Cameron Jude, Luccio Tiziana Di, Barr Jordan, Rocher Lison, Kim Eugene, Menary Gary H, Lennon Alex B, Kornfield Julia A
School of Mechanical and Aerospace Engineering, Queen's University Belfast, Belfast BT9 5AH, UK.
Department of Natural Sciences, Pitzer and Scripps Colleges, Claremont, CA 91711, USA; Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
Acta Biomater. 2025 Jan 15;192:175-188. doi: 10.1016/j.actbio.2024.10.048. Epub 2024 Nov 17.
Crystal structure and morphology dictate the mechanical, thermal, and degradation properties of poly l-lactide (PLLA), the structural polymer of the first clinically approved bioresorbable vascular scaffolds (BVS). New experimental methods are developed to reveal the underlying mechanisms governing structure formation during the crimping step of the BVS manufacturing process. Our research specifically examines the "U-bends" - the region where the curvature is highest and stress is maximised during crimping, which can potentially lead to failure of the device with dramatic consequences on patient life. A custom-made crimping rig operated at a synchrotron beamline enabled collection of wide- and small-angle X-ray scattering (WAXS/SAXS) to probe local variations of the polymer morphology as a function of position in the crest of multiple U-bends with 5 μm resolution in situ after crimping and expansion. Additionally, polarised light microscopy (PLM) images of these deformed U-bends revealed areas with varying stress distribution developed during crimping and expansion. These variations were dependant on the initial biaxial stretching processing step. The integrated X-ray scattering-microscopy approach offered a comprehensive work-flow for uncovering the intricate relationship between processing conditions and the corresponding spatially-resolved semicrystalline morphology of a BVS. STATEMENT OF SIGNIFICANCE: This research introduces a new method for gaining critical insights into the structural changes that occur during the manufacturing process of bioresorbable vascular scaffolds (BVS). The crimping and expansion of poly l-lactide (PLLA) - the structural material of BVS - are sequential manufacturing steps characterised by highly non-linear deformations at temperature conditions that remain unexplored. By utilising synchrotron X-ray scattering techniques alongside polarised light microscopy, we have developed new experimental methods to uncover the mechanisms governing structure formation during processing. This innovative approach not only deepens our understanding of the relationship between processing conditions and polymer morphology but also establishes the foundation for real-time observation methods during crimping and expansion. By improving the design and performance of BVS, this study has the potential to advance cardiovascular treatments and improve patient safety, making it highly relevant and impactful to both scientific research and clinical applications.
晶体结构和形态决定了聚左旋乳酸（PLLA）的机械、热学和降解性能，PLLA是首个获得临床批准的生物可吸收血管支架（BVS）的结构聚合物。人们开发了新的实验方法，以揭示在BVS制造过程的卷曲步骤中控制结构形成的潜在机制。我们的研究特别关注“U形弯”——在卷曲过程中曲率最高且应力最大的区域，这可能会导致装置失效，对患者生命造成严重后果。在同步加速器光束线上运行的定制卷曲装置能够收集广角和小角X射线散射（WAXS/SAXS），以探测卷曲和展开后多个U形弯顶部聚合物形态随位置变化的局部差异，原位分辨率为5μm。此外，这些变形U形弯的偏光显微镜（PLM）图像显示了卷曲和展开过程中应力分布不同的区域。这些差异取决于初始双轴拉伸加工步骤。综合X射线散射-显微镜方法为揭示加工条件与BVS相应的空间分辨半结晶形态之间的复杂关系提供了一个全面的工作流程。重要性声明：本研究引入了一种新方法，用于深入了解生物可吸收血管支架（BVS）制造过程中发生的结构变化。聚左旋乳酸（PLLA）——BVS的结构材料——的卷曲和展开是连续的制造步骤，其特点是在尚未探索的温度条件下发生高度非线性变形。通过将同步加速器X射线散射技术与偏光显微镜结合使用，我们开发了新的实验方法来揭示加工过程中控制结构形成的机制。这种创新方法不仅加深了我们对加工条件与聚合物形态之间关系的理解，还为卷曲和展开过程中的实时观察方法奠定了基础。通过改进BVS的设计和性能，本研究有可能推动心血管治疗并提高患者安全性，使其对科学研究和临床应用都具有高度相关性和影响力。
