Enzyme-Induced Photothermal and Thermally Shape-Adaptive Gelatin–Gallic Acid Hydrogel for Infected Skin Wound Management

Effective coverage and antibacterial treatment of irregular wounds remain challenging due to complex geometries, bacterial growth, and elevated levels of reactive oxygen species, which cause prolonged inflammation and impaired healing. In this study, a gelatin-gallic acid (GGA) hydrogel was enzymatically cross-linked using horseradish peroxidase (HRP) and hydrogen peroxide (H₂O₂). At high concentrations (10 wt % GGA and 0.04 wt % H₂O₂), the oxidized gallic acid moieties formed oligomeric structures with intrinsic photothermal activity, eliminating the need for exogenous photothermal agents. The hydrogel further exhibited thermosensitive behavior, maintaining an elastic state at skin temperatures but transitioning to a viscous, reflowable state above 43.6 °C. Within the photothermal therapeutic range (40-50 °C), the hydrogel undergoes reversible deformation, enabling shape readaptation and effective coverage of irregular wound surfaces under near-infrared irradiation. This system achieves synergistic photothermal antibacterial efficacy, thermal shape adaptivity, antioxidant performance, and inflammation mitigation, leading to enhanced healing outcomes.