Abstract
A dual-signal amplification strategy for electrochemiluminescence (ECL) immunosensor was designed based on L-cysteine capped CdSe quantum dots (QDs) and gold nanoparticles (AuNPs) conjugated horseradish peroxidase (HRP) for highly sensitive detection of ractopamine (RAC). The electrochemical detection was based on the HRP catalyzed o-phenylenediamine (OPD) to consume the self-produced H2O2, which has been extensively used as a co-reactant of QDs. The enzymatic reaction rate was proportional to the amount of HRP bound to the electrode. In the presence of RAC standard solution, the immobilized RAC coating antigen competed with RAC solution for the Ab-AuNPs-HRP complexes. With the increase of the RAC concentration, the amount of immobilized HRP decreased, which led to the increase of ECL intensity. Under optimized conditions, ECL intensity changed linearly with the logarithm of RAC concentration in the range of 0.005–500 ng mL−1 with the detection limit of 0.0017 ng mL−1 (S/N = 3). The ECL immunosensor possesses high sensitivity, satisfied reproducibility and selectivity, and may provide a feasible route for practical application of RAC detection.
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