Novel systems based on colloidal magnetic nanocrystals (NCs), potentially useful as superparamagnetic (SP) contrast agents for magnetic resonance imaging (MRI) have been investigated. The NCs we have studied comprise organic-capped single-crystalline maghemite (γ-Fe2O3) cores possessing controlled sizes and shapes. We have comparatively examined spherical and tetrapod-like NCs, the latter being branched particles possessing four arms which depart out at tetrahedral angles from a central point. The as-synthesized NCs are passivated by hydrophobic surfactant molecules and thus are fully dispersible in nonpolar media only. The NCs have been made soluble in aqueous solution by applying a procedure based on the surface intercalation and coating with an amphiphilic polymer shell. NMR relaxivities R1 and R2 were compared with ENDOREM®, one of the standard commercial SP-MRI contrast agent. We found that the spherical NCs exhibit R1 and R2 relaxivities slightly lower than those of ENDOREM®, over the whole frequency range; on the contrary, tetrapods show relaxivities about one order of magnitude lower. The physical origin of such difference in relaxivities between tetrapod- and spheres-based nanostructures is under investigation and it is possibly related to different sources of the magnetic anisotropy.
|Titolo:||Magnetic properties of novel superparamagnetic MRI contrast agents based on colloidal nanocrystals|
LASCIALFARI, ALESSANDRO (Secondo)
|Parole Chiave:||Colloidal nanocrystal; Contrast agent; Magnetic properties and NMR; Magnetic resonance imaging|
|Settore Scientifico Disciplinare:||Settore FIS/01 - Fisica Sperimentale|
|Data di pubblicazione:||2008|
|Digital Object Identifier (DOI):||10.1016/j.jmmm.2008.02.064|
|Appare nelle tipologie:||01 - Articolo su periodico|