Magnetic fluid hyperthermia is a cancer treatment technique that utilizes the heat dissipated by magnetic nanoparticles exposed to an alternating current magnetic field. The heat dissipated is consequence of the conversion of the magnetic energy through different relaxation mechanisms, which depends on the physical properties of the magnetic particles. Particularly, in the case of magnetic nanoparticles, the magnetic energy is converted to heat energy either by the resistive response of the rotation of the magnetic particles (Brownian relaxation) or the rotation of the magnetic moment within the particles (Néel relaxation) to the alternating magnetic field. In this article, the main focus has been on the progress of theoretical and experimental investigations towards the realization of magnetic fluid hyperthermia (MFH) through heat dissipation by Néel relaxation of magnetite particles. We discuss about the present status and prospects of magnetite nanoparticles-based hyperthermia focusing mainly on the dissipation of heat through Néel relaxation mechanism. In doing so, an attempt has been made to review and deepen the understanding on specific topics such as (a) specific heat absorption characteristics of magnetite, especially the physical properties of particles that generate heat through Néel relaxation, (b) the preparation techniques available to synthesize particles with required properties, (c) experimental investigations carried out to determine the relative contribution of Néel relaxation to dissipate heat and their potential for in vivo application, and (d) the theoretical estimation of and experimental verification of heat diffusion characteristics of magnetite. The theoretical and experimental studies have suggested that the development of case specific treatment technologies based on an integrated approach considering both the physical constraints of the magnetic particles to be used as thermal seeds and practically feasible alternating magnetic field generators is a must for the establishment of MFH therapy in the foreseeable future.

抄録全体を表示

The present study was designed to determine the physicochemical properties of octacalcium phosphate (OCP) and its products obtained by different preparations in the presence of fluoride ions (F⁻) through hydrolysis of the synthesized OCP and co-precipitation. X-ray diffraction and chemical analyses of the products showed that OCP tended to be hydrolyzed into an apatitic structure in both preparations, while the OCP structure remained when hydrolyzed in alkaline pH and obtained by co-precipitation. The solubility decreased with increasing the F⁻ content in the hydrolyzed products but almost corresponded to that of the original OCP in the co-precipitation products. The results confirmed that the different preparation produces OCP hydrolyzates having distinct physicochemical properties that preserve the characteristics of OCP to some extent. Analysis of cytochrome c (used as a model protein of growth factors) adsorption onto the crystals indicated that the hydrolysis groups had the highest capacity to adsorb.

抄録全体を表示

The purpose of this study was to evaluate the low temperature aging degradation (LTAD) of two types of zirconia through the determination of fracture toughness before and after autoclaving. The fracture toughness of yttria stabilized tetragonal zirconia polycrystals (Y-TZP) and zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al₂O₃ nanocomposite, so called NANOZR) were determined by Single Edge V-Notch Beam (SEVNB) method before and after autoclaving at 134°C for 5 h. The fracture surfaces were characterized by micro-X-ray diffractometry and micro-Raman spectroscopy. Mean fracture toughness of Y-TZP slightly decreased from 6.31 to 5.79 MPa·m^1/2 with the autoclaving (p < 0.01). On the other hand, mean fracture toughness of NANOZR showed no change as 11.03 MPa·m^1/2 (p > 0.1) and was 1.75–1.91 times larger than that of Y-TZP. It seems to be caused by that NANOZR is susceptible to stress-induced transformation from tetragonal to monoclinic, but quite stable against LTAD.

抄録全体を表示

Cytochrome c (cyt. c, molecular size of 2.5 nm × 2.5 nm × 3.7 nm) was immobilized on six types of mesoporous silicates (MPS), having pore sizes from 2.8 to 15.0 nm, and their catalytic activities were evaluated by oxidation of thioanisol with H₂O₂. Among the silica materials, cyt. c immobilized on MPS pore size of 3.4 nm) showed the best catalytic activity, and its relative activity was improved 1.7 times over that of cyt. c solution. Enhancement of catalytic activity was obtained by immobilization on MPS having a similar size (mesopore) to the molecular size of cyt. c. Activity stability of cyt. c was also evaluated under the various conditions that caused protein inactivation, like HCl, urea, methanol, and guanidine. As results, stability was improved by the immobilization on silica material having a larger pore size (15.0 nm), offered an environment for encapsulating entire cyt. c molecules, inhibiting cyt. c from unfolding and irreversible decomposition.

抄録全体を表示

The new apatite coating method, aerosol deposition method (ADM), was carried out on poly-L-lactic acid (PLLA) substrates by a following process. Hydroxyapatite (HAp) particles formed on aerosol flow by mixing with a helium carrier gas with the velocity of about 300 m/s were accumulated on PLLA substrates via impact adhesion at room temperature. Subsequently the thus prepared HAp coating film on PLLA by ADM was treated by heating. Then it was assessed by in vitro simulated body fluid (SBF) test. As a result, it was proved that the HAp film coated on PLLA by ADM with the heat treatment has bioactivity and that bonelike apatite was formed on the substrate. It is expected that the HAp film fabricated by ADM on PLLA with the heat treatment can be used in clinical orthopedics.

抄録全体を表示

A new type of calcium phosphate (CP) paste that retains plasticity during kneading and sets promptly under a physiological condition was successfully prepared by mixing Ca₄O(PO₄)₂ (TTCP) and CaHPO₄ (DCPA) (CP powders) at 67 mass % with a gelatinized wheat starch. This paste retained plasticity because the gelatinized starch layer on the surfaces of the CP particles suppressed the rapid reaction between the CP powders. When the paste was soaked in a tris-buffered NaCl solution (TRIS), the starch layer loosened and the reaction between CP powders to form hydroxyapatite (HAp) took place at a considerable rate. The setting was found to start at 5 hours after the soaking in TRIS and proceed from the surface to the interior portion of the paste. The maximum compressive strength, 5.7 MPa which is close to that of human cancellous bone, was attained. All the pastes containing CP powders prepared in this study formed bone-like apatite on their surfaces within 1 day after being soaked in a simulated body fluid (SBF, at 310 K), independent of the CP powders content. These pastes can be stored retaining the plasticity as desired even after 3 weeks in vacuo under a cool (∼277 K) condition without precipitating HAp. This material is expected to be one of the candidates for an easy-handling and highly bioactive calcium phosphate bone paste.

抄録全体を表示

For dental composite resin (CR), mechanical strength, estheticity and flowability are required. In this study, flake-shaped glass (FSG; Glass Flake^®) was employed as the filler of CR. FSG is composed of thin glass platelets with a flat, smooth surface. FSG-filled CR (FSG/CR) showed good transparency compared to an irregularly shaped filler. The Vickers hardness of FSG/CR was increased with increasing FSG content and was comparable to that of a commercial CR at 70 wt % FSG content. The compressive strength of FSG/CR with silanized FSG was also comparable to that of the commercial CR. The flowability of uncured FSG/CR was much higher than that of the CR containing the irregularly shaped filler and that of commercial flowable CR with the same filler content. Thus, FSG will be useful as a filler of dental CR that provides estheticity, mechanical strength and flowability.

抄録全体を表示

Biological safety of Y₂O₃ nanoparticles was investigated in vitro using mouse osteoblast-like cells (MC3T3-E1). The cell numbers after culture showed that smaller particles (0.03 µm) and higher concentration of Y₂O₃ particles had the highest cytotoxicity for MC3T3-E1 cells in comparison to larger particles (1 and 0.4 µm) and lower concentration, respectively. The development of actin filament and cell proliferation were found to be inhibited in the medium containing Y₂O₃ nanoparticles. Compared to the control, cells in the medium containing Y₂O₃ nanoparticles were smaller and had few actin filaments, indicating atrophy of the cells. Apoptosis was also observed in the medium containing 0.03 µm sized Y₂O₃ particles.

抄録全体を表示

A novel automatic mill of teeth and bone has been developed for bone engineering. A human frozen-tooth and/or a human frozen-bone block were put into the Zirconium oxide (ZrO₂) ceramics vessel of the machine, and crushed for 1 min with 20 saline-ice blocks (1 × 1 × 1 cm³/block) at 12000 rpm of ZrO₂ blade. The crushed granules were demineralized completely in 2% HNO₃ solution for 20 min, and rinsed in cold saline. We named each biomaterial after the acid treatment and washing, demineralized dentin matrices (DDM), demineralized bone matrices (DBM). Five wisdom teeth (total wet volume: 10.0 g) were crushed, decalcified, and lyophilized. The distribution of freeze-dried DDM granules was fine granules (0.5–1.0 mm: 0.27 g), moderate (1.0–2.0 mm: 0.46 g), and large (2.0–5.0 mm: 0.64 g). The fine granules of human DDM or DBM were implanted into the subcutaneous tissue of 4 week-old nude mice, and their tissue-inductive properties were estimated at 4 weeks after implantation histologically. The explanted samples were demineralized, embedded in paraffin, and sectioned. The specimens were stained with hematoxylin and eosin. We confirmed that DDM induced bone and cartilage independently, and DBM induced cartilage, bone and marrow at 4 weeks in the back skin of nude mice. These results indicated that our material preparation system by the novel mill with a vessel and a blade of ZrO₂ under ice-cooling maintained the bone-inducing activity of human dentin and bone.

抄録全体を表示

Dentin matrix is well known as the most insoluble collagen in human body. We already confirmed the osteoinductive property by granules of human demineralized dentin matrix (DDM) histologically. Human DDM granules and human demineralized root-dentin (DRD) mass were prepared from adult vital teeth. The hard tissue induction by DDM alone or DRD alone was estimated at 4 weeks after implantation. The DDM alone induced bone and cartilage independently. In addition, the bioassay by recombinant human BMP-2 (5.0 µg)/DDM or BMP-2 (5.0 µg)/DRD was estimated in mouse subcutaneous or intramuscular tissues, respectively. Histological examination showed that the BMP-2/DDM induced bone and marrow, and the DDM granules were partially absorbed by new bone. The morphometric analysis demonstrated that the BMP-2/DDM showed 36.3% in the volume of bone and marrow, while the DDM alone showed 1.3% at 4 weeks. Moreover, the BMP-2/DRD also induced active bone formation on the root surface and in the pulp cavity. These results indicate that BMP-2 significantly accelerated bone formation in decalcified dentin implants. Human recycled DDM and DRD might be effective materials as osteoinductive collagenous carriers of BMP-2 for bone engineering.

抄録全体を表示

In our previous clinical study, autogenous demineralized dentin matrices (DDM) prepared from the functional vital tooth (#4E) of 12-year-old male were grafted into the bone defect, using newly developed mill and device, and then received to the host without troubles. In this study, we transplanted human tooth and dentin adjusted previously to the atrophied upper jaw. 35-year-old female presented with missing tooth (#23–#24). First, a non-functional vital tooth (#38, #41, #35) were extracted and cryopreserved immediately. One year after extraction, the tooth were crushed by newly developed auto-crush mill using ZrO₂ vessel and ZrO₂ blade for 1 minute. The crushed granules were demineralized completely in 2% HNO₃ solution, rinsed in cold distilled water and lyophilized (granule size: 0.5–2.0 mm). The bacteria-free of the DDM were confirmed by the bacteriological examination before use. We extracted the contralateral premolar (#14) for transplantation and performed the immediate root canal filling by using newly developed tooth fixing device while protecting periodontal ligament cell. The cavity for transplantation was formed by spiral and step drills. The contralateral premolar (#14) was transplanted into the modified socket (#24) and the DDM were loaded onto the places of the atrophied upper jaw. A dental X-ray photography and a CT scan of the implanted site were taken after transplantation. There were no postoperative complications at 13 months after transplantation and bone augmentation were observed by CT analysis at 4 months after transplantation. This case indicates that the preserved autogenous DDM can be used as collagenous biomaterials with osteoinductive potency.

抄録全体を表示

A novel and biocompatible hemostatic material was prepared by mixing porous spherical hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂; HAp)/alginate (AG) granules with a random copolymer of ethylene oxide and propylene oxide (EPO). Two kinds of HAp powders with different particle shapes, i.e., whisker-like HAp (w-HAp; mean long-axis length, 38.0 µm; short-axis length, 1.90 µm) and nanometer-sized HAp (n-HAp; approximate sizes, 0.03 µm × 0.05 µm) were used for the preparation of granules. The HAp–AG granules with diameters of 1.5 to 3.0 mm were prepared through (i) introduction of the spherical droplets containing 2 mass% sodium alginate and HAp particles (w-HAp or n-HAp; HAp/AG = 1.0) into 1 mol·dm⁻³ CaCl₂ solution by using a syringe, (ii) freezing of resulting spherical gels at −80°C and (iii) drying of gels at −50°C for 24 h. The water absorptions of w-HAp/AG and n-HAp/AG granules after 3 d immersion at 37.0°C were 217 mass% and 66 mass%, respectively, indicating that the porosities of the former granules were higher than those of the latter. The stanching times of blood, which were evaluated by measuring how soon the papers on the EPO gels with 60 mass% HAp (i.e., w-HAp and n-HAp)/AG granules got wet by the simulated blood that came out on top of the porous HAp cube (porosity, 70%; mean pore size, 200 µm) due to the capillary force, were estimated to be approximately 5 h.

抄録全体を表示

The effects on solubility of the substitution of monovalent metal ions (Li⁺, Na⁺, and K⁺ ions) at the Ca sites in β-tricalcium phosphate (β-TCP) were investigated by immersion of β-TCP powder doped with metal ions in saline, and the dissolution mechanisms of these samples were inferred from the results of dissolution tests and from observations of the crystal structures. β-TCP powder doped with Li⁺, Na⁺, and K⁺ ions (Li-TCP, Na-TCP, and K-TCP) had a lower solubility than pure β-TCP powder, and the solubility decreased with an increase in the amount of metal ions. This decrease in solubility can be attributed to an improvement in crystal structure stabilization upon the substitution of monovalent metal ions at the Ca(4) sites and vacancies in β-TCP, and the resultant occupancy of Ca²⁺ and metal ions at all Ca sites in the β-TCP structure. However, the dissolution behavior of Li-TCP differed from that of Na-TCP and K-TCP because the atomic arrangement between the Li(4) sites and oxygen was less stable than that between the Na(4) or K(4) sites and oxygen. In addition, the solubility of β-TCP doped with divalent metal ions was lower than that of β-TCP doped with monovalent metal ions because the structural stability of β-TCP doped with divalent metal ions was higher than that of β-TCP doped with monovalent metal ions. These results show that the solubility and dissolution mechanisms of β-TCP doped with metal ions were significantly influenced by the crystal structure stabilization and atomic arrangement of doped β-TCP.

抄録全体を表示

A self-assembled monolayer (SAM) technique was employed to produce carbonate apatite (CA) coatings onto Ti substrates after sulfonation. The Ti substrates thus treated (S-SAM-Ti) were immersed in metastable calcium phosphate solutions containing carbonate to induce precipitation of carbonate apatite on the surface. The uniformity and homogeneity of the CA layer was partly demonstrated by the XPS crater-edge-line analysis. Both calcium and phosphorus were distributed quite evenly within a layer of approximately 1000 nm.

抄録全体を表示

Microstructural changes during the heating of submicrometer-sized spherical hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂: HAp) agglomerates were examined. The starting powder was prepared by the spray pyrolysis of calcium phosphate (Ca/P ratio = 1.67) solution containing 0.0167–1.5 mol·dm⁻³ Ca(NO₃)₂, 0.0100–0.9 mol·dm⁻³ (NH₄)₂HPO₄ and concentrated HNO₃ at 600°C using an ultrasonic vibrator. The resulting powders were composed of spherical agglomerates; the agglomerate diameter was reduced with decreasing concentration of spraying solution. The mean diameter of agglomerates obtained by the spray pyrolysis of solution with the lowest concentrations, i.e., 0.0167 mol·dm⁻³ Ca(NO₃)₂ and 0.0100 mol·dm⁻³ (NH₄)₂HPO₄ (abbreviated as 0.0167/0.0100), was as small as 0.34 µm. The spherical agglomerates became hollow following a heat treatment at 800°C for 10 min. The incorporation of 0.015 mol·dm⁻³ citric acid into 0.0167/0.0100 solution contributed to the formation of hollow spherical agglomerates following spray pyrolysis. Furthermore, the heat treatment of these agglomerates at 800°C for 10 min increased the amount of pores with mean diameter of 0.2 µm, due to the burn-out of residual carbon.

抄録全体を表示

We tried to prepare magnetic TiO₂ microspheres as thermoseeds for hyperthermia of cancer by a sol–gel process from titanium tetraisopropoxide (TTIP) in a water-in-oil emulsion. The microspheres were prepared by the addition of diethanolamine (DEA) as stabilizer, methanol (CH₃OH) as dispersant and colloidal γ-Fe₂O₃ nanoparticles as origin of magnetization. The γ-Fe₂O₃ nanoparticles were prepared by an oxidation–precipitation method in FeCl₂–NaNO₃–NaOH system. The diameter of microsphere was controlled by optimizing preparation conditions, i.e., molecular ratio of reactants and stirring speed. Mono-dispersed magnetic TiO₂ microspheres 10–30 µm in diameter were sucessfully obtained by adding a certain amount of water phase with the molar ratio of TTIP/DEA/CH₃OH/H₂O = 1:1.7:7:22 into kerosene with surfactant (sorbitan monooleate/sorbitan monostearate = 3:1 in weight ratio) 16 wt % of the total amount of oil phase. They contained up to 26.7 wt % γ-Fe₂O₃ and their saturation magnetization and coercive force were 20.4 Am²/kg and 10 kA/m, respectively.

抄録全体を表示

Osteoblasts are susceptible to the surface characteristics of bioceramics and stimulation from outside the cells. The purpose of this study was to evaluate the effects of electrical polarization on surface characteristics and osteoblastic adhesion. The surface characteristics revealed that electrical polarization had no effect on surface roughness, crystallinity, and constituent elements. According to contact angle measurement, electrically polarized HA, which provides two kinds of surfaces, negatively charged HA (N-HA) and positively charged HA (P-HA), was even more hydrophilic than that of normal HA (O-HA). Morphological observations and quantitative analyses revealed that the typical adhered cells had a round shape on the O-HA but had a spindle spreading configuration on the N-HA and the P-HA 1 h after seeding. After 3 h of cultivation, the rate of the number of spread cells on the O-HA increased and approached that of the N-HA and P-HA. However, the cell areas positively stained for actin, which indicates the degree of cell spreading, were distinctly larger on the N-HA and P-HA than that on the O-HA. The number of focal adhesions per cell was also less than that on the N-HA and P-HA. To conclude, the polarization improved the wettability of the HA surface, which consequently affected osteoblastic adhesion, especially spreading.

抄録全体を表示

Radiotherapy using ceramic microparticles that act as β-emitters after neutron bombardment is attractive as a minimally invasive option for cancer treatment. Yttria (Y₂O₃) microcapsules (20–30 µm in diameter) are capable of cutting off the nutrition supply in cancer cells through an embolization effect. In the present study, Y₂O₃ microcapsules were prepared via precipitation of yttrium hydroxide from a water/oil (W/O) emulsion and a subsequent heat treatment. The emulsion was prepared by dispersing yttrium hydroxide sol in 2-ethyl-1-hexanol. Microcapsules were obtained by an addition of the emulsion in butanol via dehydration and subsequent aggregation of the yttrium hydroxide. The effects of the rotation speed and surfactant concentration on the diameter of the particles were investigated. The diameter of the microcapsules showed a tendency to decrease with increases in rotation speed during emulsion preparation or surfactant concentration in the oil phase. A high yield of the Y₂O₃ microcapsules with a diameter of 20–30 µm were obtained after a heat treatment at the optimized rotation speed and surfactant concentration. The obtained microcapsules showed high chemical durability in a simulated body environment.

抄録全体を表示

Pure titanium pieces were air-oxidized and autoclaved at 121°C for 20 min before aligning various pairs of specimens in the GRAPE^® set-up, i.e., two pieces of rectangular substrates were aligned parallel to each other with optimum gap width (spatial design). Then, they were soaked in Kokubo’s simulated body fluid (SBF) for 7 days to clarify how the autoclaving is to affect the in vitro apatite-forming ability on the substrates under the specific spatial design. Autoclaved specimens deposited a larger number of apatite particles, and showed stronger apatite X-ray diffraction than the specimen only heated in air. X-ray photoelectron spectroscopy (XPS) analysis indicated that the amount of chemically adsorbed OH and Ti–OH groups on the thermally oxidized titanium specimens increased by autoclaving. These results lead to the conclusion that the increase of Ti–OH groups and OH(s) and H₂O groups on the surface enhanced the in vitro apatite-forming ability on spatial design.

抄録全体を表示

Organic–inorganic hybrids with apatite-forming abilities in physiological environments offer possibilities for building flexible bone-bonding bioactive materials; several functional groups are known to induce apatite nucleation. Here, bioactive organic–inorganic hybrids from κ-carrageenan and λ-carrageenan containing sulfonic groups were prepared. Carrageenan hydrogels were made by cross-linking with CaCl₂. The apatite-forming abilities of each kind of carrageenan hydrogel were examined using simulated body fluid (SBF); λ-carrageenan was found to be superior to κ-carrageenan for this purpose. The former swelled significantly in aqueous conditions, releasing a large amount of Ca²⁺ ions into the SBF, contributing to rapid apatite formation.

抄録全体を表示

Calcium phosphate crystals were formed by diffusion of calcium ions into polyacrylamide (PAAm) hydrogels containing phosphate ions and succinic acid. Octacalcium phosphate (OCP) and OCP with incorporated succinate (Suc–OCP) were formed in the PAAm hydrogel. Suc–OCP was formed in the presence of excess amounts of succinic acid. The precipitates of OCP and Suc–OCP had a layered structure, composed of alternating layers of fine or irregular-shaped particles, and large spherical crystals that were the focus of this work. All of the spherical crystals were composed of many flake-like crystals. When the succinic acid concentration was ≤0.375 mol·dm⁻³ a network-like structure was observed on the spherulites, and for succinic acid concentrations ≥0.75 mol·dm⁻³ a petal-like structure was observed. These morphological changes were probably caused by adsorption of succinate ions on the (100) plane of OCP.

抄録全体を表示

To improve the bioactivity of alumina containing yttria stabilized zirconia (Al-YSZ), composite ceramics consisting of Al-YSZ and 0–10 wt % of hydroxyapatite (HA) were prepared. The XRD patterns of sintered disks with an HA content above 3 wt % had monoclinic and cubic YSZ phases and a β-tricalcium phosphate phase. Although the Vickers hardness decreased as the HA content increased, all the prepared ceramics had the same or greater hardness (1000–1300 Hv with a load of 0.49 N) compared to typical YSZ ceramics (900–1000 Hv) commonly used in clinics. Furthermore, the bonelike apatite formation ability in simulated body fluid, which was examined as a screening of bioactivity, suggested that all the surfaces of Al-YSZ ceramics blending with a small amount of HA may possess the ability to connect bone. After the accelerated low temperature degradation (LTD) test performed in normal saline at 120°C for five days using composite ceramics with the HA content of 0, 1, 3, and 10 wt %, the tetragonal zirconia phase of all composite ceramics were partially transformed into the monoclinic phase with a transition ratio of ca. 16–18 mol % (for HA = 0 and 10 wt %) and ca. 4–5 mol % (for HA = 1 and 3 wt %). Blending microsized HA powder in Al-YSZ ceramics has both positive and negative effects on the LTD durability of Al-YSZ ceramics. An advantage is that calcium ion substitution in YSZ seems to stabilize the tetragonal (or cubic) zirconia phases, but the increased surface area exposed to the solution is a disadvantage.

抄録全体を表示

This paper demonstrated aerosol deposition (AD) of α-TCP powder having isotropic particle shapes on a titanium substrate to pursue type features of AD coatings. The resulting layer was mostly flat and enough thin (less than 8 µm) and intact to show slight transparency. The layer has 3 major types of mictrostructures: flat area, flakes, and voids. The flat area was a dominant microstructure with no obvious secondary particles’ boundaries. The flat area was evaluated as a type microstructure that the theory of AD methods might promise. Accordingly, the present AD run was successful concerning the flat area. The flakes on the resulting layer were considered as a feature that is not subjected to mechanism of the AD methods, hence suggesting a criterion of source particle size.

抄録全体を表示

The purpose of this study is to evaluate the bonding strengths between dental zirconia ceramics with surface treatments and resin cements. Two types of zirconia (NANOZR and Y-TZP) and six types of dental resin cements were used in this study. All zirconia specimens were treated as follows; sandblasted with alumina, annealed at 1100°C and stored in an autoclave at 134°C for 5 hours. Half of specimens after stored in the autoclave were dried in an oven at 150°C for 3 hours. Adhesive procedure of the zirconia and resin cements was undertaken according to each manufacturer’s direction. Shear bonding strengths between zirconia and resin cements were measured. The bonding strengths stored in the autoclave were higher compared with dried after autoclave treatment. XPS revealed that hydroxide or H₂O adsorbed on the outermost layer of the zirconia after autoclave treatment. It is extrapolated that adsorbed hydroxide enhanced the bonding reaction between zirconia and resin cement.

抄録全体を表示

Alumina (Al₂O₃) is classified as bioinert materials and thus, no direct bonding to bone was observed when implanted. In the present investigation, possibility of osteoconductive Al₂O₃ was evaluated based on hydrothermal treatment in calcium chloride (CaCl₂) solution. Based on X-ray photoelectron spectroscopy measurement, Ca_2p peaks were detected on Al₂O₃ after hydrothermal treatment with 10 and 50 mmol/L CaCl₂ solution at 125°C. The Ca_2p peak intensity for Al₂O₃ treated with 50 mmol/L CaCl₂ was higher than that treated with 10 mmol/L CaCl₂. Then, in vitro osteoconductivity screening evaluation was made using simulated body fluid (SBF). After being soaked in SBF for 14 days, calcium phosphate deposition could be observed on Al₂O₃ treated with 10 and 50 mmol/L CaCl₂ solution at 125°C for 7 days whereas no deposition was observed on Al₂O₃ treated at 150 and 200°C as well as non-treated Al₂O₃. We concluded, therefore, osteoconductive Al₂O₃ could be fabricated based on the hydrothermal treatment of bioinert Al₂O₃ with CaCl₂.

抄録全体を表示

Imogolite is a naturally occurring hydrous aluminosilicate clay mineral. It has nano-tubular structure similar to that of single-walled carbon nanotubes. Imogolite is a subject of interest in the pedological field, but to date there has been no bioapplications of this substance. In this study, we investigated the cellular response of osteoblast-like cells to imogolite scaffolds. To reveal the morphology, proliferation and osteoblastic functional mineralization, we cultured human osteoblast-like cells (Saos-2) and mouse osteoblast-like cells (MC3T3-E1) on the scaffolds. The surface characteristics of the imogolite scaffold were drastically changed depending on the amount of imogolite on the dish. With the increase of imogolite concentration, the surface morphology of scaffolds changed from an island-like shape in random orientation to a self-organized fiber texture aligned in the same direction, and finally full coverage in a random orientation with plural layers. Both types of osteoblast were widely spread on the imogolite scaffolds compared to their appearance in a conventional culture dish (control). The proliferation of the two types of osteoblast showed potentially useful trends. In cellular function, there was greater mineralization of both types of osteoblast on imogolite scaffolds than that of the control. Saos-2 and MC3T3-E1 cells showed good biocompatibility in addition to the enhanced osteoblastic mineralization. Therefore, imogolite is expected to be useful as a scaffold material for bone tissue engineering.

抄録全体を表示

Reinforcement of carbonate apatite (CO₃Ap) block with CO₃Ap was studied to increase the mechanical strength of CO₃Ap block and widen applicable clinical fields. First, calcium salt was introduced to the micropores of CO₃Ap block. Then, calcium salt was carbonated to form calcite inside the micropores of CO₃Ap block by exposing CO₃Ap block to carbon dioxide at the second step. On the third step, the CO₃Ap block was immersed in Na₂HPO₄ aqueous solution. In this process, calcite inside the micropores of CO₃Ap block transformed to CO₃Ap based on the dissolution–precipitation reaction, and the newly formed CO₃Ap crystals entangled not only along the newly formed CO₃Ap but also on CO₃Ap crystals of the existing CO₃Ap block. As a result of bonding between newly formed CO₃Ap and the existing CO₃Ap block, mechanical strength of the CO₃Ap block increased approximately 1.5 times higher when compared to that before the treatment.

抄録全体を表示

Internal distribution of several nanoparticles in mice has been investigated using scanning X-ray analytical microscopy, magnetic resonance imaging and inductively coupled plasma–atomic emission spectroscopy. According dynamic laser scattering analysis, the actual particle size of obtained metal oxide was similar to that of metal particles. The estimated diameters were ca. one micrometer. After administration through the tail vein of the mice, metal particles quickly reached some organs. The distribution ratio reached a constant value and was then maintained. On the other hand, the metal oxide particles were first localized in the spleen and lung. The concentration in the lung was decreased with post-injection time. This result suggested that the particles were temporally trapped in the lung then removed to other organs. The behaviors between metal and metal oxide were quite different even when those particles had a similar actual particle size. Therefore, the distribution behavior of particles depended on the chemical species.

抄録全体を表示

This report described the effects of Ti surface modification with NaOH hydrothermal solution on adhesion strength of HA coating produced by newly developed hydrothermal (DC-HHP) method. 2 kinds of surface layer (containing anatase-type TiO₂ or not) were formed on Ti surface by immersing to 5 mol/L NaOH solution before HA coating process. Pull out tests were conducted to obtain an estimate for the adhesion properties of the HA coating. Shear strength of specimens with 5 mol/L NaOH treated at 423 K for 2 hours was estimated in the range of 4.1–5.7 MPa. The enhancement of the HA adhesive properties as well as more than three times values was achieved, in comparison to the specimens without the surface layer (approximate 1.5 MPa). It was demonstrated that 423 K hydrothermal treatment with 5 mol/l NaOH solution on Ti surfaces is significantly effective to enhancing adhesion strength of the HA coating produced by the DC-HHP method.

抄録全体を表示

Commercial products of hydroxyapatite (HAp) were easily modified to obtain partially-dissolved and precipitated HAp (PDP-HAp) ceramics by the specific dissolution–precipitation technique, which involved a stirring of 300 rpm at 298 K in 1.7–3.4 × 10⁻² N-HNO₃ solutions (50 cm³) containing Ca²⁺ and PO₄³⁻ ions or/and a supersonic treatment at 120 W and 38 kHz in the same solutions. The dissolution efficiency of porous HAp products by the supersonic treatment, which was much higher than that by stirring, drastically increased with time, depending on the porosity of ceramics and the concentration of HNO₃ solution. For even dense HAp products, enhancement of micro-pores and propagation of micro-cracks were recognized by the supersonic treatment for 20 min. After the stirring of 30 min and the subsequently supersonic treatment of 25 min, HAp nano-crystals with the composition ratio (Ca/P) of 1.64–1.66 were successfully precipitated on the pore wall surface in the macro-pores and micro-pores of the ceramics at 298 K and pH 9–10. The PDP-HAp ceramics that gave macro-pore sizes of 50–200 µm, porosities of 85–90%, and specific surface areas of 1–2 m²·g⁻¹, were implanted into the bone defects at the medial condyle of femur in Japanese white rabbits. At 8 and 16 weeks after the implantation, the PDP-HAp ceramics exhibited more excellent bio-absorption and tissue-affinity than commercial HAp products because of smooth body-fluid-permeation and effective surface nature for cell-adsorption. The PDP-HAp developed can be applied as one of bioactive scaffolds with good bio-absorption and osteoconduction characteristics for bone-regeneration therapy.

抄録全体を表示

Siloxane-containing vaterite (SiV)/poly (L-lactic acid) (PLLA) hybrids have the releasing-ability of silicate and calcium ions for gene-activation. In the present paper a new types of beads were prepared using the hybrids via an electrospraying method. The diameters of the beads were controlled in the range of ∼65 to ∼180 µm by increasing the feeding rate from 0.1 to 0.9 ml/min. Depressed areas could be observed on the surface of the beads. The SiV particles with concentration of 10 and 20 wt % in the beads were completely enclosed by the PLLA matrix. These beads showed the controlled release of silicate and calcium ions in Tris buffer solution.

抄録全体を表示

A new flow experimental system was employed in order to obtain relevant information about the capability of hydroxyapatite as a drug-delivery carrier in vitro rather than in batch systems. Using our system, we were able to estimate and monitor continuously both the adsorbed and desorbed amounts of protein and the dynamic adsorption and desorption behavior, indicating that this system is a promising technique for evaluating the drug-release properties of ceramic materials.

抄録全体を表示

The first-principles calculations are carried out to investigate the influence of the presence of divalent ions, Mg²⁺ and Sr²⁺, on the elastic properties of hydroxyapatite. The calculated elastic moduli for pure hydroxyapatite are in good agreement with the experimental values. After examination of the geometrical structures of hydroxyapatite doped with the divalent ions, the elastic properties of the models are investigated.

抄録全体を表示

Eight percent (mole fraction) yttria-stabilized zirconia (8YSZ) electrolyte samples with thicknesses ranging from 150 µm to 1.2 mm were fabricated to determine the relationship between the thickness and electrical conductivity. In principle, this range can be considered to be an extension from the macro-scale to micro-scale. X-ray diffraction (XRD), scanning electron microscopy (SEM), and alternating current complex impedance were used to characterize the samples. A nonlinear relationship between electrical conductivity and temperature was observed and explained by the “surface effect.” In addition, both the pre-exponential factor and activation energy were confirmed to be significant factors affecting electrical conductivity.

抄録全体を表示

The simultaneous control of size, morphology, and size distribution of particles is a challenging topic for powder synthesis, and one-dimensional (1-D) nanostructures have attracted increasing attention due to their specific properties. In the present study, 1-D CeO₂ was synthesized via a solvothermal treatment using Ce(NO₃)₃·6H₂O and CO(NH₂)₂ in ethanol without the use of any template or surfactant. A SEM study revealed 1-D CeO₂ fibers with perfect profile, well-dispersed state, and more uniform size distribution. The diameter of the fibers was about 50 nm and the length was 200–800 nm. An in-depth TEM observation revealed that a 1-D profile was formed by agglomeration of large numbers of nanoparticles during an early stage of the reaction. Then, the nanoparticles were gradually fused together to form a 1-D fiber with a smooth surface and a sub-microstructure, namely, the CeO₂ fibers were assembled from many sub-nanofibers. Finally, some possible evolution mechanisms for the formation of bundle-like CeO₂ nanofibers were discussed.

抄録全体を表示