Characterization, corrosion behavior, cellular response and in vivo bone tissue compatibility of titanium-niobium alloy with low Young's modulus.

β-Type titanium alloys with a low elastic modulus are a potential strategy to enhance bone remodeling and to mitigate the concern over the risks of osteanabrosis and bone resorption caused by stress shielding, when used to substitute irreversibly impaired hard tissue. Hence, in this study, a Ti-45Nb alloy with low Young's modulus and high strength was developed, and microstructure, mechanical properties, corrosion behaviors, cytocompatibility and in vivo osteo-compatibility of the alloy were systematically investigated for the first time. The results of mechanical tests showed that Young's modulus of the Ti-Nb alloy was reduced to about 64.3GPa (close to human cortical bone) accompanied with higher tensile strength and hardness compared with those of pure Ti. Importantly, the Ti-Nb alloy exhibited superior corrosion resistance to Ti in different solutions including SBF, MAS and FAAS (MAS containing NaF) media. In addition, the Ti-Nb alloy produced no deleterious effect to L929 and MG-63 cells, and cells performed excellent cell attachment onto Ti-Nb surface, indicating a good in vitro cytocompatibility. In vivo evaluations indicated that Ti-Nb had comparable bone tissue compatibility to Ti determined from micro-CT and histological evaluations. The Ti-Nb alloy with an elasticity close to human bone, thus, could be suitable for orthopedic/dental applications.

Bai Y ，Deng Y ，Zheng Y ，Li Y ，Zhang R ，Lv Y ，Zhao Q ，Wei S ... -  《-》

The bone tissue compatibility of a new Ti-Nb-Sn alloy with a low Young's modulus.

A Ti-Nb-Sn alloy was developed as a new β-type titanium alloy which had a low Young's modulus and high strength. The Young's modulus of the Ti-Nb-Sn alloy was reduced to about 45 GPa by cold rolling, much closer to human cortical bone (10-30 GPa) than that of Ti-6Al-4V alloy (110 GPa) and other β-type titanium alloys developed for biomedical applications. The tensile strength of the Ti-Nb-Sn alloy was increased to a level greater than that of Ti-6Al-4V alloy by heat treatment after severe cold rolling. In this study the cytotoxicity of Ti-25Nb-11Sn alloy was evaluated in direct contact cell culture tests using metal disks and the bone tissue compatibility - examined using metal rods inserted into the medullary canal of rabbit femurs. The remarkable findings were that: (1) there were no significant differences in the relative growth ratio and relative absorbance ratio between cells grown with the Ti-Nb-Sn alloy, Ti-6Al-4V alloy and CP-Ti in direct contact cell culture tests; (2) there were no significant differences in the load at failure between the Ti-Nb-Sn alloy and Ti-6Al-4V alloy in pull-out metal rods tests; (3) there were no significant differences in new bone formation around metal rods between the Ti-Nb-Sn alloy and Ti-6Al-4V alloy in histological evaluations. The new Ti-Nb-Sn alloy with an elasticity closer to that of human bone is thus considered to be bioinert while also having a high degree of bone compatibility similar to that of Ti-6Al-4V alloy.

Miura K ，Yamada N ，Hanada S ，Jung TK ，Itoi E ... -  《-》

Effects of elastic intramedullary nails composed of low Young's modulus Ti-Nb-Sn alloy on healing of tibial osteotomies in rabbits.

Intramedullary nailing is widely performed for internal fixation of fractures. The applicable elasticity of materials composing intramedullary nails remains unclear. The present study aimed to evaluate the effects of the elastic property of β-type titanium alloy nails on fracture healing compared with conventional Ti-6Al-4V alloy nails using a rabbit tibial osteotomy model. Two types of intramedullary nails composed of β-type Ti-Nb-Sn alloy (Young's modulus: 37 GPa) or Ti-6Al-4V alloy (Young's modulus: 110 GPa) were used for osteotomy fixation in the tibiae of rabbits. At 4, 8, and 16 weeks postoperatively, microcomputed tomography (micro-CT) and three-point bending tests were performed. Micro-CT images showed that the callus volume was significantly larger in the Ti-Nb-Sn alloy group at 4 and 8 weeks. The callus bone mineral density did not differ at each time point. In mechanical testing, the maximum load was significantly higher at all time points in the Ti-Nb-Sn alloy group. Taken together, the elastic intramedullary nails composed of Ti-Nb-Sn alloy improved the mechanical properties of the bone healing site from the early phase to the remodeling phase. Adequate Young's modulus of the Ti-Nb-Sn alloy enhanced fracture union and bone strength restoration. The Ti-Nb-Sn alloy is a promising biomaterial for fracture fixation devices. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 700-707, 2019.

Kogure A ，Mori Y ，Tanaka H ，Kamimura M ，Masahashi N ，Hanada S ，Itoi E ... -  《-》

Screening on binary Zr-1X (X = Ti, Nb, Mo, Cu, Au, Pd, Ag, Ru, Hf and Bi) alloys with good in vitro cytocompatibility and magnetic resonance imaging compatibility.

In this study, the microstructures, mechanical properties, corrosion behaviors, in vitro cytocompatibility and magnetic susceptibility of Zr-1X alloys with various alloying elements, including Ti, Nb, Mo, Cu, Au, Pd, Ag, Ru, Hf and Bi, were systematically investigated to explore their potential use in biomedical applications. The experimental results indicated that annealed Zr-1X alloys consisted entirely or primarily of α phase. The alloying elements significantly increased the strength and hardness of pure Zr and had a relatively slight influence on elastic modulus. Ru was the most effective enhancing element and Zr-1Ru alloy had the largest elongation. The results of electrochemical corrosion indicated that adding various elements to Zr improved its corrosion resistance, as indicated by the reduced corrosion current density. The extracts of the studied Zr-1X alloys produced no significant deleterious effects on osteoblast-like cells (MG 63), indicating good in vitro cytocompatibility. All except for Zr-1Ag alloy showed decreased magnetic susceptibility compared to pure Zr, and Zr-1Ru alloy had the lowest magnetic susceptibility value, being comparable to that of α' phase Zr-Mo alloy and Zr-Nb alloy and far lower than that of Co-Cr alloy and Ti-6Al-4V alloy. Among the experimental Zr-1X alloys, Zr-1Ru alloy possessing high strength coupled with good ductility, good in vitro cytocompatibility and low magnetic susceptibility may be a good candidate alloy for medical devices within a magnetic resonance imaging environment.

Zhou FY ，Qiu KJ ，Li HF ，Huang T ，Wang BL ，Li L ，Zheng YF ... -  《-》

Optimizing the cell compatibility and mechanical properties in TiZrNbTa medium-entropy alloy/β-Ti composites through phase transformation.

Medium-entropy alloys (MEAs) typically exhibit outstanding mechanical properties, but their high Young's modulus results in restricted clinical applications. Mismatched Young's modulus between implant materials and human bones can lead to "stress shielding" effects, leading to implant failure. In contrast, β-Ti alloys demonstrate a lower Young's modulus compared to MEAs, albeit with lower strength. In the present study, based on the bimodal grain size distribution (BGSD) strategy, a series of high-performance TiZrNbTa/Ti composites are obtained by combining TiZrNbTa MEA powders with nano-scale grain sizes and commercially pure Ti (CP-Ti) powders with micro-scale grain sizes. Concurrently, Zr, Nb, and Ta that are β-Ti stabilizer elements diffuse into Ti, inducing an isomorphous transformation in Ti from the high Young's modulus α-Ti phase to the low Young's modulus β-Ti phase at room temperature, optimizing the mechanical biocompatibility. The TiZrNbTa/β-Ti composite demonstrates a yield strength of 1490 ± 83 MPa, ductility of 20.7 % ± 2.9 %, and Young's modulus of 87.6 ± 1.6 GPa. Notably, the yield strength of the TiZrNbTa/β-Ti composite surpasses that of sintered CP-Ti by 2.6-fold, and its ductility outperforms TiZrNbTa MEA by 2.3-fold. The Young's modulus of the TiZrNbTa/β-Ti composite is reduced by 28 % and 36 % compared to sintered CP-Ti and TiZrNbTa MEA, respectively. Additionally, it demonstrates superior biocompatibility compared to CP-Ti plate, sintered CP-Ti, and TiZrNbTa MEA. With a good combination of mechanical properties and biocompatibility, the TiZrNbTa/β-Ti composite exhibits significant potential for clinical applications as metallic biomaterials. STATEMENT OF SIGNIFICANCE: This work combines TiZrNbTa MEA with nano-grains and commercially pure Ti with micro-grains to fabricate a TiZrNbTa/β-Ti composite with bimodal grain-size, which achieves a yield strength of 1490 ± 83 MPa and a ductility of 20.7 % ± 2.9 %. Adhering to the ISO 10993-5 standard, the TiZrNbTa/β-Ti composite qualifies as a non-cytotoxic material, achieving a Class 0 cytotoxicity rating and demonstrating outstanding biocompatibility akin to commercially pure Ti. Drawing on element diffusion, Zr, Nb, and Ta serve not only as solvent atoms to achieve solid-solution strengthening but also as stabilizers for the transformation of the β-Ti crystal structure. This work offers a novel avenue for designing advanced biomedical Ti alloys with elevated strength and plasticity alongside a reduced Young's modulus.

Du P ，Cui Z ，Xiang T ，Li Y ，Zhang L ，Cai Z ，Zhao M ，Xie G ... -  《-》