exert. For functionally active cells, such as HUVEC or C17.2 cells that are actively being explored in cell transplantation studies,31 assessing cell functionality is an important aspect. It is important to note that dead cells will logically not have any more functionality and therefore only those conditions are selected at which no cytotoxicity was observed, being 60 nM for QDotsZnSe and 80 nM for QDotsInP. In the present study, the three cell types used offer optimal conditions for assessing important functional parameters. The widely spread HUVEC cells are ideally suited to investigate the effect of the QDots on cell morphology and cytoskeletal architecture.30 For QDots that are ideally suited for bioimaging applications in live cells, it is essential that the intracellular presence of the particles does not affect cell structure. Some particles, including QDots, have been found to disturb cell morphology and cell cytoskeleton and some studies have shown direct effects on actin fibers.12,47 The HUVEC cells were therefore -tubulin, stained for F-actin and after which the spreading of the cells was analyzed by confocal microscopy and image analysis, as performed previously.43 Figure 5A shows representative images of the cells which display a clear spreading and nice cytoskeletal architecture for untreated control cells and cells labeled with low concentrations of QDots. Cell area distribution was then analyzed (Figure 5B), which shows a clear decrease in cell spreading at 40 nM for QDotsZnSe and 50 nM for QDotsInP. These effects may in part be due to the induction of ROS, but when cells were treated with 5 mM N-acetylcysteine (NAC), a free radical scavenger that reduced cellular ROS levels to near control values (data not shown), the decrease in cell spreading could only be partially overcome (Figure 5C). The results demonstrate that oxidative stress plays a major role in the cytotoxic effects of the QDots, but that for both types of particles, other mechanisms also played an important role, such as cytoskeletal rearrangements and reductions in cell spreading.
exert. For functionally active cells, such as HUVEC or C17.2 cells that are actively being explored in cell transplantation studies,31 assessing cell functionality is an important aspect. It is important to note that dead cells will logically not have any more functionality and therefore only those conditions are selected at which no cytotoxicity was observed, being 60 nM for QDotsZnSe and 80 nM for QDotsInP. In the present study, the three cell types used offer optimal conditions for assessing important functional parameters. The widely spread HUVEC cells are ideally suited to investigate the effect of the QDots on cell morphology and cytoskeletal architecture.30 For QDots that are ideally suited for bioimaging applications in live cells, it is essential that the intracellular presence of the particles does not affect cell structure. Some particles, including QDots, have been found to disturb cell morphology and cell cytoskeleton and some studies have shown direct effects on actin fibers.12,47 The HUVEC cells were therefore stained for F-actin and -tubulin, after which the spreading of the cells was analyzed by confocal microscopy and image analysis, as performed previously.43 Figure 5A shows representative images of the cells which display a clear spreading and nice cytoskeletal architecture for untreated control cells and cells labeled with low concentrations of QDots. Cell area distribution was then analyzed (Figure 5B), which shows a clear decrease in cell spreading at 40 nM for QDotsZnSe and 50 nM for QDotsInP. These effects may in part be due to the induction of ROS, but when cells were treated with 5 mM N-acetylcysteine (NAC), a free radical scavenger that reduced cellular ROS levels to near control values (data not shown), the decrease in cell spreading could only be partially overcome (Figure 5C). The results demonstrate that oxidative stress plays a major role in the cytotoxic effects of the QDots, but that for both types of particles, other mechanisms also played an important role, such as cytoskeletal rearrangements and reductions in cell spreading.
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