Moisture-Balanced Antibacterial Dressings Promote Wound Healing by Maintaining a Modulating Microenvironment

Wound healing depends on a suitable microenvironment and infection control. However, existing dressings fail to meet the needs of moisture balance and antibacterial properties at the same time. In this study, we synthesized a moisture-balancing antibacterial dressing, polyurethane@polydopamine@silver(PU@PDA@Ag), by soaking dopamine-coated polyurethane (PU@PDA) in a silver nitrate solution. The performance of the dressing was then evaluated in vitro and in vivo. In vitro experiments revealed that compared with nonwoven fabrics and hydrogels, PU@PDA@Ag2.5 prepared with 2.5 mg/mL silver nitrate had excellent moisture absorption-water retention performance (a swelling rate of 1000% for 1 h and a water retention rate of 481.69% for 6 h). SEM, EDS, and FTIR confirmed that the silver nanoparticles were loaded uniformly by PDA, the porous structure of PU was not destroyed, the water contact angle decreased to 60.6°, and the hydrophilicity improved. This dressing had no significant cytotoxicity or systemic toxicity and had good biocompatibility. The inhibition zone areas against S. aureus and E. coli reached 113.8 and 94.7 mm², respectively, and they were able to kill bacteria by destroying bacterial cell membranes. In a full-thickness infection mouse model, PU@PDA@Ag2.5 reduced the average healing time from 16-17 days (PU group or Vaseline group) to 12 days, accelerated re-epithelialisation, promoted granulation tissue formation and collagen deposition. Transcriptome sequencing showed that PU@PDA@Ag2.5 may regulate the Wnt pathway (which promotes regeneration) through up-regulation and NOD-like receptors and the RAS/PI3K/Akt/mTOR pathway (which causes inflammation) through down-regulation. Immunohistochemistry and ELISA validation showed that PU@PDA@Ag2.5 promoted the proliferation of proliferating cells (PCNA positive) and neovascularisation (CD31 positive) and reduced the expression levels of pro-inflammatory cytokines such as IL-1β, IL-6, TNF-α), which were consistent with the sequencing results. This study has verified that PU@PDA@Ag2.5 can regulate the humidity balance and antibacterial properties simultaneously, providing a dressing option for infected wounds repair.