可降解金属Mg-Nd-Zn-Zr镁合金的降解行为

背景：添加合金元素是改变镁合金微观结构和控制镁合金降解行为的有效方法。目的：探讨Mg-Nd-Zn-Zr镁合金体内外的降解行为。方法：①体外静态浸泡实验：在(37.0±0.5) ℃条件下，将Mg-Nd-Zn-Zr镁合金和纯镁各6个样品分别浸入 250 mL模拟体液中，浸泡过程中不搅拌振荡。静态浸泡第3，7，30天后从模拟体液中取出试样，扫描电镜及能谱分析分析Mg-Nd-Zn-Zr镁合金在模拟体液中的降解行为。②体内植入实验：在成年新西兰兔左侧股骨钻孔，实验组植入Mg-Nd-Zn-Zr镁合金，对照组植入钛合金，空白对照组不植入任何内植物。植入后1，2，4，8周，通过X射线观察内植物的位置及降解行为；植入后4，8周，通过扫描电镜观察Mg-Nd-Zn-Zr镁合金表面腐蚀产物，通过元素能谱分析腐蚀产物的成分，并计算材料降解速率。结果与结论：①Mg-Nd-Zn-Zr镁合金浸泡于模拟体液中不同时间点的降解速率均低于纯镁组；浸泡30 d后，沉积于Mg-Nd-Zn-Zr镁合金表面的腐蚀产物主要是氧、碳、钠、镁、钙、磷和氯，去除腐蚀产物后Mg-Nd-Zn-Zr镁合金和纯镁表面均有腐蚀坑，但Mg-Nd-Zn-Zr镁合金表面腐蚀坑体积更小，分布更均匀，表明Mg-Nd-Zn-Zr镁合金和纯镁存在不同的腐蚀形式。②Mg-Nd-Zn-Zr镁合金植入动物体内后随时间延长逐渐降解，材料表面腐蚀产物及成分类似于体外浸泡实验。

In vitro and in vivo degradation of Mg-Nd-Zn-Zr alloy

BACKGROUND: Alloying is a convenient and effective method to alter the microstructure and control the corrosion behavior of magnesium alloy.OBJECTIVE:To explore the in vitro and in vivo degradation of Mg-Nd-Zn-Zr alloy as a degradable medical biomaterial.METHODS: (1) In vitro static immersion test: The immersion tests were carried out at (37.0±0.5) ℃ in a thermostatic bath. Six Mg-Nd-Zn-Zr alloy samples and six pure magnesium samples were immersed in the    250 mL simulated body fluid and vibrated without agitation during immersion. After 3, 7 and 30 days static immersion, the samples were taken out from the simulated body fluid. Then the in vitro corrosion properties were evaluated using scanning electron microscope and energy dispersive spectrometer analysis. (2) In vivo animal experiment: After bone tunnel was established in the left femur of adult New Zealand rabbits, the Mg-Nd-Zn-Zr alloy rods were embedded in the Mg-Nd-Zn-Zr alloy group, titanium alloy rods were embedded in the titanium alloy group, and only bone tunnel was established in the sham-operated group. At 1, 2, 4, 8 weeks after implantation, an X-ray of the implanted region was taken to determine the location and the degradation behavior of Mg-Nd-Zn-Zr alloy. At 4, 8 weeks after implantation, the corrosion product and its element composition were observed using scanning electron microscope with an energy dispersive spectroscopy system.RESULTS AND CONCLUSION: (1) The static immersion test showed that Mg-Nd-Zn-Zr alloy degraded slower than pure magnesium at each time point. It was obvious that there was a corrosion layer on the surface of Mg-Nd-Zn-Zr alloy after 30 days immersion in the simulated body fluid. Energy dispersive spectroscopy analysis revealed that these particles were mainly composed of oxygen, carbon, sodium, magnesium, calcium, phosphate and chlorine. After the corrosion products were removed, corrosion pits could be clearly seen on the surface of Mg-Nd-Zn-Zr alloy and pure magnesium. However, the corrosion pits on the surface of Mg-Nd-Zn-Zr alloy were smaller and more even than those on the surface of pure magnesium. This shows that the degradation modes of the Mg-Nd-Zn-Zr alloy and pure magnesium are distinctly different. (2) After implanted into the animals, the Mg-Nd-Zn-Zr alloy gradually degraded with time. And the corrosion products and ingredients were similar to the in vitro results.