INFLUENCE OF THE FIXED NEGATIVE CHARGES ON THE MEASURED POISSON'S RATIO, YOUNG'S MODULUS AND ELECTRICAL RESPONSE OF ARTICULAR CARTILAGE

摘要

Under physiological conditions, the solid extracellular matrix (ECM) of articular cartilage derives negative charges from its proteoglycan content. The load-deformation behavior of the tissue (i.e., its apparent mechanical property) comes from not only the intrinsic matrix properties, but also these charges that are attached to the matrix. Study shows that in 1D configurations (such as confined compression), at equilibrium, the osmotic pressure associated with these fixed charges may contribute as much as 50% of the apparent compressive modulus. Uniaxial loading under an unconfined compression condition has been among the simplest configurations to study the mechanical properties of cartilage. It has also been widely used in tissue engineering to study explants and gel-cell-complexes. Young's modulus and Poisson's ratio are the two material coefficients that describe the ECM, which is assumed to be an isotropic, linearly elastic material. These coefficients are necessary for a multi-dimensional stress-strain analysis of cartilage in real joint loadings and in vitro explant studies. The purpose of this study is to investigate the contribution of the fixed charges to the apparent material properties (i.e., the apparent Young's modulus and apparent Poisson's ratio at equilibrium) and to the electrical response throughout the tissue in an unconfined compression configuration.