An antibacterial bilayer hydrogel modified by tannic acid with oxidation resistance and adhesiveness to accelerate wound repair

Bacterial infection and oxidative stress remain critical problems for wound closure because they frequently trigger severe complications and delay wound healing. In addition, maintaining a moist microenvironment can promote skin regeneration. In this study, a bilayer hydrogel modified with tannic acid (TA) was constructed to accelerate wound repair. The bilayer hydrogel, composed of a layer with large pores to absorb the fluids and allow gas exchange and small pores to maintain the wound moist and prevent bacterial invasion, was initially developed. Thereafter, TA was introduced into the hydrogel to form a dual crosslinked network and endowed the hydrogel with adhesiveness, antibacterial, and oxidation resistance. In addition, the TA@bilayer hydrogel exhibited shape memory behaviour and self-healing ability due to the hydrogen bonds formed between TA and the bilayer hydrogel. As a result, the TA@bilayer hydrogel significantly promoted wound closure by accelerating collagen deposition, reducing tumour necrosis factor-α (TNF-α) levels, and facilitating the expression of vascular endothelial growth factor (VEGF).