Gold nanoparticles decorated reduced graphene oxide nanolabel for voltammetric immunosensing

This study describes the development and testing of a simple and novel enzyme-free nanolabel for the detection and signal amplification in a sandwich immunoassay. Gold nanoparticles decorated reduced graphene oxide (rGOAu) was used as the nanolabel for the quantitative detection of human immunoglobulin G (HIgG). The rGOAu nanolabel was synthesised by one pot chemical reduction of graphene oxide and chloroauric acid using sodium borohydride. The pseudo-peroxidase behaviour of rGOAu makes the nanolabel unique from other existing labels. The immunosensing platform was fabricated using self-assembled monolayers of 11-mercaptoundecanoic acid (11-MUDA) on a gold disc electrode. The covalent immobilisation of antibody was achieved through the bonding of the carboxyl group of 11-MUDA and the amino group of the antibody using chemical linkers [1-ethyl-3-(3-dimethylaminopropyl)carbodiimide] and N-hydroxysuccinimide. The fabricated immunosensor exhibited a linear range that included HIgG concentrations of 62.5-500 ng ml^-1. The sensor was also used for the testing of HIgG in the blood sample.