Interplay of Fluid Mechanics and Matrix Stiffness in Tuning the Mechanical Behaviors of Single Cells Probed by Atomic Force Microscopy.

Abstract

It is well known that both fluid mechanics and matrix stiffness present within the cellular microenvironments play an essential role in the physiological and pathological processes of cells. However, so far, knowledge of the interplay of fluid mechanics and matrix stiffness in tuning the mechanical behaviors of single cells is still extremely limited. Particularly, atomic force microscopy (AFM) is now an important and standard tool for characterizing the mechanical properties of single living cells. Nevertheless, studies of utilizing AFM to detect cellular mechanics are commonly performed in static medium conditions, which are unable to access the effects of fluidic media on cellular behaviors. Here, by integrating AFM with a fluidic cell medium device and hydrogel technology, the combined effects of fluid mechanics and matrix stiffness on cell mechanics were investigated. A fluidic medium device with tunable fluid mechanics was established to simulate the shear flow effects, and hydrogels were used to fabricate substrates with different stiffnesses for cell growth. Especially, the cantilever of the AFM probe was modified with a microsphere to indent cells for probing cell mechanics. Based on the established experimental platform, the elastic and viscous properties of single living cells grown on substrates with tunable matrix stiffness under fluidic microenvironments were quantitatively measured, and the remarkable alterations in the mechanical properties of cells were unraveled. The subcellular structure changes of cells in fluidic microenvironments were observed by fluorescence microscopy. Further, AFM morphological imaging was used to image living cells grown in fluidic medium conditions, and significant changes in the surface structure and roughness of cells were observed. The study provides a novel way to investigate the synergistic effects of fluid mechanics and matrix stiffness on the behaviors of single cells, which will benefit unveiling the underlying mechanical cues involved the interactions between microenvironments and cells.