Tomoyoshi Yamano

Tokyo University of Science, Edo, Tōkyō, Japan

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Publications (10)22.94 Total impact

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    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.
    Journal of the American Ceramic Society 01/2013; · 2.11 Impact Factor
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    ABSTRACT: Bioimaging is an important diagnostic tool in the investigation and visualization of biological phenomena in cells and in medicine. In this context, up-converting Gd(2)O(3):Er(3+),Yb(3+) nanostructures (nanoparticles, nanorods) have been synthesized by precipitation methods and hydrothermal synthesis. Independent of size and morphology, Gd(2)O(3):Er(3+),Yb(3+) powders show up-conversion (550nm, 670nm) and near-infrared emission (1.5μm) upon 980nm excitation, which makes these structures interesting for application as biomarkers. With regard to their potential application in bioimaging, cytotoxicity is an important aspect and is strongly affected by the physico-chemical properties of the investigated nanostructures. Therefore, the cytotoxic effect of bare and poly(ethylene glycol)-b-poly(acrylic acid) block co-polymer-modified nanostructures on non-phagocytic and phagocytic cells (B-cell hybridoma cells and macrophages) was investigated. The observed cytotoxic behavior in the case of macrophages incubated with bare nanostructures was assigned to the poor chemical durability of gadolinium oxide, but could be overcome by surface modification.
    Acta biomaterialia 09/2012; · 5.09 Impact Factor
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    ABSTRACT: The use of an "over 1000-nm near-infrared (NIR) in vivo fluorescence bioimaging" system based on lanthanide containing inorganic nanostructures emitting in the visible and NIR range under 980-nm excitation is proposed. It may overcome problems of currently used biomarkers including color fading, phototoxicity and scattering. Gd(2)O(3):Er(3+),Yb(3+) nanoparticles and nanorods showing upconversion and NIR emission are synthesized and their cytotoxic behavior is investigated by incubation with B-cell hybridomas and macrophages. Surface modification with PEG-b-PAAc provides the necessary chemical durability reducing the release of toxic Gd(3+) ions. NIR fluorescence microscopy is used to investigate the suitability of the nanostructures as NIR-NIR biomarkers. The in vitro uptake of bare and modified nanostructures by macrophages is investigated by confocal laser scanning microscopy. In vivo investigations revealed nanostructures in liver, lung, kidneys and spleen a few hours after injection into mice, while most of the nanostructures have been removed from the body after 24 h.
    Journal of Materials Science Materials in Medicine 05/2012; 23(10):2399-412. · 2.14 Impact Factor
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    ABSTRACT: Yttrium hydroxyl carbonate (Y(OH)CO3) precursors were synthesized by the homogeneous co-precipitation method in the presence of polyacrylic acid (PAAc). Resultant precursor particle size is about 15–20 nm with narrow size distribution whereas the particle size is smaller than those acquired by the conventional homogeneous precipitation method. Effective decrease of Y(OH)CO3 particle size was found to be higher for the presence of weak polyanionic ionomer such as PAAc than the presence of strong polyanionic ionomer such as sodium polystyrene sulfonate (PSS). It was observed that the morphology and size of the precursors are almost unchanged after the calcination process. Er3+ doped Y2O3 nanoparticles were synthesized by PAAc assisted homogeneous co-precipitation method showed bright green (550 nm) and red (660 nm) upconversion (UC) as well as near-infrared (NIR) fluorescence (1550 nm) under 980-nm excitation. UC and NIR fluorescence bioimaging and in-vitro cytotoxicity assay of Er3+ doped Y2O3 nanoparticles were successfully attempted with commercially available macrophages and B-cell hybridomas. Cellular uptake of nanoparticles is evidenced from bright field, UC and NIR fluorescence images of macrophages.
    Progress in Crystal Growth and Characterization of Materials 01/2012; 58:121. · 1.60 Impact Factor
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    ABSTRACT: Dendritic cells (DCs) are known to regulate immune responses by inducing both central and peripheral tolerance. DCs play a vital role in negative selection of developing thymocytes by deleting T cells with high-affinity for self-peptide-major histocompatibility complexes. In the periphery, DCs mediate peripheral tolerance by promoting regulatory T-cell development, induction of T-cell unresponsiveness, and deletion of activated T cells. We studied whether allogeneic DCs, obtained from bone marrow cultured with either Flt3L (FLDCs) or granulocyte-macrophage colony-stimulating factor (GMDCs), could induce allospecific central and peripheral tolerance after IV injection; B cells were used as a control. The results showed that only FLDCs reached the thymus after injection and that these cells induced both central and peripheral tolerance to donor major histocompatibility complexes. For central tolerance, injection of FLDCs induced antigen-specific clonal deletion of both CD8 and CD4 single-positive thymocytes. For peripheral tolerance, injection of FLDCs induced donor-specific T-cell unresponsiveness and prolonged survival of donor-derived skin grafts. Tolerance induction by adoptive transfer of FLDCs could be a useful approach for promoting graft acceptance after organ transplantation.
    Blood 01/2011; 117(9):2640-8. · 9.06 Impact Factor
  • Berichte der deutschen chemischen Gesellschaft 05/2010; 2010(18):2673 - 2677. · 2.94 Impact Factor
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    ABSTRACT: Near infrared wavelength region between 0.8 and 2 μm is an attractive region for biomedical imaging due to the low loss in biomedical objects in the region. Rare-earth doped ceramic phosphors are known to emit efficient fluorescence in the same wavelength region. The authors have developed micro fluorescence bioimaging system for cellular or tissue imaging and macro one for in vivo imaging. This paper will review the materials synthesis for the near infrared fluorescence probes as well as the system development and demonstrative works. Er-doped or Yb/Er-doped ceramic phosphors were synthesized with required particle size. The phosphors were partly modified with polyethylene glycol to give dispersion and controlled interaction with the biological objects. By using the micro imaging system, nematodes, mouse tissue and M1 cells were observed by detecting 1.5 μm emission from Er doped in the ceramic phosphor. in vivo imaging with the same fluorescence scheme was also performed for the digestive organs of live mouse.
    Proc SPIE 02/2010;
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    ABSTRACT: Bioimaging is an important tool for investigation and visualization of biological phenomena and as diagnostic tool in medicine. In this context upconverting Gd2O3:Er 3+ ,Yb 3+ nanostructures (nanoparticles, nanorods) have been synthesized and investigated with regard to potential biomedical applications. Besides size and morphology effect on cytotoxic behavior, the influence of PEG-b-PAAc surface modification on biocompatibility was analyzed.
    International Conference on Nanoscience and Nanotechnology (ICONN); 01/2010
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    Terrae Rarae; 01/2009