4 March 2014 Time-gated imaging of near-infrared quantum dots for in vivo cell tracking
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Abstract
In vivo cell tracking is a promising tool to improve our understanding of certain biological processes (circulating tumor cell migration, immune cell activity). Several cell tracking techniques have been developed like MRI or PET but remain ill adapted to detect rare and individual cells because of their low spatial resolution and limited sensitivity. Fluorescence detection is a promising alternative. Its sensitivity is however limited by the high tissue autofluorescence and poor visible light penetration depth. To overcome these limitations, we have developed a novel cell imaging modality, based on nearinfrared quantum dots (QDs) allowing long term cell labeling and a sensitive detection based on time-gated wide field fluorescence microscopy. We present the synthesis and characterization of Zn-Cu-In-Se / ZnS (core/shell) QDs composed of low toxicity materials. These QDs exhibit a bright emission centered around 800 nm, where absorption and scattering of tissues are minimal. These nanocrystals are coated with a new surface chemistry, which yields small, stable, bright and individual probes in the cell cytoplasm for several days after the labeling. These QDs also present a fluorescence lifetime much longer (150-200 ns) than tissue autofluorescence (5-10 ns). By combining a pulsed excitation source to a time-gated fluorescence imaging system, we show that we can efficiently discriminate the QD signal from autofluorescence and thus increase the detection sensitivity of labeled cells into tissues.
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S. Bouccara, E. Giovanelli, G. Sitbon, N. Lequeux, T. Pons, V. Loriette, A. Fragola, "Time-gated imaging of near-infrared quantum dots for in vivo cell tracking", Proc. SPIE 8947, Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues XII, 89471B (4 March 2014); doi: 10.1117/12.2039983; https://doi.org/10.1117/12.2039983
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