Influence of CAP-p15 Synthetic Peptide on the Precipitation of Calcium-phosphate Onto TiO₂ Surface

Objectives: The goal of this work is to determine the in vitro role of CAP-p15 on the apatites precipitation onto TiO2 surface.
Methods: We used TiO2 film of 1cm² synthesized by radio frequency evaporation cathode. The films were ultrasonically cleaned in distilled-deionized water, acetone, and ethanol solutions during 20 min each and rinsed with distilled-deionized water. The TiO2 films were incubated with CAP-p15, labeled with Alexaflúor-488 (1μg/ml) during 1hour at room temperature. To investigate the topography of films with and without CAP-p15, we used atomic force microscopy (AFM). To evaluate the formation of calcium-phosphate crystals, the films/CAP-p15 were immersed into a simulated body fluid (MgCl2 0.2mM, CaCl2 1mM, KH2PO4 4mM, KCl 16mM, NH4Cl 4.5mM) in HEPES 20mM buffer with pH 7. After 7 days incubation at 37 C. The films were analyzed with Scanning Electron Microscopy (SEM), Raman and Attenuated total reflection with infrared ATR-FTIR spectroscopy, and X-ray power diffraction (XRD).
Results: The topography analysis of CAP-p15 adsorbed onto TiO2 films, showed isolated spherical forms, which were corroborated by fluorescence images. The characterization of deposits obtained in the presence of CAP-p15 onto TiO2 films with SEM, Raman, ATR-FTIR and XRD, showed that CAP-p15 is actively involved in the formation and growth (size and shape) of hydroxyapatite crystals in vitro.
Conclusions: CAP-p15 adsorption onto TiO2 surfaces in a medium that imitates physiological conditions, shows that CAP-p15 regulates the morphology and growth of crystals which shown spectroscopic and crystallographic characteristics of Hydroxyapatite.