In Vivo Self‐Growing Mineral Coating Enables Durable Protection on Mg Biometals for Bone Regeneration

Abstract Magnesium represents the revolutionary biometal for bone regeneration but necessitates protective coatings to mitigate its rapid biodegradation and promote osteogenesis. However, conventional coatings inevitably deteriorate in vivo due to the mechanical damage during implant fixation surgery and continuous exposure to corrosive biofluids. Herein, a coating strategy that utilizes biofluid components to dynamically ‘self‐grow’ a mineral coating instead of deterioration, mimicking tooth enamel growth through in vivo biomineralization, is proposed to overturn the instability of coatings. A dual‐layer system, consisting of a surface‐parallel fluoroapatite (FAP)‐crystal network layer and a fluoride‐releasing MgF 2 layer, is constructed on the Mg surface to catalyze the energetically favorable conversion of Ca 2+ and PO 4 3− ions from biofluids into new FAPs via fluoride‐combined FAP template‐boosted biomineralization. This dynamically grown FAP continuously densifies the coating by sealing internal voids and autonomously adapts to the highly corrosive environment. Consequently, the self‐growing coating effectively mitigates biocorrosion, maintains magnesium substrate integrity over two months in vivo, significantly improves osteointegration and accelerates bone regeneration by enhancing osteoblast adhesion, differentiation, and fostering endogenous mineralization. This innovative strategy leverages unlimited corrosive biofluids to dynamically create an anti‐corrosion coating in vivo, revolutionizing the development of durable and bioactive coatings for implanted biomaterials.