Revisiting bioactivity of calcium titanate and titanium dioxide: Hydrolysis and complexation effects in osteogenic medium

Abstract

This study characterized laser-deposited CaTiO3 coats on several substrates by electron microscopy, X-ray diffraction, and Raman spectra. The hydrolytic stability of such coats exposed to ambient air and immersed into culture and osteogenic media has been respectively assessed by X-ray photoelectron spectra and energy dispersive X-ray analysis. It is shown these coats on titanium and micro/nanostructured oxidic titanium are not stable in air and culture or osteogenic media where they undergo hydrolysis and Ca leakage. The role of this hydrolysis is assessed and discussed in terms of not yet acknowledged complexation of the developing TiO2 surface with constituents of Dulbecco's Modified Eagle's medium. The effect of the deposited and additionally heated CT coatings on human mesenchymal stem cells is assessed regarding survival, proliferation and differentiation towards the osteogenic lineage in osteogenic medium. It is also stressed that the identified CaTiO3 hydrolysis in air and aquatic media seriously impacts the interpretation of bioactivity and physicochemical, catalytic and photocatalytic properties of CaTiO3 surfaces, which has not been yet admitted and led to erroneous conclusions in many previous studies.