Development of a label-free electrochemical immunosensor based on carbon nanotube for rapid determination of clenbuterol

We have fabricated a label-free electrochemical immunosensor for the detection of clenbuterol, a kind of β-agonist. Clenbuterol was covalently linked to multi-wall carbon nanotubes (MWCNTs) through a two-step process using 1-(3-(dimethylamino)-propyl)-3-ethylcarbodiimide and N-hydroxysulfo-succinimide as crosslinkers. The clenbuterol-MWCNT conjugates were cast on a glassy carbon electrode. Cyclic voltammetry and differential pulse voltammetry were employed to monitor the fabrication steps of immunoreaction system using the redox probe of K3Fe(CN)6. In the presence of monoclonal antibody against clenbuterol, the redox peak current of [Fe(CN)6]3−/4− was decreased, presumably due to that antibody in solution could adsorb on the electrode surface modified clenbuterol-MWCNT conjugates. The selected monoclonal antibody showed very high sensitivity and specificity for clenbuterol, and was used for the detection and quantitative determination of clenbuterol in solution with a competitive mechanism. This approach provided a detection limit of 0.32 ng mL−1. Accurate detection of clenbuterol in spiked animal feeds was demonstrated by comparison with conventional ELISA assays and LC–MS method.