Lipids and lipid mixtures in boundary layers: From hydration lubrication to osteoarthritis

Phospholipids and Hyaluronan: From Molecular Interactions to Nano- and Macroscale Friction

“…For example, the headgroup region of the phospholipids and the hydroxyl groups of the poly-and oligosaccharide chains are all strongly hydrophilic. This leads us to the hydration lubrication mechanism, as first envisaged by Klein and co-workers [21][22][23]. The strong binding of water molecules prevents dehydration of the hydrophilic groups and retains a water layer between the sliding surfaces.…”

Insight into the hydration friction of lipid bilayers

“…In recent years, many friction experiments have been carried out on hydration lubrication systems composed of lipids whose highly hydrated headgroups may reduce the friction. 3 However, most studies have been performed on the lubrication of zwitterionic lipids such as phosphatidylcholine lipids [26][27][28][29][30][31] and, to a lesser extent, on the lubrication of cationic lipids and anionic lipids. Therefore, in order to explore the effect of surface charges on the hydration friction behaviors and further understand the hydration lubrication mechanism involved, this work studied the hydration friction behaviors of three lipids with different charged headgroups (a cationic lipid, a zwitterionic lipid and an anionic lipid) through a combination of FM-AFM and FFM.…”

“…Ultralow friction in aqueous media has received extensive research attention due to their relevance to many aqueous boundary lubrication systems and biological lubrication processes. [1][2][3] Over the past few decades, extremely low sliding friction in aqueous environments has been designed and achieved through coating surfaces with surfactants, polymer brushes or lipids. [4][5][6][7][8] The mechanisms underlying this observed extremely low sliding friction are very different from those of the classic friction.…”

The Effects of Splayed Lipid Molecules on Lubrication by Lipid Bilayers

“…Each mica substrate is coated by a single lipid bilayer or liposome and shear forces were measured under pressures up to 100 atm over a micron-sized contact area. It has been repeatedly demonstrated that friction coefficients between a variety of phosphatidylcholine (PC) lipid membranes are remarkably low, at 10 −5 -10 −4 under physiological pressures, comparable with that of biological joints [11][12][13][14][15]. PC lipids consist of a hydrophilic zwitterionic headgroup and acyl tails, which leads to bilayers with headgroups exposed to the aqueous environment and the hydrophobic acyl tails interacting to stabilize the bilayer structure.…”