An all-in-one injectable biocement: self-setting magnesium phosphate for bone repair, fracture adhesion and osteoporotic fixation

Conventional bone cements face critical limitations in biodegradability, bioactivity and mechanical compatibility. To overcome these challenges, an all-in-one injectable magnesium phosphate cement (MPC) is engineered for bone repair, fracture adhesion and osteoporotic fixation. This functional platform integrates rapid self-setting, high early compressive strength and controlled degradation synchronized with bone formation. Unlike bioinert poly(methyl methacrylate) or slow-degrading calcium phosphate cements, MPC offers a superior bioactive alternative. It promotes bone regeneration through the sustained release of osteogenic Mg²⁺ ions, which accelerate osteoblast differentiation and angiogenesis. Comprehensive characterization confirms MPC's dense microstructure, mild exothermic reaction, physiological pH stability and biocompatible degradation, eliminating risks of thermal necrosis or toxic ion accumulation. The MPC demonstrates outstanding initial mechanical properties under <i>in vivo</i>-like conditions characterized by a warm and humid environment. <i>In vitro</i> studies show that MPC significantly promotes cell migration, upregulates the expression of osteogenic markers and enhances mineralized matrix deposition. Its controlled degradation behavior sustainably releases osteogenic Mg²⁺ ions, which orchestrate the proliferation of bone marrow stromal cells and facilitate RUNX2-mediated osteogenic differentiation, collectively accelerating the mineralization process. <i>In vivo</i> evaluations further reveal multi-functional bone regenerative capabilities: MPC dynamically guides defect repair through degradation-coupled bone ingrowth, achieving seamless integration without interfacial gaps, and significantly augments screw fixation stability via robust osseointegration. With exceptional adhesion to diverse substrates (tantalum, PLA, bone; 5.5× stronger than CPC on PLA) and intrinsic safety, MPC establishes an advanced platform for orthopedic regeneration and fixation.