Complex thermorheology of living cells

Abstract

Temperature has a reliable and nearly instantaneous influence on mechanical responses of cells. As recently published, MCF-10A normal epithelial breast cells follow the time-temperature superposition (TTS) principle. Here, we measured thermorheological behaviour of eight common cell types within physiologically relevant temperatures and applied TTS to creep compliance curves. Our results showed that superposition is not universal and was seen in four of the eight investigated cell types. For the other cell types, transitions of thermorheological responses were observed at 36°C. Activation energies (E A ) were calculated for all cell types and ranged between 50 and 150 kJ mol −1 . The scaling factors of the superposition of creep curves were used to group the cell lines into three categories. They were dependent on relaxation processes as well as structural composition of the cells in response to mechanical load and temperature increase. This study supports the view that temperature is a vital parameter for comparing cell rheological data and should be precisely controlled when designing experiments.

Actin and microtubule networks contribute differently to cell response for small and large strains

“…14 Pa) resulting in a maximum relative deformation below 5% at the end of the stretch (figure 1(a)). Within this regime, a physiological temperature is maintained [46,47]. For 1200 mW (stress approx.…”

Optical stretching in continuous flows

“…We designed the setup in a minimalistic approach to change as few parameters as possible to keep the systems comparable. In this regard, we used the same lasers, optical fibers, and reservoirs as in previous studies concerning cancer research [4,8,39,59,60], various research questions of single cell rheology [38,40,41,61,62], and the principle of the Optical Stretcher as an optical rheometer for living cells [36,37,50]. The microfluidic surroundings have been adopted as far as possible, keeping the channel dimensions and path lengths, as well as flow velocities and pressure in the same order of magnitude.…”

“…This non-invasive high throughput measurement is fully automatized and has led to valuable insights for cancer research. It has been utilized in the analysis of primary cancer samples [3,4], cell line models for the malignant transformation [2] and the influence of drugs and other interferences with the metabolism of cancer cells [8,[37][38][39] and has even led to the development of the completely novel approach of thermorheology of living cells [40,41]. The possibility to measure several hundred cells within hours gives a huge statistical advantage that balances out the broad distribution of properties in biological specimen.…”

Detecting heterogeneity in and between breast cancer cell lines

“…The general setup of the optical stretcher (OS) is described in (Lincoln et al 2007b) with additional improvements to the microfluidics, the computer̵ -controlled stretching processes, and the thermally controlled stage described in detail in (Lincoln et al 2007b;Guck et al 2001;Schmidt et al 2015). The mechanical properties of cells were determined by guiding the cell suspension into the automated microfluidic OS where single cells are consecutively trapped and stretched.…”