Biotribology of synovial cartilage: Role of albumin in adsorbed film formation

Abstract

A properly lubricated natural synovial joint is the basis of the proper function of the natural musculoskeletal system to lead an active and painless life. A properly lubricated natural synovial joint is the basis of the proper function of the natural movement system to lead an active and painless life. Well lubricated synovial joints are expressed, in particular, by an extremely low coefficient of friction and wear between cartilage surfaces. The presented manuscript is focused on the impact of albumin protein on the formation of adsorbed boundary layer in the contact of cartilage – a simplified model of synovial joint. This can contribute to better understanding of the lubrication in synovial joints. All presented experimental tasks were performed using a reciprocating tribometer along with fluorescence microscopy – friction forces were measured simultaneously with fluorescence records of contact. This unique experimental approach used a newly designed evaluating procedure based on image processing. The experimental results show a great impact of hyaluronic acid; adding of hyaluronic acid leads to a reduction in friction and a larger area of albumin adsorbed boundary layer; however, the phospholipids show the opposite effect. A combination of the individual protein solutions, albumin and γ-globulin, has no significant effect on the particles count of albumin clusters adsorbed in the contact; however, the area of albumin adsorbed boundary layer with simple albumin solution was much larger than the solution combining both proteins. The conclusions and discussion of this study describe the role of albumin protein in the lubricating process prevailing in a simplified model of synovial joint under conditions corresponding to slow human gait.

Keywords

• Biotribology
• Cartilage
• Reciprocating tribometer
• Friction
• Lubrication
• Fluorescence microscopy