The protein film adsorbed on joint prosthesis material affects tribological property. It is expected that optimum protein film structure could improve friction and wear of joint prosthesis materials. Therefore, it is important to understand and to clarify the effect of protein film on tribological property. In the rubbing combination of ultra-high molecular weight polyethylene (UHMWPE) and CoCrMo alloy, the adsorption behavior of bovine serum albumin (BSA) and its effect on frictional property during friction were investigated by using electrochemical method. Friction force and electric potential were measured under open circuit potential (OCP) condition, but friction force and electric current were measured under -0.2 V applied potential condition. Under OCP condition, adsorbed BSA was peeled off at first rubbing, after that BSA re-adsorbed on surface under shear force condition. BSA adsorbed film reconstructed by shear force was sustained during rubbing. It is considered that the conformation of adsorbed BSA under shear stress was changed from that of static adsorption, because readsorbed BSA molecule did not show exfoliation from metal surface, which means that adsorption strength was increased from static adsorption. Under applied potential condition where wear performance of BSA film is expected to be evaluated, BSA showed the desorption at first rubbing, and gradual decrease in desorption amount. Therefore, it is confirmed that BSA film on metal surface under rubbing condition is reconstructed during rubbing. The adsorbed film formed during rubbing is stable and has an optimally-adapted structure for shear force and can sustain its property during rubbing.
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