Here, a sandwich-type electrochemiluminescence (ECL) immunosensor for ultrasensitive determination of HBsAg was designed based on signal amplification with dendrimeric-quantum dots structures. First, the primary antibody of HBs (Ab1) was immobilized on the surface of the carboxyl-modified magnetic nanoparticles (MNPs). Then, the PAMAM dendrimer with many amine functional groups was employed as the carrier for immobilizing CdTe@CdS quantum dots (QDs) and the secondary antibody (Ab2) which can amplify the ECL signal of QDs significantly and improve the sensitivity of the proposed method. Dendrimer increasing loading of CdTe@CdS-Ab2 labels, while ECL response from CdTe@CdS QDs enhanced 4 folds compared to the unamplified protocol. Furthermore, MNPs enhances the electron transfer between the nanoprobe and the electrode and also, their large surface area leads to immobilize more Ab1. Under the optimal conditions, the constructed immunosensor showed a wide linear range from 3 fg mL-1 to 0.3 ng mL-1 with the detection limit of 0.80 fg mL-1 (S/N ratio of 3) for HBsAg detection. The proposed ECL immunosensor exhibited good analytical performance and excellent stability and it was applied for HBsAg detection in human serum samples with satisfactory results.
