Fractional viscoelastic models for power-law materials

Bonfanti, Alessandra; Kaplan, Jonathan; Charras, Guillaume; Kabla, Alexandre

doi:10.1039/d0sm00354a

Cited by 240 publications

(211 citation statements)

References 149 publications

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“…In order to obtain a major understanding of these results, we propose a simple phenomenological model that describes the mechanical response of the cell as the result of mechanical elements arranged in parallel representing the contribution of myosin II activity, the apical actin network, and the rest of cell components, mostly the cytoplasm. Each mechanical element exhibits PLR response and it is represented as "springpot" instead of the traditional combination of springs and dashpots used to describe viscoelastic materials 48 (Fig. 5A).…”

Section: Resultsmentioning

confidence: 99%

Effects of energy metabolism on the mechanical properties of breast cancer cells

et al. 2020

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Tumorigenesis induces actin cortex remodeling, which makes cancerous cells softer. Cell deformability is largely determined by myosin-driven cortical tension and actin fiber architecture at the cell cortex. However, it is still unclear what the weight of each contribution is, and how these contributions change during cancer development. Moreover, little attention has been paid to the effect of energy metabolism on this phenomenon and its reprogramming in cancer. Here, we perform precise two-dimensional mechanical phenotyping based on power-law rheology to unveil the contributions of myosin II, actin fiber architecture and energy metabolism to the deformability of healthy (MCF-10A), noninvasive cancerous (MCF-7), and metastatic (MDA-MB-231) human breast epithelial cells. Contrary to the perception that the actin cortex is a passive structure that provides mechanical resistance to the cell, we find that this is only true when the actin cortex is activated by metabolic processes. The results show marked differences in the nature of the active processes that build up cell stiffness, namely that healthy cells use ATP-driven actin polymerization whereas metastatic cells use myosin II activity. Noninvasive cancerous cells exhibit an anomalous behavior, as their stiffness is not as affected by the lack of nutrients and ATP, suggesting that energy metabolism reprogramming is used to sustain active processes at the actin cortex.

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Section: Resultsmentioning

confidence: 99%

Effects of energy metabolism on the mechanical properties of breast cancer cells

et al. 2020

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“…1b), are difficult to interpret and compare. Therefore, we model the real (G') and imaginary part (G") of the shear modulus in terms of a fractional two element approach using a generalized Kelvin-Voigt (GKV) model [22]: (Fig. 1b).…”

Section: Resultsmentioning

confidence: 99%

Intracellular softening and fluidification reveals a mechanical switch of cytoskeletal material contributions during division

Hurst¹,

Vos

Betz

2021

Preprint

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The life and death of an organism depends largely on correct cell division. While the overall biochemical signaling and morphological processes during mitosis are well understood, the importance of mechanical forces and material properties is only just starting to be discovered. Recent studies of global cell stiffening during cell division may imply an understanding of the cytosol mechanics that is mistaken. Here we show that in contrast to the stiffening process in the cell cortex, the interior of the cell undergoes a softening and fluidification that is accompanied by a decrease of active forces driving particle mobility. Using optical tweezers-based microrheology we capture the complex active and passive material state of the cytoplasm using only six relevant parameters. We demonstrate that the softening occurs because of a surprising role switch between microtubules and actin, where the intracellular, actin-based mechanics is largely controlled by a formin-mediated network.

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“…However, a single fractional element is often insufficient to describe the experimentally found differences in the power-law exponents of the storage and the loss modulus. [14][15][16][17] One key finding of the work presented here is that microrheology of ECs can be well modelled by the generalized Kelvin-Voigt model comprised of two fractional elements in parallel.…”

Section: Introductionmentioning

confidence: 86%

Microchip based microrheology via Acoustic Force Spectroscopy shows that endothelial cell mechanics follows a fractional viscoelastic model

Nguyen

Brandt

Betz

2020

Preprint

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AbstractActive microrheology is one of the main methods to determine the mechanical properties of cells and tissue, and the modelling of the viscoelastic properties of cells and tissue is under heavy debate with many competing approaches. Most experimental methods of active microrheology such as optical tweezers or atomic force microscopy based approaches rely on single cell measurements, and thus suffer from a low throughput. Here, we present a novel method for cell based microrheology using acoustic forces which allows multiplexed measurements of several cells in parallel. Acoustic Force Spectroscopy (AFS) is used to generate multi-oscillatory forces in the range of pN-nN on particles attached to primary human umbilical vein endothelial cells (HUVEC) cultivated inside a microfluidic chip. While the AFS was introduced as a single-molecule technique to measure mechanochemical properties of biomolecules, we exploit the AFS to measure the dynamic viscoelastic properties of cells exposed to different conditions, such as flow shear stresses or drug injections. By controlling the force and measuring the position of the particle, the complex shear modulus G*(ω) can be measured continuously over several hours. The resulting power-law shear moduli are consistent with fractional viscoelastic models. In our experiments we confirm a decrease in shear modulus after perturbing the actin cytoskeleton via cytochalasin B. This effect was reversible after washing out the drug. Although these measurements are possible, we provide critical information regarding the AFS as a measurement tool showing its capabilities and limitations. A key result is that for performing viscoelastic measurements with the AFS, a thorough calibration and careful data analysis is crucial, for which we provide protocols and guidelines.

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Fractional viscoelastic models for power-law materials

Abstract:
Power law materials exhibit a rich range of behaviours interpolating continuously from the linear elastic to the linear viscous responses.

Cited by 240 publications

References 149 publications

Effects of energy metabolism on the mechanical properties of breast cancer cells

Effects of energy metabolism on the mechanical properties of breast cancer cells

Intracellular softening and fluidification reveals a mechanical switch of cytoskeletal material contributions during division

Microchip based microrheology via Acoustic Force Spectroscopy shows that endothelial cell mechanics follows a fractional viscoelastic model

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Fractional viscoelastic models for power-law materials

Abstract: Power law materials exhibit a rich range of behaviours interpolating continuously from the linear elastic to the linear viscous responses.

Cited by 240 publications

References 149 publications

Effects of energy metabolism on the mechanical properties of breast cancer cells

Effects of energy metabolism on the mechanical properties of breast cancer cells

Intracellular softening and fluidification reveals a mechanical switch of cytoskeletal material contributions during division

Microchip based microrheology via Acoustic Force Spectroscopy shows that endothelial cell mechanics follows a fractional viscoelastic model

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Product

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Abstract:
Power law materials exhibit a rich range of behaviours interpolating continuously from the linear elastic to the linear viscous responses.