Utilizing nonlinearity of biopolymer matrix in both intracellular and extracellular spaces

Both living cell cytoskeleton and their extracellular matrix are constituted mainly by biopolymer matrices. The physical properties of these matrices are known to significantly impact cell behavior, such as cell morphology, migration, and stem-cell differentiation. However, cells also constantly reorganize these intracellular and extracellular structures during physiological processes; this is thought to also change the mechanics of these biopolymer matrices, which may then have an immediate impact on cell behavior. In this talk, I will present our recent progress on characterizing the drastic local nonlinear matrix stiffening induced by contraction of individual living cells inside a 3D biopolymer matrix, through direct micromechanical measurement. Moreover, I will introduce a method, called Nonlinear Stress Inference Microscopy, with which we can determine the cell-induced local matrix stress from nonlinear microrheology measurements inside various types of extracellular matrix in 3D. In addition, I will also introduce our recent progress on characterizing the significant role of cytoskeletal intermediate filament in determining nonlinear mechanics, strength, toughness, and stretchability of the mammalian cytoskeleton.