Pearl-Like Bioinspired Coating Enables Regulation of Mg Degradation for Osteoporotic Bone Repair

In osteoporotic bones, the stability of orthopedic implants is compromised, and excessive M1 macrophage polarization at the bone-implant interface disrupts bone-immune homeostasis, leading to implant loosening or failure. To address this, this study develops a bionic magnesium alloy internal fixation coating inspired by the "brick-and-mortar" structure of pearl, aiming to improve bone-implant integration and vascularization in osteoporotic conditions. The multifunctional coating consists of a calcium phosphate (Ca-P) "brick" layer, which serves as a mineralization template and corrosion barrier, and fibronectin-mimetic peptides (Fn-mimetic peptides) as the "mortar" to promote cell adhesion, regulate immune responses, and stimulate angiogenesis. This bionic multilayer structure not only alleviates oxidative stress in the osteoporotic microenvironment but also fosters immune regulation-osteogenesis coupling and improves the bone-vascular-immune microenvironment. It precisely controls the degradation rate of Mg alloys and enhances tissue repair. The CaP layer reduces rapid degradation and prevents hydrogen gas release and local alkalinization, whereas Fn-mimetic peptides enhance early bone integration and vascularization. The synergistic effect of the magnesium alloy implant and bionic coating significantly improved bone implant stability, regeneration, and vascularization, as demonstrated in osteoporotic rat models, offering a promising strategy for the design of bone repair materials under pathological conditions.