Improvement of biocompatibility of NiTi alloy by a cathode corrosion protection technique

NiTi合金具有独特的、优异的力学性能，如超弹性、形状存储特性、高耐磨性等。我们通过阴极防腐技术设计了防止镍离子释放的合金，提高了合金的生物相容性。研究了黏附细胞对种植金属耐蚀性的影响。将L929成纤维细胞贴壁于金属表面，培养3d。然后用电感耦合等离子体分析仪测定溶解到培养基中的镍离子的浓度。为了达到上述目的，利用L929成纤维细胞和U937巨噬细胞对金属粉和金属镍腐蚀液进行了镍毒性试验，对于纯镍，镍离子浓度随细胞密度的增加而增加。对于NiTi合金，Ni离子的溶出量比纯Ni的小，但Ni离子浓度与晶胞密度之间存在显著的相关性。另一方面，当细胞蛋白用10%的福尔马林溶液固定时，溶解的镍离子浓度与活细胞的浓度相差很小，根据这一结果，种植金属的耐腐蚀性强烈地依赖于活的黏附细胞的存在。

The NiTi alloy shows a unique, excellent mechanical properties like super-elasticity, a shape storage characteristic, and high wear resistance, etc. We designed the prevention of Ni ion release of the alloy by a cathode corrosion proof technique, and the improvement of the biocompatibility. We studied on the affect of adhesive cells on the corrosion resistance of implant metal. L929 fibroblastic cells, which were adhered on the surface of the metals, were cultured for 3 days. Then, the concentration of the Ni ion, which dissolved to the cultured medium was measured with the ICP analyzer. The toxicity test on Ni was carried out by using the L929 fibroblast and the U937 macrophage for a metallic powder and the corrosive liquid of metal Ni to achieve the above-mentioned purpose.About pure Ni, the amount of Ni ion concentration was increased proportionally to the cell density. For NiTi alloy, the amount of dissolution of the Ni ion was slighter than that of pure Ni, but the correlation of the concentration of Ni ion and the cell density was significant. On the other hand, when the protein of the cell was fixed with 10% formaline solution, the dissolved Ni ion concentration was a small amount compered with that of the living cells.According to the results, it was suggested that the corrosion resistance of implant metal was strongly depended on the existence of the living adhesive cells.