A multifunctional carbon dot-based nanoplatform for bioimaging and quaternary ammonium salt/photothermal synergistic antibacterial therapy.

The emergence of drug resistance and superbugs poses a devastating threat to public health and can even lead to death. Thus, it is significant to develop a novel antibacterial agent to combat bacterial infections. Herein, we developed quaternary ammonium salt (QAS) modified near-infrared carbon dots (RCDs-C35), which possesses synergistic antibacterial performance under 808 nm irradiation. This nanocomposite exhibits excellent photothermal performance and the photothermal conversion efficiency (PCE) could reach 35%. Generally speaking, the bacterial membrane sensitivity to hyperthermia would be enhanced after QAS caused the initial damage, and thus it can more easily cause bacterial inactivation after irradiation. In vitro and in vivo experiments indicated that the RCDs-C35 exhibit excellent biocompatibility, predominant synergistic antibacterial performance, and the capability of promoting wound healing. The antibacterial ratio against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) could reach 99.5% and 99.8%, respectively, after 808 nm irradiation. Additionally, the cellular imaging indicated that the RCDs-C35 could be used as a fluorescent probe in bioimaging. Therefore, RCDs-C35 with synergistic antibacterial performance and inherent luminescence possess great potential for application in the biomedical field.