Development of a biosensor array to rapidly detect and measure organophosphate pesticides in grain

Abstract

The aim of this three-year project was to investigate scientific and technological issues involved in the implementation of rapid sensor technology, for the detection of organophosphate residues in raw food products. The project succeeded in demonstrating that an array of biosensors can be used to rapidly detect and measure organophosphates in samples of grain.

The project successfully integrated rapid extraction techniques, biosensor technology, instrument design and sophisticated pattern recognition software which resulted in the development of a prototype instrument that could rapidly detect and measure different organophosphate pesticides in grain. The instrument relies on the fact that organophosphate pesticides poison, or inhibit the enzyme acetylcholinesterase. Slight modifications to the active site cause the enzyme to be inhibited to differing extents by a given pesticide. Therefore an array of six enzymes, each slightly different, will give a characteristic pattern of inhibition to each pesticide. A neural network programme recognizes the pattern of inhibition and identifies the pesticide and its concentration. Different pesticides will produce a different pattern of inhibition that can be recognised by the neural network programme.

During the programme of investigation different parts of the analytical system were developed and optimised. This included an extraction method which involved design of an extraction vessel and oxidation method. Development of the biosensor array involved selection, immobilisation and stabilization of enzymes; design, characterisation and optimisation of the electrodes. An instrument was designed and a prototype produced to take the biosensor array. The instrument had a fluidics system to take the pesticide extract to the biosensors and supply enzyme substrate and wash solutions at the appropriate times. The currents generated by the biosensors are read into a neural network programme that had to be trained to recognise particular patterns of inhibition for each pesticide. The final part of the research programme was for an end-user to evaluate the complete analytical system which was composed of the extraction process and the analysis by the prototype instrument.

The outcome of the project was to demonstrate that rapid sensor technology can be used to detect and measure organophosphate pesticides residues extracted from raw food products. Measurements made on the prototype instrument were validated by an end-user in an analytical laboratory and the instrument was portable and could be used by semi-skilled personnel. The total assay time was slightly less than 30 minutes although it may be possible to reduce this to approximately 20 minutes. The technology developed could be developed further to measure other substances in food such as toxins or antibiotics.