Effect of surface modification methods on 3D-printed NiTi alloys for cardiovascular applications

Laser powder bed fusion (LPBF) has emerged as a promising additive manufacturing technique to produce complex and custom-shaped NiTi devices, but precise control and characterization of the post-printing processing parameters are still required to achieve optimal surface properties and allow expanding the use of 3D-printed NiTi in cardiovascular applications. This work studies the effect of different surface post-processing techniques, including chemical etching, electropolishing and combinations of the two, on the surface properties and biological response of NiTi parts manufactured by LPBF. The different surface treatments resulted in changes in the roughness, wettability and corrosion resistance, which were closely correlated with the nature, microstructure and thickness of the surface oxide layers that form in each case. Furthermore, the biocompatibility of the different NiTi surfaces to human endothelial and smooth muscle cells, the main components of cardiovascular tissue, were also assessed. Interestingly, while the different surfaces showed high biocompatibility in terms of viability and proliferation, cells showed distinct morphology and orientation, as well as inflammatory response (IL-6). Finally, differences were also observed in the hemocompatibility of the 3D-printed NiTi surfaces to human blood. Overall, this work provides new insights for the wide use of additive manufacturing to develop personalized NiTi implants for cardiovascular applications.