Effects of anodizing parameters and heat treatment on nanotopographical features, bioactivity, and cell culture response of additively manufactured porous titanium

Abstract

Anodizing could be used for bio-functionalization of the surfaces of titanium alloys. In this study, we use anodizing for creating nanotubes on the surface of porous titanium alloy bone substitutes manufactured using selective laser melting. Different sets of anodizing parameters (voltage: 10 or 20V anodizing time: 30min to 3h) are used for anodizing porous titanium structures that were later heat treated at 500°C. The nanotopographical features are examined using electron microscopy while the bioactivity of anodized surfaces is measured using immersion tests in the simulated body fluid (SBF). Moreover, the effects of anodizing and heat treatment on the performance of one representative anodized porous titanium structures are evaluated using in vitro cell culture assays using human periosteum-derived cells (hPDCs). It has been shown that while anodizing with different anodizing parameters results in very different nanotopographical features, i.e. nanotubes in the range of 20 to 55nm, anodized surfaces have limited apatite-forming ability regardless of the applied anodizing parameters. The results of in vitro cell culture show that both anodizing, and thus generation of regular nanotopographical feature, and heat treatment improve the cell culture response of porous titanium. In particular, cell proliferation measured using metabolic activity and DNA content was improved for anodized and heat treated as well as for anodized but not heat-treated specimens. Heat treatment additionally improved the cell attachment of porous titanium surfaces and upregulated expression of osteogenic markers. Anodized but not heat-treated specimens showed some limited signs of upregulated expression of osteogenic markers. In conclusion, while varying the anodizing parameters creates different nanotube structure, it does not improve apatite-forming ability of porous titanium. However, both anodizing and heat treatment at 500°C improve the cell culture response of porous titanium.

The Influence of Selective Laser Melting (SLM) Process Parameters on In-Vitro Cell Response

“…The reported studies focused mainly on surface modification of solid and porous titanium scaffolds. For example, Yavari and coworkers [ 36 ] investigated the effect of anodizing parameters and heat treatment of SLM titanium discs and found that combination of both processes improves cell adhesion, proliferation and osteogenic differentiation. Wysocki and coworkers [ 37 ] found that chemical polishing of 3D porous titanium scaffolds fabricated by means of SLM yields lowers cell seeding efficiency but improves cell proliferation and scaffolds colonization.…”

Dynamic expression of SMAD3 is critical in�osteoblast differentiation of PDMCs

“…For example, bone loss in older people due to imbalances between osteoblast and osteoclast activitymay servea role in post-fracture mortality (11,12). In addition, appropriate osteoblast calcification or bone mineralization is essential for complete bone formation (13)(14)(15). The process of bone regeneration has the potential to treat defects in bone healing in patients with osteoporosis with bone fractures or abnormalities in osteogenesis (9,16,17).…”

Additively manufactured porous metallic biomaterials

“…160,161 For example, in the case of the titanium alloy Ti-6Al-4V processed with SLM, a very brittle phase (i.e., a 0 ) is often formed, which reduces the fatigue life of the resulting material. 162 Heat treatments alone 76,158,[163][164][165][166][167][168][169][170] as well as in combination with high pressures (e.g., in hot isostatic pressing 157,162,171 ) and surface treatments 162 could be used to both reduce the level of the residual stresses and to improve the microstructural features of the materials processed with EBM and SLM.…”

“…One therefore has to rely on chemical or electrochemical techniques that are capable of reaching the internal surfaces of the porous structure. Therefore, techniques such as dipping, 209 chemical surface treatments using acid and alkali solutions, 164,210,211 anodizing, 169,212 plasma electrolytic oxidation, 145,213 and electrophoretic deposition 214,215 have been usually used for such purposes.…”