TEM analysis of AuNP14 uptake in irradiated MEFs and hESCs. (A) TEM analysis of MEFs exposed to vehicle for 48 h allows for the identification of cellular organelles. (B–C) After 48 h-exposure, AuNP14 can clearly be observed in irradiated MEFs (see inset in B), where they mostly distribute in the cytoplasm (B) but are mostly absent from the nucleus (C). (D) Cytoarchitecture of vehicle-exposed hESCs was clearly visible using TEM, including clusters of glycogen granules (arrows). (E) hESCs exposed to AuNP14 for 48 h showed an ultrastructure similar to that of control cells. (F–G) No visible AuNP14 could be detected in unstained sections of exposed hESCs (G) compared to unstained sections of control hESCs (F). The scale bar length is 500 nm for (A), (B), and (C), 50 nm for the inset in (B), 200 nm for (D), (F), and (G), and 1 µm for (E).