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Er3+ -Doped Y2O3 Nanophosphors for Near-Infrared Fluorescence Bioimaging Applications

Authors

  • Nallusamy Venkatachalam,

    Corresponding author
    1. Center for Technologies against Cancer, Research Institute for Science and Technology, Tokyo University of Science, Noda, Chiba, Japan
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    • The first two authors contributed equally to this work.
  • Tomoyoshi Yamano,

    1. Division of Immunobiology, Research Institute for Biomedical Sciences, Tokyo University of Science, Noda, Chiba, Japan
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    • The first two authors contributed equally to this work.
  • Eva Hemmer,

    1. Center for Technologies against Cancer, Research Institute for Science and Technology, Tokyo University of Science, Noda, Chiba, Japan
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  • Hiroshi Hyodo,

    1. Center for Technologies against Cancer, Research Institute for Science and Technology, Tokyo University of Science, Noda, Chiba, Japan
    2. Department of Materials Science and Technology, Tokyo University of Science, Tokyo, Japan
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  • Hidehiro Kishimoto,

    1. Center for Technologies against Cancer, Research Institute for Science and Technology, Tokyo University of Science, Noda, Chiba, Japan
    2. Division of Immunobiology, Research Institute for Biomedical Sciences, Tokyo University of Science, Noda, Chiba, Japan
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  • Kohei Soga

    1. Center for Technologies against Cancer, Research Institute for Science and Technology, Tokyo University of Science, Noda, Chiba, Japan
    2. Department of Materials Science and Technology, Tokyo University of Science, Tokyo, Japan
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    • Member, The American Ceramic Society.

Abstract

Rare-earth-doped ceramic nanophosphor (RED-CNP) materials are promising near-infrared (NIR) fluorescence bioimaging (FBI) agents that can overcome problems of currently used organic dyes including photobleaching, phototoxicity, and light scattering. Here, we report a NIR–NIR bioimaging system by using NIR emission at 1550 nm under 980 nm excitation which can allow a deeper penetration depth into biological tissues than ultraviolet or visible light excitation. In this study, erbium-doped yttrium oxide nanoparticles (Er3+:Y2O3) with an average particle size of 100 and 500 nm were synthesized by surfactant-assisted homogeneous precipitation method. NIR emission properties of Er3+:Y2O3 were investigated under 980 nm excitation. The surface of Er3+:Y2O3 was electrostatically PEGylated using poly (ethylene glycol)-b-poly(acrylic acid) (PEG-b-PAAc) block copolymer to improve the chemical durability and dispersion stability of Er3+:Y2O3 under physiological conditions. In vitro cytotoxic effects of bare and PEG-b-PAAc-modified Er3+:Y2O3 were investigated by incubation with mouse macrophage cells (J774). Microscopic and macroscopic FBI were demonstrated in vivo by injection of bare or PEG-b-PAAc-modified Er3+:Y2O3 into C57BL/6 mice. The NIR fluorescence images showed that PEG-b-PAAc modification significantly reduced the agglomeration of Er3+:Y2O3 in mice and enhanced the distribution of Er3+:Y2O3.

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