Rapid and sensitive detection of aflatoxins using immunomagnetic bead-based recovery and real-time qPCR assay

Several mold species of Aspergillus produce secondary metabolites called Aflatoxins. These aflatoxins can be carcinogenic and are considered potential threats to human and animal health when ingested. Aflatoxins occur naturally in food and feed products in microgram to milligram per gram of food or feed quantities thus detection methodology should be sensitive and specific which is not obtained with currently available methods. This study involves detection and quantification of aflatoxins in food products and animal feeds. Our research methodology involves use of immunomagnetic beads combined with real time PCR assay using aflatoxin specific polyclonal and monoclonal antibodies to capture and detect aflatoxins. Primary (polyclonal) antibodies for aflatoxin B1 were covalently attached to 2.8 μm-diameter magnetic beads using a bi-functional cross linking agent. A secondary antibody for aflatoxin B1 was also covalently linked to DNA oligonucleotides based on the luciferase gene as a reporter DNA molecule. Real-time PCR amplification of the reporter DNA after aflatoxin capture provides for sensitive detection of toxin, if present. Magnetic beads were coupled to primary antibodies while secondary antibodies were coupled to DNA reporter molecules. Amplification (PCR) targeting an internal portion of the reporter molecule gave DNA fragments of the expected size. Coating of magnetic beads with capture antibodies has been facilitated by use of the BeadRetrieverTM. Quantification of toxins in food and feed samples will involve signal amplification strategies using real-time PCR amplification of reporter DNA using specific primers. This methodology is rapid, sensitive, and will help to detect and quantify low levels of aflatoxins that could otherwise be fed to food production animals, domestic animals (cats, dogs, horses), or humans through aflatoxin-contaminated cereal grains and feed.