Hidero Unuma

Preparation of transparent amorphous tungsten trioxide thin films by a dip-coating method

The amorphous tungsten trioxide (a-WO3) thin film is one of the most promising materials for electrochromic display (ECD). There are many methods for preparing a-WO 3 films; vacuum vapour deposition [1, 2], sputtering [3], spraying [4], anodization [5], decomposition of a complex compound [6] or polymerization of tungstoic acid [7]. However, large-scale and complicated equipment is needed in vacuum vapour deposition and sputtering, and large energy consumption or long duration are also required in other methods. The dip-coating method, which has recently been reviewed by some authors [8, 9], has possibilities to overcome such drawbacks. Thin films with a large section can also be obtained by this method. Yamanaka [10] prepared a W O 3 film from toluene solution of hexaphenoxy-tungsten by spin coating and thermal decomposition, but the film was coloured brown because of incomplete decomposition of organic matter. In the present report, we describe the preparation of colourless and transparent a-WO 3 thin films from tungsten hexaethoxide by adopting suitable heat-treatment Resultant properties, such as electrochromism of the films, are also discussed. 1.0 g tungsten hexaethoxide (Rare Metallic Co, Ltd, 99.99%) was dissolved into a mixed solvent of 15 ml butanol and 0.2ml acetylacetone by refluxing at

Preparation of thin films of MnO2 and CeO2 by a modified chemical bath (oxidative-soak-coating) method

Thin films of MnO2 and CeO2 were deposited on glass substrates directly from aqueous solutions in a temperature range from 313 to 333 K by a modified chemical bath deposition technique. The principle of the film deposition was based on the oxidation of Mn2+ and Ce3+ ions in homogeneous solutions and subsequent heterogeneous nucleation of MnO2 and CeO2 on the substrates. We have named this method as “oxidative-soak-coating” method. The film thicknesses after a 24-hour deposition were 1 μm and 60 nm, respectively. Thin films consisting of Mn3O4 and MnOOH were also deposited by changing the pH of the starting solutions for the deposition of MnO2. The effects of the composition of the starting solution, deposition temperature, and the compatibility of the substrates to the film substances were investigated.

Promotion of osteogenic differentiation of stem cells and increase of bone-bonding ability in vivo using urease-treated titanium coated with calcium phosphate and gelatin

Abstract Because of its excellent biocompatibility and low allergenicity, titanium has been widely used for bone replacement and tissue engineering. To produce a desirable composite with enhanced bone response and mechanical strength, in this study bioactive calcium phosphate (CaP) and gelatin composites were coated onto titanium (Ti) via a novel urease technique. The cellular responses to the CaP/gelatin/Ti (CaP/gel/Ti) and bone bonding ability were evaluated with proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) on CaP/gel/Ti and CaP/Ti in vitro. The results showed that the optical density values, alkaline phosphatase expression and genes expression of MSCs on CaP/gel/Ti were similar to those on CaP/Ti, yet significantly higher than those on pure Ti (p < 0.05). CaP/gel/Ti and CaP/Ti rods (2 mm in diameter, 10 mm in length) were also implanted into femoral shaft of rabbits and pure Ti rods served as control (n = 10). Histological examination, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) measurements were performed at 4 and 8 weeks after the operation. The histological and SEM observations demonstrated clearly that more new bone formed on the surface of CaP/gel/Ti than in the other two groups at each time point. The CaP/gel/Ti bonded to the surrounding bone directly with no intervening soft tissue layer. An interfacial layer, containing Ti, Ca and P, was found to form at the interface between bone and the implant on all three groups by EDS analysis. However, the content of Ca, P in the surface of CaP/gel/Ti implants was more than in the other two groups at each time point. The CaP/gel/Ti modified by the urease method was not only beneficial for MSCs proliferation and osteogenic differentiation, but also favorable for bone bonding ability on Ti implants in vivo, suggesting that Ti functionalized with CaP and gelatin might have a great potential in clinical joint replacement or dental implants.

AMMONOLYSIS OF SILICA GELS CONTAINING METHYL GROUPS

Abstract Silica gels containing a constant concentration of methyl groups directly bonded to silicon atoms have been prepared from methyltriethoxysilane (MTES) and mixtures of tetraethylorthosilicate (TEOS) with dimethyldiethoxysilane (DMDES) and hexamethyldisiloxane (HMDS). These gels were subsequently ammonolyzed. The temperature range in which significant nitrogen is incorporated into a gel lies between 600 ° C and 800 ° C for the gel derived from MTES, between 800 ° C and 1000 ° C in the gel derived from DMDES with TEOS and at 1000 ° C in the gel derived from HMDS with TEOS. Three different nitridation processes operate depending on the temperature. The processes are reaction of ammonia with (i) methyl groups bonded to silicon atoms, (ii) SiOH groups and (iii) SiOSi bonds. The low-temperature process is dominant in MTES-derived gel and the middle- and high-temperature processes are dominant in DMDES- and HMDS-derived gels. The nitridation processes depend on the amount of SiOH groups in the gel, the thermal stability of methyl groups present and the reactivity of the gel with SiOH or SiNH 2 groups to form SiOSi, SiNHSi or nitride bonds.

Electrochromic response of WO3 and WO3-TiO2 thin films prepared from water-soluble precursors and a block copolymer template

Abstract Electrochromic tungsten trioxide (WO3) thin films are attracting renewed attention as transmittance-controllable windows for use in automobile, aircraft, and building applications. In order to achieve high electrochromic performance, high cycle stability, and high reliability, the microstructure and compositional homogeneity of WO3 thin films have to be optimized. In this study, non-doped WO3 and TiO2-doped WO3 thin films were fabricated from water-soluble precursors of tungsten and titanium, and their electrochromic response was investigated. Amorphous WO3 and TiO2-doped WO3 thin films were fabricated by calcining the spin-coated films at 573 K. The use of a PEO-PPO-PEO block copolymer as a porogen facilitated the redox reactions occurring on the thin film/electrolyte interface. Although the effect of TiO2-doping on the cycle stability of WO3 thin films has not been fully elucidated, this study demonstrated that TiO2 doping up to 15 mol% effectively enhanced the cycle stability.

Deposition of Bone-like Apatite Layers on the Surface of Poly(L-Lactic Acid) Using Immobilized Urease

Particulate layers of hydroxyapatite were deposited on the inner and outer surfaces of porous poly(L-lactic acid) monolith, PLLA, by using enzymatically derived ammonia as the precipitant. PLLA specimens were surface-modified with urease and were impregnated with aqueous solutions containing Ca2+, PO4 3- and urea. As ammonia was produced by hydrolysis of urea with the aid of the urease, hydroxyapatite precipitated predominantly on the surfaces of the porous PLLA. In contrast to the conventional biomimetic method or the alternate soaking method, it took shorter time period for hydroxyapatite particles to cover the surfaces of PLLA. The resultant hydroxyapatite was proved to be bone-like apatite because it had low crystallinity, contained carbonate ion in the lattice, and had a calcium-deficient composition.

Bone enhancing effect of titanium-binding proteins isolated from bovine bone and implanted into rat calvaria with titanium scaffold.

Based on our previous finding that a chromatography with titanium beads selectively binds phosphoproteins, including caseins, phosvitin and dentin phosphoproteins, we investigated whether bone phosphoproteins also bind to titanium. Bovine bone matrix proteins were extracted with 2 M urea/PBS after demineralization. The 2 M urea extract was directly applied to the titanium chromatography column as reported. The chromatogram showed an initial large peak at breakthrough position (non-binding fraction) and a smaller second peak eluted later (titanium-binding fraction). Both peaks were analyzed by SDS polyacrylamide gel electrophoresis. Stains-all staining which preferentially identifies phospho-proteins revealed that the first peak contained no positively stained band, while the second peak showed 4 or 5 distinctive bands indicative of bone phosphoproteins. To investigate the biological functions of the titanium-binding bone proteins (TiBP), we implanted them into calvaria of rats, combined with titanium web (TW), a highly porous titanium scaffold of thin titanium-fibers. Bone TiBP induced significantly enhanced bone formation, and new bone appeared connected directly to titanium fibers, accompanied by active blood vessel formations. Control TW alone did not induce bone formation within the titanium framework. These results demonstrate that the bone titanium-binding proteins include phosphoproteins which enhance bone formation when implanted into bone with titanium.

Enzyme-catalyzed synthesis of hydrated calcium oxalate

Abstract Calcium oxalate hydrate was prepared by a homogeneous precipitation method using hydrolysis of oxamic acid catalyzed by enzyme. A conventional enzyme screening strategy was adopted to obtain proper hydrolase that hydrolyzes oxamic acid to oxalic acid. Dimethylformamide-water mixed solvent was used to suppress the spontaneous hydrolysis of oxamic acid. The resultant precipitates were characterized by electron microscopy, thermogravimetry, Fourier transform-IR spectroscopy and X-ray diffraction. The calcium oxalate obtained by the enzyme-catalyzed precipitation was trihydrate and fibrous with a length of 50-100 μm while that obtained by a conventional homogeneous precipitation was monohydrate and granular.

Preparation of calcium phosphate cement with an improved setting behavior

Abstract In the aim of the development of a calcium phosphate cement (CPC) that allows a sufficiently long kneading time at room temperature while sets promptly at a physiological temperature, the powder components of a CPC of a TeTCP–α-TCP–DCPD system were coated with gelatin. The gelatin coating on TeTCP or DCPD-containing portion effectively retarded the setting reaction at 293 K while it did not hinder at 310 K, implying the possibility of CPC with an improved setting behavior. Compressive strength of 41 MPa was attained for a gelatin-coated CPC.

Effect of the up-front heat treatment of gelatin particles dispersed in calcium phosphate cements on the in vivo material resorption and concomitant bone formation

Calcium phosphate cements (CPCs), consisting of a mixture of calcium phosphate powders and setting liquid, have been widely used in orthopedic applications. One of the drawbacks of CPCs is their poor resorbability in the living body, which hinders substitution with natural bones. One of the strategies to facilitate the resorption of CPCs is the incorporation of bioresorbable or water-soluble pore-generating particles (porogens), such as gelatin, in the CPC matrices. In spite of numerous reports, however, little is known about the effect of the dissolution/resorption rate of the porogens on concomitant bone regeneration. In the present study, we prepared preset CPCs dispersed with 10 mass% of low-endotoxin gelatin particles 200–500 μm in diameter having different heat-treatment histories, therefore exhibiting different dissolution rate, and then the obtained CPC/gelatin composites were evaluated for in vivo resorption and concomitant in vivo bone formation behaviors. As the results, the dispersion of gelatin particles markedly promoted in vivo resorption of CPC, and enhanced concomitant bone formation, connective tissue formation, osteoblast proliferation, and vascularization. The dissolution/resorption rate was able to be controlled by changing the up-front heat-treatment temperature. In particular, when CPC/gelatin composites were implanted in distal metaphysis of rabbits, the optimum dissolution/resorption was attained by heat-treating gelatin particles at 383 K for 24 h before dispersing in CPC.Graphical abstractQuick resorption of calcium phosphate cement and concomitant bone formation by dispersing properly heat-treated with gelatin particles.