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Reagentless Impedimetric Biosensors for Detection of Pathogens in Greenhouse Operations and Pork Processing


The time between the introduction of a biohazard and subsequent detection can strongly influence its impact (both in terms of health and economic). Although rapid detection methods are available these are typically laboratory based. Therefore, even if analysis can be performed within hours the time to collect, deliver and process the sample can take days. In this respect there is an identified need for sensors that can be used on-site that act as an alarm for the presence of potential biohazards. In the following project novel reagentless sensors for the detection of fecal indicators and pathogens will be developed.

The sensors are based on conducting polymer nano-tubes formed within microporous polycarbonate membranes onto which bioaffinity agents (host cell or antibodies) are immobilized. Interaction of the immobilized bioaffinity agent with analyte induces changes in the electrochemical properties of the conducting polymer film that can be detected using impedance spectroscopy. In the current project the target analytes selected will be F(+) coliphage (bacteriophage commonly linked to fecal contamination) and Salmonella. However, the generic sensing approach can be used to detect any biohazard (bacterial pathogens, enteric viruses, protozoa, endospores, toxins) through judicious choice of bioaffinity agent.
Initial work will fabricate the polymer electrodes and optimize immobilization of bioaffinity agents within the conducting polymer nano-tubes. The kinetics, sensitivity and selectivity of the sensors will be determined. Sensor performance will be validated against current standard techniques. Finally the ability to detect contamination within irrigation water or pork processing facilities using the sensor devices will be evaluated. Matrix affects on sensor performance will be evaluated and minimized through techniques such as background subtraction.
The sensors to be developed will be reagentless with no sample volume limitations or significant user input. The projected cost of the sensor strips will be $2-5 and have a detection time of 5- 40 minutes. The limit of detection for coliphage will be in the order of 1 pfu/ml. The lower limit for Salmonella detection is projected to be 1-102 cfu/ml.

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Expected Impact of Project Outcomes on Food Safety in Ontario:
OMAF has been pro-active at introducing HACCP and traceability schemes throughout the food chain. This in turn has led to an increase in end-product screening to reduce the risk of contaminated products reaching the marketplace. However, a more efficient approach would be to screen for hazards at critical points within the food chain thereby restricting the dissemination of contamination.
The sensors will be fabricated from relatively inexpensive materials and it is anticipated that each unit cost no more than $2-5. By using plant derived antibodies (developed by Prof C A Hall) the cost can be further reduced. Hand-held impedance analyzers are now commercially available and can be customized to the appropriate measurement type required.
Availability of robust, reliable and cheap biohazard sensors is the foundation of effective biosecurity, HACCP and traceability schemes. In this respect the generic sensing approach to be developed will be of direct benefit to food producers, processors, retailers and regulators. <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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