Light-activated viologen-based metal-covalent organic framework sprayable hydrogel for accelerated healing of infected skin wounds

Bacterial resistance and recurrent infection remain major challenges for infected wound healing. Antibacterial photodynamic therapy (aPDT) features excellent spatiotemporal control and low risk of inducing bacterial resistance, making it a promising antibacterial modality. However, many photosensitizers used in wound therapy are photounstable, bind weakly to bacteria, and generate insufficient reactive oxygen species (ROS). We developed a viologen-functionalized metal-covalent organic framework (Vio-MCOF) by covalently embedding viologen units into the MCOF framework, and integrated this material into a sprayable, ionically crosslinked sodium alginate hydrogel. In this system, viologen units serve as electron mediators and work cooperatively with the copper-cluster active sites to suppress charge recombination and may increase ROS production under simulated solar light. The positive charge of the viologen units promotes electrostatic binding of Vio-MCOF to negatively charged bacterial membranes, improving its photodynamic antibacterial performance. In vitro experiments showed that Vio-MCOF at 200 μg mL-1 achieved a bactericidal rate of over 99% against S. aureus after 30 min of simulated solar light irradiation. In vivo experiments demonstrated that the Vio-MCOF hydrogel reduced bacterial colonization in infected wounds, suppressed TNF-α and IL-6 expression, alleviated inflammation, and promoted angiogenesis and collagen deposition, leading to accelerated wound healing. Collectively, the sprayable Vio-MCOF hydrogel holds promise as an antibiotic-free dressing for infected skin wounds.