Development of Polyelectrolyte Chitosan-gelatin Hydrogels for Skin Bioprinting

Bioprinting is an emerging technology that offers the unique ability to deposit and pattern different cells and matrix materials to fabricate three-dimensional (3-D) tissue constructs. Markedly, bioprinting demonstrated great potential for skin tissue engineering ranging from the development of 3-D skin tissue models to in-situ bioprinting of skin directly over the wound site. Nevertheless, one of the major challenges that impede the progress in this field is the limited choices of printable biomaterials. In this paper, we report the development of printable polyelectrolyte chitosan-gelatin hydrogel for potential applications in tissue engineering of skin. The oppositely charged functional groups from chitosan and gelatin respectively first interacted at a specific pH range to form a polyelectrolyte complex, followed by further pH-dependent crosslinking. The pH-crosslinked polyelectrolyte chitosan-gelatin hydrogel was then evaluated in terms of its rheological behavior, biocompatibility, printability and lastly material stability under physiological conditions. The polyelectrolyte chitosan-gelatin hydrogel remained in a robust gel-state over the temperature range of 20-40 oC and facilitated cellular attachment and proliferation. Furthermore, it demonstrated good printability and the multi-layered hydrogel construct was mechanically stable after subjecting it to physiological conditions for 7 days.