Electrochemical behavior of gatifloxacin at multi-walled carbon nanotube paste electrode and its interaction with DNA

The electrochemical oxidation of an antibacterial drug, gatifloxacin (GTF), at multi-walled carbon nanotube paste electrode was studied employing cyclic and differential pulse voltammetry methods. The effect of scan rate, pH, different electrolytes, pulse amplitude and accumulation time on electrochemical behavior of GTF were investigated. GTF shows a well-defined oxidation peak at +1.05 V in acetate buffer of pH 5.0 +/- 0.01. Under optimized conditions, the peak current is linear over the concentration range 2.13x10(-5)-1.7x10(-4) M with detection limit of 4.5x10(-9) M. The applicability of the proposed method is further extended to in vitro determination of the drug in biological fluids. Differential pulse voltammetry and UV-VIS absorption techniques were employed to probe the interaction between GTF and calf thymus DNA. The addition of ds-DNA to the analyte containing GTF results in a decrease of the peak current and a positive shift of the peak potential of GTF in differential pulse voltammetry analysis, indicating the dominance of the intercalating interaction. The spectroscopic data also confirm the interaction between GTF and ds-DNA. The combining constant (beta) and combining number (m) of GTF-mDNA were also determined.