Polydopamine-Coated Copper-Doped Co₃O₄ Nanosheets Rich in Oxygen Vacancy on Titanium and Multimodal Synergistic...

Medical titanium-based (Ti-based) implants in the human body are prone to infection by pathogenic bacteria, leading to implantation failure. Constructing antibacterial nanocoatings on Ti-based implants is one of the most effective strategies to solve bacterial contamination. However, single antibacterial function was not sufficient to efficiently kill bacteria, and it is necessary to develop multifunctional antibacterial methods. This study modifies medical Ti foils with Cu-doped Co₃O₄ rich in oxygen vacancies, and improves their biocompatibility by polydopamine (PDA/Cu-O_v-Co₃O₄). Under near-infrared (NIR) irradiation, nanocoatings can generate •OH and ¹O₂ due to Cu⁺ Fenton-like activity and a photodynamic effect of Cu-O_v-Co₃O₄, and the total reactive oxygen species (ROS) content inside bacteria significantly increases, causing oxidative stress of bacteria. Further experiments prove that the photothermal process enhances the bacterial membrane permeability, allowing the invasion of ROS and metal ions, as well as the protein leakage. Moreover, PDA/Cu-O_v-Co₃O₄ can downregulate ATP levels and further reduce bacterial metabolic activity after irradiation. This coating exhibits sterilization ability against both Escherichia coli and Staphylococcus aureus with an antibacterial rate of ca. 100%, significantly higher than that of bare medical Ti foils (ca. 0%). Therefore, multifunctional synergistic antibacterial nanocoating will be a promising strategy for preventing bacterial contamination on medical Ti-based implants.