Berlin 2005 – scientific programme

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AKB: Biologische Physik

AKB 15: Cell Mechanics and Rheology

AKB 15.2: Talk

Friday, March 4, 2005, 12:00–12:15, TU H2013

A Characteristic Relaxation Time of Suspended Cells Revealed by Optical Rheology — •Falk Wottawah, Stefan Schinkinger, Bryan Lincoln, Maren Romeyke, Josef Käs und Jochen Guck — Institute for Soft Matter Physics, University of Leipzig, Linnéstrasse 5, 04103 Leipzig

The measurement of the mechanical properties of individual cells has received much attention in recent years. Whole cell rheology of individual suspended fibroblasts in an optical stretcher displays a single passive relaxation, arising from transiently crosslinked polymers. This result is in stark contrast to recent rheological measurements on adherent cells. The measured frequency-dependent complex shear modulus reveals characteristic viscoelastic signatures of the underlying cytoskeleton and its dynamic microscopic properties. These are consistent with an isotropic actin cortex underlying the cellular plasma membrane. The elastic to fluid transition occurs at a relaxation time of 2.8±0.5 s, coinciding with unbinding times of actin crosslinking proteins. Elastic contributions from slowly relaxing entangled actin filaments are negligible. The symmetrical geometry of suspended cells, in contrast to adherent cells, ensures a minute statistical variability. Yet, distinctive viscoelastic features between different cell types are seen. Mechanical stimuli on longer time scales of minutes trigger active structural responses with internal forces on the order of 1 nN.