Beta-Titanium Alloy Covered by Ferroelectric Coating–Physicochemical Properties and Human Osteoblast-Like Cell Response

Abstract

Beta-titanium alloys are promising materials for bone implants due to their advantageous mechanical properties. For enhancing the interaction of bone cells with this perspective material, we developed a ferroelectric barium titanate (BaTiO3) coating on a Ti39Nb alloy by hydrothermal synthesis. This coating was analyzed by scanning electron and Raman microscopy, X-ray diffraction, piezoresponse force microscopy, X-ray photoelectron spectroscopy, nanoindentation, and roughness measurement. Leaching experiments in a saline solution revealed that Ba is released from the coating. A progressive decrease of Ba concentration in the material was also found after 1, 3, and 7 days of cultivation of human osteoblast-like Saos-2 cells. On day 1, the Saos-2 cells adhered on the BaTiO3 film in higher initial numbers than on the bare alloy, but they were less spread, and their initial proliferation rate was slower. These cells also contained a lower amount of beta1-integrins and vinculin, i.e., molecules involved in cell adhesion, and produced a lower amount of collagen I. This cell behavior was attributed to a higher surface roughness of BaTiO3 film rather than to its potential cytotoxicity, because the cell viability on this film was very high, reaching almost 99%. The amount of alkaline phosphatase, an enzyme involved in bone matrix mineralization, was similar in cells on the BaTiO3-coated and uncoated alloy, and on day 7, the cells on BaTiO3 film attained a higher final cell population density. These results indicate that after some improvements, particularly in its roughness and stability, the hydrothermal ferroelectric BaTiO3 film could be promising coating for improved osseointegration of bone implants.