Figure 4

Different intracellular areas were scanned for S and Cd. Figures A-F represent the areas selected in figure 3 and figures A'-F' show the corresponding S/Cd ESI image. Image B and B' show a homogenous distribution of QDs within an intracellular vesicle with a specific signal for S/Cd, whereas other images are only related to noisy unspecific S/Cd background. No further analysis on these structural origins was performed, but it is assumed that the structures present in A, D and F are contaminants of TEM embedding and staining with heavy metals, whereas the structures in C and E possibly represent protein or lipid aggregates. All scale bars equate to 50 nm.