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

世卫组织估计，2020年全球有近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的最常见病理，如缺血性心脏病、中风和静脉血栓栓塞症。血栓形成是由血小板介导的，血小板是小血细胞，通常参与止血，这是一个止血过程。然而，在血栓形成过程中，血小板会异常地附着在血管壁上，并与纤维蛋白聚集形成血栓，从而导致心脏病发作、中风和外周血管疾病。这种异常的血小板黏附可由血管中的胆固醇斑块破裂或狭窄处的血流紊乱引起。由于局部血流和切变条件是启动血小板黏附和激活的重要力学因素，因此研究可控血流条件下和可控药物治疗下的血小板功能对于了解血栓形成机制和治疗方法具有重要意义。该奖项支持开发模拟人体微血管系统的血管芯片的基础研究，该芯片可以提供一种方法，以亚微米分辨率和高灵敏度在可调的流体流动剖面下监测单个血小板的行为。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，促进血栓相关疾病的药物筛选和发现。因此，这项研究的结果将造福于美国社会。这项研究涉及微电子机械系统、微流体、生物医学工程和生物力学等多个学科，允许更多的女性和未被充分代表的少数民族学生参与研究，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量控制(流量和流向)、药物对血小板的定量治疗控制以及在单细胞水平上监测血小板行为的血管模拟平台。为了实现这些目标，首先，将建立一种实验-理论方法来确定切变率的影响，并确定具有合适强度的整合素张力传感器来监测血小板的行为。其次，将研究体内切变率的影响和脉动流对血小板的影响。最后，将研究不同剂量的药物及其组合对血小板的影响。这项研究将填补关于如何开发一个平台的技术知识空白，该平台适用于研究体外可调剪应力下的血小板行为和芯片上药物治疗的受控方式。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.