Fluorescent Carbon Dot–Curcumin Nanocomposites for Remarkable Antibacterial Activity with Synergistic Photodynamic and Photothermal Abilities

Photosensitizer (PS)-mediated photodynamic therapy (PDT) has attracted more and more attention as an alternative to traditional antibiotic therapy. Nevertheless, the limitations of traditional photosensitizers seriously hinder their practical application, as a result, the methods to improve the antibacterial properties of traditional photosensitizers have become a hot topic in the field of photomedicine. Herein, a compound nano-PS system has been constructed with synergistic photodynamic and photothermal (PTT) antibacterial effects, triggered by a dual-wavelength illumination. Fluorescent carbon dots (CDs) were synthesized and employed as carriers for the delivery of curcumin (Cur) to obtain CDs/Cur. Upon combined near-infrared and 405 nm visible dual-wavelength irradiation, CDs/Cur could simultaneously generate ROS and a moderate temperature increase, triggering synergistic antibacterial effects against both Gram-positive and Gram-negative bacteria. The results of scanning electron microscopy and fluorescence confocal imaging showed that the combined effect of CDs/Cur with PDT and PTT caused more serious damage to the cell membrane. In addition, CDs/Cur exhibited low cytotoxicity and negligible hemolytic activity, showing great biocompatibility. Therefore, the construction of CDs/Cur by employing CDs as photosensitizer delivery carriers provides a strategy for the improvement of the antibacterial effect of the photosensitizer and the design of next-generation antibacterial agents in photomedicine.