Gradient pH Hydrogel Promotes Infected Wound Healing through pH Regulation of Microenvironment.

A healthy skin surface has an acidic environment with an average pH below 5, which helps to protect against bacterial infection. A weakly acidic environment of the dermis not only reduces bacterial infection but also affects fibroblasts' activity, vascular endothelial cell activity, and the immune response. The natural pH gradient helps to ensure the integrity of the skin and accelerates the repair process, following skin damage. In this study, GelMA-based gradient pH hydrogel was proposed for infected skin wound healing. Experiments showed that the gradient pH hydrogel had good antibacterial effects and promoted the proliferation and migration of fibroblasts and endothelial cells. The gradient pH hydrogel lowered the pH of the wound bed, reduced the bacterial load, and induced macrophage polarization to M2 and neovascularization. The gradient pH hydrogel promoted hair follicle regeneration by modulating Treg cells. Thus, this hydrogel provides a new option for the treatment of bacterially infected wounds.