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Ceramic/polymer composites and hollow ceramic microspheres are receiving attention as biomaterials as a bone/tissue substitute and cancer remedy. This article describes the advantages of the use of enzymes as “controllable precipitant supplier” in the processing of such biomaterials. It has been demonstrated that hydroxyapatite (HA)/polymer composites and hollow microspheres of Y2O3, Fe3O4, and HA may be fabricated in a shorter time and using a simpler operation. [ABSTRACT FROM AUTHOR]

Glass-like carbon/silica composites were prepared from rice hull and phenolic resin. Monolithic composites were prepared by carbonizing green bodies made from phenolic resin and rice hull in nitrogen atmosphere at temperatures raging from 1173 K to 1773 K. The resultant composites consisted of approximately 70 mass% of glass-like carbon and 30 mass% of silica, the latter being originated from rice hull. The highest compressive strength, bending strength, and fracture toughness were 227 MPa, 50 MPa, and 0.80 MPam1/2, respectively. The composites did not show any detectable hygroscopic expansion upon immersing in water. The mechanical properties were not deteriorated up to 1573 K, as long as the silica maintained its amorphousness. [ABSTRACT FROM AUTHOR]

Co3O4 thin films were deposited onto bare and ITO (Sn-doped In2O3)-coated glass substrates directly from aqueous solutions at a temperature as low as 323 K. The principle of the deposition of the thin films was based on the slow oxidation of Co2+ ion with BrO3- ion to Co3+ ion and subsequent spontaneous hydrolysis to form a Co3O4 colloid. When the rate of oxidation was slow enough to allow heterogeneous nucleation to predominate, smooth and adherent thin films were obtained. The thin films consisted of particles less than 100 nm in diameter with low crystallinity and showed electrochromism upon applying anodic/cathodic voltage in a basic aqueous electrolyte and electrocatalytic activity for oxygen evolution. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Background: Periosteal expansion (PEO) results in the formation of new bone in the space created between existing bone by expanding the periosteum. PEO has already been performed on rabbit parietal bone and effective new bone formation has been demonstrated. In this study, the utility of a polyethylene terephthalate (PET) membrane as an activator was evaluated in the more complex morphology of the mandible. Methods: A PET membrane coated with hydroxyapatite (HA)/gelatine was placed in the rabbit mandibular bone at lower margin of mandibular molar region underneath periosteum, and screw‐fixed. In the experimental group, the membrane was bent and screw‐fixed along the lateral surface of the bone, with removal of the outer screw after 7 days followed by activation of the membrane. The experimental group was divided into two subgroups: with and without a waiting period for activation. Three animals were euthanized at 3 weeks and another three at 5 weeks postoperatively. Bone formation was assessed using micro‐CT as well as histomorphometric and histological methods. Results: No PET membrane‐related complications were observed. The area of newly formed bone and the percentage of new bone in the space created by the stretched periosteum did not significantly differ between the control and experimental groups. However, in the experimental group a greater volume was present after 5 weeks than after 3 weeks. Histologically, bone formation occurred close to the site of cortical bone perforation, with many sinusoidal vessels extending through the perforations in the new bone into the overlying fibrous tissue. Inflammatory cells were not seen in the bone. [ABSTRACT FROM AUTHOR]

This paper describes a method for pressureless sintering of calcite (CaCO 3 ) powders and the physical properties of the obtained dense calcite ceramics. Eutectic mixture of the KF - NaF - LiF system was found to be a good sintering aid that promoted the densification and the grain growth of calcite. Calcite sample with high relative density of 99.0% was attained on sintering the calcite fine powder at temperatures as low as 723 K for 3 h in air, without calcite undergoing thermal decomposition. Particle size of the calcite powder was found to be an important factor in achieving densification. The thermal conductivity and dielectric constant were found to be close to those of calcite single crystals; however, Vickers hardness and Young’s modulus were lower than those of calcite single crystals. Thermally stimulated depolarization current of calcite ceramics was higher than that of calcite single crystals and hydroxyapatite ceramics. [ABSTRACT FROM AUTHOR]

Abstract: In order to clarify whether the mixed valence of Eu2+/Eu3+ exists in a self-compensation mode in Eu-doped BaTiO3, the site occupation and valence state of Eu ions in barium titanate were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), electron spin resonance (ESR), Raman spectroscopy (RS), and dielectric measurements. The results indicate that Eu ions may enter both Ba- and Ti-sites as Eu3+, forming a self-compensation mode with the amphoteric behavior. Self-compensation characteristics of Eu ions in BaTiO3 are reflected by an expansion in unit cell volume, evolution of the 830cm−1 Raman band, strong diffusion of the dielectric peak, disappearance of the Eu2+ ESR broad signal, and a g =2.004 signal independent of temperature. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In the present work, self-organized TiO2 nanotubes were synthesized using an anodization technique. Titanium foil was used as the substrate for growth of oxide nanotube arrays. The anodic growth experiment was performed in a two-electrode electrochemical cell using Pt as counter electrode and titanium foil as the working electrode. Effects of electrolyte concentration, anodization voltage, and anodization time on morphology of oxide layer were investigated. Aqueous NH4F in propylene glycol was used as the electrolyte at concentrations of 0.1 and 0.3 M. Anodization voltages of 20 V and 40 V were used. Anodization time was varied from 2 to 5 hours. Field emission scanning electron microscope (FE-SEM) was employed for the morphological and structural characterization of formed layers. FE-SEM micrographs of Ti foil samples in different electrolyte concentrations at 20 V for 5 hours had larger diameter tubes at lower electrolyte concentrations. Similar observations were made at a higher anodization voltage. TiO2 nanotubes made in 0.1 M NH4F had larger diameters, 60 - 80 nm. In 0.3 M NH4F, tube diameters were less than 50 nm. Nanotubes formed at a different anodization voltage (20 V vs. 40 V) had similar surface morphology but different in diameter size. However, the higher anodization voltage produced slightly shorter of nanotubes. The length of nanotubes increased with increasing anodization time. Anodization time affected thickness of oxide layers and the surface morphology of samples. Furthermore, a clear separation most nanotubes with inter-tube spacing were observed in samples prepared with longer anodization time. Morphological changes resulted in lower surface density of the tubes, which corresponding to the number of tubes per unit area. Moreover, TiO2 nanotubes samples prepared with different anodization time were evaluated the photocatalytic performance using a spin trap electron spin resonance (ESR). ESR spectra of 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO) solutions on TiO2 nanotubes samples after UV irradiation was observed. The intensity of the signals varied with anodization time. The highest signal to marker (S/M) ratio was obtained for TiO2 nanotubes prepared for 2 hours, indicating that this sample generated DMPO-OH. radicals more actively than the other samples. TiO2 nanotubes prepared for 2 hours showed the highest photocatalytic performance. [ABSTRACT FROM AUTHOR]

The biochemical mechanism behind the strong binding between titanium and living bone has not been fully elucidated, in spite of worldwide clinical application of this phenomenon. We hypothesized that one of the core mechanisms may reside in the interaction between certain proteins in the host tissues and the implanted titanium. To verify the interaction between titanium and proteins, we chose the technique of chromatography in that titanium spherical beads (45 μm) were packed into a column to obtain a bed volume of 16×50 mm, which was eluted with phosphate buffered saline (PBS) and a straight gradient system made by using PBS and 25 mM NaOH. Fetal calf serum, albumin, lysozyme, casein, phosvitin and dentin phosphoprotein (phosphophoryn) were applied to the column. Most part of albumin and lysozyme eluted with the breakthrough peak, indicating practically no affinity to titanium. Fetal bovine serum also eluted mostly as the breakthrough peak, but distinct retained peak was observed. On the other hand, α-casein, phosvitin and phosphophoryn exhibited a distinct retained peak separated from the breakthrough peak. We proposed that phosphate groups (phosphoserines) in the major phosphoproteins, α-casein, phosvitin and phosphophoryn may be involved in the binding of these proteins with titanium. [ABSTRACT FROM AUTHOR]

Titania hollow microspheres (THMs) were prepared by an interfacial reaction method using titanium bislactate as the titanium source. An aqueous solution of titanium bislactate was dispersed in hexane to form a W/O emulsion, which was then poured into an aqueous solution of polyethyleneimine (PEI). Since PEI catalyzes the hydrolysis of titanium bislactate, titania precipitates at the W/O interface, and THMs of 50–80 µm diameter are thus formed. The THMs calcined at 973 K exhibit good photocatalytic activity, as monitored by the decomposition of methylene blue. [ABSTRACT FROM AUTHOR]