Effect of albumin adsorption on friction between artificial joint materials

In this paper, the protein-adsorbing mechanisms on the surface of different artificial joint materials including ultra-high molecular weight polyethylene (UHMWPE), CoCrMo alloy, and Al2O3 ceramic were investigated and the corresponding adsorbing strength was measured. The friction tests between UHMWPE pin-on-CoCrMo plate, UHMWPE pin-on-Al2O3 plate, CoCrMo pin-on-UHMWPE plate, and Al2O3 pin-on-UHMWPE plate were carried out at different sliding speeds and under different stresses. Both dry and lubricated contacts were considered, using pure water, 50 per cent calf bovine serum solution and 50 per cent denatured calf bovine serum solution. The topography of the artificial joint materials before and after treated with 50 per cent calf bovine serum solution as well as the friction test were examined through optical microscope and atomic force microscope. The results indicated that albumin-adsorbing strength on the surface of UHMWPE, CoCrMo alloy, and Al2O3 ceramic was larger than 0.39 MPa. The adsorbed film was found to protect the surfaces of all materials investigated at low sliding speed and low stress, and subsequently to decrease friction. Therefore, at high sliding speed and high stress, the adsorbed albumin film was found to be denatured and desquamated from the bearing surface, which increased friction between the two bearing surfaces. A suitable roughness and surface microtopography may be favourable for retaining the albumin-adsorbed film.