Intercalation of small compounds into double stranded DNA (dsDNA) has been intensively studied during the past four decades due to the huge interest in the clinical use of compounds that bind strongly to DNA with applications as antitumor agents but as well as detection schemes for the quantification of DNA hybridization. Detection of hybridization events based on incorporation of suitable intercalating compounds into dsDNA may eliminate the need to modify the DNA target strand for further specific mo­dification reactions (e.g. introduction of covalently bound labels which is only possible during polymerase chain reaction (PCR)). Therefore, methods based on specific in­tercalation of suitable intercalators into dsDNA may simplify interrogation of DNA hybridization events.

Here, we present the effects caused by incorporation of Actinomycin D or profla­vine into dsDNA when interrogating the modified electrode surface with electro­chemical impedance spectroscopy (EIS). Intercalation is seen as an approach for avoiding any covalently bound labels. For this purpose, monolayers of thiol-modi­fied ssDNA were assembled on a gold electrode. The influence of the modified surface on the electron-transfer properties of negatively charged reversible redox mediators such as [Fe(CN)₆]^3-/4- was investigated. Changes in physicochemical properties of the surface-assembled DNA upon hybridization and subsequently upon intercalation provoked significant changes in the charge-transfer resistance in EIS as elucidated by means of electrochemical impedance spectroscopy (EIS). These findings can be used as basis for the development of high-sensitive DNA assasy. The design of the sensing interface and the assay architecture will be presented. Moreover, a new strategy of hybri­dization signal amplification utilizing specifically modified intercalators will be dis­cussed. Enzymatic amplification for the high-sensitive detection of DNA sequences of multi-resistant germs such as Staphylococcus aureus (MRSA) using a 32 electrode microarray chip and parallel readout will be presented.

Acknowledgement Financial support by the European Commission in the framework of the project INTCHEM (MEST-CT-2005-020681) and by the Research School of the Ruhr-Universität-Bochum is acknowledged.

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