Synthesis and Characterization of Bifunctional SiO2@(Y0.95-xGdxEu0.05)2O3 Nanocomposites for Magnetic Resonance and Optical Imaging

• Published in: European journal of inorganic chemistry 2012-12, Vol.2012 (34), p.5677-5684
• Main Authors: Liu, Huan, Li, Li, Tian, Xiu-Mei, Hu, Wen-Yong, Kuang, Xiao-Yan, Shao, Yuan-Zhi
• Format: Article
• Language: English
• Subjects: Imaging agents; Magnetic resonance imaging; Nanostructures; Optical imaging; Rare earths
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201200875

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. We report a facile method for the preparation of bifunctional SiO2@(Y0.95–xGdxEu0.05)2O3 nanocomposites for magnetic resonance (MR) and optical imaging. Increasing the content of Gd led to a significant enhancement of the emission intensity and presented a maximum MR intensity at x = 0.45. After internalization in RAW 264.7 cells, the nanoparticles showed bright intracellular luminescence.