bluuebunny/crossref_metadata_2025 huggingface dataset:
In Vitro Aging Test for Bioactive PMMA-Based Bone Cement Using Simulated Body Fluid
Authors: Cho S.B. , Kim Sang Bae , Cho Keon Joon , Kim Ill Yong , Ohtsuki Chikara , Kamitakahara Masanobu
Published: March 2009

Novel PMMA-based bone cement using bioactive sol-gel derived CaO-SiO2 powder in order to induce bioactivity as well as to increase its mechanical property. The novel PMMA-based bone cements formed apatite on their surfaces in Simulated Body Fluid(SBF). In the present study, a change in mechanical property of the cement was evaluated using SBF. Before soaking in SBF, its compressive strength showed 80.6±2.1MPa. After soaking in SBF for 2 weeks, 8weeks and 9 weeks,
its compressive strength were changed to 83.6±1.6MPa, 87.3±2.4MPa and 85.6±1.8MPa, respectively. It is clear that from the above result, there is no decrease in its compressive strength within 9 weeks soaking in SBF. That it hardly decreases in compressive strength of 7P3S bone cement in SBF is due to the relative small amount of gel powder or its spherical shape and monosize. Therefore, the newly developed PMMA-based cement can bond to the living bone and
also be effectively used as bioactive bone cement without decrease in mechanical property.
Biomechanical and Histomorphometric Study of the Bone-Screw Interface of Calcium Pyrophosphate Coated Titanium Screws
Authors: Lee Jae Hyup , Ryu Hyun Seung , Lee Dong Soo , Hong Kug Sun , Chang Bong-Soon , Lee Choon Ki
Published: March 2009

The purpose of this study is to compare the osseointegration of calcium
pyrophosphate(CPP) coated screws with uncoated screws. CPP coating was prepared and coated by dipping method. CPP coated and uncoated screws were inserted into the mongrel dogs. The insertion torques, radiographs, histology, histomorphometric analysis, and extraction torques were evaluated at
2, 4, and 8 weeks after surgery. The insertion torque was not different between CPP coated and uncoated screws. The extraction torques of CPP coated screws at 2, 4, and 8 weeks(5.45±2.05, 7.62±1.51 and 6.60±2.80 cNM) were significantly higher than their insertion torques(2.74±1.13, 2.98±0.70, and 2.18±1.34 cNM)(p<0.0001, <0.0001 and 0.0005 respectively) and significantly higher than the extraction torques of uncoated screws(1.14±0.470, 2.57±1.36, and 3.18 ±0.499 cNM). The percentages of direct bone-screw contact of CPP coated screws were statistically higher than those of uncoated screws at 2, 4, and 8 weeks. These results suggest that CPP coating may improve the clinical
results by allowing early motion exercises and early weight bearing.
Ultra-Structural Study of the Laminin-Apatite Composite Layer Formed on Ethylene-Vinyl Alcohol Copolymer by a Biomimetic Process
Authors: Oyane Ayako , Uchida Masaki , Ishihara Yousuke , Ito Atsuo
Published: March 2009

Mechanism of formation of a laminin-apatite composite layer on the surface of an
ethylene-vinyl alcohol copolymer (EVOH) using a liquid phase coating process was investigated by transmission electron microscopy (TEM). In this coating process, an EVOH substrate is alternately dipped in calcium and phosphate solutions, and then immersed in a laminin-containing calcium phosphate (LCP) solution. From the results obtained by the present study, formation of the
laminin-apatite composite layer on EVOH is likely to proceed via the following events. By the alternate dipping process, particulate amorphous calcium phosphate, which is a precursor of apatite, was deposited onto the EVOH surface. When the specimen was subsequently immersed in the LCP solution, the amorphous calcium phosphate on the specimen transformed itself into needle-like apatite crystal, and then grew into a layer. During this process, laminin molecules contained in the
LCP solution were incorporated into a matrix of the apatite crystals to produce a laminin-apatite composite layer on the EVOH surface.
The Influence of Sintering Temperature on Mechanical and Microstructural Properties of Bovine Hydroxyapatite
Authors: Göller G. , Oktar Faik Nuzhet , Agathopoulos Simeon , Tulyaganov D.U. , Ferreira José Maria F. , Kayali E.S. , Peker Ismail
Published: March 2009

The influence of sintering temperature on densification, microstructure and the
mechanical properties of bovine hydroxyapatite (BHA), produced by a calcination method, was investigated. Densification and mechanical properties increased over increasing sintering temperature in the range between 1000°C and 1300°C, and there are evidences of optimum sintering temperature at 1200°C. The measured mechanical properties indicate sintered BHA-bodies as interesting biomaterials for further investigation in biomedical applications.
The Effect of Post-Treatment on the Mechanical Behavior of Plasma Sprayed HA Coating
Authors: Cao Y. , Zhang Bo , Wang Li Ping , Lin Qiang , Li Xu Dong , Bao C.Y. , Chen Ji Yong , Yang Bang Cheng , Yang L. , Zhang Xing Dong
Published: March 2009

Plasma-sprayed hydroxyapatite coating on metal substrate has been prepared, two kinds of post-treatment methods have been used: (1) Heating in air at 650°C for 30 min, (2) Heating in water vapor at 125°C, 0.15Mpa for 6 hours. XRD showed that the nanocrystals of HA coating increased after water vapor treated. The interfacial tensiles strength between HA and the substrate were 45.0±1.82MPa, 39.1±1.27MPa and 30.3±1.61MPa for as-received coatings, water vapor
treated coatings and heated in air coatings respectively. After 3 months implant in dogs limbs, the push-out strength between implants and bone were 11.27±2.71 MPa, 11.63±3.11MPa, 23.92± 2.01MPa and 18.8±1.82 MPa for pure Ti implants, as-received coating implants, water vapor treated implants and heated in air implants respectively. The results showed that the water vapor post treated HA coating have better mechanical behavior in vitro and in vivo.
Adsorption Isotherm of Sodium Ampicillin onto Dense and Porous Hydroxyapatite
Authors: Queiroz A.C. , Santos José D. , Monteiro F.J.
Published: March 2009

The adsorption behaviour of sodium ampicillin to dense and porous hydroxyapatite as been extensively studied through the obtention of an adsorption isotherm. This isotherm was produced at body temperature, and a wide range of antibiotic solutions was used. The adsorption behaviour was measured by UV spectroscopy. The shape of the isotherm for the two forms of the material, dense and porous, indicates that the adsorption behaviour of the antibiotic seems to be different; however, this is due to the adsorption taking place within the pores of the porous material, thus showing a larger amount of antibiotic adsorbed.
Using X-Ray Micro-CT Imaging to Monitor Dissolution of Macroporous Bioactive Glass Scaffolds
Authors: Jones Julian R. , Milroy Georgina E. , Cameron Ruth , Bonfield William , Hench Larry L.
Published: March 2009

Bioactive glass scaffolds with interconnected macroporous networks have been
developed by foaming sol-gel derived bioactive glass of the 70S30C (70 mol% SiO2, 30 mol% CaO) composition. The effect of sintering temperature on the dissolution of the scaffolds in simulated body fluid (SBF) was investigated in 3D using x-ray micro-computer tomography (micro CT) and inductive coupled plasma (ICP) analysis. Micro-CT is non-destructive and allows observation of specific parts of the scaffold at various stages of degradation. However, data analysis is complex at present. Percentage porosity data obtained by micro-CT was compared to physical data and pore size distributions obtained from mercury intrusion porosimetry were compared to the interconnected pore diameters observed from the micro CT images.
Nanoscale Morphology of Apatite Precipitated onto Synthetic Hydroxyapatite from Simulated Body Fluid
Authors: Vandiver Jennifer , Patel Nelesh , Bonfield William , Ortiz Christine
Published: March 2009

Dense, polycrystalline, synthetic hydroxyapatite (HA) was incubated for 36 days in modified simulated body fluid (SBF) with increased HCO3
- and reduced Cl- ion concentrations (27 and 120 mM, respectively) closer to actual blood plasma than typical SBF. The resulting precipitated apatite layer was characterized by X-ray photoelectron spectroscopy (XPS) and contact angle measurements and found to be nonstoichiometric, calcium deficient (Ca/P~1.06),
non-carbonate containing, and of intermediate hydrophilicity (advancing contact angle, qa=76.5±1.3°). The nanoscale surface topography of the SBF-incubated HA sample was imaged by tapping mode atomic force microscopy (TMAFM), observed to be ≤100 nm in thickness, and composed of three distinct morphologies. These topographically distinct regions were localized within individual grains and facets of the initial HA surface and included: hemispherical, globular structures (maximum lateral dimension, d=44.7±12.7 nm, peak-tovalley height, h=3.6±2.7 nm); elongated, needle-like structures (minimum lateral dimension, w=31.0±8.5 nm, d=104.4±31.1 nm, h=5.0±3.2 nm), and regions of larger, irregularly shaped
structures that were relatively smooth (d=504.9±219.1 nm, h=104.0±51.7 nm).
Accelerated Formation of Bone-Like Apatite on Biodegradable Polymer Substrates
Authors: Chen Yi Zhi , Mak Arthur F.T. , Wang Min
Published: March 2009

Using an acellular simulated body fluid (SBF), bone-like apatite can be formed on a variety of biomaterials, bioactive or bioinert, after these materials have undergone appropriate treatment(s). This biomimetic apatite-forming process is now applied to tissue engineering scaffolds in an attempt to make the scaffolds osteoconductive. In the current investigation, to form bone-like apatite on polymers such as poly(L-lactic acid) (PLLA) and poly(glycolic acid) (PGA) which degrade fast in aqueous environment, a solution (5SBF) of five times the ion concentrations of SBF was used so that an accelerated apatite formation could be achieved on PLLA and PGA. It was shown that indeed apatite could be formed on PLLA and PGA in 5SBF within 24 hours and that the apatite formed in 5SBF was similar in morphology and composition to that formed in the classical biomimetic process employing SBF or 2SBF. Results obtained in this investigation are very useful for producing osteoconductive scaffolds for bone tissue engineering.
Behavior of MC3T3-E1 Osteoblast-Like Cells Cultured on a Glass Substrate with Different Surface Roughness
Authors: Saito Takao , Hayashi Hikoshiro , Uoe K. , Kizuki Takashi , Teraoka Kay , Kato Katsuya , Yokogawa Yoshiyuki
Published: March 2009

Our experiments of mouse osteoblast-like MC3T3-E1 cells cultured on a glass substrate showed that as surface roughness of a substrate increased, cell proliferation, cell differentiation and subsequent mineralization were reduced.
Attachment of Blood Cells onto ZrO2 and SiO2-Containing Glass
Authors: Valério Patricia , Agathopoulos Simeon , Calado A.J. , Leite M. Fatima , Goes Alfredo
Published: March 2009

Samples of zirconia and a bioinert SiO2-containing glass with different surface roughness were immersed into human whole blood for different settling times to investigate the adhesion and attachment of blood cells onto these materials. The cell/material interface was directly observed by scanning electron microscopy (SEM). The results indicate that the blood cells preserved their physiology and attaching capability regardless the type of material, surface roughness, and settling
time. The SEM images strongly indicate the normal function of adhesion proteins.
Multi-Scale Structure of the Pinctada Mother of Pearl: Demonstration of a Continuous and Oriented Organic Framework in a Natural Ceramic
Authors: Rousseau Marthe , Bourrat Xavier , Stempflé Philippe , Brendlé Marcel , Lopez Evelyne
Published: March 2009

Sheet nacre is a promising natural bioceramic, which consists on the internal lustrous “mother of pearl” layer of many molluscan shells, e.g. Pinctada, our model. The aim of this work is to study the structure of the flat polygonal tablets of nacre, in order to understand the multi-scale organization of this composite material and the role of the organic template during the growth of the biocrystal.
We studied the organic matrix, in situ with techniques such as darkfield transmission
electronic microscopy (TEM) on small cross-sections of nacre of Pinctada maxima, or intermittent-contact atomic force microscopy coupled with phase imaging on samples of nacre of Pinctada margaritifera polished parallel to the surface of the tablets. In this study, we demonstrate the continuity of the organic framework and the crystallographic orientation in the biocrystal at 2 relevant levels : nano- and micro-scale.
Organic-Inorganic Hybrids of Hydroxyapatite with Chitosan
Authors: Im K.H. , Park Ji Ho , Kim Kyoung Nam , Kim Kwang Mahn , Choi Seong Ho , Kim Chong Kwan , Lee Yong Keun
Published: March 2009

In tissue engineering, a scaffold helps determine 3-dimensional morphology, increases cell survival, provides initial mechanical stability, supports tissue ingrowth, aids in the formation of tissue structure. Chitosan is the partially deacetylated form of chitin that can be extracted from crustacean. It degrades in the body to non-harmful and non-toxic compounds and has been used in various fields
such as nutrition, metal recovery and biomaterials. Hydroxyapatite, a major inorganic component of bone, has been used extensively for biomedical implant applications and bone regeneration due to its bioactive, biodegradable and osteoconductive properties. The application, however, of hydroxyapatite is limited due to own brittleness. Since the natural bone is a composite mainly consisted of organic collagen and inorganic hydroxyapatite, many efforts have been made to modify hydroxyapatite by polymers. In this study, organic/inorganic hybrids were fabricated solid-liquid phase separation and a subsequent freeze-drying process. The microstructure, mechanical properties, and bioactivity of the scaffolds with various contents of hydroxyapatite were studied. The structure of the scaffolds prepared was macroporous and interconnected. The compressive mechanical properties such as compressive modulus and yield strength were improved according to the increase of hydroxyapatite contents mixed with chitosan. After 7 days of sample immersion in a simulated body fluid, for scaffolds containing hydroxyapatite, numerous bonelike apatites were formed on the surfaces of the pore walls. This study suggests that desirable pore structure, mechanical properties, and bioactivity of the hybrid scaffolds might be achieved through controlling the ratio of hydroxyapatite and chitosan.
Starch-Bioactive Glass Composite Microparticles: Bioactivity and Cellular Activity
Authors: Silva Gabriela A. , Coutinho Olga P. , Reis Rui L.
Published: March 2009

In the present work we describe the synthesis of starch-based/BG 45S5 particles and their in vitro bioactivity behaviour by means of immersion in a simulated body fluid. The composite particles have shown to form a layer of Ca-P at their surface, whose nature was confirmed by chemical and morphological analysis.
In order to evaluate the ability of these particles to be used as carriers for cell culture, undifferentiated rat cells were selected and parameters like cell adhesion, proliferation and expression of osteoblastic markers, were evaluated. The starch-based micro-particles have shown to support cellular activity, allowing cells to attach, proliferate and express specific markers while cultured in the particles surface. The final goal is to be able to use these particles as carriers for cells and simultaneously as in-situ forming constructs for tissue engineering and regenerative medicine applications.
In Vivo Characterisation of a Novel Hydrophilic Composite for Total Intervertebral Disc Substitution
Authors: Damien Elsie , Causa F. , Ambrosio L. , Revell Peter A.
Published: March 2009

Intervertebral disc (IVD) damage due to degeneration, trauma or inflammation is the main cause for lower back pain leading to morbidity and loss of function of the spinal column. Until recently the state of the art treatment for degenerative disc disease (DDD) was arthrodesis. Developments in vertebral arthroplasty enable degenerated disc to be replaced with prosthetic IVD devices while maintaining motion at the affected part. The ability of the intervertebral device to support the in vivo loading environment is critical for the clinical success of such devices. However, such properties are depended on the location and structure of IVD, as the mechanical properties of IVD change locally [1]. The objective of this study was to evaluate the in vivo tissue compatibility of a novel composite, made with poly 2-hydroxyethyl methacrylate (pHEMA), poly ε-caprolactone (PCL) and
poly ethylene terephthalate (PET) in an animal model. In vivo qualitative and quantitative results at 6 weeks post intraosseous implantation in rabbit femur revealed that this hydrogel, in contact with bone tissue, showed no tissue damage at the implant-bone interface. This novel composite disc prosthetic material is biocompatible as bone growth was observed into the implant and there was no
evidence of toxicity to bone or inflammatory responses at the peri-implant tissue.
Preparation of Porous Poly(Lactic Acid)/Hydroxyapatite Microspheres Intended for Injectable Bone Substitutes
Authors: Nagata Fukue , Miyajima Tatsuya , Teraoka Kay , Yokogawa Yoshiyuki
Published: March 2009

Porous biodegradable microspheres were successfully obtained by an improvement single step and surfactant-free emulsion solvent evaporation method. The organic phase composed of PLA and dichloromethane was stirred in aqueous phase including Ca2+ ions to yield oil in water emulsion. During emulsification, stirring rate was increased so as to produce the W/O/W emulsion that results in microspheres with internal pores. The interface of internal water/oil was stable in W/O/W emulsion, which was explained that the bond between Ca2+ ions and carboxyl group of poly(lactic acid) would be stabilized the internal water/oil interface. Adding PO4
3- aqueous solution prompted to precipitate low crystallized hydroxyapatite on the external oil/water interface, and the precipitated hydroxyapatite would stabilizied microspheres formation. The resulting microspheres were approximately 100-500 µm with internal spherical pores of 10-200 µm in diameter. The porous
biodegradable microspheres were expected to be utilized as injectable bone substitutes that allow bone ingrowth and bone regeneration.
In Vivo Evaluation of Nano-HA/PDLLA Composite
Authors: Xiao Yu Mei , Fan Hong Song , Wu Yao , Xu Jin Rui , Tan Y. , Lin Xiao Yan , Li Xu Dong , Zhang Xing Dong
Published: March 2009

The purpose of this study was to evaluate the behavior of nano-hydroxyapatite/
poly(D,L)lactide (n-HA/PDLLA) composite in vivo. The composite rods containing about 40wt% n-HA and control HA rods with a diameter of 2mm and a length of 6mm were implanted into the femora of 16 New Zealand rabbits. Composite wafers with a diameter of 5mm and a thickness of 1mm were implanted into the dorsal subcutis of 18 Wistar Albino rats. After definite intervals, the histological analysis was completed by light microscopy and the degradation behavior was observed by scanning electron microscopy. The histological analysis showed no obvious difference between n-HA /PDLLA composite and pure HA that had good biocompatibility and osteoconductivity. SEM analysis of the surface and cross section of the samples showed that the degradation of the composite started from surface, then into the inner gradually and formed multiple pores at surface.
The pore size and porosity gradually increased along with time and a porous network may be formed.
In Vivo Behavior of Calcium Phosphate Glasses with Controlled Solubility
Authors: Navarro Melba , Sanzana E.S. , Planell Josep A. , Ginebra M.P. , Torres P.A.
Published: March 2009

Resorbable calcium phosphate glasses offer interesting solutions in the biomedical field, as bone cavity fillers, drug delivery systems, biodegradable reinforcing phase in the case of composites for bone fixation devices and tissue engineering scaffolds. In this work, two different glass formulations in the systems 44.5CaO-44.5P2O5-(11-X)Na2O-XTiO2 (X=0or 5) have been elaborated. It is known that the incorporation or TiO2 into the vitreous system reduces considerably
the solubility of the glasses. To study the material solubility effect on the in vivo response, glass particles of the two formulations were implanted in rabbits. Results showed that both glasses elicited a similar biological response and good biocompatibility. The percentage of new bone formation in the glasses was comparable to that obtained for the autologous bone (control) after 12 weeks of implantation. The materials showed to have an osteoconductive potential. Finally, this
study showed that in spite of the solubility difference of the studied glasses, there were no significant differences in the in vivo response.
Highly Orientated Calcification in Newly Formed Bones on Negatively Charged Hydroxyapatite Electrets
Authors: Nakamura Satoshi , Kobayashi Takayuki , Yamashita Kimihiro
Published: March 2009

Large negative charges induced by electrical polarization on hydroxyapatite (HA)
ceramics has been demonstrated to enhance their osteoconductivities. The newly formed bones in the vicinities of the negatively charged surfaces were investigated in the views of crystallography and histology. The newly formed bone layers accompanied by mono-layered osteoblastic cells showed 4 perfect extinction positions in a 360° rotation, parallel and perpendicular to the HA surfaces by the
optically polarizing images. The observation revealed that the newly formed bone layers directly bonding to the N-surface were consisted of the well-crystallized and highly orientated HA. Therefore, it was presumed that the enhanced osteobonding by negative surface charges was ascribed to the activation of myeloid cells and the intensified attraction of the HA nuclei by the electrostatic force.
ATZ – A New Material with a High Potential in Joint Replacement
Authors: Begand Sabine , Glien Wilfried , Oberbach Thomas
Published: March 2009

The present study has been aimed to combine the advantages of the two single-phase materials, Al2O3 and ZrO2 while avoiding their disadvantages, by producing a mixed ceramic. Within a study of an ATZ ceramic we tested the influence of aging by a hydrothermal treatment on the strength, phase composition and surface properties. We found that the hydrothermal treatment of the ATZ ceramic did not significantly influence these parameters, unlike those of a single-phase
ZrO2 ceramic.
Organic-Inorganic Solution Technique for Fabrication of Porous CaO-SiO2 Based Powders
Authors: Lee Sang Jin , Lee Chung Hyo , Chun S.Y.
Published: March 2009

Soft and porous CaO-SiO2 powders (CaSiO3, Ca2SiO4, Ca3SiO5) were fabricated by organic-inorganic solution technique. Calcium nitrate and Ludox SK silica sol were dissolved in D.I. water and then 5 wt% polyvinyl alcohol solution was added as a polymeric carrier. The metal cations were dispersed well in solution and a homogeneous polymeric network was formed. The organic-inorganic precursor gels were turned to porous powder having volume expansion through an explosive oxidation reaction during calcination process. The polyvinyl alcohol content and heating rate were affected on the explosive reaction behavior. It may be speculated that the reaction between oxygen and unstable calcium cations resulted in the vigorous exothermic reaction and simultaneously the reaction made extensive void, which is accompanied with volume expansion in the powder structure, by the thermal decomposition in a moment of organic substance, polyvinyl alcohol. The porous powders were crystallized at relatively lower temperatures, and the crystalline development was dependent on the polymer content.
Reaction Bonded SiC Hot Gas Filter Using Si-Melt Infiltration Techniques
Authors: Hwang Sung Sic , Park Sang Whan , Han Jun Hyun , Kim T.W.
Published: March 2009

In this study, the reaction-bonded SiC (RBSC) hot gas filter was newly developed using Si melt infiltration technique. Si melt was infiltrated into the green body through the carbon source coated surface of SiC powder forming strong neck phases between SiC powders. The maximum flexural strength of porous RBSC support at room temperature and at 900 oC were about 80 MPa and 63 MPa, respectively, which were much higher than those of commercially available porous
clay-bonded SiC with similar pore size and porosity.
Effect of Microstructure on Dielectric Properties of Si3N4 at Microwave Frequency
Authors: Park Min Kyu , Kim Ha Neul , Lee Kee Sung , Baek Seung Su , Kang Eul Son , Kim Do Kyung , Baek Yong Kee
Published: March 2009

Silicon nitride (Si3N4) has been researched intensively because of superior mechanical properties up to high temperature. The mechanical properties of Si3N4 are strongly related to microstructure. The microstructure control of silicon nitride is well known to be a key issue for tailoring the mechanical properties of structural ceramics. This work was performed to reveal the effect of microstructure on dielectric properties at microwave frequency. Three starting powders were
used fine, course a-Si3N4 and b-Si3N4. Sintering additives, 5 wt.% Y2O3, 2 wt.% Al2O3 and 1 wt.% MgO were mixed with each starting powder. Si3N4 ceramic with different b/a phase specimen were obtained by hot pressing. The post-resonator method was used for the measurement of dielectric properties, dielectric constant (e′) and dielectric loss (tand), at microwave frequency range. Silicon
nitride ceramics show dielectric constant of 8.1 – 8.6 and dielectric loss 1.1 x 10-3 – 5.6 x 10-3. The effect of grain size and the role of phase on microwave dielectric properties are discussed.
Fabrication of Si3N4 Micro-Components by a Combined Microfabrication Process
Authors: Li Jing Feng , Jin Song Zhe , Li Yong
Published: March 2009

Si-based high-temperature ceramics are attractive materials for power
microelectromechanical systems (power MEMS), such as microscale gas turbines, micro-combustors and micro-reactors. This presentation introduces a novel process for the microfabrication of Si3N4 ceramics, which mainly consists of pre-sintering of Si powder compacts, micromachining of pre-sintered Si preforms and reaction sintering of the micromachined Si preforms. The present process has its high potential for Si3N4 3-dimensional microfabrication because it combines the
machinablity of pre-sintered Si powder compacts and near-net shaping characteristic of S3N4 reaction sintering. Si3N4 micro-components such as micro nozzle arrays and micro-rotor were fabricated by using the present process.
Indentation Induced Deformation and Crack Behavior of β-SiC Irradiated at High Temperature
Authors: Park Kyeon Hwan , Hinoki Tatsuya , Kohyama Akira
Published: March 2009

Irradiation damage produced by neutrons or energetic particles lead to changes of
physical- and mechanical-properties of SiC. Radiation hardening and fracture toughness changing of SiC were clarified by indentation method previously. However, the mechanism studies have received little alteration. The purpose of this study is to improve the understanding of the mechanisms of mechanical property changes under irradiation. In this paper, the microstructural observation beneath
and near an indentation will be used to infer mechanisms of radiation hardening and toughening. Indenting polycrystalline SiC creates deformation and cracking in the plastically deformed region. In the case of irradiated SiC, however, small-sized deformation zone was observed below contact indent, which resulted in the restricted size of residual impression. Additionally, the indentation cracks showed complex propagation behaviors such as deflecting, branching and microcracking.
Tumor Targeting of Plasmid DNA by Dextran Conjugation Based on Metal Coordination
Authors: Hosseinkhani H. , Aoyama T. , Ogawa O. , Tabata Yasuhiko
Published: March 2009

Tumor targeting of plasmid DNA was achieved through the conjugation of dextran
derivative with chelate residue based on metal coordination. Spermine (Sm) was chemically introduced to the hydroxyl groups of dextran to obtain dextran-Sm derivative. A negative zeta potential of plasmid DNA became almost 0 mV by the Zn2+-coordinated conjugation with the dextran-Sm When the dextran-Sm-plasmid DNA conjugate with Zn2+ coordination was intravenously injected to mice subcutaneously bearing Meth-AR-1 fibrosarcoma, the dextran- Sm-plasmid DNA conjugate significantly enhanced the level of gene expression in the tumor, in contrast to free plasmid DNA..
Proliferation and Differentiation of Human Stromal Cells Derived from Fat Tissue on Different Culture Substrates
Authors: Inoue Sachiko , Tabata Yasuhiko
Published: March 2009

The objective of this study is to investigate the proliferation and differentiation of stromal cells derived from human fat tissues cultured on substrates with different surface properties. In addition, the similar investigation was performed for the cells proliferated in different concentrations of basic fibroblast growth factor (bFGF). The culture substrates include several polymer films with different water wettabilities, glass or a cell culture plate, and that coated with collagen type I or IV, gelatin, and bFGF. The proliferation profiles of cells were influenced by the type of culture substrates and the growth factor concentration. A larger number of cells proliferated was observed for substrates with the water wettability around 80o, while the cell number was significantly larger for every protein-coated substrate. The rate of cell proliferation became maximum in a bFGF concentration of 1,000 ng/mL. The bFGF concentration used for cell proliferation affected the differentiation profile of cells proliferated. The stromal cells proliferated in 1 ng/mL bFGF were osteogenically differentiated to the strongest and fastest extent among those in
other growth factor doses. The alkaline phosphatase (ALP) activity of cells increased with the increased cell number although the activity per cells was indentical, irrespective of the substrates type. The strongest adipogenic differentiation was observed for cells proliferated in 1,000 ng/mL bFGF and the differentiation induction was maintained for a long time period. No clear dependence
of the cell number on adipogenesis was observed. For chondrogenic differentiation, the bFGF concentration had no influence on the glycosaminoglycans (GAG) amount. These findings indicate that the proliferation and differentiation of human fat tissue-derived stromal cells are influenced by the culture substrate and the concentration of bFGF used for proliferation.
The Study of Collagen-HA Composite with Incorporated BMP as Bone Tissue Engineering Scaffold
Authors: Liu L.R. , Zhang L.H. , Wang F.J. , Zhang Q.Q.
Published: March 2009

Collagen-HA scaffolds were prepared by a phase-separation technique, cross-linked by formaldehyde or carbodiimide(EDC)/N-hydroxysuccinimide(NHS), which is also used to covalently attach chondroitin sulfate(CS) to the scaffold. BMP was incorporated into the scaffold by adsorption. The scaffolds were characterized by SEM and ESCA. Rat mesenchymal stem cell(MSCs) was seeded into the scaffold and cultured to form a cell/scaffold construct. The ectopic osteoinduction of the scaffolds were evaluated in vivo. The results show that the scaffolds are porous with three-dimensionality, have good cell compatibility and osteoinduction. Attachment of CS can improve the adhesion and differentiation of cells.
Immobilization of Albumin and Heparin on the Surface of Ti-O Films for Improving Blood Compatibility
Authors: Jing Feng Juan , Huang Nan , Chen Jun Ying , Leng Yong Xiang , Sun H.
Published: March 2009

Aminopropyltriethoxysilane (APTE) was covalently interacted with hydroxyl on the
surface of Ti-O films prepared by magnetron sputtering, and albumin and heparin were immobilized on the APTE-coated surface with addition of 1-ethyl-3- (3-dimethyl aminopropyl) carbodiimide (EDC) as cross-link agent. X-ray photoelectron spectroscopy (XPS) was used to investigate the modified surface. Contact angle results indicate that there was an increase in the contact angle to the
surface of APTE-coated Ti-O films, and a decrease in the contact angle to the surface of albuminand heparin-immobilized surfaces. Blood platelet adhesion in vitro was improved significantly after immobilization of albumin and heparin on Ti-O films. Endothelial cell (EC) culture tests showed that EC could grow on the surface of Ti-O films immobilized with albumin and heparin, but the growth and proliferation behavior of endothelial cells was not as good as on naked Ti-O films. This
investigation showed that the surface of bio-inert inorganic materials immobilized with biological molecules is feasible and effective for improving the blood compatibility.
Study of Bone Marrow Derived Stem Cells and Gene Therapy for Engineering of Cardiovascular Grafts
Authors: Zhang Jun , Zhang Ying , Duan Ya Jun , Ou Lai Liang , Yu Yao Ting , Kong Deling
Published: March 2009

Recent study shows that endothelial progenitor cells (EPCs) and gene therapy technologies are effective strategies in the inhibition of stenosis and thrombus formation and improving the patency rate of the vascular graft in vivo. In this study, rat EPCs were cultured from bone marrow, and plated in fibronectin-coated plates with EBM-2 medium. Bone marrow mesenchymal stem cells (MSCs) were cultured with alpha minimum essential medium ( -MEM). After two weeks, EPCs
were immunohistochemically characterized using antibodies specific for endothelial cells. Retroviral vectors pMSCV-eNOS, pMSCV-tPA, pMSCV-LacZ and pMCSV-GFP were constructed. Retroviral particles were produced using packaging cell line 293T cells. Gene transfer was carried out by exposing cells to virus solution for 6 hours in the presence of 8µg/ml polybrene. For constructing vessels, MSCs and EPCs were seeded on fibronectin coated ePTFE graft in tissue culture condition for 2-4 weeks. The attachment and growth of cells were analyzed with scanning
electron microscopy (SEM). Our data showed that the EPCs expressed VEGF, Lectin BS-1, RECA-1, indicating they are endothelial lineage. The concentrated retroviral particles showed many folds higher transduction efficiency to NIH 3T3 cells than the commercial reagent Fugene. SEM data showed dense attachment of MSCs on the graft surface. MSCs/EPCs co-culture gave much better cell coverage on the graft than culture of EPCs alone.
The Antithrombogenecity of Silk Fibroin Films Blending with Citric Acid and PVA
Authors: Li Jing Hua , Cao Chuan Bao , Ma Xilan , Tang Yin , Zhu He Sun
Published: March 2009

The citric acid (CA) was added to the silk fibroin and Polyvinyl Alcohol (PVA) copolymer system. The blending 4% PVA was for improving the mechanical properties of the silk fibroin films. Citric acid amount varies from 0.5% to 2% of weight. The antithrombogenecity was characterized by in vitro clot time of prothrombin time (PT), the Activated partial thromboplastin time (APTT) and thrombin time (TT). The mechanical properties of the blending films were measured and the tensile strength and breaking elongation of films reached to 25.3MPa and 102%. The anticoagulant property results indicated that APTT and TT prolonged significantly, but PT has no effective change. We discussed the relationship between the structure and properties and proposed an anticoagulant mechanism.
Immortalization of Bone Marrow Mesenchymal Stem Cells from Inbred Pig for Regenerative Medicine
Authors: Liu Jin , Lu Xiao Feng , Wan Lin , Lu Bing , Li Sheng Fu , Zeng Yang-zhi , Lu Yan Rong , Bu Hong , Li You Ping , Cheng Jing Qiu
Published: March 2009

The aim of this experiment is to investigate whether MSCs from Banna Minipig
Inbred Line (BMI) could be immortalized by introducing SV40 large T antigen gene. MSCs were isolated from BMI and transfected with pSV3neo plasmid. Normal BMI-MSCs would apoptosis and senescence during proliferation while its population doubling (PD) number exceeded 20. However, SV40-transfected cells were immortal. As same as that of normal BMI-MSCs, transfected MSCs were positive for stem cell markers and negative for differentiated osteoblast specific marker. After
cultured in osteogenesis supplement media, cbfa1 and calcium deposit on stimulated cells were enhanced obviously. There were no data to prove the tumorigenicity potential of the immortalized cells. Furthermore, histological analysis demonstrated that bone formation was initiated in the pores of HA/TCP implants loaded immortalized BMI-MSCs 7 weeks postimplantation. BMI-MSCs were immortalized by introducing SV40 large T antigen into the cells and still kept the stem cell characters
and might be used as seeding cells for tissue engineering as well as stable test cells for biocompatibility of bone biomaterials.
Preparation of Gelatin Grafted with Lactic Acid Oligomers
Authors: Takahashi Kazuhiro , Takamoto Tomoaki , Tabata Yasuhiko
Published: March 2009

The objective of this study is to synthesize gelatins grafted with lactic acid oligomer
(LAo) and lactic acid oligomer-poly(ethylene glycol)-lactic acid oligomer (LAo-PEG-LAo) triblock copolymers and to examine their gelation behavior. The grafting ratio of LAo-grafted gelatins could be changed by the feed ratio of LAo to the amino groups of gelatin for grafting reaction, while triblock copolymers with different molecular weights of LAo were prepared. The turbidity of LAo-grafted gelatin solution increased with the increased grafting ratio, although the turbidity increase was suppressed by adding guanidine hydrochloride in a dose-dependent manner. The
turbidity of LAo-grafted gelatin solution further enhanced by mixing with the solution of triblock copolymers, while the enhanced extent increased with an increase in the LAo molecular weight. A mechanically firm hydrogel was formed by mixing the LAo-grafted gelatin and triblock copolymer at the higher solution concentrations, while the compression strength of the hydrogel became higher as the grafting ratio increased. No hydrogel formation was observed in the presence of guanidine hydrochloride.
Synthesis and Antithrombogenicity Assessment of Tetramethylpyrazine-Capped Poly(Ethylene Glycol)
Authors: Cui Dong Mei , Wang Song , Xia Cheng Jian , Zhu He Sun
Published: March 2009

Tetramethylpyrazine(TMPZ) is an active ingredient of a Chinese herbal medicine Chuanxiong (Liqusticum wallichii Franchat). In order to enhance its stability and delivery in vivo TMPZ-capped poly(ethylene glycol) conjugate was designed and synthesized efficiently by the condensation reaction of 2-cardoxyl-3, 5, 6-trimethylpyrazine (TMPZCOOH) with PEG(M=2000) in the presence of dicyclohexylcarbodiimide (DCCI). The TMPZ-PEG conjugate obtained was then purified by gel filtration chromatography (SephadexG-15 column,1.6×100cm; eluent: distilled water) and characterized by FTIR, UV spectra. FTIR (KBr): 2868cm-1(CH2), 1718cm-1(C=O), 1455cm-1 (-C=N-), 1113cm-1(O-CH2-CH2). The degree of end-capping of TMPZ per PEG molecules was estimated to be 87% from UV absorbance at 294nm. The anticoagulant activity of the conjugate was evaluated by in vitro coagulation time test. The result showed that the activated partial thromboplastin time (APTT) of the TMPZ-PEG conjugate is nearly equal to that of blank plasma in our experiment conditions, this behavior is similar to that of TMPZ. But TMPZCOOH, one of the main metabolic products of TMPZ in vivo, exhibited more potent anticoagulant activity than TMPZ and TMPZ-PEG, its APTT is even larger than the maximum clotting time set by the instrument. It is also found that APTT of the conjugate increased as the time of the sample stayed in water bath at 37°C. This is probably because the ester bond between TMPZCOOH and PEG hydrolyzed during the stay time and released the free TMPZCOOH.
Biodegradable Polyamides Containing Amino Acid Residues: A Chemoenzymatic Synthesis
Authors: Fan Yu Jiang , Chen Guo Ping , Tanaka M. , Tateishi Tetsuya
Published: March 2009

Polyamides containing amino acid residues were synthesized through a chemoenzymatic route. At first, monomers containing amino acid esters at both ends were prepared from amino acid esters and bifunctional acid chlorides through a Scotten-Baumann reaction under organic condition. Diamine was used as bifunctional nucleophilic reagent to aminolysis the amino acid ester bonds of these monomers under protease catalysts, leading to the polycondensation to form the desired polyamides containing amino acid residues. Spectra characterizations confirmed the structure of obtained polyamides. The factors that influence the polymerization, including the type of enzymes, the amount of enzymes, and the water contents in the solvent, were also discussed. It is expected that the obtained polyamides have the potential for biomaterial applications.
Hydrothermal Preparation of Porous Hydroxyapatite with Tailored Crystal Surface
Authors: Iuga Alin , Kawachi Giichiro , Yamasaki Nakamichi , Toda M. , Fujimori Hirotaka , Goto Seishi
Published: March 2009

Porous sheets of hydroxyapatite (Ca10(PO)4(OH)2; HA) with about 50 µm to 1 mm in thickness and porous HA granules of about 50 µm to 1 mm in size with tailored crystal surface were prepared by the hydrothermal vapor exposure method at the temperatures above 105 °C under saturated vapor pressure of pure water. Porous HA sheets with about 75 % porosity prepared at 120 °C were composed of rod-shaped crystals of about 30 µm in length. Porous HA granules prepared at 160 °C were also composed of rod-shaped crystals of about 20 µm in length with the mean aspect ratio of 30. These crystals were elongated along the c-axis. Rod-shaped HA crystals were locked together to make micro-pores of about 0.1 µm in size. Both of materials were nonstoichiometric HA with calcium deficient composition. These materials must have the advantage of adsorptive activity, because they had large specific crystal surface and much micro-pores.
Bioactive NiTi Implants Used for Bone Repairing Applications
Authors: Cui Zhen Duo , Yang Xian Jin , Zhu S.L.
Published: March 2009

In this study, chemical methods were used to treat NiTi for the purpose of preparing
bioactive NiTi implants. The surface of the bioactive NiTi alloy was investigated by XRD and ESEM. The biocompatibility and bioactivity of the bioactive NiTi samples were evaluated by in vivo implantation experiments. The results show that a Ca-P layer composed mainly of hydroxyapatite (HA) with a trace amount of other apatites and a Ca/P ratio of 1.59 covers the surface of the bioactive NiTi alloy. In vivo tests show that osteoblasts actively proliferated on the bioactive NiTi implants after 6 weeks implantation. A large amount of new bone directly in contact with the host bone was observed after 13 weeks implantation. These revealed the excellent biocompatibility and bioactivity of the prepared bioactive NiTi alloy.
Wear of UHMWPE against Zirconia/Alumina Composite
Authors: Lee Kwon Yong , Kim Hwan , Kim Dae Joon , Lee Myung Hyun , Seo Won Seon
Published: March 2009

The sliding wear behavior of ultra high molecular weight polyethylene (UHMWPE) was examined on a novel low temperature degradation-free zirconia/alumina composite material and on the conventional ceramics (alumina and zirconia) used for a femoral head in total hip joint replacement. The wear of UHMWPE pins against these ceramic disks was evaluated by performing linear reciprocal sliding and repeat pass rotational sliding tests for one million cycles in a bovine serum. The weight loss of polyethylene against the novel low temperature degradation-free zirconia/alumina composite disks was much less than conventional ceramics for all tests. The mean
weight loss of the polyethylene pins was more in the linear reciprocal sliding test than in the repeat pass rotational sliding test for all kinds of disk materials. Neither the coherent transfer film nor the surface damage was observed on the surface of the novel zirconia/alumina composite disks during the test. In conclusion, the novel zirconia/alumina composite leads the least wear of polyethylene among the tested ceramics and demonstrates the potential as the alternative materials for femoral
head in total hip joint replacement.
The Friction and Wear Behaviors of Dental Porcelains with Different Surface Strengthening Techniques
Authors: Yu H.Y. , Zhou Zhong Rong , He L.H.
Published: March 2009

The friction and wear behavior of dental feldspathic ceramics, treated distinctively by three routine surface strengthening techniques (auto-glazing, ion exchange and polishing), were investigated by cyclic sliding against pure titanium ball on a modified fretting friction and wear test rig under imitating oral enviorment. The wear scars of the samples were characterized with 3-D con focused laser-scanning microscope. The wear depths were analyzed statistically and the element concentrations of Ti, Al and Si on the scar before and after surface treatments were determined with energy dispersion spectrometry. The correlations between the wear behaviors and micro hardness or toughness were also compared. The results show the present routine surface strengthening methods have little effects on the friction coefficient of dental porcelain, but play an role in improving the wear behavior of ceramics at the early stage of sliding cycles. The effect of surface ion exchange is better than that of auto-glazing or polishing. The friction and wear behavior of dental ceramics depend on the material itself especially after the surface-strengthening layer disappeared. Abrasive wear, adhesion and micro cracking characterize the wear mechanism of dental feldspathic ceramics after the surface-strengthening treatments.
Refolding and Purification of rhBMP-2 Expressed as Inclusion Bodies in E.COLI with Hydroxyapatite Chromatography
Authors: Yao Shaohua , Zhang Ling Li , Cheng Steven Y. , Zhang Xing Dong
Published: March 2009

The objective of this study was to develop an efficient method for the production of
bioactive bone morphogenetic protein 2 (BMP-2). A recombinant plasmid encoding mature human BMP-2 was transferred and expressed at a high level in E.coli. Most of the aimed proteins existed in inclusion bodies. The non-active recombinant human BMP-2 (rhBMP-2) monomer in inclusion bodies was refolded and simultaneously purified using hydroxyapatite (HA) chromatography. After
oxidization of the monomer, the rhBMP-2 dimmer showed biological activity by the induction of alkaline phosphate activity in C2C12 cells. The refolding yield was about 30% and the purity was about 90% just by one chromatography process.
Periodic Structure of Blaze Grating in Abalone Shell
Authors: Wang J. , Peng X.J. , Yuan Chun Wei
Published: March 2009

Periodic structures, such as photonic crystals and gratings, offer the ability to control light propagation and produce structural colors (not produced by pigments). Structural colors are quite widespread in nature, such as in opals and some animals. The abalone shells attract much attention due to its fracture resistant. In present work, we report on the microstructure of the surface area in where the iridescence color appears found in abalone shell shows a groove structure of blaze grating. The scanning electron microscopy (SEM) images of its iridescent layer show layers of platelets. The abalone shell has a statistically regular arranged tile structure. This specific tile structure serves as a two-dimensional grating to cause the iridescence phenomenon. Unlike opals, the iridescence color of the abalone shells is not directional due to the two-dimensional arrangement of the reflection grating structure and the convex shape of the tiles.