Noritada Kaji

Chalmers University of Technology, Goeteborg, Västra Götaland, Sweden

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Publications (110)453.6 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We report aqueous phase synthesized semiconductor nanoparticles with well-defined numbers of constituent atoms. Aqueous phase synthesis provides many advantages over organic phase synthesis for producing such high-quality semiconductor nanoparticles. We synthesized CdSe nanoparticles with excellent colloidal and optical stabilities directly in aqueous solution at room temperature and then identified them as selectively grown (CdSe)33 and (CdSe)34 magic-sized clusters. These clusters displayed extremely sharp excitonic absorption and emission peaks because of their practically monodispersed size distribution. Their X-ray diffraction pattern and Raman spectral features were considerably different from the corresponding pattern and features for typical crystalline CdSe nanoparticles. Growth of our magic-sized clusters was very slow and proceeded via the formation of different sizes of progressively larger CdSe nanoparticle intermediates with time. Our results demonstrated that aqueous phase synthetic routes could be successfully adopted for producing high-quality semiconductor nanoparticles.
    The Journal of Physical Chemistry C. 10/2010; 114(44).
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    ABSTRACT: We present a new rapid and easy-to-use immunoassay chip which we have named the immuno-pillar chip. It has hydrogel pillars, fabricated inside a microchannel, with many antibody molecules immobilized onto 1 µm diameter polystyrene beads. To evaluate the chip performance, we applied it to the sandwich assay of C-reactive protein (CRP), α-fetoprotein (AFP) and prostate-specific antigen (PSA), a cardiac and inflammation marker, tumors and prostate cancer markers, respectively. For detection of disease markers, we confirmed the chip provides rapid analysis (total assay time of about 4 min) with high sensitivity, it is easy-to-use (no special skills are needed), and it uses small volumes of the sample and reagent (0.25 µL each). Moreover, multiplex assay for three biomarkers was also possible. Additionally, the immuno-pillar chip has a big advantage of having hardly any influence on the assay results even if the introduction quantities of the sample or reagents are different.
    Lab on a Chip 10/2010; 10(24):3335-40. · 5.70 Impact Factor
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    ABSTRACT: The various potential factors affecting the performance of nanopillar chips on DNA separation were investigated from the viewpoints of both numerical calculations and actual experiments. To yield higher performance and replace the conventional DNA separation techniques such as microchip electrophoresis, the phenomenon specific to the nanopillar chips should be deeply understood. In this paper, although various factors affecting the performance of the nanopillar chips are considered, we focused on the effect of electroosmotic flow, which is particularly noticeable in quartz-made nanopillar chips. High-resolution separation of DNA was realized when an electroosmotic flow was suppressed by simply using a higher concentration of buffer, but DNA separation failed in the presence of an electroosmotic flow. It was confirmed from the numerical simulations and the direct observations that the deformation of DNA band during the injection process was induced by electroosmotic flow and consequently led to a poor resolution.
    Israel Journal of Chemistry. 03/2010; 47(2):161 - 169.
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    ABSTRACT: DNA separation technologies combined with micro- and nanofabrication technologies found a breakthrough in genotyping and DNA sequencing. This tutorial review outlines the fabrication technologies for nano-scaled structures inside microchannels and how the precisely designed structures contribute to obtaining higher performances in DNA separations from the viewpoint of the fabrication process, "top-down" nanofabrication and "bottom-up" molecular self-assembly approaches. It was found that these nanofabricated structures generated the unique separation modes that could not be achieved by random-sized pores of conventional gel or polymer systems. Furthermore, it was found that nanoscale-specific phenomena such as electroosmotic flow should be taken into consideration for further development of nanofabricated structures in DNA analysis. These separation technologies will contribute as a core technology for a future integrated biomolecule anlaysis chip.
    Chemical Society Reviews 03/2010; 39(3):948-56. · 24.89 Impact Factor
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    ABSTRACT: Quantum dots (QDs) have been used to study the effects of fluorescent probes for biomolecules and cell imaging. Adipose tissue-derived stem cells, which carry a relatively lower donor site morbidity, while yielding a large number of stem cells at harvest, were transduced with QDs using the octa-arginine peptide (R8) cell-penetrating peptide (CPP). The concentration ratio of QDs:R8 of 1 x 10(4) was optimal for delivery into ASCs. No cytotoxicity was observed in ASCs transduced with less than 16 nM of QDs655. In addition, >80% of the cells could be labeled within 1 h and the fluorescent intensity was maintained at least for 2 weeks. The ASCs transduced with QDs using R8 could be differentiated into both adipogenic and osteogenic cells, thus suggesting that the cells maintained their stem cell potency. The ASCs labeled with QDs using R8 were further transplanted subcutaneously into the backs of mice or into mice through the tail vein. The labeled ASCs could be imaged with good contrast using the Maestro in vivo imaging system. These data suggested that QD labeling using R8 could be utilized for the imaging of ASCs.
    Biomaterials 02/2010; 31(14):4094-103. · 7.60 Impact Factor
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    ABSTRACT: Development of an Easy and High-Throughput Cell Assay System with a Culture Chip and an Assay Chip
    IEEJ Transactions on Sensors and Micromachines 01/2010; 130:471-475.
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    ABSTRACT: We present an application of a novel DNA separation matrix, cholesterol-bearing pullulan (CHP) nanogels, for microchip electrophoresis. The solution of the CHP showed a unique phase transition around 30 mg∕ml and formed gel phase over this critical concentration. This gel phase consists of the weak hydrophobic interactions between the cholesterols could be easily deformed by external forces, and thus, loading process of the CHP nanogels into microchannels became easier. The high concentration of the CHP nanogels provided excellent resolutions especially for small DNA fragments from 100 to 1500 bp. The separation mechanism was discussed based on Ogston and Reptation models which had developed in gels or polymer solutions. The result of a single molecule imaging gave us an insight of the separation mechanism and the nanogel structures as well.
    Biomicrofluidics 01/2010; 4(3):32210. · 3.39 Impact Factor
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    ABSTRACT: To determine if gene expression profiling of whole blood cells is a useful source of markers for the early diagnosis of the onset of type 2 diabetes, we examined gene expression profiling of whole blood cells and type 2 diabetes-related organs, such as liver, adipose tissue, and skeletal muscle, of Otsuka Long-Evans Tokushima Fatty (OLETF) rats. At the age of 6 weeks, RNA was isolated from tissues of fasted OLETF and control Long-Evans Tokushima Otsuka (LETO) rats. Gene expression was analyzed using the Agilent rat oligo microarray. Gene ontology analysis showed that gene expression of biologically meaningful groups of genes in liver, adipose tissue, and skeletal muscle, which are involved in the pathogenesis of type 2 diabetes, differed between OLETF and LETO rats. Three hundred genes of whole blood cells were differentially expressed. Four out of these 300 genes were related to the insulin-signaling pathway and 57 out of 300 genes were up- or down-regulated in at least one tissues in OLETF rats. These results support our hypothesis that gene expression profiling of whole blood cells might be a useful source of markers to predict the onset of type 2 diabetes.
    Biological & Pharmaceutical Bulletin 01/2010; 33(6):1033-42. · 1.85 Impact Factor
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    ABSTRACT: Using cysteine and its derivatives as capping molecules, we investigated the influence of the physical structure and chemical nature of capping molecules on the selective growth and stabilization of small CdSe nanoparticles (NPs) in aqueous solution at room temperature. Our investigations revealed specific roles for each functional group of cysteine, and we could correlate this structure and nature of the capping molecules with the size, size restriction, size distribution, and stability of the NPs. For selective growth and stabilization of the NPs in aqueous solution, their capping molecules should have at least one functional group with strong nucleophilicity as well as another free, charged functional group. Capping molecules acting as a monodentate ligand were more effective than those acting as a bidentate ligand for restricting the NPs to a smaller size, whereas the former was less effective than the latter for getting a narrower NP size distribution. Capping molecules with relatively bulky spatial geometry near the ligand-NP interface resulted in the formation of NPs with poor short- and long-term stabilities, whereas those having relatively compact spatial geometry near the interface led to NPs with at least moderate short-term stability. We saw that capping molecules having relatively compact outermost spatial geometry led to NPs with excellent long-term stability, whereas those having relatively bulky outermost spatial geometry produced NPs with at most only moderate long-term stability. Our results clearly showed general trends for the possibility of selective growth of stable semiconductor NPs with particular sizes in aqueous solution.
    ACS Nano 12/2009; 4(1):121-8. · 12.06 Impact Factor
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    ABSTRACT: Spontaneous adsorption from solution onto solid surface is a common phenomenon in nature, but the force that governs adsorption is still a matter of considerable debate. (1, 2) We found that surfactants and cellulose adsorb from solution onto a poly(methyl methacrylate) (PMMA) surface in an ordered and cooperative way governed by hydrogen bonding. The glucose rings of n-dodecyl-beta-D-maltoside (DDM) and hydroxyethylcellulose (HEC) stand perpendicular to the surface, H-bond to the surface COOMe groups with their C=O and Me-O bonds parallel to the surface, and form a tight monolayer. The non-H-bonded COOMe groups orient their C=O bonds perpendicular to the surface. In contrast, the glucose rings of hydrophobically modified hydroxyethylcellulose (HMHEC) lie flat with the side chains perpendicular to the surface and H-bond to the perpendicular-oriented C=O groups. The non-H-bonded COOMe groups orient their C=O bonds parallel but Me-O bonds near-perpendicular to the surface for stabilizing HMHEC. The current work provides a detailed picture of how surface-active molecules interact with a solid surface and self-assemble into greatly different architectures.
    Langmuir 06/2009; 25(16):9296-301. · 4.19 Impact Factor
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    ABSTRACT: In about a 3 min period, we have simultaneously separated plasma from human whole blood and metered and diluted the plasma using a microchip with an interchannel microstructure. The plasma separation was based on both cross-flow filtration and sedimentation of red blood cells in the microchannels. Metering and diluting operations of the plasma were based on volume control of liquid in the microchannels by syringe pumps. On this microchip, we produced plasma diluted by a factor of 6 from whole blood containing theophylline and we observed very little hemolysis. It is possible to separate plasma from one or just several drops of whole blood by using this microchip.
    Analytical Chemistry 05/2009; 81(8):3194-8. · 5.70 Impact Factor
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    ABSTRACT: We have realized fluorescence polarization immunoassay (FPIA) on a microchip in about 1 minute. FPIA is a homogeneous competitive immunoassay which is based on measuring fluorescence polarization after competitive binding of an analyte and a tracer to an antibody. We constructed a microfluidic FPIA system composed of a newly designed microchip, a laser, a CCD camera and an optical microscope with two specially installed polarizers-one fixed and one rotatable. Theophylline, a typical small drug molecule, was used as a model analyte. Theophylline and fluorescence-labeled theophylline were introduced through different inlets and combined in a 100 microm-wide microchannel where anti-theophylline antibody was added. To optimize the microchip design for FPIA, we investigated the diffusion time of theophylline and the mixing time of theophylline and antibody in this channel, which were 6 s and 36 s, respectively. We successfully carried out a quantitative analysis of theophylline in serum near the therapeutic range in 65 s. In FPIA, a larger tracer-antibody complex emits more polarized fluorescence than the tracer, and therefore, by increasing the antigen concentration in a sample, more polarization relaxation is observed since the tracer-antibody complex concentration is decreased and the tracer concentration is increased. Tracer binding to an antibody is directly measured by spectroscopic techniques without any separation process.This microchip-based FPIA is very simple and rapid, unlike microchip-based heterogeneous immunoassay, because it does not require several processes such as washing and reflowing and immobilizing of antibodies or antigens in the channel. In the future, microchip-based FPIA should find frequent use for point-of-care testing in the clinical field, where conventional FPIA has been used for laboratory tests.
    Lab on a Chip 05/2009; 9(7):966-71. · 5.70 Impact Factor
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    ABSTRACT: Separation techniques, such as chromatography and electrophoresis, form the basis in many fields and are continually developed for better separation efficiency. The efforts normally involve a new mechanism together with sufficient separation length. We develop a velocity gap theory to make things simple. The theory is based on the discovery that the velocity gap (VG) effect could enlarge the distance between two moving objects. Mathematical deduction certified that the resolution may be magnified infinitely without changing the separation mechanism or the separation length. DNA separation confirmed its practical feasibility by achieving 2-5 times higher resolution on a microchip. Our results indicate that VG effect could enlarge the distance between two moving objects and may potentially be utilized to ameliorate separation efficiency.
    Analytical Chemistry 05/2009; 81(7):2745-50. · 5.70 Impact Factor
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    ABSTRACT: We have realized a cloned enzyme donor immunoassay (CEDIA) on a microchip in 96 s. CEDIA is a homogeneous immunoassay, based on the bacterial enzyme beta-galactosidase, which was genetically engineered into two inactive fragments: an enzyme donor and an enzyme acceptor. A model analyte was theophylline, and the detectable concentration range was from 0 to 40 microg mL(-1). Our CEDIA using a microfluidic device was very simple and rapid, unlike microchip-based heterogeneous immunoassays and CEDIA on a well-type microchip.
    Analytical Sciences 03/2009; 25(2):149-51. · 1.57 Impact Factor
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    ABSTRACT: We investigated properties of cells affecting their optical trapping force and successfully established a novel cell separation method based on the combined use of optical trapping force and microfluidics on a microchip. Our investigations reveal that the morphology, size, light absorption, and refractive index of cells are important factors affecting their optical trapping force. A sheath flow of sample solutions created in a microchip made sample cells flow in a narrow linear stream and an optical trap created by a highly focused laser beam captured only target cells and altered their trajectory, resulting in high-efficiency cell separation. An optimum balance between optical trapping force and sample flow rate was essential to achieve high cell separation efficiency. Our investigations clearly indicate that the on-chip optical trapping method allows high-efficiency cell separation without cumbersome and time-consuming cell pretreatments. In addition, our on-chip optical trapping method requires small amounts of sample and may permit high-throughput cell separation and integration of other functions on microchips.
    Analytical and Bioanalytical Chemistry 03/2009; 394(1):277-83. · 3.66 Impact Factor
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    ABSTRACT: In this research, a simple on-line microchip gel electrophoresis with ITP was applied for the concentration and separation of BSA and its immunoassay complex with mAb in a single cross form PMMA microchip. We investigated the ITP concentration effect in PMMA MCE using combination of leading electrolytes, terminating electrolytes and other factors. We realized an ITP-based concentration and separation of BSA and its immunoassay complexes in standard cross-channel microchip gel electrophoresis, which exceeded 2000-fold concentration of BSA immunocomplex using Tris-H3PO4 as a leading electrolyte and Tris-gamma-amino butyric acid as a terminating electrolyte. In addition, we also realized concentration of BSA sample in water, which was more than 20 000-fold and was the result of the concentration effect from combining ITP and the sample stacking techniques.
    Electrophoresis 01/2009; 30(18):3250-3256. · 3.26 Impact Factor
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    ABSTRACT: Adipose tissue-derived stem cells (ASCs) have a self-renewing ability and can be induced to differentiate into various types of mesenchymal tissue. Because of their potential for clinical application, it has become desirable to label the cells for tracing transplanted cells and for in vivo imaging. Quantum dots (QDs) are novel inorganic probes that consist of CdSe/ZnS-core/shell semiconductor nanocrystals and have recently been explored as fluorescent probes for stem cell labeling. In this study, negatively charged QDs655 were applied for ASCs labeling, with the cationic liposome, Lipofectamine. The cytotoxicity of QDs655-Lipofectamine was assessed for ASCs. Although some cytotoxicity was observed in ASCs transfected with more than 2.0 nM of QDs655, none was observed with less than 0.8 nM. To evaluate the time dependency, the fluorescent intensity with QDs655 was observed until 24 h after transfection. The fluorescent intensity gradually increased until 2 h at the concentrations of 0.2 and 0.4 nM, while the intensity increased until 4 h at 0.8 nM. The ASCs were differentiated into both adipogenic and osteogenic cells with red fluorescence after transfection with QDs655, thus suggesting that the cells retain their potential for differentiation even after transfected with QDs655. These data suggest that QDs could be utilized for the labeling of ASCs.
    Cell Transplantation 01/2009; 18(5):591-9. · 4.42 Impact Factor
  • Biophysical Journal - BIOPHYS J. 01/2009; 96(3).
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    ABSTRACT: A thermo-responsive separation matrix, consisting of Pluronic F127 tri-block copolymers of poly(ethylene oxide) and poly(propylene oxide), was used to separate DNA fragments by microchip electrophoresis. At low temperature, the polymer matrix was low in viscosity and allowed rapid loading into a microchannel under low pressure. With increasing temperatures above 25 degrees C, the Pluronic F127 solution forms a liquid crystalline phase consisting of spherical micelles with diameters of 17-19 nm. The solution can be used to separate DNA fragments from 100 bp to 1500 bp on poly(methyl methacrylate) (PMMA) chips. This temperature-sensitive and viscosity-tunable polymer provided excellent resolution over a wide range of DNA sizes. Separation is based on a different mechanism compared with conventional matrices such as methylcellulose. To illustrate the separation mechanism of DNA in a Pluronic F127 solution, DNA molecular imaging was performed by fluorescence microscopy with F127 polymer as the separation matrix in microchip electrophoresis.
    Analytical and Bioanalytical Chemistry 07/2008; 391(7):2543-9. · 3.66 Impact Factor
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    ABSTRACT: We demonstrated a highly sensitive double-fluorescent dye staining in microchip electrophoresis (ME) for analysis of milk proteins. The detection sensitivity of ME was very limited so far and needed improvement. Our staining method consisted of two steps. First, in sample preparation before electrophoresis, protein was covalently bound to an amine-reactive fluorescent dye, Cy5. Then, the Cy5-attached protein was denatured with SDS and was further stained, during electrophoresis, with Agilent fluorescent dye, which was noncovalently attached to hydrophobic regions of the SDS-protein complexes. This double-fluorescent staining enhanced fluorescent intensity and lowered the detection limit to 200 pg of protein. This provided higher sensitivity than silver- or SYPRO Ruby-staining methods, which have previously given the highest sensitivity in protein staining. In addition, we applied our staining method to analysis of milk proteins and achieved their successful detection, whereas it was difficult to analyze them by the unimproved method.
    Electrophoresis 07/2008; 29(12):2533-8. · 3.26 Impact Factor

Publication Stats

858 Citations
453.60 Total Impact Points

Institutions

  • 2013
    • Chalmers University of Technology
      Goeteborg, Västra Götaland, Sweden
  • 2007–2013
    • Hokkaido University
      • • Laboratory for Molecular Design of Pharmaceutics
      • • Faculty of Pharmaceutical Sciences
      • • Graduate School of Pharmaceutical Sciences
      Sapporo-shi, Hokkaido, Japan
  • 2006–2012
    • Nagoya University
      • Graduate School of Engineering
      Nagoya-shi, Aichi-ken, Japan
  • 2000–2011
    • The University of Tokushima
      • • Graduate School of Pharmaceutical Sciences
      • • Institute for Genome Research
      • • Department of Molecular and Pharmaceutical Biotechnology
      • • Department of Medicinal Biochemistry
      • • Faculty of Pharmaceutical Sciences
      Tokusima, Tokushima, Japan
  • 2009
    • Tohoku University
      • Center for Interdisciplinary Research
      Sendai-shi, Miyagi-ken, Japan
  • 2006–2009
    • National Institute of Advanced Industrial Science and Technology
      • Health Research Institute
      Takamatsu-shi, Kagawa-ken, Japan
  • 2001–2004
    • Japan Science and Technology Agency (JST)
      Edo, Tōkyō, Japan