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Proceedings Paper

Quantum dots as contrast agents for endoscopy: mathematical modeling and experimental validation of the optimal excitation wavelength
Author(s): Mathieu Roy; Ralph S. DaCosta; Robert Weersink; George Netchev; Sean R. H. Davidson; Warren Chan; Brian C. Wilson
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Paper Abstract

Our group is investigating the use of ZnS-capped CdSe quantum dot (QD) bioconjugates combined with fluorescence endoscopy for improved early cancer detection in the esophagus, colon and lung. A major challenge in using fluorescent contrast agents in vivo is to extract the relevant signal from the tissue autofluorescence (AF). Our studies are aimed at maximizing the QD signal to AF background ratio (SBR) to facilitate detection. This work quantitatively evaluates the effect of the excitation wavelength on the SBR, using both experimental measurements and mathematical modeling. Experimental SBR measurements were done by imaging QD solutions placed onto (surface) or embedded in (sub-surface) ex vivo murine tissue samples (brain, kidney, liver, lung), using a polymethylmethacrylate (PMMA) microchannel phantom. The results suggest that the maximum contrast is reached when the excitation wavelength is set at 400±20 &mgr;m for the surface configuration. For the sub-surface configuration, the optimal excitation wavelength varies with the tissue type and QD emission wavelengths. Our mathematical model, based on an approximation to the diffusion equation, successfully predicts the optimal excitation wavelength for the surface configuration, but needs further modifications to be accurate in the sub-surface configuration.

Paper Details

Date Published: 27 February 2007
PDF: 12 pages
Proc. SPIE 6448, Colloidal Quantum Dots for Biomedical Applications II, 644812 (27 February 2007); doi: 10.1117/12.700954
Show Author Affiliations
Mathieu Roy, Univ. of Toronto (Canada)
Ralph S. DaCosta, Univ. of Toronto (Canada)
Robert Weersink, Univ. of Toronto (Canada)
George Netchev, Univ. of Toronto (Canada)
Sean R. H. Davidson, Ontario Cancer Institute, Univ. Health Network (Canada)
Warren Chan, Univ. of Toronto (Canada)
Brian C. Wilson, Univ. of Toronto (Canada)
Ontario Cancer Institute, Univ. Health Network (Canada)


Published in SPIE Proceedings Vol. 6448:
Colloidal Quantum Dots for Biomedical Applications II
Marek Osinski; Thomas M. Jovin; Kenji Yamamoto, Editor(s)

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