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 bio films obtained were employed for the direct and real-time detection of DNA hybridisation by using photocurrent spectroscopy and a quartz crystal micro balance (QCM). The photoelectrochemical properties of polypyrrole appear to be influenced by the presence of ODN allowing the transduction of the hybr idisation event into a measurable photocurrent. The operational parameters of the biosensor (film thickness, ODN load,...) were assessed to optimise t he response to DNA hybridisation. In addition, QCM detection, which is base d on the monitoring of the biofilm mass uptake generated by molecular recog nition, has been used as a validation technique. The sensors obtained have been demonstrated to be fully reusable. They have also shown a suitable sen sitivity and a good reproducibility in terms of kinetic behaviour and inten sity of the measured signal. Finally, this study considers the pertinence o f both techniques regarding DNA hybridisation detection. (C) 2001 Elsevier Science B.V. All rights reserved.