Hydroxyapatite/Bioactive Glass Films Produced by a Sol-Gel Method: In Vitro Behavior

Hydroxyapatite (HA) and HA/bioactive glass (49S) films were deposited on Si(100) substrates by a sol-gel dip-coating method. The microstructure and in vitro bioactivity of the films were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Polycrystalline HA and amorphous bioactive glass films were obtained after annealing at 600 and 400 degrees C, respectively. The crystallization temperature of HA was determined to be around 568 degrees C. The surfaces of the HA films were covered with an apatite layer consists Of spherulites formed by nanosized needle-like aggregates after the soaking in simulated body fluid (SBF) for 10 days, while amorphous HA/bioactive glass surface was covered with larger spherical crystallites. Both XPS and EDS results obtained from HA/bioactive glass film, after soaking in SBF, showed increasing P amounts on the surface at the expense of Si. The higher density of the newly formed layer on HA/bioactive glass surface than that of the HA surface after 10 days of soaking was evidence of increased reaction rate and apatite forming ability when bioactive glass layer is present on the HA films.