Fe-based nanoparticulate metallic alloys as contrast agents for magnetic resonance imaging.

Pharmaceutical grade magnetic colloidal dispersions have been prepared from iron alloys synthesized by laser pyrolysis. The colloids were obtained by simultaneous dispersion and coating of the particles with dextran in a strong alkaline solution. Both powders and dispersions have been analyzed in terms of microstructural characteristics, chemical composition and magnetic properties. The powders consist of uniform spherical nanoparticles (12 nm of diameter) showing a metallic core encapsulated into an iron-oxide shell. On the other hand, the colloidal dispersions consist of magnetic particles-aggregates with hydrodynamic sizes of approximately 75 nm. Magnetic resonance images of rats were taken after the intravenously administration of the Fe colloidal dispersions, and compared with those obtained using a commercial iron oxide magnetic resonance imaging contrast agent. The results showed a contrast improvement of 60% in the liver with respect to the commercial sample, which suggests that this product could be a suitable contrast agent for NMR imaging of liver and spleen.