Mechanical and biological properties of Ti-(0-25 wt%)Nb alloys for biomedical implants application

Binary titanium-niobium (Ti-Nb) alloys have recently been attracted due to low Young's moduli and non-toxic properties. This study explores the influence of low Nb content (0-25 wt%) on the comprehensive parameters of tensile stress-strain relationships (ultimate strength (σ_UTS), yield strength (σ_0.2) and elastic modulus (E)), surfaces properties (Vickers microhardness, surface roughness (R _a), water contact angle (WCA), X-ray diffraction (XRD) and scanning electron microscopy (SEM)), corrosion resistance (in artificial saliva and lactic acid) and biological properties (cytotoxicity and alkaline phosphatase activity of MC3T3-E1 pre-osteoblasts) of Ti-xNb alloys (x = 5, 10, 15, 20 and 25 wt%), with using commercially pure grade 2 titanium (cp-Ti) as control. XRD results shown that all the Ti-xNb alloys comprised α + β Ti alloy phases, such that the β phase increased correspondingly with the increased amount of Nb in the alloy, as well as the reduction of E (69-87 GPa). Except Ti-5Nb, all other Ti-xNb alloys showed a significantly higher hardness, increased σ_UTS and σ_0.2, and decreased WCA compared with cp-Ti. No corrosion was detected on Ti-xNb alloys and cp-Ti in artificial saliva and lactic acid solutions. The cytotoxicity of Ti-xNb alloys was comparable to that of cp-Ti in MC3T3-E1 pre-osteoblasts without interference from differentiation behaviour, but the proliferation rate of the Ti-5Nb alloy was lower than other groups. In overall, binary Ti-(10-25 wt%)Nb alloys are promising candidate for orthopaedic and dental implants due to their improved mechanical properties and comparable biological performance, while Ti-5Nb should be used with caution.