Electrochemical behavior of neomycin at DNA-modified gold electrodes

Deoxyribonucleic acid (DNA) modified gold electrodes are prepared by the dry adsorptive method and the electrochemical behavior of neomycin and the influence of Pb(II) are studied by cyclic voltammetry, chronocoulometry, differential pulse voltammetry. It is found that in 0.01 M phosphate-buffered saline (PBS) buffer solutions (pH 7.3) at DNA/Au electrode neomycin exhibits an irreversible cathodic peak (E_p = 0.489 V), which is more positive and less sensitive compared with that at bare gold electrodes (E_p = 0.423 V). In the presence of Pb(II) the peak shifts toward positive with its height increasing. Moreover, the peak height is linear to neomycin concentration over the range of 0.15-57 μM. The interaction of Pb(II)-neomycin complex with calf thymus DNA is also studied by calculating the binding constants (K) of the Pb(II)-neomycin complex to DNA and binding site size (s) from voltammetric data (1.0 × 10⁷ M⁻¹ and 4 bp, respectively).