Comprehensive Characterization of Titania Nanotubes Fabricated on Ti–Nb Alloys: Surface Topography, Structure, Physicomechanical Behavior, and a Cell Culture Assay

Abstract

In this study, hybrid composites based on β-alloy Ti−xNb and oxide nanotubes (NTs) have been successfully prepared. NTs of different sizes were grown on Ti−Nb substrates with different Nb contents (5, 25, and 50 wt %) via electrochemical anodization at 30 and 60 V. Scanning electron microscopy imaging revealed that vertically aligned nanotubular structures form on the surface of Ti−Nb alloy substrates and influence Nb content in alloys based on NT length. X-ray diffraction analysis confirmed the formation of the anodized TiO 2 layer and revealed several phases as the Nb content increased, starting with α′ for low Nb content (5 wt %), the martensite α″ for intermediate Nb content (25 wt %), and the β phase for the highest Nb content (50 wt %). Nanoindentation testing was used to evaluate the changes in mechanical properties of oxide NTs grown on Ti−Nb alloys with different compositions. NT arrays showed wide variations in Young's modulus and hardness depending upon the anodization voltage and the Nb content. The hardness and Young's modulus strongly correlated with NT morphology and structure. The highly dense morphology formed at a lower anodization voltage results in increased elastic modulus and hardness values compared with the surfaces prepared at higher anodization voltages. The nanostructurization of Ti−Nb surface substrates favored improved surface properties for the enhanced adhesion and proliferation of human mesenchymal stem cells (hMSCs). In vitro adhesion, spreading, and proliferation of hMSCs revealed the improved surface properties of the NTs prepared at an anodization voltage of 30 V compared with the NTs prepared at 60 V. Thus it can be concluded that NTs with diameters of ∼50 nm (at 30 V) are more favorable for cell adhesion and growth compared with NTs with diameters of 80 ± 20 nm (at 60 V). The surfaces of Ti−25Nb substrates anodized at 30 V promoted enhanced cell growth, as the further increase in Nb content in Ti−Nb substrate (Ti−50Nb) led to reduced cell proliferation. The application of NTs on Ti−Nb substrates leads to significant reductions in mechanical properties compared with those on the Ti−Nb alloy and improves cell adhesion and proliferation, which is vitally important for successful application in regenerative medicine.

Biofunctional magnesium-coated Ti6Al4V scaffolds promote autophagy-dependent apoptosis in osteosarcoma by activating the AMPK/mTOR/ULK1 signaling pathway

“…As a classic type of orthopedic implant, Ti6Al4V prostheses are widely used for the treatment of large bone defects. Although many other titanium alloys, such as Ti–Nb alloys [ 33 ], exhibit excellent mechanical properties and biocompatibility, Ti6Al4V remains indispensable for clinical applications and bone tissue engineering [ 34 ]. In recent years, porous Ti6Al4V scaffolds have attracted more attention due to their low overall modulus of elasticity, excellent mechanical properties, and good ingrowth of new bone [ 35 ].…”

Evolution of anodised titanium for implant applications

“…In Ti alloys, Renjie et al [294] proposed that the compaction/reduction of the α-phase and/or increase in the amount of the β-phase was the most important factor in promoting the mechanical biocompatibility of the surface. Recently, Chernozem et al [296] reported the anodic deposition of TNTs on β-alloy Ti-xNb hybrid composites (x ¼ 5, 25 or 50) and it was observed that there was a significant increase in β-phase elements in the alloy leading to an increase in the surface's elastic modulus after anodisation. The surface load-deformation behaviour of TNTs on Ti-50Nb was reduced by approximately 17% when compared to TNTs structure on Ti-Nb composites with lower wt% Nb and by approximately 23% when compared to cp-T [296].…”

“…Recently, Chernozem et al [296] reported the anodic deposition of TNTs on β-alloy Ti-xNb hybrid composites (x ¼ 5, 25 or 50) and it was observed that there was a significant increase in β-phase elements in the alloy leading to an increase in the surface's elastic modulus after anodisation. The surface load-deformation behaviour of TNTs on Ti-50Nb was reduced by approximately 17% when compared to TNTs structure on Ti-Nb composites with lower wt% Nb and by approximately 23% when compared to cp-T [296]. Regarding Young's modulus, the value obtained for the β-alloy Ti-xNb hybrid composites coated with TNTs was approximately the same as that of bone (ca.…”

“…Regarding Young's modulus, the value obtained for the β-alloy Ti-xNb hybrid composites coated with TNTs was approximately the same as that of bone (ca. 20–30 GPa [ 265 , 292 ]), suggesting that the nanostructured anodic surface has a beneficial effect and could represent a possible solution to the mechanical mismatch between bone and implant materials [ 296 ]. Since anodically grown TNTs on the proposed hybrid composite have reduced length, Chernozem et al.…”

“…Nanostructured films comprised of concurrent regions of tubes and laminar structures have not been documented among the highly promising properties and characteristics of anodised titanium today. In Ti-alloying, the biocompatible beta alloys made up of non-toxic elements (Nb, Ta, and Mo) have outstanding mechanical properties and corrosion resistance [ 211 , 296 , 298 ], making the β-phase titanium alloys as good candidates for replacing pure Ti and Ti-Al-V alloys in biomedical applications [ 297 ], but to validate their clinical translation, more research is required on these topics. Henceforth, this review envisioned that the trend of research for anodised titanium in the future should focus on substrate pre-processing and have more variety of Ti-substrates alloyed with β-elements tested and then anodised to broaden the functionality of the anodised titanium for implant coatings.…”