Laser-synthesized nanocrystalline, ferroelectric, bioactive BaTiO₃/Pt/FS for bone implants

The goal of our study is to design BaTiO₃ ferroelectric layers that will cover metal implants and provide improved osseointegration. We synthesized ferroelectric BaTiO₃ layers on Pt/fused silica substrates, and we studied their physical and bio-properties. BaTiO₃ and Pt layers were prepared using KrF excimer laser ablation at substrate temperature T_s in the range from 200°C to 750°C in vacuum or under oxygen pressure of 10 Pa, 15 Pa, and 20 Pa. The BaTiO₃/Pt and Pt layers adhered well to the substrates. BaTiO₃ films of crystallite size 60-140 nm were fabricated. Ferroelectric loops were measured and ferroelectricity was also confirmed using Raman scattering measurements. Results of atomic force microscopy topology and the X-ray diffraction structure of the BaTiO₃/Pt/fused silica multilayers are presented. The adhesion, viability, growth, and osteogenic differentiation of human osteoblast-like Saos-2 cells were also studied. On days 1, 3, and 7 after seeding, the lowest cell numbers were found on non-ferroelectric BaTiO₃, while the values on ferroelectric BaTiO₃, on non-annealed and annealed Pt interlayers, and on the control tissue culture polystyrene dishes and microscopic glass slides were similar, and were usually significantly higher than on non-ferroelectric BaTiO₃. A similar trend was observed for the intensity of the fluorescence of alkaline phosphatase, a medium-term marker of osteogenic differentiation, and of osteocalcin, a late marker of osteogenic differentiation. At the same time, the cell viability, tested on day 1 after seeding, was very high on all tested samples, reaching 93-99%. Ferroelectric BaTiO₃ films deposited on metallic bone implants through a Pt interlayer can therefore markedly improve the osseointegration of these implants in comparison with non-ferroelectric BaTiO₃ films.