A water-soluble, long-wavelength fluorescent-emitting CDs with antibacterial properties derived from the Chinese herbal medicine emodin

It is urgent to develop safe and effective new antibiotics to reduce the increasingly serious threat of antibiotic resistance to human health. This study proposes a novel strategy for synthesizing antibacterial CDs (CDs) using active components from Chinese herbal medicine. Employing medicinal emodin as the carbon source and urea as the nitrogen source, a hydrothermal method was utilized to prepare water-soluble nitrogen-doped CDs (EUCDs). Under 523 nm excitation, its emission wavelength reached 600 nm with a fluorescence lifetime of 1.79 ns. Results demonstrate that EUCDs exhibit s not only superior environmental stability and biocompatibility but also effectively kills Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ). The minimum inhibitory concentration (MIC) of EUCDs was determined to be 14 μg/mL. Research has revealed that EUCDs exhibit distinct red fluorescence on the membranes of L929 tumor cells. Through transmission electron microscopy combined with cell staining and imaging techniques, the antibacterial mechanism of EUCDs is identified as disrupting bacterial cell membranes, leading to the leakage of intracellular substances and effectively killing E. coli and S. aureus . This study successfully developed a carbon dot based high-efficiency antibacterial agent that also has imaging function. This is of great significance for expanding the research and application fields of traditional Chinese medicine and CDs.