Masakatsu Yonese

Recyclable characteristics of hyaluronate-polyhydroxyethyl acrylate blend hydrogel for controlled releases.

Hyaluronate-hydroxyethyl acrylate blend hydrogels which have a wide range of composition and characteristics were investigated. Glycidyl methacrylate derivatized hyaluronate (GMA-HA) were synthesized by coupling GMA to hyaluronate (HA) in the presence of a photoinduced initiator for polymerization. By copolymerizing radically GMA-HA and hydroxyethyl acrylate (HEA) under various compositions (weight ratios of HEA and GMA-HA: 1-20), GMA-HA hydrogels could be prepared in wide ranges of characteristics. These HA-PHEA gels possessed the feature that the dried ones recovered completely to the original swelling states on repeated runs, i.e. recyclable gels. The water contents of these hydrogels in equilibrium swellings in water (W(w)) were 0.99-0.86, and their viscoelastic properties were measured by a creep. The spontaneous elastic moduli were 1.05x10(5)-1.94x10(5) N m(-2), and they were mechanically tough. Their effective charge densities were estimated from the partition coefficients of sodium benzoate (NaBA) and decreased from -0.033 to -0.044 mol dm(-3) with increasing contents of HEA. Release of NaBA was studied, and the diffusion coefficients were found to be from 6.95x10(-10) to 0.12x10(-10) m(2) s(-1) with increasing the ratio of HEA. Their diffusion coefficients were found to be much less than the values estimated from the lattice model.

Influence of ethanol on physical state of freeze-dried mannitol.

PurposeThe purpose of this study is to characterize freeze-dried mannitol prepared from an ethanol-containing solution as a function of the ethanol ratio, mannitol concentration, and annealing in the freeze-drying cycle.MethodsThe characteristics of the freeze-dried mannitol were evaluated by X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The reconstitution time was measured for the freeze-dried solids as well as the residual moisture and ethanol by Karl–Fischer titration and gas chromatography, respectively.ResultsThe XRD pattern of 5% (w/v) mannitol freeze-dried from aqueous solution with no annealing cycle showed all the five characteristic peaks at 13.6° and 17.2° 2θ for the α polymorph, at 14.6° and 23.4° 2θ for the β polymorph and at 9.7°2θ for the δ polymorph. The addition of ethanol to the initial solutions resulted in only a peak at 9.7° 2θ, indicating the presence of only the δ polymorph, regardless of the ethanol ratio in the initial solutions used [10, 20, 30, and 40% (v/v)]. However, annealing during freeze-drying influenced the XRD pattern; in particular, for the solid prepared from the 10% ethanol solution. Annealing of the 10% ethanol solution promoted the formation of the α polymorph and produced a different peak that might be attributable to another polymorph. In DSC thermograms, an endotherm and a subsequent exotherm were found in the temperature range of 150°C to 160°C, which corresponded to the transition of the δ form to α or β forms. The magnitude of this transition was smaller as the ethanol ratio increased for the solids from ethanol-containing solutions with an annealing cycle. In other words, annealing of the ethanol-containing solutions promoted δ polymorph formation in the lyophiles. In addition, the mannitol concentration affected the polymorphism in freeze-dried solids prepared from aqueous and 10% ethanol solutions. Addition of ethanol in the initial solution, in particular, at a lower ethanol level (10% v/v), and a higher concentration of mannitol could also promote the generation of lumps in freeze-dried solids during reconstitution, and result in longer reconstitution time. The residual moisture levels were less than 0.5%, and residual ethanol levels were less than 0.1%, irrespective of the formulation used.ConclusionsThe physical state and reconstitution time of the freeze-dried mannitol appears to be a complex function of the ethanol and mannitol concentrations in the initial solution before freeze-drying and of annealing during the freeze-drying process.

Gel immobilization of centimeter-sized and uniform colloidal crystals formed under temperature gradient.

We report the fabrication of large and high-quality charged colloidal crystals that are incorporated in a polymer hydrogel matrix. The colloidal crystals are prepared by the thermally induced unidirectional crystallization of colloidal silica in coexistence with pyridine, whose dissociation degree increases with temperature. Their crystal structures are immobilized in the polymer hydrogel matrix by photoinduced polymerizations. The crystals are large sized (maximum dimensions: 1 x 10 x approximately 30 mm), and their lattice planes are well oriented and parallel to the gel surface. Furthermore, they have excellent spatial uniformity in the Bragg wavelengths (<0.7% in standard deviation). The present gelled colloidal crystals, which are unique in that they have large sizes as well as good optical uniformity, will be useful as photonic materials.

Formation of colloidal silver in the presence of a nonionic surfactant, Surfynol 465

The formation of colloidal silver in the presence of a nonionic surfactant, Surfynol 465, was studied at various temperatures. By simply mixing equal volumes of AgClO4 aq. (1–10 mmol kg−1) and Surfynol 465 aq., the colloidal silver was formed. The colloidal solution had well over ten times the amount of fine silver particles in the solution formed by the ordinary methods. The first factor to form the colloidal silver without aggregation was the molar ratio of Surfynol 465 to AgClO4, and the optimum ratio increased with increasing the concentration of AgClO4 or the temperature. In the fraction of colloidal silver collected through the gel filtration, Surfynol 465 was also found in the micellar state. From these results, it was suggested that Surfynol 465 was a protecting agent of colloidal silver as well as a reducing agent of AgClO4 in the similar manner to the case of colloidal gold.

DIFFUSION-REACTION OF UREA THROUGH MULTIMEMBRANE CONTAINING UREASE : EFFECTS OF MICROENVIRONMENTS AROUND UREASE AND ASYMMETRY OF THE MEMBRANE

Abstract Diffusion-reactions through enzyme membranes were studied by using a multimembrane, consisting of an enzyme layer sandwiched between films. The multimembrane was shown to possess the following characteristics: (1) the microenvironments around the enzyme can be altered arbitrarily by adding polymers etc., and (2) the asymmetries of the multimembranes can be controlled easily by using various films. Diffusion-reactions of urea through symmetric and asymmetric multimembranes having a urease layer were studied by measuring total fluxes J p T and flux ratios — J p I / J p II of one of the products (NH 4 + ion) into a donor and an acceptor compartment. By adding sodium alginate NaAlg to the urease layer, the pH showing the maximum J p T shifted towards the alkaline pH region by 0.6 pH unit, and the maximum J p T increased. From the value of the pH shift, the electrostatic potentialψ α around the active site of the urease was calculated to be − 0.0343 V. The values of J p I / J p II through the symmetric multimembrane were in the range 1.2–1.7, and those for the asymmetric multimembrane were in the range 0.2–0.3. In the diffusion-reaction through the latter membrane, carbamate anions were found to play an important role. Diffusionreaction through the multimembranes was analyzed by assuming that the reactions in the enzyme layer obey a first order reaction.

Two Dimensional Auto-organized Nanostructure Formation of Hyaluronate on Bovine Serum Albumin Monolayer and its Surface Properties

The layer-by-layer interaction between sodium hyaluronate (NaHA) and bovine serum albumin (BSA) were studied by a quartz crystal microbalance (QCM) method. Their surface structures, adhesive force F ad and frictional behavior were investigated using an atomic force microscope (AFM). The adsorptions of NaHA on the BSA monolayer were found to be the Langmuir type. The surface structures of NaHA adsorbed on the BSA monolayer were found to form hexagonal-like networks and the mesh size decreased with increasing molecular weight M w. The F ad between the AFM tip and the surfaces of the saturated NaHA layers increased with increasing value of M w. However, the frictional coefficient of saturated NaHA layer was found to decrease from 0.933 to 0.191.

Subambient Behavior of Mannitol in Ethanol-Water Co-solvent System

PurposeThe purpose of this study is to characterize the freezing behavior of mannitol in ethanol–water co-solvent systems in comparison with the corresponding aqueous solution.MethodsSubambient differential scanning calorimetry (DSC) and microscopy techniques were used to investigate the freezing behavior of mannitol in aqueous solutions and in ethanol–water co-solvent systems.ResultsThe DSC thermogram of the frozen aqueous solution, which was warmed after cooling at 5.0°C/min, consisted of a glass transition, an endothermic transition, and a crystallization exotherm from mannitol, respectively. The thermograms of ethanol-containing solutions were different in view of including some thermal events attributable to ethanol hydrates. The glass transition of amorphous mannitol was also observed in the thermograms, but became unclear with increasing ethanol in the co-solvent system. The microscopy experiments enabled understanding of the subambient behavior of mannitol. Ethanol was largely removed by vacuum drying rather than freeze-drying. In addition, such manipulations as annealing during the freezing process and slower cooling (0.5°C/min) enhanced the crystallization of mannitol in the frozen system.ConclusionsIn the presence of ethanol, crystallization of mannitol was inhibited under subambient conditions. Annealing or slower cooling promoted the crystallization of mannitol during the freezing process.

Studies of transport of strong electrolytes and carboxylic acids through lipid—nitrocellulose membranes on the basis of a lipid multibarrier channel model

Lipid-dispersed nitrocellulose membranes (L-N membranes) were prepared by casting mixed solutions composed of L-α-lecithin, β,γ-dipalmitoyl and nitrocellulose in a glass vessel. Their lipid contents varied from 0 to 0.2 in the weight ratio of lipid to nitrocellulose, and their water contents were adjusted to 60-65% w/w under experimental conditions depending on the composition of the casting solutions. Various strong electrolytes (LiCl, NaCl, KCl, MgCl2 and CaCl2) and carboxylic acids (acetic acid, propionic acid, butyric acid and valeric acid) were permeated through the membranes in a two-compartment cell at 25°C while stirring two bulk solutions at 650 rpm. The results were analyzed quantitatively by a lipid multibarrier channel model, i.e., a membrane model which consists of water channels, WC, and lipid barrier channels, LC. The membrane parameters, such as the fractional areas of WC and LC and tortuosity, were obtained from the water content, the lipid content and the permeability of strong electrolytes, and the effects of the lipid content on these parameters were then examined. The permeability coefficients, P, of L-N membranes were theoretically shown to be a function of the ratio of the diffusivity of a permeant through the water channel to the diffusivity through the lipid barrier. In the case of weak electrolytes the effeccts of their degree of dissociation on the values of P were analyzed. Furthermore, the permeability coefficients of carboxylic acids through the lipid barrier phase in the channel were obtained from the values of P.

Thermodynamic properties of dilution of chondroitin 4-sulfate having tetraalkylammonium counterions

The dilution enthalpies,ΔdilH, of tetraalkylammonium chondroitin 4-sulfate (R4NChSA) and polyacrylate (R4NPAA) having methyl (Me), ethyl (Et), propyl (Pr) and butyl (Bu) as alkyl groups (R) were measured to elucidate the effects of hydrophobic counterions. TheΔdilH of R4NChS-A and R4NPAA were negative (exothermic) and decreased as the carbon number of tetraalkylammonium cation (R4N+) increased. These results were found to possess the same effects onΔdilH as these of bromides. The non-electrostatic terms of dilution enthalpiesΔdilHn of R4NChS and R4NPAA were evaluated by using the electrostatic terms ofΔdilH obtained from Mannings theory. TheΔdilHn of R4NChS-A and R4NPAA decreased, i.e., their exothermic tendencies increased as the carbon number of R4N+ increased, and the rate of decrease of the R4NPAA was more than that of the R4NChS-A. These results are discussed in relation to the increase of the hydrated water structure around R4N+ on dilution.

Isooctane/water interfacial adsorptions of chondroitin sulfates having hydrophobic counterions

Abstract Interfacial adsorption of chondroitin sulfates (ChS-A) between isooctane and aqueous salt free solution were studied by interfacial tensions obtained from a drop volume method to elucidate effects of hydrophobic counterions on the adsorption. As counterions of ChS-A, NH 4 + and tetraalkylammonium ions R 4 N + ((CH 4 ) 4 + , (C 2 H 5 ) 4 N + , (C 3 H 7 ) 4 N + and (C 4 H 9 ) 4 N + ) were used. Increasing with the carbon numbers of R , the interfacial tensions showed more rapid decreases with concentrations of R 4 NChS-A than those of R 4 NBr. The former interfacial excesses Γ p were obtained using mean activity coefficients calculated from their osmotic coefficients. Γ p of R 4 NChS-A increased with the carbon numbers of R and were saturated in the region of very diluted concentrations about m = 10 −4 mol/dm 3 based on the concentration of the counterions. The interfacial excesses of R 4 NBr Γ were saturated at almost m = 2 × 10 −2 mol/dm 3 , which required almost 200 times as much as those of R 4 NChS-A. The saturated interfacial excesses of the counterions of R 4 NChS-A were found to be much more than those of R 4 NBr. The effects of the arrangements of the counterions along ChS-A chains enhanced their interfacial adsorptions, especially in the cases of the carbon numbers of R > 2.