Er:Y2O3 and Nd:Y2O3 Nanoparticles: Synthesis, Pegylation, Characterization and Study of Their Luminescence Properties

Abstract

Lanthanide-doped yttrium oxide nanoparticles can display selective upconversion properties, rendering them invaluable in the field of nanomedicine for both sensing and diagnostics. Different syntheses of Er:Y2O3 and Nd:Y2O3 nanoparticles (NPs) were studied and optimized to obtain small particles of regular shape and good crystallinity. The morphological and compositional characterizations of the nanoparticles were obtained with different techniques and showed that both Er:Y2O3 and Nd:Y2O3 NPs were well dispersed, with dimensions of the order of a few tens of nanometers. The photoluminescence and cathodoluminescence measurements showed that both Er:Y2O3 and Nd:Y2O3 NPs had good emission as well as upconversion. The nanophosphors were functionalized by a pegylation procedure to suppress unwanted reactions of the NPs with other biological components, making the NP systems biocompatible and the NPs soluble in water and well dispersed. The pegylated core/shell nanoparticles showed the same morphological and optical characteristics as the core, promoting their strategic role as photoactive material for theragnostics and biosensing.

Internalization of Pegylated Er:Y2O3 Nanoparticles inside HCT-116 Cancer Cells: Implications for Imaging and Drug Delivery

“…47 To evaluate the percentage of Er present in the NPs, ICP-MS measurements were carried out. The Er/Er + Y value found (0.09) was slightly higher than the expected one (Er/Er + Y = 0.07) and essentially the same to that previously obtained, 38 that is the best to obtain a high fluorescence signal. 48,49 Before being used for internalization studies with cells, the optical properties of the particles were probed in order to verify that the luminescence characteristics were maintained even after the pegylation process.…”

“…The pegylation of Er:Y 2 O 3 nanoparticles was carried out by slightly modifying the procedure reported by Kamimura et al Briefly, to 20 mL of a buffer solution TRIS/HCl (pH 7.00), containing 0.5 g/L of PEG- b -PAAC, 2 mg of nanoparticles were added, and the resulting mixture was kept at 4 °C for 24 h under magnetic stirring. The obtained solution was purified by ultracentrifugation (9.0 × 10 4 g, 15 min, 3 times), and the solvent was changed to Milli-Q water …”

“…The obtained solution was purified by ultracentrifugation (9.0 × 10 4 g, 15 min, 3 times), and the solvent was changed to Milli-Q water. 38 2.4. TEM Analyses.…”

“…The typical peaks of erbium are present in the visible region at approximately 550 and 660 nm, and in the infrared region at 980 and 1522 nm, clearly indicating that, after the PEGylation, the nanoparticles core still maintained itsluminescence properties with satisfactory intensities; in particular, the same transitions of the naked nanoparticles were observed. 38 This behavior is due to the fact that the crystalline characteristics of the material are not significantly altered. 50,51 The PL spectrum of the nanoparticles in solution obtained by a confocal microscope is reported in Figure 2c.…”

“…Indeed, particles that are too large may not be able to overcome the lipid bilayer and enter the cytoplasm. In the particular case of rare earths-doped Y 2 O 3 nanoparticles, however, it was noted that too small particles give lower luminescence signals. , Recently, some of us have developed a synthetic procedure by which it is possible to obtain NPs with a fairly high yield and suitable dimensions to simultaneously optimize the fluorescence intensity and the ability to penetrate inside the cells.…”