Berlin 2012 – scientific programme

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BP: Fachverband Biologische Physik

BP 27: Posters: Cytoskeletal Filaments

BP 27.1: Poster

Thursday, March 29, 2012, 17:30–19:30, Poster A

Cell plasticity is tightly linked to elastic stresses in the cytoskeleton — •Achim Schilling, Navid Bonakdar, Michael Kuhn, Richard Gerum, and Ben Fabry — Biophysics Group, FAU

Cells show pronounced non-linear visco-elastic and visco-plastic properties under large deformations and forces that are important for protecting the cell against mechanical damage. We used a high-force magnetic tweezer setup to deliver unidirectional forces with high precision of up to 30 nN to fibronectin-coated magnetic 5um beads bound to cell surface adhesion receptors. To probe cells with bidirectional forces, the cell culture plate was placed on a rotational/translational stage such that the magnetic bead remained at a constant distance to the magnetic tweezer tip after a 180° rotation. Bead displacements were measured during application of force steps (creep response) and after the force was removed (recovery response). With increasing force magnitude, the cells stiffened, and the recovery became increasingly incomplete, indicating the emergence of plastic behavior. This plasticity was a constant fraction (20%) of the total bead displacement. We attribute the plastic behavior to a buildup of excess slack in the cytoskeletal fibers; when the force direction was suddenly reversed, the beads jumped by twice the slack length in the opposite direction. The creep and the recovery response were fully characterized by a simple power-law vs. time with only 2 force-dependent parameters (elasticity and creep exponent). Our results show that plastic energy dissipation during large cell deformations is tightly linked to elastic stress dissipation and provides additional protection against mechanical damage.