Improved Biocompatibility and Biodegradation of Zn-based Stent Materials through Surface Nano-Engineering

 描述：金属支架通常用于再血管化闭塞的动脉。美国心脏协会表示，2007年(已汇编的最新统计数据)进行了622,000次经皮冠状动脉介入治疗。一种生物可吸收的金属支架可以随着时间的推移无害地侵蚀掉，可以将与永久性支架相关的正常慢性风险降至最低。目前，镁和铁基合金在设计这种可生物降解支架方面取得了有限的成功。最近只推出了一种由Biotronik开发的名为Lekton Magic Stent的商用镁支架，但它溶解太快，涉及到生物相容性未知的稀土元素。密歇根理工大学提出的这项研究旨在首次开发一种替代的锌基支架系列，这种支架可以在体内持续6-9个月，并含有生物相容的锂。初步研究表明，锌在生物可吸收支架的应用中表现出理想的生理腐蚀行为。锌支架的可行性在我们的初步研究中得到了证实。锌和锌锂在体内的腐蚀行为及其对血管环境中降解率的影响仍然是悬而未决的问题，也是拟议的计划的主题。我们将评估生物可吸收锌和锌基支架的总体可行性。利用最近开发的一种动脉植入方法，将具有金属丝几何形状的样本植入大鼠的动脉壁，从而完成对材料生物腐蚀的体内评估。锌锂合金将成为 为了将材料性能调整到抗拉强度、断裂伸长率和渗透率等可接受的值而制备的。不同厚度和结构的氧化膜将被 使用阳极氧化在锌和锌锂合金表面配制。氧化膜的表面工程将导致可调的生物腐蚀速率。这项研究将引领 选择符合以下标准的表面改性特性：i)提高血液相容性和生物相容性以及锌基植入材料；ii)在最初的3-4个月内保持低于0.02毫米/年的腐蚀率；以及iii)4个月后不保护金属免受加速的(0.02毫米/年)生物降解。

 DESCRIPTION: Metal stents are commonly used to revascularize occluded arteries. The American Heart Association states that 622,000 percutaneous coronary interventions were performed in 2007 (the most recent period for which statistics have been compiled). A bio absorbable metal stent that harmlessly erodes away over time could minimize the normal chronic risks associated with permanent stents. Mg- and Fe-based alloys are currently pursued in designing such biodegradable stents with a limited success. Only one commercial Mg-based stent called Lekton Magic Stent and developed by Biotronik was recently introduced but it dissolves away too fast and involves rare earth elements, which have unknown biocompatibility. The research proposed at Michigan Tech aims to develop, for the first time, an alternative line of Zn-based stents that last 6-9 months in vivo and contain biocompatible Li. Preliminary study suggests that zinc exhibits ideal physiological corrosion behavior for bio absorbable stent application. The viability of a zinc stent was demonstrated in our preliminary study. The corrosion behavior in vivo for zinc and zinc-lithium with a passive layer of oxide film and its effect on the degradation rate in the vascular environment remain open questions, and are the subjects of the proposed program. The overall feasibility of a bio absorbable zinc and zinc-based stents with engineered surfaces will be evaluated. An in vivo evaluation of materials bio corrosion will be completed utilizing a recently developed arterial implantation method in which a sample with wire geometry is implanted into the arterial wall of a rat. Zinc-lithium alloys will be prepared in order to tailor the material properties to accepted values of tensile strength, elongation to failure, and penetration rate. Oxide films of varying thickness and structure will be formulated on surfaces of both zinc and zinc-lithium alloys using an anodization. The surface engineering of thin oxide films will lead to tunable rates of bio corrosion. The research will lead to selection of surface modification characteristics that meets the following criteria: i) improve hemocompatibility and biocompatibility and zinc-based implant materials; ii) keep corrosion rates below the 0.02 mm/year value in the first 3-4 months; and iii) will not protect metal from accelerated (>0.02 mm/year) biodegradation after 4 months.