Discrete membrane arrays

This review describes various methods for the attachment of phospholipid bilayers to solid supports. The simplest approach involves vesicle unrolling onto a surface that has been previously modified with a continuous self-assembled monolayer (SAM). The choice of a suitable SAM can lead to the formation of attached bilayers that have the desired biomimetic properties and are suitable for studying transmembrane proteins. However, there are intrinsic problems associated with this approach if one is interested in studying ion transport phenomena. In particular, the relatively low resistance values found for such bilayers do not permit studies of single ion channels. For such studies to be carried out the background leakage through the lipid film must be greatly reduced. In an attempt to reduce the problems of leakage we have formed patterned SAMs in which a blocking, hydrophobic, layer covers 90% of the electrode surface. The remaining portion of the surface, which is hydrophilic, supports the formation of a bilayer. This approach has led to an improvement in the quality of the bilayers formed but has still not provided bilayers with sufficiently high specific resistances to study single ion channels. Finally, we describe new approaches based on the formation of bilayers suspended over small apertures. These 'suspended' bilayers are similar in structure to those used in black lipid membrane experiments and give rise to highly blocking bilayer membranes. Unfortunately, this approach requires the use of solvents to create the suspended bilayer and they are relatively fragile.