Construction and curcumin release performance of pH-responsive hydrogels based on norbornene dicarboxylic anhydride-modified chitosan via thiol–ene photocrosslinking

This study aims to develop a novel chitosan-based pH-responsive hydrogel for sustained curcumin (Cur) delivery. Chitosan was modified with norbornene dicarboxylic anhydride to introduce reactive double bonds and enhance solubility, while cysteine-modified Pluronic F127 was crosslinked via UV-induced thiol–ene chemistry to form a stable three-dimensional network. The hydrogel structure was tuned by adjusting the CSNB/CPC ratio and characterized using 1 H NMR, solid-state 13 C NMR, FTIR, TGA, XRD, SEM, and rheology. The optimized hydrogel achieved a drug loading capacity of 13.3 mg/g and exhibited pH-responsive release in simulated gastrointestinal fluids, with kinetics well-fitted to the Peppas–Sahlin model (R 2  > 0.98), dominated by Fickian diffusion. Functional evaluation showed that NC4 displayed nearly 90% DPPH radical scavenging efficiency, and its antioxidant potential was further supported by the Folin–Ciocalteu (GAE) assay and the phosphomolybdenum (AAE) assay, indicating enhanced overall reducing capacity and total antioxidant capacity. NC4 also exhibited strong antibacterial activity against Staphylococcus aureus and Escherichia coli . Biocompatibility was confirmed by CCK-8 and hemolysis assays, with cell viability exceeding 90% and hemolysis rates below 0.35%. Collectively, this multifunctional hydrogel integrates sustained release, antioxidant, antibacterial, and excellent biocompatibility, providing a promising material platform for oral controlled drug delivery and wound healing applications.