Time-gated cell imaging using long lifetime near-infrared-emitting quantum dots for autofluorescence rejection

International audience; Fluorescence imaging is a promising technique for the detection of individual cell migration. Its sensitivity is, however, limited by a high tissue autofluorescence and a poor visible light penetration depth. In order to solve this problem, the fluorescence signal peak wavelength should lie in an absorption and diffusion free region and should be distinguishable, either spectrally or temporally, from the autofluorescence background. We present, here, the synthesis and characterization of low toxicity Zn-Cu-In-Se/ZnS core/shell quantum dots. Their fluorescence emission wavelength peaks around 800 nm, where the absorption and scattering of tissues are minimal. They are coated with a new ligand, which yields small, stable, and bright individual probes in the live cell cytoplasm, even 48 h after the labeling. Furthermore, these near-infrared-emitting quantum dots have a long fluorescence lifetime component (around 150 ns) compared to autofluorescence (