Multilayered Upconversion Nanocomposite-Based Photodynamic Hydrogel Dressings for Wound Sterilizing and Healing

Skin wounds are particularly susceptible to bacterial infection, which seriously affects skin healing. Therefore, wound dressing with antibacterial properties is urgently needed for skin trauma treatment. Here, we have designed a hydrogel dressing by utilizing a multilayered upconversion nanocomposite that is constructed by the upconversion nanoparticles (UCNPs) coated with a mesoporous silica-loaded zinc phthalocyanine (ZnPc) photosensitizer. The nanocomposite can produce singlet oxygen for photodynamic therapy under 980 nm excitation by luminescent energy resonance transfer between UCNPs and ZnPc, which endows the antibacterial activity during the wound healing process. Furthermore, by utilizing the non-toxic active ester of polyethylene glycol as the cross-linking agent, the nanocomposite is assembled in chitosan to generate the hydrogel dressing, whereas chitosan is considered an ideal material for promoting wound healing. The experiments show that the dressing has good antimicrobial activity against Staphylococcus aureus and Escherichia coli. Meanwhile, in vivo experiments demonstrate that the antibacterial hydrogel dressing can effectively reduce inflammation and significantly accelerate wound healing due to its low toxicity, deep tissue penetration, good biocompatibility, and strong antibacterial capacity. Such a photodynamic hydrogel dressing designed here would provide a practical application pathway for photodynamic sterilization and treating emergencies as a total solution.