Lubrication and Wear of Crosslinked Hyaluronic Acid On Model Surfaces

Hyaluronic acid (HA) is an important component in synovial fluid and thus is considered to play an important role in articular cartilage lubrication. Using the surface forces apparatus (SFA) technique, we have investigated the boundary lubrication behavior of crosslinked HA. HA was first adsorbed on poly-dopamine modified mica surface and then crosslinked. Both the normal and friction forces between two layers of crosslinked HA are measured in SFA. The normal force profiles of two crosslinked HA layers fit Alexander-de Gennes brush polymer theory well. For pressure up to ~100 atm, crosslinked HA shows uniform boundary lubrication behavior with a friction coefficient μ~0.12 and no serious damage occurs even at very high load (near 100 atm). Our study shows that a low coefficient is not a necessary requirement to have low wear. These results support our hypothesis that HA is not a good boundary lubricant at low load but could function as a good wear protector and a back up boundary lubricant under high load.