Adhesive chitosan-based hydrogel assisted with photothermal antibacterial property to prompt mice infected skin wound healing

Bacterial infection of wounds is an escalating medical problem, issuing threats to both global public health and personal health. Photothermal antibacterial technology as a novel sterilization strategy has outstanding sterilization efficiency, high safety and low risk of emergence of drug-resistant bacteria. By combining inherent antibacterial activity and light-assisted antibacterial treatment, developing novel multifunctional dressings with synergistic high-efficiency antibacterial effects and also promoting wound healing possesses attractive advantages in the field of treating bacterial wound infections in clinical care. Herein, a multifunctional hydrogel formed by in situ photo-cross linking was designed and prepared by first grafting methacrylic anhydride as a photosensitizer onto chitosan, and then introducing oxidatively synthesized polydopamine (PDA). The physicochemical characterizations of the synthesized hydrogels demonstrated their tunability certainly associated with PDA concentration, including pore size, water swelling, rheological properties and in vitro degradability. In addition, the composite hydrogels exhibited good adhesion, anti-oxidation and photothermal properties due to the existence of PDA. Within 10 min upon exposure to 808 nm near-infrared (NIR) light irradiation, this hydrogel system displayed outstanding antibacterial activity against Staphylococcus aureus with almost 100% killing efficiency, of which rapid efficient sterilization plays a significant role in wound healing. Moreover, the hydrogel is capable of cytocompatibility and has low toxicity to murine fibroblasts (L929 and NIH/3T3). In the full-thickness wound defect infection model in mice, the wound closure ratio, inflammatory response, fibroblasts, neovascularization and epithelialization were measured. Animal experiments also reveal that the hydrogel assisted with NIR laser irradiation can inhibit effectively infection at an early stage and accelerate the wound healing process. In summary, this novel multifunctional injectable hydrogel exhibits excellent swelling capacity, bio-adhesion, antioxidant property, photothermal activity, efficient antibacterial property and facilitates skin healing, which has great promising application as a medical dressing biomaterial in infected wound care fields.