Electrochemical DNA detection using supramolecular interactions.

An electrochemical DNA detection format has been developed to allow simple and rapid assays with downsized instruments. Since naphthalene diimide derivatives are known to bind to double stranded DNA (dsDNA) with threading intercalation, they are stabilized by pseudo-catenane formation. For example, ferrocenylnaphthalene diimide (FND) can be efficiently concentrated on dsDNA, thus enabling its electrochemical detection. Since dsDNA is formed between single stranded target DNA and DNA probe, the target DNA can be detected electrochemically, using DNA probe-immobilized on the electrode. Further stabilization of naphthalene diimide derivatives as a complex with dsDNA on the electrode is expected to lead to more precise and selective detection of target DNA. This approach was realized by the formation of inclusion complexes of ferrocene with β-cyclodextrin (β-CD) for the FND-dsDNA complexes on the electrode. Combination of adamantylnaphthalene diimide (AND) and ferrocenyl-β-CD (Fc-CD) gave new supramolecular DNA detection assays coupled with DNA probe-immobilized electrodes. The electrochemical signal increased only upon formation of the Fc-CD/AND complex bound to dsDNA on the electrode. Naphthalene diimide carrying ferrocene and β-CD realized "signal on" type detection of dsDNA in homogenous solution. Naphthalene diimide carrying two dithiolene termini provided a new method to immobilize dsDNA on the gold electrode that may be suitable for the electrochemical detection of target DNA.