An NIR-absorbed cationic photosensitizer for high-efficacy eradication of drug-resistance bacteria

With the widespread use of antibiotics, the emergence and spread of drug-resistant bacteria have become a major threat in the global public health field. Small-molecule photodynamic antimicrobial therapy has shown great potential in the treatment of drug-resistant bacteria due to its unique mechanism of action, but small-molecule photosensitizers with near-infrared absorption, which have higher tissue penetration, are still rarely reported. In this study, a cationic small-molecule photosensitizer coumarin-flavylium (CF) with near-infrared absorption was developed, which exhibits excellent anti-drug-resistant bacteria performance. The structure of CF was characterized by ultraviolet-visible absorption spectroscopy, fluorescence emission spectroscopy, etc. The antibacterial effect of CF against methicillin-resistant Staphylococcus aureus (MRSA) was evaluated by the plate coating method, and the antibacterial effect of CF against MRSA was also assessed by experiments such as scanning electron microscopy and LIVE/DEAD^TM staining. The experimental results show that CF has low cytotoxicity, and under the conditions of near-infrared light irradiation (660 nm), low dose (0.5 μmol·L^-1) and low light intensity (20 mW·cm^-2), it exhibits significant antibacterial effect (sterilization efficiency > 99%) and can effectively remove biofilms. This photosensitizer is expected to become a powerful tool to deal with drug-resistant bacterial infections.