Mg-Gd-Y-Zn-Zr合金腐蚀降解行为与生物性能研究

发布时间：2018-10-23 20:27

【摘要】：作为可降解生物金属材料,镁及镁合金与自然骨的抗拉强度、抗压强度、弹性模量和密度均比较相似,力学相容性以及生物相容性好,因此,镁及镁合金逐渐成为最具有开发潜力的可降解生物材料。本文采用热挤压变形和时效处理等工艺方法制备生物Mg-8Gd-4Y-xZn-0.5Zr(x=1,2 wt%)合金,利用电化学腐蚀实验和浸泡腐蚀降解实验,对比研究不同状态合金在Hank's模拟体液中的腐蚀降解速率;通过采用OM, SEM,XRD等技术手段对腐蚀后的试样表面及腐蚀产物形貌进行分析,探究其腐蚀类型和腐蚀程度及腐蚀机理;借助MTT法考察不同Mg-8Gd-4Y-xZn(x=0, 1,2, 3 wt%)合金对小鼠预成骨细胞(MC3T3-E1)、人骨肉瘤细胞(Saos-2)、骨髓间充质干细胞(hTMSC)的细胞毒性。得到以下结论:(1)时效处理后Mg-8Gd-4Y-1Zn-0.5Zr合金析氢量从28 ml降至20 ml,腐蚀速率从7.247 mm/a 降至 5.691 mm/a,而 Mg-8Gd-4Y-2Zn-0.5Zr 的析氢量从 30 ml 降至 23ml,腐蚀速率从8.748 mm/a降至7.164 mm/a。由此可见,时效处理减轻了合金的腐蚀。(2)SEM形貌显示腐蚀产物均为片层状龟裂结构,大部分比较平整,出现了典型的点蚀坑。时效过程中,合金发生了静态回复,空位数量、位错密度降低,残余应力得以释放,有利于合金耐蚀性能的提高。XRD结果表明,腐蚀产物主要由Mg(OH)2组成,并掺杂有MgO、Mg3(PO4)2、Ca(PO3)2等物质。时效后合金的开路电位、极化曲线趋于向正移动,腐蚀电流减小,高频容抗弧也随之增大,合金耐蚀性都有所增强,腐蚀速率有所降低。(3)合金在SBF溶液腐蚀过程中,合金表面会发生反应析出大量的H2,随着溶液不断的被碱化,浸泡10 h后溶液pH达到10.5左右。挤压态合金在SBF溶液中的腐蚀速度高于时效态合金的腐蚀速度。试样的离子浓度在SBF和培养液中规律基本一致,在时效态合金中的析出量较挤压态合金的低。(4) MC3T3-E1 细胞、hTMSC 细胞在 Mg-8Gd-4Y-xZn(x=0, 1,2, 3 wt%)浸提液中培养1天和3天后,当浸提液浓度为100 %时,合金的细胞毒性均属于无毒或微毒范畴,当浸提液浓度为50 %和25 %时,细胞增殖率达到80 %以上,细胞毒性均为0级。证明合金的生物性良好,适宜用作生物医用植入材料。(5) MC3T3-E1细胞和hTMSC细胞经过25%浸提液培养24 h后,大部分细胞呈梭形,几乎无任何异常状态出现。随着Zn含量的增加,细胞的增殖呈现出先增加后降低的趋势。扫描电镜观察hTMSC细胞的生长状态,细胞多为长梭形,时效态合金浸提液培养过后的伸展状态良好,并且细胞长出伪足与临近细胞交联呈网状。
[Abstract]:As biodegradable biomaterials, magnesium and magnesium alloys have similar tensile strength, compressive strength, elastic modulus and density with natural bone. Magnesium and magnesium alloys are becoming the most promising biodegradable biomaterials. In this paper, the biological Mg-8Gd-4Y-xZn-0.5Zr (x1 + 2 wt%) alloy was prepared by hot extrusion deformation and aging treatment. The corrosion degradation rate of different state alloys in simulated body fluid of Hank's was studied comparatively by electrochemical corrosion test and immersion corrosion degradation experiment. The corrosion types, corrosion degree and corrosion mechanism of the samples after corrosion were analyzed by means of OM, SEM,XRD and other techniques. The cytotoxicity of different Mg-8Gd-4Y-xZn (xn0, 1, 2, 3 wt%) alloys to mouse preosteoblasts (MC3T3-E1), human osteosarcoma cells (Saos-2) and bone marrow mesenchymal stem cells (hTMSC) was investigated by MTT assay. The following conclusions are obtained: (1) after aging treatment, the hydrogen evolution rate of Mg-8Gd-4Y-1Zn-0.5Zr alloy decreases from 28 ml to 20 ml, from 7.247 mm/a to 5.691 mm/a, while that of Mg-8Gd-4Y-2Zn-0.5Zr decreases from 30 ml to 23 ml, and the corrosion rate decreases from 8.748 mm/a to 7.164 mm/a.. It can be seen that aging treatment alleviates the corrosion of the alloy. (2) SEM morphology shows that the corrosion products are lamellar crack structure, most of them are flat, and typical pitting pits appear. During aging, static recovery occurs, the number of vacancies and dislocation density decrease, and the residual stress is released. The XRD results show that the corrosion products are mainly composed of Mg (OH) _ 2 and doped with MgO,Mg3 (PO4) _ 2Ca (PO3) _ 2. After aging, the open circuit potential and polarization curve tend to move positively, the corrosion current decreases, the high frequency capacitance arc resistance increases, the corrosion resistance of the alloy increases and the corrosion rate decreases. (3) during the corrosion process of SBF solution, the corrosion resistance of the alloy increases. A large amount of H _ 2 was precipitated on the surface of the alloy, and the pH of the solution reached about 10.5 after 10 h immersion with the solution continuously alkalized. The corrosion rate of extruded alloy in SBF solution is higher than that of aged alloy. The ion concentration of the sample was basically consistent with that of the culture medium, and the precipitation amount in the aging alloy was lower than that in the extruded alloy. (4) MC3T3-E1 cells and hTMSC cells were cultured in the Mg-8Gd-4Y-xZn (x0, 1, 2, 3 wt%) extractions for 1 and 3 days, when the concentration of the extracted solution was 100%. The cytotoxicity of the alloy belongs to the category of non-toxic or micro-toxic. When the concentration of extract solution is 50% and 25%, the cell proliferation rate is more than 80%, and the cytotoxicity is 0 grade. The results showed that the alloy had good biological properties and was suitable for biomedical implantation. (5) after 24 h culture of MC3T3-E1 cells and hTMSC cells, most of the cells were fusiform and had almost no abnormal state. With the increase of Zn content, cell proliferation increased first and then decreased. The growth state of hTMSC cells was observed by scanning electron microscope. Most of the cells were fusiform, the extended state of aging alloy extract was good, and the pseudopodia grew into a network of adjacent cells.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG172;TG379;TG166.4

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