Electrochemical sensor based on reduced graphene oxide, gold nanoparticles and DNA aptamer for the detection of malathion

The widespread utilization of organophosphorous (OP) compounds in the environment has raised significant concerns regarding both human health and the well-being of our ecosystems. These OPs find common application as pesticides and insecticides, but their potential use as chemical warfare agents (CWAs) by terrorists has further escalated these concerns. Consequently, the development of chemical sensors with exceptional sensitivity and specificity towards OPs has become a matter of utmost importance. Among the various available techniques, electrochemical sensors have emerged as particularly valuable due to their stability, adaptability for on-site detection, and straightforward measurement protocols. In this study, we have engineered an electrochemical sensor designed for the detection of malathion. This sensor leverages the unique properties of gold nanoparticles (AuNPs) coupled with reduced graphene ooxide (rGO), which are integrated onto a screen-printed carbon electrode (SPCE) to serve as the sensing platform. The process involved the electrochemical reduction og graphene oxide on the SPCE, followed by modification with AuNPs to yield an AuNPs/rGO-modified SPCE. This modified electrode was then employed for the immobilization ofthiolated DNA aptamer through a self-assembly technique. Characterization techniques such as cyclic voltammetry (CV),Fourier-Transform Infra-Red spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM) were employed to confirm the successful surface modification of the SPCE. Detection of malathion was achieved using a differential pulse voltammogram (DPV) revealing a noteworthy decrease in the Faradaic peak current upon the binding of malathion to the aptamer-modified electrode. This outcome underscores the successful formation of a malathion-aptamer complex, which impedes electron transfer, thus demonstrating the sensor's efficacy in detecting malathion.