To address the current need for engineered tissues and organs, we have developed new hyaluronic acid (HA) and gelatin-based biomaterials for implementation within bioprinting and rotational bioreactor frameworks. By using creative modification, combination, and engineering strategies, we have been able to add novel properties and functionality to these derivatives.Based on the original thiol-functionalized HA hydrogels developed in our laboratory, we have branched out to further modify hydrogels using new chemistries and crosslinkers. Different crosslinkers, such as a 4-armed PEG crosslinker and gold nanoparticles (AuNPs), as well as a methacrylated HA derivatives, alter the gelation characteristics and mechanical properties of the hydrogels, which have been characterized by rheology. These hydrogels have properties that make them more suitable for bioprinting applications, in which the mechanical properties determine ease of material deposition into 3-D physiologically-relevant organizations. Additionally, these materials show good biocompatibility, making them appropriate for cell-loaded printing and tissue culture.We have also modified the surfaces of crosslinked dextran beads with HA and gelatin derivatives, turning them into effective microcarriers that support cell growth in a rotational bioreactor. Cell clusters that were formed using this approach could be removed from the beads and returned to culture to yield bead-free microtissues that could be bioprinted within a hydrogel carrier.The goal of this work is to demonstrate the efficacy of these materials and approaches in bioprinting applications. Tailoring the mechanical properties to the exact specifications necessary for successful printing is difficult, but possible with a logical approach, addressing each of the parameters that affect the end product -- concentrations, polymer to crosslinker ratio, gelation times, and cell densities. Use of hyaluronic acid in medicine has long been established, but by incorporating new modifications and engineering techniques, we can develop biomaterials that address issues ranging from simple cell culture procedures to advanced protocols for developing engineered tissues.
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