INTERACTION OF PHOSPHOLIPID-VESICLES WITH SMOOTH METAL-OXIDE SURFACES

The interaction of phospholipid vesicles with planar metal oxide suppo rts has been previously reported as a means of preparing supported lip id bilayers, which are useful models of biological membranes. Neverthe less, extant evidence that bilayers are actually formed is rather circ umstantial, and the necessary and sufficient conditions for their form ation have never been delineated. Here, we tackle this problem by usin g smooth planar optical waveguides as the support. Analysis of the lig htmode spectra of the waveguides, measured in situ during the depositi on process, yields the mass of lipid deposited at the solid/liquid int erface. By comparing the optogeometric parameters of the structures as sembled from the vesicles with those of a lipid bilayer of known struc ture assembled using the Langmuir-Blodgett technique, we show that in many cases the vesicles remain intact and form a supported layer of ve sicles rather than a bilayer, and often mixed structures (intact vesic les embedded in a bilayer partially covering the surface) occur. Caref ul analysis of the lipid deposition kinetics corroborates this result. We have also found that divalent cations dramatically promote attachm ent of mixed phosphatidylcholine/phosphatidylglycerol vesicles to form supported vesicle layers, and bilayer formation from pure phosphatidy lcholine vesicles. (C) 1998 Elsevier Science B.V.