Electrochemical enzyme-linked immunoassay in a DNA hybridization sensor |
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Authors: | E Pale?ek R KizekL Havran S BillovaM Fojta |
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Affiliation: | Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, 61265 Brno, Czech Republic |
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Abstract: | In most of the currently developed electrochemical DNA hybridization sensors short single-stranded probe DNA is immobilized on an electrode and both the hybridization and detection steps are carried out on the electrode surface. Here we use a new technology in which DNA hybridization is performed on commercially available magnetic beads and detection on solid electrodes. Paramagnetic Dynabeads Oligo(dT)25 (DBT) with covalently bound (dT)25 probe are used for the hybridization with target DNA containing adenine stretches. Target DNA is modified with osmium tetroxide,2,2′-bipyridine (Os,bipy) and the immunogenic DNA-Os,bipy adduct is determined by the enzyme-linked immunoassay with electrochemical detection. Electroinactive 1-naphthyl phosphate is used as a substrate and the electroactive product (1-naphthol) is measured on the carbon electrodes. Alternatively Os,bipy-modified target DNA can be determined directly by measuring the osmium signal on the pyrolytic graphite electrode (PGE). A comparison between determinations of the 67-mer oligodeoxynucleotide on carbon electrodes using (a) the guanine oxidation signal, (b) direct determination of the DNA-Os,bipy adduct and (c) its electrochemical immunoassay showed immunoassay to be the most sensitive method. In combination with DBT, the DNA hybridization of long target deoxyoligonucleotides (such as 67- and 97-mers) and a DNA PCR product (226-base pairs) have been detected by immunoassay at high sensitivity and specificity. |
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Keywords: | Electrochemical sensor for DNA hybridization Enzyme-linked immunoassay of target DNA DNA hybridization and electrochemical detection on two different surfaces Magnetic beads with attached DNA probe Carbon electrodes Determination of osmium-modified target DNA |
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