Study on the Mechanisms of Wear Reduction of Artificial Cartilage through in Situ Observation on Forming Protein Boundary Film

Abstract

PVA (poly (vinyl alcohol)) hydrogel is one of the anticipated materials for artificial cartilage. In previous research, authors found that the structure of protein boundary film on rubbing surface is a key essence for wear reduction of PVA hydrogel. The aim of this study is to understand the mechanisms of wear reduction of PVA hydrogel through in situ observation on forming protein boundary film on the rubbing surface. Reciprocating apparatus was constructed on the stage in inverted fluorescent microscope. A sliding pair of a spherical reciprocating upper specimen of PVA hydrogel and a flat stationary lower specimen of cover glass was tested. Lubricants were single and binary protein solutions, in which fluorescent-labeled bovine serum albumin and human serum γ-globulin were used as additives. When single protein was added to lubricants, albumin formed a loosely adsorbed film on rubbing surface, whereas γ-globulin adsorbed firmly and formed a smooth and uniform boundary film. When both of albumin and γ-globulin were added into lubricants, the stability of protein boundary film varied with the concentration and ratio of two kinds of proteins in lubricants. These results indicate that there is suitable content and ratio of proteins added into lubricants to form a stable boundary film.

Keywords

• artificial cartilage
• wear reduction
• protein boundary film
• in situ observation