• Bernášek, K.
• Vosmanská, Magda
• Veverka, P.
• Herynek, V.
• Dvořák, P.
• Kubíčková, L.
• Kohout, J.
• Kaman, O.
• Brázda, P.

Abstract

Magnetic nanoparticles of iron oxides have received extensive attention in the biomedical research, e.g. as prospective contrast agents for T-2-weighted magnetic resonance imaging (MRI). The ability of a contrast agent to enhance the relaxation rate of H-1 nuclei in its vicinity is quantitatively described by its relaxivity. Among the polymorphs of the iron(III) oxide, the nanoparticulate epsilon-Fe2O3, distinguished by its high magnetocrystalline anisotropy resulting in a blocked state of single-domain particles up to the Curie temperature of similar to 500 K, has never been studied as a contrast agent for MRI before. We analyzed r(1) and r(2) relaxivities of epsilon-Fe2O3 nanoparticles coated with amorphous silica, particularly with the aim to determine their dependences on the external magnetic field, temperature, and thickness of the silica coating. The r(2) relaxivity was interpreted within the motional averaging and static dephasing regimes. MRI images at 11.75 T confirmed high applicability of epsilon-Fe2O3-based contrast agents in ultra-high fields.

Topics

• nanoparticle
• impedance spectroscopy
• amorphous
• iron
• Curie temperature