Turkish Journal of Chemistry




An electrochemical biosensor for the voltammetric detection of DNA sequences related to the bloom-forming genera of cyanobacteria, Microcystis spp., is described. A specific DNA ``probe'' is designed based on sequence polymorphism within the 16S ribosomal DNA (rDNA) of the Microcystis spp. These single-stranded probes were immobilized onto carbon paste electrode (CPE) with the adsorption at a controlled potential. The probes were hybridized with the complementary ``target'' sequences at the electrode. The formed hybrids on the electrode surface were evaluated by differential pulse voltammetry (DPV) and cyclic voltammetry (CV) using methylene blue (MB) and tris (2,2' -- bipyridine) ruthenium (II) chloride ([Ru(bpy)_{3}]^{2+}) as the labels of hybridization. The response of the probe modified CPE to the exposure of the non--complementary oligonucleotide proves the specificity of the hybridization with the target. The two-bases mismatch could also be discriminated and specific detection of Microcystis spp. was achieved by using the difference between the voltammetric peaks of MB and [Ru(bpy)_{3}]^{2+} obtained with the probe and hybrid-modified CPEs. The detection of Microcystis spp. target DNA from real tap water and river water samples was also achieved.

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