Three-Step Regenerative Strategy: Multifunctional Bilayer Hydrogel for Combined Photothermal/Photodynamic Therapy to Promote Drug-Resistant Bacteria-Infected Wound Healing

Abstract

The drug-resistant bacterial-infected skin wound is still a severe healthcare problem. Uncontrolled bacterial infection, abundant reactive oxygen species (ROS) content, and prolonged inflammatory response are detrimental to wound healing. Moreover, excessive vessel growth can result in unsatisfactory scar formation. Herein, a three-step regenerative strategy based on a bilayered gelatin/acryloyl β-cyclodextrin (BGACD) hydrogel containing physical host–guest complexations and chemical crosslinks is proposed. The hydrogel is loaded with humic acids (HAs) and astragaloside IV (AS) in the lower layer and verteporfin (Vt) in the upper layer. Different gelatin/acryloyl β-cyclodextrin ratios endow the lower and upper layers of the hydrogel with different degradation rates. Under light irradiation, the combination of HAs-induced photothermal therapy (PTT) and verteporfin-induced photodynamic therapy effectively inhibits MRSA growth. The HAs and astragaloside IV are released from the lower layer to scavenge ROS and promote M2 macrophage polarization and angiogenesis during the inflammation and early proliferation phases, while verteporfin releases from the upper layer suppress excessive vessel growth during the late proliferation and remodeling phases. The HAs-AS@Vt@BGACD hydrogel successfully achieves rapid and scarless wound healing in an MRSA-infected wound model in rats. Therefore, the HAs-AS@Vt@BGACD hydrogel shows promising potential for the treatment of drug-resistant bacteria-infected skin wound healing.