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 (0-25wt%) on the comprehensive parameters of tensile stress-strain relationships (ultimate strength (sigma(UTS)), yield strength (sigma(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 25wt%), with using commercially pure grade 2 titanium (cp-Ti) as control. XRD results shown that all the Ti-xNb alloys comprised alpha + beta Ti alloy phases, such that the beta phase increased correspondingly with the increased amount of Nb in the alloy, as well as the reduction of E (69-87GPa). Except Ti-5Nb, all other Ti-xNb alloys showed a significantly higher hardness, increased sigma(UTS) and sigma(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.