Inorganic nanoparticle-based T-1 and T-1/T-2 magnetic resonance contrast probes

Magnetic resonance imaging (MRI) yields high spatially resolved contrast with anatomical details for diagnosis, deeper penetration depth and rapid 3D scanning. To improve imaging sensitivity, adding contrast agents accelerates the relaxation rate of water molecules, thereby greatly increasing the contrast between specific issues or organs of interest. Currently, the majority of T-1 contrast agents are paramagnetic molecular complexes, typically Gd(III) chelates. Various nanoparticulate T-1 and T-1/T-2 contrast agents have recently been investigated as novel agents possessing the advantages of both the T-1 contrast effect and nanostructural characteristics. In this minireview, we describe the recent progress of these inorganic nanoparticle-based MRI contrast agents. Specifically, we mainly report on Gd and Mn-based inorganic nanoparticles and ultrasmall iron oxide/ferrite nanoparticles.