printing of hierarchical materials displaying porosity at the nano-, micro- and macroscales. Pores are generated upon removal of nanodroplets and microscale templates present in the initial ink. Using particles to stabilize the droplet templates is key to obtain Pickering nanoemulsions that can be 3D printed through direct ink writing. The combination of such self-assembled templates with the spatial control offered by the printing process allows for the digital manufacturing of hierarchical materials exhibiting thus far inaccessible multiscale porosity and complex geometries.
AUTHOR Rupp, Harald and Döhler, Diana and Hilgeroth, Philipp and Mahmood, Nasir and Beiner, Mario and Binder, Wolfgang H.
Title 3D Printing of Supramolecular Polymers: Impact of Nanoparticles and Phase Separation on Printability [Abstract]
Year 2019
Journal/Proceedings Macromolecular Rapid Communications
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DOI/URL DOI
Abstract
Abstract 3D printing of linear and three-arm star supramolecular polymers with attached hydrogen bonds and their nanocomposites is reported. The concept is based on hydrogen-bonded supramolecular polymers, known to form nano-sized micellar clusters. Printability is based on reversible thermal- and shear-induced dissociation of a supramolecular polymer network, which generates stable and self-supported structures after printing, as checked via melt-rheology and X-ray scattering. The linear and three-arm star poly(isobutylene)s PIB-B2 (Mn = 8500 g mol −1), PIB-B3 (Mn = 16 000 g mol −1), and linear poly(ethylene glycol)s PEG-B2 (Mn = 900 g mol−1, 8500 g mol −1) are prepared and then probed by melt-rheology to adjust the viscosity to address the proper printing window. The supramolecular PIB polymers show a rubber-like behavior and are able to form self-supported 3D printed objects at room temperature and below, reaching polymer strand diameters down to 200–300 µm. Nanocomposites of PIB-B2 with silica nanoparticles (12 nm, 5–15 wt%) are generated, in turn leading to an improvement of their shape persistence. A blend of the linear polymer PIB-B2 and the three-arm star polymer PIB-B3 (ratio ≈ 3/1 mol) reaches an even higher structural stability, able to build free-standing structures.
AUTHOR Augurio, Adriana and Cortelletti, Paolo and Tognato, Riccardo and Rios, Anne and Levato, Riccardo and Malda, Jos and Alini, Mauro and Eglin, David and Giancane, Gabriele and Speghini, Adolfo and Serra, Tiziano
Title A Multifunctional Nanocomposite Hydrogel for Endoscopic Tracking and Manipulation [Abstract]
Year 2019
Journal/Proceedings Advanced Intelligent Systems
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Abstract
In this work, the fabrication of multi-responsive and hierarchically organized nanomaterial by using core-shell SrF2 upconverting nanoparticles, doped with Yb3+, Tm3+, Nd3+ incorporated into gelatin methacryloyl matrix, is reported. Upon 800 nm excitation, deep monitoring of 3D printed constructs is demonstrated. Addition of magnetic self-assembly of iron oxide nanoparticles within the hydrogel provides anisotropic structuration from the nano- to the macro-scale and magnetic responsiveness permitting remote manipulation. The present study provides a new strategy for the fabrication of a novel highly organized multi-responsive material using additive manufacturing, which could have important implications in biomedicine. This article is protected by copyright. All rights reserved.
AUTHOR Cernencu, Alexandra I. and Lungu, Adriana and Stancu, Izabela-Cristina and Serafim, Andrada and Heggset, Ellinor and Syverud, Kristin and Iovu, Horia
Title Bioinspired 3D printable pectin-nanocellulose ink formulations [Abstract]
Year 2019
Journal/Proceedings Carbohydrate Polymers
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DOI/URL URL DOI
Abstract
The assessment of several ink formulations for 3D printing based on two natural macromolecular compounds is presented. In the current research we have exploited the fast crosslinking potential of pectin and the remarkable shear-thinning properties of carboxylated cellulose nanofibrils, which is known to induce a desired viscoelastic behavior. Prior to 3D printing, the viscoelastic properties of the polysaccharide inks were evaluated by rheological measurements and injectability tests. The reliance of the printing parameters on the ink composition was established through one-dimensional lines printing, the base units of 3D-structures. The performance of the 3D-printed structures after ionic cross-linking was evaluated in terms of mechanical properties and rehydration behavior. MicroCT was also used to evaluate the morphology of the 3D-printed objects regarding the effect of pectin/nanocellulose ratio on the geometrical features of scaffolds. The proportionality between the two polymers proved to be the determining factor for the firmness and strength of the printed objects.
AUTHOR Creusen, Guido and Roshanasan, Ardeshir and Garcia Lopez, Javier and Peneva, Kalina and Walther, Andreas
Title Bottom-up design of model network elastomers and hydrogels from precise star polymers [Abstract]
Year 2019
Journal/Proceedings Polymer Chemistry
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Abstract
We introduce a platform for the simultaneous design of model network hydrogels and bulk elastomers based on well-defined water-soluble star polymers with a low glass transition temperature (Tg). This platform is enabled via the development of a synthetic route to a new family of 4-arm star polymers based on water-soluble poly(triethylene glycol methyl ether acrylate) (p(mTEGA)){,} which after quantitative introduction of functional end-groups can serve as suitable building blocks for model network formation. We first describe in detail the synthesis of highly defined star polymers using light and Cu-wire mediated Cu-based reversible deactivation radical polymerization. The resulting polymers exhibit narrow dispersities and controlled arm length at very high molecular weights{,} and feature a desirable low Tg of −55 °C. Subsequently{,} we elucidate the rational design of the stiffness and elasticity in covalent model network elastomers and hydrogels formed by fast photo-crosslinking for different arm lengths{,} and construct thermally reversible model network hydrogels based on dynamic supramolecular bonds. In addition{,} we describe preliminary 3D-printing applications. This work provides a key alternative to commonly used star-poly(ethylene glycol) (PEG) for model hydrogel networks{,} and demonstrates access to new main and side chain chemistries{,} thus chain stiffnesses and entanglement molecular weight{,} and{,} critically{,} enables the simultaneous study of the mechanical behavior of bulk network elastomers and swollen hydrogels with the same network topology. In a wider perspective{,} this work also highlights the need for advancing precision polymer chemistry to allow for an understanding of architectural control for the rational design of functional mechanical network materials.
AUTHOR Cofiño, Carla and Perez-Amodio, Soledad and Semino, Carlos E. and Engel, Elisabeth and Mateos-Timoneda, Miguel A.
Title Development of a Self-Assembled Peptide/Methylcellulose-Based Bioink for 3D Bioprinting [Abstract]
Year 2019
Journal/Proceedings Macromolecular Materials and Engineering
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Abstract
Abstract The introduction of 3D bioprinting to fabricate living constructs with tailored architecture has provided a new paradigm for biofabrication, with the potential to overcome several drawbacks of conventional scaffold-based tissue regeneration strategies. Hydrogel-based materials are suitable candidates regarding cell biocompatibility but often display poor mechanical properties. Self-assembling peptides are a promising source of biomaterials to be used as 3D scaffolds based on their similarity to extracellular matrices (structurally and mechanically). In this study, an advanced bioink for biofabrication is presented based on the optimization of a RAD16-I-based biomaterial. The strategy followed to build 3D predefined structures by 3D printing is based on an enhancement of bioink viscosity by adding methylcellulose (MC) to a RAD16-I solution. The resultant constructs display high shape fidelity and stability and embedded human mesenchymal stem cells present high viability after 7 days of culture. Moreover, cells are also able to differentiate to the adipogenic lineage, suggesting the suitability of this novel biomaterial for soft tissue engineering applications.
AUTHOR Tondera, Christoph and Akbar, Teuku Fawzul and Thomas, Alvin Kuriakose and Lin, Weilin and Werner, Carsten and Busskamp, Volker and Zhang, Yixin and Minev, Ivan R.
Title Highly Conductive, Stretchable, and Cell-Adhesive Hydrogel by Nanoclay Doping [Abstract]
Year 2019
Journal/Proceedings Small
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DOI/URL DOI
Abstract
Abstract Electrically conductive materials that mimic physical and biological properties of tissues are urgently required for seamless brain–machine interfaces. Here, a multinetwork hydrogel combining electrical conductivity of 26 S m−1, stretchability of 800%, and tissue-like elastic modulus of 15 kPa with mimicry of the extracellular matrix is reported. Engineering this unique set of properties is enabled by a novel in-scaffold polymerization approach. Colloidal hydrogels of the nanoclay Laponite are employed as supports for the assembly of secondary polymer networks. Laponite dramatically increases the conductivity of in-scaffold polymerized poly(ethylene-3,4-diethoxy thiophene) in the absence of other dopants, while preserving excellent stretchability. The scaffold is coated with a layer containing adhesive peptide and polysaccharide dextran sulfate supporting the attachment, proliferation, and neuronal differentiation of human induced pluripotent stem cells directly on the surface of conductive hydrogels. Due to its compatibility with simple extrusion printing, this material promises to enable tissue-mimetic neurostimulating electrodes.
AUTHOR Apelgren, Peter and Karabulut, Erdem and Amoroso, Matteo and Mantas, Athanasios and Martínez Ávila, Héctor and Kölby, Lars and Kondo, Tetsuo and Toriz, Guillermo and Gatenholm, Paul
Title In Vivo Human Cartilage Formation in Three-Dimensional Bioprinted Constructs with a Novel Bacterial Nanocellulose Bioink [Abstract]
Year 2019
Journal/Proceedings ACS Biomaterials Science & Engineering
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Abstract
Bacterial nanocellulose (BNC) is a 3D network of nanofibrils exhibiting excellent biocompatibility. Here, we present the aqueous counter collision (ACC) method of BNC disassembly to create bioink with suitable properties for cartilage-specific 3D-bioprinting. BNC was disentangled by ACC, and fibril characteristics were analyzed. Bioink printing fidelity and shear-thinning properties were evaluated. Cell-laden bioprinted grid constructs (5 × 5 × 1 mm3) containing human nasal chondrocytes (10 M mL-1) were implanted in nude mice and explanted after 30 and 60 days. Both ACC and hydrolysis resulted in significantly reduced fiber lengths, with ACC resulting in longer fibrils and fewer negative charges relative to hydrolysis. Moreover, ACC-BNC bioink showed outstanding printability, postprinting mechanical stability, and structural integrity. In vivo, cell-laden structures were rapidly integrated, maintained structural integrity, and showed chondrocyte proliferation, with 32.8 ± 13.8 cells per mm2 observed after 30 days and 85.6 ± 30.0 cells per mm2 at day 60 (p = 0.002). Furthermore, a full-thickness skin graft was attached and integrated completely on top of the 3D-bioprinted construct. The novel ACC disentanglement technique makes BNC biomaterial highly suitable for 3D-bioprinting and clinical translation, suggesting cell-laden 3D-bioprinted ACC-BNC as a promising solution for cartilage repair. Bacterial nanocellulose (BNC) is a 3D network of nanofibrils exhibiting excellent biocompatibility. Here, we present the aqueous counter collision (ACC) method of BNC disassembly to create bioink with suitable properties for cartilage-specific 3D-bioprinting. BNC was disentangled by ACC, and fibril characteristics were analyzed. Bioink printing fidelity and shear-thinning properties were evaluated. Cell-laden bioprinted grid constructs (5 × 5 × 1 mm3) containing human nasal chondrocytes (10 M mL-1) were implanted in nude mice and explanted after 30 and 60 days. Both ACC and hydrolysis resulted in significantly reduced fiber lengths, with ACC resulting in longer fibrils and fewer negative charges relative to hydrolysis. Moreover, ACC-BNC bioink showed outstanding printability, postprinting mechanical stability, and structural integrity. In vivo, cell-laden structures were rapidly integrated, maintained structural integrity, and showed chondrocyte proliferation, with 32.8 ± 13.8 cells per mm2 observed after 30 days and 85.6 ± 30.0 cells per mm2 at day 60 (p = 0.002). Furthermore, a full-thickness skin graft was attached and integrated completely on top of the 3D-bioprinted construct. The novel ACC disentanglement technique makes BNC biomaterial highly suitable for 3D-bioprinting and clinical translation, suggesting cell-laden 3D-bioprinted ACC-BNC as a promising solution for cartilage repair.
AUTHOR Zhuang, Pei and Ng, Wei Long and An, Jia and Chua, Chee Kai and Tan, Lay Poh
Title Layer-by-layer ultraviolet assisted extrusion-based (UAE) bioprinting of hydrogel constructs with high aspect ratio for soft tissue engineering applications [Abstract]
Year 2019
Journal/Proceedings PLOS ONE
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DOI/URL DOI
Abstract
One of the major challenges in the field of soft tissue engineering using bioprinting is fabricating complex tissue constructs with desired structure integrity and mechanical property. To accomplish such requirements, most of the reported works incorporated reinforcement materials such as poly(ϵ-caprolactone) (PCL) polymer within the 3D bioprinted constructs. Although this approach has made some progress in constructing soft tissue-engineered scaffolds, the mechanical compliance mismatch and long degradation period are not ideal for soft tissue engineering. Herein, we present a facile bioprinting strategy that combines the rapid extrusion-based bioprinting technique with an in-built ultraviolet (UV) curing system to facilitate the layer-by-layer UV curing of bioprinted photo-curable GelMA-based hydrogels to achieve soft yet stable cell-laden constructs with high aspect ratio for soft tissue engineering. GelMA is supplemented with a viscosity enhancer (gellan gum) to improve the bio-ink printability and shape fidelity while maintaining the biocompatibility before crosslinking via a layer-by-layer UV curing process. This approach could eventually fabricate soft tissue constructs with high aspect ratio (length to diameter) of ≥ 5. The effects of UV source on printing resolution and cell viability were also studied. As a proof-of-concept, small building units (3D lattice and tubular constructs) with high aspect ratio are fabricated. Furthermore, we have also demonstrated the ability to perform multi-material printing of tissue constructs with high aspect ratio along both the longitudinal and transverse directions for potential applications in tissue engineering of soft tissues. This layer-by-layer ultraviolet assisted extrusion-based (UAE) Bioprinting may provide a novel strategy to develop soft tissue constructs with desirable structure integrity.
AUTHOR Markstedt, Kajsa and Håkansson, Karl and Toriz, Guillermo and Gatenholm, Paul
Title Materials from trees assembled by 3D printing – Wood tissue beyond nature limits [Abstract]
Year 2019
Journal/Proceedings Applied Materials Today
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DOI/URL URL DOI
Abstract
Materials from trees have the potential to replace fossil based and other non-sustainable materials in everyday products, thus transforming the society back to a bioeconomy. This paper presents a 3D printing platform which mimics wood biogenesis for the assembly of wood biopolymers into wood-like hierarchical composites. The genome was substituted with G-code, the programming language which controls how the 3D printer assembles material. The rosette was replaced by the printer head for extrusion of cellulose. Instead of microtubules guiding the alignment of cellulose, the printing direction was guided by an x/y stage, thus mimicking the microfibril angle. The printed structures were locked by an enzymatic crosslinking reaction similar to what occurs in the cell wall upon lignification. Hierarchical structures characteristic for wood were designed and printed with control of density, swelling and directional strength. Accelerating the development of the 3D printing technology helps realize the circular bioeconomy where garments, packaging, furniture and entire houses are manufactured by 3D printing wood.
AUTHOR Zhou, Miaomiao and Lee, Bae Hoon and Tan, Yu Jun and Tan, Lay Poh
Title Microbial transglutaminase induced controlled crosslinking of gelatin methacryloyl to tailor rheological properties for 3D printing [Abstract]
Year 2019
Journal/Proceedings Biofabrication
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DOI/URL DOI
Abstract
Gelatin methacryloyl (GelMA) is a versatile biomaterial that has been shown to possess many advantages such as good biocompatibility, support for cell growth, tunable mechanical properties, photocurable capability, and low material cost. Due to these superior properties, much research has been carried out to develop GelMA as a bioink for bioprinting. However, there are still many challenges, and one major challenge is the control of its rheological properties to yield good printability. Herein, this study presents a strategy to control the rheology of GelMA through partial enzymatic crosslinking. Unlike other enzymatic crosslinking strategies where the rheological properties could not be controlled once reaction takes place, we could, to a large extent, keep the rheological properties stable by introducing a deactivation step after obtaining the optimized rheological properties. Ca2+-independent microbial transglutaminase (MTGase) was introduced to partially catalyze covalent bond formation between chains of GelMA. The enzyme was then deactivated to prevent further uncontrolled crosslinking that would render the hydrogel not printable. After printing, a secondary post-printing crosslinking step (photo crosslinking) was then introduced to ensure long-term stability of the printed structure for subsequent cell studies. Biocompatibility studies carried out using cells encapsulated in the printed structure showed excellent cell viability for at least 7 d. This strategy for better control of rheological properties of GelMA could more significantly enhance the usability of this material as bioink for bioprinting of cell-laden structures for soft tissue engineering.
AUTHOR Pan, Houwen Matthew and Chen, Shengyang and Jang, Tae-Sik and Han, Win Tun and Jung, Hyun-do and Li, Yaning and Song, Juha
Title Plant seed-inspired cell protection, dormancy, and growth for large-scale biofabrication [Abstract]
Year 2019
Journal/Proceedings Biofabrication
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DOI/URL DOI
Abstract
Biofabrication technologies have endowed us with the capability to fabricate complex biological constructs. However, cytotoxic biofabrication conditions have been a major challenge for their clinical application, leading to a trade-off between cell viability and scalability of biofabricated constructs. Taking inspiration from nature, we proposed a cell protection strategy which mimicks the protected and dormant state of plant seeds in adverse external conditions and their germination in response to appropriate environmental cues. Applying this bioinspired strategy to biofabrication, we successfully preserved cell viability and enhanced the seeding of cell-laden biofabricated constructs via a cytoprotective pyrogallol (PG)-alginate encapsulation system. Our cytoprotective encapsulation technology utilizes PG-triggered sporulation and germination processes to preserve cells, is mechanically robust, chemically resistant, and highly customizable to adequately match cell protectability with cytotoxicity of biofabrication conditions. More importantly, the facile and tunable decapsulation of our PG-alginate system allows for effective germination of dormant cells, under typical culture conditions. With this approach, we have successfully achieved a biofabrication process which is reproducible, scalable, and provided a practical solution for off-the-shelf availability, shipping and temporary storage of fabricated bio-constructs.
AUTHOR Rotbaum, Y. and Puiu, C. and Rittel, D. and Domingos, M.
Title Quasi-static and dynamic in vitro mechanical response of 3D printed scaffolds with tailored pore size and architectures [Abstract]
Year 2019
Journal/Proceedings Materials Science and Engineering: C
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DOI/URL URL DOI
Abstract
Scaffold-based Tissue Engineering represents the most promising approach for the regeneration of load bearing skeletal tissues, in particular bone and cartilage. Scaffolds play major role in this process by providing a physical template for cells to adhere and proliferate whilst ensuring an adequate biomechanical support at the defect site. Whereas the quasi static mechanical properties of porous polymeric scaffolds are well documented, the response of these constructs under high strain compressive rates remain poorly understood. Therefore, this study investigates, for the first time, the influence of pore size and geometry on the mechanical behaviour of Polycaprolactone (PCL) scaffolds under quasi static and dynamic conditions. 3D printed scaffolds with varied pore sizes and geometries were obtained using different filament distances (FD) and lay-down patterns, respectively. In particular, by fixing the lay-down pattern at 0/90° and varying the FD between 480 and 980 μm it was possible to generate scaffolds with square pores with dimensions in the range of 150–650 μm and porosities of 59–79%. On the other hand, quadrangular, hexagonal, triangular and complex pore geometries with constant porosity (approx. 70%) were obtained at a fixed FD of 680 μm and imposing four different lay-down patterns of 0/90, 0/60/120, 0/45/90/135 and 0/30/60/90/120/150°, respectively. The mechanical response of printed scaffolds was assessed under two different compression loading regimes spanning five distinct strain rates, from 10−2 to 2000 s−1, using two different apparatus: a conventional screw-driven testing machine (Instron 4483) and a Split Hopkinson pressure bar (SHPB) equipped with a set of A201 Flexi-force™ (FF) force sensors and a pulse shaper. Our results show that the mechanical properties of PCL scaffolds are not strain rate sensitive between 1300 and 2000 s−1 and these strongly depend on the pore size (porosity) rather than pore geometry. Those findings are extremely relevant for the engineering of bone tissue scaffolds with enhanced mechanical stability by providing new data describing the mechanical response of these constructs at high strain rates as well as the at the transition between quasi static and dynamic regimes.
AUTHOR Gloria, Antonio and Frydman, B. and Lamas, Miguel L. and Serra, Armenio C. and Martorelli, Massimo and Coelho, Jorge F. J. and Fonseca, Ana C. and Domingos, M.
Title The influence of poly(ester amide) on the structural and functional features of 3D additive manufactured poly(ε-caprolactone) scaffolds [Abstract]
Year 2019
Journal/Proceedings Materials Science and Engineering: C
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DOI/URL URL DOI
Abstract
The current research reports for the first time the use of blends of poly(ε-caprolactone) (PCL) and poly(ester amide) (PEA) for the fabrication of 3D additive manufactured scaffolds. Tailor made PEA was synthesized to afford fully miscible blends of PCL and PEA using different percentages (5, 10, 15 and 20% w/w). Stability, characteristic temperatures and material's compatibility were studied through thermal analyses (i.e., TGA, DSC). Even though DMTA and static compression tests demonstrated the possibility to improve the storage modulus, Young's modulus and maximum stress by increasing the amount of PEA, a decrease of hardness was found beyond a threshold concentration of PEA as the lowest values were achieved for PCL/PEA (20% w/w) scaffolds (from 0.39 ± 0.03 GPa to 0.21 ± 0.02 GPa in the analysed load range). The scaffolds presented a controlled morphology and a fully interconnected network of internal channels. The water contact angle measurements showed a clear increase of hydrophilicity resulting from the addition of PEA. This result was further corroborated with the improved adhesion and proliferation of human mesenchymal stem cells (hMSCs). The presence of PEA also influenced the cell morphology. Better cell spreading and a much higher and homogenous number of cells were observed for PCL/PEA scaffolds when compared to PCL ones.
AUTHOR Gretzinger, Sarah and Beckert, Nicole and Gleadall, Andrew and Lee-Thedieck, Cornelia and Hubbuch, Jürgen
Title 3D bioprinting – Flow cytometry as analytical strategy for 3D cell structures [Abstract]
Year 2018
Journal/Proceedings Bioprinting
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DOI/URL URL DOI
Abstract
The importance of 3D printing technologies increased significantly over the recent years. They are considered to have a huge impact in regenerative medicine and tissue engineering, since 3D bioprinting enables the production of cell-laden 3D scaffolds. Transition from academic research to pharmaceutical industry or clinical applications, however, is highly dependent on developing a robust and well-known process, while maintaining critical cell characteristics. Hence, a directed and systematic approach to 3D bioprinting process development is required, which also allows for the monitoring of these cell characteristics. This work presents the development of a flow cytometry-based analytical strategy as a tool for 3D bioprinting research. The development was based on a model process using a commercially available alginate-based bioink, the β-cell line INS-1E, and direct dispensing as 3D bioprinting method. We demonstrated that this set-up enabled viability and proliferation analysis. Additionally, use of an automated sampler facilitated high-throughput screenings. Finally, we showed that each process step, e.g. suspension of cells in bioink or 3D printing, cross-linking of the alginate scaffold after printing, has a crucial impact on INS-1E viability. This reflects the importance of process optimization in 3D bioprinting and the usefulness of the flow cytometry-based analytical strategy described here. The presented strategy has a great potential as a cell characterisation tool for 3D bioprinting and may contribute to a more directed process development.
AUTHOR Petta, D. and Armiento, A. R. and Grijpma, D. and Alini, M. and Eglin, D. and D'Este, M.
Title 3D bioprinting of a hyaluronan bioink through enzymatic-and visible light-crosslinking [Abstract]
Year 2018
Journal/Proceedings Biofabrication
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DOI/URL DOI
Abstract
Extrusion-based three-dimensional bioprinting relies on bioinks engineered to combine viscoelastic properties for extrusion and shape retention, and biological properties for cytocompatibility and tissue regeneration. To satisfy these conflicting requirements, bioinks often utilize either complex mixtures or complex modifications of biopolymers. In this paper we introduce and characterize a bioink exploiting a dual crosslinking mechanism, where an enzymatic reaction forms a soft gel suitable for cell encapsulation and extrusion, while a visible light photo-crosslinking allows shape retention of the printed construct. The influence of cell density and cell type on the rheological and printability properties was assessed correlating the printing outcomes with the damping factor, a rheological characteristic independent of the printing system. Stem cells, chondrocytes and fibroblasts were encapsulated, and their viability was assessed up to 14 days with live/dead, alamar blue and trypan blue assays. Additionally, the impact of the printing parameters on cell viability was investigated. Owing to its straightforward preparation, low modification, presence of two independent crosslinking mechanisms for tuning shear-thinning independently of the final shape fixation, the use of visible green instead of UV light, the possibility of encapsulating and sustaining the viability of different cell types, the hyaluronan bioink here presented is a valid biofabrication tool for producing 3D printed tissue-engineered constructs.
AUTHOR Aied, Ahmed and Song, Wenhui and Wang, Wenxin and Baki, Abdulrahman and Sigen, A.
Title 3D Bioprinting of stimuli-responsive polymers synthesised from DE-ATRP into soft tissue replicas [Abstract]
Year 2018
Journal/Proceedings Bioprinting
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DOI/URL URL DOI
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.
AUTHOR Li, Huijun and Tan, Yu Jun and Li, Lin
Title A strategy for strong interface bonding by 3D bioprinting of oppositely charged κ-carrageenan and gelatin hydrogels [Abstract]
Year 2018
Journal/Proceedings Carbohydrate Polymers
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Abstract
A promising approach for improving the interfacial bonding of a three-dimensionally (3D) printed multilayered structure has been investigated by taking advantage of the electrostatic interactions between two hydrogels with oppositely charges. Here, two hydrogels namely gelatin and κ-carrageenan, which are the cationic and anionic hydrogels respectively, are used. It is found that the interfacial bonding strength between these two oppositely charged hydrogels is significantly higher than that of a bilayered gelatin or a bilayered κ-carrageenan. The bioprinted multilayered κ-carrageenan-gelatin hydrogel construct demonstrates a very good biocompatibility and a good structure integrity at 37 °C. Our strategy also overcomes the limitation of using gelatin for bio-fabrication at 37 °C, without further post crosslinking.
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 [Abstract]
Year 2018
Journal/Proceedings Biomaterials Science
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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.
AUTHOR García-Lizarribar, Andrea and Fernández-Garibay, Xiomara and Velasco-Mallorquí, Ferran and G. Castaño, Albert and Samitier, Josep and Ramón-Azcón, Javier
Title Composite Biomaterials as Long-Lasting Scaffolds for 3D Bioprinting of Highly Aligned Muscle Tissue
Year 2018
Journal/Proceedings Macromolecular Bioscience
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