Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 24: Cell Mechanics (in vivo)

BP 24.8: Talk

Thursday, March 29, 2007, 12:00–12:15, H44

Single fibroblast viscoplasticity: elastic stiffening and kinematic hardening — •Pablo Fernandez^{1, 2}, Pramod Pullarkat¹, and Albrecht Ott¹ — ¹Universität Bayreuth, Germany — ²Present address: Technische Universität München, Germany

The deep biological relevance of mechanics is well illustrated by features such as cell locomotion, contractility, and mechanotransduction. The advent of single-cell rheology brings hope of a physical understanding of these phenomena. We report that the mechanical response of single 3T3 fibroblasts to uniaxial extension in the 1–100% range obeys a remarkably simple and robust phenomenology. Below 10% deformation cells exhibit a previously reported, stress-stiffening master relation probed with sinusoidal oscillations. Beyond 10% stretch, deformations at a constant rate in a 0.03–3 µm/s range always exhibit pure plastic flow. The plastic deformation translates the elastic region, a behaviour known as kinematic hardening. Fixing the cells abolishes the plastic response. Then the force-length relation shows dramatic stiffening, the integral of the previously described master-relation. Thus 2 key features summarise fibroblast mechanical behaviour: exponential elastic stiffening and viscoplastic kinematic hardening.