Haruma Kawaguchi

Kanagawa University, Yokohama, Kanagawa, Japan

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Publications (147)488.95 Total impact

  • Haruma Kawaguchi
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    ABSTRACT: Microhydrogels have become a very interesting and important material in hydrogels ­bioapplications. New techniques for the design, synthesis, characterization, function, and application of microhydrogels are providing exciting new possibilities in the micronized ­science. Hydrogels are a soft material with sizes and shapes that are subject to change depending on environmental conditions such as temperature, pH, coexisting materials, and light. Hydrogels that respond to these environmental stimuli and cause swelling changes in aqueous media are known as “stimuli-sensitive hydrogels.”
    12/2009: pages 107-119;
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    ABSTRACT: We discovered a novel method to prepare a protein-based hydrogel, that is, a "Three-Dimensional Nanostructured Protein Hydrogel (3D NPH)", which is composed of protein-polymer hybrid nanoparticles. In this study, we propose a novel protein microarray whose 3D NPH spots were prepared by dispensing a small volume of the solution of protein-polymer mixture on a substrate. The dispensed solution had a short time for cross-linking before its drying-up and the resulting 3D NPH had loosely cross-linked, thin spongy structure. Therefore, the reaction ratio between ligands and analytes was drastically improved in this system compared with the large volume system for Surface Plasmon Resonance (SPR) protein microarray.
    Colloids and surfaces B: Biointerfaces 02/2009; 70(2):259-65. DOI:10.1016/j.colsurfb.2008.12.037 · 4.29 Impact Factor
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    ABSTRACT: We developed novel magnetic nano-carriers around 180 nm in diameter for affinity purification. Prepared magnetic nano-carriers possessed uniform core/shell/shell nano-structure composed of 40 nm magnetite particles/poly(styrene-co-glycidyl methacrylate (GMA))/polyGMA, which was constructed by admicellar polymerization. By utilizing relatively large 40 nm magnetite particles with large magnetization, the magnetic nano-carriers could show good response to permanent magnet. Thanks to uniform polymer shell with high physical/chemical stability, the magnetic nano-carriers could disperse in a wide range of organic solvent without disruption of core/shell structure and could immobilize various kinds of drugs. We examined affinity purification using our prepared magnetic nano-carriers with anti-cancer agent methotrexate (MTX) as ligand. Our magnetic nano-carriers showed higher performance compared to commercially available magnetic beads in terms of purification efficiency of target including extent of non-specific binding protein.
    Colloids and surfaces B: Biointerfaces 08/2008; 64(2):162-9. DOI:10.1016/j.colsurfb.2008.01.013 · 4.29 Impact Factor
  • Macromolecular Rapid Communications 08/2008; 29(15). DOI:10.1002/marc.200890029 · 4.61 Impact Factor
  • Macromolecular Rapid Communications 08/2008; 29(15):1287 - 1292. DOI:10.1002/marc.200800090 · 4.61 Impact Factor
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    ABSTRACT: Protein chips are important tools for high-throughput analysis of biological events. We have developed a novel method to prepare a protein-based hydrogel, that is, a “Three-Dimensional Nano-structured Protein Hydrogel” (3-D NPH), which is composed of protein and polymer nano-particles. The 3-D NPH could be easily prepared by dispensing a protein and polymer mixture on a substrate. Surprisingly, gold particles conjugated with protein A diffused into the 3-D NPH which was made of mouse IgG through the pores. We have shown that the protein chips made with our 3-D NPH method has tremendously improved sensitivity in detecting protein-protein interactions compared with that of direct protein immobilization methods.
    Macromolecular Symposia 06/2008; 266(1):81-84. DOI:10.1002/masy.200850615
  • Sakiko Tsuji, Haruma Kawaguchi
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    ABSTRACT: Poly(N-isopropylacrylamide) (PNIPAM)-carrying particles were characterized as thermosensitive Pickering emulsifiers. Emulsions were prepared from various oils, such as heptane, hexadecane, trichloroethylene, and toluene, with PNIPAM-carrying particles. PNIPAM-carrying particles preferentially formed oil-in-water (O/W)-type emulsions with a variety of oils. All the emulsions stabilized by PNIPAM-carrying particles were stable for more than 3 months as long as they were stored at room temperature. However, when the emulsions were heated from room temperature to 40 degrees C, at which point the PNIPAM layer caused a coil-to-globule transition, phase separation occurred. Thus, by using thermosensitive PNIPAM-carrying particles as emulsifiers, the stability of the Pickering emulsions could be controlled by a slight change in temperature.
    Langmuir 05/2008; 24(7):3300-5. DOI:10.1021/la701780g · 4.38 Impact Factor
  • Macromolecular Rapid Communications 04/2008; 29(7):547 - 551. DOI:10.1002/marc.200700797 · 4.61 Impact Factor
  • Anan Jeenanong, Haruma Kawaguchi
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    ABSTRACT: The effect of pH and temperature on the behavior of stimuli-sensitive microgels on surface plasmon resonance (SPR) sensor chip was studied using poly(N-isopropylacrylamide-co-acrylic acid) microgels. The microgels were prepared by aqueous free-radical precipitation copolymerization. The dispersions of microgels in different buffer solutions were run over the SPR chip which was covered with a self-assembled monolayer (SAM) having amine functional groups at the top surface. Due to a loss of electrostatic repulsive force between microgels in citrate buffer, the size of microgels was the smallest and the number of microgels bound on the chip was the largest. As a result, the highest response was observed in citrate buffer. The temperature also affected the attachment of microgels. Both NaCl aqueous and citrate buffer solutions gave a higher response with increasing temperature. To clarify these phenomena, the effect of swelling degree on SPR response was studied by using the same chip. The results showed that the difference in SPR response in each solution was due to changing volume and refractive index of swollen gel. The simulated SPR response based on the mean square electric field (MSEF) was consistent with experimental response.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 02/2008; 315(1):232-240. DOI:10.1016/j.colsurfa.2007.08.003 · 2.35 Impact Factor
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    Daisuke Suzuki, Sakiko Tsuji, Haruma Kawaguchi
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    ABSTRACT: We present Janus microgels modified using a Pickering emulsion-based approach and demonstrate their self-assembly. Stimuli-responsive microgels composed of cross-linked poly[N-isopropylacrylamide-co-(acrylic acid)] (pNA) were synthesized by means of aqueous free-radical precipitation polymerization. Using pNA microgels as stabilizers, a Pickering emulsion was formed by simple stirring with pNA dispersion and hexadecane. The amino groups were then introduced by means of a carbodiimide coupling reaction using ethylenediamine and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. These microgels were collected by emulsion collapse. Hemispherical distribution of the amino groups in the modified microgels was confirmed using the Au nanoparticle labeling technique. Interestingly, these microgels were aggregated in string structures at pH 4, whereas they were not at pH 6. Such microgel string structures self-assembled from well-structured microgels by simple stimuli-change have potential use as micro-actuators.
    Journal of the American Chemical Society 08/2007; 129(26):8088-9. DOI:10.1021/ja072258w · 11.44 Impact Factor
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    Henmei Ni, Haruma Kawaguchi, Takeshi Endo
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    ABSTRACT: Amphoteric microgels consisting of poly(AAm/MAc/DMAEMA/MB) were prepared by semicontinuous polymerization in ethanol. Scanning electron microscopy (SEM) and dynamic light scattering (DLS) were employed for evaluating the microspheres and their pH−volume transitions in the aqueous solution, respectively. Monodispersed amphoteric microgels with a U-type of pH−volume transition, i.e., volume contracted in the pH range 6.5−7.5 and expanded beyond this, were prepared by adding MAc dropwise at a certain rate (20 g/80 min, standard recipes). It was observed that increasing [NaCl] or [CaCl2] served to decrease the hydrodynamic diameter of amphoteric microgels, irrespective of pH. Moreover, in the region of pH 2−3, the pH of amphoteric microgels increased with the increase of ion strength, whereas inversely, for pH 9−10, the pH decreased with an increase of ion strength, regardless of the types of salts. The U-type curve of diameter vs pH could be replaced along with the pH axis by adjusting the charged amount of DMAEMA. Control-releasing behavior of amphoteric microgels was also investigated. It was observed that the dye was released to the same extent when the pH was changed from 6.8 to either acidic or basic conditions.
    Macromolecules 07/2007; 40(17). DOI:10.1021/ma070358g · 5.93 Impact Factor
  • Anan Jeenanong, Haruma Kawaguchi
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    ABSTRACT: Behavior of stimuli-sensitive microgels on SPR (surface plasmon resonance) sensor chip was studied using poly(N-isopropylacrylamide-co-acrylic acid) microgels. The microgels were prepared by aqueous free-radical precipitation copolymerization. They were monodisperse spheres with a diameter less than 200 nm. The dispersions of microgels in different buffer solutions were run over the SPR chip which was covered with a self-assembled monolayer (SAM) having amine functional groups at the top surface. The number of microgels bound to the chip was inversely proportional to the hydrodynamic size of microgel. SPR response of microgels bound to the chip was found to be controlled by two factors: the microgel-inducing change in evanescent wave amplitude and the number of microgels. The former is a function of depth-depending evanescent field strength, refractive index, and volume of swollen microgel. The simulated SPR response based on this function was consistent with experimental response.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 07/2007; 302(1-3-302):403-410. DOI:10.1016/j.colsurfa.2007.03.008 · 2.35 Impact Factor
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    Yasujiro Mori, Haruma Kawaguchi
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    ABSTRACT: Sub-micron sized polystyrene particles containing magnetite more than 30 wt.% were prepared by miniemulsion polymerization with commercially available ferricolloid. The effects of some water-soluble initiators and/or oil-soluble initiators on the particles characteristics, such as the size, morphology, magnetic properties and colloidal stability, were studied. The size of monomer droplets/polymer particles increased from 60 to 300 nm during polymerization, keeping magnetic in core when potassium persulfate (KPS) or ammonium persulfate (APS) was used as the sole initiator. These particles were easily separated from the medium within short time scale in external magnetic field, while such characteristics were controlled by the amount of persulfate used for the polymerization. In contrast, when 2,2'-azobis isobutyronitrile (AIBN) was used as the initiator, the size of droplets/particles was retained to be 90 nm at the most and magnetite nanoparticles located at the surface of polystyrene particles, which were so colloidally stable that they were not separated in external magnetic field. The above-mentioned effect of initiators on particle size in persulfate system was likely originated from the decrease of pH value and the increase of ionic strength, which induced the fusion of droplets/particles containing magnetite. Mixed-initiators system resulted in intermediate characteristics, compared with each initiator system. The location of magnetite in the particle seems to depend on where initiation/polymerization occurred in each initiator system.
    Colloids and surfaces B: Biointerfaces 05/2007; 56(1-2):246-54. DOI:10.1016/j.colsurfb.2006.11.023 · 4.29 Impact Factor
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    Henmei Ni, Haruma Kawaguchi, Takeshi Endo
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    ABSTRACT: The forming process and characteristics of monodispersed hydrogel microspheres of poly(acrylamide–methacrylic acid) with sharp pH–volume transition were studied. pH-/ion-sensitive and thermosensitive behaviors of microspheres sampled at various stage of polymerization were evaluated by using the dynamic light scattering. It was observed that the sharpness of pH–volume transition increased with the increase in monomer conversion. Both thermo- and ion-sensitive behaviors were affected by pH. At pH4.3, the hydrodynamic diameter of microspheres monotonically and slightly decreased with the increase in temperature, whereas at pH3.5 and 3.8, the curves of thermo–volume transition were similar to those of pH–volume transition with a maximum temperature at 25 and 20°C, respectively. Increasing the [CaCl2] was to decrease the hydrodynamic diameters of microspheres, irrespective of pH. However, a region at lower [NaCl] was found, where the diameter increased with the increase in [NaCl]. Moreover, the range of diameter increasing extended to higher [NaCl] as pH increased.
    Colloid and Polymer Science 04/2007; 285(8):873-879. DOI:10.1007/s00396-006-1633-1 · 2.41 Impact Factor
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    Henmei Ni, Haruma Kawaguchi, Takeshi Endo
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    ABSTRACT: Monodisperse hydrogel microsphere of polyacrylamide (AAm)-methacrylic acid (MAc) cross-linked by N,N′-methylene-bis(acrylamide) (MB) with sharp pH–volume transition was prepared in ethanol. The dynamic light scattering (DLS) was employed to evaluate the pH sensitivity of these microspheres. The effects of main factors: composition of copolymer, cross-linked degree, and initial total concentration or solid content of comonomers were investigated. Osmotic pressure and deformation of cross-linked polymer network were considered as the two dominant factors influencing the characteristics of pH–volume transition. High content of MAc and cross-linked degree increased the osmotic pressure, thereby moving the onset of pH–volume transition to higher pH. Association/dissociation of poly-MAc segments in the domains contributed to the free energy of hydrogel–solvent mixing. As soon as pH was high enough to overcome the osmotic pressure, the dissociated poly-MAc segments simultaneously decreased the osmotic pressure and free energy of hydrogel–solvent mixing, thereby allowing the sharp and large volume transition. As a result, microspheres were prepared with pH–volume transition of almost 12 times to their original volume within a narrow range of pH variation, ca. 0.5.
    Colloid and Polymer Science 03/2007; 285(7):819-826. DOI:10.1007/s00396-006-1631-3 · 2.41 Impact Factor
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    ABSTRACT: We present the assembly of colloidal crystals composed of various thermoresponsive core/shell microgels and their hybrid microgel counterparts that contain localized Au nanoparticles. To obtain nanostructured microgels, we conducted a three-stage polymerization. First, core microgels composed of cross-linked poly(N-isopropylacrylamide) (pNIPAm) were synthesized by precipitation polymerization. Using these microgels as cores or “seeds”, a copolymer shell of pNIPAm was added to these core particles using a functional comonomer. Finally, a second shell consisting solely of cross-linked pNIPAm was added onto the preformed core/shell microgels by using this seeded polymerization technique. With use of these core/shell/shell microgels as templates, Au nanoparticles were synthesized in situ, using the cationic sites in the inner shell to nucleate particle growth. To control the optical properties of the Au nanoparticles, electroless Au plating was carried out with use of the preformed Au nanoparticles in the microgel as seeds. These hybrid microgels retained their thermoresponsive properties and possessed a high degree of size uniformity as confirmed by dynamic light scattering and were assembled into three-dimensional colloidal crystals by using thermal annealing processes. The resulting colloidal crystals were characterized by optical microscopy and reflectance spectroscopy. This synthetic design for producing distinctive, functional building blocks could be expanded to enable the creation of complex tunable optical materials containing refractive index periodicity on multiple length scales.
    The Journal of Physical Chemistry C 03/2007; 111(15). DOI:10.1021/jp068535n · 4.84 Impact Factor
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    ABSTRACT: Magnetic nano-particles composed of superparamagnetic iron oxide in the core and hydrophilic polymer in the shell were prepared for the use of MRI contrast agents. Ferric and ferrous ions were added to an aqueous solution of block copolymer, poly(ethylene oxide)-block-poly(glycelol methacrylate-co-acrylic acid), which was prepared by living radical polymerization using iniferter. After iron ions-polymer complex formation, the pH of the solution was raised to 11 to get magnetite nanoparticles which were encapsulated with polymer. Use of the polymer having the molecular weight of ca. 10,000 and the 100 × AAc/GLM of 1–10 and incubation of the mixture of iron ions and water-soluble polymers at a moderate temperature resulted in the formation of favorable composite particles of 10–20 nm in diameter. The saturation magnetization and other instrumental analysis of composite particles suggested that the iron oxide formed in the above-mentioned procedure was magnetite.
    Macromolecular Symposia 12/2006; 245-246(1):363 - 370. DOI:10.1002/masy.200651350
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    ABSTRACT: Thermo-sensitive colloidal crystals are prepared simply by mixing colloidal silica spheres and large thermo-sensitive gel spheres. The thermo-reversible change in the lattice spacing of colloidal crystals of monodisperse silica spheres (CS82, 103nm in diameter) depends on the size of the admixed temperature-sensitive gel spheres. For spheres with sizes less and greater than that of the silica spheres, the lattice spacing upon temperature increase above the lower critical solution temperature of poly(N-isopropyl acrylamide) decreases (cf. Okubo et al. Langmuir 18:6783, 2002) and increases, respectively. A mechanism, which is able to explain these experimental findings, is proposed. Moreover, crystal growth rates and the rigidities of the thermo-sensitive colloidal crystals are studied.
    Colloid and Polymer Science 11/2006; 285(3):351-358. DOI:10.1007/s00396-006-1578-4 · 2.41 Impact Factor
  • Daisuke Suzuki, Haruma Kawaguchi
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    ABSTRACT: We report in this study the presence of Janus particles, which are candidates for use with electronic color papers. We used negatively charged polystyrene particles (370nm) as the core particles, and gold was then sputtered onto their packed monolayer under several conditions. The sputtered particles were next redispersed into the aqueous medium by gentle sonication. Gold nanoparticles localized on one side of the cores could also serve as seeds for subsequent shell growth by electroless gold plating. Through these treatments, a series of well-dispersed Janus particles were obtained with gold nanostructures of different size and shape only on one side. Their dispersions showed different colors originating from the surface plasmon resonance absorption of gold nanoparticles localized on the hemisphere. The particles obtained by this approach have potential applications such as in sensors and electronic color paper.
    Colloid and Polymer Science 08/2006; 284(12):1471-1476. DOI:10.1007/s00396-006-1524-5 · 2.41 Impact Factor
  • Daisuke Suzuki, Haruma Kawaguchi
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    ABSTRACT: We synthesize and characterize stimuli-sensitive core/shell particles with functional group (or material) localized in the core. We previously reported two types of hybrid particles prepared by using the template particles which were synthesized by soap-free emulsion copolymerization with N-isopropylacrylamide and glycidyl methacrylate (GMA) as monomers but by different preparation methods. GMA has advantages in immobilizing materials having several functional groups such as thiol ones. In this study, to obtain the suitable template particles for immobilizing any inorganic nanoparticles in the core, we investigated the effect of feed ratio of the two monomers. Obtained template particles were modified by thiol compounds to introduce ionic groups. They were characterized by dynamic light scattering and scanning electron microscopy. After in situ synthesis of magnetic nanoparticles in the templates, the hybrid particles were characterized directly by transmission electron microscopy. Consequently, we could obtain the hybrid core/shell particles which contained a large amount of magnetic nanoparticles (∼33wt%) in the core.
    Colloid and Polymer Science 08/2006; 284(12):1443-1451. DOI:10.1007/s00396-006-1523-6 · 2.41 Impact Factor

Publication Stats

4k Citations
488.95 Total Impact Points


  • 2009
    • Kanagawa University
      • Department of Chemistry
      Yokohama, Kanagawa, Japan
  • 1981–2009
    • Keio University
      • • Graduate School of Science and Technology
      • • Department of Applied Chemistry
      • • Faculty of Science and Technology
      Edo, Tōkyō, Japan
  • 2000–2002
    • Tokyo Institute of Technology
      • Department of Biological Information
      Tokyo, Tokyo-to, Japan
  • 1994
    • Nagoya Institute of Technology
      • Department of Materials Science and Engineering
      Nagoya, Aichi, Japan