Ultrasmall Europium, Gadolinium, and Dysprosium Oxide Nanoparticles: Polyol Synthesis, Properties, and Biomedical Imaging Applications

Abstract

Imaging agents are crucial in diagnosing diseases. Ultrasmall lanthanide oxide (Ln₂O₃) nanoparticles (NPs) (Ln = Eu, Gd, and Dy) are promising materials as high-performance imaging agents because of their excellent magnetic, optical, and X-ray attenuation properties which can be applied as magnetic resonance imaging (MRI), fluorescence imaging (FI), and X-ray computed tomography (CT) agents, respectively. Ultrasmall Ln₂O₃ NPs (Ln = Eu, Gd, and Dy) are reviewed here. The reviewed topics include polyol synthesis, characterization, properties, and biomedical imaging applications of ultrasmall Ln₂O₃ NPs. Recently published papers were used as bibliographic databases. A polyol method is a simple and efficient one-pot synthesis for preparing ultrasmall Ln₂O₃ NPs. Ligand-coated ultrasmall Ln₂O₃ NPs have good colloidal stability, biocompatibility, and renal excretion ability suitable for in vivo imaging applications. Ultrasmall Eu2O3 NPs display photoluminescence in the red region suitable for use as FI agents. Ultrasmall Gd2O3 NPs have r1 values higher than those of commercial molecular contrast agents and r2/r1 ratios close to 1, which make them eligible for use as T1 MRI contrast agents. Ultrasmall Dy2O3 NPs exhibit high r2 and negligible r1 values, which make them suitable for use as T2 MRI contrast agents. All ultrasmall Ln₂O₃ NPs have high X-ray attenuation powers which make them suitable for use as CT contrast agents. Unmixed, mixed, or doped ultrasmall Ln2O3 NPs with different Ln are extremely useful for in vivo imaging applications in MRI, CT, FI, MRI-CT, MRI-FI, CT-FI, and MRI-CT-FI.

Keywords: CT; FI; Gd; Ln2O3 nanoparticle (Ln = Eu; MRI; Smart polyol synthesis; and Dy); biomedical imaging.