Investigation of Immunosensor Modification With Reduced Graphene Oxide with Au Nanoparticles on Glassy Carbon Electrode in Label-free for Escherichia coli Detection

 Escherichia coli  (E.coli) is an essential bacterial indicator in the control of pharmaceutical quality and other similar fields. There are some biosensors designed for its detection based on electrochemical transduction methods. A biosensor with reduced graphene oxide was modified. Traditional methods are time-consuming and high prices, so in this study a new biosensor with modification of reduced graphene oxide (rGO) as a kind of carbon composition on glassy carbon electrode (GCE) with Au Nanoparticles (Au NPs) decoration was used for E. coli detection.

 Reduced graphene oxide (rGO)  modified on glassy carbon electrode (GCE) and chronoamperometric and reduction methods were used for Au NPs decoration and it was completed with polyclonal E. coli antibody and 0.5 W/V% Bovine Serum Albumin (BSA) solution. Morphology and structure of rGO and Au NPs in GCE/rGO/Au NPs/ E. coli polyclonal antibody/ BSA biosensor were verified by SEM (Scanning Electron Microscope) during modification steps. E. coli detection in dissimilar samples was performed by Square-Wave Voltammetry (SWV) and Cyclic Voltammetry (CV) techniques which were set in 0.1M phosphate buffer solution (PBS) (pH 7.4) mixed with 0.5mM acetaminophen. In comparison with the biosensor, the classical method of detection was performed with serial dilutions of E. coli ATCC 8739 (1×101–1×108 CFU/ml) which was cultured on media. 

 Despite the two methods used to stabilize Au NPs, scanning electron microscope (SEM) images showed that the current difference did not increase due to gold particles. Its modification had not significant change in current and it was not a successful experiment for E.coli detection.

 Compared with the plate method, biosensor couldn’t substitute with conventional methods for E. coli detection.