Abstract
Quantum dots (QDs) are small nanocrystals widely used for labelling cells in order to enable cell tracking in complex environments in vitro, ex vivo and in vivo. They present many advantages over traditional fluorescent markers as they are resistant to photobleaching and have narrow emission spectra. Although QDs have been used effectively in cell tracking applications, their suitability has been questioned by reports showing they can affect stem cell behaviour and can be transferred to neighbouring cells. Using a variety of cellular and molecular biology techniques, we have investigated the effect of QDs on the proliferation and differentiation potential of two stem cell types: mouse embryonic stem cells and tissue-specific stem cells derived from mouse kidney. We have also tested if QDs released from living or dead cells can be taken up by neighbouring cells, and we have determined if QDs affect the degree of cell-cell fusion; this information is critical in order to assess the suitability of QDs for stem cell tracking. We show here that QDs have no effect on the viability, proliferation or differentiation potential of the two stem cell types. Furthermore, we show that the extent of transfer of QDs to neighbouring cells is <4%, and that QDs do not increase the degree of cell-cell fusion. However, although the QDs have a high labelling efficiency (>85%), they are rapidly depleted from both stem cell populations. Taken together, our results suggest that QDs are effective cell labelling probes that are suitable for short-term stem cell tracking.
Highlights
Quantum dots (QDs) are fluorescent semiconductor nanocrystals, which due to their optical properties, have the potential to be used in a variety of biomedical applications [1]
We examined the effect of QDs on the viability, proliferation rate and differentiation potential of two types of stem cells: mouse embryonic stem cells and mouse kidney-derived stem cells (KSCs), a tissue-specific stem cell line isolated from postnatal mouse kidney [16]
The QDs used in this study were coated with a ZnS shell, which has been reported to prevent the release of Cd2+ ions thereby circumventing cytotoxic effects [6]
Summary
Quantum dots (QDs) are fluorescent semiconductor nanocrystals, which due to their optical properties, have the potential to be used in a variety of biomedical applications [1]. QDs have a number of advantages over traditional fluorescent markers, such as green fluorescent protein (GFP) They have a wide absorbance and narrow emission spectrum, which means that QDs of different sizes can be excited with a single light source and emit at discrete, non-overlapping wavelengths, making them ideally suited to multiplexing [2,3,4]. They are resistant to photobleaching [5], which means they have great potential for time-lapse studies. By functionalising the ZnS shell with an appropriate high affinity peptide ligand, the QDs can be targeted to surface receptors of specific cell types [9]
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