Microrheology, stress fluctuations and active behavior of living cells

TL;DR

This study measures intrinsic strain fluctuations in living cells using a novel tracer correlation technique, revealing that the cytoskeleton behaves as a continuum with power-law rheology driven by random stress fields, and showing a nearly $1/rac{2}{ ext{omega}}^2$ power spectrum.

Contribution

It introduces a new experimental method to quantify cellular stress fluctuations and provides a theoretical framework for interpreting these in heterogeneous, actively driven media.

Findings

Cytoskeleton behaves as a continuum with power-law rheology.

Intracellular stress fluctuations follow a nearly $1/rac{2}{ ext{omega}}^2$ power spectrum.

Stress fluctuations are driven by a spatially random stress tensor field.

Abstract

We report the first measurements of the intrinsic strain fluctuations of living cells using a recently-developed tracer correlation technique along with a theoretical framework for interpreting such data in heterogeneous media with non-thermal driving. The fluctuations' spatial and temporal correlations indicate that the cytoskeleton can be treated as a course-grained continuum with power-law rheology, driven by a spatially random stress tensor field. Combined with recent cell rheology results, our data imply that intracellular stress fluctuations have a nearly $1/\omega^2$ power spectrum, as expected for a continuum with a slowly evolving internal prestress.