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。由于溶解分子引起的渗透压的变化驱动水在膜上的传输，从而引起流体流动和膜运动。这种流动对生物过程至关重要，如细胞水分含量的调节、细胞内和细胞外隔间的运输以及细胞在组织中的迁移。尽管它们很重要，但这些过程背后的基本流体力学仍然知之甚少。这个项目的目的是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提取、分离和输送细胞外小泡的生物技术成为可能，这些技术被积极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参观和暑期研究体验为来自代表性不足群体的初中生和高中生提供教育机会。拟议工作的中心目标是开发实验平台和理论模型，以阐明渗透梯度中脂泡运动的物理机制？这一过程被称为渗透作用。使用微流控系统，我们将量化囊泡速度作为膜属性的函数，如囊泡大小、渗透性、刚性、张力/过剩面积和表面电荷，以及环境属性如溶质类型、梯度大小、流体粘度和限制。值得注意的是，我们将使用含有水通道蛋白水通道的脂膜来创建模仿天然外切体的高渗透性囊泡。拟议的实验将提供明确的数据，以加强我们对渗透作用及其对生物学中囊泡运输的影响的理解。提出的理论将把以前关于刚性球形膜渗透渗透作用的工作与膜动力学模型结合起来，该模型解释了不可压缩脂双层内的变形和流动。我们的理论研究将最终重现和解释渗透梯度中囊泡快速运动的实验观察。最后，拟议的渗透性囊泡分类演示将为涉及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 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 proposed work 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, we 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, we will use lipid membranes incorporating aquaporin water channels to create high permeability vesicles that mimic native exosomes. The proposed 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. Our theoretical investigations will ultimately reproduce and explain experimental observations of rapid vesicle motions in osmotic gradients. Finally, the proposed 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.