Biolubrication from Phospholipid Membranes: Correlation between nanomechanical resistance and tribological properties

Abstract

The analysis of joint molecular interfaces has led to the identification of lipid bilayers adsorbed on the joint rubbing surfaces. Nanostructural physical techniques such as lipid deposition by vesicle fusion method or by co-adsorption of lipid-detergent micelles and atomic force microscopy are used to reproduce and characterize the nano-mechanical resistance of supported phospholipid bilayers forming biological rubbing surfaces. We have studied the mechanical and tribological properties of DOPC fluid bilayers in different solutions. We observed a clear correlation between membrane resistance (probed by AFM force spectroscopy) and the tribological properties of lipid bilayers (using our homemade biotribometer). The latter allows simultaneously the measurement of the friction coefficient and the visualization of surface degradation by fluorescence microscopy. In both buffered and buffered saline solution, phospholipid bilayers are more resistant and present better lubricant properties. The addition of salt improves the resistance to indentation but not to shear. Our study thus showed that good mechanical stability of the bilayers is essential and suggested that the low friction coefficient is ensured by the hydration layers between adjacent lipid bilayers, with an important role of ions