Sensitivity and specificity performance of a direct-charge transfer biosensor for detecting Bacillus cereus in selected food matrices

A direct-charge transfer conductometric biosensor was developed for the detection of Bacillus cereus in various food samples in this study. The biosensor employed antibodies as the biological sensing elements and polyaniline (emeraldine salt) as transducers for detection. The biosensor used the principle of a sandwich immunoassay, combined with an electron charge flow aided through conductive polyaniline, to generate an electronic signal that was recorded by a data collection system. The biosensor architecture was based on the lateral capillary flow of a liquid sample. Polyaniline tagged with primary anti B. cereus antibodies were responsible for the first capture of the target pathogen followed by the formation of a sandwich complex with secondary antibodies functionalised on the biosensor surface. The biosensor was able to detect cell concentrations in the range of 35-88CFU ml(-1) in the food samples with a detection time of 6 min. The biosensor was found to be specific to the target pathogen in pure cultures of Bacillus megaterium and generic Escherichia coli. The speed, sensitivity and ease of use, of this biosensor make it a promising device for rapid field-based diagnosis toward the protection of the food supply chain. (C) 2007 IAgrE. Published by Elsevier Ltd. All rights reserved.