Electronically conductive polymer grafted with oligonucleotides as electrosensors of DNA - Preliminary study of real time monitoring by in situ techniques

Polypyrrole bearing covalently linked oligonucleotide (ODN) probes has been used for electrode modification through one-step electrosynthesis. The biofilms obtained were employed for the direct and real-time detection of DNA hybridisation by using photocurrent spectroscopy and a quartz crystal microbalance (QCM). The photoelectrochemical properties of polypyrrole appear to be influenced by the presence of ODN allowing the transduction of the hybridisation event into a measurable photocurrent. The operational parameters of the biosensor (film thickness, ODN load,...) were assessed to optimise the response to DNA hybridisation. In addition, QCM detection, which is based on the monitoring of the biofilm mass uptake generated by molecular recognition, has been used as a validation technique. The sensors obtained have been demonstrated to be fully reusable. They have also shown a suitable sensitivity and a good reproducibility in terms of kinetic behaviour and intensity of the measured signal. Finally, this study considers the pertinence of both techniques regarding DNA hybridisation detection. (C) 2001 Elsevier Science B.V. All rights reserved.