Anti-inflammatory and antibacterial hydrogel of chitosan-dimethyl itaconate conjugate

Hydrogels with anti-inflammatory and antibacterial capacity have gained increasing attention in regenerative medicine. Dimethyl itaconate (DMI), a derivative of itaconic acid, exhibits powerful anti-inflammatory activity. Herein, we report a green synthesis of a chitosan-dimethyl itaconate (CS-DMI) conjugate through a nucleophilic substitution reaction, where primary amines of chitosan attack the ester carbonyl groups of DMI to form conjugation under mild alkaline conditions. The resulting conjugate was subsequently crosslinked with genipin into a hydrogel. Our findings indicate that this reaction fundamentally changed the nature of CS, converting it from acidic aqueous solution into a nearly neutral aqueous CS-DMI solution. It improved the efficiency of genipin crosslinking while maintaining the robust antibacterial activity of CS. The CS-DMI hydrogel showed sustained drug release of DMI and greater compression strength over the CS hydrogel. The CS-DMI conjugate showed good cytocompatibility, significantly promoted macrophage polarization toward an M2-like phenotype, reducing reactive oxygen species and nitric oxide production in lipopolysaccharide-stimulated macrophages. In a murine subcutaneous implantation model, the CS-DMI hydrogel significantly reduced immune cell infiltration, primarily by suppressing neutrophil recruitment and promoting a shift in macrophage polarization toward the pro-healing M2 phenotype. These findings confirm a viable strategy for developing multifunctional hydrogels that simultaneously address anti-inflammatory and antibacterial needs for modulating inflammation in regenerative medicine.