A self-activating electron transfer antibacterial strategy: Co3O4/TiO2 P–N heterojunctions combined with photothermal therapy

Abstract

Implant-associated infections are significant impediments to successful surgical outcomes, often resulting from persistent bacterial contamination. It has been hypothesized that bacteria can transfer electrons to semiconductors with comparable potential to the biological redox potential (BRP). Building on this concept, we developed an antibiotic-free bactericidal system, Co₃O₄/TiO₂–Ti, capable of achieving real-time and sustainable bactericidal effects. Our study demonstrated that Co₃O₄/TiO₂–Ti, possessing an appropriately set valence band, initiated charge transfer, reactive oxygen species (ROS) production, and membrane damage in adherent Staphylococcus aureus (S. aureus). Notably, in vivo experiments illustrated the remarkable antibacterial activity of Co₃O₄/TiO₂–Ti, while promoting soft-tissue reconstruction and demonstrating excellent cytocompatibility. Transcriptomic analysis further revealed a down-regulation of aerobic respiration-associated genes and an up-regulation of ROS-associated genes in S. aureus in the presence of Co₃O₄/TiO₂–Ti compared to Ti. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and gene set enrichment analysis (GSEA) identified alterations in respiratory metabolism, oxidative phosphorylation, and the synthesis of amino acid in S. aureus cultured on Co₃O₄/TiO₂–Ti. Furthermore, when combined with near-infrared (NIR) irradiation and photothermal therapy (PTT), Co₃O₄/TiO₂–Ti eliminated 95.71% of floating and adherent S. aureus in vitro. The findings suggest that this antibiotic-free strategy holds substantial promise in enhancing implant sterilization capabilities, thereby contributing to the prevention and treatment of bacterial infections through bandgap engineering of implants and NIR irradiation.