A microenvironment-adaptive bilayer composite dressing for disrupting MRSA biofilms and promoting wound regeneration via ROS-mediated immune regulation

(MRSA) biofilm-infected wounds remain difficult to treat because persistent biofilm protection, oxidative stress imbalance, and unresolved inflammation jointly hinder tissue repair. Here, we developed a microenvironment-adaptive bilayer composite dressing (OQT/P) by integrating a pH-responsive copper-based nanozyme into a dynamically crosslinked hydrogel and coupling it with an outer electrospun fibrous membrane. This asymmetric structure enables stage-specific regulation of the infected wound microenvironment. In the mildly acidic infection phase, the embedded nanozyme promotes localized reactive oxygen species (ROS) generation to disrupt MRSA biofilms and enhance antibacterial efficacy. As the wound environment gradually returns toward neutrality, the system shifts toward ROS scavenging, thereby alleviating oxidative stress and suppressing inflammatory amplification. In vitro, OQT/P exhibited favorable interfacial stability, pronounced antibacterial and antibiofilm activity, good cytocompatibility, and pro-angiogenic potential. In a full-thickness MRSA biofilm-infected wound model, OQT/P markedly reduced bacterial burden and ROS accumulation, accelerated wound contraction, and achieved approximately 98.07 ± 0.90% wound closure by day 12. Histological and immunofluorescence analyses further demonstrated attenuated inflammation, enhanced collagen deposition, improved neovascularization, and more advanced tissue remodeling. Transcriptomic profiling, supported by ELISA and Western blot validation, showed that these therapeutic effects were associated with coordinated suppression of infection- and inflammation-related pathways, particularly the NF-κB, TNF, and Th17 axes, together with promotion of a repair-associated immune phenotype. Overall, this study presents a non-antibiotic strategy for MRSA biofilm-infected wounds and demonstrates the therapeutic potential of combining bilayer dressing architecture with dynamic redox regulation for infection control and regenerative repair.