A DNA biosensor with [Ru(DA-bpy)3]Cl2(DA-bpy:4,4'-diamino-2,2'-bipyridine) (RuL) as the electrochemical probe was prepared on pyrolytic graphite electrode (PGE) through the supramolecular interaction between RuL complex and DNA template. Cyclic voltammetry of RuL-DNA film showed a pair of stable and reversible peaks corresponding to the Ru(III)/Ru(II) redox potential of -0.165 V versus Ag|AgCl in pH 7.4 0.1 mol·L-1 Tris-HCl. The electron transfer was expected across the double-strand DNA by an "electron tunneling" mechanism. When the DNA biosensor was immerged in gold (III) buffer solution, the current peak signal (I) of the RuL-DNA supramolecular depressed and △I was linear in the concentrationrange of Au ion from 1 × 10-7 to 2 × 10-5 mol·L-1 with a regression coefficient of 0.9879. The detection limit was 5 × 10-8 mol·L-1. The developed procedures were applied to the analysis of synthetic samples of real materials with good sensitivity and selectivity.
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