丝蛋白对磷酸钙生长及其结晶的调控

以氨气扩散法为基础,以再生丝蛋白(RSF)作为可溶性有机物对磷酸钙的生成实施调控.采用透射电镜包括选区电子衍射、扫描电镜、X-射线衍射及红外光谱等多种技术手段对所生成磷酸钙的形貌和晶型进行观察和检测.通过改变矿化时间、RSF浓度以及钙/磷离子浓度等,能够在特定的条件下可控获得具有相应形貌即球形颗粒状的无定形磷酸钙(ACP)或粘连片状的羟基磷灰石(HAP).大量的实验显示出其基本规律为,在较高钙/磷离子浓度的母液中,诱导形成ACP所需的RSF浓度也较高;而在其它相同的情况下,RSF的分子量越高,其调控产生ACP所需的浓度随之降低.同时,RSF不仅对ACP的生成具有诱导效应,而且还能起到对ACP的稳定作用.相对稳定的ACP/RSF杂化物对骨修复材料的制备而言具有非常重要的意义.     

Physico-chemical and thermochemical studies of the hydrolytic conversion of amorphous tricalcium phosphate into apatite

The conversion of amorphous tricalcium phosphate with different hydration ratio into apatite in water at 25 °C has been studied by microcalorimetry and several physical-chemical methods. The hydrolytic transformation was dominated by two strong exothermic events. A fast, relatively weak, wetting process and a very slow but strong heat release assigned to a slow internal rehydration and the crystallization of the amorphous phase into an apatite. The exothermic phenomenon related to the rehydration exceeded the crystalline transformation enthalpy. Rehydration occurred before the conversion of the amorphous phase into apatite and determined the advancement of the hydrolytic reaction. The apatitic phases formed evolved slightly with time after their formation. The crystallinity increased whereas the amount of HPO₄²⁻ ion decreased. These data allow a better understanding of the behavior of biomaterials involving amorphous phases such as hydroxyapatite plasma-sprayed coatings.     

Preparation of a biphasic calcium phosphate from Ca(H2PO4)2·H2O AND CaCO3

Sintered hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) are the two most common bio-ceramics for bone substitute. Although their composition are analogous to the constituent of human hard tissue, but some disadvantages are always exist till now, such as they need a high temperature sintering process, and this would lose the functional groups for bioactivity and closed the micro- pores without any interconnections, that hamper the body fluid transportation and angiogenesis during regeneration. Furthermore, the sintered ceramics with block and fixed size is difficult to fit non-regular defect area. In this study, the mixtures of Ca(H₂PO₄)₂·H₂O and CaCO₃ were adjusted firstly, then distilled water were introduced in wet chemical method, and a biphasic ceramic of HAp/β-TCP will be obtained after drying and sintering, then the result product that prepared by wet chemical method will be the sample in this investigation. The physical properties of result powders were characterized by DTA/TG, XRD and SEM, respectively, the particle size of two bio-ceramics that after heat treatment were found under 5 μm in SEM examination. Powder type calcium phosphate ceramics with the Ca/P molar ratio of 1.67 can be as bone cement by mixing with polymeric binder, the fine particle product of the setting cement will possess micro-pores and macro-pores that after suitable heat treatment process, and this is good for fluid transportation and tissue regeneration.     

Amorphous Calcium Phosphate Based Composites: Effect of Surfactants and Poly(ethylene oxide) on Filler and Composite Properties

The uncontrolled aggregation of amorphous calcium phosphate (ACP) particulate fillers and their uneven distribution within polymer matrices can have adverse effects on the properties of ACP composites. In this article, we assessed the influence of nonionic and anionic surfactants and poly(ethylene oxide) (PEO) introduced during the preparation of ACP on the particle size distribution and compositional properties of ACP. In addition, the mechanical strength of polymeric composites utilizing such fillers with a photo‐activated binary methacrylate resin was evaluated. Zirconia‐hybridized ACP (Zr‐ACP) filler and its corresponding composite served as controls for this study. Surfactant‐ and PEO‐ACPs had an average water content of 16.8% by mass. Introduction of the anionic surfactant reduced the median particle diameter about 45% (4.1 µm versus 7.4 µm for the Zr‐ACP control). In the presence of PEO, however, the d_m increased to 14.1 µm. There was no improvement in the biaxial flexure strength (BFS) in any of the dry composite specimens prepared with the surfactant and/or PEO‐ACPs compared to those formulated with Zr‐ACP. The BFS of wet composite specimens decreased by 50% or more after a month‐long exposure to saline solutions. Other types of surfactants and/or polymers as well as alternative surface modification protocols need to be explored for their potential to provide better dispersion of ACP into the matrix resin and better mechanical performance ACP composites.     

Synthesis and thermal characterization of copper and calcium mixed phosphates

A series of compounds with composition of Ca_1–xCu_xHPO₄, where x varied from 0.05 to 0.5 were synthesized by precipitation method. The compounds were characterized by elemental analysis, X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and thermogravimetry. The chemical stabilities of solids were investigated at several pH. Elemental analysis of copper, calcium and phosphorus are in agreement with the proposed composition. The formation of lamellar phosphates was evidenced. The stability of the set of compounds was better for samples with high copper content.     

Study of the Solubility Diagram of H3PO4-KOH-Ca(OH)2-H2O at 25°C Section CaHPO4-KOH-H2O

Study of the system CaHPO₄-KOH-H₂O at 25°C allowed determination of the precipitation fields of CaHPO₄and the apatite compounds KCaPO₄·H₂O and K₄Ca(PO₄)₂·5H₂O. The solid products were studied and identified by X-ray analysis. The water ratio is of great importance in the preparation of the starting mixture; it affects the nature of the compounds obtained after equilibrium. This revised version was published online in July 2006 with corrections to the Cover Date.     

不同结构的磷酸盐对凝胶体系中草酸钙晶体物相和相组成的影响

泌尿系结石的形成是一种病理性生物矿化过程,不同地区的结石发病率在3％～15％之间。且50％(美国)至80％(中国)的人会复发。结石中约70％以上为草酸钙(CaC2O4)结石。CaC2O4结石的形成与其热力学(过饱和度)和动力学(成核、生长和聚集)因素有关。由于结石患者尿液和正常人尿液中     

Crystal structure and properties of the new vanadyl(IV)phosphates Na2MVO(PO4)2, M=Ca and Sr

Two new complex vanadyl(IV)phosphates Na₂MVO(PO₄)₂ (M=Ca, Sr) were synthesized in evacuated quartz ampoules and investigated by means of X-ray diffraction, electron microscopy, DTA, ESR and magnetic susceptibility measurements. The crystal structure of Na₂SrVO(PO₄)₂ was solved ab initio from X-ray powder diffraction data. Both compounds are isostructural: a=10.5233(3) Å, b=6.5578(2) Å, c=10.0536(3) Å and a=10.6476(3) Å, b=6.6224(2) Å, c=10.2537(3) Å for Ca and Sr, respectively; S.G. Pnma, Z=4. The compounds have a three-dimensional structure consisting of V⁴⁺O₆ octahedra connected by PO₄ tetrahedra via five of the six vertexes forming a framework with cross-like channels. The strontium and sodium atoms are located in the channels in an ordered manner. Electron diffraction as well as high-resolution electron microscopy confirmed the structure solution. The new vanadylphosphates are Curie-Weiss paramagnets in a wide temperature range down to 2 K with θ=12 and 5 K for Ca and Sr phases, respectively.     

Feasibility of using isothermal microcalorimetry to evaluate the physical stability of amorphous nifedipine and phenobarbital

Feasibility of microcalorimetry to evaluate the physical stability of amorphous drugs was studied. Amorphous forms of nifedipine and phenobarbital were prepared by melting and subsequent cooling in a differential scanning calorimetry (DSC) sample pan, and their heats of crystallization were monitored by isothermal microcalorimetry. The time required for 10% of the amorphous drug to crystallize (t₉₀), a direct measure of the crystallization rate, could be obtained from a single microcalorimetric trace of the amorphous nifedipine or phenobarbital. The t₉₀ values were also determined by conventional storage studies in which the heat of crystallization was determined by DSC. The t₉₀ values obtained by microcalorimetry were consistent with those obtained by DSC, within experimental error, indicating that microcalorimetry is a useful method for evaluating the physical stability of amorphous drugs.     

Selective oxidation of alcohols over nickel zirconium phosphate

Nickel zirconium phosphate nanoparticles were found to function as efficient catalysts for the selec-tive oxidation of a wide range of alcohols to their corresponding ketones and aldehydes using H2O2 as an oxidizing agent and without any organic solvents, phase transfer catalysts, or additives. The steric and electronic properties of various substrates had significant influence on the reaction con-ditions required to achieve acetylation. The results showed that this method can be applied for the chemoselective oxidation of benzyl alcohols in the presence of aliphatic alcohols. The catalyst used in the current study was characterized by ICP-OES, XRD, NH3-TPD, Py-FTIR, N2 adsorp-tion-desorption, SEM and TEM. These analyses revealed that the interlayer distance in the catalyst increased from 0.75 to 0.98 nm when Ni2+ was intercalated between the layers, whereas the crystal-linity of the material was reduced. The nanocatalyst could also be recovered and reused at least seven times without any discernible decrease in its catalytic activity. This new method for the oxi-dation of alcohols has several key advantages, including mild and environmentally friendly reaction conditions, short reaction time, excellent yields and a facile work-up.     

宋代绿釉陶表面“银釉”的分析及其形成机理

银釉是古代铅釉陶瓷器表面较为常见一种病变。利用扫描电子显微镜能谱、X射线衍射、傅立叶红外光谱、光电子能谱等测试技术,分析了湖北黄冈地区出土宋代绿釉陶表面银釉的成分和结构。结果发现,银釉中富含钙(5.1%～9.2%)、磷(4.6%～9.2%)、铅(56.9%～70.5%)等元素,并有Pb10-xCax(PO4)(OH)2(x<2.7)物相存在。结合其出土前(弱酸性的土壤)埋藏环境,推测银釉应为土壤中羟磷灰石及各种磷酸化合物与釉陶表面Pb2 发生化学反应的产物。     

磷矿及磷肥中氧化钙测定方法改进

为了解决磷矿及磷肥中氧化钙酸溶不完全和消除测定过程中磷酸根、镁、铁等的干扰,对磷矿和磷肥中氧化钙的测定方法进行改进.对不同酸溶解体系选择、酸用量、加热时间、干扰掩蔽实验、pH值等条件进行实验,确定采用10 mL王水、3 mL氢氟酸分解试样,加入2 mL盐酸溶解盐类,加入10 mL糊精和5 mL三乙醇胺溶液掩蔽Mg2+、...     

Mechanochemical-hydrothermal synthesis of calcium phosphate powders with coupled magnesium and carbonate substitution

Magnesium- and carbonate-substituted calcium phosphate powders (Mg-, CO₃-CaP) with various crystallinity levels were prepared at room temperature via a heterogeneous reaction between MgCO₃/Ca(OH)₂ powders and an (NH₄)₂HPO₄ solution using the mechanochemical-hydrothermal route. X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis were performed. It was determined that the powders containing both Mg²⁺ and CO₃²⁻ ions were incorporated uniformly into an amorphous calcium phosphate phase while in contrast, the as-prepared powder free of these dopants was crystalline phase-pure, stoichiometric hydroxyapatite. Dynamic light scattering revealed that the average particle size of the room temperature Mg-, CO₃-CaP powders was in the range of 482 nm-700 nm with a specific surface area between 53 and 91 m²/g. Scanning electron microscopy confirmed that the Mg-, CO₃-CaP powders consisted of agglomerates of equiaxed, ≈20-35 nm crystals.     

电流密度对钙磷沉积层组成和结构的影响

用X射线衍射、激光拉曼光谱以及等离子体原子发射光谱等技术研究了电化学沉积钙磷陶瓷过程中 ,电流密度对电沉积层组成和结构的影响 .实验表明阴极表面得到的沉积物是几种钙磷盐组成的混合物 ,且其成份随电流密度的改变而发生较大的变化 .在电解液温度为 75℃条件下 ,当控制电流密度较低时 ,沉积层主要由CaHPO4· 2H2 O (DCPD)和Ca8H2 (PO4) 6· 5H2 O (OCP)组成 ;随着电流密度的增加 ,阴极表面逐渐生成Ca3 (PO4) 2 ·nH2 O (TCP)和Ca10 (PO4) 6(OH) 2 (HAP) .当电流密度大于 5mA/cm2 时 ,电沉积层的主要成份为羟基磷灰石 (HAP) .     

Ion association in calcium phosphate solutions at 37°C

Ion association in the system Ca(OH)₂–H₃PO₄–KCl–H₂O at 37°C has been studied potentiometrically over a range of pH from 3 to 9. The experimental conditions were optimized for the accurate determination of the association constants for the formation of the ion pairs CaH₂PO ₄ ⁺ , CaHPO₄ and CaPO ₄ ^– which were found to be 27.9±0.1, 591±2, and (1.35±0.02)×10⁶ L-mol^–1, respectively.     

焦磷酸盐-磷酸盐复合催化剂高效催化乳酸脱水制丙烯酸

利用沉淀法制得焦磷酸盐与磷酸盐在浆状态下复配制备成复合催化剂,并用于催化乳酸脱水制丙烯酸.实验发现催化剂的组成对乳酸的转化率及丙烯酸的选择性有着重要的影响,当磷酸盐/焦磷酸盐质量比在30∶70～50∶50范围内,可以获得较高的乳酸的转化率和丙烯酸的选择性.催化反应条件如反应温度,乳酸进料浓度,液空速也被详细地进行了考察.此外,考察了该复合催化剂的稳定性.当催化剂连续运行56 h后,乳酸的转化率保持在96%以上,丙烯酸的选择性也高达57%.为了进一步揭示催化剂的结构与催化性能之间的关系,利用X射线粉末衍射、热重、扫描电镜和傅立叶红外等对催化剂进行了表征.     

骨及生物材料中的纳米磷酸钙

纳米磷酸钙在自然界骨组织的形成过程中起到了关键作用。尽管骨的类型有所不同,但在其初级结构中的无机成分都是纳米磷酸钙。纳米磷酸钙结构能够给予骨良好的机械性能和生物学活性。在生物体中,无机纳米磷酸钙在有机基质的调控下能定向自组装成特定的生物矿物。体外细胞实验显示小尺寸纳米羟基磷灰石更能促进骨髓基质干细胞的增殖,而同尺寸的结晶型纳米磷酸钙则比无定形磷酸钙更能利于干细胞分化。鉴于纳米磷酸钙具有很好的生物相容性和骨诱导性,可以发展成为理想的生物材料常用于骨组织工程和生物医学。     

The Effect of Microwave Sintering on the Microstructure and Properties of Calcium Phosphate Ceramic

Despite good ability to improved biological affinity and activity of calcium phosphate (CP) ceramic to the surrounding host tissue when implanted, CP ceramic is capable to encourage direct bond with bone as their chemical compositions are similar to the mineral phase of bone. However, the low mechanical property of CP ceramic restricts use in load-bearing applications. Therefore, the primary aim of this study was to fabricate dense CP ceramic via used of microwave sintering analyze the microstructure and mechanical properties comparison to conventional ceramic sintering. The sintered specimens were characterized by their surface microstructure, density measurement and hardness test. The result demonstrated that the density and hardness values of sintered CP ceramic specimens by microwave sintering were higher than conventional sintering. The microstructures of CP ceramic microwave sintered specimens show also better microstructures (analyzed by FESEM technique), with fines grain size and the present of apatite layer growth on the surface when examined with SBF solution. It can be concluded that the microwave sintering enhanced better microstructure and mechanical properties of CP ceramic.     

离子色谱法测定磷酸氢钙中的氟化物

建立了离子色谱法测定磷酸氢钙中氟化物的方法。用本法测得的结果与化学法相符,相对标准偏差为0.65%-4.36%,回收率为99.5%-100.3%。