Published papers

オゾンで高分子物質を処理することによって、その表面への多種類のポリマー鎖のグラフト化が可能となった。

ポリウレタンを低温プラズマ処理し、表面への側鎖にポリエチレンオキサイドを有するビニルモノマーのグラフト重合を行った。この改質により表面へのタンパク質の吸着および血小板の粘着は著しく抑制された。

Free-radical polymerization of a termonomer system comprising acrylamide (AAm) N,N′-methylenebisacrylamide (MBAAm) and styrene (S) initiated by water-soluble ammonium peroxodisulphate (APS) or by toluene-soluble dibenzoyl peroxide (DBP) in inverse microemulsion (toluene/ S/AOT//water//AAm/MBAAm), leads to the formation of partly hydrophobized crosslinked polymer particles of tailored chemical composition, degree of crosslinking and polymer particle size. Styrene strongly decreases the rate of terpolymerization, while the presence of MBAAm has almost no effect on the polymerization rates observed. This conclusion is valid for both APS and DBP initiators. Increase of the S/T mass ratio (T is toluene) in inverse microemulsion leads to an increase of polymer particle diameter from about 20 nm to about 50 nm attributed to toluene swelling of the styrene-rich structural moieties of AAm-co-S copolymer located on the surface of polymer particles. Polymerization kinetics measurements pointed to the important role of exiting water soluble AAm and MBAAm monomer radicals generated by thermal decomposition of APS in water pools of inverse micelles for initiation of polymerization reactions of sparingly water-soluble S monomer in the oil-phase of the inverse microemulsion. It was shown that the polymerization and copolymerization reactions of S in the presence of AAm and/or MBAAm are effectively initiated by water-soluble APS and also by oil-soluble DBP initiators. During dialysis the polymerized single-phase water/oil Winsor IV inverse microemulsion gradually converts itself into a two-phase oil/water Winsor I dispersion system with volume fraction of aqueous phase Φaw≈0.950. The water phase contains water swelled, crosslinked polymer particles of diameters 80-300 nm. During dialysis, toluene and the sodium salt of bis(2-ethyl hexyl)sulphosuccinic acid (AOT) partition between the oil phase of the dialysed dispersion system and the water dialysate. After evaporation of water from the dialysed inverse microemulsion, solid, dried, crosslinked polymer particles in the form of a transparent film, almost uncontaminated by AOT surfactant, were obtained. © 2000 Society of Chemical Industry.

Poly(N-isopropylacrylamide) (PNIPAM) particles are highly swollen below the transition temperature in water so that they become very soft and hydrophilic, but collapsed above the transition temperature to become hard and hydrophobic. Such changes bring about the discontinuous temperature dependence of adsorbability of protein, activity of immobilized enzyme, cell activating ability of the particles. The transition temperature of PNIPAM was changed by binding something to the chain end and this property was used to control the enzyme activity with temperature. Sudden change in the topology of the particle surface by quick temperature change gave excess stimulus to cells when the change was transmitted straightly to the cells.

微粒子表面の感温性のポリマー鎖に酵素の固定化を行った。この微粒子は温度変化により３つのサイズに変化した。それぞれの状態で酵素活性は異なり、温度による制御の可能性が示唆された。

We report a novel drug delivery system for apoptosis induction by a "smart" polymer vehicle possessing thermosensitivity and bioaffinity. The polymer chain was prepared by copolymerization of N-isopropyl-acrylamide and N-methacryloyloxysuccinimide. Cell-adhesive RGDS peptide was conjugated with the copolymer as a ligand model for bioaffinity. When the temperature was increased, nanoscale aggregates precipitated from a copolymer aqueous solution. Either dolichyl phosphate (dol-p), which is an apoptotic inducer, or dolichol was added to aggregates at around the precipitation temperature (31°C), and the temperature was raised to 37°C for incorporation. Aggregates incorporating dol-p or dolicol were added to a human promonocytic leukemia U937 cell suspension at 37°C. When the temperature was lowered to 25 °C, cells underwent apoptosis in the presence of Ca2+. Probably, copolymer vehicles were concentrated on a cell surface through the binding of RGDS and integrin and the release of lipid inducers was caused by the disruption of vehicles in response to temperature.

Cell membrane fluidity and changes of cellular lipids of U937 cells during apoptosis are compared between the cells treated with dolichyl phosphate (dol-P) and etoposide. Dol-P induced lateral cell membrane perturbation immediately after addition and continued for at least 40 min. However, etoposide induced apoptosis without increase in cell membrane fluidity. Phosphatidylethanolamine was translocated together with phosphatidylserine after 4 hr of treatment in both dol-P and etoposide treated cells. The concentration of lipid levels changed in dol-P-induced cells and the cholesterol/phospholipid ratio almost doubled. Conversely, none of the phospholipid and cholesterol levels changed in etoposide treated cells. Although both dol-P and etoposide induce apoptosis, dol-P, but not etoposide, appeared to function as a modulator of membrane fluidity and to change membrane constituents and membrane physiology during the course of apoptosis.© 2002, Japan Oil Chemists’ Society. All rights reserved.

We fabricated porous polymeric membranes using the miniemulsion templating method to investigate the transmitted and scattered lights in terms of the Christiansen filter effect. This method made it possible to produce porous polymeric membranes with different refractive indices by polymerization of different monomers and copolymerization of monomers. When a membrane with an open-cellular structure was immersed in a liquid, the transmitted light was observed at a wavelength where the refractive indices of the polymeric phase and the liquid matched. Angle-independent color derived from the scattered light could also be observed. When the porous membrane of poly(2-ethylhexyl methacrylate) (EHMA) was immersed in a mixture of different kinds of liquids, the maximum wavelength of the transmission (λmax) changed according to the refractive index matching of the polymeric phase and the liquid, resulting in the change in coloration. Next, when the P(EHMA-co-EGDMA) membrane was immersed in a mixture of toluene and d-limonene, λmax and color varied depending on their mixing ratios. This coloration was controlled by temperature and the refractive indices of the polymeric phase and the liquid. Furthermore, we could estimate the refractive index of PEGDMA using λmax values obtained by immersing it into liquids with different refractive indices.

好中球の非特異的な活性化についての知見を得るために、ポリスチレン表面の表面化学改質を行った。その表面と接触した細胞の活性酸素の放出やレセプター類の発現を調べた。

The effects of the anti-platelet agent dipyridamole on vascular endothelial cells were assessed by measurement of the injury index induced by oxygen stress. Vascular endothelial cell injury was assayed by measuring 51 Cr release from labeled vascular endothelial cells. Leukocytes activated by phorbol 12-myristate 13-acetate (PMA) were used to induce the injury of endothelial cells. In this system, dipyridamole suppressed endothelial cell injury in a dose dependent manner (0.1-10 4mUM) while it had no effect on production of superoxide anion in PMA-activated leukocytes. Treatment of endothelial cells with hydrogen peroxide also induced endothelial cell injury in a dose dependent manner (50-150 μM). Dipyridamole also prevented the endothelial cell injury induced by hydrogen peroxide with a dose dependent fashion (1-10 μM). There were no significant changes in the activities of catalyzing enzymes such as catalase and glutathione peroxidase in the endothelial cells following dipyridamole treatment. In contrast, dipyridamole significantly increased the cyclic GMP content of endothelial cells in a dose dependent manner (1-10 μM). Addition of 8-bromo-cyclic GMP (1 mM) to the culture also protected endothelial cells from injury induced by hydrogen peroxide, but 8-bromo-cyclic AMP did not. These data suggest that the protective effect of dipyridamole against oxygen stress is correlated with the increase in the cyclic GMP content of the endothelial cells. © 1995 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.

Liposomes are valuable drug and cosmetic carriers but face limitations in stability and active loading from external phases. Polymer-coated liposomes (liponanocapsules) have improved robustness, and this study advances the approach by acetylating chitosan-coated liposomes to form chitin-deposited capsules, leveraging chitin's biocompatibility and insolubility to enhance the structural and colloidal stability in organic solvents and oils. This represents the first report of suspensions of liposome-based capsules in such media. Anionic liposomes prepared from dilauroyl phosphatidyl acid acquire a hydrodynamic diameter increase from 100 to 190 nm and shift in ζ-potential from negative to positive upon chitosan deposition. Surface acetylation of the deposited chitosan with sodium acetate and a condensing agent yields chitin-deposited liposomes (Lipo[-]-chitin), with the degree of acetylation (DA) controlled by changing the reagent concentration. Lipo[-]-chitin shows a shift in the phase transition of the lipid membrane to a higher temperature owing to the suppression of lipid fluidity, suggesting that the capsules become rigid and robust. The hydrodynamic diameter of Lipo[-]-chitin in water increases with the DA because of capsule aggregation. By contrast, Lipo[-]-chitin becomes smaller in mixtures of water and water-miscible organic solvents, such as dimethyl sulfoxide (DMSO), ethanol, and acetone, indicating a positive impact of acetylation on the colloidal stability. In mixtures of water with DMSO or ethanol, a higher DA reduces the colloidal stability, whereas the opposite trend is observed in acetone. These results indicate that the colloidal stability of the acetylated capsules is strongly governed by the DA. Notably, Lipo[-]-chitin with a higher DA can be suspended in 100 % ethanol without aggregation or rupture. The solvent can then be replaced with poorly water-soluble organic solvents, such as isododecane. This enabled active loading of α-tocopherol as a lipophilic cargo into the capsule. Overall, surface acetylation of chitosan-coated liposomes produces chitin-deposited nanocapsules with enhanced solvent resistance, offering a promising platform for pharmaceutical, cosmetic, and nanocomposite applications.

Many proteins tend to aggregate during refolding, especially at high protein concentrations. To reduce aggregation and improve the refolding yields, denatured/reduced lysozyme at 0.5 mg ml-1 was refolded using disulfide-carrying microspheres. The extent of renaturation was evaluated by measuring the content of recovered soluble protein and its enzymatic activity. Addition of the dispersion of the modified microspheres to the aqueous solution of reduced lysozyme resulted in the binding of the proteins on the microsphere surface, followed by the spontaneous release of the bound proteins. As a consequence, a 10% active enzyme was obtained. However, no renaturation occurred without the microspheres due to aggregation. Moreover, when glutathione was added 20 h after incubation with the microspheres, the refolding yields could increase to ~40%. These results indicate that the disulfide moieties of the microspheres play an important role in preventing the aggregation process and catalyzing the refolding reaction through the thiol-disulfide interchange reactions. Copyright (C) 2000 Elsevier Science B.V.

To improve the water resistance of products prepared from water-soluble cellulose derivatives, we prepared cellulose-based nanoparticles without chemical modifications such as crosslinking. We employed a W/O (water-in-oil) miniemulsion as a nanoreactor to prepare cellulose-based particles. Methylcellulose (MC) was selected as the cellulose-derived biomass polymer. Aqueous nanodroplets, including MC, were suspended in corn oil by homogenization and ultrasonication. MC hydrogel nanoparticles (MC-H) were subsequently obtained via the gelation of MC within the nanodroplets with increasing temperature. Next, to obtain MC xerogel nanoparticles (MC-X), we carried out water evaporation from MC-H. Furthermore, MC-X with different inner structures could be obtained by tuning the temperature and pressure of the evaporation conditions. MC-H and MC-X showed high water resistance because of the strong association of MC chains, which was promoted in confined vessels such as nanodroplets and nanoparticles. In addition, the release of water-soluble substances from MC-H was promoted at 4 °C below the dissolution temperature of MC, whereas MC-X exhibited suppressed release because of the strong association of MC chains. To explore the utility of MC-X as a biomass-derived filler, it was embedded in the polymer film. MC-X was slightly aggregated but evenly distributed within the film without compromising its transparency.

To embed particles into human hair, core-shell (CS) particles were prepared by seeded emulsion polymerization and were arrayed to the surface of natural hair via dip coating. The particle-coated natural hair was treated at various temperatures in a controlled environment with a relative humidity of 5% (5% RH). No particle embedding was observed at 25 °C. However, the degree of particle embedding (DE) slightly increased at 50 °C and substantially at 150 °C. At 100% RH, embedding was effectively achieved at 50 °C, probably because the adsorbed water acted as a plasticizer, softening the hair. Bleached hair exhibited a significant reduction in surface wettability, whereas the DE of CS particles remained comparable to that of natural hair, indicating that surface wettability does not affect the particle embedding process. On the other hand, hair treated with a reducing agent displayed a notable increase in the DE, reaching approximately 20% even at 25 °C and increasing to 35% at 150 °C. At 100% RH, DE values dramatically increased to approximately 35%, even at 25 °C. Sudan Black B was incorporated into the CS particles to produce stained particles (CS(B) particles). This staining process enabled the coloration of bleached hair by arranging and embedding CS(B) particles. Visual observation confirmed uniform coloration of the hair samples. The color difference (ΔE*) results strongly indicated that bleached hair could be effectively dyed with CS(B) particles. Additionally, the color of CS(B) particle-embedded hair remained stable after ultrasonication, demonstrating that particle embedding ensures long-lasting hair coloration by securely embedding the stained particles within the hair samples.