Synthesis and characterization of N-octanoyl glycol chitosan as a novel temperature and pH-sensitive injectable hydrogel for biomedical applications

• One-step facile reaction to synthesize N -octanoyl glycol chitosan (OGC) • Controllable sol–gel transition by degree of octanoylation, concentration, and pH. • OGC is biocompatible and non-cytotoxic based on in vitro and in vivo results. • OGC-coated dish is suitable for 3D non-scaffold cell culture. Multi-responsive hydrogel formulations have received significant attention in biomedical applications as promising injectable depots and platforms for tissue regeneration. In this study, a new pH- and temperature-sensitive polymer, octanoyl glycol chitosan (OGC), synthesized by controlled N -octanoylation of glycol chitosan and evaluated as a reversible hydrogel system capable of undergoing sol–gel transition in response to changes in pH and temperature. The OGC hydrogels, with varying degrees of octanoylation (DO), were characterized by 1 H NMR and ATR-FTIR analyses, and their physicochemical properties were evaluated in terms of injectability, thermo- and pH-sensitivity, biodegradability, self-healing, cytotoxicity, 3D cell culture support, and in vivo biocompatibility. The OGC exhibited controlled thermosensitive sol–gel transition behavior, with transition temperature ranging from 23 °C to 58 °C, which could be tuned by adjusting the DO and polymer concentration. The effect of pH on gelation was also observed within the pH range of 5 to 7.4. OGC demonstrated excellent injectability and self-healing properties. In scaffold-free 3D cell culture systems, the OGC supported spheroid formation and maintained stability for up to 7 days. In vivo studies in ICR mice revealed no significant inflammatory response upon implantation. These results suggest that the OGC could be a promising injectable biomaterial for various biomedical applications.