Chen Chenxin, Tan Jinyun, Wu Wei, Petrini Lorenza, Zhang Lei, Shi Yongjuan, Cattarinuzzi Emanuele, Pei Jia, Huang Hua, Ding Wenjiang, Yuan Guangyin, Migliavacca Francesco
National Engineering Research Center of Light Alloy Net Forming & State Key Laboratory of Metal Matrix Composite, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, China, 200240.
Department of Vascular Surgery, Huashan Hospital of Fudan University, No. 12 Mid-Wulumuqi Road, Shanghai 200040, China.
ACS Biomater Sci Eng. 2018 Nov 12;4(11):3864-3873. doi: 10.1021/acsbiomaterials.8b00700. Epub 2018 Oct 8.
Biodegradable magnesium alloy stents exhibit deficient corrosion period for clinic applications, making the protective polymer coating more crucial than drug-eluting stents with the permanent metal scaffold. We implemented a cohesive method based on a finite element analysis method to predict the integrity of adhesive between coating and stent during the crimping and deployment. For the first time, the three-dimensional quantitative modeling reveals the process of polymer coating delamination and stress concentration. The fracture and microcracks of coatings were consistent with the simulation result, confirmed by the scanning electron microscopy observation. Moreover, we analyzed four possible factors, i.e., stent design, strut material, coating polymer, and thickness of the coating, affecting the stent-coating damage and the distribution of the stress in coatings. Mg-Nd-Zn-Zr alloy with lower yield strength performed a more uniform strain distribution and more favorable adhesion of the coating than the commercial magnesium alloy AZ31. Shape optimization of stent design improves the strain and stress distribution of coating remarkably, avoiding coating delamination. Additionally, PLGA coating with lower elastic modulus and yield strength tends to follow the deformation of the stent better and to adhere on the surface more tightly, compared to PLLA polymer. A reduction in coating thickness and an increase in the strength of stent-coating interface improve the resistance to delamination. Our framework based on cohesive method provides an in-depth understanding of stent-coating damage and shows the way of computational analyses could be implemented in the design of coated biodegradable magnesium stents.
可生物降解镁合金支架在临床应用中表现出腐蚀期不足的问题，这使得保护性聚合物涂层比带有永久性金属支架的药物洗脱支架更为关键。我们基于有限元分析方法实施了一种内聚方法，以预测在压接和展开过程中涂层与支架之间粘合剂的完整性。首次通过三维定量建模揭示了聚合物涂层分层和应力集中的过程。涂层的断裂和微裂纹与模拟结果一致，这通过扫描电子显微镜观察得到了证实。此外，我们分析了影响支架 - 涂层损伤和涂层中应力分布的四个可能因素，即支架设计、支柱材料、涂层聚合物和涂层厚度。与商用镁合金AZ31相比，屈服强度较低的Mg - Nd - Zn - Zr合金表现出更均匀的应变分布和更良好的涂层附着力。支架设计的形状优化显著改善了涂层的应变和应力分布，避免了涂层分层。此外，与聚乳酸（PLLA）聚合物相比，具有较低弹性模量和屈服强度的聚乳酸 - 羟基乙酸共聚物（PLGA）涂层往往能更好地跟随支架变形并更紧密地粘附在表面上。涂层厚度的减小和支架 - 涂层界面强度的增加提高了抗分层能力。我们基于内聚方法的框架提供了对支架 - 涂层损伤的深入理解，并展示了在涂层可生物降解镁支架设计中实施计算分析的方法。
