An electrochemical aptasensor for the sensitive detection of Pb2+ based on a chitosan/reduced graphene oxide/titanium dioxide

In the present work, a composite comprising chitosan, graphene, and titanium dioxide (CS/RGO/TiO2) is successfully synthesized. From the obtained CV and EIS results, it is revealed that the CS/RGO/TiO2 can improve the electrochemical performance of the electrode and provide a better electrochemical sensing interface. A novel sensitive aptasensor based on CS/RGO/TiO2 is constructed for the detection of Pb2+. The aptamer complementary strand is assembled onto the surface of the modified electrode for hybridizing with the Pb2+ aptamer to form a DNA double strand structure. In the presence of Pb2+, the DNA duplex unwound and a stable G-quadruplex is formed because of the Pb2+ -induced aptamer conformation. Under optimal conditions, the modified electrode could detect Pb2+ in the range 1 ng L-1 to 1000 ng L-1 with a limit of detection of 0.33 ng L-1. Also, the modified electrode displays excellent repeatability, stability, and specificity against other interferential metal ions. These results indicated that the CS/RGO/TiO2 possesses great potential for the development of a variety of electrochemical aptasensors.