A label-free electrochemical DNA sensor based on ZrO2/poly(thionine)/CNT modified electrode and its application for detecting CaMV35S transgene gene sequence

Abstract

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.