15 April 2008 Self-assembled quantum dot-bioconjugates: characterization and use for sensing proteolytic activity
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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.
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Igor L. Medintz, Igor L. Medintz, Thomas Pons, Thomas Pons, Kim E. Sapsford, Kim E. Sapsford, Philip E. Dawson, Philip E. Dawson, Hedi Mattoussi, Hedi Mattoussi, } "Self-assembled quantum dot-bioconjugates: characterization and use for sensing proteolytic activity", Proc. SPIE 6945, Optics and Photonics in Global Homeland Security IV, 69450Q (15 April 2008); doi: 10.1117/12.782174; https://doi.org/10.1117/12.782174

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