(222al) Creating Free-Standing Lipid Bilayers On Fused Silica Substrates With Nanograting Structure

Supported lipid bilayer membranes have been widely used to study protein-lipid membrane interactions due to the fixed position and planar geometry suitable for many surface analytical tools. However, the membrane physical properties are often influenced by the solid support, which may affect the interested interactions. Some previous studies have created free-standing bilayers by depositing unilamellar vesicles on the pores with sizes smaller than the vesicles or by using shear-driven bilayers to span over nanopores at high pH. However, these methods may not form continuous bilayers in a large scale or may not apply to various types of lipids. Here, we developed a theory, based on extended-Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and Helfrich bending theory, to estimate the appropriate conditions for creating free-standing lipid bilayers on solid supports with nanograting structure.  We calculated how the buffer conditions, lipid types, and the solid support geometry can influence the affinity between the lipid membrane and the solid support, and the bending energy of the lipid membrane. When the bending energy dominates the entire energy of the system, we predicted that the membrane would form free standing bilayers above the trenched area of the nanograting solid support. On the other hand, if the support-membrane affinity dominates, the lipid bilayer can easily bend and follow the contour of the solid support. In order to tune the relative size of the support-membrane affinity and the bending energy, we prepared buffers with a series of ionic strength (from 5 mM to 100 mM NaCl) and fused silica substrates with periodic 100 nm and 200 nm nanograting structure. The characterization of membrane states by fluorescence recovery after photobleaching measurement shows that our experiment results well match the theoretical predictions and that the developed theory could be used to predict the suitable conditions for the free-standing bilayers to form on solid supports with various kinds of geometry.