Hydrothermally crystallized Sr-containing bioactive glass film and its cytocompatibility

Sr-containing bioactive glass film with the Sr/(Ca+Sr) atomic ratio of 20% was sol-gel coated on titanium substrate, followed by hydrothermal treatment in a mixed phosphate solution (8 mM CaHPO₄ and 2 mM SrHPO₄) and other media at 120 or 140 °C. X-ray diffraction (XRD) analysis confirms amorphous nature of the gel powder calcined at 610 °C, but small peaks of Ca_1.8Sr_0.2SiO₄ or Ca_1.5Sr_0.5SiO₄ are also present. The absorption bands of Si-O-Si, PO₄ and OH groups and a weak absorption band of NO₃ groups appear in FT-IR spectrum of the calcined gel powder. Hydroxyapatite (HA) is detected for the hydrothermally treated sample by XRD and Raman analyses. Sr-containing HA nanocrystallites are formed on the film through a dissolution and precipitation mechanism in the hydrothermal treatment. The appearant bonding strength is 21±1 MPa for the both samples. In the test with MC3T3-E1 cells, the two coated samples exhibit larger viability, higher ALP levels and better cell morphology than the polished sample.