Study On Biocompatibility And Osseointegration Capacity Of Novel Low Elastic Modulus Titanium Alloy TiNbZrTaSi

Objective:The well biocompatibility of titanium alloys makes them the most commonly used biomedical metallic material. However, the problems of relatively high elastic modulus and low binding force between bone and implant still exist. South China University of Technology has developed a novel titanium alloy with nominal compositions of(Ti-35Nb-7Zr-5Ta)98Si2, which has been designed by d-electron alloy design theory and fabricated by spark plasma sintering(SPS). The new alloy exhibited low elastic modulus, high strength, ultra-large ductility and ultrafine-grained structure. Ti-35Nb-7Zr-5Ta alloy system had been proved to possess well biocompatibility and low elastic modulus. Si could promote grain refinement and glass-formation, and exhibited good biocompatibility.(Ti-35Nb-7Zr-5Ta)98Si2 exerts lower elastic modulus to that of Ti-6Al-4V. In this study, we evaluated corrosion resistance, biocompatibility, bioactivity and osseointegration capacity of the new titanium alloy, in order to discuss its biosecurity and applied value in orthopaedic surgery, and provide theoretical basis for its application. Methods:(1)Corrosion resistance evaluation: alloy samples have been soaked in normal saline for 1, 2, 3, 5, 7 days. Corrosion of materials was detected at different time points in PH value, weightlessness rate and surface morphology change under scanning electron microscopy.(2)Biocompatibility evaluation: leach liquor was prepared to culture L-929 cells. Morphology observation and MTT test were used for the assessment of cytotoxicity. Acute systemic toxicity was evaluated according to material toxicity evaluation standard. Skin/intracutaneous sensitization test results was evaluated according to skin/intracutaneous reaction scoring system and reaction types. Bone implant test was evaluated by HE staining.(3)Bioactivity evaluation: MC3T3-E1 cells were cultured together with the alloy samples. Cell count with acridine orange staining was performed to assess adhesive capacity. Cell morphology was observed under scanning electron microscopy. Apoptosis rate was detected by Annexin V-FITC method. IL-6 secretion was detected by ELISA. ALP secretion and biomineralization were detected to evaluate the early and terminal differentiation of osteoblast cells.(4)Osseointegration capacity evaluation: six rabbits were implanted Ti-6Al-4V and(Ti-35Nb-7Zr-5Ta)98Si2 in their femurs. After three months, general material-bone interface condition was observed by X-ray. Masson staining and toluidine blue staining were performed to evaluate tissue reaction of material-bone interface and bone contact ratio was calculated. Push-out test was to detect the binding strength between bone and implanted samples. Results:(1)No change was detected in PH and weight during immersion period. Surface morphology observation showed no evidence of corrosion.(2)Cell morphology and MTT test results indicated the alloy has no cytotoxicity. No toxic reaction was detected in acute systemic toxicity test. The material exerted no allergic reaction in skin/intracutaneous sensitization test. The implanted material did not cause tissue necrosis and inflammation.(3)Osteoblast cells were adherent to the novel alloy well and exerted good growth state, as well as that adherent to Ti-6Al-4V. The alloy did not increase the apoptosis rate and secretion of IL-6. ALP secretion was not higher when osteoblast cells were cultured together with Ti Nb Zr Ta Si alloy, compared with negative control and Ti-6Al-4V. The new alloy increased biomineralization as well as Ti-6Al-4V.(4)No redness, fester or tissue necrosis was found aside implanted materials. The implant was bound tightly to bone tissue and bone-formation was observed. Binding force and bone contact ratio(BCR) of(Ti-35Nb-7Zr-5Ta)98Si2 were higher than those of Ti-6Al-4V. Conclusion:(1)The novel titanium alloy(Ti-35Nb-7Zr-5Ta)98Si2 with low elastic modulus and ultrafine-grained structure exhibited good biocompatibility.(2)This alloy exerted well corrosion resistance, bioactivity and osseointegration capacity, which make it a perfect material for orthopaedic surgery.