Effect of Stress-Fiber Inclusion on the Local Stiffness of Cell Cytoskeleton Probed by AFM Indentation: Insights from a Discrete Network Model

In this paper, we analyze the effect of stress-fiber inclusion on the stiffness of an actin random network. We use a discrete random network model to analyze the elastic response of this system in terms of apparent Young’s modulus. First, we showed that for a flat-ended cylindrical indenter the total indentation force has a linear relation with the indentation depth and the indenter radius. Using this relation, we concluded that the stiffening effect of the stress-fiber on the fibrous network has a range of effectivity and surprisingly, the stiffening is not maximum when the stress-fiber is straight below the indenter but when it is a certain distance from it. These results shed light on some aspects of the widely used AFM stiffness measurements of cells.