Boron doped diamond electrodes brought a new potential in bioanalytical chemistry including studies of structure and interactions of nucleic acids. Herein, deposition conditionswere optimized to produce a set of polycrystalline BDD electrodes with comparable boron concentration in solid phase of (1.8 - 2.1) · 1021 cm-3 akin to metallic-type conductivity but with increasing sp2carbon content. Increase of[CH4]/[H2]from 0.25 % to 2.0 % during deposition led to an obvious decrease in grain size from ca.300 nm (BDD0.25) to < 100 nm (BDD2.0). Adsorption of oligodeoxynucleotides and their structural changes in the presence of K+ and Li+ ions were evaluated through enzyme-linked DNA hybridization assay in which oxidizable 1-naphthol was released from its phosphoesterbystreptavidin-alkaline phosphatase conjugate upon successful hybridization of the target oligodeoxynucleotide with a biotinylated complementary probe. With increasing sp2carbon content, the hybridization assay showed improved discrimination between a target forming guanine quadruplex (stabilized by K+ ions), yielding by 40 % - 60 % lower hybridization signal with the complementary probe, compared to the same but unstructured target oligodeoxynucleotide in the presence of Li+ions that don't stabilize the quadruplex structure. Such behaviour was observed also for commercial BDD electrode with surface roughness < 10 nm.

Charles University Faculty of Science Department of Analytical Chemistry Albertov 2038 6 128 00 Prague 2 Czech Republic

FZU Institute of Physics of the Czech Academy of Sciences Na Slovance 2 182 00 Prague 8 Czech Republic

Institute of Biophysics of the Czech Academy of Sciences Královopolská 135 612 00 Brno Czech Republic

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