Ultrasensitive electrochemiluminescent brombuterol immunoassay by applying a multiple signal amplification strategy based on a PAMAM-gold nanoparticle conjugate as the bioprobe and Ag@ Au core shell nanoparticles as a substrate

A multiple amplified electrochemiluminescence immunosensor is described for the determination of the illicit beta-adrenergic agonist brombuterol. Firstly, cystein-coated silver nanowires (SCNW) were modified with polyamidoamine dendrimers (PAMAM) and then immobilized on a glassy carbon electrode (GCE). Then, Ag@ Au core/shell nanoparticles (NPs) were deposited on the surface of the modified GCE via gold-nitrogen bonds. The use of Cys-coated silver nanowires accelerates the electron transfer process and also prevents the aggregation of the Ag@ Au NPs. The nanocomposites on the GCE have a large surface and outstanding electrical conductivity. It can carry a large amount of coating antigen to amplify the ECL signal. Moreover, PAMAM-Au-CdSe quantum dot bioprobes were prepared, and the unique dendrimer-encapsulated gold nanoparticles with numerous functional amino groups were employed to load abundant activated CdSe quantum dots for further enhancement of the ECL signal. On the basis of signal amplification of the SCNW-PAMAM-Ag@ Au-based immunosensor and the PAMAM-Au-CdSe quantum dot bioprobes. The assay has a wide linear range that extends over the 0.001-1000 ng . mL-1 brombuterol concentration range and a lower detection limit of 37 fg.mL(-1). The method is well reproducible, stable and specific. It was applied to the determination of brombuterol in spiked samples of pork and feed where it gave satisfactory recoveries.