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Submitted: 10 July 2013 Modified: 13 September 2013
HERDIN Record #: R07-USC-13071011202763

Local viscoelasiticity of living mammalian cells


The ability of cells to deform or resist deformation affects several important factors of cell function. Most studies infer the elastic modulus of a living cells from the simultaneous measurements of forces and deformations exerted on the cell, based on Hertz model. However, the force-distance curves are affected by indenter-cell adhesion forces, and neglecting this effect may result in systematic errors in the determination of the Young's modulus of elasticity.

For the first time, the Hertz model was extended to include the effect of adhesion in the description of contact stiffness by using the Lennard-Jones potential to model the inter-molecular interaction between the probe surface and a living cell sample. The adhesion force derived from the potential gradient was incorporated to the Hertz relation, from which the value of the elastic modulus of the sample is obtained.

Our results show that during indentation of the intact cell, the adhesion force increases in proportion to the indentation depth. The increase in the slope of the force-indentation curves predicts a higher Young's modulus than the value obtained by the Hertz model neglecting adhesion force by up to 25% for decreasing size of molecules coating the probe. The model predicts the Young's modulus of a cell based on the radius of the probe, and the size and concentration of the molecules coating the surface. Thus, our approach provides precision on cell mechanics measurements without neglecting surface interactions that could be incorrectly neglected.

Publication Type
Thesis/Dissertations
Thesis Degree
MS
Specialization
Physics
Publication Date
October 2011
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