Block cationic copolymer/quaternary ammonium chitosan-based composite antibacterial hydrogel dressings with NIR photothermal effects for bacteria-infected wound healing.

Wound infections caused by pathogenic bacteria can cause delayed wound healing and even threaten the life of patients. Drug resistance and effectiveness with regard to traditional wound dressings have become urgent issues which need to be addressed. The antibacterial effect of hydrogels, as novel wound dressings, is through contact-active antibacterial was limited by the contact area and time. In this paper, MXene (a 2D carbonitride) has been employed as the substrate and via the in-situ reduction of silver nanoparticles and the polymerization of dopamine on its surface the photothermal agent MXene-Ag-PDA was obtained. This was then introduced into the hydrogel matrix via the block cationic polymer (AM-VBIMBr-AAPBA), oxidized sodium alginate (OSA) and quaternary ammonium chitosan (HACC). Multifunctional composite hydrogels (PNVAO/M-A-P) possessing photo-thermal effects and inherent antibacterial activity were obtained after crosslinking, and were employed as medical materials to promote the healing of infected wounds. The cationic groups contained in the PNVAO/M-A-P were capable of capturing and killing bacteria by electrostatic interactions, and produced local heat killing adsorption and residual bacteria in the surrounding solution under NIR irradiation, thereby shortening the antibacterial cycle and improving the sterilization efficiency. Meanwhile, the introduction of glycerin in the hydrogel improved its anti-freezing and anti-drying properties, enabling the hydrogel to function stably under extreme environments. PNVAO/M-A-P composite hydrogels based on chemical and dynamic crosslinking exhibited the desired mechanical strength, and via their self-healing ability can adapt to dynamic wounds. The hydrogel dressing showed excellent anti-freezing and anti-drying properties, high bovine serum albumin (BSA) adsorption capacity (308.17 mg·g), good biocompatibility (the cell viability exceeded 100 % after 48 h of incubation), antioxidant properties and excellent antibacterial activity (the sterilization rate can reach 99.9 %). Furthermore, the hydrogel was applied to infected wound treatment and was able to control the wound infection, reduce pro-inflammatory factor production, promote collagen deposition and neovascularization formation, and thus promote wound healing. Therefore, multifunctional composite hydrogels with synergistic antibacterial effects can be used as an novel dressing for the treatment of bacterial infected wounds.