A strip liposome immunoassay for aflatoxin B1

A technique has been developed for the preparation of aflatoxin B1 (AFB1)-tagged liposomes encapsulating a visible dye. These liposomes have several useful potential analytical applications, one of which is demonstrated. A simple plastic-backed nitrocellulose strip is the basis for an assay for detecting AFB1. Samples containing aflatoxin B1 are allowed to migrate by capillary action along the strip into a zone containing immobilized antibodies; then aflatoxin B1-tagged, dye-containing liposomes are allowed to migrate into the same area, filling any remaining antibody sites. The liposomes that bound to the antibody zone exhibit an intense purplish pink color whose optical density is inversely proportional to the aflatoxin concentration in the sample. The device is capable of detecting aflatoxin B1 at levels down to 20 ng and could serve as a rapid procedure for visual screening of agricultural and food samples for AFB1 or, with densitometry, as an inexpensive quantitative assay.