DNA-based electrochemical biosensor using chitosan–carbon nanotubes composite film for biodetection of Pirazon

The interaction of Pirazon (PIR) with calf thymus dsDNA (doublestranded Deoxyribonucleic acid) in the solution and the immobilized DNA on chitosan–carbon nanotubes compositemodified gold electrode was investigated by electrochemical and UVVis spectroscopy techniques. In the solution interactions, spectroscopic results indicate nonintercalative binding of PIR. A competition study with methylene blue, as an intercalative probe, was applied to confirm the binding mode of PIR. PIR showed an oxidation peak at 1.1 V at the bare Au electrode. When dsDNA was added into the PIR solution, its peak current decreased. Au electrode modified with single wall carbon nanotube (SWCNT) and chitosan (CS) decorated with the dsDNA was tested to determine PIR content in solution. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to characterize the electrochemical properties of the modified electrode. The modified electrode surface has good reproducibility and stability. The modified electrode exhibited linear detection range, 5×109 to 5×105 M, with a detection limit of 1×1010 M.