An electrochemical study of safranin O binding to DNA at the surface

The interaction of safranin O (SO) with double-stranded calf thymus DNA was investigated electrochemically, using a DNA-modified glassy carbon (GC-DNA) electrode. The results were compared with those obtained using a bare GC electrode. The formal potential of SO was more negative when using the GC-DNA electrode, although the rate of heterogeneous electron transfer was not altered. The GC-DNA electrode enabled preconcentration of the SO on the electrode surface, despite the fact that the mass transfer effects in the thin DNA layer adsorbed on the surface were still observed. The diffusion coefficient of SO and the binding ratio for the oxidized and reduced forms of the bound species were obtained. A binding isotherm for SO at the GC-DNA electrode was plotted from coulometric titrations, giving a binding constant of 5.8×10⁴ L mol⁻¹.