Influence of Substrate on Supported Lipid Bilayers: Membrane Pinning, Stretching, Pores, and Remodelling

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 SLBs are pinned to the support, creating barriers for lipid diffusion. Furthermore, they are intrinsically stretched and under tension, causing membrane rupture and the formation of 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 field of drug-delivery systems and membrane biophysics.