In vitro and in vivo acute response towards injectable thermosensitive chitosan/TEMPO-oxidized cellulose nanofiber hydrogel

TEMPO-oxidized cellulose nanofiber (TOCNF) is a natural material with many promising properties, including biocompatibility and degradability. In this study, we integrated TOCNF at different concentrations (0.2, 0.4, 0.6, 0.8% w/v) with chitosan (CS) and created a thermosensitive injectable hydrogel intended for biomedical applications. These hydrogels can undergo sol-gel transition at body temperature through interactions between chitosan and beta-glycerophosphate. The addition of TOCNF resulted in faster gelation time and increased porosity. These hydrogels with TOCNF showed improved biocompatibility both in vitro and in vivo compared to CS hydrogel. Both MC3T3-E1 pre-osteoblast cells and L929 fibroblast cells showed biocompatibility towards CS/TOCNF 0.4. After 7 days of implantation, initial inflammatory response to CS/TOCNF 0.4 was found. Such response was significantly subsided within 14 days. Cell infiltration within the hydrogel was also prominent, showing anti-inflammatory or wound healing (M2) macrophage at 14 days after implantation. These results showed that the addition of TOCNF could significantly improve the biocompatibility of CS hydrogel as a biomaterial for biomedical application.