Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna 1090, Austria; Ludwig Boltzmann Institute for Cardiovascular Research, Vienna 1090, Austria.
Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna 1090, Austria; Ludwig Boltzmann Institute for Cardiovascular Research, Vienna 1090, Austria.
Mater Sci Eng C Mater Biol Appl. 2021 May;124:112085. doi: 10.1016/j.msec.2021.112085. Epub 2021 Mar 31.
Conventional electrospun small diameter vascular grafts have a random fiber orientation. In order to achieve mechanical characteristics similar to a native blood vessel, a controllable fiber orientation is of interest. In this study the electrospinning jet was directly controlled by means of an auxiliary, changeable electrostatic field, so that the fibers could be deposited in adjustable orientations. Prostheses with circumferentially, axially, fenestrated and randomly aligned fibers were electrospun on Ø2mm mandrels out of a thermoplastic polyurethane (PUR) and a polylactid acid (PLLA). The impact of the materials and the various preferential fiber orientations on the resulting biomechanics was investigated and compared with that of the native rat aorta in quasistatic and dynamic hoop tensile tests. The test protocol included 3000 dynamic loading cycles in the physiological blood pressure range and ended with a quasistatic tensile test. Any orientation of the fibers in a particular direction resulted in a significant reduction in scaffold porosity for both materials. The standard randomly oriented PUR grafts showed the highest compliance of 29.7 ± 5.5 [%/100 mmHg] and were thus closest to the compliance of the rat aortas, which was 37.2 ± 6.5 [%/100 mmHg]. The maximum tensile force was increased at least 6 times compared to randomly spun grafts by orienting the fibers in the circumferential direction. During the 3000 loading cycles, creeping of the native rat aorta was below 1% whereas the electrospun grafts showed creeping up to 2.4 ± 1.2%. Although the preferred fiber orientations were only partially visible in the scanning electron micrographs, the mechanical effects were evident. The investigations suggest a multi-layer wall structure of the vascular prosthesis, since none of the preferred fiber directions and the materials used could imitate the typical j-shaped mechanical characteristics of the rat aorta.
传统的小直径静电纺血管移植物具有随机纤维取向。为了获得与天然血管相似的机械性能，可控的纤维取向是感兴趣的。在这项研究中，通过辅助的、可改变的静电场直接控制电纺射流，使得纤维可以以可调节的取向沉积。用热塑性聚氨酯（PUR）和聚乳酸（PLLA）在Ø2mm 心轴上静电纺制了具有周向、轴向、有孔和随机排列纤维的移植物。研究了材料和各种优先纤维取向对生物力学的影响，并与在准静态和动态环向拉伸试验中的大鼠主动脉的生物力学进行了比较。测试方案包括在生理血压范围内进行 3000 次动态加载循环，最后进行准静态拉伸试验。两种材料中任何特定方向的纤维取向都会导致支架孔隙率显著降低。标准的随机取向 PUR 移植物的顺应性最高，为 29.7 ± 5.5 [%/100mmHg]，因此最接近大鼠主动脉的顺应性，大鼠主动脉的顺应性为 37.2 ± 6.5 [%/100mmHg]。通过将纤维沿周向取向，最大拉伸力至少增加了 6 倍，与随机纺丝移植物相比。在 3000 次加载循环中，天然大鼠主动脉的蠕变小于 1%，而静电纺丝移植物的蠕变高达 2.4 ± 1.2%。尽管优先纤维取向在扫描电子显微镜照片中仅部分可见，但机械效应是明显的。研究表明，血管移植物具有多层壁结构，因为没有一种优先纤维方向和使用的材料可以模仿大鼠主动脉的典型 J 形机械特性。
