Highly sensitive exonuclease III-assisted fluorometric determination of silver(I) based on graphene oxide and self-hybridization of cytosine-rich ss-DNA

Abstract

We report on a method for selective fluorometric determination of Ag(I) based on the use of graphene oxide (GO) and by exploiting exonuclease III-assisted signal amplification. In the presence of Ag(I), the self-hybridization of cytosine-rich ss-DNA labeled with the fluorescent tag FAM leads to the formation of a ds-DNA that is cleaved by the catalytic action of Exo III. In the absence of Ag(I) ions, however, the tagged ss-DNA is adsorbed on the surface of GO and its fluorescence is quenched. As a result, the induction of the process by Ag(I) leads to a strong amplification of fluorescence. The method allows Ag(I) ions to be determined in the 1 to 250 nM concentration range, with a 0.1 nM detection limit. The recoveries range from 93.3 to 105.1 %, with RSDs of <8.2 %.