The failure of wound healing is majorly attributed to uncontrolled bleeding and bacterial infections. However, developing a wound plaster that can stop bleeding, resist blood extravasation, and realize directional transportation of drugs to promote wound healing remains a significant challenge. Herein, a superhydrophilic/hydrophobic polyvinyl alcohol/chitosan/silver@Thermoplastic polyurethane (PVA/CS/Ag@TPU) Janus membrane with structural and wettability gradients is developed. In this newly developed membrane, water is absorbed from blood via the superhydrophilic layer, which is attached to the wound, and the charge interactions between platelets and the introduced chitosan (CS) promote blood clotting. The capillary pressure resistance (∆p > 0) of the superhydrophilic layer toward the hydrophobic layer prevents blood permeation, thereby reducing blood loss. The favorable ∆p (< 0) of the membrane based on its structural and wettability gradients can realize the directional transportation of drugs that promote wound healing from the hydrophobic to the superhydrophilic layer. The incorporation of CS and silver endows the Janus membrane with intrinsic antibacterial properties (99.9%). The formation of the hydrated layer on the hydrophilic layer imparts a resisting effect, further endowing the membrane with antiadhesion and antibacterial properties. Experiments involving mice with full-thickness skin wounds revealed that the wound-healing rate increased from 87.65% to ~ 100% when the Janus membrane was loaded with the prehealing drug. Moreover, the dressing accelerated wound healing, regenerated epidermal and granulation tissues, promoted collagen formation, and reduced scar size. Thus, this gradient design strategy opens an avenue for the development of next-generation wound dressings.

Graphical abstract