Nontoxic Carbon Quantum Dots/g-C3N4 for Efficient Photocatalytic Inactivation of Staphylococcus aureus under Visible Light

The widespread use of antibiotics has caused the rapid emergence of antibiotic-resistant bacterial strains and antibiotic resistance genes in the past few decades. Photocatalytic inactivation, a promising approach for the killing of pathogens, efficiently avoids the problems induced by antimicrobial drugs. However, traditional photocatalysts usually have some disadvantages, such as high costs of raw materials, ultraviolet ray excitation, and potential leaching of toxic metals. Here, a metal-free heterojunction photocatalyst, denoted as CQDs/g-C3N4, is synthesized through incorporating carbon quantum dots (CQDs) on graphitic carbon nitride (g-C3N4), which significantly enhances photocatalytic inactivation of Staphylococcus aureus (S. aureus) compared with pure g-C3N4 in vitro. CQDs/g-C3N4 causes a rapid increase of intracellular reactive oxygen species levels and destruction of cell membranes under visible light, eventually leading to death of bacteria. The efficacy of CQDs/g-C3N4 is further examined by a mouse cutaneous infection model of S. aureus. CQDs/g-C3N4 markedly reduces the bacterial loads and prompts lesion recovery in mice, as compared with g-C3N4-treated group. In vivo and in vitro toxicity analyses show that the side effects of CQDs/g-C3N4 are negligible. Considering the efficient photocatalytic inactivation and nontoxicity of CQDs/g-C3N4, this visible-light-driven photocatalyst paves a brand new avenue for the treatment of S. aureus infection.