Mechanical characterization of adherent cells with atomic force microscopy

Abstract

Changes in cell’s mechanical properties are potential to identify certain types of cancer. Therefore, the mechanical characterization, including experiments and parameter modeling, is essential to prove this idea for clinical applications. the micropipette aspiration method combined with simple local linear elastic models is widely used but this approach has difficulties to be used to adherent cells, which stick to the substrate. In this thesis, indentation experiments on adherent cells were conducted by an Atomic Force Microscope (AFM) and the results were analyzed to characterize the mechanical properties of adherent cells. Single cell indentation experiments were performed on cell lines including HegG2, a hepatocarcinoma cell, and THLE2, a normal hepatocytes. In addition, the actin disrupted experiments were also implemented to verify effects of cellular membrane and cytoplasm, For identifying nonlinear mechanical properties of the cells, the nonlinear FE model including topological information of the cells and indenters was developed and simulated with the optimization algorithm. FE model considering both membrane and cytoplasm layer was also developed from the actin disrupted experiment results. The results of this study can be summarized as; 1) The Young’s modulus of each cell was 16.3 ± 3.4 kPa and 1.49 ± 0.45 kPa from Hertz-Sneddon model. 2) Due to the weight factor’ change of actin filament, composition, kinetics, or cross-linking between actin filaments could be altered in cancer process. 3) The parameter is similar to the elastic modulus estimated by Hertz-Sneddon model as a result of the optimization process