Dependence of calcium phosphate formation on nanostructure of rutile TiO2(110) surfaces

To demonstrate the effect of the surface nanostructures on the osteoconductivity of titanium dioxide (TiO2), formation of calcium phosphate on the rutile TiO2(110) surfaces in Hanks' balanced salt solution (HBSS) was examined using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. When the TiO2(110) surfaces annealed in air were immersed in HBSS, calcium phosphate particles were formed on the surface. The calcium phosphate formation was suppressed by further annealing of the surfaces in O-2 before the immersion in HBSS. The suppression of calcium phosphate formation is attributed to the transformation of the topmost layer of the air-annealed TiO2(110) surface from amorphous to rutile. The arrangement of the phosphate ions adsorbed on the rutile (1 x 1) surface does not match the hydrogen phosphate ion lattice of the CaHPO4 sheet of brushite. (C) 2018 The Japan Society of Applied Physics