Comparison of liposome amplification and fluorophor detection in flow-injection immunoanalyses

A flow-injection liposome immunoanalysis (FILIA) system was developed for the measurement of imazethapyr herbicide. The liposome is a spherical vesicle encapsulating many marker molecules in an aqueous interior. By incorporating analyte-phospholipid conjugates into the bilayer, the liposome can competitively bind to anti-analyte antibody, immobilized in the immunoreactor column of the FILIA system. In this study, the analyte-tagged liposome containing a fluorescent dye, carboxyfluorescein, was compared to a single fluorophor-tagged analyte used for the generation of the analytical signal. The liposome enhanced sensitivity by 1000-fold compared to the single fluorescent molecule-tagged analyte. This is the first report to demonstrate directly the amplification of the response by liposomes in a flow-injection immunoassay.