Morphology-dependent Fe3O4 nanozymes with NIR-enhanced peroxidase-like activity for antibacterial wound therapy

Bacterial infection severely impairs wound repair, and antibiotic-based treatment is increasingly challenged by antimicrobial resistance. Herein, Fe3O4 nanozymes with octahedral, spherical, and cubic morphologies were synthesized and systematically compared for peroxidase-like activity, photothermal performance, and antibacterial efficacy. Despite their comparable sizes and good dispersibility, the three nanozymes exhibited distinct morphology-dependent catalytic activities. Octahedral Fe3O4 nanoparticles (O-IONP) showed the highest POD-like activity, strongest hydroxyl radical generation, lowest apparent Michaelis constant toward TMB, and highest maximum reaction velocity. The catalytic activity of Fe3O4 nanozymes increased with temperature and reached an optimum near 55 oC, indicating the feasibility of photothermalenhanced catalysis. Under 808 nm near-infrared irradiation, O-IONP displayed the most efficient photothermal response and reached a temperature favourable for POD-like catalysis. In vitro, O-IONP combined with NIR reduced Escherichia coli viability to approximately 2% and caused severe bacterial membrane deformation, collapse, and rupture, while maintaining acceptable cytocompatibility toward macrophages. In an E. coli-infected wound model, O-IONP with NIR significantly accelerated wound closure, reducing the wound remaining ratio to approximately 13% on day 10. This work demonstrates a simple morphology-engineered Fe3O4 nanozyme platform for photothermal-catalytic antibacterial therapy and infected wound healing.