A novel label-free electrochemical immunesensor for ultrasensitive detection of LT toxin using prussian blue@gold nanoparticles composite as a signal amplification

Abstract

In the current study, a novel electrochemical label-free immunosensor is proposed for sensitive detection of heat-labile enterotoxin (LT) from Escherichia coli. Firstly, a glassy carbon electrode (GCE) was modified by a mixture containing reduced graphene oxide/room temperature ionic liquid (rGO/RTIL) composite. Then, simultaneous electrodeposition of prussian blue and gold nanoparticles led to formation of prussian blue@gold nanoparticles (PB@GNPs) composite on the electrode surface. The modified electrode was characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. After immobilization of anti-LT and blocking the unreacted sites with BSA (bovine serum albumin), the analytical performance of the proposed immunosensor was evaluated under optimal conditions (i.e. optimal pH, incubation time and temperature of incubation). Square wave voltammetry (SWV) was used to determine different concentrations of the LT antigen. The linear dynamic range of the proposed immunosensor was from 0.01 to 50 µg/mL and the detection limit of the immunosensor was found to be 0.0023 µg/mL. An acceptable selectivity in the real sample, long-term stability and goodreproducibility made the fabricated immunosensor a good candidate for detecting LT.