Regulating the Atomic Active Center by Covalent Organic Framework-Derived Photothermal Nanozyme to Arm Self-Gelling Powder for Bacterial Wound Healing

Creating simple methods to produce antioxidant nanozymes with clear structure–activity relationships, particularly aiming to improve disinfection and create practical drug formulations for bacterial wound healing, remains a crucial challenge. Herein, we synthesized iron-loaded covalent organic framework nanospheres, which were then controllably transformed into a carbon-based nanozyme with both iron single atoms and iron clusters through simple pyrolysis. We discovered that the gradual growth of iron clusters significantly boosted the nanozyme's adsorption onto the substrate and electron transfer, greatly influencing its activity. The nanozyme, optimized by the coexistence of single iron atoms and Fe4 clusters, exhibited the strongest catalase and superoxide dismutase enzyme activities as well as high photothermal efficiency. Under physiological conditions, its peroxidase and oxidase enzymatic activities, which stimulate oxidative stress, remained low. Furthermore, we created an antibacterial self-gelling powder capable of dispersing the nanozyme using polyacrylamide and poly(acrylic acid). The powder can rapidly gel and adhere to wet wound areas, synergistically sterilizing the wound through the combined actions of the gel's amino groups and the nanozyme's photothermal effect, while leveraging the antioxidant enzymatic effects to mitigate wound inflammation. These properties contribute to the fast healing of infectious wounds, thus promising a clear formulation and treatment.