Self-assembled quantum dot-bioconjugates: characterization and use for sensing proteolytic activity

Igor L. Medintz; Thomas Pons; Kim E. Sapsford; Philip E. Dawson; Hedi Mattoussi

doi:10.1117/12.782174

15 April 2008 Self-assembled quantum dot-bioconjugates: characterization and use for sensing proteolytic activity

Igor L. Medintz, Thomas Pons, Kim E. Sapsford, Philip E. Dawson, Hedi Mattoussi

Proceedings Volume 6945, Optics and Photonics in Global Homeland Security IV; 69450Q (2008) https://doi.org/10.1117/12.782174
Event: SPIE Defense and Security Symposium, 2008, Orlando, Florida, United States

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 (k_on and k_off) and the binding constant (K_d). We find that self-assembly is rapid with an equilibrium constant K_d^-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.

Citation Download Citation

Igor L. Medintz, Thomas Pons, Kim E. Sapsford, Philip E. Dawson, and 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); https://doi.org/10.1117/12.782174

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