Search

Many of the lanthanide‐based nanoparticles are valuable in magnetic resonance imaging (MRI) because they have excellent magnetic properties that make them suitable for MRI contrast agents, while some of them have additional optical properties and thus can serve as fluorescence imaging (FI) agents as well. Herein, we synthesized d‐glucuronic acid‐coated ultrasmall Ln2O3 (Ln = Tb, Dy, and Ho) nanoparticles with average diameters of ∼ 2 nm. All the nanoparticles showed unsaturated but appreciable magnetization of ∼ 4 emu/g at an applied field of 1.8 T at room temperature, and consequently, high transverse water proton relaxivities (r2) of ∼ 7 s–1 mm–1 at 1.5 T, ∼ 35 s–1 mm–1 at 3.0 T, and ∼ 55 s–1 mm–1 at 9.4 T with negligible longitudinal water proton relaxivities (r1), thus being eligible for use as T2 MRI contrast agents at high MR fields. In addition, d‐glucuronic acid‐coated ultrasmall Tb2O3 nanoparticles exhibited fluorescence in the green region, useful for dual‐modal imaging. [ABSTRACT FROM AUTHOR]

The excellent theranostic properties of gadolinium oxide (Gd2O3) nanoparticles (GNPs) make them very useful as high‐performance positive magnetic resonance imaging (T1 MRI) contrast agents, X‐ray computed tomography (CT) contrast agents, and gadolinium neutron capture therapy (GdNCT) agents in tumor targeting. Among these applications, tumor‐targeting T1 MRI is investigated in this study. To this end, we employ cyclic RGDs (cRGDs; cyclic Arg–Gly–Asp peptides) as tumor‐targeting ligands to coat ultrasmall GNPs (particle diameter = 1.0–2.5 nm). Five types of commercial cRGDs are used in the coating. The cRGD‐coated GNPs (cRGD‐GNPs) are prepared through one‐pot syntheses. They exhibit longitudinal water‐proton relaxivity (r1) values of 10.0–18.7 s–1 m m–1, with r2/r1 ratios of 1.4–1.7 (r2 = transverse water‐proton relaxivity), which are 3–5 times higher than those of commercial Gd chelates. The in vivo tumor targeting of the cRGD‐GNPs is demonstrated by taking T1 MR images in a model mouse with a liver tumor using one of the five cRGD‐GNP sample solutions prepared. Approximately threefold contrast enhancements are observed in the T1 MR images in the tumor region of the liver than in the normal part of the liver, following intravenous administration of the solution. These results demonstrate that cRGD‐GNPs are potential tumor‐targeting T1 MRI contrast agents. [ABSTRACT FROM AUTHOR]

To date, only a few nanosystems have been investigated as T1 MRI-CT dual contrast agents. The T1 MRI-CT dual functionality of a material depends on its longitudinal water-proton relaxivity ( r1) and X-ray absorption strength. We explored Gd(IO3)3 ·2H2O nanomaterial because Gd is the most powerful element for T1 MRI contrast agents, and both Gd and I absorb X-ray radiation; Gd absorbs X-ray radiation ca. 2.5 times more strongly than I. D-Glucuronic acid coated Gd(IO3)3 ·2H2O nanomaterial showed a very large r1 of 52.3 s-1 m M-1 ( r2/ r1 = 1.21), which could be ascribed to hydrated water molecules in the lattice. Its X-ray absorption intensity was also stronger than those of commercial molecular iodine CT contrast agents. This result clearly suggests that D-glucuronic acid coated Gd(IO3)3 ·2H2O nanomaterial is a potential T1 MRI-CT dual contrast agent. [ABSTRACT FROM AUTHOR]