In situ forming Hydrogel with adding ZnO Nano-particle for effectively methicillin-resistant Staphylococcus aureus infected frostbite injury.

Unlabelled: Hydrogel has emerged as a promising wound dressing material, and in situ forming hydrogel has emerged as a promising wound dressing recently. But most in situ forming hydrogel are normally unstable. Herein, we report an in-situ forming hydrogel synthesized from poly(Nisopropylacrylamide166---butyl acrylate9)-poly(ethyleneglycol)-poly(N-isopropylacrylamide166---butyl acrylate9) copolymer (P(NIPAM166--nBA9)-PEG-P(NIPAM166-conBA9), denoted as PEP) and zinc oxide nano-particle(ZnO nano-particle) in response to skin temperature. This thermoresponsive hydrogel exhibits sol-gel reversibility at high temperatures, which is closed to the temperature of human skin. To investigate its healing effects, we used the Hydrogel dressing® in an SD rat model. The biocompatibility and antibacterial ability against methicillin-resistant Staphylococcus aureus(MRSA) of this PEP-ZnO hydrogel wound dressing are confirmed in vitro and in vivo, which could transparently promote the healing of a MRSA-infected frostbitten skin Injury.

Materials And Methods: Thirty rats were randomly divided into two groups. The treatment group received hydrogel and transparent film dressing 30 min to 1 h post-burn, while the control group received only cotton dressing. The wound area was measured, and the wound closure rate was calculated on days 3, 7, and 14 post-surgery. Tissue samples were collected from each rat on these days and stored at -80 °C for histological analysis using H&E, Masson and immunohistochemical staining. This analysis assessed factors such as granulation tissue length, re-epithelialization, re-angiogenesis, collagen deposition, inflammatory cell infiltration, and collagen production. Clinical and histological assessments at 14 days showed more rapid healing in the hydrogel dressing group compared to the control group.

Conclusion: Our results indicate that the design of our hydrogel for cooling injury wounds effectively improves healing and mitigates the damage from low temperatures.