Platelets on Chip: Studies of Mechanobiology of Platelet-Mediated Thrombosis Enabled by Molecular Fluorescence Sensors Grafted inside Microfluidic Chips

世界卫生组织估计，到2020年，全球将有近2500万人死于心血管疾病。血栓形成是导致危及生命的心血管疾病（如缺血性心脏病、中风和静脉血栓栓塞）的最常见病理。血栓形成是由血小板介导的，血小板是通常介导止血的小血细胞，止血是一种止血过程。然而，在血栓形成过程中，血小板会异常地粘附在血管壁上，并与纤维蛋白聚集形成血块，从而导致心脏病发作、中风和外周血管疾病。这种异常的血小板粘附可能是由血管中的胆固醇斑块破裂或狭窄处的血流紊乱引起的。由于局部血流和剪切条件是引发血小板粘附和活化的重要力学因素，因此研究可控血流条件下和可控药物作用下的血小板功能对于理解血栓形成机制和治疗至关重要。该奖项支持基础研究，以开发血管芯片，模仿人体中的微血管系统，可以提供一种方法来监测单个血小板在可调流体流动剖面下的行为，具有亚微米分辨率和高灵敏度。该芯片还可以同时研究多种药物及其组合对血小板的影响，促进药物筛选和血栓相关疾病的发现。因此，这项研究的成果将有利于美国社会。该研究涉及微机电系统、微流体、生物医学工程和生物力学等多个学科，使女性和少数民族学生能够广泛参与研究，从而对工程和科学教育产生积极影响。该项目旨在开发具有定量流动控制的血管模拟平台（流速和流动方向两者）、药理学试剂对血小板的定量治疗控制以及在单细胞水平监测血小板行为的能力。为了实现这些目标，首先，将建立一个实验-理论方法，以确定剪切速率的影响，并确定整合素张力传感器与合适的强度监测血小板的行为。其次，将研究体内剪切速率的影响和脉动流对血小板的影响。最后，将研究药物及其不同剂量组合对血小板的影响。该研究将填补技术知识的空白，如何开发一个平台，适用于研究血小板在可调剪切应力和药物治疗下的体外行为，在一个芯片上以受控的方式。该奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的智力价值和更广泛的影响审查标准。

The WHO estimates nearly 25 million CVD deaths worldwide in 2020. Thrombosis is the most common pathology causing life-threatening CVDs such as ischemic heart disease, stroke, and venous thromboembolism. Thrombosis is mediated by platelets which are small blood cells normally mediating hemostasis, a process of stopping bleeding. However, during thrombosis, platelets can abnormally adhere on blood vessel walls and aggregate with fibrin to form blood clots that cause heart attacks, strokes, and peripheral vascular disease. Such abnormal platelet adhesion can be initiated by the ruptured cholesterol plaques in blood vessels or by disturbed blood flow at stenoses. Because the local blood flow and shear conditions are important mechanical factors initiating platelet adhesion and activation, studying platelet functions under controllable flow conditions and under controllable pharmacological agents’ treatment is critical for the understanding of the mechanisms of thrombus formation and therapeutics. This award supports fundamental research to develop blood vessel chips, mimicking the microvasculature in human body, that can provide a way to monitor the behaviors of single platelets under tunable fluid flowing profiles with submicron resolution and high sensitivity. This chip also can allow simultaneous studies of the effects of multiple pharmacological agents and their combinations on the platelets, facilitating the drug screen and discovery for thrombus related diseases. Hence, the outcomes from this research will benefit the U.S. society. This research involves several disciplines including microelectromechanical system, microfluidics, biomedical engineering, and biomechanics, allowing broaden participation of women and underrepresented minority students in research, and thus resulting in a positive impact on engineering and science education.The project seeks to develop blood vessel mimicking platforms with quantitative flow control (both flow rate and flow direction), quantitative treatment control of pharmacological agents on platelets, and the ability of monitoring the behaviors of platelets at single cell level. Toward these goals, first, an experimental-theoretical methodology will be established to determine the influence of shear rates and identify the integrin tension sensors with suitable strengths for monitoring the behaviors of platelets. Second, the effects of the in vivo shear rates and the effects of pulsatile flow on platelets will be studied. Finally, the effects of the pharmacological agents and their combinations with varied doses on the platelets will be studied. This research will fill the technical knowledge gap on how to develop a platform suitable for studying the behaviors of platelets in vitro under tunable shearing stresses and pharmacological agents’ treatment in a controlled manner on a chip.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.