In vivo cell tracking is a promising tool to improve our understanding of certain
biological processes (circulating tumour cells migration, immune cells activity).
Fluorescence microscopy ensures a high resolution and a good sensitivity. The latter is
however limited by the high tissue autofluorescence and poor visible light penetration
depth.
We present the synthesis and characterization of Zn-Cu-In-Se / ZnS (core/shell) QDs
made of low toxicity materials. These QDs exhibit a bright emission centred around 800
nm, where absorption and scattering of tissues are minimal. These nanocrystals are
coated with a new surface chemistry, which yields small and bright probes in the cell
cytoplasm for several days after labelling.
These QDs also present a fluorescence lifetime much longer (150 ns) than the tissue
autofluo- rescence (fluorescence imaging system, we show that we can efficiently discriminate the
intracellular QDs signal from autofluores- cence in an ex vivo sample and thus increase
the detection sensitivity of labelled cells into tissues. We also report preliminary results
obtained in an in vivo sample.