Magnetically propelled microwheels for rapid thrombolysis in small arteries

项目总结：在占缺血性卒中20%的小血管卒中（SVS）中， 纤溶酶原激活剂（tPA）是无效的，因为它可能需要非常长的时间才能扩散到凝块， 基于导管的血栓切除装置不能进入小血管。此外，治疗相关 对于所有缺血性卒中，血栓形成将tPA的使用限制在症状发作后几小时内。作为 因此，迫切需要克服这些限制的战略，特别是在SVS中，同时减少 与tPA相关的风险。在成功的先前工作的基础上，提出了一种药物递送策略， 可以选择性地靶向小动脉闭塞并输送机械力以加速血栓溶解。的 该提议的目的是在实际模型中研究和测试一种注入的方法， 将分散的磁珠组装成血细胞大小的微轮（µwheels）， 闭塞性凝块位于小血管中，并通过机械和生物化学的组合溶解它们。 行动上核心假设是，µwheels可以（i）通过利用低流量来靶向闭塞的小动脉， 这些血管入口处的区域，（ii）以比血管入口处的区域快一个数量级的速率实现再灌注。 可溶性tPA，和（iii）改善中风鼠模型的结果。这一假设将用 以下具体目标：目标1。确定定位闭塞的µwheels的磁场条件。µWheels 将在流动的血液中组装并被引导到堵塞的通道或血管。微流体，斑马鱼， 3D人体脑血管模型将用于测试组装和靶向。目标2.确定费率 使用tPA功能化的μwheels进行闭塞性血栓的溶栓。据推测，tPA官能化 µwheels可以溶解微流控模型中富含纤维蛋白和血小板的凝块，并在体外实现再灌注。 斑马鱼和3D人类脑血管模型，速率显著快于可溶性tPA。目标3.测量 µwheel体内溶栓的功能益处。与可溶性tPA相比，µwheel介导的 溶栓将改善小鼠中风模型的安全性、运动和神经学结局， 使用高分辨率MRI和微型CT进行可视化。在目标1和2中，预期成果是确定 µwheel组装、靶向和纤溶的操作条件可提供更快的再灌注， tPA，并且可以按比例放大到人类大小的血管网络。在目标3中，将显示µwheel 在神经行为结果方面，溶栓是一种优于全身给予tPA的上级策略。 中风模型，并可以在体内成像。这种方法很重要，因为它可以导致发展 一种比目前可用的方法更快速和更少侵入性的缓解缺血的策略。这 这种方法是创新的，因为使用外部磁场来推动纤溶微装置， 闭塞部位，并提供机械作用，以加速再灌注时间相比，全身 给予tPA。

Project Summary: In small vessel stroke (SVS), which accounts for 20% of ischemic strokes, tissue plasminogen activator (tPA) is ineffective because it can take a prohibitively long time to diffuse to the clot, and catheter-based thrombectomy devices cannot access small vessels. Moreover, treatment associated hemorrhaging limits tPA use to within a few hours of the onset of symptoms for all ischemic strokes. As a result, there is an urgent need for strategies that overcome these limitations, particularly in SVS, while reducing the risks associated with tPA. Building on a successful previous work, a drug delivery strategy is proposed that can selectively target small artery occlusions and deliver mechanical force to accelerate thrombolysis. The objective of this proposal is to investigate and test within realistic models an approach where injected, dispersed magnetic beads are assembled into blood cell sized microwheels (µwheels) capable of targeting occlusive clots located in small vessels and lysing them with a combination of mechanical and biochemical action. The central hypothesis is that µwheels can (i) target occluded small arteries by exploiting the low flow regions at the entrance of these vessels, (ii) achieve reperfusion at rates an order-of-magnitude faster than soluble tPA, and (iii) improve outcomes in murine models of stroke. This hypothesis will be tested with the following specific aims: Aim 1. Identify magnetic field conditions for µwheels targeting of occlusions. µWheels will be assembled in flowing blood and directed to occluded channels or vessels. Microfluidic, zebrafish, and 3D human cerebrovascular models will be used to test the assembly and targeting. Aim 2. Determine rates for thrombolysis of occlusive thrombi using tPA functionalized µwheels. It is postulated that tPA functionalized µwheels can dissolve fibrin- and platelet-rich clots within microfluidic models and achieve reperfusion in zebrafish and 3D human cerebrovascular models, at rates significantly faster than soluble tPA. Aim 3. Measure the functional benefit of µwheel thrombolysis in vivo. In comparison to soluble tPA, µwheel mediated thrombolysis will improve safety, motor, and neurological outcomes in murine stroke models and can be visualized using high-resolution MRI and micro-CT. In Aims 1 and 2 the expected outcomes are identifying the operating conditions for µwheel assembly, targeting, and fibrinolysis that provide faster reperfusion compared to tPA and can be scaled-up to human-size vascular networks. In Aim 3, it will be shown that µwheel thrombolysis is a superior strategy to systemic administration of tPA in terms of neurobehavioral outcomes in a stroke model and can be imaged in vivo. This approach is significant because it could lead to the development of a more rapid and less invasive strategy for alleviating ischemia than methods currently available. This approach is innovative because of the use of external magnetic fields to propel fibrinolytic microdevices to the sites of occlusion and provide mechanical action to accelerate reperfusion time compared to systemic administration of tPA.