Metal release and cell biological compatibility of beta-type Ti-40Nb containing indium

Small indium (In) additions up to 5 wt % to the beta-type Ti-40Nb alloy effectively improve its mechanical biofunctionality. The impact on its biocompatibility is addressed in this work. Comparative electrochemical polarization studies and inductively coupled plasma optical emission spectrometry analyses were conducted in Tris-buffered saline (on the basis of 150 mM NaCl) with pH 7.6 and 2.0 at 310 ± 1 K with Ti-6Al-4V as reference. The metal ion releases from beta-type alloys were generally very low, for example, those of In³⁺ ions from (Ti-40Nb)-4In specimens were below 6 × 10^-7 mmol/cm² . X-ray photoelectron spectroscopy revealed the passivation mainly by Ti- and Nb-oxides with traces of In-oxides as the dominating surface process. In vitro studies demonstrate a better human bone marrow stromal cells (hBMSC) activity on the beta-type alloys in comparison to CP-Ti (grade 2), which is mainly due to their high Nb content. At 24 h after seeding on (Ti-40Nb)-4In the metabolic activity of hBMSC was 1.5-fold higher and after 11 days, the tissue non-specific alkaline phosphatase activity was 1.8-fold higher relative to values for CP-Ti. Surface treatments, like chemical etching or plasma oxidation, change the surface topography and the thickness and composition of the oxide layers, but they are not effective in further improving the cell response. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1686-1697, 2018.