Quantum-dots based electrochemical immunoassay of interleukin-1α

We describe a quantum-dot (QD, CdSe@ZnS) based electrochemical immunoassay to detect a protein biomarker, interleukin-1 alpha (IL-1 alpha). QD conjugated with anti-IL-la antibody was used as a label in an immunorecognition event. After a complete sandwich immunoreaction among the primary IL-1 alpha antibody (immobilized on the avidin-modified magnetic beads), IL-1 alpha, and the QD-labeled secondary antibody, QD labels were attached to the magnetic-bead surface through the antibody-antigen immunocomplex. Electrochemical stripping analysis of the captured QDs was used to quantify the concentration of IL-1 alpha after an acid-dissolution step. The streptavidin-modified magnetic beads and the magnetic separation platform were used to integrate a facile antibody immobilization (through a biotin/ streptavidin interaction) with immunoreactions and the isolation of immunocomplexes from reaction solutions in the assay. The voltammetric response is highly linear over the range of 0.5-50 ng ml(-1) IL-1 alpha, and the limit of detection is estimated to be 0.3 ng ml(-1) (18 pM). This QD-based electrochemical immunoassay shows great promise for rapid, simple, and cost-effective analysis of protein biomarkers. (C) 2007 Elsevier B.V. All rights reserved.