Ultrasensitive detection of clenbuterol by quantum dots based electrochemiluminescent immunosensor using gold nanoparticles as substrate and electron transport accelerator

A simple, rapid and ultrasensitive electrochemiluminescent (ECL) competitive immunoassay based on gold nanoparticles (GNPs) and CdSe quantum dots (QDs) has been developed for the detection of clenbuterol (CLB). Transmission electron microscope image (TEM), photoluminescence spectra, ultraviolet-visible absorption spectra and dynamic light scattering (Dls) were used to characterize the QDs. Meanwhile the GNPs/Ovalbumin-CLB/anti-CLB-QDs immunosensor was fabricated by layer by layer using GNPs as substrate and electron transport accelerator. The sensor was characterized with electrochemical impedance spectra (EIS), and a strong ECL emission of the modified electrode could be observed during the cathodic process of S2O82- and QDs in air-saturated PBS buffer containing of 0.1 M K-2 S-2 O-8 and 0.1 M KCl (pH 7.4). Under the optimum conditions, the ECL signal depended linearly on the logarithm of the clenbuterol concentration within a range from 0.02 ng/mL to 50 ng/mL, and a detection limit was 0.0084 ng/mL, much lower than those reported literatures. The immunosensor showed good stability, specificity and fabrication reproducibility. It has been applied to detect practical samples with the satisfactory results. This immunosensing strategy exhibits a great prospect for screening of trace amount of CLB residue and opens a new avenue for application of QDs in ECL biosensing. (C) 2013 Elsevier B.V. All rights reserved.