Antibacterial carboxymethyl chitosan hydrogel loaded with antioxidant cascade enzymatic system for immunoregulating the diabetic wound microenvironment.

Diabetic wound healing faces several complex challenges, such as hypoxia, oxidative stress, and bacterial infections, which severely inhibit the wound-healing process. Herein, a quaternary ammonium salt-crosslinked carboxymethyl chitosan hydrogel (TPC) with excellent antioxidant and antibacterial properties was developed to immunoregulate the diabetic wound microenvironment. The TPC hydrogel was prepared by first mixing carboxymethyl chitosan (CMCS) and protocatechualdehyde (PA), followed by the addition of a quaternary ammonium cross-linker (TSPBA) and a superoxide dismutase (SOD)-catalase (CAT) cascade system. The immobilized SOD and CAT retained their activity, continuously converting endogenous ·O and HO to O and HO. PA also provided the TPC hydrogel excellent oxygen and nitrogen radical scavenging capacity. The quaternary ammonium groups in TSPBA significantly enhanced the inherent antibacterial ability of CMCS-based hydrogels. In diabetic wound-healing experiments, this porous and adhesive TPC hydrogel effectively closed wounds and regenerated skin tissue, resulting in shorter wound edges, thicker granulation, and higher collagen deposition levels compared with other groups. The TPC hydrogel also promoted macrophage polarization toward the M2 phenotype, accelerating wound healing by upregulating IL-10 expression, downregulating IL-6 expression, and enhancing angiogenesis. These results demonstrate the great potential of TPC hydrogel as a promising therapeutic dressing for treating diabetic wounds.