Figure 9.

Ultrastructural images of the “proton sponge effect” and “endosome escape”. (a) The endosomes in the cytoplasm contained QDs and cell debris. Rectangle B in a is magnified in b. (b) The bilayer plasma membrane of endosomes was ruptured in several parts (arrow), the outflow of QDs spilled along the ruptures and remained as a lane of QDs (left, white arrowhead). Subsequently, particles with a high density of QDs were homogeneously distributed in the cytoplasm (black arrowhead). Large and small endosomes joined together and a channel observed between them at a high density of QDs (right, white arrowhead). (c): The upper half of a large endosome is shown in b. The nano-sized spots indicated the locations of single QDs and/or larger clusters of QDs (black arrowhead) from an endosome rupture in the cytoplasm (arrow). QD, quantum dots.