Electrochemical monitoring of the interaction between mitomycin C and DNA at chitosan--carbon nanotube composite modified electrodes

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1. acceleration voltage between 5.0 and 10.0 kV with the resolution at various magnitudes: 10 µ m, 2 µ m, and 500 mm. DNA and MC immobilization onto the surface of chitosan and chitosan*CNT modified PGEs Each unmodified/modified PGE was immersed in a vial containing 110 µ L of 50 µ g/mL DNA solution for 1 h. Each electrode was then rinsed with ABS for 3 s before voltammetric transduction. Each modified PGE was immersed in a vial containing 110 µ L of 40 µ g/mL MC solution for 1 h. Each electrode was then rinsed with TBS for 3 s before voltammetric transduction. Interaction of MC with DNA at the surface of chitosan*CNT modified PGEs First 50 µ g/mL dsDNA immobilized PGEs were immersed in vials containing 110 µ L of 40 µ g/mL MC for interaction for 7.5 min. Each electrode was then rinsed with TBS for 3 s before voltammetric transduction. Voltammetric transduction CV measurements were obtained with a step potential of 25 mV, a scan rate of 100 mV/s, forward scan +0.4 to +1.2 V, reverse scan +1.2 to +0.4 V, in a redox probe containing 2 mM K3[Fe(CN)6]/K4[Fe(CN)6] (1:1) mixture prepared in 0.1 M KCl. DPV measurements were used for monitoring the MC and guanine oxidation signal before/after interac- tion. DPVs were performed in ABS with a 3-electrode system by scanning from +0.20 to +1.40 V at the pulse amplitude 50 mV and the scan rate 50 mV/s. EIS measurements The surfaces of unmodified PGEs, and chitosan and chitosan*CNT modified PGEs were characterized by EIS according to the procedure given below. Chitosan*CNT PGEs were also used to investigate the effect of interaction of MC with DNA by EIS measurement under the same conditions. EIS measurements were performed in the presence of 2.5 mM K3[Fe(CN)6]/K4[Fe(CN)6] (1:1) mixture as a redox probe prepared in 0.1 M KCl. The impedance was measured in the frequency range from 105Hz to 10 −1 Hz in a potential of open-circuit value of +0.23 V versus Ag/AgCl with a sinusoidal signal of 10 mV. The frequency interval was divided into 98 logarithmically equidistant measure points. The respective semicircle diameter corresponds to the charge-transfer resistance, Rct, the values of which are calculated using the fitting program AUTOLAB 302 (FRA, version 4.9 Eco Chemie, the Netherlands).