A CuS@g-C₃N₄ heterojunction endows scaffold with synergetic antibacterial effect

Graphitic carbon nitride (g-C₃N₄) had aroused tremendous attention in photodynamic antibacterial therapy due to its excellent energy band structure and appealing optical performance. Nevertheless, the superfast electron-hole recombination and dense biofilm formation abated its photodynamic antibacterial effect. To this end, a nanoheterojunction was synthesized via in-situ growing copper sulfide (CuS) on g-C₃N₄ (CuS@g-C₃N₄). On the one hand, CuS could form Fermi level difference with g-C₃N₄ to accelerate carrier transfer and thus facilitate electron-hole separation. On the other hand, CuS could respond near-infrared light to generate localized thermal to disrupt biofilm. Then the CuS@g-C₃N₄ nanoparticle was introduced into the poly-l-lactide (PLLA) scaffold. The photoelectrochemistry results demonstrated that the electron-hole separation efficiency was apparently enhanced and thereby brought an approximate sevenfold increase in reactive oxygen species (ROS) production. The thermal imaging indicated that the scaffold possesses a superior photothermal effect, which effectively eradicated the biofilm by disrupting its extracellular DNA and thereby facilitated to the entry of ROS. The entered ROS could effectively kill the bacteria by causing protein, K⁺, and nucleic acid leakage and glutathione consumption. As a consequence, the scaffold displayed an antibacterial rate of 97.2% and 98.5% against E. coli and S. aureus, respectively.