# ZIF-8 Hydrogel-Mediated Regulation of Macrophage Phenotype Accelerates Frostbite Wound Healing

## TL;DR

A new hydrogel using OR@ZIF-8 nanoparticles improves frostbite healing by reducing inflammation and boosting tissue repair in mice.

## Contribution

A pH-responsive OR@ZIF-8@HA hydrogel is developed to enhance oxyresveratrol delivery and macrophage regulation for frostbite treatment.

## Key findings

- OR@ZIF-8 nanoparticles released 75.46% of OR under acidic conditions in 36 hours.
- The hydrogel reduced TNF-α and IL-6 by over 100% and increased IL-10 by 45% in vitro.
- In vivo, the treatment achieved 96.14% wound healing in 14 days in a mouse frostbite model.

## Abstract

Background: Frostbite injury creates an ischemic, hypoxic, and acidic microenvironment that often triggers severe oxidative stress and inflammation. Current therapeutic approaches are limited by low drug delivery efficiency and an inability to adequately regulate multiple pathological pathways. Although oxyresveratrol (OR) exhibits excellent antioxidant and anti-inflammatory activities, its application is hampered by poor aqueous solubility and low stability. Methods: We constructed Oxyresveratrol@Zeolitic Imidazolate Framework-8 nanoparticles (OR@ZIF-8) and further embedded them in a sodium hyaluronate (HA) matrix to form an OR@ZIF-8@HA composite hydrogel. The physicochemical properties and pH-responsive drug release behavior of the system were characterized. Its antioxidant activity, ability to promote cell migration, and capacity to modulate macrophage polarization were evaluated in cellular assays. The therapeutic efficacy was further investigated using a mouse frostbite model, with wound repair analyzed via histological staining. Results: The OR@ZIF-8 nanoparticles achieved a cumulative release rate of 75.46 ± 3.68% under acidic conditions within 36 h. In vitro experiments demonstrated that the formulation significantly scavenged TNF-α and IL-6, by 161.85 ± 19.43% and 125.37 ± 12.65%, respectively, and increased the level of IL-10 by 44.97 ± 4.57%. In a scratch assay, it promoted wound healing, achieving a closure rate of 97.55 ± 2.77% after 36 h. In vivo studies revealed that the OR@ZIF-8@HA treatment group achieved a wound healing rate of 96.14 ± 4.12% on day 14. Conclusions: The OR@ZIF-8@HA composite hydrogel effectively overcomes the limitations of OR application via intelligent pH-responsive delivery. Through synergistic multi-mechanistic actions, it significantly accelerates frostbite wound healing, offering a novel and efficient therapeutic strategy for frostbite management.