Photo-Inspired Antibacterial Activity and Wound Healing Acceleration by Hydrogel Embedded with Ag/Ag@AgCl/ZnO Nanostructures

Abstract

Ag/Ag@AgCl/ZnO hybrid nanostructures are embedded in a hydrogel by a simple two-step technique. The Ag/Ag@AgCl nanostructures are assembled in the hydrogel via ultraviolet light chemical reduction followed by incorporation of ZnO nanostructures by NaOH precipitation. The hydrogel accelerates wound healing and exhibits high antibacterial efficiency against both Escherichia coli and Staphylococcus aureus under visible light irradiation. The Ag/Ag@AgCl nanostructures enhance the photocatalytic and antibacterial activity of ZnO due to the enhancement of reactive oxygen species by visible light. This hydrogel system kills 95.95% of E. coli and 98.49% of S. aureus within 20 min upon exposure to simulated visible light, and rapid sterilization plays a crucial role in wound healing. In addition, this system provides controllable, sustained release of silver and zinc ions over a period of 21 days arising from the reversible swelling-shrinking transition of the hydrogel triggered by the changing pH value in the biological environment. About 90% Zn²⁺ release is observed in the acidic environment after 3 days, whereas only 10% Zn²⁺ release occurs in the neutral environment after 21 days. In vivo results show that release of Ag⁺ and Zn²⁺ stimulates the immune function to produce a large number of white blood cells and neutrophils (2-4 times more than the control), thereby producing the synergistic antibacterial effects and accelerated wound healing.

Keywords: antibacterial activity; hydrogel; photodynamic therapy; visible light irradiation; wound healing.