Elasticity Spectra as a Tool to Investigate Actin Cortex Mechanics

Abstract

Background The mechanical properties of single living cells have proven to be a powerful marker of the cell physiological state. The use of nanoindentation-based single cell force spectroscopy provided a wealth of information on the elasticity of cells, which is still largely to be exploited. The simplest model to describe cell mechanics is to treat them as a homogeneous elastic material and describe it in terms of the Young's modulus. Beside its simplicity, this approach proved to be extremely informative, allowing to assess the potential of this physical indicator towards high throughput phenotyping in diagnostic and prognostic applications. Results Here we propose an extension of this analysis to explicitly account for the properties of the actin cortex. We present a method, the Elasticity Spectra, to calculate the apparent stiffness of the cell as a function of the indentation depth and we suggest a simple phenomenological approach to measure the thickness and stiffness of the actin cortex, in addition to the standard Young's modulus. Conclusions The Elasticity Spectra approach is tested and validated on a set of cells treated with cytoskeleton-affecting drugs, showing the potential to extend the current representation of cell mechanics, without introducing a detailed and complex description of the intracellular structure.

FluidFM for single-cell biophysics

“…3(b)). Experimental results have significantly shown the capabilities of the FluidFM-prepared spherical tips in sensing the mechanical properties of cells [65]. A notable point is that the sphere sucked to the FluidFM cantilever can be exchanged in the working medium when probing cells.…”

“…In this review, the achievements in single-cell manipulations and detections using FluidFM in the past decade since its invention have been summarized, considerably demonstrating that FluidFM has become a powerful multifunctional toolbox for single-cell biophysics, including various single-cell manipulations (e.g., three-dimensional operation [48], cell sorting [56], cell patterning [57], exchangeable colloidal probe for cell indenting [65], drug dispensing & injection with very small volumes [25], cell nucleus injection [68], individual virus stimulation [67], and cellular extraction [70]), single-cell force spectroscopy (e.g., cell-substrate interaction measurements [82] and cell-cell interaction measurements [95]), and single-cell electrophysiology (e.g., simultaneous mechanical force and ionic current recording for patch clamp [106], force-controlled SICM [114], and single-molecule sensing based on scanning nanopore microscopy [49]), providing novel possibilities for investigating the behaviors of single living cells, which is significantly meaningful for the studies of revealing the underlying molecular mechanisms guiding cellular physiological/pathological processes.…”