Paramagnetic dysprosium oxide nanoparticles and dysprosium hydroxide nanorods as T2 MRI contrast agents

We report here paramagnetic dysprosium nanomaterial-based T-2 MRI contrast agents. A large r(2) and a negligible r(1) is an ideal condition for T-2 MR imaging. At this condition, protons are strongly and nearly exclusively induced for T-2 MR imaging. The dysprosium nanomaterials fairly satisfy this because they are found to possess a decent r(2) but a negligible r(1) arising from L + S state 4f-electrons in Dy(III) ion (H-6(15/2)). Their r(2) will also further increase with increasing applied field because of unsaturated magnetization at room temperature. Therefore, MR imaging and various physical properties of the synthesized D-glucuronic acid coated ultrasmall dysprosium oxide nanoparticles (d(avg) = 3.2 nm) and dysprosium hydroxide nanorods (20 x 300 nm) are investigated. These include hydrodynamic diameters, magnetic properties. MR relaxivities, cytotoxicities, and 3 tesla in vivo T-2 MR images. Here, MR imaging properties of dysprosium hydroxide nanorods have not been reported so far. These two samples show r(2)s of 65.04 and 181.57 s(-1) mM(-1), respectively, with negligible r(1)s at 1.5 tesla and at room temperature, no in vitro cytotoxicity up to 100 mu M Dy, and clear negative contrast enhancements in 3 tesla in vivo T-2 MR images of a mouse liver, which will be even more improved at higher MR fields. Therefore, D-glucuronic acid coated ultrasmall dysprosium oxide nanoparticles with renal excretion can be a potential candidate as a sensitive T-2 MRI contrast agent at MR field greater than 3 tesla. (c) 2012 Elsevier Ltd. All rights reserved.