Magnetic wire as stress controlled micro-rheometer for cytoplasm viscosity measurements

TL;DR

This paper reviews magnetic wire-based microrheology techniques for measuring cytoplasm viscosity, demonstrating their ability to provide time-resolved, stress-controlled measurements in living cells with high potential for confined space applications.

Contribution

It introduces a magnetic wire-based method for stress-controlled microrheology, enabling quantitative, time-resolved viscosity measurements in cell cytoplasm, extending previous approaches.

Findings

Cytoplasm viscosity ranges between 10 and 100 Pas in various cell lines.

Magnetic wires can operate as stress-controlled rheometers for creep-recovery and steady shear tests.

The technique reveals strong temporal fluctuations in cell interior viscosity.

Abstract

We review here different methods to measure the bulk viscosity of complex fluids using micron-sized magnetic wires. The wires are characterized by length of a few microns and diameter of a few hundreds of nanometers. We first draw analogies between cone-and-plate rheometry and wire-based microrheology. In particular we highlight that magnetic wires can be operated as stress-controlled rheometers for two types of testing, the creep-recovery and steady shear experiments. In the context of biophysical applications, the cytoplasm of different cell lines including fibroblasts, epithelial and tumor cells is studied. It reveals that the interior of living cells can be described as a viscoelastic liquid with a static viscosity comprised between 10 and 100 Pas. We extend the previous approaches and show that the proposed technique can also provide time resolved viscosity data, which for cells display strong temporal fluctuations. The present work demonstrates the high potential of the magnetic wires for quantitative rheometry in confined espaces.