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Biomimetic medical materials are the biomaterials which mimic the important characteristic features of natural material/tissue structures or architectures and are mainly used in biomedical field for their applications in tissue regeneration, medical devices, biosensors and drug delivery. It is one of the leading research topics which have the ability to replace the existing biomaterials and medical devices and to development new biomaterials. The innovation and development in this research area are growing quickly because of the state-of-the-art techniques like nanobiotechnology, biosensors, tissue engineering and regenerative medicine, and 3D (bio)printing. These techniques can mimic the biomacromolecules, peptide sequences, morphology, chemical and physical structures more precisely than other currently available methods. The importance of hydrogels and its composites as examples among many other biomaterials are increasing vastly because of their recent advancements in its biological, chemical and physical cues which are biomimetic to native tissues. Furthermore, an enhancement in the 3D bioprinting technology where live cells are printed along with biomaterials demonstrates the capabilities of this technology to innovate novel tissue engineering products in micro- to macro-technology. The recent trends of development and intellectual properties related to biomimetic medical materials along with their perspectives and area of scope are discussed by focusing on 3D bioprinting in this chapter.

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We developed customizable biomolecule functionalized 3D poly-ε-caprolactone (PCL) scaffolds reinforced with carbon nanofibers (CNF) for human meniscal tissue engineering. 3D nanocomposite scaffolds exhibited commendable mechanical integrity and electrical properties with augmented cytocompatibility. Especially, the functionalized 3D (10wt% CNF) scaffolds showed ~363% increase in compressive moduli compared to the pristine PCL. In dynamic mechanical analysis, these scaffolds achieved highest value (~42 MPa at 10 Hz) among all tested scaffolds including pristine PCL and human menisci (33, 41, 56 years). In vitro results were well supported by the outcomes of cell proliferation analysis, microscopic images, Hoechst staining and extracellular-matrix estimation. Further, in vivo rabbit bio toxicity studies revealed scaffold's non-toxicity and its future potential as a meniscus scaffold. This study also indicates that the incorporation of CNF in polymer matrix may be optimized based on mechanical properties of patient meniscus and it may help in developing the customized patient specific 3D constructs with improved multifunctional properties.

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BACKGROUND: The worldwide demand for the organ replacement or tissue regeneration is increasing steadily. The advancements in tissue engineering and regenerative medicine have made it possible to regenerate such damaged organs or tissues into functional organ or tissue with the help of 3D bioprinting. The main component of the 3D bioprinting is the bioink, which is crucial for the development of functional organs or tissue structures. The bioinks used in 3D printing technology require so many properties which are vital and need to be considered during the selection. Combination of different methods and enhancements in properties are required to develop more successful bioinks for the 3D printing of organs or tissue structures. MAIN BODY: This review consists of the recent state-of-art of polymer-based bioinks used in 3D printing for applications in tissue engineering and regenerative medicine. The subsection projects the basic requirements for the selection of successful bioinks for 3D printing and developing 3D tissues or organ structures using combinations of bioinks such as cells, biomedical polymers and biosignals. Different bioink materials and their properties related to the biocompatibility, printability, mechanical properties, which are recently reported for 3D printing are discussed in detail. CONCLUSION: Many bioinks formulations have been reported from cell-biomaterials based bioinks to cell-based bioinks such as cell aggregates and tissue spheroids for tissue engineering and regenerative medicine applications. Interestingly, more tunable bioinks, which are biocompatible for live cells, printable and mechanically stable after printing are emerging with the help of functional polymeric biomaterials, their modifications and blending of cells and hydrogels. These approaches show the immense potential of these bioinks to produce more complex tissue/organ structures using 3D bioprinting in the future.

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Tissue engineered constructs with rapid restoration of mechanical and biological properties remain a challenge, emphasizing the need to develop novel scaffolds. Here, we present a multicomponent composite three-dimensional scaffold structure with biomimetic reinforcement and biomolecule functionalization for meniscus tissue engineering. The scaffold structure was developed using 3:1 silk fibroin (SF) and polyvinyl alcohol (PVA). Autoclaved eggshell membrane (AESM) powder (1-3%w/v) was used as reinforcement to enhance biomechanical properties. Further to improve cell attachment and proliferation, these scaffolds were functionalized using an optimized unique combination of biomolecules. Comprehensive analysis of scaffolds was carried out on morphological, structural, mechanical and biological functionalities. Their mechanical properties were compared with different native human menisci. The results indicated that, functionalized SF-PVA with 3%AESM has shown similar order of magnitude of compressive and dynamic mechanical properties as in human meniscus. Moreover, 3% AESM based scaffolds were found to support better primary human meniscal cellular proliferation and extracellular matrix secretion. Immunohistochemical analysis revealed angiogenesis and biocompatibility with minimal inflammatory response for subcutaneously implanted scaffolds in New Zealand white rabbits. The developed reinforced and functionalized SF-PVA scaffolds can uniquely combine the potential for load-bearing properties with improved in vitro and in vivo support for meniscus tissue regeneration. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1722-1731, 2018.

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BACKGROUND: The tissue engineering and regenerative medicine approach require biomaterials which are biocompatible, easily reproducible in less time, biodegradable and should be able to generate complex three-dimensional (3D) structures to mimic the native tissue structures. Click chemistry offers the much-needed multifunctional hydrogel materials which are interesting biomaterials for the tissue engineering and bioprinting inks applications owing to their excellent ability to form hydrogels with printability instantly and to retain the live cells in their 3D network without losing the mechanical integrity even under swollen state. METHODS: In this review, we present the recent developments of in situ hydrogel in the field of click chemistry reported for the tissue engineering and 3D bioinks applications, by mainly covering the diverse types of click chemistry methods such as Diels-Alder reaction, strain-promoted azide-alkyne cycloaddition reactions, thiol-ene reactions, oxime reactions and other interrelated reactions, excluding enzyme-based reactions. RESULTS: The click chemistry-based hydrogels are formed spontaneously on mixing of reactive compounds and can encapsulate live cells with high viability for a long time. The recent works reported by combining the advantages of click chemistry and 3D bioprinting technology have shown to produce 3D tissue constructs with high resolution using biocompatible hydrogels as bioinks and in situ injectable forms. CONCLUSION: Interestingly, the emergence of click chemistry reactions in bioink synthesis for 3D bioprinting have shown the massive potential of these reaction methods in creating 3D tissue constructs. However, the limitations and challenges involved in the click chemistry reactions should be analyzed and bettered to be applied to tissue engineering and 3D bioinks. The future scope of these materials is promising, including their applications in in situ 3D bioprinting for tissue or organ regeneration.

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In the current study, we describe the synthesis, material characteristics, and cytocompatibility of conducting poly (ɛ-caprolactone) (PCL)-based nano-composite films. Electrically conducting carbon nano-fillers (carbon nano-fiber (CNF), nano-graphite (NG), and liquid exfoliated graphite (G)) were used to prepare porous film type scaffolds using modified solvent casting methods. The electrical conductivity of the nano-composite films was increased when carbon nano-fillers were incorporated in the PCL matrix. CNF-based nano-composite films showed the highest increase in electrical conductivity. The presence of an ionic solution significantly improved the conductivity of some of the polymers, however at least 24 h was required to absorb the simulated ion solutions. CNF-based nano-composite films were found to have good thermo-mechanical properties compared to other conducting polymer films due to better dispersion and alignment in the critical direction. Increased nano-filler content increased the crystallisation temperature. Analysis of cell viability revealed no increase in cell death on any of the polymers compared to tissue culture plastic controls, or compared to PCL polymer without nano-composites. The scaffolds showed some variation when tested for PC12 cell attachment and proliferation, however all the polymers supported PC12 attachment and differentiation in the absence of cell adhesion molecules. In general, CNF-based nano-composite films with highest electrical conductivity and moderate roughness showed highest cell attachment and proliferation. These polymers are promising candidates for use in neural applications in the area of bionics and tissue engineering due to their unique properties.

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