Silanized NaCa₂HSi₃O₉ nanorods with a reduced pH increase on Ti for improving osteogenesis and angiogenesis in vitro

Extracellular Ca and Si can enhance the response of osteogenesis related cells and new bone formation. Calcium silicate-based ceramics are bioactive, biodegradable and can rapidly release large amounts of Ca and Si. However, the concurrently high pH value in the microenvironment induces cell injury, resulting in poor osseointegration and implant loosening. In this study, NaCa₂HSi₃O₉ nanorods were initially fabricated on Ti by micro arc oxidation and hydrothermal treatment, and then covalently immobilized with a self-assembled NH₂ functionalized silane layer. The microstructure and degradation behavior of the nanorods before and after silanization treatment were compared. Their osteoblast (hFOB1.19) and endotheliocyte (HUVECs) response in vitro was evaluated. After silanization treatment, an amorphous layer of silane networks with a thickness of 10 nm formed on nanorods, and this layer didn't change the coating microstructure obviously. It slightly decreased the hydrophilicity and acted as a barrier to isolate nanorods from directly contacting medium, resulting in a slower degradation rate. Silanized NaCa₂HSi₃O₉ nanorods improved the adhesion and proliferation of HUVECs or hFOB1.19 compared with untreated nanorods and showed similar adhesion and proliferation but promoted differentiation of HUVECs and hFOB1.19 compared with TiO₂. It is demonstrated that silanized NaCa₂HSi₃O₉ nanorods allow efficient Ca and Si release and controlled pH increase. It should be a potential coating that can be applied on Ti implants.