Voltammetric study of the ion-exchange binding of non-electroactive metal cations to DNA-modified surfaces
Abstract
We describe a simple electrochemical protocol for studying the ion-exchange binding of non-electroactive ions, specifically mono- and divalent metal cations of biological relevance (Mg2+, Ca2+, and K+), to DNA-modified surfaces. After incubation in a dilute solution of multiply charged transition metal complex (5.0 µM [Ru(NH3)6]Cl3), gold electrodes modified with thiolate–DNA monolayers respond to the presence of these non-electroactive metal cations by producing significant changes in the cyclic voltammograms (i.e., decrease of the integrated charge and shift of formal potential) of the surface-bound redox complex ([Ru(NH3)6]3+). The divalent cations (particularly Mg2+) can be detected at very low concentrations (<10 µM), while the on-set value for K+ is substantially higher (50 mM). The equilibrium binding constants for Mg2+ and Ca2+ to DNA-modified surfaces were calculated.