Photothermal-enhanced antibacterial and antioxidant hydrogel dressings based on catechol-modified chitosan-derived carbonized polymer dots for effective treatment of wound infections

Bacterial infection and excessive reactive oxygen species (ROS) remain challenging factors contributing to the delayed healing of chronic wounds. Although various antibacterial and antioxidant hydrogel dressings have been developed to accelerate wound healing, multifunctional hydrogels fabricated by rationally designing and introducing carbonized polymer dots (CPDs) have rarely been reported. Herein, inspired by the mussel biomimetic approach, we synthesized 3,4-dihydroxybenzaldehyde functionalized chitosan (DFC), and then the polymeric precursor was pyrolyzed into CPDs with abundant amino and catechol groups on the surface, which endowed it with a highly positively charged surface that could activate the photothermal effect under near-infrared (NIR) light irradiation. Finally, the nanocomposite hydrogel (PVA@CPDs) was simply constructed by directly mixing polyvinyl alcohol (PVA) with CPDs, utilizing the freeze-thaw cycle method to form a gel, in which, CPDs as a center of polyfunctional nanoparticles drove the formation of PVA microcrystalline crosslinking and endowed the PVA substrate with versatile functionalities. Remarkable and comprehensive improvements in the swelling behavior, mechanical properties and adhesive strength of the hydrogel could be conveniently achieved with the suitable loading of CPDs. The in vitro experiments demonstrated that the PVA@CPDs hydrogel presented broad-spectrum and rapid bactericidal activity, concurrently acting as an effective antioxidant being able to scavenge free radicals. In addition, no obvious cytotoxicity was observed for the multifunctional hydrogel after incubation with L02 cells. In vivo evaluation in an infected full-thickness skin wound model demonstrated that the PVA@CPDs hydrogel promoted wound closure without any side effects. As a consequence, the current work manifests a facile yet versatile strategy to develop effective and biocompatible multifunctional hydrogel dressings for bacteria-infected wound healing.