Rose Bengal-functionalized chitosan spheres as singlet oxygen generators for photodegradation of water contaminants and photodynamic inactivation.

Millimeter-sized chitosan spheres covalently functionalized with Rose Bengal (ME-CS-RB) were developed as reusable heterogeneous photosensitizers capable of generating singlet oxygen (1O2) under visible-light irradiation. Structural and spectroscopic characterization confirmed the effective immobilization of the photosensitizer within the chitosan matrix without compromising its integrity. The photoactivity of ME-CS-RB was evaluated through the photosensitized degradation of furosemide as a model water contaminant under green LED irradiation, with scavenger experiments indicating that 1O2 is the predominant reactive oxygen species involved, consistent with a Type II photosensitization mechanism. The spheres exhibited good operational stability over successive reuse cycles. In parallel, the photodynamic potential of the system was demonstrated through the effective inactivation of both Gram-positive (Enterococcus faecalis) and Gram-negative (Escherichia coli) bacteria under visible-light irradiation. The environmental relevance of the process was further assessed using phytotoxicity assays, which confirmed the neutralization of furosemide toxicity after photodegradation. Overall, these results demonstrate that ME-CS-RB spheres constitute a versatile photoactive platform integrating pollutant degradation and photodynamic inactivation, relevant to photochemical and photobiological applications.