铁基可降解心血管支架材料研究

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	铁基可降解心血管支架材料研究
	徐文利
学位类型	硕士
导师	杨柯
	2011
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料加工工程
关键词	铁基材料心血管支架生物降解 Fe-mn合金生物相容性 Iron Based Material Coronary Stent Biodegradation Fe-mn Alloy Biocompatibility
摘要	"作为新型的可降解心血管支架材料，铁基材料以其优异的力学性能、良好的生物相容性使其具有独特的潜在优势。已有研究结果证明，纯铁作为心血管支架材料安全可靠，但是面临降解速度过低和由于其存在磁性而影响核磁共振成像等问题。本文首先研究了纯铁在模拟体液中的降解行为和体外生物相容性。为进一步提高纯铁的降解速度，本文制备了Fe-30Mn合金、Fe-30Mn-1C合金和Fe-30Mn-0.05S合金，研究了其力学性能、磁性、降解性能，并对其体外生物相容性进行了初步的研究。得到如下主要研究成果：电化学测试结果表明，纯铁在Hank’s溶液中的阳极极化曲线的塔菲尔斜率为23.71mV，阳极极化曲线上无钝化平台。说明纯铁在Hank’s溶液中的阳极过程容易进行，无保护性的钝化膜形成。阴极极化曲线表明，阴极过程为氧的还原过程，由于受氧的扩散速度控制，阴极过程存在20μA/cm2的极限扩散电流密度。阴极极化曲线同时表明，析氢过程为极化活化控制，而且存在较大过电位。因此，纯铁的降解受氧还原过程控制，由于氧还原过程存在极限扩散电流密度，所能提供的最大降解速度为0.24mm/year。所以向铁中加入具有较低平衡电位或者低析氢过电位的元素可能会提高其降解速度。在Hank’s溶液中的浸泡实验表明，由于磷酸盐的析出，纯铁在Hank’s溶液中的降解速度仅为0.011-0.036mm/year，而在生理盐水中的降解速度可达0.05-0.17mm/year。所以Hank’s溶液中磷酸盐的析出，会缩小不同材料间降解速度的差异。为了提高降解速度并降低磁性，采用真空感应熔炼法制备了Fe-30Mn、Fe-30Mn-1C、Fe-30Mn-0.05S合金。经固溶处理后，Fe-30Mn合金为单一奥氏体结构，应力作用下易产生ε、α马氏体和孪晶；Fe-30Mn-1C合金为单一奥氏体，且应力作用下不产生相变；Fe-30Mn-0.05S合金具有与Fe-30Mn合金同样的相组成。Fe-30Mn、Fe-30Mn-1C合金均具有较316L不锈钢更优的力学性能，其中Fe-30Mn-1C合金兼具高强、高塑性，屈服强度为373MPa、抗拉强度为1010MPa、断后延伸率为88%。三种合金均为顺磁性，均具有较低的磁化率，其中Fe-30Mn-1C合金具有最低的磁化率。Fe-30Mn、Fe-30Mn-1C、Fe-30Mn-0.05S合金在生理盐水中的降解速度均较纯铁有所提高，分别为0.10-0.15mm/year、0.16-0.22mm/year、0.14-0.16mm/year。纯铁和Fe-30Mn、Fe-30Mn-1C、Fe-30Mn-0.05S合金均具有良好的血液相容性，溶血率均小于5%，同时具有良好的抗凝血性能。良好的抗凝血性能来自于材料对内源性凝血过程中凝血酶原激活物形成阶段的抑制作用。由于材料的表面能中的极性分量/色散分量的比值较高，材料还同时具有较好的抗血小板黏附性能。细胞毒性实验表明，四种铁基材料的24h、72h浸提液在与L929细胞共培养1天后的细胞毒性等级均为1级合格，培养2、3天后均出现一定的细胞毒性。毒性高低与降解速度的大小一致。"
其他摘要	"Iron-based alloy has shown potential application as coronary stent material due to its good biocompatibility and excellent mechanical properties. The reported results have demonstrated that iron is a suitable metal for manufacture of biodegradable stents, but a higher degradation rate is needed. Meanwhile, pure iron is not compatible with magnetic resonance imaging (MRI), a fast growing medical imaging technique. In this study the degradation behavior of pure iron in simulated body fluid was first investigated. In order to improve the degradation rate of pure iron, Fe-30Mn, Fe-30Mn-1C and Fe-30Mn-0.05S alloys were developed, and their mechanical properties, magnetic properties and degradation behaviors were investigated. The biocompatibility of the developed alloys was also evaluated in vitro. The main results are summarized as followings: The anodic Tafel slope of pure iron in Hank’s solution was 23.71mV, and no plateau was observed in the anodic polarization curve, which indicated that the anodic reaction would proceed easily. The cathodic reaction was an oxygen reduction which was controlled by the diffusion rate of oxygen, and the limited diffusion current density was 20μA/cm2, indicating that the highest degradation rate of pure iron in static Hank’s solution could be 0.24mm/year. Based on the above results the addition of element with lower equilibrium potential or lower hydrogen evolution overpotential into iron should accelerate the degradation rate of iron-based material. The results of immersion test of pure iron in Hank’s solution showed that the deposition of phosphate decreased the degradation rate dramatically, which can narrow the difference of degradation rates among different materials. To accelerate the degradation rate and lower the magnetic susceptibility of pure iron, Fe-30Mn, Fe-30Mn-1C and Fe-30Mn-0.05S alloys were prepared by vacuum induction melting. After solution treatment, the Fe-30Mn alloy showed single γ phase, but ε, α and twin were observed after deformation because of the TRIP/TWIP effects. The Fe-30Mn-0.05S alloy had the similar phase composition with Fe-30Mn alloy. The Fe-30Mn-1C alloy presented single stable γ phase, and no ε, α phase was observed after deformation. The mechanical properties of Fe-30Mn and Fe-30Mn-1C alloys were better than that of 316L SS, a commercially used coronary stents material. The Fe-30Mn-1C alloy combined high strength and high ductility with yield strength of 373MPa, tensile strength of 1010MPa and elongation of 88%. All the three alloys were paramagnetic, and Fe-30Mn-1C alloy had the lowest magnetic susceptibility compared with other two alloys. The degradation rates of Fe-30Mn, Fe-30Mn-1C and Fe-30Mn-0.05S alloys in normal solution were 0.10-0.15mm/year, 0.16-0.22mm/year and 0.14-0.16mm/year, respectively, higher than that of pure iron. Pure iron, Fe-30Mn, Fe-30Mn-1C and Fe-30Mn-0.05S alloys possess good blood-compatibility. The hemolysis rates of the four materials are all less than 5% and meet the requirement of medical implant materials. All the four materials showed an inhibition of the prothrombin activator formation process, which ensures the good anti-clotting properties. Densities of the adhered platelets on surfaces of the three developed alloys were all lower than that on the surface of 316L SS because of the higher γsp/γsd values of the developed alloys. The cytotoxicity evaluation by MTT revealed that all the extracts of the four iron-based materials showed no toxicity after co-cultured with L929 cells for 1 day. After co-cultured 2 and 3 days all the extract displayed certain toxicity to L929 cells, and the cytotoxicity levels were accordance with the degradation rate of the materials."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64398
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	徐文利. 铁基可降解心血管支架材料研究[D]. 北京. 中国科学院金属研究所,2011.