【作者】 刘丽君；

【导师】 王鲁宁；

【作者基本信息】 北京科技大学 ， 材料科学与工程， 2021， 博士

【摘要】 锌及锌合金由于具有良好的生物相容性和可降解性而成为新一代可降解血管支架材料。但是,由于缺乏严格的测试标准,锌及锌合金的降解机理尚未达成共识。液体环境是影响金属材料腐蚀行为的一个重要因素。体外测试时,模拟体液中的无机盐及有机成分(如蛋白质)的差异会使材料表现出不同的腐蚀行为。因此,围绕液体成分对腐蚀的影响这一问题,利用电化学测试和浸泡实验研究了纯锌在不同模拟体液中的腐蚀行为,并研究了腐蚀对力学性能的影响。(1)研究了模拟体液中Cl-、HCO3-、HPO42-、SO42-和蛋白质(牛血清白蛋白)对纯锌腐蚀的影响。结果表明,阴离子会使纯锌发生不同程度的腐蚀,表面出现无机盐腐蚀产物,蛋白质则会明显降低纯锌的腐蚀速率;(2)重点研究了蛋白质浓度对纯锌腐蚀行为的影响。在磷酸盐缓冲液中,0.5 g L-1的蛋白质先是减缓纯锌的腐蚀,之后又使其加速,而2 gL-1的蛋白质会明显减少磷酸盐腐蚀产物的沉积,并在浸泡初期加速腐蚀;(3)研究了纯锌在模拟血浆(含有60g L-1蛋白质)中的腐蚀行为。结果发现,纯锌的腐蚀行为与以往报道的结果有所不同。在模拟血浆中,纯锌发生均匀腐蚀,腐蚀产物为蛋白质和ZnO/Zn(OH)2的复合物,通过失重计算所得的腐蚀速率约为16.52±0.21μmy-1,接近血管支架材料的标准;(4)研究了腐蚀对力学性能的影响。在模拟体液中,纯锌表面出现严重的局部腐蚀,纯锌的屈服强度、抗拉强度分别从59.31±1.33 MPa、89.93±0.62 MPa 降低至 46.35±2.21 MPa、79.11±1.01 MPa,尤其是延伸率从 81.33±3.51%大幅度降低至47.04±4.09%;在模拟血浆中,蛋白质减缓了纯锌的局部腐蚀,屈服强度、抗拉强度和延伸率随浸泡时间缓慢下降至49.63±5.01 MPa、85.69±0.78 MPa、57.17±2.75%。6个月后,纯锌的延伸率仍然高于对支架材料延伸率的要求。体外测试时,纯锌在不同的模拟体液中表现出不同的腐蚀行为。蛋白质促使纯锌发生均匀腐蚀,减小腐蚀速率,减少腐蚀产物沉积,还会进一步影响其力学行为。因此,建议在体外测试时,考虑蛋白质对纯锌腐蚀行为的影响,以便对材料在体内的腐蚀行为及力学行为做出合理的预测。更多还原

【Abstract】 Zinc(Zn)and its alloys have become a new generation of biodegradable vascular scaffolds due to their good biocompatibility and biodegradability.However,due to lacking of strict testing standards,consensus on the degradation mechanism of Zn and its alloys has not been reached.Physiological environment plays an important role in the corrosion of metals.When tested in vitro,differences of inorganic salts and organic components(such as proteins)in simulated body fluids could alter the corrosion behavior of stent materials.Therefore,this work focused on the influences of solution compositions on the corrosion behavior of pure Zn.Electrochemical measurements and immersion tests were utilized to evaluate the pure Zn corrosion in different solutions.(1)The effects of Cl-、HCO3-、HPO42-、SO42-and proteins(bovine serum albumin)in simulated body fluids on the corrosion of pure Zn were studied.Results showed that anion leads to the corrosion of pure Zn to some extent,and inorganic salt formed on the surface as corrosion products.However,protein can significantly reduce the corrosion of pure Zn.(2)The effect of protein concentrations on the corrosion behavior of pure Zn was studied.In the phosphate buffered saline,protein with 0.5 g L-1 firstly slowed down the corrosion of pure Zn and then accelerated it.Protein with 2 g L-1 significantly reduced deposition of phosphates on the surface and accelerated the corrosion at the initial stage of immersion.(3)The corrosion behavior of pure Zn in simulated plasma containing 60 g L-1 protein was studied.The results showed that the corrosion behavior of pure Zn was different from the results reported previously.In the simulated plasma,pure Zn encountered uniform corrosion,and the corrosion product was a complex of protein and ZnO/Zn(OH)2.The corrosion rate of pure Zn after 28 d immersion was about 16.52±0.21μm y-1,which is close to the standard of vascular scaffold materials.(4)The effect of corrosion on mechanical properties was studied.In the simulated body fluid,serious localized corrosion was observed on the pure Zn surface.And the yield strength and ultimate tensile strength were decreased from 59.31±1.33 MPa,89.93±0.62 MPa to 46.35±2.21 MPa,79.11±1.01 MPa,the elongation was reduced greatly from 81.33±3.51%to 47.04±4.09%.In the simulated plasma,the presence of proteins alleviated the localized corrosion of pure Zn.The mechanical parameters decreased slowly with the immersion time to 49.63±5.01 MPa、85.69±0.78 MPa、57.17±2.75%.After 6 months,the elongation of pure Zn was still higher than the requirement of scaffold materials.In the in vitro test,pure Zn showed different corrosion behavior in different simulated body fluids.Protein causes uniform corrosion of pure Zn and reduces the corrosion rate as well as the deposition of corrosion products.The mechanical behavior was also related to the corrosion in different solutions.Therefore,it is suggested that the influence of proteins on the corrosion behavior of pure Zn should be considered in the in vitro test,so as to make a reasonable prediction on the corrosion behavior and mechanical behavior of materials in vivo.更多还原