"On-off" switchable electrochemical affinity nanobiosensor based on graphene oxide for ultrasensitive glucose sensing.

A novel "smart" electrochemical affinity nanobiosensor with "on-off" switchable property was designed for the ultrasensitive determination of glucose. The sensing approach was based on the glucose-ConA-dextran competitive system induced charge evolution in the use of graphene oxide (GO) as transducer element, resulting in the enhancement of interfacial electron transfer kinetics between the redox probe and the electrode. As concanavalin A (ConA) constituent was pH-sensitive, when the ConA-DexP/GO film electrode switched in probe Fe(CN)(6)(3-/4-) solution between pH 4.0 and 8.0, the film was cycled between the "on" and "off" states by the electrostatic attraction and repulsion of Fe(CN)(6)(3-/4-) to and from the electrode surface. Upon introduction of glucose into the ConA-DexP/GO complex at the "off" state, glucose competed with DexP for ConA and displaced ConA from the GO platform, resulting in gradual decrease of the surface negative charge as well as the resistance of probe for electron communication on the sensor surface, and making the switching from "off" state to "on" state simultaneously. This ultrasensitive glucose nanobiosensor had a broad linearity between the decrease in electron transfer resistance (ΔR) and the glucose concentration over a range from 5.0 μM to 9.0 mM with a detection limit as low as 0.34 μM. The proposed method showed potential application for fabricating novel biosensors and bioelectronic devices.