Determination of Strain Rate Dependent Mechanical Behavior of Living and Fixed Osteocytes and Chondrocytes Using Atomic Force Microscopy and Inverse Finite Element Analysis

Abstract

The aim of this paper is to determine the strainratedependent mechanical behavior of living and fixed osteocytes and chondrocytes, in vitro. First, atomic force microscopy (AFM) was used to obtain the force–indentation curves of these single cells at four different strainrates. These results were then employed in inverse finite element analysis (FEA) using modified standard neoHookean solid (MSnHS) idealization of these cells to determine their mechanical properties. In addition, a FEA model with a newly developed spring element was employed to accurately simulate AFM evaluation in this study. We report that both cytoskeleton (CSK) and intracellular fluid govern the strainratedependent mechanical property of living cells whereas intracellular fluid plays a predominant role on fixed cells' behavior. In addition, through the comparisons, it can be concluded that osteocytes are stiffer than chondrocytes at all strainrates tested indicating that the cells could be the biomarker of their tissue origin. Finally, we report that MSnHS is able to capture the strainratedependent mechanical behavior of osteocyte and chondrocyte for both living and fixed cells. Therefore, we concluded that the MSnHS is a good model for exploration of mechanical deformation responses of single osteocytes and chondrocytes. This study could open a new avenue for analysis of mechanical behavior of osteocytes and chondrocytes as well as other similar types of cells.