PhDNovel fluorescent quantum dots of small size, tunable light emission wavelength and
high compatibility with biological systems are of great significance to light microscopy
super-resolution imaging. In this thesis, colloidal germanium quantum dots of 3.8
nm size have been investigated as a novel fluorescent probe for cell imaging.
Two single molecule localisation super-resolution methods were explored: one
utilised QDs blinking statistics and the other one was based on intrinsic QDs size
dispersion. We found that the blinking super-resolution strategy which combined the
usage of blinking QDs and spinning disk confocal imaging has led to less than seven
minutes collection time for 2000 image frames. High precision temporal separation of
single molecules has been achieved on Ge QDs and CdSe QDs labelled fixed Hela cell.
The spectroscopic super-resolution strategy that combined the usage of size dependent
light emission QDs and spectra imaging, resulted in a 1.6 seconds data acquisition
time. Spectroscopic separation and high precision single molecule localisation has
been demonstrated using Ge QDs and CdSe QDs labelled fixed Hela cell samples.
We compared various localisation algorithms when applied to the two superresolution
methods we studied. We found that they did not work well with our
data. Consequently, we developed two MATLAB-based localisation algorithms. The
first algorithm used the independent component analysis (ICA) model to analyse the
blinking stochastic imaging data, whilst the other used the Gaussian mixed model
(GMM) to analyse the spectroscopic separation imaging data.
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We also conducted comparative toxicity tests of these novel Ge QDs with a
typical of-the-shelf system. The cell toxicity of Ge QDs was found to be less than
that of CdSe/ZnS QDs. For instance, 25 nM Ge QDs in 1 mL Hela cell solution did
not cause observable cells apoptosis in 24 hours. It caused 15% cells apoptosis after
3 days, rather than 35% for CdSe QDs at the same concentration. In addition, long
term live cell imaging with QDs revealed that Ge QDs had not significantly changed
cellular morphology within a 90 hour period.China Scholarship Council
and Queen Mary, University of Londo
