Intelligence-responsive wettability switch coating on magnesium implants for treating osteoporotic fracture

Osteoporotic fracture healing is frequently complicated by elevated levels of reactive oxygen species and disrupted bone homeostasis. Biodegradable magnesium alloys are promising orthopedic implants, but rapid degradation in oxidative, acidic osteoporotic microenvironments limits their clinical application. In this study, we develop a reactive oxygen species-responsive hydrogel coating of tannic acid and gelatin methacryloyl on magnesium implants via a metal-phenolic network. We show that this firmly adhering coating significantly decelerates magnesium degradation while scavenging reactive oxygen species on demand. In osteoporotic rat models, we demonstrate that coated implants effectively reduce oxidative stress and facilitate bone healing. Mechanistically, single-cell transcriptomics reveals that the coating activates the nuclear factor erythroid 2-related factor 2 signaling pathway in bone marrow mesenchymal stromal cells and bone marrow-derived macrophages, enhancing osteogenesis while inhibiting osteoclastogenesis. Consequently, this multifunctional coating provides corrosion protection and a targeted therapeutic approach to enhance osteoporotic fracture healing under oxidative stress.