3D Bioprinting of Strong Living Scaffolds

The regeneration of damaged or diseased tissues that serve biomechanical functions, such as musculoskeletal tissues, has been a long-standing challenge in clinical practice and research. Regenerative engineering offers a promising alternative to auto- and allografts in tissue regeneration by combining biomaterial scaffolds, viable cells, and bioactive factors. Engineering scaffolds that provide both mechanical support and biological activities is critical for regenerating such tissues with biomechanical functions; however, it remains an enormous challenge. Currently existing scaffolds, which include either rigid polymer/elastomer with limited bioactivities or hydrogels with poor mechanical properties, fall short of meeting both mechanical and biological needs. We propose to develop a novel family of emulsion bioinks to enable the 3D bioprinting of strong living scaffolds with built-in mechanical robustness and desirable biological functions for tissue regeneration. The encapsulation of bioactive factors and cells within scaffolds presents an attractive strategy to equip the scaffolds with desired biological functions. The major roadblocks to achieve the viable encapsulation of bioactive factors and cells within rigid polymer or elastomer inks include the deficiency of cell adhesive motifs and the frequent usage of harmful chemicals, such as organic solvents and/or toxic reactants. In this study, the water-in-oil emulsion bioink is designed to contain two immiscible phases of hydrogel microparticle (microgel) with entrapped bioactive factors/cells as inner aqueous phase and polymer/elastomer solution as outer organic phase. It is hypothesized that the inner phase of microgels will protect the encapsulated bioactive factors and cells from harmful chemicals in outer phase of polymer/elastomer solution by limiting their diffusion from outer to inner phases. The preliminary data demonstrates that >95% viability of fibroblast cells in a polymer ink is achieved using water-in-oil emulsion system. This project will initiate with the development of cytocompatible and bioprintable cell-laden emulsion bioinks, followed by characterization of 3D-bioprinted strong living scaffolds, and finally validate the functions of encapsulated bioactive factors and stem cells within 3D-bioprinted scaffolds for meniscus regeneration as a test model. This model will include assessments of proliferation, fibrochondrogenic differentiation in vitro and neo-menisci formation in vivo. Overall, our approach presents a paradigm-shifting new method to produce mechanically strong and biologically functional living scaffolds by integrating emulsion chemistry and 3D bioprinting technology. We anticipate that this work will have a broad and significant impact on regenerative engineering by benefiting repair or regeneration of broad-spectrum tissues with biomechanical functions.