生理环境中NiTi记忆合金腐蚀释放Ni离子的研究

Study on the NiTi alloy corrosion releasing Ni ion in the different simulate physiological environment

目的研究pH值、Cl-浓度对医用NiTi形状记忆合金在不同模拟生理环境中的Ni2+腐蚀释放动力学过程的影响,同时对NiTi形状记忆合金Ni2+腐蚀释放机理进行分析探讨。方法在0.9%NaCl生理盐水、Hank’s模拟体液、Tyrode’s模拟血液三种模拟生理液中,pH值分别为2、5、8和10,恒温(37±1)℃下,进行静态挂片腐蚀试验,然后用最小二乘原理拟合试验曲线。结果Ni Ti形状记忆合金在Tyrode’s模拟血液中的Ni离子释放量最大,Hank’s模拟体液中次之,0.9%NaCl生理盐水中较低,Ni离子释放在前7天内呈现较快速度,之后趋于平缓;且Ni离子释放量随pH和Cl-的增大而增加。结论在Cl-浓度为正常条件0.14mol/L下,当体液在2≤pH≤10范围内波动时,NiTi记忆合金中Ni2+的腐蚀释放量在约3年内达不到Ni致敏的最低极限量,孔蚀是NiTi形状记忆合金在生理环境中主要的腐蚀机理。

Objective Study on the affection of pH value, and Clion concentration to medical NiTi alloy releases the eliciting toxic and allergic Ni^2＋ ion on account of corrosion in the different simulate physiological environment. Simultaneously, it was searched for and analyzed the releasing mechanism to NiTi alloy allergic Ni^2＋ ion. Methods In three simulated body fluids （37±1）℃ which are the 0. 9% Nacl solution ,and Hanks solution and Tyrode＇s solution at pH 2-10, the samples were immersed, and otherwise, in Nacl physiological solutions with six C1 ion concentrations for the same period respectively. In final, the curves and data were fit using a mathematics way. Results The resuits showed that different physiological environments, pH value, Cl^- ion concentration and immersion period, respectively, had a significantly influence on the release amount of Ni ion. The amount of Ni release increased with the reducing of pH value. The amount of Ni ion release in Tyrode＇s simulated blood solution was higher than that in both Hanks and 0.9% Nacl physiological solutions, but the amount of Ni ion released from NiTi alloy in tyrode＇s simulated blood solution was well below the critical value necessary to induce allergy. Conclusion NiTi alloy as implants in vitro is safe in three years at 2≤pH≤10 with normal Cl^- ion concentration because the amount of Ni release is low below the standard. On the other hand, the higher Cl^- ion concentration corresponded to the higher Ni ion release. The corrosive mechanism of NiTi alloy is pitting corrosion in physiological environments.