Paper BI-ThP8
Molecular Interactions between Lubricin and Type II Collagen Surfaces: Adsorption, Adhesion, Steric Repulsion, and Boundary Lubrication

Thursday, October 21, 2010, 6:00 pm, Room Southwest Exhibit Hall

Although many studies have tried to elucidate the lubrication mechanisms that occur in articular cartilage, the molecular details of how constituents of the synovial fluid interact with cartilage surfaces and mediate cartilage to cartilage interaction still remain poorly understood. One of the major constituents of the synovial fluid that is thought to be responsible for boundary lubrication is the glycoprotein lubricin; however, details of the molecular mechanisms by which lubricin carries out its vital functions still remain largely unknown. Here, we examine i) the molecular details in which lubricin interacts with type II collagen, the main component of cartilage that provides structural integrity and tensile strength, ii) whether collagen structure can affect lubricin binding and change the adhesive interactions and boundary lubrication between collagen surfaces. We found that lubricin adsorbed strongly onto denatured, amorphous and fibrillar collagens surfaces. Furthermore, we found large repulsive interactions, between the collagen surfaces in presence of lubricin, increase with increasing lubricin concentration. Lubricin attenuated the large friction and also the long-ranged adhesion between the fibrillar collagen surfaces. Interestingly, lubricin mediated the frictional response between the denatured and native amorphous collagen surfaces equally, and showed no preference on the supramolecular architecture of collagen. We speculate that in mediating interactions at the cartilage surface, an important role of lubricin is to attach to the cartilage surface and provide a protective coating that maintains the contacting surfaces in a sterically repulsive state.