A novel PAMAM dendrimers-Au nanostructure was prepared and used to develop an amplified CdSe quantum dots (QDs) probe for ultrasensitive electrochemiluminescence (ECL) immunoassay. The unique dendrimer-encapsulated Au nanoparticles have numerous functional groups for loading enough QDs, and the ECL of QDs was enhanced by the localized surface plasmon resonance (LSPR) of gold nanoparticles (Au NPs). After the PAMAM dendrimer was used to form an effective immobilization matrix for biomolecules, the capture antibody (Ab1) was covalently conjugated to the dendrimers. In the presence of the target human IgG (Ag), the secondary antibody (Ab2) modified PAMAM-Au-CdSe QDs signal probe was attached to the electrode. On the basis of the amplified ECL signal of the CdSe QDs, an ultrasensitive signal-on ECL immunosensor was developed. The PAMAM-Au-CdSe QDs nanostructure opens a new promising material direction for ECL biosensing; this method shows considerable promise for diverse clinical applications. (C) 2015 Elsevier B.V. All rights reserved.