Complexing of heavy metals with DNA and new bioaffinity method of their determination based on amperometric DNA-based biosensor

Abstract

The immobilized single-stranded DNA (ssIDNA) has been found to be a very effective biospecific analytical reagent when used in a newly developed bioaffinity method of the determination of heavy metals based on the amperometric DNA-based biosensor. This has been concluded from the comparative study of the complexing of heavy metals with double-stranded DNA, single-stranded DNA, and ssIDNA, using Fe(III) and Cu(II) as a model (metal/nucleotide ratio and stability constants are maximum for ssIDNA), from the study of adsorption of Fe(III), Cu(II), Pb(II), and Cd(II) on nitrocellulose membranes, containing single-stranded DNA, and from the determination of their binding constants with ssIDNA. According to these data, the chosen heavy metals can be lined up in a series of binding strengths with ssIDNA: Cu(II) > Pb(II) > Fe(III) > Cd(II). The method of the determination of heavy metals is based on biospecific preconcentration of metal ions on the biosensor followed by the destruction of DNA-metal complexes with ethylenediaminetetraacetate and voltammogram recording has been proposed. The lower detection limits are 4.0 × 10-11, 1.0 × 10-10, 1.0 × 10 -9, and 5.0 × 10-9 M for Cu(II), Pb(II), Cd(II), and Fe(III), respectively. The heavy metals have been assayed in nnilticomponent environmental and biological systems such as natural and drinking water, milk, and blood serum samples. © 2005 American Chemical Society.