Supported Planar Single and Multiple Bilayer Formation by DOPC Vesicle Rupture on Mica Substrate: A Mechanism as Revealed by Atomic Force Microscopy Study

Abstract

A planar lipid bilayer on a solid support serves as model system that explains fundamental aspects of membrane biology and enables us to characterize wide-range surface-sensitive techniques, including molecular engineering. The present study aims at understanding the process of single and multiple bilayer formation after the exposure of small unilamellar vesicles (SUVs) of dioleoyl phosphatidylcholine (DOPC) to mica substrate. Isolated single bilayer formation and co-existence of double and triple lipid bilayers in the aqueous medium have been quantitatively measured by atomic force microscopy and discussed the physicochemical mechanism. It has been observed that due to the strong adhesion of DOPC SUV to mica surface, vesicles of diluted solution rupture spontaneously and form isolated bilayer patches when they come in contact with the mica surface. No further lateral growth or movement of the bilayer patches has been observed upon increase of incubation time. However, the increase of vesicle number on the same surface area by successive deposition of DOPC solution of same concentration and increasing incubation time shows merging of the nearby patches as well as development of stacked second and third bilayers due to edge-guided rupture of adsorbed vesicles on first or second bilayer patches. Mechanisms of single and multi-bilayer formation and a theoretical interpretation of the process have been elucidated.