Formation of Supported Lipid Bilayers by Vesicle Fusion: Effect of Deposition Temperature

We have investigated the effect of deposition temperature on supported lipid bilayer formation via vesicle fusion. By using several complementary surface-sensitive techniques, we demonstrate that despite contradicting literature on the subject, high-quality bilayers can be formed below the main phase-transition temperature of the lipid. We have carefully studied the formation mechanism of supported DPPC bilayers below and above the lipid melting temperature (T-m) by quartz crystal microbalance and atomic force microscopy under continuous flow conditions. We also measured the structure of lipid bilayers formed below or above T-m by neutron reflection and investigated the effect of subsequent cooling to below the T-m. Our results clearly show that a continuous supported bilayer can be formed with high surface coverage below the lipid T-m. We also demonstrate that the high dissipation responses observed during the deposition process by QCM-D correspond to vesicles absorbed on top of a continuous bilayer and not to a surface-supported vesicular layer as previously reported.