可降解镁锌合金支架材料加工改性方法的研究进展

药物洗脱支架是冠心病支架治疗中的首选材料，但其永久存留在体内易损害内皮细胞，还有可能发生支架内血栓形成、支架内再狭窄等严重问题，而且现在冠心病发展越来越年轻化，导致药物洗脱支架在临床工作中的应用越来越受到限制。近年来，生物可降解材料逐渐被开发和探索，作为心脏支架材料的新生力量，被国内外多个研究机构看好。主要介绍了可降解镁锌合金材料。首先介绍了镁、锌元素的良好的生物相容性，它们是人体内含量丰富的元素，在体内多种生命活动中都发挥重要作用，缺乏镁、锌元素会增加人体患心血管等疾病的风险，镁锌元素组合还有助于改善各自不适宜的性能，使其更接近临床对可降解材料的需求。然而，镁锌合金支架降解产物局部浓度过高、支架的力学性能和降解速率可控机制等仍需要进一步提高。针对这些问题，重点讨论了近些年来常用于改善合金材料性能的加工改性方法，常用于改进镁锌合金材料的技术包括添加元素、表面改性、热处理、塑性加工、快速凝固、多种技术相结合等方法。介绍了这些方法的原理、效果、优点以及作为可降解血管支架改性方法的局限性，最后对生物可降解镁锌合金支架进行了展望。

Research Progress of on Processing and Modification Methods of Degradable Magnesium Zinc Alloy Scaffolds

Drug-eluting stents are currently the preferred material in the stent treatment of coronary heart disease, but their permanent presence in the body will damage endothelial cells, stent thrombosis, restenosis, etc. These disadvantages gradually become apparent with years of extensive use. Bioresorbable scaffold materials can provide temporary support for blood vessels, and can be completely degraded in the body after the task is completed, so that blood vessels can restore their original appearance. Its unique advantages become the future development direction of cardiac vascular stents. At present, polymer and magnesium are mainly used in the research of bioresorbable scaffold materials. However, bioresorbable polymer scaffolds are limited in the field of biodegradable scaffolds due to insufficient radial support, difficulty in observation and high risk of thrombosis. As a new member of the bioresorbable vascular scaffolds, due to their biosafety and mechanical properties similar to those of traditional metal stents, the bioresorbable magnesium-zinc alloy scaffold has been favored by many research institutions in China and abroad. Firstly, the good biocompatibility of magnesium and zinc is introduced. They are abundant elements in the human body and play an important role in a variety of life activities. A lack of magnesium or zinc can increase the risk of human diseases such as cardiovascular diseases. If magnesium and zinc are combined, their undesirable properties can be improved to bring them closer to the need for biodegradable materials. However, the local high concentration of degradation products, mechanical properties and degradation rate control mechanism of Mg-Zn alloy scaffolds need to be further improved. In view of these problems, the improvement measures in recent years are discussed. The techniques commonly used to improve Mg-Zn alloy materials include addition of other elements, surface modification, heat treatment, plastic processing, rapid solidification, combination of various technologies, etc. Among these methods, surface modification is considered as a major category, including chemical transformation, anodic oxidation, electrochemical deposition, plasma spraying, ion implantation, physical vapor deposition, laser technology, sol-gel and other methods. It has been proved by many researchers that the properties of Mg-Zn alloy can be improved effectively by one or more techniques combined with suitable parameters. The principles of these improved technologies are summarized, the effects are illustrated with examples, and the limitations as biodegradable vascular scaffolds are explored. The surface modification is the main method in the improved technology. Through the mechanical, physical, chemical and biological-chemical method in preparation of surface coating, this technique has simple preparation method, does not affect performance alloy itself and can improve the overall performance alloy. It is outstanding in improving the initial corrosion resistance of alloys. However, many methods have shortcomings such as high brittleness and loose structure. The addition of some other metals or rare earth elements, heat treatment, plastic processing, rapid solidification can also effectively improve the mechanical properties and corrosion resistance of Mg-Zn alloy and enhance its biocompatibility. However, the method of adding elements is expensive, and it is difficult to control the uniform surface corrosion. Heat treatment and plastic processing can not fully control the galvanic corrosion in the alloy. Rapid solidification can refine grain size and reduce impurities, but the alloy still has different degrees of oxidation. The combination of a variety of methods can be used to check and fill gaps, which has a more prominent advantage in improving the overall performance of alloy. Finally, the future development of biodegradable Mg-Zn alloy scaffolds is prospected.