Figure 1.

Measuring cell stiffness by nanoindentation: Principle, protocol, and recording. (A) nanoindenter used to measure resistance to deformation (stiffness). A spherical glass tip attached to a cantilever of known stiffness is used to indent a sample, e.g., a cell. Cantilever deformation is measured interferometrically and used to calculate the force applied to the sample. Green cell: Transfected cell expressing enhanced green fluorescent protein (EGFP) alone, or EGFP and the gene of interest. (B) downward movement of the indenter (motor displacement) beyond the cell surface leads to indentation of the cell and to cantilever bending. (C) force vs. indentation curves can be fitted using a Hertzian model for contact mechanics enabling to derive the effective Young’s modulus E_eff, which is 0.15 kPa in this example.