Abstract
For use as positive (T1) magnetic resonance imaging contrast agents (MRI-CAs), gadolinium oxide (Gd2O3) nanoparticle colloids (i.e. nanoparticles coated with hydrophilic ligands) should be stable, non-toxic, and ultrasmall in particle diameter for renal excretion. In addition, they should have a high longitudinal water proton relaxivity (r1) and r2/r1 ratio that is close to one (r2 = transverse water proton relaxivity) for high-performance. In this study, we report ultrasmall Gd2O3 nanoparticle colloids [coating material = polyacrylic acid, Mw = ∼5100 Da] satisfying these conditions. The particle diameter was monodisperse with an average value of 2.0 ± 0.1 nm. The colloidal suspension exhibited a high r1 value of 31.0 ± 0.1 s−1 mM−1 and r2/r1 ratio of 1.2, where r1 was ∼8 times higher than that of commercial Gd-chelates: the cooperative induction model was proposed to explain this. The effectiveness of the colloidal suspension as a high-performance T1 MRI-CA was confirmed by taking in vivo T1 MR images in a mouse after intravenous administration. Highly positive contrast enhancements were observed in various organs of the mouse such as the liver, kidneys, and bladder. The colloidal suspension was then excreted through the bladder.
Highlights
Magnetic resonance imaging contrast agents (MRI-CAs) allow us to discriminate between normal and abnormal tissues inside the body through the differential contrast enhancement between them.[1,2,3] This occurs owing to the differential population of the magnetic resonance imaging contrast agents (MRI-CAs) between them
The gra ing density (s), which corresponds to the average number of polyacrylic acid (PAA) coated per nanoparticle unit surface area,[33] was estimated to be 1.0 Æ 0.1 nmÀ2 using the bulk density of Gd2O3 (7.41 g cmÀ3),[34] the aforementioned estimated value of P, and the average particle diameter determined via high-resolution transmission electron microscope (HRTEM) imaging
We reported the facile one-pot synthesis and characterization of ultrasmall Gd2O3 nanoparticle colloids in vitro and in vivo
Summary
Magnetic resonance imaging contrast agents (MRI-CAs) allow us to discriminate between normal and abnormal tissues inside the body through the differential contrast enhancement between them.[1,2,3] This occurs owing to the differential population of the MRI-CAs between them. Stable and non-toxic ultrasmall gadolinium oxide nanoparticle colloids (coating material 1⁄4 polyacrylic acid) as high-performance T1 magnetic resonance imaging contrast agents
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