Fig. 3.

Transmission electron microscopy analysis of nanoparticle-treated cells. RAW264 cells were imaged via transmission electron microscopy after treatment with copper oxide nanoparticles for 4 h (panels A, C, and D) and 24 h (panel B). The copper nanoparticles are concentrated in multivesicular bodies and in lysosomes, as expected for professional phagocytic cells. Cells treated for 24 h show much larger, fusioned lysosomes than cells treated for only 4 h. Various sizes of copper oxide can be seen, from the 200- to 300-nm aggregates present in the medium (thick arrows) to the 30- to 50-nm sizes of the initial particles (thin arrows) and even smaller sizes such as 10 nm (arrowheads), as can be expected from the intracellular dissolution of the nanoparticles.