Thermochromic, Antibacterial, and Conductive Hydrogel Patch with Sandwich Structure for Visual Infectious Chronic Wound Care and Treatment.

Multifunctional smart hydrogel dressings that combine diagnosis and treatment are a popular solution for the care and treatment of infectious wounds. Herein, a sandwich structure hydrogel patch (PTP) composed of tannic acid modified gelatin (TGL) as the middle layer and polyvinyl alcohol hydrogel with sodium chloride and iodine (PAI/NS) as the inner and outer layer is successfully designed and assembled. The obtained PTP exhibits good mechanical performance, outstanding biocompatibility, and robust electrical conductivity. When attached to an active wound, the change of electrical signal caused by the movement of conductive ions (Na⁺ and Cl^-) in PAI/NS would reflect the integrity and fit of the gel patch. Meanwhile, the increased temperature of the wound elicits a temperature-activated acid-base color reaction between TGL and PAI/NS, indicating fever and wound infection. In turn, the infection degree of the wound is monitored to guide on-demand drug administration through photothermal antibacterial treatment. The results of in vivo and in vitro experiments demonstrate that the PTP hydrogel patch shows a remarkable anti-infection and pro-healing effect. This smart hydrogel system integrates real-time wound infection monitoring with anti-bacterial treatment, offering a viable strategy for visual, personalized management of infected chronic wounds.