title: Local viscoelasticity of living cells measured by rotational magnetic spectroscopy.
abstract: When submitted to a magnetic field, micron-size wires with superparamagnetic properties behave as embedded rheometers and represent interesting sensors for microrheology. Here we use rotational magnetic spectroscopy to measure the shear viscosity of the cytoplasm of living cells. We address the question of whether the cytoplasm is a viscoelastic liquid or an elastic gel. The main result of the study is the observation of a rotational instability between a synchronous and an asynchronous regime of rotation, found for murine fibroblasts and human cancer cells. For wires of susceptibility 3.6, the transition occurs in the range 0.01-1 rad s(-1). The determination of the shear viscosity (10-100 Pa s) and elastic modulus (5-20 Pa) confirms the viscoelastic character of the cytoplasm. In contrast to earlier studies, it is concluded that the interior of living cells can be described as a viscoelastic liquid, and not as an elastic gel.
authors.affiliation: Matière et Systèmes Complexes, UMR 7057 CNRS Université Denis Diderot Paris-VII, Bâtiment Condorcet, 10 rue Alice Domon et Léonie Duquet, 75205 Paris, France.
authors.forename: J-F
authors.initials: JF
authors.lastname: Berret
mesh_terms: D000818:Animals; D002462:Cell Membrane; D002468:Cell Physiological Phenomena; D003593:Cytoplasm / Q000502:physiology; D003599:Cytoskeleton / Q000378:metabolism; D004548:Elasticity; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D012212:Rheology / Q000295:instrumentation / Q000379:methods; D013057:Spectrum Analysis / Q000295:instrumentation* / Q000379:methods*; D014783:Viscosity