Antimicrobial activity and mechanisms of carbon quantum dot decorated modified zinc oxide nanoparticles against oral pathogenic bacteria

Caries represents one of the most prevalent bacterial infectious diseases in the oral cavity. Over decades, researchers have been actively seeking nanomaterials capable of inhibiting oral pathogenic bacteria. We utilized a one-pot hydrothermal method to synthesize CQDs with multicolor luminescence and CQD-loaded ZnO composite nanomaterials. FE-SEM revealed that the rod-like structure of CQDs/ZnO becomes finer with increased CQDs content. XRD and XPS confirmed the presence of all components within the nanocomposites. We compared the antimicrobial activities of ZnO, 7.7% and 14.3% CQDs/ZnO against Streptococcus mutans, Enterococcus faecalis, Escherichia coli, and Staphylococcus aureus. The 7.7% CQDs/ZnO composite exhibited the most effective antibacterial activity. The 7.7% CQDs/ZnO composite exhibited the most effective antibacterial activity. FE-SEM and ONPG assays demonstrated that 7.7% CQDs/ZnO disrupted the membrane structure and alters membrane permeability. ESR, DPBF and ROS assayed further confirmed that 1O2 produced by 7.7% CQDs/ZnO accumulated at the cell membrane and disrupts its structure.