Study On Mechanical Properties Of Cells Based On Atomic Force Nanomanipulation

As a basic part of life,many scientists are involved in studying cells,exploring the changes in the biological and physical properties of cells from different aspects when they are in different physiological states.The cell size is so small that it cannot be observed directly on the macro scale.The atomic force microscope has the resolution of nano scale and is widely used in the field of microscopic testing.As one of the important factors affecting the mechanical properties of cells,the cytoskeleton plays an important role in maintaining cell morphology and responding to external stimulation.When the cell's environment changes,it will also change the cell's morphological structure and mechanical properties.In order to know the physiological state of cells,this dissertation is proposed to study the morphological and mechanical properties of cancer cells based on atomic force nanomanipulation on the microscopic scale,and to explore the differences between the morphological and mechanical properties of cells before and after carcinogenesis for providing experimental data which distinguish normal hepatic cells from hepatoma carcinoma cells.The influence of substrate on the mechanical properties of cells is explored.Due to the change in substrate stiffness,the cytoskeleton is rearranged and the distribution within the cell changes.In this dissertation,the morphological information and mechanical parameters of normal hepatic cells and hepatoma carcinoma cells are collected in the liquid phase,and the differences between normal cells and cancer cells are compared and analyzed.Atomic Force Microscope(AFM)is used to obtain denoising,correcting and equalizing the original image to obtain the small structural information.The results show that after the cell becomes cancerous,the height of the epatoma carcinoma cells become higher and the pseudopod structure is more abundant.Both the elastic modulus and the adhesion force show a tendency to decrease,which is closely related to the spread and metastasis of cancer cells.In this dissertation polydimethylsiloxane(PDMS)is selected as the substrate material in this work,and the substrates of different rigidities are obtained by adjusting the ratio of the main agent of PDMS and the curing agent.Based on the atomic force nanomanipulation,the substrates of different rigidities are obtained.A nanoindentation experiment is performed on the cells to obtain the elastic properties of the cells grown on the substrates of different rigidities.The results show that the probe tip is in contact with the substrate during the indentation process,which affects the accuracy of the obtained cell elastic modulus.The cross-correlation algorithm is used to remove the data affected by the substrate on the indentation curve,and then the remaining data segment is extended to obtain a substrate-free effect.The indentation curve is fitted based on the Sneddon contact model to obtain the elastic modulus without substrate influence;the change of the substrate stiffness affects the cell elastic modulus,and the cytoskeleton determines the cell elastic modulus.From this,the distribution of cell cytoskeleton changes with the substrate rigidity.It can be seen that the atomic force nanomanipulation provides an analytical method in cell diagnosis and the study of the mechanism of cell's environment.