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Journal of Biomedicine and Biotechnology
Volume 2007 (2007), Article ID 79169, 6 pages
http://dx.doi.org/10.1155/2007/79169
Research Article

Time-Resolved Analysis of a Highly Sensitive Förster Resonance Energy Transfer Immunoassay Using Terbium Complexes as Donors and Quantum Dots as Acceptors

1Physikalische Chemie, Institut für Chemie und Interdisziplinäres Zentrum für Photonik, Universität Potsdam, Karl-Liebknecht-Straße 24-25, Potsdam-Golm 14476, Germany
2Laboratoire de Chimie Moléculaire, Ecole Européenne de Chimie, Polymères, Matériaux (ECPM), UMR 7509 CNRS, 25 rue Becquerel, 67087 Strasbourg Cedex, France

Received 2 April 2007; Accepted 16 July 2007

Academic Editor: Marek Osinski

Copyright © 2007 Niko Hildebrandt et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

CdSe/ZnS core/shell quantum dots (QDs) are used as efficient Förster Resonance Energy Transfer (FRET) acceptors in a time-resolved immunoassays with Tb complexes as donors providing a long-lived luminescence decay. A detailed decay time analysis of the FRET process is presented. QD FRET sensitization is evidenced by a more than 1000-fold increase of the QD luminescence decay time reaching ca. 0.5 milliseconds, the same value to which the Tb donor decay time is quenched due to FRET to the QD acceptors. The FRET system has an extremely large Förster radius of approx. 100 Å and more than 70% FRET efficiency with a mean donor-acceptor distance of ca. 84 Å, confirming the applied biotin-streptavidin binding system. Time-resolved measurement allows for suppression of short-lived emission due to background fluorescence and directly excited QDs. By this means a detection limit of 18 attomol QDs within the immunoassay is accomplished, an improvement of more than two orders of magnitude compared to commercial systems.