The formation of lipid bilayers on surfaces

The adsorption of biological molecules at solid-liquid interfaces is growing in importance due to its application to a very broad range of fields. Biomimetic systems like phospholipid mono- or bilayers are used to study such adsorption processes in great detail. Here we show how the formation of a complete lipid bilayer by vesicle adsorption and rupture depends on the type of the surface used. Fairly smooth SiO(2) surfaces and much rougher polyelectrolyte cushions are used to study this process. Depending on the chemical structure of the lipids, two different pathways are found on SiO(2) surfaces: either vesicle adsorption occurs in a first step until a critical coverage is reached followed by vesicle rupture and bilayer formation or adsorption and vesicle rupture occur almost at the same time. In the case of polyelectrolyte cushions, both neutron reflectivity and quartz crystal microbalance experiments show that the formation of homogeneous DMPC bilayers is significantly better on the negatively charged PSS surface compared to the positively charged PAH surface.