Influence of metal oxides on biocompatibility of additively manufactured NiTi

In order to properly satisfy biomedical constraints for cardiovascular applications, additively manufactured NiTi scaffolds required further process and metallurgical engineering. Additively manufactured NiTi materials for cardiovascular use will have to undergo surface finishing in order to minimize negative surface interactions within the artery. In this study, we sought to understand biocompatibility from chemically etched additively manufactured NiTi scaffolds by laser powder bed fusion (LPBF). Although two distinct oxide films were created in the surface etching process (labeled CP-A and CP-B), no qualitative changes in microroughness were seen between the two conditions. CP-A possessed significantly less Ni at the surface (0.19 at. %) than the CP-B group (3.30 at. %), via x-ray photoelectron spectroscopy, alongside a concomitant shift in the O1 s peak presentation alluding to a greater formation of a Ni based oxide in the CP-B group. Our live dead staining revealed significant toxicity and reduced cellular attachment for the CP-B group, in addition to inducing more cell lysis (20.9 ± 5.1%), which was significantly increased when compared to CP-A (P < 0.01). Future practices of manufacturing NiTi scaffolds using LPBF should focus on producing surface films that are not only smooth, but free of cytotoxic Ni based oxides.