Preliminary studies of application of CdTe nanocrystals and dextran-Fe3O4 magnetic nanoparticles in sandwich immunoassay

Background: The favorable properties of water-soluble CdTe nanocrystals as novel biological luminescent label over conventional fluorescent probes have attracted considerable interest. The magnetic separation technique has widely been applied to various aspects in biotechnology in recent years. In this paper, we made use of CdTe nanocrystals and dextran-Fe3O4 magnetic nanoparticles for fluorescence immunoassay. Methods: The CdTe nanocrystals and dextran-Fe3O4 magnetic nanoparticles were applied to immunoassay for the determination of human immunoglobulin G (HIgG). A rabbit anti-HIgG antibody (primary antibody) was immobilized on magnetic nanoparticles, which was used as a solid support. A sheep anti-HIgG antibody (secondary antibody) was attached to the surface of the CdTe nanocrystals via electrostatic interaction. The immunoassay was based on a sandwich immunoreaction of primary antibody on the magnetic nanoparticles, HIgG (or serum sample), and the secondary antibody labeled with CdTe nanocrystals. Results: The CdTe label was compared with a fluorescein isothiocyanate (FITC) label. The CdTe is an order of magnitude more sensitive than the FITC. The immunoassay method was applied to determining the HIgG in practical samples and the results obtained are in good agreement with those obtained by nephelometry. Conclusion: This technique may be applied in many types of antibody-antigen system. (c) 2006 Elsevier B.V All rights reserved.