Modification of gold microelectrodes for detection of DNA hybridization

Anna M. Nowicka 1Agata Kowalczyk 1Zbigniew J. Stojek 1Donal Leech 2

1. Uniwersytet Warszawski, Wydział Chemii, Warszawa, Poland
2. National University of Ireland, Galway (NUIG), University Road, Galway none, Ireland

Abstract
The development of a suitable electrochemical biosensor for DNA hybridisation is of great interest due to the high sensitivity, low cost, small dimensions, simple design and low power requirements offered by such a device. One of the difficulties that is faced is that that DNA hybridization does not normally produce an adequate electrical signal for the detection. This has been overcome, by e.g. labeling DNA with an enzyme which catalyses the transformation of a specific substrate to a product which may be detected electrochemically 1. We show in this presentation our strategy to achieve highly sensitive electrochemical assays for enzyme-labeled detection of DNA hybridization. The recognition film in our device is based on a redox polymer that is cross-linked and co-immobilized with a 20 mer oligonucleotide on the gold microelectrode surface either modified or not with colloidal gold. The hybridization process occurrs between the immobilized probe DNA and a biotin-modified target DNA (designed from the ssrA gene of Listeria Monocytogenes). The hybridization is followed by addition of an enzyme (glucose oxidase)-avidin conjugate and glucose. As a result bioelectrocatalytic oxidation of glucose takes place. Each hybridization event produces a large number of electrons flowing to the electrode. We have decided to employ the use of microelectrodes since a smaller surface may allow producing more reliable layers and to achieve further progress in improving the analytical performance of the sensor. Modification of the microelectrode surface with colloidal gold increases the true electrode surface area. The biofunctionalized colloidal gold nanoparticles not only reveal extraordinary stability and regeneration properties, but also posses the undisturbed, specific recognition capabilities of the colloid-bound sensing film with DNA probe.

1. P. Kavanagh; D. Leech. Anal. Chem., 2006, 78, 2710.

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Presentation: Short communication at SMCBS'2007 International Workshop, by Zbigniew J. Stojek
See On-line Journal of SMCBS'2007 International Workshop

Submitted: 2007-09-06 15:16
Revised:   2009-06-07 00:44
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