Cellulose Acetate Nanoparticles as Eco-Friendly Photosensitizers for Antimicrobial Photodynamic Inactivation

Antimicrobial resistance has emerged as a critical global health issue, demanding sustainable alternatives to conventional antibiotics. This study aimed to develop and evaluate cellulose acetate nanoparticles (NPs-CA) as eco-friendly photosensitizers for antimicrobial photodynamic inactivation (aPDI). NPs-CA were synthesized via nanoprecipitation, producing spherical and monodisperse nanoparticles with a mean hydrodynamic diameter of 268 ± 8 nm. The particles' photophysical and morphological properties were characterized by UV-vis, SEM, and DLS. ROS generation was assessed using dihydroethidium (DHE) assays. Acute toxicity was assessed using Artemia sp. assays. The nanoparticles exhibited visible light absorption at 450 nm and generated ROS upon irradiation. In vitro assays demonstrated a >3 log₁₀ CFU reduction of Escherichia coli at 500 ppm and complete photoinactivation at 1000 ppm under blue-light irradiation. Staphylococcus aureus exhibited low sensitivity, with no significant photodynamic effect observed. Toxicity tests indicated an LC₅₀ of 320.56 ppm and a TU < 0.4, classifying the system as nontoxic. NPs-CA are light-activated photosensitizers for E. coli inactivation, with confirmed safety in ecotoxicological assays. These findings support the use of cellulose-based nanomaterials as sustainable and biocompatible platforms for antimicrobial photodynamic therapy, particularly against multidrug-resistant Gram-negative bacteria.