Numerical Study On Cell Motility Interacting With The Chemoattractant Flow In Microchannels

Beneficial to the steady control of flow properties and concentration gradient profiles attributed to the development of the microfluidic system,quantification of cell chemotaxis based on microfluidic devices could achieve on the scale of a single cell.However,normal experimental studies assumed that the concentration field was not affected by the existing cell,or by the impact of the cell motion.The effect of cell existence and motion on the concentration field around the cell is worth discussing because of the high sensitivity of cells to the concentration gradient.Morever,The direct visualization technology of chemokine gradient is still in its early stage so that the concentration gradient field around cells can not be observed at any time.Therefore,the influence of cell movement on its chemical microenvironment should be studied by numerical simulation.We used dynamic mesh model,moving boundary model and multiphase flow model to simulate the interactions of the cell translational,rotational and passive deformation movements with its chemical gradient flow.The influences of the chemical flow Peclet number,cell's translational velocity,2D and 3D models,cell's rotational velocity and direction,the fully sticky and unbinding models,single drop and compound drop models,different cortical tensions of cell membrane were investigated.Results showed as below:First of all,the actual chemotactic speed and direction change greatly when the cell moves to the original direction.Cell rotating in situ only has a greater influence on chemotactic direction.Morever the cell's two contrary rotational directions lead to contrary results.The chemotaxis experiment uses the microchannel device whose height can be as low as a cell diameter(except for bacteria and other small cells)so that 2D model is usually used in numerical simulation.2D model with circular cell is practically feasible due to simplicity,while 3D model with spherical cell is closer to reality.Numerical comparison showed that the 2D model can be used to analyze the cell's chemotactic tendency,but it also amplifies the cell's perturbation and then separation to its surrounding chemical flow.Then,a single cell's interactive chemotaxis in a micro chamber was simulated based on experimental measured chemotactic coefficient.The interactive chemotactic cell kept moving slightly upstream instead of upright crossing the interface.Finally,the effect of cell passive deformation is considered.When the wall shear stress is large for example: 6dyn/cm2,if the cell move near the wall or attached to a wall,the cell's trajectory in the future will remain in the vicinity of the wall surface.If the wall surface adhesion factor related to the cell surface,there may be a connection easily formed between the cell and the wall.Then the cell chemotaxis will begin the rolling and adhesion process.The cortical tension of cell membrane is smaller,the greater the cell deformation will be and the less the nucleus moves back.Cell passive deformation has small influence on the chemotaxis angle,but the part of the cell near the downstream may first begins active chemotactic deformation because the maximum and minimum concentration value positions move downward.This work may contribute to the development of chemotactic measurement method and precise evaluation on the cell's chemotactic sensitivity.