Testing Rigidity Percolation Models of Articular Cartilage via Enzymatic Degradation

The shear modulus of articular cartilage has been shown to change by several orders of magnitude with depth, and these changes correlate well with very slight changes in concentration of the constituents of the tissue, namely collagen fiberils and aggrecans. A Rigidity Percolation Model has been proposed to explain this jump in shear modulus. Here, I will describe results of studies where we use readily accessible enzymes to selectively degrade the constituents of articular cartilage and measure the mechanical properties with depth using confocal elastography. Comparing the mechanical measurements with the constitutive concentrations of cartilage, measured using FTIR imaging, we test and further develop our rigidity percolation models to describe the mechanical behavior of articular cartilage. Ultimately, development of these models will enable creating new artificial constructs with properties based on the model predictions, for use as tissue replacements, or in soft robotics.