Collaborative Research: Active Transport of Lipid Vesicles in Osmotic Gradients

活细胞的膜对水具有高度和选择性的渗透性。由于溶解的分子引起的渗透压的变化驱动水穿过膜的运输，从而引起流体流动和膜运动。这种流动对于生物过程是至关重要的，例如细胞水含量的调节、细胞内和细胞外隔室的运输以及组织中细胞的迁移。尽管它们的重要性，这些过程的基本流体力学仍然知之甚少。这个项目旨在促进我们对渗透梯度驱动的流体流动和膜运动的理解。这些知识将进一步使涉及细胞外囊泡的提取、分离和递送的生物技术成为可能，这些生物技术被积极地用作治疗人类疾病的诊断和治疗工具。该项目还将通过实验室图尔斯参观和暑期研究体验，为来自代表性不足群体的初高中学生提供教育机会。该研究的中心目标是发展实验平台和理论模型，阐明渗透梯度中脂囊泡运动的物理机制？一个叫做电泳的过程使用微流体系统，该研究将量化囊泡速度作为膜特性的函数，如囊泡大小，渗透性，刚度，张力/多余面积和表面电荷以及环境特性，如溶质类型，梯度大小，流体粘度和限制。 值得注意的是，该项目将使用包含水通道蛋白水通道的脂质膜来创建模拟天然外泌体的高渗透性囊泡。这些实验将提供明确的数据，以提高我们的理解，电泳及其对生物学中的囊泡运输的影响。所提出的理论将整合以前的工作，刚性球形膜与模型的膜动力学，占不可压缩的脂质双层内的变形和流动。理论研究将最终重现和解释实验观察到的快速囊泡运动的渗透梯度。最后，电泳囊泡分选的演示将为涉及细胞外囊泡分离和表征的生物技术提供基本基础。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

The membranes of living cells are highly and selectively permeable to water. Variations in the osmotic pressure due to dissolved molecules drives water transport across the membrane, thereby inducing fluid flows and membrane motions. Such flows are critical to biological processes such as the regulation of cell water content, the transport of intra- and extracellular compartments, and the migration of cells in tissues. Despite their importance, the fundamental fluid mechanics underlying these processes remains poorly understood. This project aims to advance our understanding of fluid flows and membrane motions driven by osmotic gradients. Such knowledge will further enable biotechnologies involving the extraction, separation, and delivery of extracellular vesicles, which are actively pursued as diagnostic and therapeutic tools for treating human diseases. The project will also provide educational opportunities to middle and high school students from underrepresented groups through laboratory tours and summer research experiences.The central goal of the research is to develop experimental platforms and theoretical models that elucidate the physical mechanisms underlying the motion of lipid vesicles in osmotic gradients ? a process called osmophoresis. Using microfluidic systems, the research will quantify vesicle velocity as a function of membrane properties such as vesicle size, permeability, rigidity, tension / excess area, and surface charge as well as environmental properties such as solute type, gradient magnitude, fluid viscosity, and confinement. Notably, the project will use lipid membranes incorporating aquaporin water channels to create high permeability vesicles that mimic native exosomes. The experiments will provide definitive data with which to enhance our understanding of osmophoresis and its impact on vesicle transport in biology. The proposed theory will integrate previous work on the osmophoresis of rigid spherical membranes with models of membrane dynamics that account for deformation and flow within incompressible lipid bilayers. The theoretical investigations will ultimately reproduce and explain experimental observations of rapid vesicle motions in osmotic gradients. Finally, the demonstration of osmophoretic vesicle sorting will provide a fundamental basis for biotechnologies involving the separation and characterization of extracellular vesicles.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.