Nanoscale Viscosity of Cytoplasm Is Conserved in Human Cell Lines

Abstract

Metabolic reactions in living cells are limited by diffusion of reagents in the cytoplasm. Any attempt to quantify the kinetics of biochemical reactions in the cytosol should be preceded by careful measurements of the physical properties of the cellular interior. The cytoplasm is a complex, crowded fluid characterized by effective viscosity dependent on its structure at a nanoscopic length scale. In this work, we present and validate the model describing the cytoplasmic nanoviscosity, based on measurements in seven human cell lines, for nanoprobes ranging in diameters from 1 to 150 nm. Irrespective of cell line origin (epithelial–mesenchymal, cancerous–noncancerous, male–female, young–adult), we obtained a similar dependence of the viscosity on the size of the nanoprobes, with characteristic length-scales of 20 ± 11 nm (hydrodynamic radii of major crowders in the cytoplasm) and 4.6 ± 0.7 nm (radii of intercrowder gaps). Moreover, we revealed that the cytoplasm behaves as a liquid for length scales smaller than 100 nm and as a physical gel for larger length scales.

Biocompatible Ir(III) Complexes as Oxygen Sensors for Phosphorescence Lifetime Imaging

“…These data are in line with the dynamic character of the phosphorescence quenching in the model viscous media. However, the effect of viscosity onto emission lifetime is relatively small and does not exceed 10% in the interval studied, which evidently covers the values typical for the intracellular media [ 55 , 56 , 57 ]. Comparison of the lifetime data obtained in cuvette using spectrometer and those obtained in PLIM experiments ( Table S6 ) showed that they coincide within the margin of experimental uncertainty.…”

Dynamic Cellular Cartography: Mapping the Local Determinants of Oligodendrocyte Transcription Factor 2 (OLIG2) Function in Live Cells Using Massively Parallel Fluorescence Correlation Spectroscopy Integrated with Fluorescence Lifetime Imaging Microscopy (mpFCS/FLIM)

“…We have also shown that noninteracting molecules smaller than 5 nm, e.g., eGFP, diffuse without significant hindrance through the entire cell (Figures and S15), while molecules/molecular complexes that are larger than 10 nm, such as eGFP tet , largely reside in the cytoplasm where their diffusion is hindered by internal membranes in the cytoplasm (Figures S13 and S15). These findings are in line with experimental findings reported in the literature and with theoretical findings showing that the cytoplasm behaves to a very large extent as a liquid phase for length scales shorter than 100 nm and as a dynamically structured macromolecular matrix for longer length scales . They are also important for the validation of our instrument performance.…”

“…These findings are in line with experimental findings reported in the literature and with theoretical findings showing that the cytoplasm behaves to a very large extent as a liquid phase for length scales shorter than 100 nm and as a dynamically structured macromolecular matrix for longer length scales. 63 They are also important for the validation of our instrument performance.…”

Quantitative Methodologies to Dissect Immune Cell Mechanobiology

“…Recent work by Kwapiszewska et al used PTM in combination with two different fluorescence correlation spectroscopy (FCS) modes to quantify the mechanical properties of cells, such as the nanoscale viscosity of the cytoplasm [ 59 , 60 ]. Interestingly, the study revealed length-scale-dependent viscosity profiles, which were mostly independent of the cell type, as well as the origin of the cells, such as age, gender, disease or tissue.…”