Ultrasensitive electrochemiluminescent salbutamol immunoassay with dual-signal amplification using CdSe@SiO2 as label and gold nanoparticles as substrate

The authors describe a dual signal amplification electrochemiluminescent (ECL) immunoassay for ultrasensitive determination of the β-adrenergic agonist salbutamol (SAL). It is based on the use of gold nanoparticles (AuNPs) and silica-coated quantum dots of the type CdSe@SiO 2 . The CdSe@SiO 2 nanoparticles (NPs) were synthesized by water-in-oil reversed-phase microemulsion. Amino-modified NPs were then prepared and used as an ECL signal probe for detection of SAL in the presence of K 2 S 2 O 8 . The gold NPs with their large specific surface carry the antigen, facilitate electron transfer and improve the electrochemical reaction efficiency of QDs and K 2 S 2 O 8 . The ECL immunosensor was fabricated by coating the AuNPs with antigen, and then SAL competed with SAL antigen for the binding sites of the antibody on the CdSe@SiO 2 NPs. Under optimized conditions, the ECL intensity is linearly related to the logarithm of the SAL concentration in the range from 0.001 to 1000 ng mL −1 , with a lower detection limit of 0.17 pg mL −1 (at an S/N ratio of 3). The assay has good operational stability, is highly sensitive and selective. It is judged to possess a wider scope in that it may be applied to many other small molecule analytes for which adequate antibodies are available. Schematic of a dual signal amplification electrochemiluminescent immunoassay for ultrasensitive detection of the β-adrenergic agonist salbutamol based on the use of gold nanoparticles and CdSe@SiO 2 .