Osteogenic Potential of Additively Manufactured TiTa Alloys

The only alloy currently utilized for additive manufacture of bone implants, Ti-6Al-4V, has a high elastic modulus and bioinert surface, potentially inducing stress shielding and hindering osseointegration. Low-modulus materials with bioactive surfaces could significantly reduce implant failure rates by improving the interaction between implants and the surrounding bone. In this study, laser powder bed fusion Ti25Ta and Ti6STa alloys, highlighted previously for their low moduli, were assessed for their surface osteogenic potential, using human bone marrow mesenchymal stromal cells (hBMSCs). Polished metallic substrates were utilized to avoid the effects of surface topography on cell fate and highlight the chemical effect of the Ta content. Electron-dispersive X-ray and X-ray photoelectron spectroscopy revealed surface Ta enrichment on the polished TiTa substrates. XPS measured Ta oxide contents of 8.0 and 16.5 at % for the Ti25Ta and Ti65Ta alloys, respectively. In vitro testing revealed increased alkaline phosphatase activity and mineralization of hBMSCs on the TiTa alloys compared to the Ti-6Al-4V control and only minor differences in biological behavior between the Ti25Ta and Ti65Ta alloys. It was concluded that the Ti25Ta composition, with a lower Ta content but equivalent biological response, was the most promising composition for additively manufactured bone implants.