pH-switchable palladium nanozymes deliver GSH-scavenging α-bromocinnamaldehyde for MRSA-infected wound healing

Nanozymes show great potential in reactive oxygen species (ROS)-based antibacterial therapy. However, bacterial glutathione (GSH)-mediated ROS scavenging and tissue damage caused by residual ROS after sterilization remain challenges. Herein, we report a ROS-adaptively regulated M@PB, which is constructed by co-loading multienzyme Pd nanoparticles and a GSH scavenger α-bromocinnamaldehyde (BCA) onto mesoporous polydopamine (MPDA). The M@PB exhibits pH-switchable enzyme-like activities: under acidic conditions, it exerts peroxidase (POD)-like activity to generate ROS for efficient bacterial elimination; as bacteria are eradicated and the local pH rebounds, it switches to catalase (CAT)-like activity to scavenge residual ROS and produce oxygen, thereby accelerating cell migration. Furthermore, backbone-modified BCA exhibits strong GSH-scavenging activity, and its acid-triggered release from M@PB further disrupts bacterial antioxidant systems, driving greater oxidative stress to accelerate the antibacterial-to-healing progression. Experiments demonstrate that M@PB exhibits potent antibacterial and antioxidant properties with favorable biosafety, and effectively promote the healing of methicillin-resistant Staphylococcus aureus ( MRSA )-infected wounds. This work provides a pH-switchable nanoplatform that enables flexible regulation of ROS, offering a robust strategy for the care of wounds infected with drug-resistant bacteria.