Influences of lubricant composition on forming boundary film composed of synovia constituents

In this study, the influences of lubricant composition on adsorption behavior of proteins and stability of protein boundary film were investigated by using total internal reflection fluorescence microscopy (TIRFM). In addition, the adsorption of hyaluronic acid (HA) on rubbed surface was also observed. It was found that the forming of bottom layer of protein boundary film mainly composed of γ-globulin is a key factor to form a stable boundary film and the friction-induced enhancement of forming protein boundary film occurred in appropriate lubricant. In addition, the adsorption of HA on rubbed surface was enhanced by coexistence with γ-globulin and frictional action. It was indicated that a gel-like film is formed due to the introduction of hydrophilic HA molecules into boundary film and it contributes to reduce friction.