論文 - 堀田　篤

Thermophysical property measurements on tetrabutylphosphonium sulfate ionic semiclathrate hydrate consisting of the bivalent anion

Arai Y., Koyama R., Endo F., Hotta A., Ohmura R.

Journal of Chemical Thermodynamics （Journal of Chemical Thermodynamics）  131   330 - 335 2019年04月

ISSN  00219614

　概要を見る

© 2018 Elsevier Ltd To develop the “hydrate thermal energy storage technology” it is desired to reveal the mechanism of the thermophysical property manifestation on ionic semiclathrate hydrate. The influence of valence on thermophysical properties has not been investigated so far. In the present study, the phase equilibrium temperatures and the dissociation heats of tetrabutylphosphonium sulfate ((TBP)2SO4) ionic semiclathrate hydrate were experimentally studied. (TBP)2SO4 hydrate consists of the bivalent anion, SO42−. The highest phase equilibrium temperature was 6.5 °C at the mass fraction range from 0.363 to 0.384. The largest dissociation heat was (168.8 ± 2.4) kJ·kg−1 at the mass fraction 0.374. These values of the phase equilibrium temperature and the dissociation heat were respectively lower and smaller than those of the ionic semiclathrate hydrates with the monovalent anion. As a new choice for thermal energy storage medium, (TBP)2SO4 hydrate would be suitable to the automotive air conditioner and the cold chain for blood or perishable foods.

• Access to Document (DOI)

Micropatterning of a 2-methacryloyloxyethyl phosphorylcholine polymer surface by hydrogenated amorphous carbon thin films for endothelialization and antithrombogenicity

Bito K., Hasebe T., Maegawa S., Kitagawa T., Matsumoto T., Suzuki T., Hotta A.

Acta Biomaterialia （Acta Biomaterialia）  87   187 - 196 2019年03月

ISSN  17427061

　概要を見る

© 2019 Acta Materialia Inc. The existing first-generation drug-eluting stent (DES) has caused late and very late stent thrombosis related to incomplete stent endothelialization. Hence, biomaterials that possess sufficient anti-thrombogenicity and endothelialization with the controlled drug release system have been highly required. In this work, we have developed a newly designed drug-release platform composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer, a non-thrombogenic polymer, and micropatterned hydrogenated amorphous carbon (a-C:H), a cell-compatible thin film. The platelet adhesion and the endothelial cell adhesion behavior on the micropatterned substrates were investigated in vitro. The results indicated that the micropatterned a-C:H/MPC polymer substrates effectively supported the human umbilical vein endothelial cell (HUVEC) proliferation, while suppressing the platelet adhesion. Interestingly, the HUVEC exhibited different shape and behavior by changing the island size of the micropatterned a-C:H. By introducing both a non-thrombogenic polymer and cell-compatible thin films through a simple patterning method, we demonstrated that the platform had the potential to be utilized as a base material for DES with cell controllability. Statement of significance: The current first-generation drug-eluting stents (DES) would cause late and very late stent thrombosis due to the incomplete endothelialization of the metal stent material. In this work, we have developed a new DES platform composed of a 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer micropatterned by hydrogenated amorphous carbon (a-C:H). Two types of differently micropatterned a-C:H stent surface were made. Our studies revealed that the micropatterned a-C:H/MPC polymer substrates could effectively enhance the endothelial cell (EC) proliferation, simultaneously suppressing the platelet adhesion, becoming a highly biocompatible material especially for indwelling devices including a drug-release device. The new drug-release platform could be utilized as a base material for cell-controllable coating on DES.

• Access to Document (DOI)

Thermo-responsive nanocomposite hydrogels based on PEG-b-PLGA diblock copolymer and laponite

Maeda T., Kitagawa M., Hotta A., Koizumi S.

Polymers （Polymers）  11 （ 2 ）  2019年02月

　概要を見る

© 2019 by the authors. Poly(ethylene glycol)-b-poly(D,L-lactide-co-glycolide) (PEG-b-PLGA) diblock copolymers are widely known as polymeric surfactants for biomedical applications, and exhibit high solubility in water compared to PLGA-b-PEG-b-PLGA triblock copolymers known as gelation agents. In order to overcome the difficulties in the preparation of thermo-responsive hydrogels based on PLGA-b-PEG-b-PLGA due to the low solubility in water, the fabrication of thermo-responsive hydrogels based on PEG-b-PLGA with high solubility in water was attempted by adding laponite to the PEG-b-PLGA solution. In detail, PEG-b-PLGA with high solubility in water (i.e., high PEG/PLGA ratio) were synthesized. Then, the nanocomposite solution based on PEG-b-PLGA and laponite (laponite/PEG-b-PLGA nanocomposite) was fabricated by mixing the PEG-b-PLGA solutions and the laponite suspensions. By using the test tube inversion method and dynamic mechanical analysis (DMA), it was found that thermo-responsive hydrogels could be obtained by using PEG-b-PLGA, generally known as polymeric surfactants, and that the gelation temperature was around the physiological temperature and could be regulated by changing the solution composition. Furthermore, from the structural analysis by small angle neutron scattering (SANS), PEG-b-PLGA was confirmed to be on the surface of the laponite platelets, and the thermosensitive PEG-b-PLGA on the laponite surface could trigger the thermo-responsive connection of the preformed laponite network.

• Access to Document (DOI)

Radiopaque and biodegradable beads fabricated with Lipiodol and polycaprolactone for transarterial chemoembolization

Okamoto Y., Bito K., Hasebe T., Matsumoto T., Hotta A.

MRS Advances （MRS Advances）  4 （ 20 ） 1187 - 1192 2019年

　概要を見る

Copyright © Materials Research Society 2019. Embolic beads for transarterial chemoembolization (TACE) should possess radiopacity and biodegradability at the same time, to be visualized in a body under fluoroscopy and CT scanning to avoid complicating disease. In this study, we fabricated radiopaque and biodegradable beads composed of Lipiodol (LPD) (ethiodized oil) and polycaprolactone (PCL), a biocompatible and biodegradable polymer. LPD/PCL beads were first fabricated with a home-made microfluidic device. By changing the flow-rate ratio in the microfluidic device, the mean diameter of LPD/PCL beads could be well controlled. The radiopacity was evaluated by the fluoroscopic imaging and the CT number measurements. Furthermore, the biodegradability was evaluated by collecting the weight loss data of LPD/PCL immersed in lipase/PBS solution and PBS. The results showed that LPD/PCL beads obtained in this study had sufficient radiopacity and biodegradability, which would be an alternative embolic agent for TACE.

• Access to Document (DOI)

Enhancement of the mechanical property of poly(ϵ-caprolactone) composites with surface-modified cellulose nanofibers fabricated via electrospinning

Ichimura H., Kurokawa N., Hotta A.

MRS Advances （MRS Advances）  4 （ 7 ） 385 - 391 2019年

　概要を見る

Copyright © Materials Research Society 2019. Poly(ϵ-caprolactone) (PCL) is one of the leading biocompatible and biodegradable polymers. However, the mechanical property of PCL is relatively poor as compared with that of polyolefins, which has limited the active applications of PCL as an industrial material. In this study, to enhance the mechanical property of PCL, cellulose nanofibers (C-NF) with high mechanical property, were employed as reinforcement materials for PCL. The C-NF were fabricated via the electrospinning of cellulose acetate (CA) followed by the subsequent saponification of the CA nanofibers. For the enhancement of the mechanical property of the PCL composite, the compatibility of C-NF and PCL was investigated: the surface modification of the C-NF was introduced by the ring-opening polymerization of the ϵ-caprolactone on the C-NF surface (C-NF-g-PCL). The polymerization was confirmed by the Fourier transform infrared (FTIR) spectroscopy. Tensile testing was performed to examine the mechanical properties of the C-NF/PCL and the C-NF-g-PCL/PCL. At the fiber concentration of 10 wt%, the Young's modulus of PCL compounded with neat C-NF increased by 85% as compared with that of pure PCL, while, compounded with C-NF-g-PCL, the increase was 114%. The fracture surface of the composites was analyzed by scanning electron microscopy (SEM). From the SEM images, it was confirmed that the interfacial compatibility between PCL and C-NF was improved by the surface modification. The results demonstrated that the effective surface modification of C-NF contributed to the enhancement of the mechanical property of PCL.

• Access to Document (DOI)

Annealing and saponification of electrospun cellulose-acetate nanofibers used as reinforcement materials for composites

Inukai S., Kurokawa N., Hotta A.

Composites Part A: Applied Science and Manufacturing （Composites Part A: Applied Science and Manufacturing）  113   158 - 165 2018年10月

ISSN  1359835X

　概要を見る

© 2018 Elsevier Ltd To enhance the mechanical properties of regenerated cellulose nanofibers (RC-NF), the annealing and the saponification of electrospun cellulose-acetate nanofibers (CA-NF) have been investigated. It was found that, by increasing the annealing time of CA-NF at 50 °C from 0 to 12 h, the crystallinity of RC-NF increased from 37% to 41%, which became constant after 12 h. By applying the theory proposed by Tsai, the Young's modulus of RC-NF was found to increase from 9.0 to 28.0 GPa by increasing the annealing time from 0 to 12 h, which also became constant after 12 h. The optimized annealing time for the maximum crystallinity and Young's modulus became shorter by increasing the annealing temperature, indicating that the crystallinity and the Young's modulus of RC-NF were strongly correlated. Eventually, the Young's modulus of RC-NF/PVA increased from 2.1 to 3.0 GPa at the maximum, while that of pure PVA was 1.5 GPa.

• Access to Document (DOI)

Thermomechanical properties of highly transparent self-reinforced polylactide composites with electrospun stereocomplex polylactide nanofibers

Kurokawa N., Hotta A.

Polymer （Polymer）  153   214 - 222 2018年09月

ISSN  00323861

　概要を見る

© 2018 Elsevier Ltd Stereocomplex polylactide (sc-PLA) nanofibers with the average diameter of 367 nm were prepared by the conductivity-controlled electrospinning using 7 wt% PLA solution in the mixed solvents of dichloromethane and pyridine. The sc-PLA nanofibers were used as reinforcement materials for poly(L-lactide) (PLLA) to fabricate a self-reinforced PLA composite, while the fibers were compounded into the PLLA by compression molding. Thermomechanical and optical properties of the resulting self-reinforced PLA composites were investigated. It was found that highly transparent (above 75%) self-reinforced PLA composites were obtained up to the sc-PLA fiber concentration of 15 wt%. Also, at higher temperature in the rubbery state, the storage moduli of the composites increased by adding sc-PLA nanofibers. At the fiber concentration of 15 wt%, the storage modulus of the composite became 70 MPa, which was 24.1 times higher than that of the original pure PLLA. It was therefore concluded that the self-reinforced PLA composite with high transparency and high thermomechanical properties was successfully obtained.

• Access to Document (DOI)

Uniformly dispersed polymeric nanofiber composites by electrospinning: Poly(vinyl alcohol) nanofibers/polydimethylsiloxane composites

Watanabe K., Maeda T., Hotta A.

Composites Science and Technology （Composites Science and Technology）  165   18 - 23 2018年09月

ISSN  02663538

　概要を見る

© 2018 Elsevier Ltd A method for the fabrication of homogeneous and well-dispersed polymeric nanofiber composites was investigated. Nanofiber fillers can be used to produce polymeric nanocomposites by mixing the fillers to base polymers, eventually enhancing the mechanical property of the matrix polymers. To produce such composites, nanofibers were usually sandwiched by molten matrix polymers at high temperature before molding. The traditional so-called sandwich method, however, was found to produce rather biased and inhomogeneous composites due largely to the solid entanglement of the nanofibers. In this work, unwoven polymer nanofibers were synthesized through electrospinning by controlling the electrostatic repulsion of the nanofibers. We modified the electrospinning apparatus for the direct synthesis of homogenous composites: nanofibers were electrospun and directly ejected from the electrospinning syringe to the matrix polymer solution (not in a solid state), where a regular metal electrode plate was replaced by an optimized metal container containing the base polymer solution. It was found that this new fabrication method could realize homogeneous mixing of the nanofibers that were eventually uniformly dispersed in the polymer solution. Poly(vinyl alcohol) (PVA) was used for nanofibers and polydimethylsiloxane (PDMS) was used for polymer matrix. The field emission scanning electron microscopy (FE-SEM) revealed the homogeneous and well-dispersed PVA nanofibers in the resulting PDMS composites. The composites also presented higher mechanical properties as compared with the composites fabricated by the traditional sandwich method.

• Access to Document (DOI)

Mechanically Tough Syndiotactic Polypropylene (sPP) Gels Realized by Fast Quenching Using Liquid Nitrogen

F. Endo, R. Okoshi, K. Takaesu, N. Kurokawa, H. Iwase, T. Maeda, A. Hotta

Macromolecules （ACS Publications）  51   2321 - 2327 2018年02月

研究論文（学術雑誌）, 共著, 査読有り

• Access to Document (DOI)

Impact of hot wire and material gas species on the Cat-CVD coating of gas barrier SiOC thin films onto PET bottles

M. Nakaya, S. Yasuhara, T. Maeda, A. Hotta

Surface and Coatings Technology （Elsevier）  344   21 - 29 2018年02月

研究論文（学術雑誌）, 共著, 査読有り

• Access to Document (DOI)

Thermophysical property measurements of tetrabutylphosphonium acetate (TBPAce) ionic semiclathrate hydrate as thermal energy storage medium for general air conditioning systems

Y. Arai, Y. Yamauchi, H. Tokutomi, F. Endo, A. Hotta, S. Alavi, R, Ohmura

International Journal of Refrigeration （Elsevier）  88   102 - 107 2018年01月

研究論文（学術雑誌）, 共著, 査読有り

• Access to Document (DOI)

Nanocomposite injectable gels capable of self-replenishing regenerative extracellular microenvironments for in vivo tissue engineering

K. Nagahama, N. Oyama, K. Ono, A. Hotta, K. Kawauchi, T. Nishikata

Biomaterials Science （Royal Society of Chemistry）  6   550 - 561 2018年01月

研究論文（学術雑誌）, 共著, 査読有り

• Access to Document (DOI)

Self-assembly of peptide amphiphiles by vapor pressure osmometry and dissipative particle dynamics

Seki T., Arai N., Suh D., Ozawa T., Shimada T., Yasuoka K., Hotta A.

RSC Advances （RSC Advances）  8 （ 47 ） 26461 - 26468 2018年

　概要を見る

© The Royal Society of Chemistry. Peptide amphiphiles are one of the most promising materials in the biomedical field, so much effort has been devoted to characterizing the mechanism of their self-assembly and thermosensitive gelation. In this work, vapor pressure osmometry measurements were carried out to parameterize the thermosensitivity of interactions between peptide amphiphiles in an aqueous solution. The osmometry measurement verified that the peptides became more hydrophobic as temperature increased, which was quantitatively described with the Flory-Huggins χ parameter. Thereafter, a coarse-grained molecular model was used to simulate peptide amphiphiles dissolved in an aqueous solution. The temperature sensitive coarse-grained parameter aHW, which is the repulsive force between the hydrophilic head of the peptide amphiphile and water was estimated from the aforementioned experimentally obtained χ. Furthermore, the effects of concentration and temperature on the self-assembly behavior of peptide amphiphiles were quantitatively studied by dissipative particle dynamics. The simulation results revealed that aHW plays an important role in self-assembly characteristics and in the resulting microstructure of the peptide amphiphiles, which coincides with previous experimental and computational findings. The methodology in quantitatively linking the coarse-grained parameter from experiment and theory provides a sensible foundation for bridging future simulation studies with experimental work on macromolecules.

• Access to Document (DOI)

PEG-based nanocomposite hydrogel: Thermo-responsive sol-gel transition and degradation behavior controlled by the LA/GA ratio of PLGA-PEG-PLGA

M. Kitagawa, T. Maeda, A. Hotta

Polymer Degradation and Stability （Elsevier）  147   222 - 228 2017年12月

研究論文（学術雑誌）, 共著, 査読有り

• Access to Document (DOI)

Thermal effects on the strain-induced β to α form crystalline structural transition observed in solid-state syndiotactic polystyrene

F. Endo, A. Hotta

Polymer （Elsevier）  135 （ 17 ） 103 - 110 2017年12月

研究論文（学術雑誌）, 共著, 査読有り

• Access to Document (DOI)

Gas and flavor barrier thin film coating to plastic closures

M. Nakaya, K. Motomura, T. Maeda, A. Hotta

Quarterly Physics Review （KEI Journals）  4 （ 1 ） 1590 2017年12月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  2572-701X

Thermodynamic Properties of Ionic Semiclathlate Hydrate Formed with Tetrabutylammonium Propionate

Y. Yamauchi, T. Yamasaki, F. Endo, A. Hotta, R. Ohmura

Chemical Engineering & Technology （Wiley）  40 （ 10 ） 1810 - 1816 2017年08月

研究論文（学術雑誌）, 共著, 査読有り

• Access to Document (DOI)

In vitro basic fibroblast growth factor (bFGF) delivery using micro-patterning of hydrogenated amorphous carbon (a-C:H) film and anti-thrombogenic 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer for stent coating

K. Bito, T. Hasebe, T. Maeda, S. Maegawa, T. Matsumoto, T. Suzuki, A. Hotta

Journal of Biomedical Materials Research Part A （Wiley）  105 （ 12 ） 3384 - 3391 2017年08月

研究論文（学術雑誌）, 共著, 査読有り

• Access to Document (DOI)

Biocompatibility Tests and Adhesion Improvements for Hydrogen-Free Amorphous Carbon for Blood-Contacting Medical Devices

Y. Yamato, T. Hasebe, S. Maegawa, K. Bito, T. Matsumoto, T. Mine, T. Hayashi, A. Hotta, T. Suzuki

Sensors and Materials （MYU K.K.）  29 （ 6 ） 843 - 854 2017年06月

研究論文（学術雑誌）, 共著, 査読有り

• Access to Document (DOI)

Composition-dependent sol-gel transition of amphiphilic blend of PEG with hydrophobic gallamide components

A. Aso, K. Taki, T. Maeda, K. Toma, H. Tamiaki, A. Hotta

Journal of Applied Polymer Science （Wiley）  135 （ 24 ） 45402 2017年06月

研究論文（学術雑誌）, 共著, 査読有り

• Access to Document (DOI)