Fabrication of dual physically cross-linked polyvinyl alcohol/agar hydrogels with mechanical stability and antibacterial activity for wound healing

Bacterial infection is one of the most critical obstacles in wound healing, and severe bacterial infections can lead to inflammatory conditions and delay the healing process. Herein, a novel hydrogel based on polyvinyl alcohol (PVA), agar, and silk-AgNPs was prepared using a straightforward one-pot physical cross-linking method. The in situ synthesis of AgNPs in hydrogels exploited the reducibility of tyrosine (Tyr tyrosine) in silk fibroin, which endowed the hydrogels with outstanding antibacterial qualities. In addition, the strong hydrogen bond cross-linked networks of agar and the crystallites formed by PVA as the physical cross-linked double network of the hydrogel gave it excellent mechanical stability. The PVA/agar/SF-AgNPs (PASA) hydrogels exhibited excellent water absorption, porosity, and significant antibacterial effects against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Furthermore, in vivo experimental results confirmed that the PASA hydrogel significantly promoted wound repair and skin tissue reconstruction by reducing inflammation and promoting collagen deposition. Immunofluorescence staining showed that the PASA hydrogel enhanced CD31 expression to promote angiogenesis while decreasing CD68 expression to reduce inflammation. Overall, the novel PASA hydrogel showed great potential for bacterial infection wound management.