The effect of nanoclay and crosslink density on the mechanical and tribological properties of a hydrogel composite for cartilage replacement

Abstract

Millions of individuals suffer from the bone joint disease arthritis, every year, worldwide. Total joint replacements, the standard for current treatment has certain drawbacks such as wear of the surface, a negative immune response to wear particles, non-matching of the mechanical and tribological properties with natural bone joint tissue. In order to overcome the drawbacks of current materials used in total joint replacements, and mimic natural cartilage, hydrogel composite materials were investigated. Inter penetrating networks of Poly Hydroxyethyl Methacrylate (P-HEMA) and Poly Acrylamide (PAAM) were synthesized with nano clay particles as reinforcement. Tribological and compression tests were carried out. There was a significant change in stiffness and failure load with the addition of nanoclay. Four lubricants-simulated body fluid (SBF), and SBF with 1, 2, and 3mg/ml of Hyaluronic acid (HA) were incorporated in the tribological tests. The counter material was a stainless steel pin. It was found that the nanoclay particles significantly improved the strength of the composite. Increasing the HA concentration led to an increase in viscosity of the lubricant but had no significant effect on the coefficient of friction. An increase in crosslink density also led to an increase in the coefficient of friction. The addition of nano clay led to a decrease in the coefficient of friction.