Effects Of Mechanical Properties Of F-actin Bundles On Cell Spread Dynamics

The mechanical properties of the F-actin bundles,which are a kind of subcellular structure,play an important role in the physiological process of cells,such as cell spreading and cell migration.Various types of skeletal substructures in cells are composed of F-actin bundles,including filopodia,stress fibers,and microvilli.The mechanical properties of F-actin bundles have not been considered in the current research on the cellular mechanical behavior,so the effect of the mechanical properties of F-actin bundles on the cellular spreading process is still unknown.However,a large number of experiments have proved that during the spread of these cytoskeletal substructures,the F-actin bundles show obvious nonlinear behavior when the tensile force is large.In order to solve the above problems,a new model was proposed to solve the dynamic process of cell spread based on Monte Carlo simulation.In the process of tension transmission,the F-actin bundles exhibits hyperelastic behavior when the tension is large.Firstly,the stress-strain relationship was obtained based on the finite deformation theory in continuum mechanics by considering the influence of the hyperelastic F-actin bundles on the spread motion of filaments on the substrate.By selecting proper strain energy function and material parameters,the relation between displacement and time of filopodia is obtained.It can be found that the filopodia spreading on the soft substrate exhibits a state between "load and fail" and "frictional slippage".In addition,by analyzing the movement process of filaments on the substrate,it can be found that the binding time of molecular bond and F-actin bundles changes,which is reflected in that the binding time is shortened when considering that the F-actin bundles are hyperelastic,that is,when the F-actin bundles show nonlinear behavior,the binding time is shortened.Therefore,F-actin bundles have a great influence on filopodia movement.