Sandwich-structure hydrogels implement on-demand release of multiple therapeutic drugs for infected wounds.

Wound infections bring huge challenges to clinical practice. A series of approaches are involved in the management of infected wounds including use of antibacterial agents, granulation tissue regeneration and scar prevention. In this study, we fabricated a sandwich-structure hydrogel dressing through layer-by-layer assembly of films and hydrogels. By pre-loading silver nanoparticles (AgNPs), vascular endothelial growth factors (VEGF) and ginsenoside Rg3 (Rg3) into each layer of the sandwich compound, this hydrogel could realize the sequential release of these drugs onto infected wound beds as demanded. Moreover, altering the thickness of middle layer could further change the drug delivery patterns characterized by delay at the initial releasing timepoint. When applying this dressing on infected wounds of rabbit ears, we found it could alleviate infection-induced inflammation, promote granulation tissue regeneration and inhibit scar formation. Collectively, the design of sandwich-structure hydrogels was facilitated to deliver specific drugs sequentially during their therapeutic time window for complicated diseases and has shown potential applications in infected wounds.