Light Meets Nature: Cellulose Cluster as a Natural Photoantimicrobial Agent

Antibiotic‐resistant bacteria present a persistent challenge to current therapeutic methods, underscoring the need for novel antimicrobial approaches. Antimicrobial photodynamic therapy (aPDT) is a promising approach that uses reactive oxygen species to damage bacterial membranes, proteins and nucleic acids, making it difficult for bacteria to become resistant. Nevertheless, the practical application of many photosensitizers is hindered by limited biocompatibility and aggregation‐caused quenching effects that reduce photodynamic efficiency. Building on recent advances in cluster‐triggered emission (CTE), this study demonstrates that cellulose derivatives can exhibit pronounced CTE behavior, generating singlet oxygen in suspension through long‐lived excitonic states. The results also underscore the strong photoantimicrobial activity of these materials against Gram‐positive bacteria like Staphylococcus aureus , highlighting their potential as an unconventional class of photodynamic agents composed of FDA‐approved materials. These findings redefine the role of cellulose, shifting it from a passive formulation excipient into an active material with previously unrecognized photodynamic capabilities.