The development of an experimental setup capable of contrasting fluorescent materials by their recombinative lifetimes
in an imaging mode is discussed. Such materials might include molecular dyes and QDs. The system is comprised of a
standard upright microscope fitted with an imaging CCD, and a white light laser that illuminates a circular region within
the field of view with variable period excitation pulse trains. Different fluorescent species within this region absorb the
laser light and fluoresce with a recombination lifetime dependent on material composition and local environment.
Species with differing fluorescent lifetimes can be distinguished in an imaging mode by their contrasting intensity
response to the pulse train at the range of different pulse frequencies. The technique is discussed and applied to samples
containing both CdTe (705 nm) and CdSe (611 nm) QDs, showing contrast between long (70-100 ns) and (relatively)
short (25-35 ns) lifetime within an image.
We have used flow-cytometry together with computational modeling of quantum dot portioning during cell division to
identify population distributions of proliferating cells. The objective has been to develop a robust assay of integrated
cellular fluorescence which reports the extent of cellular bifurcation within a complex population and potentially
provides profiles of drug resistance, cell clonality and levels of aneuploidy in tumour cells. The implementation of a data
analysis program based on genetic algorithms provides a complete description of the proliferation dynamics and gives
values for the inter-mitotic time, the partitioning ratio of quantum dots between daughter cells and their associated