A DNA piezoelectric biosensor assay coupled with a polymerase chain reaction for bacterial toxicity determination in environmental samples

In this paper, we report the realisation of a DNA piezoelectric biosensor c oupled with the polymerase chain reaction (PCR) for the detection of a spec ific bacterial toxicity factor. Biotinylated 23-mer probes were immobilised on the streptavidin coated gold surface of a quartz crystal; streptavidin was covalently bound to the thiol/dextran modified gold surface. The hybrid isation of the immobilised probe with a synthetic oligonucleotide was inves tigated; the absence of non-specific adsorption was verified using a non-co mplementary oligonucleotide. Many cycles of measurements can be performed o n the same crystal surface by regenerating the single strand with 1 mM HCl. The same hybridisation reaction was then performed using real samples of D NA extracted from bacteria and amplified by PCR. The PCR product was a frag ment of a specific gene of Aeromonas hydrophila. The piezoelectric biosenso r was able to distinguish samples containing the gene or not; in this way i t was possible to determine the pathogenicity of different Aeromonas strain s isolated from water, vegetables or human specimens. Experiments with non- specific samples confirmed the absence of adsorption or non-specific effect s on the quartz crystal treated with the reported procedure. (C) 2000 Elsev ier Science B.V. All rights reserved.