Double-edged effects caused by magnesium ions and alkaline environment regulate bioactivities of magnesium-incorporated silicocarnotite in vitro

Magnesium (Mg) is an important element for its enhanced osteogenic and angiogenic properties in vitro and in vivo, however, the inherent alkalinity is the adverse factor that needs further attention. In order to study the role of alkalinity in regulating osteogenesis and angiogenesis in vitro, magnesium-silicocarnotite [Mg-Ca(5)(PO(4))(2)SiO(4), Mg-CPS] was designed and fabricated. In this study, Mg-CPS showed better osteogenic and angiogenic properties than CPS within 10 wt.% magnesium oxide (MgO), since the adversity of alkaline condition was covered by the benefits of improved Mg ion concentrations through activating Smad2/3-Runx2 signaling pathway in MC3T3-E1 cells and PI3K-AKT signaling pathway in human umbilical vein endothelial cells in vitro. Besides, provided that MgO was incorporated with 15 wt.% in CPS, the bioactivities had declined due to the environment consisting of higher-concentrated Mg ions, stronger alkalinity and lower Ca/P/Si ions caused. According to the results, it indicated that bioactivities of Mg-CPS in vitro were regulated by the double-edged effects, which were the consequence of Mg ions and alkaline environment combined. Therefore, if MgO is properly incorporated in CPS, the improved bioactivities could cover alkaline adversity, making Mg-CPS bioceramics promising in orthopedic clinical application for its enhancement of osteogenesis and angiogenesis in vitro.