Development of chitinous nanofiber-based flexible composite hydrogels capable of cell adhesion and detachment

Chitinous nanofibers (NFs) exhibit a specific physiological activity not observed in the powdered form. While three-dimensional cell culture scaffolds are being actively studied, attempts have been made to use chitinous materials as well. In this study, we aimed to develop a cell-adhesive chitinous NF-based flexible hydrogel. Such a gel will be easy to handle, and there is a possibility that the gel will be able to be three-dimensionally molded. For this purpose, the surface of chitinous NFs was modified to introduce vinyl polymerizable functional groups, and the modified NFs were copolymerized with an N-isopropylacrylamide (NIPAM) monomer in an aqueous system. First, by modification of chitosan NFs with maleic anhydride (MA), a flexible gel was obtained by subsequent copolymerization with NIPAM. However, the adhesion of L929 mouse fibroblasts onto MA-modified NFs was extremely lower than that of chitosan NFs, probably due to the simultaneous introduction of anionic groups. The desired cell-adhesive flexible hydrogel was eventually obtained by introducing cationic groups and polymerizable functional groups on the chitinous NF surface. Cells adhered to the gel could be detached by cooling to 4 degrees C. The composite hydrogel fabricated here may be useful as a cell culture scaffold material in regenerative medicine.