In this study a simple and selective methodology was used to develop a novel electrochemical DNA biosensor for determination of furazolidone. This biosensor was made of pretreated carbon paste electrode(CPE) that modified with TiO 2 -reduced graphene oxide(RGO) decorated with ds-DNA, This simple and inexpensive biosensor was performed through the interaction of small molecules such as furazolidone with the DNA. The first part of this project explains the use of DNA-based biosensor for the determination of trace amount of furazolidone, which is a kind of nitrofuran. First, the intraction of salmon sperm ds-DNA with furazolidone on the surface of ds-DNA modified carbon paste was studied. The oxidation signals of guanine and adenine were used as probs to study the intraction. By intraction of furazolidone with the DNA, the oxidation currents of guanine and adenine were decresed at the modified-CPE, using differential pulse voltammetry. A linear dependence of the guanine and adenine oxidation signals were observed for the determination of furazolidone concentration in the range of 1.0–10.0 and 10.0–150.0 pmol L -1 (at the optimum conditions) with a detection limit of 0.55 and 0.43 pmol L -1 respectively for guanine and adenine. The relative standard deviations for five replicate measurements of 10.0 pmol L -1 furazolidone were 4.3% and 4.8%, respectively for guanine and adenine. This method is successfully applied for determination of afew amount of furazolidone in real samples. In the second part of this study, the inhibitory effect of some metal ions such as (copper, nickel, zinc and cobalt) on the destruction of DNA by furazolidone has been investigated. Furazolidone could make a complex with, copper, nickel, zinc and cobalt ions by capturing the RNO 2 -? (after furazolidone is reduced by biological reductants). This studied was performed using electrochemical impedance spectroscopy (EIS) using carbone paste electrode (CPE) and UV–Vis spectroscopy.
