Papers - Asakura, Kouichi

pH-Tolerant giant vesicles composed of cationic lipids with imine linkages and oleic acids

Sawada D., Hirono A., Asakura K., Banno T.

RSC Advances (RSC Advances)  10 ( 56 ) 34247 - 34253 2020.09

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Giant vesicles (GVs) have attracted attention as functional materials because they can encapsulate both hydrophilic and hydrophobic compounds. For next generation functional GVs, both tolerance and stimuli-sensitivity are needed. So far, vesicles tolerant to acidic or basic conditions were generated using a mixture of cationic lipids and fatty acids. Here, to create functional GVs that are tolerant to a wide pH range but sensitively respond at below a specific pH, the behaviour of GVs composed of a cationic lipid with an imine bond and oleic acid was investigated. Even though the GVs prepared by the film swelling method were tolerant to strongly acidic conditions, GVs without oleic acid gradually shrank, accompanied by the generation of oil droplets at the same pH. 1H NMR analysis revealed that during hydration of the film, the imine bond hydrolysed to provide a cationic surfactant and an oil component in the presence of oleic acid due to its own Lewis basicity, suggesting the dissociation of oleic acid. The results of fluorescence spectroscopy using an environment-responsive probe and IR spectroscopy indicated that the GV tolerance originated from the intermolecular interactions of cationic lipids and anionic oleate. This journal is

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Temperature-Dependent Dynamics of Giant Vesicles Composed of Hydrolysable Lipids Having an Amide Linkage

Tameyuki M., Hiranaka H., Toyota T., Asakura K., Banno T.

Langmuir (Langmuir)  35 ( 52 ) 17075 - 17081 2019.12

ISSN  07437463

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Various amphiphiles including surfactants and lipids have been designed and synthesized to improve and create new functionalities. In particular, the emergence of cell-like behaviors of giant vesicles (GVs) composed of synthetic lipids has drawn much attention in the development of chemical models for cells. The aim of this study was to measure temperature-dependent morphological changes of GVs induced by fragmentation and subsequent growth using hydrolysable cationic lipids having an amide linkage. Results from differential scanning calorimetry, fluorescence spectroscopy using an environment-responsive probe, and confocal Raman microscopy showed that the dynamics observed were due to changes in the vesicle membrane, including variation in the lipid composition, induced by thermal stimulation.

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Start of Micrometer-Sized Oil Droplet Motion through Generation of Surfactants

Kasuo Y., Kitahata H., Koyano Y., Takinoue M., Asakura K., Banno T.

Langmuir (Langmuir)  35 ( 41 ) 13351 - 13355 2019.10

ISSN  07437463

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Self-propelled motion of micrometer-sized oil droplets in surfactant solution has drawn much attention as an example of nonlinear life-like dynamics under far-from-equilibrium conditions. The driving force of this motion is thought to be induced by Marangoni convection based on heterogeneity in the interfacial tension at the droplet surface. Here, to clarify the required conditions for the self-propelled motion of oil droplets, we have constructed a chemical system, where oil droplet motion is induced by the production of 1,2,3-triazole-containing surfactants through the Cu-catalyzed azide-alkyne cycloaddition reaction. From the results of the visualization and analysis of flow fields around the droplet, the motion of the droplets could be attributed to the formation of flow fields, which achieved sufficient strength caused by the in situ production of surfactants at the droplet surface.

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Surface structures of cosmetic standard poly methyl methacrylate UV evaluation plates and their influence on the in vitro evaluation of UV protection abilities of cosmetic sunscreens

Kuroda A., Sakai K., Yahagi S., Mukawa T., Sato N., Nakamura N., Maezawa D., Masaki H., Banno T., Asakura K.

Journal of Oleo Science (Journal of Oleo Science)  68 ( 2 ) 175 - 182 2019.02

Research paper (scientific journal), Joint Work, Accepted,  ISSN  13458957

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© 2019 by Japan Oil Chemists’ Society. Cosmetic standard poly methyl methacrylate (PMMA) UV evaluation plates, i.e., roughened PMMA plates, are used in the EU and the US for the in vitro evaluation of UV protection abilities of sunscreen, such as in vitro UVA-PF and critical wavelength for the Broad-spectrum approval. In our previous studies, inhomogeneity in the thickness of a pseudo-sunscreen layer applied on a flat quartz plate was observed to alter UV transmission. Thus, the surface roughness of the standard plates should have a significant influence on the in vitro evaluation. In the present study, we have analyzed the surface structures of three cosmetic standard PMMA UV evaluation plates: Helioplates HD6 (Sa = 6 µm) and ISO plates (Ra = 2 and 5 µm). A decamethylcyclopentasiloxane and 2-propanol-mixed solvent solution of acrylsilicone resin was prepared, and the solution was added dropwise onto the plates. After the evaporation of the solvents, the plates were cut and the cross section was analyzed using SEM-EDS. The distribution of silicon atoms at the cross-section suggested that the maximum depth of penetrating of acrylsilicone resin was larger than Ra for all the standard plates, and the surface structure was significantly different for each standard plate. In addition, cracks into which the acrylsilicone resin deeply penetrated were observed on the surface of some plates. Clear-solution-type pseudo-sunscreen samples in which UV absorbers and acrylsilicone resin were dissolved were deposited on the standard roughened PMMA plates. It was observed that the addition of acrylsilicone resin drastically changed the net UV transmission. The degree to which the hollows of the roughened surface were filled with the pseudo-sunscreen samples determined the variation of UV transmittance.

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Hydrophilicity of the substrate surface under the applied sunscreen layer changes in vitro UV protection efficacies

Kouichi Asakura, Akihiro Kuroda

IFSCC Magazine (IFSCC)  21   53 - 57 2018.08

Research paper (scientific journal), Joint Work, Accepted

Locomotion Mode of Micrometer-Sized Oil Droplets in Solutions of Cationic Surfactants Having Ester or Ether Linkages

Hirono A., Toyota T., Asakura K., Banno T.

Langmuir (Langmuir)  34 ( 26 ) 7821 - 7826 2018.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  07437463

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© 2018 American Chemical Society. Micrometer-sized self-propelled oil droplets under a far-from-equilibrium condition have drawn much attention because of their potential as a dynamic model for the chemical machinery in living organisms. To clarify the effect of interactions between the system components (surfactant, oil, and water) on the locomotion mode of droplets, we investigated the behaviors of oil droplets composed of n-heptyloxybenzaldehyde (HBA) in solutions of cationic surfactants having or not having an ester or an ether linkage. It was observed that in solutions of cationic surfactants having an ester or an ether linkage, spherical HBA droplets self-propelled by changing their direction frequently. On the other hand, when this functional group is absent, a slow self-propelled motion of the oil droplets concurrent with the evolution of aggregates on their surface was observed. From the results of measurement of interfacial tension and assessment of self-emulsification, we determined that the attractive interactions of cationic surfactants without an ester or an ether linkage with HBA are stronger than those having the linkage. The difference in the locomotion mode of oil droplets is probably explained from the viewpoint of the interactions among the system components.

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Effect of freeze–thaw treatment on the precipitation of octyl β-D-Galactoside hemihydrate crystal from the aqueous solution

Ogawa S., Takahashi I., Koga M., Asakura K., Osanai S.

Journal of Oleo Science (Journal of Oleo Science)  67 ( 5 ) 627 - 637 2018

Joint Work, Accepted,  ISSN  13458957

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© 2018 by Japan Oil Chemists’ Society. Cryogenic treatment, like the freeze–thaw process, has been reported to be effective in modifying the physicochemical properties of polymeric hydrogels. However, not much attention has been paid to this process in terms of the precipitation of surfactant–water systems. In this study, two effective cryogenic methodologies were successfully reported to alter the physicochemical properties of a precipitate of an octyl β-D-galactoside (Oct-Gal)–water system. First, hyperrapid cooling (i.e., cooling at 30℃/min) was found to be an effective type of cryogenic treatment: the phase transition temperature (T K ) and enthalpy at the phase transition (ΔH K ) between the crystal-dispersed phase and the sol (micelle) phase significantly decreased. In addition, cryogenic treatment in the presence of electrolytes, such as NaCl, NaBr, and CsCl, was effective even in the absence of the hyperrapid cooling condition. The hyperrapid cooling or the addition of certain electrolytes was considered to prevent the precipitation of the Oct-Gal hemihydrate crystals prior to the complete freezing of ice and the electrolyte/ice eutectic. Hence, the size of the aggregated crystals prepared by the above-mentioned effective cryogenic treatments seemed to be decreased compared with that of the normal precipitated crystals, thereby changing T K and ΔH K . Thus, two basic methodologies for the modification of the physicochemical properties of the crystal-dispersed phase of surfactant–water systems are discussed.

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Coagel prepared from aqueous octyl β-D-galactoside solution

S. Ogawa, M. Koga, K. Asakura, I. Takahashi, S. Osanai

J. Surfact. Det. 20 ( 1 ) 255 - 261 2017

Research paper (scientific journal), Joint Work, Accepted

Phototactic behavior of self-propelled micrometer-sized oil droplets in a surfactant solution

S. Kaneko, K. Asakura, T. Banno

Chem. Commun. 53   2237 - 2240 2017

Research paper (scientific journal), Joint Work, Accepted

Self-propelled oil droplets and their morphological change to giant vesicles induced by a surfactant solution at low pH

T. Banno, Y. Tanaka, K. Asakura, T. Toyota

Langmuir 632 ( 37 ) 9591 - 9597 2016

Research paper (scientific journal), Joint Work, Accepted

Controlled polymerization of acrylonitrile proceeded along with the Belousov-Zhabontinsky oscillator by changing its stirring conditions

Y. Furue, K. Okano, T. Banno, K. Asakura

Chem. Phys. Lett. 645   210 - 214 2016

Research paper (scientific journal), Joint Work, Accepted

Oligosaccharide-based surfactant / citric acid buffer system stabilizes lactate dehydrogenase during freeze-drying and storage without the addition of natural sugar

S. Ogawa, R. Kawai, M. Koga, K. Asakura, I. Takahashi, S. Osanai, S

J. Oleo Sci. 65 ( 6 ) 525 - 532 2016

Research paper (scientific journal), Joint Work, Accepted

Problems on the evaluation of the critical wavelength of sunscreens for “Broad Spectrum” approval brought on by viscous fingering during sunscreen application

M. Wakabayashi, K. Okano, T. Mukawa, D. Maezawa, H. Masaki, A. Kuroda, K. Asakura

Photochem. Photobiol. 92 ( 4 ) 637 - 643 2016

Research paper (scientific journal), Joint Work, Accepted

Deformable self-propelled micro-object comprising underwater oil droplets

T. Banno, A. Asami, N. Ueno, H. Kitahata, Y. Koyano, K. Asakura, T. Toyota

Sci. Rep. 6   31292 2016

Research paper (scientific journal), Joint Work, Accepted

Photoresponsive stripe pattern in achiral azobenzene liquid crystals

Kunihiko Okano, Satoshi Aya, Fumito Araoka, Haruki Obara, Shiori Sato, Takashi Yamashita, Hideo Takezoe, Kouichi Asakura

ChemPhysChem 16 ( 1 ) 95 - 98 2015.01

Research paper (scientific journal), Joint Work, Accepted

Degree of maintenance of lactate dehydrogenase (LDH) activity during freeze/thaw process highly depends on hydrophobic chain length of synthetic mono-tailed glycolipid stabilizer

S. Ogawa, R. Kawai, M. Koga, K. Asakura

Cryobiology and Cryotechnology 61   89 - 94 2015

Research paper (scientific journal), Joint Work, Accepted

Lyotropic behavior of a mono-tailed glycolipid assembly during solidification and melting of electrolyte/ice eutectic systems

Shigesaburo Ogawa, Kouichi Asakura, Shuichi Osanai

Chem. Pharm. Bull. 62 ( 12 ) 1180 - 1184 2014.12

Research paper (scientific journal), Joint Work, Accepted

High-strength gel actuator driven by a photothermal effect

Kunihiko Okano, Aya Nogami, Kouichi Asakura

Polymer J. 46 ( 12 ) 827 - 830 2014.12

Research paper (scientific journal), Joint Work, Accepted

Coexistence effect of UVA absorbers to increase their solubility and stability of supersaturation

Mayu Endo, Tsubasa Mukawa, Nobumasa Sato, Daisuke Maezawa, Yutaka Ohtsu, Akihiro Kuroda, Misaki Wakabayashi, Kouichi Asakura

Int. J. Cosmet. Sci. 36 ( 6 ) 546 - 552 2014.12

Research paper (scientific journal), Joint Work, Accepted

Problems of in vitro SPF measurements brought about by viscous fingering generated during sunscreen applications

Kanae Fujikake, Shizuka Tago, Raphael Plasson, Ryo Nakazawa, Kunihiko Okano, Daisuke Maezawa, Tsubasa Mukawa, Akihiro Kuroda, Kouichi Asakura

Skin Pharmacol. Physiol. 27 ( 5 ) 254 - 262 2014.07

Research paper (scientific journal), Joint Work, Accepted