Carbon Quantum Dots as Drug Carriers of Methylene Blue: Preparation and Properties Study.

Photodynamic therapy (PDT) has long been considered an effective way to tackle antibiotic resistance. Here, Methylene blue (MB) as photosensitizer was combined with carbon quantum dots (CQDs) as drug carriers to make a compound antibacterial agent. The fluorescent CQDs were prepared by hydrothermal method with citric acid (CA) and neutral red (NR) as raw materials. The CQDs can emit 640nm red fluorescence under 520nm laser irradiation. In the antibacterial experiment, CQDs-MB was irradiated with 660nm light. The results showed that CQDs-MB had ideal antibacterial activity against <italic>Staphylococcus aureus</italic> (<italic>S. aureus</italic>) and <italic>Escherichia coli</italic> (<italic>E. coli</italic>) with 100% antibacterial concentration of 5μM and 10μM, respectively. The combination of CQDs and MB enhanced singlet oxygen (1O2) generation and the PDT activity of MB, which significantly increased the phototoxicity of MB to bacteria. [ABSTRACT FROM AUTHOR]