Viscoelastic properties of suspended cells measured with shear flow deformation cytometry

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.