Construction of Mg2+ loaded multifunctional casein phosphopeptide/alendronate sodium antioxidative coating for repairing osteoporotic fracture

Owning to seriously impaired capacity of bone regeneration, the repair of osteoporotic bone defect remains a major clinical challenge in orthopedics. For titanium mesh scaffolds of skull repair, to construct bio-coatings targeting the pathological environment of osteoporosis is significant. Here, tannic acid (TA)/casein phosphopeptide (CPP) based layer-by-layer (LBL) self-assembled coating that loaded with anti-osteoporotic alendronate sodium (AS) and bioactive Mg 2+ were prepared. The TA/CPP based LBL coatings showed good antioxidative function to effectively clear ABTS +• free radicals (scavenging rate of 64.29 ± 20.21 %) and inhibited the production of reactive oxygen species (ROS) in bone marrow mesenchymal stem cells (BMSCs) under oxidative stress conditions. All the LBL coatings exhibited good blood compatibility, and promoted early adhesion of BMSCs without affecting cell proliferation. In particular, the (TA/CPP-AS NPs) 4  + Mg 2+ coatings had both good alkaline phosphatase (ALP) activity and in vitro osteogenic mineralization, and could effectively promote the migration of human umbilical vein endothelial cells (HUVECs). In 8-weeks in vivo implantation experiments of osteoporotic skull defects, AS and Mg 2+ loaded LBL coating showed significant formation of new bone tissue. The study on the integrated system of antioxidative coating with bisphosphonates and active metal ions will serve as a promising strategy for osteoporotic bone defect repair.