Paramagnetic ultrasmall Ho₂O₃ and Tm₂O₃ nanoparticles: characterization of r₂ values and in vivo T₂ MR images at a 3.0 T MR field

Abstract

Paramagnetic ultrasmall Ho2O3 and Tm2O3 nanoparticles (davg = ~2.1 nm) grafted with various hydrophilic and biocompatible ligands such as poly(ethylene glycol) diacid (Mn = 250 and 600 amu) and polyacrylic...

Magnetic Nanoparticle-Based High-Performance Positive and Negative Magnetic Resonance Imaging Contrast Agents

“…The NPs exhibited mean particle diameters of 2.05 and 1.90 nm and appreciable r 2 values of 13.1 and 9.9 s −1 mM −1 for the PEI1200 and PEI60000-coated NPs, respectively. The same authors synthesized Ho 2 O 3 NPs grafted with PEG diacid (PEGD)250 (Mw = 250 amu), PEGD600 (Mw = 600 amu), and PAA1800 (Mw = 1800 amu) using the one-pot polyol method (mean particle diameter = 2.1, 2.1, and 1.7 nm, respectively) [ 98 ]. The r 2 value decreased with increasing ligand-size such that 30.39 s −1 mM −1 (PEGD250) < 11.33 s −1 mM −1 (PEGD600) < 1.44 s −1 mM −1 (PAA1800).…”

“… ( a ) ( i ) TEM image of PAA-coated Ho 2 O 3 NPs (labeled with dotted circles) and ( ii ) in vivo T 2 MR images of mouse liver (labeled as “L”) and kidneys (labeled as “K”), before (labeled as “Pre”) and 15 or 16 min after intravenous injection of PAA-coated Ho 2 O 3 NPs into mice tails at 3.0 and 9.4 T [ 96 ]. ( b ) ( i ) TEM image (labeled with dotted circles) and ( ii ) in vivo T 2 MR images of mouse liver and kidneys at 3 T, before (labeled as “pre”) and 4 h after intravenous injection of PEGD250-coated Ho 2 O 3 NPs [ 98 ]. …”

“…Mn-based NPs can be used as T 1 and T 2 dual-modal contrast agents because of their suitable r 2 /r 1 ratios. However, Ln-based NPs (Ln = Dy, Ho, and Tb) can only be used as T 2 MRI contrast agents because they have negligible r 1 values [ 96 , 97 , 98 , 99 , 100 ].…”