Meso-macroporous crack-free nanohydroxyapatite coatings templated by C12 E10 diblock copolymer on Ti6Al4V implant materials toward human osteoblast-like cells.

Abstract

Meso-macroporous nanohydroxyapatite coatings (MHACs) were synthesized on Ti6Al4V implant materials calcined at different temperatures using a nonionic diblock copolymer template (C12 E10 ) by sol-gel and dip-coating methods. To improve the bonding strength between the substrate and coating, a TiO2 intermediate layer was applied on the surface of the substrates. The physicochemical and structural properties of MHAC samples were fully studied by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, scanning probe microscopy, field-emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller method, and contact angle measurements. Based on the data obtained, the hydroxyapatite phase with a flower-like morphology was formed on the Ti6Al4V substrates in all of the samples. According to confocal optical microscopy and FESEM images, there was no macrocrack and microcrack on the MHACs, whereas they were accompanied by macroporosities and mesoporosities on top of the coatings. By increasing the calcination temperature from 500°C to 650°C, the crystallite sizes increased, while the surface roughness value and hydrophilicity decreased. A reduction in specific surface area and an increase in the pore diameters occurred as the calcination temperature increased. In addition, the assessment of protein adsorption behavior over the samples revealed that the adsorption amounts significantly increased as the substrates were coated with HAP; however, the affinity of surface for protein adsorption was strictly dependent on the surface topography and hydrophilicity. in vitro cellular assay disclosed a great cytocompatibility in terms of adhesion and proliferation in MHAC samples as compared with that in TiO2 -coated and bare substrates. Regarding the physicochemical properties and biological studies, MHAC calcined at 650°C was deemed optimal for bone tissue engineering.