White light-triggered zwitterionic polymer nanoparticles based on an AIE-active photosensitizer for photodynamic antimicrobial therapy

Photodynamic antimicrobial therapy (PDAT) has received enormous attention due to its excellent spatiotemporal accuracy, non-invasiveness, and anti-multidrug resistance properties compared with chemotherapy. However, traditional PDAT methods possess numerous disadvantages, such as high dark toxicity, poor chemical stability, susceptibility to fluorescence quenching, and relatively low ROS efficiency in water. In this work, we successfully fabricated a type of pH-responsive zwitterionic polyurethane nano-micelle possessing great reactive oxygen species (ROS) generation efficiency due to the smaller singlet-triplet energy gap of its AIE PS moiety. This nano-system also has near-infrared bioimaging functionality, and can detect bacteria in real time. In addition, the hydrophilic zwitterionic polyurethanes plays a vital role in antifouling, enhancing biocompatibility and prolonging circulation time under normal conditions (pH 7.4). Under acidic conditions (pH 5.4), the zwitterionic moiety is suddenly protonated to enable positively charged nano-micelles to target the bacterial infection site, resulting in great antibacterial efficiency, which is superior to the existing PDAT method.