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Mycotoxin Detection in Foods Using Electrochemical Sensors Based on Affinity Molecules Incorporated into Conducting Polymer Films


Mycotoxin is a broad term to describe toxic secondary metabolites derived from certain filamentous mold strains (Aspergillus, Penicillium, Fusarium). Any crops (pre- or post-harvest) that support the growth of molds can potentially become contaminated with mycotoxins, although cereals (wheat, barley, maize, rye) and oilseeds are considered high risk commodities. A common feature of mycotoxins is the high binding affinity to DNA and proteins leading to chronic conditions such as cancer, immuno-suppression or organ damage. Mycotoxins are highly stable and can accumulate within the body when ingested in small quantities over prolonged time periods. In animals (especially pigs), the production period is typically too short to result in chronic toxicity, however, even moderate levels can detrimentally effect their development.
Due to the stability of mycotoxins there is no reliable method to inactivate or remove the toxic agent should contamination occur. Therefore, there is a high reliance on sample screening to identify contaminated batches and restrict entry into the food chain. Because mycotoxins represent a hazard even when present in trace amounts, regulatory limits are set in the parts per billion (ppb) and sample sizes are typically large (0.1-1 kg). Therefore, this necessitates initial extraction and concentration of mycotoxins from samples prior to detection using techniques such as HPLC or ELISA. Current methods are laboratory based, require a high level of expertise and are time consuming. An ideal alternative would be to screen for mycotoxins on-site thereby providing rapid results and immediate corrective action to take place (withdrawal or diversion of contaminated batches). Current on-site tests based on ELISA dip-sticks have complicated protocols and poor sensitivity. In the following project a self contained rapid, on-site, screening method that enables extraction, capture and detection of mycotoxins with minimal user input will be developed. Mycotoxins (aflatoxin B1, orchatoxin A, fumonisin B1, DON and patulin) will be extracted into aqueous solutions of methanol and concentrated (captured) via passage through molecular imprinted conducting polymer films.
The mycotoxin in the eluent will be injected into a flow injection system and passed over a conducting polymer modified electrode containing a binding affinity agent (antibody, nucleic acid, serum albumin). The bind-
ing of mycotoxin to affinity agent will be reagentless detected through monitoring changes induced in the electrochemical properties of the supporting conducting polymer film. It is envisaged that the sensor will have a lower detection limit in the range of ppb.

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Expected Impact of Project Outcomes on Food Safety in Ontario:
The mycotoxin levels in grains (wheat and corn) within Ontario are amongst the highest encountered within Canada. This is primarily due to the climatic conditions within the province that are conducive to mycotoxin formation by contaminating molds.
Due to the inherent stability of mycotoxins there is a strong reliance on screening methods to prevent contaminated products from entering the food chain. This not only includes foods destined for human consumption but also animal feed since mycotoxins can be readily transferred via meat, milk, cheese and eggs. Currently, the majority of screening is performed within commercial laboratories at a cost of $18-125 per test and turn-around time of up to 7 days. Therefore, any action taken is retrospective.
The system to be developed will enable detection of ppb levels of mycotoxins within 30 minutes with minimal user input. On-site testing will facilitate more frequent screening for mycotoxins, but more importantly, enable corrective action to be taken should contaminated batches be detected. The system to be developed can be fully automated and enable detection of multiple mycotoxin types simultaneously. It is envisaged that the output of the research will provide a powerful tool to reduce mycotoxins within the food chain and further enhance food safety standards within Ontario. <P> For more information, please visit the <a href="; target="_blank">Ontario Ministry of Agriculture, Food & Rural Affairs (OMAFRA) Food Safety Research Program</a>.

Warriner, Keith
University of Guelph
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