Fish scale-inspired biomimetic nanocoatings on magnesium implants for vascularized bone regeneration in infected bone defects

The regeneration of infected bone defects is still challenging and time-consuming, due to the adverse osteogenic microenvironment caused by bacterial contamination and pronounced ischemia. Biodegradable magnesium (Mg)-based alloys are desirable for orthopedic implants due to the mechanical properties approximating those of human bone and the released Mg²⁺ ions essential to osteogenic activity. However, the fast and uncontrolled self-degradation of Mg alloy, along with the inadequate antimicrobial activity, limit their strength in the osteogenic microenvironment. Inspired by the structural and physiological characteristics of “fish scales,” two-dimensional (2D) nanomaterials, black phosphorus (BP) and graphene oxide (GO), were assembled together under the action of pulsed electric field. The bionic 2D layered BP/GO nano-coating was constructed for infection resistance, osteogenic microenvironment optimization, and biodegradation control. In the early stage of implantation, it exerted a photothermal effect to ablate bacterial biofilms and avoid contaminating the microenvironment. The blocking effect of the “nano fish scales” - 2D material superposition regulated the degradation of implants. In the later stage, it attracted the migration of vascular endothelial cells (VECs) and released phosphate slowly for in situ mineralization to create the microenvironment favoring vascularized bone formation. It is indicated that the enhancement of microtubule deacetylation and cytoskeletal reorganization played a key role in the effect of VEC migration and angiogenesis. This study provided a promising bionic strategy for creating osteogenic microenvironments that match the sequential healing process of infected bone defects.