Development of electrochemical DNA hybridization biosensors based on carbon paste electrode (CPE) and gold nanoparticle modified carbon paste electrode (NGMCPE) astransducers and ethyl green (EG) as a new electroactive label is described. Electrochemical impedance spectroscopy and cyclic voltammetry techniques were applied for the investigation and comparison of bare CPE and NGMCPE surfaces. Our voltammetric and spectroscopic studies showed gold nanoparticles are enable to facilitate electron transferbetween the accumulated label on DNA probe modified electrode and electrode surface and enhance the electrical signals and lead to an improved detection limit. The immobilization of a 15-mer single strand oligonucleotide probe on the working electrodes and hybridization event between the probe and its complementary sequence as a target were investigated by differential pulse voltammetry (DPV) responses of the EG accumulated on the electrodes. The effects of some experimental variables on the performance of the biosensors were investigated and optimum conditions were suggested. The selectivity of the biosensors was studied using some non-complementary oligonucleotides. Finally the detection limits were calculated as 1.35×10 －10 mol/L and 5.16×10 －11 mol/L on the CPE and NEGCPE, respectively. In addition, the biosensors exhibited a good selectivity, reproducibility and stability for the determination of DNA sequences.
