Viscoelastic properties of suspended cells measured with shear flow deformation cytometry

Abstract

Numerous cell functions are accompanied by phenotypic changes in viscoelastic properties, and measuring them can help elucidate higher-level cellular functions in health and disease. We present a high-throughput, simple and low-cost microfluidic method for quantitatively measuring the elastic (storage) and viscous (loss) modulus of individual cells. Cells are suspended in a high-viscosity fluid and are pumped with high pressure through a 5.8 cm long and 200 μm wide microfluidic channel. The fluid shear stress induces large, near ellipsoidal cell deformations. In addition, the flow profile in the channel causes the cells to rotate in a tank-treading manner. From the cell deformation and tank treading frequency, we extract the frequency-dependent viscoelastic cell properties based on a theoretical framework developed by R. Roscoe that describes the deformation of a viscoelastic sphere in a viscous fluid under steady laminar flow. We confirm the accuracy of the method using atomic force microscopy-calibrated polyacrylamide beads and cells. Our measurements demonstrate that suspended cells exhibit power-law, soft glassy rheological behavior that is cell cycle-dependent and mediated by the physical interplay between the actin filament and intermediate filament networks.

Calcium supplementation of bioinks reduces shear stress-induced cell damage during bioprinting

“…During the channel passage, cells were imaged at high speed (500 fps) at the midsection of the channel, using a 40×/0.6 NA dry objective on an epifluorescence microscope (Leica DM IL, Leica, Wetzlar, Germany) equipped with a complementary metal-oxide semiconductor (CMOS) camera (acA720-520um, Basler, Germany) and a 100 mW diode laser (473 nm) in the bright-field and epifluorescence mode. For each recording, the velocity profile, shear rate profile, cell mechanical parameters (stiffness and fluidity) and hydrogel rheology (zeroshear-stress viscosity, characteristic shear rate for the onset of shear thinning, and shear-thinning exponent) were measured as previously described [29].…”

“…To test whether FM 1-43 also allows us to visualize plasma membrane damages under the typical flow conditions in a printing needle during biofabrication, we subjected NIH/3T3 cells (0.8-1.25 × 10 6 ml −1 ) suspended in 3% alginate containing FM 1-43 to laminar flow using a custom-designed microfluidic cell deformation cytometer (figure S1supplementary information) [7,29]. During capillary passage (6 bar), cells were imaged in bright-field and epifluorescence mode (473 nm) at high temporal resolution (500 Hz, 30 µs exposure time).…”