Lubricating characteristics of hyaluronic acid molecules on the albumin-mediated tribological processes

Synovial fluid mediated boundary lubrication is the key mechanism dominating the wear process of the artificial joint materials. The most abundant composition in the synovial fluid is albumin. It has been observed that the increasing human serum albumin (HSA) concentration leads to the increasing friction coefficient under the articulation of ultra-high molecular polyethylene (UHMWPE) and CoCrMo alloy materials. In this study, the friction and adsorption experiments were carried out to investigate the effects from addition of hyaluronic acid (HA) molecules. Our results indicated that the increase in HA concentration level results in the decrease of the frictions under HSA-HA mixed lubrication conditions. Insertion of HA molecules at the interface provide a higher elasticity of the lubricating layer. This damping mode results in the slightly reduction of friction. More HA molecules may entrap the HSA molecules and then expel them away from the articulating surfaces. This expelling mode leads to a significant decrease of friction. The lubricating mechanism of hyaluronic acid on the albumin-mediated tribological processes between UHMWPE and CoCrMo materials was investigated and proposed in this study.