Harnessing Corrosion in A P(VDF-TrFE)/Mg Composite for Dynamic Passivation and Osteoimmunomodulation

Rather than suppressing corrosion, we propose "corrosion-guided functionalization", harnessing controlled Mg degradation as a programmable source of passivation and bioactivity. This concept is realized in an asymmetric, 3D-interlocked P(VDF-TrFE)/Mg mesh composite, where partial polymer encapsulation engineers interfacial micro-crevices that act as in situ micro-reactors. These micro-reactors confine initial corrosion products, triggering autonomous growth of a dynamic, self-adapting Mg(OH)₂ barrier. This passivation mechanism provides sustained corrosion stability compared to conventional sacrificial CaP coatings. Our composite achieves controlled corrosion that preserves the beneficial bioactivity of metallic Mg while avoiding the detrimental side effects that plague bare Mg. The composite exhibits robust antibacterial activity and reprograms the local immune microenvironment by polarizing macrophages toward a regenerative M2 phenotype through sustained corrosion-derived Mg^{2 +} release and mild alkalinity. This immunomodulation triggers a downstream cascade, enhancing angiogenesis and neurogenesis, which collectively drive accelerated bone regeneration in a critical-sized defect model. As a proof-of-concept, the composite thus serves as an advanced guided bone regeneration membrane, uniquely integrating sustained space maintenance with corrosion-derived bioactivity and enabling minimally invasive retrieval after healing. Beyond this demonstration, this work establishes "corrosion-guided functionalization" as a new strategy for corrosion control of biodegradable metals, offering a versatile tool for future biomaterial engineering.