A sodium phytate–ethyl cellulose coating with sustained oleoyl serine release enables spatiotemporal osteoimmune regulation of magnesium implants

Biodegradable magnesiumMgimplants hold immense potential in orthopedics,yettheir rapid degradation,insufficient osseointegration,and immune imbalance remain major barriers to clinical translation.This study developedasodium phytateSPpassivation layer and an ethyl celluloseECbarrier loaded with oleoylserineOSmultifunctional coatingonMgimplant surfaces.ThisSP-EC-OScoating achieves spatiotemporal synergistic regulation throughatriple mechanism of"chemical passivation,barrier isolation,signal-controlled release."TheSPlayer enhances interfacial bonding strength and corrosion resistance,theEClayer providesaplatform for controlled degradation and sustained release,while the continuous release ofOSsynergistically modulates cellular behavior withMg2+.In vitro results demonstrated that theMg-SP-EC-OSsignificantly enhancing corrosion resistance whileitsprogrammable release synchronizes with the bone regeneration cascade.More importantly,the synergistic effect ofOSandMg2+promotes osteoblast differentiation and mineralization,inhibits osteoclast activation,and induces macrophage polarization toward the M2 phenotype,achieving immune regulation-driven bone regeneration.In vivo validation of the femoral defect model in ratshasshown thatMg-SP-EC-OSimplants induce macrophage polarization toward the M2 phenotype through immune regulation,significantly promotenewbone formation,reduce bone-implant interface cavities,and maintain excellent systemic biosafety.This multifunctional coating combines corrosion resistance,immunomodulation,and spatiotemporal osteogenic effects,achieving spatiotemporally controlled degradation aligned with the bone healing process.Itprovidesaviable strategy for developinganewgeneration of degradable magnesium-based orthopedic implants.