Investigation of liposome-based immunomigration sensors for the detection of polychlorinated biphenyls

The use of immunospecific liposome migration offers many advantages for the extralaboratory detection of environmental contaminants. Devices utilizing this technique are fast, easy to use, and robust and respond to the presence of analyte at low-parts-per-billion concentrations. Investigations have been carried out that determine optimal interactions for key components of these assays, and techniques are presented for the development of generalized liposome immunoassays. Two complementary prototype liposome-based immunomigration techniques have been developed for the detection of polychlorinated biphenyls (PCBs). The liposome immunocompetition assay format measures the competitive reaction between analyte-tagged liposomes and the sample analyte for immobilized antibodies and can detect 0.4 nmol of PCB in less than 8 min. A more sensitive format, the liposome immunoaggregation (LIA) assay detects the inhibition of immunospecific liposome aggregation in solution and can detect 2.6 pmol of PCB in less than 23 min. Laser diffraction particle sizing has been used to study LIA-induced increases in liposome size over time and to determine optimal conditions for the application of this technique. Both formats utilize capillary action to transport liposome-containing solutions along strips of nitrocellulose. Measurement of color intensity is then carried out visually or with a desktop scanner.