Development of SMP's for Cardiovascular Use

描述（由申请人提供）： 植入心血管器械以治疗各种瓣膜、血管和血管外并发症的微创手术技术越来越多地用于改善患者结局，并降低发病率和成本。这些设备最初基于简单的金属，现在通过使用精确设计的材料，如金属双晶片（形状记忆合金）和新的聚合物结构，变得更加复杂。特别是，聚合物在这些应用中表现出优于金属和金属合金的显著优点，包括易于进行表面改性以增强生物相容性、更大的机械柔性以更准确地模拟天然机械行为以及各种各样的基础结构配置的可用性。操纵聚合物以产生形状记忆特性是最新的发展，由于其高度的形状可恢复性（比金属合金大的数量级），其在设计微创心血管装置方面具有显著更大的自由度。然而，一些实质性的挑战阻碍了形状记忆聚合物（SMP）作为外科植入物的创新生物材料的可靠和直接的应用。该项目的目标是通过明确量化一种有前途的SMP类型的热机械性能，并将此信息注入到商用有限元模型（ABAQUS）中，来消除SMP设计过程中的这一限制。这将为希望使用SMP的心血管器械设计人员提供两项增强功能，以使SMP生物材料能够用于未来的外科器械：（1）基于SMP的器械的合理设计和概念验证所需的新SMP工程基准特性，以及（2）在制造前完善和测试器械设计的强大先验评估工具。然后，该模型将被用于生产两种越来越复杂的原型设备：一种血管支架，其形状可恢复性比目前使用金属形状记忆合金的血管支架大得多，以及一种人工心脏瓣膜。

DESCRIPTION (provided by applicant): Minimally invasive surgical techniques to implant cardiovascular devices for treatment of a variety of valvular, vascular and extra-vascular complications are increasingly exploited to improve patient outcomes, and reduce morbidity and cost. Originally based on simple metals, these devices are now becoming more sophisticated through the use of precisely engineered materials such as metal bimorphs (shape memory alloys) and new polymer structures. Polymers, in particular, exhibit significant advantages in these applications over metals and metal alloys, including ease of surface modification that enhances biocompatibility, greater mechanical flexibility to more accurately simulate native mechanical behavior, and availability of a wide variety of base structural configurations. Manipulation of polymers to produce shape memory characteristics is the most recent evolution, which due to their high degree of shape recoverability (order of magnitude greater than metal alloys) promises significantly greater freedom in designing minimally invasive cardiovascular devices. However, several substantial challenges preclude reliable and direct applications of shape memory polymers (SMPs) as innovative biomaterials for surgical implants. The goal of this project is to remove this limitation in the SMP design process by explicitly quantifying the thermomechanical properties of one promising type of SMP, and infusing this information into a commercially available finite element model (ABAQUS). This will provide designers of cardiovascular devices who wish to use SMPs with two enhancements required to enable exploitation of SMP biomaterials in future surgical devices: (1) new SMP engineering benchmarking characteristics required for rational design and proof-of-concept for SMP-based devices, and (2) a powerful a priori evaluation tool to refine and test device designs prior to fabrication. The model will then be exercised to produce two increasingly complex prototype devices: a vascular stent with significantly greater shape recoverability than currently available using metal shape memory alloys, and a prosthetic heart valve.