Influence of Substrate on Supported Lipid Bilayers: Membrane Adhesion, Stretching, Pores, and Remodeling

Model membranes offer a simplified representation of
biomembranes,
allowing for controlled structural and functional studies without
the inherent complexity of biological systems. Due to the confined
space and strong interactions with the support, supported lipid bilayers
(SLBs) exhibit markedly distinct properties compared to those of their
free-standing counterparts. However, the nano- and microscale origins
of these differences, structural effects, and the related biophysical
consequences remain incompletely understood. Using a combination of
spectroscopy and micromanipulation techniques, we reveal that lipids
in SLBs are strongly attached to the support. These SLBs are intrinsically
stretched and under tension, causing membrane rupture, and form stable
∼2 nm aqueous pores that allow the permeation of small hydrophilic
molecules. Despite strong adhesion, SLBs can undergo localized shape
changes associated with membrane fusion, and membrane nanotubes can
be extruded under optical forces. The findings underscore the very
distinct properties of model membranes, and we anticipate that they
will have important consequences in the fields of drug-delivery systems
and membrane biophysics.