Surface properties and cell response of fluoridated hydroxyapatite/TiO2 coated on Ti substrate

Dense and well-crystallized TiO2 and fluoridated hydroxyapatite (FHAp) films with TiO2 as a buffer layer were deposited on Ti substrates using a sol-gel spin-coating technique. X-ray diffraction showed a positive correlation between the level of F− incorporation into the HAp structure and the crystallinity of the HAp phase and the concentration of the FHAp phase. The decrease in water contact angle was attributed mainly to the increase in total surface energy of the FHAp/Ti and FHAp/TiO2/Ti as well as the increased polar component in FHAp. The FTIR spectra of the FHAp coated samples showed a weak absorption band at PO43- (1040 and 1092 cm−1) and P-O (875 cm−1), and several strong absorption bands between 3450 and 3550 cm−1 due to F-OH and OH−. The critical load values measured by the scanning scratch tester showed that the adhesion strength of the FHAp/TiO2 coated Ti substrate was 1.2-1.7 times higher than that of the HAp and FHAp coated Ti substrate. The level of cell attachment on FHAp and FHAp/TiO2 coated Ti substrates were 1.4 and 1.7 times higher than that on the HAp coated Ti substrate, respectively.