High payload Gd(iii) encapsulated in hollow silica nanospheres for high resolution magnetic resonance imaging.

For clear MR imaging of blood vessels, a long blood circulation time of effective T contrast agents is necessary. Nanoparticulate MR contrast agents are much more effective owing to their enhanced relaxivity, a result of reduced tumbling rates, and large payloads of active magnetic species. PEGylated yolk-shell silica nanospheres containing high payloads of Gd(iii) with cross-linking ligands are synthesized and evaluated as a blood-pool magnetic resonance contrast agent. The hydrophilic PEG coating and the microporous silica shell allow water exchange while keeping the multi-nuclear Gd species from leaching out. These Gd(iii)-containing yolk-shell silica nanoparticles with PEGylated surfaces give excellent resolution and contrast in magnetic resonance angiography images of vasculature in rat brains.