Crosslinker-free PVA hydrogel incorporating a water-soluble Ir(III) photosensitizer for antibacterial photodynamic applications in wound healing.

Abstract

Bacterial infections, particularly those involving biofilm formation and antibiotic-resistant pathogens, severely impede wound healing. Photodynamic antibacterial therapy (PDT) offers a non-antibiotic, broad-spectrum antibacterial strategy via light-triggered reactive oxygen species (ROS) generation, yet poor photosensitizer retention and instability in exudative wounds limit its clinical translation. Herein, we report a crosslinker-free photodynamic hydrogel platform based on a physically assembled poly(vinyl alcohol) (PVA) network incorporating a water-soluble cyclometalated Ir(III) photosensitizer in its sodium salt form (IrONa). The hydrogel is fabricated via repeated freeze-thaw cycling, enabling homogeneous photosensitizer incorporation without chemical crosslinkers. Multivalent hydrogen bonding and nanoscale physical confinement effectively suppress premature photosensitizer leaching while preserving its photophysical activity. Upon visible-light irradiation, the FT-PVA/IrONa hydrogel generates sustained singlet oxygen with high efficiency, resulting in potent antibacterial activity against both Gram-positive and Gram-negative bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Notably, localized photodynamic action reduced mature biofilm biomass and viable biofilm-associated bacteria, resulting in a 71.2% inhibition rate against MRSA biofilms. In an MRSA-infected burn wound model, photodynamic activation of the FT-PVA/IrONa hydrogel significantly decreases bacterial burden, downregulates pro-inflammatory cytokines, and upregulates pro-angiogenic markers, ultimately accelerating wound closure and tissue reconstruction. This work establishes a simple yet effective strategy to embed photosensitizers into tissue-conformal hydrogels, offering an antibiotic-free platform for infected wound treatment.