Characterization of cellular elastic modulus using structure based double layer model.

The mechanical characterization of cells is important for understanding cellular behavior and physiological functions. We used atomic force microscopy (AFM) to obtain a force-displacement curve and estimate the elastic modulus of hepatocellular carcinoma cells (HEP-G2) utilizing both linear Hertz-Sneddon (HS) and non-linear elastic models. In order to overcome the limitations of HS model, which assumes a linear homogeneous cell body, a cell is modeled as a double-layered body with an outer cytoplasmic layer made mostly of interconnected fibers of cytoskeleton proteins and a nucleus. By disrupting all cytoskeletal protein networks, we estimate the elastic modulus of the core nucleus using FEM for a single ellipsoid. Based on the nucleic modulus and cellular dimensions found by 3D confocal imaging, we develop a novel double-layered cellular (DLC) finite element model. The DLC model provides a more reliable estimate of the elastic modulus of the cell than conventionally used HS model and correlates closely with experimental results.