The Ag+-G interaction inhibits the electrocatalytic oxidation of guanine--a novel mechanism for Ag+ detection.

The heavy metal ions-nucleobases interaction is an important research topic in environmental and biochemical analysis. The presence of the silver ion (Ag(+)) may influence the formation of oxidation intermediate and the electrocatalytic oxidation activity of guanine (G), since Ag(+) can interact with guanine at the binding sites which are involved in the electrocatalytic oxidation reaction of guanine. According to this principle, a new electrochemical sensor for indirectly detecting Ag(+) based on the interaction of Ag(+) with isolated guanine base using differential pulse voltammetry (DPV) was constructed. Among the heavy metal ions examined, only Ag(+) showed the strongest inhibitory effect on the electrocatalytic oxidation of guanine at the multi-walled carbon nanotubes modified glassy carbon electrode (CNTs/GC). And the quantitative study of Ag(+) based on Ag(+)-G sensing system gave a linear range from 100 nM to 2.5 μM with a detection limit of 30 nM. In addition, this modified electrode had very good reproducibility and stability. The developed electrochemical method is an ideal tool for Ag(+) detection with some merits including remarkable simplicity, low-cost, and no requirement for probe preparation.