Electrochemical investigation of neutral red binding to DNA at the surface

The interaction of neutral red (NR) with double-stranded calf thymus DNA was investigated by electrochemical methods using a DNA-modified glassy carbon (GC-DNA) electrode. The results were compared with those obtained at a bare glassy carbon (GC) electrode. The findings showed that although the kinetic of the electron transfer process remains reversible similar to that of using GC electrode, the formal potential of NR (E-0') was more positive when using GC-DNA electrode. GC-DNA electrode enables the enrichment of the concentration of NR for the chosen times on the electrode surface. The ratio of the binding constants for the oxidized and reduced forms of the bound species was obtained through comparing the formal potentials of NR obtained using the modified and bare surfaces. A binding isotherm for NR at GC-DNA electrode was obtained from coulometric titrations indicated a Langmuiran behavior for the NR adsorption on DNA layer, and gave an affinity constant equal to 2.76 x 10(4) 1 mol(-1). (C) 2004 Elsevier B.V. All rights reserved.