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Proceedings Paper

Self-assembled quantum dot-bioconjugates: characterization and use for sensing proteolytic activity
Author(s): Igor L. Medintz; Thomas Pons; Kim E. Sapsford; Philip E. Dawson; Hedi Mattoussi
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Paper Abstract

We present a characterization of the metal-affinity driven self-assembly between luminescent CdSe-ZnS core-shell semiconductor quantum dots (QDs) and either peptides or proteins appended with various length terminal polyhistidine tags. We first monitor the kinetics of self-assembly between surface-immobilized QDs and proteins/peptides under flow conditions (immobilized). To accomplish this, the QDs were immobilized onto functionalized substrates and then exposed to dye-labeled peptides/proteins. By using evanescent wave excitation of the substrate, self-assembly was assessed by monitoring the time-dependent changes in the dye fluorescence. This configuration was complemented with experiments using freely diffusing QDs and proteins/peptides (solution-phase) via energy transfer between QDs and dye-labeled proteins/peptides. Cumulatively, these measurements allowed determination of kinetic parameters, including association and dissociation rates (kon and koff) and the binding constant (Kd). We find that self-assembly is rapid with an equilibrium constant Kd-1 in the low nM. We next demonstrate the importance of understanding this self-assembly by creating QD-peptide bioconjugates which we employ as substrates to monitor the cleavage activity of proteolytic enzymes. This confirms that metal-affinity interactions can provide QD-bioconjugates that are functional and stable.

Paper Details

Date Published: 15 April 2008
PDF: 10 pages
Proc. SPIE 6945, Optics and Photonics in Global Homeland Security IV, 69450Q (15 April 2008); doi: 10.1117/12.782174
Show Author Affiliations
Igor L. Medintz, U.S. Naval Research Lab. (United States)
Thomas Pons, U.S. Naval Research Lab. (United States)
Kim E. Sapsford, U.S. Naval Research Lab. (United States)
Philip E. Dawson, The Scripps Research Institute (United States)
Hedi Mattoussi, U.S. Naval Research Lab. (United States)

Published in SPIE Proceedings Vol. 6945:
Optics and Photonics in Global Homeland Security IV
Craig S. Halvorson; Daniel Lehrfeld; Theodore T. Saito, Editor(s)

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