Figure 2.

Delivery of nanoparticles across the blood–brain barrier (BBB). Normal rats received hyperosmotic mannitol to open the BBB, followed by intraarterial administration of the iron oxide nanoparticles ferumoxytol (A) or ferumoxides (B, C). After ferumoxytol administration, MRI signal intensity peaks by 24 h then fades over 3 to 7 days as the nanoparticles are metabolized (A, T1W indicates T1-weighted MRI). In contrast, ferumoxides induce signal dropout in the rat brain for over a month (B, T2* indicates T2*-weighted MRI). Electron microscopy shows that ferumoxides particles (Fe) are trapped between the vascular endothelial cells and the basement membrane after BBB disruption. Panels (A) and (B) are adapted with permission from Lippincott Williams and Wilkins/Wolters Kluwer Health: Neurosurgery (Muldoon et al., 2005), ©2005. Panel (C) is modified with permission from Muldoon et al. (1999), © by American Society of Neuroradiology.