Approach and penetration of cell membranes by microswimmers and self-propelled particles

我们在这个项目中的目标是从理论和数值上获得自行式活性粒子接近细胞膜和穿透细胞膜的完整表征。该项目分为两个主要部分，概述如下。在物理接触发生之前，对膜附近活性粒子的行为和动力学的了解，是了解它们渗透到细胞内部的关键因素。因此，该项目的第一部分将致力于研究活跃粒子和微泳者的近膜动力学。为此，我们将使用流体的连续描述来解析地解决催化活性粒子由于其表面上的化学反应而在细胞膜附近移动的扩散潜水自推进机制。以往的研究仅集中在硬壁附近的自推进，而在可变形膜附近的定向运动到目前为止还没有被研究过。化学活性和膜弹性之间的物理相互作用有望导致非常丰富和可行的现象学。我们的计算将使用各种不同的模型游泳者，包括蠕动模型和远场流动的高阶表示。我们的理论预测将通过边界积分模拟来检验和验证。在项目的第二部分，我们将研究物理接触建立后，自推进粒子穿透细胞膜的过程。为此，我们将利用基于耗散粒子动力学方法的介观模拟方法来研究不同大小和形状的自扩散活性粒子进入脂质双层膜的物理进入。此外，我们还将探索流体和膜介导的活性粒子之间的相互作用。我们的模拟将补充和补充使用渐近分析和标度参数的理论计算，以便研究活性物品与细胞膜结合时的包裹机制。我们的合作者将在活细胞膜附近和通过活细胞膜进行相应的生物相容自推进实验。

Our goal in this project is to obtain a full characterization of the approach and penetration of cell membranes by self-propelled active particles both theoretically and numerically. The project is structured into two main parts as outlined below. The understanding of the behavior and dynamics of active particles near membranes, before physical contact takes place, is a crucial ingredient to understand their penetration into the cell interior. The first part of this project will therefore be devoted to the near-membrane dynamics of active particles and microswimmers. For this purpose, we will address analytically, using a continuum description of the fluid, the diffusiophoretic self-propulsion mechanism of a catalytically active particle moving due to a chemical reaction on its surface in the vicinity of a cell membrane. Previous works have only focused on self-propulsion near stiff walls and directed motion near deformable membranes has not been addressed so far. The physical interplay between the chemical activity and membrane elasticity is expected to lead to a very rich and viable phenomenology. Our calculations will be carried out using a variety of different model swimmers including the squirmer model and the higher order representation of the far-field flow. Our theoretical predictions will then be tested and validated by boundary integral simulations. In the second part of the project, we will investigate the penetration process of a self-propelled particle into a cell membrane after physical contact is established. For that aim, we will make use of mesoscopic simulations based on the dissipative particle dynamics method to investigate the physical entry of a self-diffusiophoretic active particle with different sizes and shapes into the lipid bilayer membrane. Additionally, we will explore the fluid- and membrane-mediated interactions between active particles. Our simulations will then be complemented and supplemented by theoretical calculations using asymptotic analysis and scaling arguments in order to examine the wrapping mechanism upon binding of an active article to the cell membrane. Corresponding experiments of biocompatible self-propulsion near and through living cell membranes will be performed by our collaborators.