Dissipative Particle Dynamics Simulation Of Cell Adhesion And Mechanical Response On Rigid Substrate

In the process of maintaining the normal life activities of living organisms,all cells are subjected to mechanical stimuli generated by the cells themselves and the extracellular environment.The response of cells to external mechanical stimuli is the basis for achieving their specific biological functions.Cells in an organism or cultured in vitro are essentially in a state of adhesion.In living organisms,all tissues and organs are subjected to forces generated by cell-extracellular matrix,cell-cell,and other interactions;in vitro experiments,cells adhere,migrate,and spread on the substrate,and cells are subjected to the force of the substrate.Therefore,quantitative analysis of the process of cell from suspension to adhesion has a certain significance to understand the biological behavior of adherent cells.It is helpful for us to understand the mechanical properties of cells by applying specific mechanical stimulation to adherent cells to study its mechanical response.In this dissertation,based on the principle of dissipative particle dynamics,a cell model that can characterize most eukaryotic cells is established by MATLAB,including cell membrane,nucleus,actin microfilament and intermediate filament.The simulation is realized by molecular dynamics software LAMMPS.The specific research includes the following two aspects :Firstly,under the generalized LJ(Lennard-Jones potential)potential describing the non-specific action of cell-substrate adhesion,the adherent cell was mechanically stimulated with high acceleration and the changes in cell morphology and the response of different cell components were analyzed.The change of high acceleration environment has various effects on the structure and function of cells.After the high acceleration stimulation reaches a stable state,the mechanical properties of the adherent cell model subjected to high acceleration are explored by nanoindentation method.Then the generic LJ potential is used to describe the adhesion potential energy between the cell and the substrate in the weak electrolyte environment.A certain adhesion zone is formed between the cell and the substrate.After the cell reaches the steady state of adhesion,different sizes of stress are applied to observe the change of the contact radius between the cell and the substrate.It is concluded that there is a limited contact radius when no external force is applied.When the compressive stress increases,the contact radius increases.When the tensile stress increases,the contact radius decreases and finally de-adhesive,and the cell-substrate contact radius became zero when de-adhesive.In the case of strong electrolytes,Pauli electrostatic repulsion and Van der Waals attraction work together to form two different attractive regions of between the cell and the substrate,as well as a repulsion barrier sandwiched between them.Therefore,this dissertation couples two LJ potential energies with different well depths and different cutoff radii to describe this potential energy,and applies different magnitudes of stress after the cell reaches the adhesion steady state to observe the contact radius between the cell and the substrate.When no external force is applied,there is already a finite contact radius.When the compressive stress increases,the contact radius increases.When the tensile stress increases,the contact radius decreases,and the contact radius is not zero when de-adhesive.In this study,we also simplified the cell model for the same simulation.In this dissertation,the mechanical response of adherent cells is illustrated by dissipative particle dynamics method,which can provide some reference for biomechanics and mechanobiology.