Voltammetric behavior of osmium-labeled DNA at mercury meniscus-modified solid amalgam electrodes. Detecting DNA hybridization

The complex of osmium tetroxide with 2,2'-bipyridine has been utilized as a probe of DNA structure and all electroactive marker of DNA in DNA hybridization sensors. It produces several voltammetric signals, the most negative of them has been observed only at mercury electrodes. This signal is of catalytic nature affording a high sensitivity of DNA determination. The catalytic current due to evolution of hydrogen in voltammetry of DNA modified by complex of osmium tetroxide with 2,2'-bipyridine (DNA-Os,bipy) was studied. Solid amalgam electrodes (modified with mercury menisci) of silver (m-AgSAE), copper (m-CuSAE), gold. and of combined bismuth and silver, Were used as possible Substitutes for mercury electrodes. Besides the hanging mercury drop electrode (HMDE), the catalytic Current was observed only on m-AgSAE and m-CuSAE. Electrodes of gold and bismuth amalgams did not give the catalytic Current. The detection limit of DNA-Os,bipy on HMDE was 0.1 ng mL(-1) (RSD = 2.3% N = 11) and oil m-AgSAE 0.2 ng mL(-1) (RSD = 3.1.%, N = 11). The m-AgSAE was successfully applied as a detection electrode in double-surface DNA hybridization experiments offering highly specific discrimination between complementary (target) and nonspecific DNAs, as well as determination of the length of a repetitive DNA sequence. The m-AgSAE has proved a convenient alternative to the HMDE or carbon electrodes used for similar purposes in previous work.