Magnetic nanocomposite of anti-human IgG/COOH–multiwalled carbon nanotubes/Fe3O4 as a platform for electrochemical immunoassay

Abstract

An electrochemical immunosensing method was developed based on a magnetic nanocomposite. The multiwalled carbon nanotubes (MWCNTs) were treated with nitric acid to produce carboxyl groups at the open ends. Then, Fe3O4 nanoparticles were deposited on COOH–MWCNTs by chemical coprecipitation of Fe2+ and Fe3+ salts in an alkaline solution. Goat anti-human IgG (anti-hIgG) was covalently attached to magnetic nanocomposite through amide bond formation between the carboxylic groups of MWCNTs and the amine groups of anti-hIgG. The prepared bio-nanocomposite was used for electrochemical sensing of human tetanus IgG (hIgG) as a model antigen. The anti-hIgG magnetic nanocomposite was fixed on the surface of a gold plate electrode using a permanent magnet. The hIgG was detected using horseradish peroxidase (HRP)-conjugated anti-hIgG in a sandwich model. Electrochemical detection of hIgG was carried out in the presence of H2O2 and KI as substrates of HRP. Using this method, hIgG was detected in a concentration range from 30 to 1000ngml−1 with a correlation coefficient of 0.998 and a detection limit of 25ngml−1 (signal/noise=3). The designed immunosensor was stable for 1month.