Bioresponsive Dual Microspheres Embedded in a Hydrogel: A Sequentially Triggered Strategy for Regulating Diabetic Wound Healing

Chronic diabetic wounds complicated by methicillin-resistant Staphylococcus aureus (S. aureus) (MRSA) remain refractory because the milieu evolves from a protease- and bacteria-dominated inflammatory phase to a reactive oxygen species (ROS)-rich, angiogenesis-impaired reparative phase. Here we report a stage-adaptive hydrogel dressing that integrates orthogonal, pathology-stage-driven activation with pathological-factor neutralization coupled to triggered delivery. Two bioresponsive microspheres are embedded in the hydrogel: MMP-9-responsive gelatin methacrylate (GelMA) microspheres loaded with a cationic antimicrobial peptide (ILRWPWWPWRRK-NH₂), and ROS-responsive HA-PBA-PVA microspheres loaded with vascular endothelial growth factor (VEGF). In the early stage, elevated MMP-9 cleaves GelMA microspheres, consuming MMP-9 and releasing AMP to eradicate MRSA and mitigate infection-driven inflammation. In the later stage, ROS degrades HA-PBA-PVA microspheres, quenching ROS while releasing VEGF to restore endothelial function and neovascularization. In vitro, the system shows stimuli-responsive release, potent antibacterial activity, ROS scavenging, and improved endothelial migration and tube formation under oxidative stress. In a streptozotocin-induced diabetic rat model with MRSA-infected full-thickness wounds, the dual-microsphere hydrogel accelerates closure, reduces bacterial burden and inflammation, enhances collagen deposition and mature vessel formation, and shows no systemic toxicity. This work demonstrates a translational, stage-matched strategy for regulating infected diabetic wounds.