Development of Biosensor Comprising DNA as Affinity Ligand

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A molecular recognition function employed in sensing techniques such as biosensors is usually provided by proteins including enzymes and antibodies. On the other hand, DNA is also an important host molecule in biological affinity reactions. We have developed in this study a new modification chemistry for immobilizing double-helical DNA on metal electrode. Some possible application of the electrode for bioaffinity-based sensing has been studied.DNA double strands were immobilized on a Au electrode via chemisorption, i.e., a co-ordination to Au with a sulfur-containing moiety. Cyclic voltammograms of ferrocyanide/ferricyanide redox couple were taken with the DNA-modified electrode. When adding quinacrine, the well-known antimalarial drug, the peak currents increased with increasing concentration of the drug. The peak current showed almost a linear relationship with the concentration of quinacrine in the range of 10^<-7>-5x10^<-7>M and then saturated beyond the concentration of 8x^<-7>M.The binding of the cationic drug to the immobilized DNA should reduce the electrostatic repulsion between the polyanionic DNA and the anionic redox couple ions, resulting in the enhancement of the current intensity.In addition, the DNA-modified electrode was found to be useful for"gene sensor". The sensor comprising DNA as a receptive component can be used for not only the measurement of DNA but also the evaluation of the interaction between DNA and a family of DNA-binding drugs.