Advanced hydrogel-based delivery of minoxidil for improved frostbite wound healing: formulation optimization, performance evaluation, and assessment of therapeutic efficacy.

Frostbite is a serious clinical condition in which delayed treatment usually results in irreversible tissue necrosis. Due to lack of effective therapeutic interventions, we have developed minoxidil-loaded chitosan (CH)-polyethylene glycol (PEG) hydrogel (MH) to treat frostbite injury. RSM-CCD was used to optimize the independent variables in order to maximize the gel fraction, swelling index and in vitro drug permeation studies. The MH formulation was characterized by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The healing activity was evaluated in L929 cells. The MH formulation was studied in experimentally induced frostbite in a rat model. Further, the efficacy was evaluated for wound closure rate, histopathological analysis, immunohistochemical expression of CD34, and levels of IL-6, IL-10, VEGF, and NO. MH showed a gel fraction (63.21 ± 3.28%), swelling index (479.79 ± 6.12%), and in vitro drug permeation (91.78 ± 10.17%). FESEM and AFM analyses validated its macroscopic properties. In L929 cell lines, MH showed significant cell proliferation, improvement of cell migration from the scratch assay and negligible toxicity. MH is also shown to be hemocompatible and non-irritant. Further, an in vivo study revealed significant improvement in the wound area with re-epithelization, angiogenesis, reduction of inflammation, and significant collagen depositions without the formation of scars. Based on these preclinical observations, it can be concluded that MH has the potential to be a promising therapeutic option for frostbite-induced tissue injury. Further studies, such as long-term stability and detailed molecular mechanisms, will be required for its clinical applicability.