Amphiphilic Nanoparticles Control the Growth and Stability of Lipid Bilayers with Open Edges

Molecular amphiphiles self-assemble in polar media to form ordered structures such as micelles, vesicles, and membranes essential to a broad range of industrial and biological processes.  However, some of the more interesting architectures – such as bilayer sheets, helical ribbons, and hollow tubules – are inherently unstable owing to the presence of “open” edges that expose the hydrophobic bilayer core to the polar surroundings. Here, we describe a strategy to stabilize open bilayer structures using amphiphilic nanoparticle “surfactants” that present mixtures of hydrophilic and hydrophobic ligands on their surface. These particles can bind selectively to the open edge of bilayer membranes to stabilize otherwise transient amphiphile assemblies.  We show how such particles can precisely control the size of lipid tubules, how they can inhibit the formation of undesirable assemblies such as gallstone precursors, and how they can stabilize free-floating lipid “microdiscs”.