The emergence of antibiotic drug resistance has undermined the efficacy of antibiotics, and is becoming a severe threat to public health. To combat antibiotic drug resistance and to replace traditional antibiotic treatment, an alternative strategy based on antibacterial photodynamic therapy (APDT), which has broad applicability, high efficiency and less potential of developing antibiotic drug resistance, has been developed. In this work, the cationic porphyrin-based nanoparticles (NPs) were prepared by epoxy-amine chain extension polymerization of diepoxy-terminated poly(ethylene glycol) (PEG) and tetraamino-containing porphyrin, followed by quaternization with methyl iodine and butyl bromide. The as-obtained cationic porphyrin NPs preserved the photophysical properties of porphyrin derivatives, and can efficiently generate singlet oxygen (