Electrochemical sensing of chromium-induced DNA damage: DNA strand breakage by intermediates of Chromium(VI) electrochemical reduction
DNA damage by Cr-v and/or Cr-IV intermediates of Cr-VI electrochemical reduction was detected using a supercoiled DNA-modified mercury electrode. A signal sensitive to formation of DNA strand breaks, AC voltammetric DNA peak 3, increased due to incubation of the DNA-modified electrode in micromolar solutions of Cr-VI at potentials sufficiently negative for Cr-VI reduction. Damage to DNA in solutions containing Cr-VI and a chemical reductant (ascorbic acid, AA) was observed only at relatively high chromium concentrations (hundreds of mu M). To eliminate interferences of excess Cr-VI in measurements of guanine electrochemical signals, a magnetoseparation double surface electrochemical technique was introduced. Using this approach, DNA damage in solution was detected for 50-250 mu M Cr-VI upon addition of 1 mM AA. Our results suggest a more efficient DNA damage at the electrode surface due to continuous production of the reactive chromium species, compared to DNA exposure to chromium being reduced chemically in solution.