The effect of buffer solution choice on protein adsorption and lubrication

In vitro buffers are frequently used to formulate model synovial fluids to investigate the role of individual constituents in synovial joint lubrication. This work examines how buffer choice affects protein film formation in static and rolling conditions. Solution pH dominates both the protein adsorption kinetics and the formation of tribofilms in static and rolling conditions respectively. Under static conditions, equilibrium adsorbed protein films from all buffers tested have similar properties although three distinct modes of adsorption, governed by the pH of the buffer, are observed. Films formed under rolling conditions are also pH dependent, with large irregular deposits formed in solutions with pH 7.4 or lower. The adsorption properties of proteins under static conditions only partially govern the lubrication properties of proteins.