A PEGylated star polymer with a silver-porphyrin core as an efficient photo-antimicrobial agent

Antibacterial agents play a pivotal role in healthcare to prevent contamination of biomedical devices, which can determine infections in surgical and traumatic wound treatments. Furthermore, the COVID-19 pandemic has amplified the importance of protecting common surfaces to avoid bacterial contamination issues. Phenomena such as bacterial resistance push research to develop innovative antibacterial nanosystems. In this context, various agents showing antibacterial properties have appeared, including drug-releasing polymers, organic/inorganic hybrids, and porphyrin derivatives. The silver-based porphyrin derivatives show antibacterial properties despite having some drawbacks, such as toxicity for humans. On the other hand, water-soluble porphyrins, obtained by functionalization of the porphyrin core with PEG chains that enhance solubility and provide stealth properties, have gained attention because of their biocompatibility, structural stability, and tunability. This study focuses on the synthesis and characterization of a PEGylated silver-porphyrin that shows photo-activated antibacterial properties against Pseudomonas aeruginosa and Staphylococcus aureus, antibiotic-resistant pathogens that often coexist and contribute to biofilm-related problems. The porphyrinic system was characterized through NMR, UV–Vis, and fluorescence spectroscopies. Its in-vitro antibacterial activity was investigated and compared with that of the metal-free counterpart. To elucidate the influence of the complexed silver ion and its free base on the photo-antimicrobial effect, the occurrence of demetallation phenomena under irradiation was investigated. The experimental data suggest that the complexation of the silver ion protects the porphyrin core, allowing the photo-bactericidal activity of the system through photo-demetallation phenomena under light irradiation. © 2024 The Authors