Abstract: Objective: To investigate the photothermal/photocatalytic synergistic antimicrobial effect of monatomic Cu-doped graphitic carbon nitride (g-C₃N₄) combined with bismuth sulfide (Bi₂S₃) composites against porphyromonas gingivalis (P.g) in periodontitis. Methods: g-C₃N₄ (abbreviated as CN) nanosheets and Bi₂S₃ (abbreviated as BiS) were synthesized by hydrothermal method, CN was grafted to Cu²⁺ to obtain CuCN and the composite material CuCN@BiS was synthesized based on electrostatic adsorption method. Nanomaterials was characterized in terms of morphology, potential, and crystal structure. Composites were tested for reactive oxygen species production in vitro using 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) fluorescence. The 808 nm near infrared (NIR) light exciter were used to evaluate the photothermal properties of CuCN@BiS. The antimicrobial efficiency of the composite CuCN@BiS against P.g by colony counting and the removal of biofilm were assessed by crystal violet staining. The biocompatibility of CuCN@BiS was observed using the cell counting kit-8 (CCK-8) experiment. Results: The composite CuCN@BiS was successfully constructed and had good photothermal properties under NIR light irradiation. The antimicrobial effect on P.g and the scavenging effect on biofilm of CuCN@BiS were concentration-dependent. When the concentration was 0.5 mg/mL, CuCN@BiS demonstrated excellent antimicrobial (98.36%) and anti-biofilm efficiency (92.84%). Meanwhile, under NIR irradiation, the amount of ROS entering the bacteria was positively correlated with the concentration of CuCN@BiS. The relative activity of the cells in 0.5 mg/mL of CuCN@BiS was above 85%, which demonstrated good biocompatibility. Conclusion: Application of CuCN@BiS for photocatalytic/photothermal antimicrobial treatment could effectively destroy P.g and its biofilm, providing references for the treatment of periodontitis.

Key words: nanocomposites, photocatalytic therapy, photothermal therapy, Porphyromonas gingivalis