Label-free impedimetric immunosensor based on one-step co-electrodeposited poly-(pyrrole-co-pyrrole-1-propionic acid) and reduced graphene oxide polymer modified layer for the determination of melamine

Abstract

A label-free electrochemical impedimetric immunosensor was developed to monitor melamine, and it was successfully applied for the detection of melamine in spiked dairy samples. The poly (pyrrole-co-pyrrole-1-propionic acid) and reduced graphene oxide polymer layer (rGO-PPYPPA) were co-electrodeposited on the electrode using a one-pot method, thus obtaining a copolymer layer with favorable electrochemical properties. A competitive immunoassay was used for quantitative analysis of melamine. The rGO-PPYPPA copolymer improved the conductivity of the sensor and provided adequate anchor sites for antibody binding, thus enhancing immuno-binding. The specific immune-interactions at the electrode surface that restrict the electron transfer of the redox probe Fe(CN)63−/4− lead to changes in electrochemical impedance, and the changes in impedance correlated to specific concentrations of melamine. The immunosensor displays a wide detection range (10−11−10−2 mol L−1), low limit of detection (1.2 × 10−11 mol L−1) and acceptable recovery (84.6%–100.3%) in real samples. The results provide a simple and versatile impedimetric immunosensing platform, with great potential for real-world applications.