Water-Soluble MnO Nanocolloid for a Molecular <i>T</i>₁ MR Imaging: A Facile One-Pot Synthesis, In vivo <i>T</i>₁ MR Images, and Account for Relaxivities

다국어 초록 (Multilingual Abstract)

<P>A facile one-pot synthesis of a water-soluble MnO nanocolloid (i.e., <SMALL>d</SMALL>-glucuronic acid-coated MnO nanoparticle) is presented. The MnO nanoparticle in the MnO nanocolloid was coated with a biocompatible and hydrophilic <SMALL>d</SMALL>-glucuronic acid, and its particle diameter was nearly monodisperse and ranged from 2 to 3 nm. The average hydrodynamic diameter of the MnO nanocolloid was estimated to be 5 nm. The MnO nanoparticle was nearly paramagnetic down to <I>T</I> = 3 K. The MnO nanocolloid showed a high longitudinal water proton relaxivity of <I>r</I><SUB>1</SUB> = 7.02 s<SUP>−1</SUP> mM<SUP>−1</SUP> with the <I>r</I><SUB>2</SUB>/<I>r</I><SUB>1</SUB> ratio of 6.83 due to five unpaired <I>S</I>-state electrons of Mn(II) ion (<I>S</I> = 5/2) as well as a high surface to volume ratio of the MnO nanoparticle. High contrast in vivo <I>T</I><SUB>1</SUB> MR images were obtained for various organs, showing the capability of the MnO nanocolloid as a sensitive <I>T</I><SUB>1</SUB> MRI contrast agent. The suggested three key-parameters which control the <I>r</I><SUB>1</SUB> and <I>r</I><SUB>2</SUB> relaxivities of nanocolloids (i.e., the <I>S</I> value of a metal ion, the spin structure, and the surface to volume ratio of a nanoparticle) successfully accounted for the observed <I>r</I><SUB>1</SUB> and <I>r</I><SUB>2</SUB> relaxivities of the MnO nanocolloid.</P><P><B>Graphic Abstract</B>
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