Saqib Muhammad, Beshchasna Natalia, Cuniberti Gianaurelio, Opitz Joerg
Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Maria-Reiche-Strasse 2, 01109 Dresden, Germany.
Institute of Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, 01062 Dresden, Germany.
Materials (Basel). 2024 Dec 26;18(1):46. doi: 10.3390/ma18010046.
Coated metallic stents are the next generation of metallic stents with improved surface properties. To evaluate the degradation behavior of stents in vitro, different in vitro degradation models can be applied: (i) static immersion test: degradation under static fluid condition, (ii) fluid dynamic test: degradation under flowing fluid, and (iii) electrochemical corrosion test: degradation under the influence of electric potential. During these experimental procedures, stents interact with the simulated blood plasma, and degradation products are formed in the form of depositions on the stent surface, likewise in vivo experiments. These deposited crystals act as a hindrance to the application of important characterization techniques (e.g., mass loss measurement for the calculation of corrosion rate and examining the adhesion of the coating to metallic stents after fluid dynamic exposure). Therefore, to better characterize the coatings, the removal of these depositions is significant. In this work, we investigate the influence of in vitro test conditions in fluid dynamic biostability tests on the biostability of titanium oxynitride (TiON) coated stainless steel stents by adapting various fluid dynamic experimental parameters. The experimental conditions are based on modification in the components of fluid dynamic setup (e.g., tubings), simulated body fluid (SBF), with and without Ca and Mg ions, and the cleaning procedure (use of water, acetone, and isopropanol). Four different experiments were conducted under various experimental parameter sets. SEM and EDX measurements were used for the identification of degradation products after each experiment. This study highlights the importance of optimized experimental conditions showing negligible depositions when utilizing Puriflex tubing or a comparable artificial vessel, SBF devoid of Ca and Mg ions, and performing sample cleaning with distilled water in an ultrasonic bath. The presented conditions were optimized for titanium oxynitride coated samples. A similar approach could be applied to other samples with or without some small variation.
涂层金属支架是具有改善表面性能的下一代金属支架。为了评估支架在体外的降解行为，可以应用不同的体外降解模型：（i）静态浸泡试验：在静态流体条件下的降解；（ii）流体动力学试验：在流动流体下的降解；（iii）电化学腐蚀试验：在电势影响下的降解。在这些实验过程中，支架与模拟血浆相互作用，降解产物以沉积物的形式形成在支架表面，体内实验也是如此。这些沉积晶体对重要表征技术的应用构成阻碍（例如，通过质量损失测量计算腐蚀速率以及在流体动力学暴露后检查涂层与金属支架的附着力）。因此，为了更好地表征涂层，去除这些沉积物很重要。在这项工作中，我们通过调整各种流体动力学实验参数，研究流体动力学生物稳定性测试中的体外测试条件对氮氧化钛（TiON）涂层不锈钢支架生物稳定性的影响。实验条件基于对流体动力学装置组件（如管道）、模拟体液（SBF）（含或不含钙和镁离子）以及清洗程序（使用水、丙酮和异丙醇）的修改。在各种实验参数集下进行了四个不同的实验。每次实验后使用扫描电子显微镜（SEM）和能量色散X射线光谱（EDX）测量来鉴定降解产物。本研究强调了优化实验条件的重要性，当使用Puriflex管道或类似的人造血管、不含钙和镁离子的SBF并在超声浴中用蒸馏水进行样品清洗时，沉积物可忽略不计。所提出的条件是针对氮氧化钛涂层样品进行优化的。类似的方法可应用于其他样品，可能会有一些小的变化。
