Multi-enzyme active temperature-sensitive hydrogel with reactive oxygen species scavenging and antimicrobial capacity for diabetic wound repair

Diabetic wound healing is often impaired due to the high-glucose microenvironment in patients. Among the relevant factors, bacterial infection and overproduction of reactive oxygen species (ROS) have critical roles, and sustained oxidative stress further impairs angiogenesis and increases apoptosis, thereby hindering wound repair. To reduce these effects, we aimed to develop an injectable temperature-sensitive cellulose hydrogel exhibiting anti-apoptotic, oxidative stress-attenuating, antimicrobial, and multi-species enzymatic activities.

By simulating the dual active sites of natural copper–zinc superoxide dismutase (CuZn–SOD), a bimetallic mimetic nanoenzyme [Cu/Zn-metal–organic framework (MOF)] was synthesized. Subsequently, Cu/Zn-MOF was incorporated into a hydroxypropyl methylcellulose hydrogel, and the gelation temperature was adjusted to enable a sol-to-gel transition near physiological temperature. A rheometer was used to measure the gelation temperature, and scanning electron microscopy was performed to characterize the surface morphology. The hydrogels were evaluated for multiple enzyme-like activities, including those of SOD, glutathione peroxidase (GPx), thiol peroxidase (TPx), and ascorbate peroxidase (APx). Mouse fibroblasts (L929 cells) and human umbilical vein endothelial cells were used to assess antioxidant, pro-migratory, pro-angiogenic, and anti-apoptotic properties. Antimicrobial activity was assessed against Escherichia coli and Staphylococcus aureus. Western blotting was performed to verify potential anti-inflammatory mechanisms. Finally, wound and infected-wound models were established in diabetic mice to evaluate the hydrogel’s effects on wound repair.

The hydrogel exhibited a sol-to-gel transition at 37℃ and demonstrated favorable injectability and hydrophilicity, providing a moist healing environment. The Cu/Zn-MOF nanoenzymes demonstrated four enzyme-like activities (SOD, GPx, TPx, and APx), enabling cascade ROS scavenging, which was further confirmed in cellular experiments. The Cu/Zn-MOF nanoenzymes also modulated Sirt1/nuclear factor-κ beta expression to influence inflammatory factor release, thereby exhibiting strong anti-inflammatory activity. The hydrogel also exerted cell migration, angiogenesis, and anti-apoptotic effects. Antimicrobial assays showed kill rates of 99.39% and 99.67% against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively. In a diabetic mouse wound model, the hydrogel significantly enhanced pro-healing effects by promoting neovascularization and collagen deposition through ROS and bacterial clearance, thereby reducing the inflammatory response.

Biomimetic nanoenzymes were synthesized and incorporated into temperature-sensitive injectable hydrogels, which exhibited strong antioxidant and antimicrobial activities that have considerable potential for diabetic wound therapy.