1. An example preparation of oligonucleotide-modified vesicles. A mixture of lipids containing egg phosphatidylcholine and 0.5 mol % of reactive lipid, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[3-(2-pyridyldithio)propionate] (sodium salt) (N-PDP-PE, Avanti Polar Lipids), and fluorescently labeled lipid, Texas Red 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine (TR DHPE, Molecular Probes) in chloroform, is dried to a film, reconstituted in buffer (100 mM borate, 50 mM citrate, 100 mM NaCl, 2 mM EDTA, pH 8.0) to 25 mM and extruded through a 50 nm polycarbonate membrane (Avanti) to form vesicles. An oligonucleotide modified with a disulfide group on the 5‘-end (IDT DNA technologies) is first reduced to expose a free sulfhydril functionality with 10 molar excess tris(2-carboxyethyl)phosphine (TCEP), then added to the vesicle solution to a final DNA concentration of 50 μM and lipid concentration of 13 mM. The DNA attaches to the outside surface by a disulfide exchange reaction on average 1−2 per vesicle, estimated using an assay based on the fluorescence of a labeled antisense oligonucleotide. Vesicles are isolated on a Sepharse CL-4B gel filtration column with the same buffer as eluant. Supported bilayers displaying oligonucleotides are formed on a cleaned glass coverslip by vesicle fusion as described earlier for simple lipids (Salafsky, J.; Groves, J. T.; Boxer, S. G.Biochemistry1996,35, 14773−81), and excess vesicles are rinsed away with copious amounts of buffer. Vesicles, at approximately 70 μM in lipids, displaying the complementary oligonucleotide, are incubated with this bilayer at room temperature for 30 min followed by further rinsing with buffer to remove free, unattached vesicles. Similar procedures were used to prepare vesicles varying in size from 30 to 200 nm and oligonucleotide lengths of 16 to 24 bases.
2. Micropattern Formation in Supported Lipid Membranes