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Doping Method Determines Para- or Superparamagnetic Properties of Photostable and Surface-Modifiable Quantum Dots for Multimodal Bioimaging
journal contribution
posted on 2018-05-30, 00:00 authored by Florian Part, Christoph Zaba, Oliver Bixner, Tilman A. Grünewald, Herwig Michor, Seta Küpcü, Monika Debreczeny, Elisabetta De Vito Francesco, Andrea Lassenberger, Stefan Schrittwieser, Stephan Hann, Helga Lichtenegger, Eva-Kathrin EhmoserSemiconductor
quantum dots (QDs) are widely used for optical applications
and bioimaging. In comparison to organic dyes used for fluorescent
labeling, QDs exhibit very high photostability and can be further
surface modified. Equipping QDs with magnetic properties (mQDs) makes
it possible to combine fluorescence and magnetic resonance imaging
analyses. For this purpose, we have prepared water-dispersible and
magnetic CdTe/ZnS mQDs, whereby ferrous ions are selectively incorporated
in either their cores or their shells. This study aims at understanding
the differences in optical, structural, and magnetic properties between
these core- and shell-doped mQDs. Field-dependent isothermal magnetic
susceptibility measurements show that shell-doped mQDs exhibit paramagnetic
and their core-doped equivalents superparamagnetic behavior
near room temperature. Shell doping results in about 1.7 times higher
photoluminescence quantum yields and 1.4 times higher doping efficiency
than core doping. X-ray diffraction patterns reveal that core doping
leads to defects in the lattice and hence to a severe decrease in
crystallinity, whereas shell doping has no significant impact on the
crystal structure and consequently fewer disadvantages regarding the
mQD’s quantum yield. These selective doping approaches, particularly
shell doping, allow for the tailored design of paramagnetic QDs having
modifiable and biocompatible particle surfaces. The organic ligandsin
this study N-acetyl-l-cysteinesufficiently
prevent leakage of toxic metal ions, as shown by cytotoxicity assays
with HepG2 cells. Confocal laser scanning microscopy shows that mQDs
are internalized by these cells and accumulated near their nuclei.
This study shows that biocompatible, fluorescent, and paramagnetic
QDs are promising photostable labels for multimodal bioimaging.
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shell doping resultsMultimodal Bioimaging Semiconductor quantum dotsshell dopingsusceptibility measurements showphotoluminescence quantum yieldscore dopingDoping Method Determines ParaHepG 2 cellsresonance imaging analysesbiocompatible particle surfacesX-ray diffraction patternsshell-doped mQDs exhibitConfocal laser scanning microscopySurface-Modifiable Quantum Dots
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