Here, a sandwich-type electrochemiluminescence (ECL) immunosensor was designed for ultrasensitive determination of hepatitis B virus surface antigen (HBsAg) based on signal amplification using dendrimeric-quantum dots structure. In this respect, dendrimer of the PAMAM was employed as the carrier for immobilizing CdTe@CdS quantum dots (QDs) and the secondary antibody (Ab2) due to the many functional amine groups which can be amplified significantly the ECL signal of QDs and hence, improved the sensitivity of the proposed method. The PAMAM-QD-Ab2 nanoprobe was constructed by covalent attachment of Ab2 on CdTe@CdS QDs tagged PAMAM. Firstly, the primary antibody of HBs (Ab1) was immobilized on the surface of the carboxyl-modified magnetic nanoparticles (MNPs). Then, sandwich immunosensor assembled on the surface of Au electrode by external magnetic forces. MNPs enhances the electron transfer between the nanoprobe and the electrode and also, their large surface area leading to immobilize more Ab1. Under optimal conditions, the constructed immunosensor showed a wide linear range from 3 fgmL-1 to 0.3 ng mL-1 with a detection limit of 0.81 fg mL-1 at a S/N ratio of 3 for the HBsAg detection. The proposed ECL immunosensor exhibited high sensitivity, good analytical performance and excellent stability. Moreover satisfactory results from determination of HBsAg in human serum was obtained, thus has great potential for clinical detection of HBsAg.
