Carboxyl-modified graphene for use in an immunoassay for the illegal feed additive clenbuterol using surface plasmon resonance and electrochemical impedance spectroscopy

We report on an efficient method for the production carboxy-modified graphene (carboxy-GR), and its application to a highly sensitive immunoassay for the livestock feed additive clenbuterol. Octadecanoic acid is shown to self-assemble on carboxy-GR via intermolecular interaction. Goat anti-mouse IgG was conjugated to 1-octadecanethiol-modified carboxy-GR and then deposited by self-assembly on a C18-modified gold surface. The resulting sensor surface was used to quantify clenbuterol by both surface plasmon resonance and electrochemical impedance spectroscopy. The assay works in the 0.01 ng∙mL −1 to 10 ng∙mL −1 concentration range and the lower detection limit is 6.57 pg∙mL −1 . It is concluded that this fairly simple method can be extended to immunoassays for other food additives. Principle of sensor system and immunoassay. (i) Binding of ACG–IgG with the alkyl chain of 1-octadecanethiol through intermolecular force onto the gold substrate; (ii) absorbance of Ab CLB onto the surface of ACG-IgG; and (iii) detection of CLB using an immunoassay based on Ab CLB –ACG–IgG.