Evaluation of wear property of PVA hydrogel as artifical cartilage and effect of protein film on wear-resistant property

Polyvinyl alcohol (PVA) hydrogel is one of prospective artificial cartilage materials. The mechanical property of PVA hydrogel was evaluated in the tensile test. PVA hydrogel was prepared by repeated freezing-thawing method. It is known that the mechanical strength of PVA hydrogel treated by repeated freezing-thawing method depends on the number of freezing-thawing cycles. In this study the number of freezing-thawing cycles were selected form 2, 5 and 10. The mechanical strength was the highest in 5 cycles. The wear property of PVA hydrogel as artificial cartilage was evaluated in a simplified reciprocating test. A sliding pair of an elliptical upper stationary PVA hydrogel specimen and flat reciprocating lower specimen of PVA hydrogel or glass plate was tested at constant load. The lubricant was hyaluronate (HA) solution containing protein of albumin and/or γ-globulin. In the solution containing high concentration of HA, the wear of sliding pair of PVA hydrogel was decreased. Especially wear was decreased in lubricant containing both of proteins. It is supposed that the boundary film of proteins is effective to decrease wear of PVA hydrogel. The boundary film on glass plate was observed in AFM. Albumin adsorbed weakly compared with γ-globulin. Mixed boundary film of both proteins reduced the wear remarkably.