A model for magnetic bead microrheometry

Mechanical properties of a cell play an important role in the essential cellular functions such as mechanotransduction, shape stability, motility, apoptosis and DNA synthesis. The viscoelasticity of the cytoplasm is a crucial physical parameter for many cellular processes. In this work, we develop a new model allowing us to determine viscoelastic parameters of the cytoplasm (shear elastic modulus, the effective viscosities and the strain relaxation time) of cells. The model describes the rotation of magnetic chains consisting of 3–4 nanoparticles under the influence of rotating external magnetic fields. As the bead rotates, mechanical stresses opposing that rotation are developed within the cell and from the measured angular displacement of the bead, we can extract the viscoelastic parameters by fitting the experimental data with our model. The model gives the possibility for a general description of various phenomena in magnetorheological suspensions.