Interaction of metal ions and DNA films on gold surfaces: an electrochemical impedance study.

Electrochemical impedance spectroscopy (EIS) has been used to investigate the effects of a number of metal ions with DNA films on gold surfaces exploiting [Fe(CN)6](3-/4-) as a solution-based redox probe. Alkaline earth metal ions Mg2+, Ca2+, trivalent Al3+, La3+ and divalent transition metal ions Ni2+, Cu2+, Cd2+ and Hg2+ have been selected in this study and the results are compared with previous studies on the effects of Zn2+ on the EIS of DNA films. All experimental results were evaluated with the help of equivalent circuits which allowed the extraction of resistive and capacitive components. For all metal ions studied here, addition of the metal ions causes a decrease in the charge transfer resistance. The difference of charge transfer resistance (DeltaR(ct)) of ds-DNA films in the presence and absence of the various metal ions is different and particular to any given metal ion. In addition, we studied the EIS of ds-DNA films containing a single A-C mismatch in the presence and absence of Ca2+, Zn2+, Cd2+ and Hg2+. DeltaR(ct) values for ds-DNA films with a single A-C mismatch is smaller than those of fully matched ds-DNA films.