Feedback-tracking microrheology in living cells

Kenji Nishizawa, Marcel Bremerich, Heev Ayade, Christoph F. Schmidt, Takayuki Ariga, Daisuke Mizuno

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Living cells are composed of active materials, in which forces are generated by the energy derived from metabolism. Forces and structures self-organize to shape the cell and drive its dynamic functions. Understanding the out-of-equilibrium mechanics is challenging because constituent materials, the cytoskeleton and the cytosol, are extraordinarily heterogeneous, and their physical properties are strongly affected by the internally generated forces. We have analyzed dynamics inside two types of eukaryotic cells, fibroblasts and epithelial-like HeLa cells, with simultaneous active and passive microrheology using laser interferometry and optical trapping technology. We developed a method to track microscopic probes stably in cells in the presence of vigorous cytoplasmic fluctuations, by using smooth three-dimensional (3D) feedback of a piezo-actuated sample stage. To interpret the data, we present a theory that adapts the fluctuation-dissipation theorem (FDT) to out-of-equilibrium systems that are subjected to positional feedback, which introduces an additional nonequilibrium effect. We discuss the interplay between material properties and nonthermal force fluctuations in the living cells that we quantify through the violations of the FDT. In adherent fibroblasts, we observed a well-known polymer network viscoelastic response where the complex shear modulus scales as G* º(−iw)3/4. In the more 3D confluent epithelial cells, we found glassy mechanics with G* º(−iw)1/2 that we attribute to glassy dynamics in the cytosol. The glassy state in living cells shows characteristics that appear distinct from classical glasses and unique to nonequilibrium materials that are activated by molecular motors.

Original languageEnglish
Article number1700318
JournalScience Advances
Volume3
Issue number9
DOIs
Publication statusPublished - Jan 1 2017

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Mechanics
Cytosol
Fibroblasts
Optical Tweezers
Interferometry
Cell Shape
Eukaryotic Cells
Cytoskeleton
HeLa Cells
Energy Metabolism
Glass
Polymers
Lasers
Epithelial Cells
Technology

All Science Journal Classification (ASJC) codes

  • General

Cite this

Nishizawa, K., Bremerich, M., Ayade, H., Schmidt, C. F., Ariga, T., & Mizuno, D. (2017). Feedback-tracking microrheology in living cells. Science Advances, 3(9), [1700318]. https://doi.org/10.1126/sciadv.1700318

Feedback-tracking microrheology in living cells. / Nishizawa, Kenji; Bremerich, Marcel; Ayade, Heev; Schmidt, Christoph F.; Ariga, Takayuki; Mizuno, Daisuke.

In: Science Advances, Vol. 3, No. 9, 1700318, 01.01.2017.

Research output: Contribution to journalArticle

Nishizawa, K, Bremerich, M, Ayade, H, Schmidt, CF, Ariga, T & Mizuno, D 2017, 'Feedback-tracking microrheology in living cells', Science Advances, vol. 3, no. 9, 1700318. https://doi.org/10.1126/sciadv.1700318
Nishizawa K, Bremerich M, Ayade H, Schmidt CF, Ariga T, Mizuno D. Feedback-tracking microrheology in living cells. Science Advances. 2017 Jan 1;3(9). 1700318. https://doi.org/10.1126/sciadv.1700318
Nishizawa, Kenji ; Bremerich, Marcel ; Ayade, Heev ; Schmidt, Christoph F. ; Ariga, Takayuki ; Mizuno, Daisuke. / Feedback-tracking microrheology in living cells. In: Science Advances. 2017 ; Vol. 3, No. 9.
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