Light-Activated Antimicrobial Coatings Based on Porphyrin-Functionalized Poly(vinyl chloride) Synthesized via MADIX

Bacterial surface contamination is a significant public health concern, particularly for immunocompromised individuals, and has driven the development of self-sanitizing materials. Photodynamic inactivation (PDI)has emerged as a sustainable antimicrobial strategy that uses photosensitizers (PS) upon light activation. In this study, a porphyrin-functionalized xanthate was synthesized and used as a chain transfer agent in the MADIX polymerization of poly(vinyl chloride) (PVC) under environmentally friendly conditions. PVCs functionalized with porphyrin and having varied molecular weights were fully characterized by MALDI-TOF-MS, 1H NMR, SEC, DSC, and TGA to determine their composition, molecular weight, dispersity (Đ), and thermal properties. The obtained polymers were applied as antimicrobial coatings on glass substrates pretreated with a PVC-co-poly(butyl acrylate) (PBA) film-forming layer, and their surface morphology was analyzed by SEM. The antimicrobial performance against representative Gram-positive and Gram-negative strains, Staphylococcus aureus and Escherichia coli, respectively, was assessed under three conditions: dark, blue light (BL), and white light (WL). BL exposure produced the most pronounced cellular effects, resulting in a significant reduction in bacterial viability. These effects were further confirmed by SEM analysis, which showed visible structural damage to the bacterial cells. Cytocompatibility was confirmed using normal human dermal fibroblast (NHDF) cells. The PS polymer coatings (0.09 mg/cm2) demonstrated strong antimicrobial activity under light exposure and low cytotoxicity, highlighting their potential as photoactive antimicrobial surfaces for biomedical and hygiene-sensitive applications.