Stretching and heating cells with light—nonlinear photothermal cell rheology

Abstract

Stretching and heating are everyday experiences for skin and tissue cells. They are also standard procedures to reduce the risk for injuries in physical exercise and to relieve muscle spasms in physiotherapy. Here, we ask which immediate and long-term mechanical effects of such treatments are quantitatively detectable on the level of individual living cells. Combining versatile optical stretcher techniques with a well-tested mathematical model for viscoelastic polymer networks, we investigate the thermomechanical properties of suspended cells with a photothermal rheometric protocol that can disentangle fast transient and slow ‘inelastic’ components in the nonlinear mechanical response. We find that a certain minimum strength and duration of combined stretching and heating is required to induce long-lived alterations of the mechanical state of the cells, which then respond qualitatively differently to mechanical tests than after weaker/shorter treatments or merely mechanical preconditioning alone. Our results suggest a viable protocol to search for intracellular biomolecular signatures of the mathematically detected dissimilar mechanical response modes.

The Xenopus spindle is as dense as the surrounding cytoplasm

“…Differences in the RI between an object and its surrounding medium can be used to trap and deform the object (Guck et al, 2001). While experiments with optical stretchers (OSs) have been routinely used on a cellular level (Guck et al, 2005;Lautenschl€ ager et al, 2009;Huster et al, 2020), they have not been performed in in vitro reconstituted systems. We thus used a custom-built OS setup (Figure S2A) designed for Xenopus egg extract experiments.…”

High-throughput viscoelastic characterization of cells in hyperbolic microchannels

“…Cellular viscoelasticity has emerged as a central indicator of cell state and function, playing an increasingly significant role in disease characterization. [1][2][3][4][5][6] Established techniques such as micro-pipette aspiration, 1,7 atomic force microscopy, [8][9][10] or the optical stretcher, [11][12][13][14] while effective in revealing changes in cell deformability and relaxation times, operate on timescales of seconds with throughputs limited to a few hundred cells per hour max. This limitation makes them unsuitable for swift diagnostic applications.…”

High-throughput viscoelastic characterization of cells in hyperbolic microchannels

“…Cellular viscoelasticity has emerged as a central indicator of cell state and function, playing an increasingly significant role in disease characterization. [1][2][3][4][5][6] Established techniques such as micro-pipette aspiration, 1,7 atomic force microscopy, [8][9][10] or the optical stretcher, [11][12][13][14] while effective in revealing changes in cell deformability and relaxation times, operate on timescales of seconds with throughputs limited to a few hundred cells per hour max. This limitation makes them unsuitable for swift diagnostic applications.…”