Publications by authors named "Motohiro Kasuya"

14 Publications

  • Page 1 of 1

Facile and rapid detection of SARS-CoV-2 antibody based on a noncompetitive fluorescence polarization immunoassay in human serum samples.

Biosens Bioelectron 2021 Oct 5;190:113414. Epub 2021 Jun 5.

Division of Applied Chemistry, Faculty of Engineering, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo, 060-8628, Japan; Innovative Research Centre for Preventive Medical Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan; Institute of Innovation for Future Society, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan. Electronic address:

Antibody detection methods for viral infections have received broad attention due to the COVID-19 pandemic. In addition, there remains an ever-increasing need to quantitatively evaluate the immune response to develop vaccines and treatments for COVID-19. Here, we report an analytical method for the rapid and quantitative detection of SARS-CoV-2 antibody in human serum by fluorescence polarization immunoassay (FPIA). A recombinant SARS-CoV-2 receptor binding domain (RBD) protein labeled with HiLyte Fluor 647 (F-RBD) was prepared and used for FPIA. When the anti-RBD antibody in human serum binds to F-RBD, the degree of polarization (P) increases by suppressing the rotational diffusion of F-RBD. The measurement procedure required only mixing a reagent containing F-RBD with serum sample and measuring the P value with a portable fluorescence polarization analyzer after 15 min incubation. We evaluated analytical performance of the developed FPIA system using 30 samples: 20 COVID-19 positive sera and 10 negative sera. The receiver operating characteristic curve drawn with the obtained results showed that this FPIA system had high accuracy for discriminating COVID-19 positive or negative serum (AUC = 0.965). The total measurement time was about 20 min, and the serum volume required for measurement was 0.25 μL. Therefore, we successfully developed the FPIA system that enables rapid and easy quantification of SARS-CoV-2 antibody. It is believed that our FPIA system will facilitate rapid on-site identification of infected persons and deepen understanding of the immune response to COVID-19.
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http://dx.doi.org/10.1016/j.bios.2021.113414DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8178067PMC
October 2021

Evaluation of Interfacial pH Using Surface Forces Apparatus Fluorescence Spectroscopy.

Langmuir 2021 Apr 13;37(16):5073-5080. Epub 2021 Apr 13.

Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan.

The fluorescence spectrum measurement of a fluorescence pH probe, C. SNARF-4F, was performed for monitoring the interfacial pH of aqueous electrolytes between mica or silica surfaces while varying the surface separation () using surface force apparatus (SFA) fluorescence spectroscopy. The pH of the aqueous CsCl between mica exponentially decreased with decreasing . The order of the decay lengths of the interfacial pH obtained from the exponential fitting () at various electrolyte concentrations was > ≈ > . For studying the mechanisms of these changes, we performed the electric double layer (EDL) model calculation of the interfacial pH based on the surface potentials, which were evaluated from the EDL forces between the substrates in aqueous electrolytes using the same SFA. The calculated pH value for the 0.1 mM aqueous electrolyte corresponded to the values obtained from fluorescence spectroscopy, indicating that the interfacial pH was attributed to only the general EDL effect. On the other hand, the measured pH value for the higher concentrations of aqueous electrolytes (0.4-10 mM) decreased in the longer ranges than the values calculated from the model, indicating that there was an additional factor affecting the interfacial pH for those concentrations. We also studied the effects of the cationic species of the electrolytes (Cs, Na, and Li) and of the silica substrate on the interfacial pH. The systematic studies of the interfacial pH revealed that it depended on all three factors studied here, that is, the electrolyte concentration, electrolyte species, and the substrates. The results also suggested that the interfacial pH was not only due to the simple EDL theory but could also be affected by an additional factor due to the ion adsorption at the interface and chemical states of the substrates.
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http://dx.doi.org/10.1021/acs.langmuir.1c00817DOI Listing
April 2021

Ice premelting layer of ice-rubber friction studied using resonance shear measurement.

Soft Matter 2020 Sep;16(37):8677-8682

New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai, 980-8577, Japan.

We performed a resonance shear measurement (RSM) based on a low-temperature surface force apparatus to evaluate the frictional properties of the interface between butadiene rubber and ice at various temperatures below 0 °C. Friction between the rubber and ice was high and constant at temperatures below -5 °C, but sharply decreased when the temperature rose above -5 °C. We performed the same measurement by replacing the rubber with polystyrene and silica films which were rigid and exhibited practically minimal elastic deformation in comparison to the rubber. The friction decreased gradually with the increase in temperature from -20 °C to 0 °C at both the polystyrene-ice and the silica-ice interfaces. These results indicated that the elasticity of rubber was responsible for the differences in the rubber-ice interface and the other two samples. To understand the detailed mechanism of friction between the rubber and the ice, we analyzed the obtained RSM data using a physical model. The result indicated that the friction between ice and rubber was determined by the elastic deformation of the rubber film at temperatures below -5 °C, and by the viscosity of the ice premelting layer above -5 °C.
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http://dx.doi.org/10.1039/d0sm00478bDOI Listing
September 2020

Ice Premelting Layer Studied by Resonance Shear Measurement (RSM).

Langmuir 2019 Dec 4;35(48):15729-15733. Epub 2019 Nov 4.

Nihon Michelin Tire Co., Ltd. , 3-7-1 Nishishinjuku, Shinjuku-ku , Tokyo 160-0023 , Japan.

The viscosity of the ice premelting layer in contact with silica in the temperature range of -18 to -1 °C was studied by resonance shear measurement (RSM). The viscosity of the ice premelting layer was determined to be ∼5 orders of magnitude greater than that of the bulk liquid water and continuously decreased with the increasing sliding speed between the two surfaces over the temperature range employed in this study, which was the same behavior as for the typical confined liquids including water. On the other hand, the normal load and the contact pressure did not influence the viscosity, indicating that the premelting layer behaved differently from the typical confined liquids.
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http://dx.doi.org/10.1021/acs.langmuir.9b02451DOI Listing
December 2019

Viscosity measurement of Xanthan-Poly(vinyl alcohol) mixture and its effect on the mechanical properties of the hydrogel for 3D modeling.

Sci Rep 2018 11 8;8(1):16538. Epub 2018 Nov 8.

Institute of Fluid Science, Tohoku University 2-1-1, Katahira, Aoba-ku, Sendai, Miyagi, 980-8577, Japan.

Biomodels made of poly(vinyl alcohol) (PVA) are demanded because they can represent the geometries and mechanical properties of human tissues realistically. Injecting and molding, commonly used in three-dimensional (3D) modeling, help to represent the blood vessels accurately. However, these techniques sometimes require higher pressures than the upper pressure limit of the dispensers for pouring in high viscosity materials; the material viscosity should therefore be lower. Moreover, the mechanical properties of the biomodels should be reproduced. This study proposes a PVA solution through the addition of xanthan gum (XG) for 3D modeling, which lowers liquid viscosity while maintaining the mechanical properties of biomodels. XG is known to facilitate the achievement of non-Newtonian fluidity; however, the effects of XG on a PVA solution and PVA hydrogel (PVA-H) are not confirmed. The viscosity measurement using 15 wt% PVA with XG solution (PVA/XG) shows that it will provide easier pouring than 17 wt% PVA solution. The tensile test using the PVA-H of PVA(15 wt%)/XG(0.2 wt%) reveals that the gel is comparable in Young's modulus to 17 wt% PVA-H. X-ray diffraction shows the crystalline structures of the PVA/XG gel and PVA-H are identical. Thus, this PVA/XG would be useful for fabricating biomodels using injection molding techniques.
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http://dx.doi.org/10.1038/s41598-018-34986-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6224553PMC
November 2018

Low-Temperature Surface Forces Apparatus to Determine the Interactions between Ice and Silica Surfaces.

Langmuir 2018 09 14;34(38):11311-11315. Epub 2018 Sep 14.

Nihon Michelin Tire Co., Ltd. , 3-7-1, Nishishinjuku , Shinjuku-ku, Tokyo 160-0023 , Japan.

We have developed a low-temperature surface forces apparatus (SFA) using a thermoelectric Peltier module inserted below the bottom surface of the lower sample holder, giving easy access to the samples and allowing quick temperature changes. In air, the temperature can be decreased to ca. -20 °C. To demonstrate the performance of the apparatus, we measured the interactions between ice and a silica surface at -11.5 ± 0.5 °C. An exponentially decaying repulsion of the decay length, 11.2 ± 1.0 nm, was observed, and attributed to the electric double layer (EDL) repulsion. The surface potential of the ice was calculated to be -35 mV by fitting the data to the EDL model.
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http://dx.doi.org/10.1021/acs.langmuir.8b01902DOI Listing
September 2018

Selection of Diacrylate Monomers for Sub-15 nm Ultraviolet Nanoimprinting by Resonance Shear Measurement.

Langmuir 2018 08 2;34(32):9366-9375. Epub 2018 Aug 2.

Institute of Multidisciplinary Research for Advanced Materials (IMRAM) , Tohoku University , 2-1-1 Katahira , Aoba-ku, Sendai , Miyagi 980-8577 , Japan.

In UV nanoimprinting, the selection of monomers suitable for sub-15 nm patterning is difficult because the filling behavior of resin at this scale still remains scientifically unclear. We demonstrate sub-15 nm patterning by UV nanoimprinting using silica molds with 20, 15, and 7 nm diameter holes; however, the 7 nm diameter pillar patterns were not fabricated using hydroxy-containing monomers. The filling behavior into silica holes of around 10 nm depended on the chemical structure of the monomers. Resonance shear measurements revealed the following: (1) The viscosities of hydroxy-containing monomers confined between chlorodimethyl(3,3,3-trifluoropropyl)silane (FAS3-Cl)-modified surfaces began to increase at distances shorter than those of the monomers between unmodified surfaces. (2) The monomers confined between tridecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane-modified surfaces were squeezed out when the surface-surface distance decreased at less than 7 nm. The measured viscosities between the FAS3-Cl-modified silica surfaces were correlated with the insufficient filling behavior into the silica holes of around 10 nm in UV nanoimprinting. Contact angle measurements provided an additional insight that a higher wettability of the monomers onto the antisticking chemisorbed monolayers resulted in imprinted patterns with higher aspect ratios. Considering the increase in the monomer viscosity in the nanospace and the wettability of monomers onto chemisorbed monolayers, we concluded that the monomer showing low viscosity under confinement and high wettability onto the mold surface was suitable for single-digit nanometer UV nanoimprinting.
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http://dx.doi.org/10.1021/acs.langmuir.8b01881DOI Listing
August 2018

Nanotribological Characterization of Lubricants between Smooth Iron Surfaces.

Langmuir 2017 04 10;33(16):3941-3948. Epub 2017 Apr 10.

Toyota Motor Co., Toyota, Aichi 471-8572, Japan.

We performed the resonance shear measurement (RSM) for evaluating the nanorheological and tribological properties of model lubricants, hexadecane and poly(α-olefin) (PAO), confined between iron surfaces. The twin-path surface forces apparatus (SFA) was used for determining the distance between the surfaces. The obtained resonance curves for the confined lubricants showed that the viscosity of the confined hexadecane and PAO increased due to liquid structuring when the surface separation (D) decreased to a value less than 24 and 20 nm, respectively. It was also determined that the iron surfaces were lubricated by the hexadecane when normal load (L) was less than 1.1 mN, while the confined hexadecane behaved almost solid-like and showed poor lubricity when L was greater than 1.1 mN. In contrast, PAO between the iron surfaces showed high lubricity even under the high load (L > 2 mN). The surface separation of hexadecane and PAO at a hard wall contact between the iron surfaces was determined to be 4.6 ± 0.5 and 5.0 ± 0.4 nm by applying the fringes of equal chromatic order (FECO) for half-transparent iron films deposited on mica surfaces as substrates. We also characterized hexadecane and PAO confined between mica surfaces for studying the effect of substrates on the confined lubricants.
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http://dx.doi.org/10.1021/acs.langmuir.7b00148DOI Listing
April 2017

Nanometer-Resolved Fluidity of an Oleophilic Monomer between Silica Surfaces Modified with Fluorinated Monolayers for Nanoimprinting.

ACS Appl Mater Interfaces 2017 Feb 8;9(7):6591-6598. Epub 2017 Feb 8.

Institute of Multidisciplinary Research for Advanced Materials and ‡Advanced Institute for Materials Research (WPI-AIMR), Tohoku University , 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan.

Ultraviolet (UV) nanoimprinting has the potential to fabricate sub-15 nm resin patterns, but the interfacial fluidity of organic monomers near monomer liquid/mold solid interfaces related to filling nanoscale mold recesses with UV-curable resins still remains unclear. In this study, we demonstrated that surface forces and resonance shear measurements were helpful to select a surface modifier appropriate for silica mold surfaces for UV nanoimprinting with the low-viscosity monomer 1,10-decanediol diacrylate. Surface forces between silica surfaces mediated with the diacrylate monomer and fluidities of the monomer were investigated with nanometer resolution. Chemical vapor surface modification of silica surfaces with chlorodimethyl(3,3,3-trifluoropropyl)silane (FAS3-Cl) and tridecafluoro-1,1,2,2-tetrahydrooctyltrimethoxysilane (FAS13) gave fluorinated silica surfaces with root-mean-square roughness of less than 0.24 nm suitable for the measurements. When the distance D between two silica surfaces was decreased stepwise in the range of 0-30 nm, monomer viscosity between cleaned silica surfaces increased markedly at D < 6 nm. Surface modification with FAS3-Cl suppressed this increase of interfacial monomer viscosity. In contrast, FAS13-modified silica surfaces caused a jump-in phenomenon at approximately D = 7-9 nm, suddenly decreasing to D = 1 nm as the monomer fluid layer was squeezed out. We concluded that FAS3-Cl was appropriate as a fluorinated surface modifier for silica molds used in UV nanoimprinting with an oleophilic low-viscosity monomer, because the chemisorbed monolayer maintained low monomer viscosity near the surface/monomer interface, in addition to its low surface free energy and short CFCHCH- group.
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http://dx.doi.org/10.1021/acsami.6b15139DOI Listing
February 2017

Characterization of ferrocene-modified electrode using electrochemical surface forces apparatus.

Langmuir 2014 Jun 10;30(24):7093-7. Epub 2014 Jun 10.

Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , Sendai 980-8577, Japan.

A electrochemical surface forces apparatus (EC-SFA) was employed to measure the interactions between gold electrodes modified with self-assembled monolayers of ferrocene alkyl thiol (Fc-SAM) and oxidized ferrocene (ferrocenium cation, Fc(+)-SAM) in a 1 mM aqueous electrolyte. The double-layer repulsion in both cases of the Fc-SAM and Fc(+)-SAM electrodes was observed. The surface charge density (σ) evaluated from the double-layer repulsions between the Fc(+)-SAM electrodes in 1 mM aqueous KClO4 was 0.0027 C/m(2), which was 2.5 times greater than that of the Fc-SAM, at 0.0011 C/m(2). The σ values of the Fc(+)-SAM were evaluated for various counteranions using the same method, which were 0.0048, 0.0040, and 0.0104 C/m(2) for NO3(-), SO4(2-), and CF3SO3(-), respectively. The degrees of dissociation (αd) between the ferrocenium cation and these counteranions were obtained from σ and the density of the ferrocenium on the electrode. The αd value of CF3SO3(-), 4.1%, was the highest, followed in the order, SO4(2-) > NO3(-) > ClO4(-), indicating that most of the positive charges of the ferrocenium cation were compensated by formation of an ion pair with counteranions.
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http://dx.doi.org/10.1021/la5009347DOI Listing
June 2014

Two types of two-component gels formed from pseudoenantiomeric ethynylhelicene oligomers.

Langmuir 2012 Aug 2;28(32):11939-47. Epub 2012 Aug 2.

Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba 6-3, Sendai 980-8578, Japan.

Two-component gels formed from pseudoenantiomeric ethynylhelicene oligomers in toluene exhibited two different properties depending on difference in numbers of helicenes in the two components. The combinations (M)-5/(P)-4, (M)-6/(P)-4, and (M)-7/(P)-4, which contained oligomers with comparable numbers of helicenes, formed transparent gels (Type I gels). The combinations (M)-6/(P)-3, (M)-7/(P)-3, and (M)-8/(P)-3, which contained oligomers with considerably different numbers of helicenes, formed turbid gels (Type II gels). Negative Cotton effects were observed for the Type I gels in the region between 350 and 450 nm, and were positive for the Type II gels, despite the use of (M)-oligomers for the longer components. UV/vis exhibited absorption maxima at 350 nm for the Type I gels and at 338 nm for the Type II gels. Different behaviors in gel formation processes were observed by fluorescence studies. Atomic force microscopy analysis showed fiber structures of 25-50 nm diameter for Type I gels and bundles of 100-150 nm diameter for Type II gels. The stoichiometry in gel formation also differed: The Type I gels showed 1:1 stoichiometry of the two components; the Type II gels showed no 1:1 stoichiometry, likely 1:2 stoichiometry. Using the Type I and II gels, two-layer gel systems were constructed.
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http://dx.doi.org/10.1021/la302759kDOI Listing
August 2012

Resonance shear measurement of nanoconfined ionic liquids.

Phys Chem Chem Phys 2010 Apr 11;12(16):4066-71. Epub 2010 Mar 11.

Department of Chemistry and Biotechnology, Yokohama National University, 79-5 Tokiwadai Hodogaya-ku, Yokohama 240-8501, Japan.

Two types of imidazolium-based ionic liquid (IL), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C(4)mim][NTF(2)]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim][BF(4)]), confined between silica surfaces were investigated by surface force apparatus (SFA)-based resonance shear measurements together with surface force measurements. The surface force profiles in the ILs showed oscillatory solvation forces below the characteristic surface separations: 10.0 nm for [C(4)mim][NTf(2)] and 6.9 nm for [C(4)mim][BF(4)]. The more pronounced solvation force found in [C(4)mim][NTf(2)] suggests that the crystal-forming ability of the IL contributes to the stronger layering of the ILs adjacent to the surface. The resonance shear measurement and the physical model analysis revealed that the viscosities of the confined ILs were 1-3 orders of magnitude higher than that of the bulk IL. This paper also focused on the correlation between the resonance shear behaviour and the lubrication property of the ILs, and the suspension rheology in the ILs. An understanding of the solid-IL interface and of ILs confined in nanospace will facilitate the further development of novel applications employing ILs.
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http://dx.doi.org/10.1039/b923571jDOI Listing
April 2010

Water expansion dynamics after pulsed IR laser heating.

Phys Chem Chem Phys 2008 Sep 8;10(34):5256-63. Epub 2008 Jul 8.

Institute of Materials Research and Engineering A STAR, Agency for Science, Technology and Research, Singapore.

A nanosecond pulsed IR (1.9 microm) laser rapidly heated water, in an open vessel, to temperatures well below the boiling point. The subsequent dynamics of volume expansion were monitored using time-resolved interferometry in order to measure the increase in the water level in the heated area. The water expanded at less than the speed of sound, taking just less than 100 ns to increase its height by approximately 500 nm at surface temperature jumps of 20 K. The initial expansion was followed by an apparent contraction and then a re-expansion. The first expansion phase occurred more slowly than the timescale for bulk H-bond re-structuring of the water, as determined from vibrational bands in the Raman spectra, and represents the limit to the rate at which the overpressure caused by sudden heating can be released. The second phase of the expansion was caused by hydrodynamic effects and is accompanied by morphological changes resulting in light scattering as well as droplet spallation.
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http://dx.doi.org/10.1039/b805838eDOI Listing
September 2008

Density changes accompanying wave propagation in the cerium-catalyzed Belousov-Zhabotinsky reaction.

J Phys Chem A 2005 Feb;109(7):1405-10

Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, 980-8578, Japan.

Refractive index measurement using an interferometric imaging system and observation of chemical wave shapes were carried out during chemical wave propagation of a cerium-catalyzed Belousov-Zhabotinsky (BZ) reaction. Densities increased as chemical waves propagated in samples without NaBr, and decreased in samples with NaBr. Concentration changes of malonic acid, bromomalonic acid, and BrO3- were estimated from Raman spectral measurements in a stirred batch BZ reaction, and these also exhibited differences between samples with and without NaBr. It is proposed that a reaction subset yielding low molecular weight carboxylic acids is predominant in samples with NaBr, whereas a pathway leading to dibromoacetic acid or tribromoacetic acid production is the major process in samples without NaBr.
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http://dx.doi.org/10.1021/jp046001lDOI Listing
February 2005
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