Preparation and Characterization of β-TCP/CS Scaffolds by Freeze-extraction and Freeze-gelation

The freeze-extraction and freeze-gelation methods were used to prepare highly porous β-TCP/CS scaffolds with different β-TCP/CS ratio.In these methods,the suspending mixture of β-TCP and chitosan was frozen,the frozen mixture was immersed in a non-solvent(0.05mol/L NaOH/ehanol aqueous) bath to allow the exchange between solvent(acetic-acid aqueous) and non-solvent at a temperature lower than the freezing point of the acetic-acid.Then,the β-TCP/CS scaffolds were formed and dried at room temperature.Scanning ...     

Fabrication of Porous Scaffolds Using NaHCO3 Particulates as the Porogen Material

A new method of fabricating porous polymer scaffolds was developed, using sodium hydrogen carbonate particulates as the porogen to foam. The pore structure of polymer scaffolds can easily be manipulated by controlling the size and weight fraction of sodium hydrogen carbonate particulates. The scaffolds are highly porous with a porosity greater than 90% and with a larger pore size ranging from 100-400μm, and are well distributed with the interconnected and open pore wall structure which is necessary for tissue engineering. We investigated the effect of the porosity of scaffolds, the pore size of scaffolds and material of polymer on the mechanical properties of scaffolds. The scaffolds fabricated by the method have more big pores than those by the convenient method of salt leaching.     

Effects of β-TCP ceramics on osteoblast cellular proliferating, mineralization and osteocalcin expression

After co-cultrured osteoblast with β-TCP ceramics, the cellular proliferating, mineralization and osteocalcin expression were studied. MTT assay showed that β-TCP ceramics had no affect on cellular proliferating. Laser scanning confocal detection showed that β-TCP ceramics could increase the mineralization level of osteoblast. Furthermore, RT-PCR showed that β-TCP could increase the expression level of osteocalcin. Those results indicate β-TCP ceramics had perfect biocompatibility and increased the mineralization of osteoblast to accelerate osteogenesis by means of affecting the expression of genes involving in osteogeneticprocess.     

Effects of β-TCP Ceramics on Intracellular Ca~(2+) Concentration,Mineralization of Osteoblast and Protein Structure

β-TCP, as one of calcium phosphates ceramics, exerts perfect biocompatibility and osteoconductivity, and is clinically used as a bone graft substitute for decades. Consequently, the effects of β-TCP ceramics on intracellular Ca2+ concentration, mineralization of osteoblast and BSA protein structure were studied. Results showed that β-TCP could increase the intracelluar Ca2+ concentration and mineralization of osteoblast, indicating that β-TCP ceramics could take part in the organic metabolism and the degrad...     

改进粒子沥滤法制备PLA径向梯度多孔支架

采用溶剂浇铸／真空挥发／粒子沥滤法制备了径向梯度聚乳酸（PLA）多孔支架材料,对支架孔的形貌、孔径、孔隙率、压缩模量及致孔剂和溶剂残留情况等进行了研究．SEM测试结果表明,支架的孔分布均匀,孔径呈现梯度变化,且孔与孔间具有良好的相互连通性．梯度多孔支架各层的平均孔径在（175±30）-（341±23）μm之间;孔隙率均大于（87．9±1．2）％,结果表明：径向各层的孔径、孔隙率可通过致孔剂用量和粒径进行控制．压缩模量在（1．96±0．24）-（2．40±0．1）MPa之间,致孔剂用量和致孔剂粒径的变化均会导致支架力学性能的变化;TGA测试结果证实支架不存在致孔剂和溶剂残留．     

Evaluation of a novel bioabsorbable PRGD/PDLLA/<Emphasis Type="Italic">β</Emphasis>-TCP/NGF composites in repair of peripheral nerves

Peripheral nerve regeneration using a novel nerve conduit (PRGD/PDLLA/β TCP/NGF) was evaluated, which was made of RGD peptide modified poly{(lactic acid)-co-[(glycolic acid)-alt-(L-lysine)]} (PRGD), poly(d,l-lactic acid) (PDLLA) and β-tricalcium phosphate (β-TCP). And the effectiveness was compared with that of PRGD/PDLLA/β-TCP, PDLLA and autograft in terms of nerve regeneration across a gap. Both of biodegradablity and cell-biocompatibility of the novel nerve conduit were evaluated in vitro. The results show that PRGD/PDLLA/β-TCP/NGF composite materials have better biodegradation properties and cell affinity than PDLLA, and could promote the RSC96 Schwann cells adhesion, proliferation and growth on the surface of materials. PRGD/PDLLA/β-TCP/NGF composite conduit was significantly superior to that of the PDLLA conduit in histological and axon morphologic index. PRGD/PDLLA/β-TCP/NGF conduit is more beneficial to nerve regeneration than PDLLA conduit. The biodegradable PDLLA/PRGD/β-TCP/NGF conduit has a good biocompatibility with rats tissue and it could effectively promote the nerve regeneration after bridging sciatic nerve defect of rats, the effect is as good as that of the autograft nerve, significantly superior to the PRGD/PDLLA/β-TCP conduit and PDLLA conduit. PDLLA/PRGD/β-TCP/NGF composite conduit is a potential ideal conduit. Funded by 973 State Key Fundamental Research and Development (No. G2005CB623905)     

Effect of β-TCP Ceramic on the Total Protein of Osteoblasts

The osteoblast with the β-TCP ceramic was co-cultured. Scanning electron microscopy shows the cells adhered onto β-TCP ceramic surface and grew better, proving the β-TCP ceramic has a biocompatible property. The Coomassie brilliant blue G-250 stain shows that the total protein in the experimental groups was highly increased compared with the control group （p〈0.05）. Flow-cytometric analysis shows that β-TCP ceramic could promote the osteoblast transform from the G0/G1 phase to S phase. Those all demonstrate the product of the degradation of the β-TCP ceramic may take part in the protein metabolism of osteoblast.     

Preparation and Degradation Characteristics of Poly （d,l-lactide） Composite Films

PDLLA/CHI/β-TCP/NGF composite films were prepared by a solvent evaporation method. The degradation characteristics of the poly （d, l-lactide） composite films were studied in vitro and in vivo. The acidity produced by poly （d, l-lactide） materials was not obvious. Adding chitosan and β-TCP can relieve the acidity problem and improve strength performance of films. The NGF has influences on the degradation characteristics of films. It is verified that PDLLA/CHI/β-TCP/NGF composite films prepared by solvent evaporation method have excellent degradation characteristics. It can be used as a perfect biomaterial for repairing nerve injuries.     

Laboratory investigation on mechanisms of stress wave propagations in porous media

A number of porous models having the similar statistical characteristics of pores and physical properties with natural sandstones have been produced using reactive powder concrete (RPC) and polystyrenes. Spit-Hopkinson-Pressure -Bar tests and CT scans have been carried out on the models with the various porosities to probe the performance of wave propagations and the responses of pores and the matrix during wave propagations. It is shown that porosities significantly influence wave propagations. For an identical impact strain rate, the greater the porosity is, the larger the amplitude of the reflected wave appears, the more the peak in the reflected wave presents, and the smaller the amplitude of the transmitted wave turns out. A single peak emerges in the reflected wave when the porosity falls down to 5%. The larger the impact strain rate, the much remarkable the phenomena. The energy-dissipated ratio of porous models, i.e., W _J /W _I , linearly increases with the increment of porosities. The ratio is sensitive to the impact strain rate. Differences in the performance of wave propagations and energy dissipation result from the varied mechanisms that pores response to impacts. For the porosity less than 10%, the mechanism appears to be a process fracturing the matrix to generate new surfaces or pores. Energy has primarily been dissipated in creating new surfaces or pores. No apparent pore deformation takes place. The impact strain rate takes little effect on pore geometry. For the porosity of 15% or more, the mechanism works depending on the impact strain rate. When a low impact strain rate applies, the mechanism still appears to crack the matrix to generate surfaces or pores, but the amount is lower as compared to the case with a low porosity. If a large impact stain rate applies, the mechanism combines both fracturing the matrix and deforming the pores, with the deforming pores predominating. The vast majority of energy has been dissipated to deform pores. Only high porosity and impact strain rate can bring significant deformation to the pores. The proposed eccentricity of pores is capable of characterizing the geometry of pores and its change during wave propagations. Supported by the Natural Sciences & Engineering Research Council of Canada (PGS-D2-2006), the National Basic Research Program of China (“973” Project) (Grant No. 2002CB412705), and the New Century Excellent Talents Program of the Ministry of Education of China (NCET-05-0215)     

有机泡沫浸渍法制备多孔羟基磷灰石生物支架的研究

以聚氨酯海绵为模板,采用浸渍法合成了孔隙率可控的羟基磷灰石(hydroxyapatite, HAP)生物支架。首先自制了羟基磷灰石粉体, 并借助X射线衍射对其进行了物相组成的分析;其次,利用聚氨酯海绵自身均匀的孔隙结构,采用浸渍法制备了多孔羟基磷灰石支架。支架孔隙率的高低与浸渍次数有关, 可达45％～90％。支架的扫描电子显微镜(SEM)分析显示,多孔支架孔形状近似为圆形,尺寸400μm左右。随浸渍次数的增加,支架的抗压强度会相应增高,浸渍5次可达3。51MPa,满足临床要求。最后还对支架的生物亲和性进行了研究,结果表明制备的羟基磷灰石支架在人体环境中具有一定的生物亲和性。     

椭球颗粒体系宏细观特性的三维离散元分析

颗粒材料由大量不同形状的离散颗粒组成,其力学特性与构成颗粒体系的颗粒形状密切相关,目前关于颗粒形状对颗粒材料剪切强度的影响已有大量的物理试验或数值模拟试验研究,而非球形颗粒材料在复杂应力路径下的宏、细观力学特性认识还不够充分。本文采用离散单元法(DEM)对按一定级配生成的不同伸长率的椭球颗粒体系进行等σ₃(第三主应力)等b(中主应力比)的真三轴加载数值模拟试验,研究了椭球颗粒体系的三维宏、细观力学特性,并验证了常用三维强度准则对椭球颗粒体系的适用性。研究结果表明在三维加载路径下,不同于圆球颗粒体系宏、细观演化规律的一致性,椭球颗粒体系的宏观应力面与细观组构面演化规律不一致,宏观应力比与强接触网络组构偏值/均值比线性不为1,归因于椭球颗粒体系弱接触网络对宏观应力的贡献;椭球颗粒体系宏观体应变、细观法向接触力分布、接触数目及配位数分布等宏、细观指标与加载路径无关;随着椭球伸长率η增大,Mohr-Coulomb、Lade-Duncan、Mastsuoka-Nakai及施维成三维强度准则对φmax(峰值内摩擦角)~b关系预测准确度逐渐增大,其中Lade-Duncan准则能更好地拟合不同加载路径下椭球颗粒体系的数据点。本文的研究为提高人们对真实应力状态下椭球颗粒材料的宏、细观特性提供了一定的理论基础。     

Experimental Study on Young′s Modulus of Concrete

Ｃｏｎｃｒｅｔｅｃｏｍｐｏｎｅｎｔｉｓｗｉｄｅｌｙｕｓｅｄｉｎｉｎｄｕｓｔｒｉａｌａｎｄｃｉｖｉｌｃｏｎｓｔｒｕｃｔｉｏｎｓ .Ｙｏｕｎｇ′ｓｍｏｄｕｌｕｓｉｓａｂｏｕｔｉｔｓｂａｓｉｃｍｅｃｈａｎｉｃｓｃｈａｒａｃｔｅｒｉｓｔｉｃ ,ｗｈｉｃｈｉｓｉｎｄｉｓｐｅｎｓａｂｌｅａｎｄｉｍ ｐｏｒｔａｎｔｆｏｒｓｔｕｄｙｓｕｃｈｐｒｏｂｌｅｍｓａｓｄｅｆｏｒｍａｔｉｏｎ ,ｅｘｐｌｏｓｉｖｅｗａｖｅａｎｄｅａｒｔｈｑｕａｋｅｗａｖｅ .ＴｈｅｒｅｌａｔｉｏｎｂｅｔｗｅｅｎＹｏｕｎｇ′ｓｍｏｄｕｌｕｓａｎｄｔ…     

NaCl添加量对SF/HA复合多孔材料结构和性能的影响

采用等静压成型法制备丝素SF/羟基磷灰石HA复合多孔材料,通过对材料形态结构、密度、孔隙率、透气性及抗弯、抗压性能等的测试和分析,研究了致孔剂NaCl添加量对SF/HA复合多孔材料结构和性能的影响.结果表明,以Nacl为致孔剂能够制得SF/HA复合多孔材料,致孔效果明显,孔呈三维空间结构,当NaCl添加量达到400%～550%后,材料内孔与孔之间连通性有较显著的改善.SF/HA复合多孔材料的孔结构有利于养料和代谢物的运输交换,为细胞提供良好的生长环境,便于骨组织的长入,其生物降解性有利于骨组织的改建和塑形,具有良好的临床应用前景.     

Chitosan and <Emphasis Type="Italic">β</Emphasis>-cyclodextrin microspheres as pulmonary sustained delivery systems

Chitosan and β-cyclodextrin were used to prepare microspheres with theophylline for pulmonary delivery by spray drying method. The characteristics, mucociliotoxicity, permeation rate and drug release were studied. The drug entrapments of microspheres Ⅰ, Ⅱ and Ⅲ were from 35.70% to 21.09% and 13.33%, while yields and encapsulation efficiencies were higher than 45% and about 90% respectively. The microspheres possessed low tap densities （0.34-0.48 g/cm^3）, appropriate diameters （3.35-3.94 μm） and theoretical aerodynamics diameters （2.20-3.04 μm）. SEM images showed the microspheres were spherical with smooth or wrinkled surface surfaces. FT-IR demonstrated theophylline had formed hydrogen bonds with chitosan and fl-cyclodextrin. The microspheres could effectively reduce the ciliotoxicity and easy to penetrate the memberine. The in vitro release of the microspheres was related to the ratio of drug/polymer and microspheres Ⅱ had a prolong release, providing the release of 72.00% in 12 h. The results suggestes that chitosan/β-cyclodextrin microspheres Ⅱ are a promising carrier as sustained release for pulmonary delivery.     

Microstructural evolution during aging of Ti-5Al-5Mo-5V-1Cr-1Fe alloy

The evolution of microstructure on aging of an (α+β) titanium alloy (Ti-5Al-5Mo-5V-1Cr-1Fe) in the β and (α+β) solution-treated and quenched conditions was investigated. The presence of very fine ω phase was detected by electron diffraction for samples aged below 400 °C. The fine α aggregates are uniformly formed within β grains by nucleating at the ω particles or β/ω interfaces. At higher temperature, the formation of ω phase is avoided and the α lamellae are precipitated at the preferred site of grain boundary and then within the matrix. The highest hardness values are found when the alloys are aged at 450 °C for β condition and 350 °C for (α+β) condition. Foundation item: Project (50634030) supported by the National Natural Science Foundation of China; Project (2007DS04014) supported by the Program of Science and Technology of Shandong Province, China; Project supported by the Open Research Fund from the State Key Laboratory of Rolling and Automation, Northeastern University, China     

<Emphasis Type="Italic">In-situ</Emphasis> growth and photoluminescence of β-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> cone-like nanowires on the surface of Ga substrates

β-Ga₂O₃ cone-like nanowires have been in-situ grown on the surface of gallium grains and films by heating gallium substrates at 750–1000°C for 2 h in air. The controllable synthesis of β-Ga₂O₃ nanowires with different diameters and lengths was achieved by adjusting the heating temperature and time. The as-synthesized products were characterized by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the β-Ga₂O₃ nanowires are single crystalline with a monoclinic structure and have a controllable diameter and length in the range of 30–100 nm and 0.5–1.5 μm, respectively. A possible mechanism was also proposed to account for the formation of β-Ga₂O₃ cone-like nanowires. Photoluminescence spectra of the β-Ga₂O₃ nanowires obtained at different temperatures were measured at room temperature, and a strong blue photoluminescence with peaks at 430 and 460 nm and a weak red photoluminescence with peak at 713 nm were observed. The blue light emission intensity decreases with increasing the reaction temperature, however, the red light emission intensity hardly changes. The blue and red light emissions originate from the recombination of an electron on an oxygen vacancy with a hole on a gallium-oxygen vacancy pair and the nitrogen dopants, etc., respectively. Supported by the National Natural Science Foundation of China (Grant No. 20573072) and Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20060718010)     

Preparation and characterization of 3-dimensionally ordered macroporous SiC

Compared with the non-ordered macroporous materials, 3D long range ordered macroporous materials exhibit many advanced properties, such as the uniform pore size and the high permeability, etc. Nowadays, many kinds of 3D ordered macroporous (3DOM) materials, such as oxide ceramics[1―4], carbon[5] and polymers[6,7], have been successfully fabricated. However, the developed porous materials have some drawbacks that the porous carbon and polymer cannot be used in air at high temperatures, and o…     

Enantiomeric separation of phenylsuccinic acid by cyclodextrin-modified reversed phase high-performance liquid chromatography

The chiral separation of phenylsuccinic acid (PSA) was studied by reversed phase high-performance liquid chromatography (RP-HPLC) with cyclodextrins (CDs) as chiral mobile phase additives. The effects of types of CDs, concentration of hydroxypropyl-β-cyclodextrin (HP-β-CD), percentage of organic modifier, pH value and column temperature on enantioselective separation were investigated. The quantification property of the developed RP-HPLC method was examined. The chiral recognition mechanism of PSA was also discussed. The results show that a baseline separation of PSA enantiomers is achieved on a Lichrospher C18 column (4.6 mm (inner diameter)×250 mm, 5 μm) with HP-β-CD as chiral mobile phase additive. The capacity factors of R-PSA and S-PSA are 3.94 and 4.80, respectively. The separation factor and resolution are respectively 1.22 and 8.03. The mobile phase is a mixture of acetonitrile and deionized water (20:80, volume ratio) containing 10 mmol/L HP-β-CD and 0.05% trifluoroacetic acid (pH 2.5, adjusted with triethylamine) with a flow rate of 1.0 mL/min. The ultraviolet (UV) detector is set at 254 nm. The likely roles are inclusion interaction, induction and hydrogen bonding between HP-β-CD and PSA enantiomers. Foundation item: Project(20776038) supported by the National Natural Science Foundation of China     

Microstructure and mechanical properties of calcium phosphate cement/gelatine composite scaffold with oriented pore structure for bone tissue engineering

The macroporous calcium phosphate(CPC) cement with oriented pore structure was prepared by freeze casting. SEM observation showed that the macropores in the porous calcium phosphate cement were interconnected aligned along the ice growth direction. The porosity of the as-prepared porous CPC was measured to be 87.6% by Archimede’s principle. XRD patterns of specimens showed that poorly crystallized hydroxyapatite was the main phase present in the hydrated porous calcium phosphate cement. To improve the mechanical properties of the CPC scaffold, the 15% gelatine solution was infiltrated into the pores under vacuum and then the samples were freeze dried to form the CPC/gelatine composite scaffolds. After reinforced with gelatine, the compressive strength of CPC/gelatine composite increased to 5.12 MPa, around fifty times greater than that of the unreinforced macroporous CPC scaffold, which was only 0.1 MPa. And the toughness of the scaffold has been greatly improved via the gelatine reinforcement with a much greater fracture strain. SEM examination of the specimens indicated good bonding between the cement and gelatine. Participating the external load by the deformable gelatine, patching the defects of the CPC pores wall, and crack deflection were supposed to be the reinforcement mechanisms. In conclusion, the calcium phosphate cement/gelatine composite with oriented pore structure prepared in this work might be a potential scaffold for bone tissue engineering.     

湘鄂西地区上震旦统陡山沱组页岩微观孔隙特征及主控因素

随着中国页岩气研究的不断深入,页岩储层微观孔隙特征的研究越来越受到众多学者重视。为了深入了解湘鄂西地区上震旦统陡山沱组页岩孔隙特征,综合利用扫描电镜、氩离子抛光-场发射扫描电镜、氮气吸附/脱附试验以及核磁共振试验等对页岩孔隙特征进行定性观察和定量表征,并结合有机地球化学分析数据以及岩石矿物全岩定量分析结果,探讨页岩孔隙发育的主控因素。结果表明:湘鄂西地区上震旦统陡山沱组页岩发育6种孔隙类型,主要有粒内孔、粒间孔、黏土矿物层间孔、有机质孔隙,还可见部分黄铁矿晶间孔以及微裂缝;页岩孔径大小主要分布在2~5 nm之间,以中孔隙为主,还发育少量微孔隙和大孔隙,峰值在2~5 nm之间的孔隙是页岩孔隙体积的主要贡献者;页岩孔隙结构类型以板状孔等狭缝形孔为主,还发育部分圆筒形孔、锥形管孔等;总有机碳主要控制页岩微孔隙、中孔隙的发育,黏土矿物含量主要影响页岩中孔隙的发育,而脆性矿物含量控制页岩大孔隙的发育。