Stress relaxation microscopy (STREM): Imaging mechanical force decay in cells

TL;DR

This paper introduces Stress Relaxation Microscopy (STREM), a new technique using scanning probes to measure and map the viscoelastic relaxation responses of cell surfaces, revealing insights into cell mechanics and heterogeneity.

Contribution

The study presents a novel scanning probe-based method to analyze cell biomechanics through force relaxation measurements and models cell surface behavior with a generalized Maxwell viscoelastic model.

Findings

Detected bimodal relaxation with characteristic times of 0.1s and 1s.

Identified relaxation processes linked to membrane and cytoskeleton.

Mapped mechanical heterogeneities in cell surfaces.

Abstract

We have developed a novel scanning probe-based methodology to study cell biomechanics. The time dependence of the force exerted by the cell surface on a scanning probe at constant local deformation has been used to extract local relaxational responses. The generalized Maxwell viscoelastic model that accounts for multi relaxations fully describes the mechanical behaviour of the cell surface that exhibits a bimodal relaxation. Within the range of tested forces (0.1-4 nN) a slow and a fast relaxation with characteristic times of 0.1 and 1s have been detected and assigned to rearrangements in the cell membrane and cytoskeleton cortex, respectively. Relaxation time mapping allows to simultaneously detect non-uniformities in membrane and cytoskeletal mechanical behaviour and can be used as both identifying and diagnosing tools for cell type and cell disease.