Texture-Governed Cell Response to Severely Deformed Titanium

Abstract

The phenomenon of superior biological behavior observed in titanium processed by an unconventional severe plastic deformation method, that is, hydrostatic extrusion, has been described within the present study. In doing so, specimens varying significantly in the crystallographic orientation of grains, yet exhibiting comparable grain refinement, were meticulously investigated. The aim was to find the clear origin of enhanced biocompatibility of titanium-based materials, having microstructures scaled down to the submicron range. Texture, microstructure, and surface characteristics, that is, wettability, roughness, and chemical composition, were examined as well as protein adsorption tests and cell response studies were carried out. It has been concluded that, irrespective of surface properties and mean grain size, the (101̅ 0) crystallographic plane favors endothelial cell attachment on the surface of the severely deformed titanium. Interestingly, an enhanced albumin, fibronectin, and serum adsorption as well as clearly directional growth of the cells with preferentially oriented cell nuclei have been observed on the surfaces having (0001) planes exposed predominantly. Overall, the biological response of titanium fabricated by severe plastic deformation techniques is derived from the synergistic effect of surface irregularities, being the effect of refined microstructures, surface chemistry, and crystallographic orientation of grains rather than grain refinement itself.

Microstructure evolution of pure titanium during hydrostatic extrusion

“…Owing to its mechanical characteristics as well as excellent biocompatibility, titanium produced via multi-pass HE followed by rotary swaging could be potentially applied in medicine for orthopedic or dental implants [24]. In fact, the attractiveness of a material from the point of view of biomedical purposes has been demonstrated in its superior corrosion resistance [25], enhanced protein adsorption on the surface [26] as well as improved cell-material interactions [27]. As a great advantage of the multi-pass HE one may regard the possibility of the mechanical properties adjustment for a certain application of the final product by applying different process parameters such as reduction diameter, number of passes, operating pressures etc.…”

What is the impact of plastic deformation on cytocompatibility of biodegradable Zn–Mg alloys?

“…This observation may be related to a strong crystallographic texture, which is a characteristic phenomenon of plastically deformed materials. 30…”

“…In general, the extracts are a mixture of cell culture medium and metal ions, as described in our previous study. 14 Within the present article, for the sake of brevity, we call the harvested extracts simply “zinc extracts” even though for the Zn–0.8Mg alloy, they might contain some minute concentration of the alloying addition. Prior to cell-response investigations, three different concentrations of extracts upon serial dilution with cell culture medium were studied, i.e.…”

“…For a more extensive description of the EBSD-derived parameters, readers are encouraged to reach out to e.g., our previous reports. 10,30,31 Materials Advances Paper…”

“…T1 relaxometry, a special mode of diamond-based quantum sensing whose principles can be found elsewhere, 13 has been successfully applied to check the nanoscale impact of zinc ions on endothelial cells. 14 It has been revealed that Zn 2+ released from biodegradable samples induces the intracellular formation of free radicals and that the overload of zinc ions in the cell environment results in the excessive production of reactive oxygen/nitrogen species and cell death. In biomaterial studies, T1 relaxometry has also been used to reveal whether free radicals are generated in lung epithelial cells exposed to nickel, titanium, and nitinol.…”