Additively Manufactured Metastable-β Ti-Nb-Zr-Sn Exhibits Superior Corrosion, Semiconducting, and Cell Metabolic...

Manufacturers frequently use Ti-6Al-4V for permanently implanted medical devices. While clinically successful, Ti-6Al-4V corrodes at modular taper interfaces in both the hip and knee. Additionally, additive manufacturing (AM) can develop biomaterials with the potential to improve upon Ti-6Al-4V's properties. In this study, we used AM to generate Ti-Nb-Zr-Sn, comparing the admixture to classically melted Ti-Nb-Zr and wrought-annealed Ti-6Al-4V. We asked (1) how does manufacturing alter Ti-Nb-Zr biomaterial structure; (2) do resulting structural differences govern corrosion and semiconducting properties; and (3) does biomaterial chemistry and structure affect cell metabolic activity? To answer these questions, we first used scanning electron microscopy and electron backscattered diffraction to characterize microstructure. Then, we elucidated the corrosion properties and semiconducting performance in 0.1 M H₂O₂ and PBS solutions. Next, we measured the cell metabolic activity after 24 and 72 h. Manufacturing profoundly altered the Ti-Nb-Zr biomaterials, with AM processes generating a columnar microstructure consisting of elongated grains. This contrasted with the equiaxed β grains of the alloy produced by melting processes. However, these structural changes had little effect on the corrosion or semiconducting properties. Additionally, both Ti-Nb-Zr-Sn and Ti-Nb-Zr exhibited increased corrosion resistance and decreased defect densities over Ti-6Al-4V in 0.1 M H₂O₂. Finally, we documented superior cell metabolic properties on polished and as-built Ti-Nb-Zr-Sn surfaces after 72 h. Combined, these results suggest an inhibitory effect of ZrO₂ oxides on reactive oxygen species and support the continued characterization of Ti-Nb-Zr-Sn as a candidate biomaterial.