Core–shell magnetic nanoparticles applied for immobilization of antibody on carbon paste electrode and amperometric immunosensing

An amperometric immunosensor was developed based on immobilizing antibody on the surface of modified CdFe2O4 magnetic nanoparticles. The goat anti-human IgG antibody (anti-IgG) was first covalently immobilized to core–shell (CdFe2O4–SiO2) magnetic nanoparticles, which were surface-modified with amino groups on the surface. The resulting bio-magnetic nanoparticles were attached to the surface of carbon paste electrode (CPE) with the help of a permanent magnet. A sandwich immunoassay was performed on the bio-magnetic nanoparticles monolayer supported by CPE. The assay comprised first loading of IgG on the bio-magnetic nanoparticles monolayer, then blocking in BSA solution, followed by incubation in anti-IgG-HRP conjugate, and finally the amperometric detection with hydroquinone as a mediator. The linear range for IgG assay was 0.51–30.17 μg ml−1 and the detection limit was 0.18 μg ml−1. The simple manipulations of construction and low cost were main advantages of proposed immunosensing method.