Shizuko Sato

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.

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.

Enthalpic studies on the formation and interaction of micelles of a nonionic, surfynol 465

The enthalpy of dilution, ΔdilH, of a nonionic surfactant, Surfynol 465, was measured in water at 25°C using a twin-type microcalorimeter. Both the amounts of water in the aqueous solution to be diluted and those in the diluent were kept constant, and the amount of Surfynol 465, n2, was varied. The value of ΔdilH was always negative and decreased nonlinearly with n2. The relative apparent molar enthalpy, φL2, increased sharply from nil, reached a plateau at 27.8 kJ mole−1, and increased again with the concentration of Surfynol 465. The relationship between ΔdilH and n2 was analyzed on the basis of an association equilibrium model and by using the optimal standard enthalpy of micellization at 23.7 kJ mole−1. In the analysis, an excess enthalpy of micelle in the concentration region higher than 0.4 mole kg−1 was found. An overlapping model was proposed for the excess enthalpy.

The contact angle of phospholipid monolayer on a wilhelmy plate

Abstract Contact angles of phospholipid monolayers with polished glass plate were measured by a Wilhelmy method. On monolayers of dipalmitoyl phosphatidyl choline and sphingomyelin with choline residue, we obtained finite contact angles which increased with the increase of surface pressure. On the other hand, on monolayers of dipalmitoyl phosphatidyl ethanolamine without choline residue and fatty acids, such as myristic acid and stearic acid, we had nearly zero contact angles in the surface pressure range of 0–40 dyn cm −1 .

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.

Raman scatterings of colloidal silver and gold prepared in the presence of a nonionic surfactant, Surfynol 465

The FT-Raman and resonance Raman scatterings of colloidal silver or gold formed in the presence of a nonionic surfactant, Surfynol 465, were studied. The intensity of Raman scattering of colloidal solution was strongly affected by the power of laser for excitation. At the low power, the intensity of scattering and the spectrum of colloidal solution were normal. However, at the high power, the intensity of Raman scattering anomalously increased over the whole frequency region, suggesting the surface enhanced Raman scattering (SERS) on colloidal silver or gold. And in the Raman spectra new bands were found in addition to bands of starting materials. Through the assignment of new bands, the working mechanism of Surfynol 465 for the formation of colloidal silver or gold was discussed.

The transfer rate of dipalmitoyl lecithin monolayer from aqueous to glass surface by contact angle measurement

Abstract The contact angle of dipahnitoyl lecithin monolayer on 0.1 M NaCl aq. with a fixed molecular area, ca. 134 A 2 molec −1 , in the coexisting state of gaseous and liquid-expanded phases against polished glass plate was measured at 25°C by a Wilhelmy method. They increased sigmoidlly with the lapse of time after an initial jump. The rate of contact angle increase was analyzed according to a first-order kinetics with respect to the transfer of lecithin from aqueous to glass surface, giving 2.59 × 10 −3 sec −1 as an apparent rate constant.

Behavior of Nonionic Surfactant, Surfynol 465, in Aqueous Media

The acetylenic nonionic surfactant, Surfynol 465, was studied in aqueous media at 298.15 K, to characterize the various physico-chemical parameters of its monomer and micelle. To analyze the experimental data of Surfynol 465 at various concentrations, two alternative models of micelle formation, i.e., phase separation and association equilibrium, were adopted. From the measured results of surface tension, density, vapor-pressure depression, heat of dilution, and UV and 13C-NMR spectra, we estimated the aggregation number of the micelle, the association equilibrium constant, and the standard molar volume and enthalpy changes accompanying micelle formation as well as the cmc. Also, the standard molar volumes and the NMR chemical shifts of the methyl carbon were estimated separately for the monomer and the micelle. From the detailed analysis of the heat of dilution, we found a repulsive interaction between micelles.

Spreading of dipalmitoyl phosphatidylcholine on the surface of sodium deoxycholate aqueous solution

The surface pressure vs. mokcular surface area relations for dipalmitoyl phosphatidylcholine (DPPC) insoluble monolayer and sodium deoxycholate (SDC) adsorbed monolayer,L and D1, respectively, were obtained from the analyses of surface tensions measured by the Wilhelmy glass plate. Also, D1 was obtained by a drop-weight method. Next, the surface pressure time course,π(t), of the SDC aq. was measured by the Wilhelmy plate before and after DPPC was spread on the liquid surface. At DPPC spreading,π(t) jumped to a maximum,π′, and decreased along an exponential curve. The values ofπ′ with various surface amounts of DPPC and bulk concentrations of SDC were analyzed using a dual surface-region model. The model enabled the estimation ofπ′. For better fitting, modified relations were constructed in place of D1. The exponential decrease ofπ(t) was also observed on the SDC adsorbed monolayer which was rapidly compressed by a moving barrier. Theπ(t) relaxation rate constants of the SDC monolayers which were compressed by DPPC spreading and the moving barrier agreed with each other, suggesting a desorption of SDC from the surface.