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Biomedical subjects

Motohiro Uo

Publications and source records attributed to Motohiro Uo.

At least 19 recordsLinked to original sources
PubMed2007

Mechanical properties and biological behavior of carbon nanotube/polycarbosilane composites for implant materials.

Multiwalled carbon nanotube/polycarbosilane (MWCNT/PCS) composites were fabricated by the spark plasma sintering (SPS) method. The MWCNT/PCS composites consisted of MWCNTs and nanosized SiC particles pyrolyzed from PCS and possessing good mechanical properties for bone tissue repair or dental implantation. The MWCNT/PCS composites were implanted in the subcutaneous tissue and femur of rats at 1 and 4 weeks after implantation. Histological investigations showed that there was little inflammatory response in the subcutaneous tissue, and newly formed bone tissue was observed in the femur. These results indicated that the MWCNT/PCS composite had little prophlogistic effect and good osteoconductivity. The study suggested the possibility that the MWCNT/PCS composite could be a candidate bone-substitute and dental-implant material in the future.

Animals↗
PubMed2006

The degradation of the three layered nano-carbonated hydroxyapatite/collagen/PLGA composite membrane in vitro.

OBJECTIVE: The purpose of this paper was to investigate the in vitro biodegradation of a guided tissue regeneration composite membrane, nano-carbonated hydroxyapatite/collagen/poly(lactic-co-glycolic acid) (nCHAC/PLGA). Especially for periodontal therapy, the functional graded material (FGM) nCHAC/PLGA membrane was prepared that consisted of three layers with 8 wt% nCHAC + PLGA/4 wt% nCHAC + PLGA/PLGA, where one face of the membrane is porous, thereby allowing cell growth thereon and the opposite face of the membrane smooth, thereby inhibiting cell adhesion. METHODS: For evaluation, in vitro degradation specimens of nCHAC/PLGA were immersed into artificial saliva solution at 37 degrees C for 1, 2, 4, 8 and 12 weeks to detect the weight loss over the period, and set pure PLGA membrane as control to compare the degraded behaviors. pH value and calcium concentration of the residual solution were measured, and morphology change was investigated by scanning electron microscopy (SEM). RESULTS: During the experimental period in vitro, the whole shape of the membrane could be kept for 4 weeks, after that it became powder at between 8 and 12 weeks. The results demonstrated that weight loss increased continuously with a reduction in mass of 23.1% after 4 weeks and 88% after 12 week for the nCHAC/PLGA three FGM layers composite membrane. The calcium concentration in the residual solution showed a significant increase after 4 weeks, which referred to the nano-carbonated hydroxyapatite degradation. Moreover, the pH value in the solution of the nCHAC/PLGA membrane was a little higher than that of the pure PLGA membrane, which demonstrated the possible neutralization effect from nCHAC composite for the acid outcome of PLGA in the solution. The pore structure of 8 wt% nCHAC + PLGA was enlarged on the porous surface, while the nonporous surface of pure PLGA also showed a small porous structure after increased time. SIGNIFICANCE: Degradation of the composite membrane is appropriate for practical periodontal repair. Moreover, the new mineral formation on the surface of the composite membrane referred to the possible positive effect in vivo for new bone tissue regeneration.

Absorbable Implants↗
PubMed2006

Human neutrophils reaction to the biodegraded nano-hydroxyapatite/collagen and nano-hydroxyapatite/collagen/poly(L-lactic acid) composites.

The impact of biodegraded nano-hydroxyapatite/collagen (nHAC) composite and nano-hydroxyapatite/collagen/poly(L-lactic acid) (nHAC/PLA) scaffold composite on neutrophils reaction was evaluated in vitro. Neutrophils were separated from human peripheral blood of healthy subjects. The nHAC and nHAC/PLA materials were immersed in the D-Hanks' Balanced Salt Solution (D-HBSS) for 1 day, 7 days and 2, 4, 8 weeks (37 degrees C) as testing solution, which mixed with the neutrophils for 1 h. Both of the nHAC and nHAC/PLA materials were shown the same cell survival rate as blank control, but the lactate dehydrogenase (LDH) and tumor necrosis factor alpha (TNF-alpha) released from the neutrophils were increased significantly after the 2 weeks in nHAC sample. The possible reason relied on the high concentration of calcium due to the quick biodegradation of the nHAC material. Before 2 weeks, the LDH value of nHAC/PLA is higher than that of nHAC sample that corresponded to the initial PLA degradation in vitro. This study provided the biocompatibility test of neutrophils other than common methods, such as osteoblastic cells for biomimetic materials. Moreover, it demonstrated the calcium concentration stimulating effect for cytokine release from neutrophils.

Biocompatible Materials↗
PubMed2006

Effect of surface condition of dental zirconia ceramic (Denzir) on bonding.

Yttria partially stabilized zirconia (YPSZ) ceramics are suitable for dental and medical use because of their high fracture toughness and chemical durability. The purpose of this study was to examine the bonding behavior of a dental YPSZ ceramic, Denzir. After being subjected to various surface treatments, Denzir specimens were bonded to each other using an adhesive resin composite, glass ionomer, or zinc phosphate cement. Bonding strength was then determined by the shearing test. No significant differences (p>0.05) were observed between SiC- and Al2O3-blasted specimens. In all surface treatments, the shear bond strength significantly (p<0.05) increased in the order of adhesive resin composite cement > glass ionomer cement > zinc phosphate cement. Moreover, silanization with methacryloxy propyl trimethoxysilane slightly increased the bonding strength of the adhesive resin composite cement.

Dental Bonding↗
PubMed2005

Influence of length on cytotoxicity of multi-walled carbon nanotubes against human acute monocytic leukemia cell line THP-1 in vitro and subcutaneous tissue of rats in vivo.

Carbon nanotubes (CNTs) are single- or multi-cylindrical graphene structures that possess diameters of a few nanometers, while the length can be up to a few micrometers. These could have unusual toxicological properties, in that they share intermediate morphological characteristics of both fibers and nanoparticles. To date, no detailed study has been carried out to determine the effect of length on CNT cytotoxicity. In this paper, we investigated the activation of the human acute monocytic leukemia cell line THP-1 in vitro and the response in subcutaneous tissue in vivo to CNTs of different lengths. We used 220 nm and 825 nm-long CNT samples for testing, referred to as "220-CNTs" and "825-CNTs", respectively. 220-CNTs and 825-CNTs induced human monocytes in vitro, although the activity was significantly lower than that of microbial lipopeptide and lipopolysaccharide, and no activity appeared following variation in the length of CNTs. On the other hand, the degree of inflammatory response in subcutaneous tissue in rats around the 220-CNTs was slight in comparison with that around the 825-CNTs. These results indicated that the degree of inflammation around 825-CNTs was stronger than that around 220-CNTs since macrophages could envelop 220-CNTs more readily than 825-CNTs. However, no severe inflammatory response such as necrosis, degeneration or neutrophil infiltration in vivo was observed around both CNTs examined throughout the experimental period.

Animals↗
PubMed2005

Strict preparation and evaluation of water-soluble hat-stacked carbon nanofibers for biomedical application and their high biocompatibility: influence of nanofiber-surface functional groups on cytotoxicity.

Water-soluble H-CNFs modified with a carboxyl group possessed the ability to induce TNF-alpha, whereas CHAPS-treated H-CNFs possessed significantly greater activity and were also found to activate NF-kappaB reporter activity, to a significantly greater level than H-CNFs; furthermore the functional group modified or coated on the surface of H-CNFs was a significant cytotoxic factor that affected cell activation.

Carbon↗
PubMed2005

The preparation and characteristics of a carbonated hydroxyapatite/collagen composite at room temperature.

Nanocarbonated hydroxyapatite/collagen (nCHAC) composite was prepared at room temperature via biomimetic self-assembly method. X-ray diffraction (XRD), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) were performed. This composite shows the same inorganic phase of natural bone with nanosized level and low degree of crystallinity, and contains 2.8-14.7 wt % of carbonated content. TEM results confirm that the microstructure of this composite is the mineralized collagen fiber bundle like the hierarchical structure of natural bone. The diameter of a single mineralized collagen fiber is about 4 nm. Slightly different assembly units of the composite with different carbonates and collagen were demonstrated. The carbonated percentage affects the mineral crystal size and collagen fibril assembly. Because of the biomimetic component and microstructure, the use of nCHAC composite is promising for hard tissue therapy.

Bone Substitutes↗
PubMed2005

A three-layered nano-carbonated hydroxyapatite/collagen/PLGA composite membrane for guided tissue regeneration.

Functional graded materials (FGM) provided us one new concept for guided tissue regeneration (GTR) membrane design with graded component and graded structure where one face of the membrane is porous thereby allowing cell growth thereon and the opposite face of the membrane is smooth, thereby inhibiting cell adhesion in periodontal therapy. The goal of the present study was to develop a three-layered graded membrane, with one face of 8% nano-carbonated hydroxyapatite/collagen/poly(lactic-co-glycolic acid) (nCHAC/PLGA) porous membrane, the opposite face of pure PLGA non-porous membrane, the middle layer of 4% nCHAC/PLGA as the transition through layer-by-layer casting method. Then the three layers were combined well with each other with flexibility and enough high mechanical strength as membrane because the three layers all contained PLGA polymer that can be easily used for practical medical application. This high biocompatibility and osteoconductivity of this biodegraded composite membrane was enhanced by the nCHAC addition, for the same component and nano-level crystal size with natural bone tissue. The osteoblastic MC3T3-E1 cells were cultured on the three-layered composite membrane, the primary result shows the positive response compared with pure PLGA membrane.

Animals↗
PubMed2005

Biological behavior of hat-stacked carbon nanofibers in the subcutaneous tissue in rats.

The tissue response to hat-stacked carbon nanofibers (H-CNFs) was evaluated. H-CNFs were implanted in the subcutaneous tissue of rats. Histological and ultrastructural investigations were carried out by transmission electron microscopy. Although many macrophages and foreign body giant cells were seen around H-CNFs, no severe inflammatory response such as necrosis was observed. Some H-CNFs were observed in lysosomal vacuoles of phagocytes. These results showed that H-CNFs were not strong prophlogistic substances and were englobed in vivo.

Animals↗
PubMed2005

Rare earth oxide-containing fluorescent glass filler for composite resin.

In recent dental care, esthetic restorative materials such as composite resin and porcelain have been widely used and studied. However, their good esthetics makes the visual inspection of restored teeth difficult. In this study, a fluorescent glass filler containing rare earth oxides - which are well-known fluorescent materials - was prepared and used in composite resin to enhance visual inspection capability with small change in color. For example, when irradiated with near ultraviolet light, an Eu2O3-containing filler fluoresced clearly and visibly. The fluorescence intensity of the prepared composite resin increased with increase of Eu2O3 content in the glass filler and with filler/resin ratio in the resin. Despite the clear fluorescence, the effect of Eu2O3 on the color change of composite resin was quite small - even when up to 10 wt% Eu2O3 was added to the glass filler. Tb4O(7-) and Dy2O3-added fillers also showed clear fluorescence, just like Eu2O3-added filler. Therefore, fluorescent glass fillers for composite resins, resulting in small color change in the latter, were successfully prepared in this study.

Composite Resins↗
PubMed2004

Three-dimensional topographic scanning electron microscope and Raman spectroscopic analyses of the irradiation effect on teeth by Nd:YAG, Er: YAG, and CO(2) lasers.

A three-dimensional analyzer installed in a scanning electron microscope was used to evaluate the morphology and surface roughness using noncontact profilometry. Observations were carried out on the enamel and dentin surface irradiated by three different lasers: Nd:YAG (wavelength 1.06 microm), Er:YAG (2.94 microm), and CO(2) (10.6 microm). Spectroscopic analysis was done by Raman spectroscopy for nonirradiated and laser-irradiated surfaces. The lasers were applied perpendicularly to vertically sectioned and polished human extracted caries-free molars. The tooth was sectioned at each cavity for cross-section analysis after laser irradiation. Irradiation by Nd:YAG and CO(2) lasers of the enamel surface showed an opaque white color, different from dentin where the surface turned black. The Er:YAG laser induced no changes in color of the dentin. Numerous cracks associated with thermal stress were observed in the CO(2) laser-irradiated dentin. Noncontact surface profile analysis of Er:YAG laser-irradiated enamel and dentin showed the deepest cavities, and direct cross-sectional observations of them showed similar cavity outlines. The CO(2) laser-irradiated dentin had the least surface roughness. Raman spectroscopic analysis showed that fluorescence from the laser-irradiated tooth was generally greater than from nonirradiated teeth. Bands in dentin attributed to organic collagen matrix were lost after Nd:YAG and CO(2) laser irradiation, and a broad peak due to amorphous carbon appeared. The Er:YAG laser-irradiated dentin showed no sign of a carbon band and had more suitable results for dental ablation. Noncontact surface profile analysis was effective to evaluate the structural change in the tooth in the microarea of study after laser irradiation.

Humans↗
PubMed2004

Microparticle formation and its mechanism in single and double emulsion solvent evaporation.

The emulsification is the first step of the emulsification solvent evaporation method and has been extensively investigated. On the contrary the second step, the solvent transport out from the emulsion droplets that determine the particle morphology and with great influence on the microparticles encapsulation and release behavior has been scarcely studied. This study investigates the mechanism of the solvent elimination from the emulsion droplets and its influence on the particle morphology, encapsulation and release behavior. Usually, the solvent is highly volatile that makes the solvent elimination process very fast thus difficult to observe. In order to observe in detail the microparticle formation, the initial emulsion was monitored by optical microscope under controlled solvent evaporation conditions. The results from the optical microscopic observations corroborated with laser diffractometry analysis showed that in single emulsion formulations, spherical microparticles are formed by accelerated solvent elimination due to the combined effects of high solvent volatility and polymer precipitation. The solvent expulsion accompanied by important shrinkage generates on the microparticle surface a thin layer of nanoparticles attested by scanning electron microscopy and laser diffractometry. During the intense solvent elimination, the encapsulated substance is drained, affecting the loading efficiency. Furthermore, it will concentrate towards the microparticle surface contributing to the initial burst release. In double emulsion formulations, microparticles with different morphologies are generated due to the presence of the aqueous-phase microdroplets inside the emulsion droplet. During the solvent elimination, these microdroplets generally coalesce under the pressure of the precipitating polymer. Depending mainly on the polymer concentration and emulsification energies, the final microparticles will be a mixture of honeycomb, capsule or plain structure. During the shrinkage due to the incompressibility of the inner microdroplets, the precipitating polymer wall around them may break forming holes through which the encapsulated substance is partly expulsed. Through these holes, the encapsulated substance is further partitioning with the external aqueous phase during solvent evaporation and contributes to the initial burst release during the application.

Capsules↗
PubMed2004

Quantitative analysis of biologic specimens by X-ray scanning analytic microscopy.

X-ray scanning analytic microscopy (XSAM) can be used to visualize the elemental distribution in biologic specimens. In this article, the authors prepared standard specimens for XSAM and performed quantitative analysis of various elements dissolved in soft tissues. Two different types of standard specimens were prepared. Methylmethacrylate (MMA) resin-based standard specimens were prepared with organic compounds of elements for low-concentration standards and lithium borate glass-based standard specimens were prepared with oxides of elements for higher concentration standards. Using these standard specimens, the P and Ca concentrations in normal rat tissue and dissolved Ni, Fe, and Ni concentrations around metal-implanted tissues were quantitatively analyzed. The estimated concentrations of dissolved Fe, Cu, and Ni from the implants were 1000, 40, and 20 mM, respectively. From the concentration levels causing inflammation around these implants, the high toxicity for soft tissue of Ni and Cu at low concentrations, for example, 10 mM, was confirmed. The toxicity of Cu was estimated as next to that of Ni. In contrast, Fe had low toxicity despite high concentrations of dissolved Fe of as much as 1000 mM. In this article, it was possible to estimate the nonmetallic elements and low-concentration metallic elements dispersed in soft tissue by XSAM.

Animals↗
PubMed2004

Rapid analysis of metallic dental restorations using X-ray scanning analytical microscopy.

OBJECTIVES: X-ray scanning analytical microscopy (XSAM) makes it possible to analyze small specimens in air without pretreatment. The purpose of this study was to utilize XSAM for the rapid analysis of metallic dental restorations by microsampling. METHODS: Six different dental alloys were scratched with brand-new silicone points to obtain metal on the silicone point for compositional analysis. The fluorescent spectra of XSAM were measured to determine the metal attached to the specimen. RESULTS: The major components of the six dental metals, except for palladium, were clearly detected. The identification of palladium was difficult since the fluorescent X-ray of palladium is quite close to that of rhodium, which is the source metal of the incident X-rays. However, with a slight modification of XSAM, palladium was also identified. The total time required for sampling and analysis with XSAM was less than 10 min. The amount of the attached metal was estimated to be less than 30 microg. This amount of sampling does not damage metal restorations. SIGNIFICANCE: XSAM analysis using the microsampling technique is useful for the rapid analysis of metallic restorations.

Dental Alloys↗
PubMed2004

Distortion of laser welded titanium plates.

The distortion of laser welded titanium plates was assessed for different operating conditions of the laser welding device, and with different welding parameters (in terms of weld point and prewelding). In this study, Nd : YAG laser welding device was used to join the titanium plates. The results showed that distortion increased stepwise after each welding point along the welding zone (one-side welding), but decreased consecutively as the welding proceeded on the second side of the weld (two-side welding). In the case of one-side welding, the dependence of distortion on current and spot diameter presented maxima--due to changes in the welding pool characteristics. For two-side weld the same parameters exercised little influence on its distortion recovery, due to the effect of solidified weld pools from the first side. Current and spot diameter determined the weld pool, which in turn regulated distortion based on shrinkage. Four-point prewelding significantly decreased the final distortion for both one- and two-side welds. Alternating two-side welding of prewelded assembly showed lower distortion than a classic two-side weld.

Dental Soldering↗
PubMed2003

Tissue response to a newly developed calcium phosphate cement containing succinic acid and carboxymethyl-chitin.

We developed a new calcium phosphate cement containing succinic acid and carboxymethyl-chitin in the liquid component. In this study, the biocompatibility and osteoconductivity of this new cement were investigated. After mixing, cement in putty form was implanted immediately between the periosteum and parietal bone and in the subcutaneous tissues of rats. In control cement, distilled water was used instead of the liquid component. In addition to histological evaluations, analyses with X-ray diffraction and Fourier transform infrared were performed for the subcutaneously implanted cements. Histological examination showed slight inflammation around the new cement on the bone and in the subcutaneous tissue at 1 week after surgery. At 2 weeks, the cement was partially bound to the parietal bone. The extent of the surface of the new cement directly in contact with the bone increased with time, and most of the undersurface of the new cement bound to the host parietal bone by 8 weeks. Analysis by X-ray diffraction showed that the new cement in the subcutaneous tissue was transformed into hydroxyapatite by 8 weeks. These results indicate that this new calcium phosphate cement is useful as a bone substitute material.

Absorbable Implants↗
PubMed2003

Cytotoxicity and bonding property of dental ceramics.

OBJECTIVES: Yttria partially stabilized zirconia (YPSZ) ceramic is suitable for dental and medical use because of its high fracture toughness and chemical durability. The purpose of this study was to estimate the cytotoxicity and bonding property of zirconia ceramic compared to other dental ceramics. METHODS: Eight commercial dental ceramics including Denzir (YPSZ) are used in this cytotoxicity test. The human gingival fibroblast (GF) cells were cultured using extraction solutions of ceramics. The cytotoxicity was estimated by two different methods. The bonding strength of Denzir was compared to Empress2 using zinc phosphate, glass ionomer, and adhesive resin cements. A brass plate was prepared with drilled tapered holes and ceramic specimens were prepared to fit the holes and bonded. The bonding strength was estimated by the punching test. RESULTS: No significant (p>0.05) cytotoxicity was observed in all ceramic extractions. The two evaluation methods showed no significant differences. Denzir and Empress2 showed similar bonding strength with zinc phosphate or glass ionomer cement bonding. For both Empress2 and Denzir the glass ionomer cement showed significantly (p<0.001) higher bonding strength compared to the zinc phosphate cement. Empress2 showed significantly higher bonding strength with adhesive resin cement. However, the Denzir showed lower bonding strength with adhesive resin cement. SIGNIFICANCE: No ceramic extractions showed any evidence of cytotoxicity. Therefore, the low in vitro cytotoxicity of ceramic extractions including Denzir was confirmed. Denzir showed a similar bonding strength to Empress2 with zinc phosphate or glass ionomer cement bonding with this testing method and lower bonding strength with adhesive resin cement than with Empress2.

Cells, Cultured↗