Green synthesis of carbon quantum dots from plant turmeric holds promise as novel photosensitizer for in vitro photodynamic antimicrobial activity

Research has shown that carbon quantum dots (CQDs) are active as novel carbon nanomaterials in photodynamic therapy due to their excellent photophysical properties. However, previously expensive precursors and time-consuming production processes, as well as complex doping/functionalization forms have limited their economic design and use. In this study, we prepared ST-JHCQDs by a simple and green method using natural plant turmeric as the carbon source, and characterized ST-JHCQDs by physical and optical means. In vitro antibacterial results showed that the antibacterial effects of ST-JHCQDs against E. coli and S. aureus under the irradiation of blue light depended on carbonization degrees, concentration and light duration. Biomolecule leakage and confocal laser scanning microscope analysis showed that ST-JHCQDs were effective in producing reactive oxygen species (ROS) under blue light irradiation, which resulted in disturbance of cell membrane integrity and leakage of intracellular macromolecules in both bacteria. Meanwhile, scanning electron microscopy images showed cell membrane wrinkling and fragmentation, which was consistent with ROS damage, demonstrating the effectiveness of ST-JHCQDs as photosensitizers in vitro photodynamic antimicrobial activity. These experiments show that CQDs prepared from turmeric was a new natural photosensitizer material with great antibacterial potential.