An electrochemical sensing interface based on aptamer conjugated gold nanoparticles/reduced graphene oxide for the determination of malathion

The widespread use of organophosphorous pesticides primarily in agriculture has raised human health and environmental concerns which has led us to the development of a sensing interface that is able to detect the organophosphorous (OP) compound. Herein, we report gold nanoparticles (AuNPs) decorated reduced graphene oxide (rGO) modified on screen printed carbon electrode (SPCE) as the support for aptamer immobilization to develop an electrochemical impedimetric aptasensor for the detection of malathion, one of the most common used OP compounds. Graphene oxide was electrochemically reduced on SPCE and further modified with AuNPs to produce AuNPs/rGO-modified SPCE which was then utilized for the immobilization of thiolated DNA aptamer by self-assembly method. The modified SPCE was characterized for structural changes as compared to bare SPCE by using Fourier�transform infra red (FTIR) and scanning electron microscopy (SEM) for surface morphology. The stepwise modification process was characterized by cyclic voltammetry (CV). The detection was carried out by using EIS where it is based on the variation of electron transfer resistance associated with the formation of malathion-aptamer complex at the modified electrode surface. The result shows that the value of charge transfer resistance increased upon binding of malathion to the aptamer-modified electrode indicating the successful formation of malathion-aptamer complex that blocks the electron transfer.