A label-free electrochemical aptasensor for sensitive edifenphos detection in rice†
Herein, for the first time, we developed a facile and sensitive method for the determination of edifenphos (EDI). An aptamer (APT) covalently attached on the surface of a glassy carbon electrode (GCE) was covered with a nanocomposite composed of reduced graphene oxide (rGO) and functionalized multi-walled carbon nanotubes (f-MWCNTs). To promote electron transfer, amplify the signal and increase the stability of the electrode, this nanocomposite was deposited on the GCE in two steps. In the first step, graphene oxide (GO) and f-MWCNTs were deposited on the GCE (f-MWCNT–GO/GCE). In the next step, electrochemical reduction afforded the rGO and f-MWCNT nanocomposite (f-MWCNT–rGO). Following that, aminated APT was immobilized on the f-MWCNT–rGO/GCE through the covalent coupling of APT and the carboxylate groups of f-MWCNT–rGO (APT/f-MWCNT–rGO/GCE). This modified electrode was evaluated by electrochemical methods, including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The obtained data from DPV, under optimized conditions, showed a wide linear range from 0.001 to 1300 nmol L−1, and the detection limit (LOD) was 0.1 pmol L−1. Moreover, the fabricated aptasensor exhibited good stability, reproducibility, and rapid response for EDI in real samples.