Figure 5

TEM images of PEG-coated and uncoated 23 nm gold spheres throughout the gastrointestinal tract. TEM images of gold nanospheres found throughout the gastrointestinal tract of a mouse following oral gavage: in the stomach (I) 10 minutes post-gavage (PG), small intestine (II) 2.5 hours PG, cecum (III) 4 hours PG, large intestine (IV) 5 hours PG and feces (V) 24 hours PG. Micrographs from animals gavaged with PEG-coated particles are shown in panel A for all five insets, uncoated particles are shown in panel B for all insets except IV (large intestine) in which uncoated particles are shown in panel C. As seen in snap shots throughout the GIT, PEG-coated particles remain well dispersed while uncoated particles appear to agglomerate extensively, beginning immediately after dosing, as seen in the stomach (I). In addition to a contrast in agglomeration behavior, PEG-coated particles are frequently seen adjacent to the absorptive surfaces within the GIT (I-III) while uncoated particles are only observed in the tissue lumen, distal from the surface (I-IV). As seen in the small intestine (II), panel C shows the microvilli of a mouse dosed with uncoated particles being entirely void of particles. In image IV, large intestine, the thick mucin layer can be seen in panel B, potentially explaining why both PEG-coated and uncoated particles were only observed in the lumen of the tissue.