Hydration forces at solid and fluid biointerfaces

Abstract

We review the different molecular mechanisms giving rise to the repulsive hydration force between biologically relevant surfaces such as lipid bilayers and bio-ceramics. As we will show, the hydration force manifests itself in very different and subtle ways depending on the substrates. Soft, mobile surfaces such as lipid bilayers tend to exhibit monotonic, decaying hydration force, originated from the entropic constriction of the lipid head groups. Solid surfaces on the other hand, tend to exhibit a periodic oscillatory hydration force, originated from the surface induced polarization of water molecules. In this review we will describe both subtle faces of this important interaction by first describing the early experiments performed on solid surfaces and their interpretation by recent simulation studies. Then we will describe the hydration force between fluid interfaces such as bilayers and explain how experimentally researchers have unraveled the dominant role of the lipid head groups conformation.