Measuring Viscoelastic Properties of Living Cells

Abstract

Precise measurement of mechanical properties of living cells is important in understanding their mechanics-biology relations. In this study, we adopted the atomic force microscope to measure the creep deformation and stress relaxation of six different human cell lines. We examined whether the measured creep and relaxation trajectories satisfy a verification relation derived based on the linear viscoelastic theory. We compared the traditional spring-dashpot and the newly developed power-law-type constitutive relations in fitting the experimental measurements. We found that the human normal liver (L02), hepatic cancer (HepG2), hepatic stellate (LX2) and gastric cancer (NCI-N87) cell lines are linear viscoelastic materials, and human normal gastric (GES-1) and gastric cancer (SGC7901) cell lines are nonlinear due to failing in satisfying the verification relation for linear viscoelastic theory. The three-parameter power-law-type constitutive relation can fit the experimental measurements better than that of the five-parameter classical spring-dashpot.

Effects of Lipid Deposition on Viscoelastic Response in Human Hepatic Cell Line HepG2

“…The AFM indentation assay and the theoretical model were conducted as previously described ( Bu et al, 2019 ). Cells were seeded and treated in sterilized 35-mm petri dishes.…”

“…Considering that the cytoplasm is rich in different molecules such as lipids, carbohydrates, and proteins, dynamic changes in cell composition may be reflected in energy dissipation and time-dependent deformations. Our previous work has showed the viscoelastic differences between different cells in the liver ( Bu et al, 2019 ). Therefore, the viscoelastic parameters may be used as indicators to distinguish cells with different lipid depositions.…”

“…In this work, an oleic acid (OA)-induced hepatocyte deposition model with a gradient change was used to simulate intracellular lipid deposition. Following our previous study ( Bu et al, 2019 ), we adopted a three-parameter power-law-type constitutive relation to fit the experimental measurements, and this method is better than the five-parameter classical spring-dashpot. The combination of the proposed power law expression and AFM indentation measurements on the creep compliance and relaxation modulus will provide a unique way in determining the viscoelastic properties of the HepG2 cells with different lipid deposition levels.…”

Biomechanical Sensing using Gas Bubbles Oscillations in Liquids and Adjacent Technologies: Theory and Practical Applications

“…However, despite technical maturity of a number of current techniques suitable 313 for the investigation of mechanical properties of biological cells[110,117,129,[131][132][133][134][135][136][137], 314 most of these techniques measure those of cell membranes only or of cell membranes 315 combined with cytoskeleton. As a result, the information about mechanical properties of 316 the interior of an individual cell may be difficult to gain.…”

Preface to the “Soft Matter Mechanics” Special Issue of Acta Mechanica Solida Sinica

“…Ye et al [4] explored the torsion instability of an anisotropically growing tube with fiber reinforcement that mimics tubular organs. Bu et al [5] examined the creep deformation and stress relaxation of different human cells with the atomic force microscope. Based on the Helfrich membrane theory, Tang et al [6] performed a theoretical investigation to explore the mechanical behaviors of pressurized elastic fluid nanovesicles indented by a rigid cylindrical punch.…”