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

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-co-n-butyl acrylate9)-poly(ethyleneglycol)-poly(N-isopropylacrylamide166-co-n-butyl acrylate9) copolymer (P(NIPAM166-co-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.