A label-free electrochemical sensor for detecting the CaMV35S transgene gene sequence was reported based on a ZrO2/poly(thionine)/multiwalled carbon nanotubes modified glassy carbon electrode (ZrO2/PTH/MWCNTs/GCE). Probe oligonucleotides (p-ssDNA) were immobilized on the ZrO2 thin films via the strong affinity between the phosphate groups and ZrO2. Differential pulse voltammetry (DPV) was used to monitor DNA hybridization. Upon hybridization electrochemical signal changes were generated at the PTH-solution interface. Compared with noncomplementary target ssDNA, an obvious decrease in the peak current was observed upon p-ssDNA hybridization with complementary target ssDNA. The sensor exhibited an excellent selectivity for distinguishing three-mismatched with complementary target ssDNA and a high sensitivity for detecting complementary target ssDNA with the detection limit of 0.34 pM (S/N = 3). In addition, the sensor showed an excellent reproducibility and stability, and applied to determine the CaMV35S transgene gene sequence in samples with satisfactory results.
