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. To do this, 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 AFM indenter the total indentation force has a linear relation with the indentation depth and the indenter radius in a fibrous network. 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 immediately under the indenter but, when has a certain distance with it. In addition, when the stress-fiber axis has a specific distance from the loading region, it has negligible effect on the local stiffness of the network. These results shed light on some aspects of the widely used AFM stiffness measurements of cells.