Insights into rapid photodynamic inactivation mechanism of Staphylococcus aureus via rational design of multifunctional nitrogen-rich carbon-coated bismuth/cobalt nanoparticles

Despite the development of various drugs and materials, bacterial infections remain a serious problem for wound healing. Most current materials cannot simultaneously provide antibacterial effects, reusability, and biocompatibility, and participate in stimulating cellular behaviour to promote bacterial wound healing. Herein, multifunctional nitrogen-rich carbon-coated bismuth/cobalt nanoparticles (Bi@Co@CN) with foam-like structures synthesised by a simple two-step method showed remarkably improved magnetic and photoconversion effects. These are promising candidates as photodynamic inactivation materials. Within 20 min, > 99.999% Staphylococcus aureus (S. aureus) were killed by the composite due to its strong ability to generate reactive oxygen species (ROS) and thermal energy under simulated visible light. Additionally, Bi@Co@CN also displayed high stability: its antibacterial efficiency underwent rapid photodynamic inactivation over five cycles. In vitro results revealed that ROS and photothermal conversion of materials can seriously damage bacterial cell membranes and inhibit the virulence factors produced by bacteria, which ultimately leads to the death of S. aureus. Moreover, in vivo assessment of wound healing showed that the material was very effective for bacteria-accompanied wound healing and did not cause detectable damage to the major organs. Therefore, the Bi@Co@CN composite has great potential as a safe multimodal treatment system for active photodynamic inactivation and wound healing.