Characterizing in situ poroelastic properties of cytoplasm by the translation of a rigid spherical inclusion

Poroelasticity of cytoplasm is a rate- and size-dependent biphasic material behavior that reflects the normal activities and pathological states of cells, mainly caused by the migration of fluid molecules and the deformation of porous solid skeleton (protein scaffold). While micro/nano-indentation tests have been extensively used to characterize the poroelasticity of a cell, characterizing the in situ poroelasticity of cytoplasm remains elusive. In this study, based on the theory of the translation of a rigid spherical inclusion, we proposed a new method to characterize the in situ poroelasticity of cytoplasm. Based on data from optical/magnetic tweezers tests, we estimated three key poroelasticity parameters—shear modulus, Poisson ratio and diffusion coefficient—of cytoplasm for a variety of cells, including cardiomyocytes, endothelial cells of bovine capillary, and fibroblasts. The proposed method provides a powerful tool for in situ measurement of poroelastic properties of cytoplasm via optical/magnetic tweezers.