Computation of Adherent Cell Elasticity for Critical CellBead Geometry in Magnetic Twisting Experiments. Annals of Biomedical Engineering

Abstract—Quantification of the cell elastic modulus is a central issue of micromanipulation techniques used to analyze the me-chanical properties of living adherent cells. In magnetic twisting cytometry (MTC), magnetic beads of radius R, linked to the cell cytoskeleton through transmembrane receptors, are twisted. The relationships between imposed external torque and measured re-sulting bead rotation or translation only provide values of the ap-parent cell stiffness. Thus, specific correcting coefficients have to be considered in order to derive the cell elastic modulus. This issue has been highlighted in previous studies, but general relationships for handling such corrections are still lacking while they could help to understand and reduce the large dispersion of the reported values of cell elastic modulus. This work establishes generalized abacuses of the correcting coefficients from which the Young’s modulus of a cell probed by MTC can be derived. Based on a 3D finite element analysis of an hyperelastic (neo-Hookean) cell, we show that the dimensionless ratio hu/2R, where hu is the cell height below the bead, is an essential parameter for quantification of the cell elas-ticity. This result could partly explain the still intriguing question of the large variation of measured elastic moduli with probe size. Keywords—Cytomechanical model, Finite element method, Magnetic twisting cytometry, Correcting coefficients, Cell stiffness