Toxins can be classify into natural toxins already presence in foods itself Toxins that are produced after genetically modifying them.
Toxins Detection methods: The array biosensor is capable of detecting multiple targets rapidly and simultaneously on the surface of a single waveguide. Sandwich and competitive fluoroimmunoassays have been developed to detect high and low molecular weight toxins, respectively, in complex samples. Recognition molecules (usually antibodies) were first immobilized in specific locations on the waveguide and the resultant patterned array was used to interrogate up to 12 different samples for the presence of multiple different analytes. Upon binding of a fluorescent analyte or fluorescent immunocomplex, the pattern of fluorescent spots was detected using a CCD camera. Automated image analysis was used to determine a mean fluorescence value for each assay spot and to subtract the local background signal. The location of the spot and its mean fluorescence value were used to determine the toxin identity and concentration. Toxins were measured in clinical fluids, environmental samples and foods, with minimal sample preparation. Results are shown for rapid analyses of staphylococcal enterotoxin B, ricin, cholera toxin, botulinum toxoids, trinitrotoluene, and the mycotoxin fumonisin. Toxins were detected at levels as low as 0.5 ng mL–1. Keywords Biosensor - Immunosensor - Array - Multi-analyte - Toxin - Detection http://www.springerlink.com/content/7epu6q4rqtnmv98h/
About Bt toxins:
Bacillus thuringiensis produces crystal toxins and cytolytic toxins, the cytolytic toxins compliment the crystals and improve the bacterium’s ability to control insects. Bacillus thuringiensis is classified as a bacterium that produces delta-endotoxins, consisting of three domains. The structures of the three Domains are all significant in the bacterium’s lethality to insects; Domain 1 is composed of 7 alpha-helices, which can bore holes in the insect’s gut. Domain 2 has three antiparallel beta-pleated sheets, which help the antigens bind to the gut, and Domain 3 is tightly packed, which prevents binding of the gut protease (The Microbial World 2001). Because the bacterium is composed of several crystal proteins, the toxins produced have a unique “targeting affect.” Due to the fact that currently, only one of the crystal protein toxins can be affectively isolated from the bacterium at once, the natural insecticide is lethal to only a few species, depending on which protein is isolated (Tabashnik, 2002). The three types of proteins produced by the Bacillus thuringiensis bacterium are the Cry1Ab, the Cry1Ac, and the Cry3A protein. These crystal endotoxins are found in the N-terminal section of the protein. The Cry1Ab protein is lethal against the European corn borer worm and is the protein used when dealing with Bt corn plants. In Bt cotton, the Cry1Ac protein is affective against the Tobacco budworm and the Cotton bollworm. Lastly, the Cry3A protein targets the Colorado potato beetle and is used when protecting potato plants (Peferoen, 1997). Due to the fact that Bacillus thuringiensis is only lethal to a small variety of insect species, many non-threatening or beneficial insects survive. However, there much research is being conducted on incorporating all three Cry proteins into a plant’s genome. With all three proteins augmenting each other, the result is a crop that is resistant to all types of Lepidopteron and a few species of the Coleopteran family. This new Bt plant, or “Bt2”, solves a common problem that cotton farmers struggle with each growing season. Since Bt1 only isolates the Cry1Ac protein and is lethal solely against Tobacco budworms and Cotton bollworms, the Fall and Beet Armyworms, which are major destructive species, are not affected. Therefore, Bt2 virtually eliminates all of the major Lepidopteron pests that hinder high cotton yields.
