Disposable electrochemical genosensor for the simultaneous analysis of different bacterial food contaminants

This paper deals with the use of an electrochemical genosensor array for the rapid and simultaneous detection of different food-contaminating pathogenic bacteria. The method includes PCR amplification followed by analysis of the amplicons by hybridisation with toxin-specific oligonucleotide probes. A screen-printed array of four gold electrodes, modified using thiol-tethered oligonucleotide probes, was used. Unmodified PCR products were captured at the sensor interface via sandwich hybridisation with surface-tethered probes and biotinylated signaling probes. The resulting biotinylated hybrids were coupled with a streptavidin-alkaline phosphatase conjugate and then exposed to an alpha-naphthyl phosphate solution. Differential pulse voltammetry was finally used to detect the alpha-naphthol oxidation signal. Mixtures of DNA samples from different bacteria were detected at the nanomolar level without any cross-interference. The selectivity of the assay was also confirmed by the analysis of PCR products unrelated to the immobilised probes.