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

Skin wounds are particularly susceptible to bacterialinfection,which seriously affects skin healing. Therefore, wound dressing withantibacterial properties is urgently needed for skin trauma treatment.Here, we have designed a hydrogel dressing by utilizing a multilayeredupconversion nanocomposite that is constructed by the upconversionnanoparticles (UCNPs) coated with a mesoporous silica-loaded zincphthalocyanine (ZnPc) photosensitizer. The nanocomposite can producesinglet oxygen for photodynamic therapy under 980 nm excitation byluminescent energy resonance transfer between UCNPs and ZnPc, whichendows the antibacterial activity during the wound healing process.Furthermore, by utilizing the non-toxic active ester of polyethyleneglycol as the cross-linking agent, the nanocomposite is assembledin chitosan to generate the hydrogel dressing, whereas chitosan isconsidered an ideal material for promoting wound healing. The experimentsshow that the dressing has good antimicrobial activity against Staphylococcus aureus and Escherichiacoli. Meanwhile, in vivo experiments demonstrate thatthe antibacterial hydrogel dressing can effectively reduce inflammationand significantly accelerate wound healing due to its low toxicity,deep tissue penetration, good biocompatibility, and strong antibacterialcapacity. Such a photodynamic hydrogel dressing designed here wouldprovide a practical application pathway for photodynamic sterilizationand treating emergencies as a total solution.