Synthesis and Characterization of Bifunctional SiO₂@(Y_0.95–xGd_xEu_0.05)₂O₃ Nanocomposites for Magnetic Resonance and Optical Imaging

Abstract

The development of multimodal contrast agents for magnetic resonance (MR) optical imaging has attracted considerable attention due to the combination of both high spatial and temporal resolution of MR imaging with the sensitivity of optical imaging. In this work, a form of dual functional nanocomposites SiO2@(Y0.95–xGdxEu0.05)2O3 (x = 0–0.95) with core–shell structures have been synthesized for magnetic resonance and optical imaging. Based on the results of transmission electron microscopy (TEM), (Y0.95–xGdxEu0.05)2O3 nanoshells of around 8 nm were successfully coated onto amorphous SiO2 nanocores (ca. 115 nm in diameter). The XRD patterns indicate that the shell is crystalline after annealing. Under excitation with UV light (250 nm), the Eu3+ ions in the core–shell nanocomposites of SiO2@(Y0.95–xGdxEu0.05)2O3 mainly exhibit their characteristic red emission (612 nm, 5D0–7F2); increasing the content of Gd increased the luminescent intensity of the nanocomposites significantly. The relationship between T1‐weighted MR imaging and the amount of doped Gd (x) was also investigated. It was found that the highest MR imaging signal intensity was obtained at x = 0.45. In vitro fluorescence imaging indicated that the monodisperse nanoparticles of SiO2@(Y0.95–xGdxEu0.05)2O3 were successfully internalized by RAW 264.7 cells and that they show bright intracellular luminescence. Furthermore, this facile precipitation method may be readily extended to the synthesis of SiO2@(Y0.7Yb0.18Er0.02Gd0.1)2O3 nanocomposites, which present both up‐conversion luminescence and MR contrast properties. The nanocomposites investigated in this study have a certain potential to serve as a versatile material for multimodal imaging probes.

In Vivo Immunotoxicity of SiO2@(Y0.5Gd0.45Eu0.05)2O3 as Dual-Modality Nanoprobes

“…Figure 2b shows that the cytotoxicity of Raw264.7 cells had no significant difference after incubation for 24 and 48 h ( p > 0.05). This complements cytotoxicity data for L929 and lymphocyte cells from our precious study [13]. All cytotoxicity of the nanoprobes was negligible and indicated that the concentration of free Gd 3+ ions was low.…”

“…This suggests that our dual-modality nanoprobes are suitable for T 1 -weighted contrast agents in vitro . Additional characterization has been reported previously [13]. In addition, zeta potential of the dual-modality nanoprobes was (−7.31 ± 1.45) mV (Figure S1).…”

“…In our previous research [13], we have successfully synthesized SiO 2 @(Y 0. 5 Gd 0.45 Eu 0.05 ) 2 O 3 nanocomposites as a potential dual-modality nanoprobe for magnetic resonance (MR) and optical imaging in vitro , but have yet to perform systematic assessments of its immunotoxicity in vivo .…”

Photoluminescence Imaging of SiO2@ Y2O3:Eu(III) and SiO2@ Y2O3:Tb(III) Core-Shell Nanostructures

“…Emission peaks were observed between 570 and 720 nm for the emission spectrum generated at an excitation wavelength of 300 nm and assigned to 10,16,21,31 For the corresponding 2D and 3D photoluminescence images, the dense region corresponds to the emission peaks. The International Commission on Illumination (CIE) xyz color coordinate indicates the redness of the as-prepared sample.…”

“…1,2 Luminescence phosphors have also been applied to biomedical purposes. [3][4][5][6][7][8][9][10] Silica spheres have been employed as phosphor support (or capping) or cell imaging materials due to their good thermal stability and biocompatibility. Zhang et al prepared Eu@SiO 2 core-shell nanoparticles for application to living HeLa cell imaging using time-resolved luminescence.…”