Low friction hydrogel for articular cartilage repair: Evaluation of mechanical and tribological properties in comparison with natural cartilage tissue

The mechanical and tribological properties of a novel biomaterial, a boundary lubricant functionalized hydrogel, were investigated and compared to natural cartilage tissue. This low friction hydrogel material was developed for use as a synthetic replacement for focal defects in articular cartilage. The hydrogel was made by functionalizing the biocompatible polymer polyvinyl alcohol with a carboxylic acid derivative boundary lubricant molecule. Two different gel processing techniques were used to create the hydrogels. The first method consisted of initially functionalizing the boundary lubricant to the polyvinyl alcohol and then creating hydrogels by physically crosslinking the reacted polymer. The second method consisted of creating non-functionalized polyvinyl alcohol hydrogels and then performing the functionalization reaction on the fully formed gel. Osteochondral bovine samples were collected and replicate experiments were conducted to compare the mechanical and tribological performance of the boundary lubricant functionalized hydrogels to non-functionalized hydrogels and native cartilage. Friction experiments displayed a maximum decrease in friction coefficient of 70% for the functionalized hydrogels compared to neat polyvinyl alcohol. Indentation investigated the elastic modulus of the hydrogels, demonstrating that stability of the hydrogel was affected by processing method. Hydrogel performance was within the lower ranges of natural cartilage tested under the exact same conditions, showing the potential of the boundary lubricant functionalized hydrogels to perform as a biomimetic synthetic articular cartilage replacement.