Electrochemical detection of DNA hybridization is viable alternative to optical and radio-labelled techniques.  The benefits of using biosensors based on electrochemical systems are high sensitivity, possible development of miniature systems interfaced to electronic devices as well as low cost of operation and small sample requirements.

We have developed an electrochemical DNA hybridization assay, based on deposition of films, consisting of single-strand DNA cross-linked with an osmium-based redox polymer, on gold electrodes. A signal, corresponding to hybridization between the immobilized probe ssDNA and a biotin-conjugated target DNA is amplified by addition of glucose oxidase-avidin conjugate and glucose substrate¹. The interaction between target DNA, avidin-GOx and osmium redox polymer layer generates a bioelectrocatalytic current in the presence of glucose. Catalytic currents corresponding to oxidation of glucose scale with complementary DNA concentration.

An improvement in recognition layer stability is achieved by providing an anchoring layer of cysteamine, via self-assembly, onto the underlying gold electrode. Further improvements in layer stability may be achieved by modification of carbon electrodes via aryl diazonium electroreduction to provide a grafted anchoring layer ².

References: 

1. Kavanagh, P.; Leech, D. Anal. Chem. 2006, 78, 2710
2. Boland, S. et al. Langmuir, 2008, 24, 6351.

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2. Modification of gold microelectrodes for detection of DNA hybridization
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