Mechanical Shear Properties of Cell-Polymer Cartilage Constructs

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Abstract
Cartilaginous constructs were created by using bovine chondrocytes on synthetic, biodegradable scaffolds made of fibrous polyglycolic acid (PGA). The constructs have previously been shown to resemble natural articular cartilage biochemically and histologically. The mechanical properties of articular cartilage mainly depend on the swollen extracellular matrix (ECM), which is a gel consisting of collagen fibers and proteoglycans in a fluid phase of water and electrolytes. The biomechanical properties of the constructs and the build-up of the ECM were studied using dynamic, nondestructive measurements in shear. A small, harmonic strain, γ ≤ 5 x 10−4, was applied to the sample, and the resulting stress was recorded and used for calculating the complex shear modulus G*. The applied strain was much smaller than that used in confined compression. The shear modulus G* correlated well with both the collagen and glycosaminoglycan content of the constructs but did not reach the same level as in natural cartilage. Collagen is the dominant component contributing to the shear strength of cartilage, and G* was shown to depend approximately quadratically on the collagen content of the constructs. The difference in G* between the constructs and natural cartilage was shown to depend on both the biochemical composition and the microstructure of the constructs.