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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Publications at this Location » Publication #117451
Title: A STRIP LIPOSOME IMMUNOASSAY FOR AFLATOXIN B1

Author
item HO, ANNIE - NATIONAL CHI-NAN UNIV.
item Wauchope, Robert - Don

Submitted to: Bioanalytical Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2002
Publication Date: 6/1/2002
Citation: HO, A., WAUCHOPE, R.D. A STRIP LIPOSOME IMMUNOASSAY FOR AFLATOXIN B1. ANALYTICAL CHEMISTRY 74:1493-1496. 2002.

Interpretive Summary: We have developed a simple "dip-stick" procedure which has potential as a test to check foods for the presence of the microbial poison aflatoxin B1. The technique relies on aflatoxin-coated or "tagged" liposomes, which are tiny spheres created in certain chemical mixtures by ultrasonic agitation. They can be filled with an intense dye and the whole sphere will attach to surfaces meant to capture aflatoxin. Then the liposomes can be broken up by changing the solution makeup; they then release the dye, creating a vivid color depending on how many liposomes were captured. The dip-sticks are plastic-backed paper strips with aflatoxin-sensitive surfaces. The strips are dipped into a food extract and then dipped into a tagged liposome mixture and the liposomes disrupted; the lower the resulting color intensity the greater the aflatoxin concentration in the extract. The color intensity can be estimated by eye or more accurately by instruments. The test may be considerably cheaper than current methods.

Technical Abstract: 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 18 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.