脂质体中生物矿化的研究进展

生物矿化是指在有机体内形成矿物的过程。以脂质体作为模板，不仅可以模拟生物矿化过程中有机基质的调控作用和生物大分子的指导作用，而且可以提供生物矿化所需的特殊隔室，使反应物富集、定位，催化矿化反应的发生。本文综述了近年来在脂质体中模拟生物矿物磷酸钙、碳酸钙和草酸钙等矿化的研究进展，并讨论了膜控制晶体生长的机理。     

单分子膜诱导下晶体生长中的晶格匹配

有机基质与无机晶体的晶格几何匹配是导致生物体内矿物有序生长并具有特殊理化性质的重要因素之一.作为模拟生物矿化的重要模板之一,Langmuir单分子膜具有独特的优势.本文综述了单分子膜诱导下CuSO4、Na2SO4、PbS、CdS、BaF2和CaF2等晶体生长过程中的晶格匹配,讨论了单分子膜亲水头基、膜的电荷性质、膜聚集态等因素对膜控晶体生长过程中晶格匹配的影响.指出了该领域所面临的问题和将来的发展方向.     

不同结构物质和有机基质对草酸钙晶体生长的促进作用

本文综述了有机大分子、小分子和有机基质对尿石矿物草酸钙(CaOxa)晶体成核、生长和聚集的促进作用.从促进物的分子结构和草酸钙晶体的晶面性质等方面讨论了不同类型促进物的作用机理.最后指出了该领域所面临的问题和将来的发展方向.     

两株嗜冷碳酸钙矿化菌对大理石表面修复效果研究

细菌诱导的矿化沉积是一种有效修复和保护石质文物的方法.为探究生物矿化法应用于寒冷地区石质文物表面的修复效果,本文在黄龙高寒钙华沉积区分离到2株具高产碳酸酐酶(CA)活性的嗜冷型细菌菌株,并在大理石试件表面进行诱导矿化沉积.采用pH计、SEM、XRD等仪器,通过对矿化沉积过程中pH值、试件表面矿化沉积变化量、试件表面矿化沉积物的晶型晶貌、试件表面吸水性与透气性、耐酸度等的测定来表征嗜冷型碳酸酐酶产生菌在大理石试件表面矿化沉积的修复效果.结果表明,无论是存活菌还是灭活菌都在大理石试件表面生成了致密的碳酸钙矿化层,均为方解石晶型,形貌受菌体调控,活菌生成的矿化层更为均一和致密,长期作用比短期作用效果更明显,具有矿化层的试件在吸水性、透气性和耐酸度上都体现出更具防腐蚀的能力.其结果可为石质文物的修复提供一定的理论依据.     

阳离子聚合物聚乙烯亚胺诱导的碳酸钙仿生矿化研究

以富含胺基的阳离子聚合物聚乙烯亚胺(PEI)为碳酸钙生长的矿化调节剂,采用气体扩散的方法,研究了不同PEI浓度以及不同矿化时间对碳酸钙形貌和晶型的影响.分别采用扫描电子显微镜(SEM)、X射线粉末衍射(XRD)、傅里叶红外光谱(FT-IR)等实验手段对所得的样品进行了表征.结果表明,在较低的聚乙烯亚胺浓度下获得空心球状的球霰石和方解石,在较高浓度下,为方解石的聚集体,并随着矿化时间的延长,方解石的形貌趋于规则.     

Deinococcus Radiodurans表面氨基修饰对钙锶生物矿化自组装的影响

研究中通过表面基团屏蔽探索耐辐射奇球菌表面氨基对钙锶生物矿化及其自组装过程的影响.结果表明:(1)在Deinococcus Radiodurans作用下,体系倾向于形成文石晶型;(2)屏蔽氨基后,氨基对方解石晶体的抑制作用消失,[Ca2+]高时诱导晶体从文石转变为方解石,[Sr2+]高时诱导晶体产生空壳结构;(3)在D.Radiodurans作用下,文石晶体的生长属于经典的棒-哑铃-球自组装模型;屏蔽氨基后,文石晶体的生长为球壳和哑铃空壳的空壳自组装过程.综上所述,耐辐射奇球菌表面氨基能促进晶型的转换,控制晶体的自组装.本研究结果可为阐释微生物诱导生物矿化自组装过程提供参考.     

蒙脱石基生物纳米复合功能材料及应用研究

生物纳米复合功能材料的理论与应用研究已成为关注焦点,是生命科学与材料科学前沿交叉方向.粘土矿物是一类天然纳米结构的硅酸盐矿物,其特殊的层状纳米结构,使其具有吸附能力强,稳定性好,应用广泛等特点.本文主要介绍了蒙脱石基生物纳米复合功能材料在酶催化、抗菌、医药和环保等领域中的研究、开发及应用情况,并探讨了粘土矿物基纳米复合材料的发展前景.     

LB膜模板诱导晶体取向生长

LB膜作为模板可诱导晶体取向成核和外延生长,生成的晶体材料具有独特的微观结构和优异的物理化学性能.这种方法对于生物矿化现象的研究以及新颖材料合成策略的设计等方面具有重要的启示意义.本文从LB膜诱导晶体取向生长的机理及利用等方面综述了该领域研究的最新进展.     

水热法制备纳米线研究进展

纳米线因其显著的边界效应、易单晶化、高比线径、大比表面积、高强度、高韧性、低导电性等特点,广泛应用于电子器件、太阳能转换、纤维合成、微电池制造等领域.水热法是制备纳米线的常用方法,本文综述了水热法工艺参数,矿化剂种类、反应温度、反应时间等对调控纳米线表面形貌与性能影响的研究进展,并提出研究中需要解决的问题.矿化剂种类对纳米线的形成及形貌有显著影响,矿化剂浓度的升高会促进纳米线的形成,但是超过某一临界值又会反过来影响纳米线的形貌与抑制纳米线的形成;反应温度直接影响晶粒的生长,温度过高会导致杂相的产生,不利于形成稳定晶型,温度太低又不足以提供纳米线生长的动力;随着反应时间的增加,纳米线长径比增加,比表面积增加,表面变得更光滑,当反应时间过长时,纳米线横向过度生长,纳米线长径比降低,纳米线变为纳米棒.     

硫酸软骨素模板诱导片状纳米羟基磷灰石的仿生合成

依据生物矿化的原理,以硫酸软骨素(ChS)为模板合成了片状纳米羟基磷灰石(HA).用X射线衍射仪(XRD)、傅立叶变换红外光谱(FTIR)、透射电镜(TEM)和热重-差热分析仪(TG-DTA)对纳米HA的结构、组成、形貌和热性能进行表征.结果表明ChS的浓度很大程度地影响了HA的形貌,浓度较低时(0.1～0.3;质量分数),形成短纤维状晶体;浓度较高时(≥0.5;质量分数),则形成片状晶体.电导率测试结果表明,ChS和钙离子之间存在较强相互作用.本文还讨论了HA的生长机理.     

Compositional analysis of a polymer-induced liquid-precursor (PILP) amorphous CaCO3 phase

Amorphous calcium carbonate (ACC) has been of keen interest in the biomimetics field because of recent evidence which suggests it plays an important role in biomineralization. In this report, an in vitro model system is used to examine the composition of an amorphous phase generated by polyanionic process-directing agents, such as the sodium salt of polyaspartic acid (Pasp), which is considered a simple mimic to the proteins associated with calcific biominerals. This additive leads to the formation of a highly hydrated, amorphous mineral precursor to calcium carbonate (CaCO₃), referred to as a polymer-induced liquid-precursor (PILP) phase. The precursor phase was collected by centrifugation, and the quantity of precursor phase and the water content were determined. It was found that Pasp promotes and stabilizes the amorphous precursor, which has a composition that steadily changes with time as the polymer and water are excluded. Elemental analysis was used to investigate the role of the polymer in influencing the calcium/carbonate ratio, the water content, and the amount of precursor phase. Raman and ATR-FTIR spectroscopy were used to compare the compositions of the precursor phases generated with different polymeric concentrations. The role of Pasp in generating and stabilizing the ACC precursor phase is discussed.     

The influence of crystallization conditions on the onset of dendritic growth of calcium carbonate

Understanding the crystallization of calcium carbonate is relevant in numerous fields like biomineralization, geology and industrial applications where calcium carbonate forms. In order to enhance the knowledge about the formation of calcium carbonate with focus on the vaterite polymorph, in this work calcium carbonate has been crystallized in aqueous solutions at temperatures from 5 °C to 90 °C. Special attention has been directed to higher temperatures for which the effect of the initial supersaturation on the resulting crystal morphologies and the onset of dendritic growth have been studied. In analogy to snow crystal formation, it has been found that in a certain temperature range hexagonal plate‐like crystals form at low supersaturation whereas dendritic patterns start to appear at higher supersaturation. The symmetrical branches characteristic for dendritic growth get less pronounced as the temperature is decreased. The results reported here related to the interdependence between supersaturation, crystal morphology and growth mechanisms, can be used in future works to predict particle formation and to design crystal architectures. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of impurity on rhythmic crystallization of calcium carbonate in agar gel

During the gel growth of calcite crystals in test tubes, for a narrow concentration of inner and outer electrolytes we observed rhythmic crystallization of calcium carbonate. In this paper the effect of adding impurities on the pattern of periodic crystallization of calcium carbonate has been presented. The addition of impurities either increases or decreases the solubility of reaction product and hence may affect the rate of nucleation of calcium carbonate crystals. The variation of spacing coefficient and velocity constant due to the addition of impurities has also been studied.     

Growth of calcium carbonate in polyacrylamide hydrogel: Investigation of the influence of polymer content

The growth of calcium carbonate crystals has attracted growing attention as a model system for biomineralisation processes. Organic molecules and gelatinous matrices are known to play an essential role in the formation of hard tissues. For the investigation of the function of specific influence factors, a model experiment is necessary. Several hydrogels were previously tested as growth matrices for calcium carbonate.

For laboratory experiments, a double diffusion set-up for the growth of crystals in gels was established earlier. Calcium carbonate crystals were grown in polyacrylamide hydrogels.

Here the influence of the polymer content in the hydrogels on the crystallisation behaviour is reported. Time-resolved and spatially resolved crystallisation experiments were conducted. The collected calcium carbonate precipitates were analysed by light microscopy, scanning electron microscopy and X-ray diffraction.

The morphology of the developing crystals was found to be dependent on the polymer content of the hydrogels.     

Crystal Growth in Gels at Elevated Pressures: The Upper Limit of Temperature for Metastable Formation of Aragonite

Both rapid precipitation and diffusion controlled gel growth were applied to crystallize calcium carbonate at temperatures in the range of 100 °C to 270 °C. The amount of aragonite was determined by means of X-ray diffraction data. The morphology of the aragonite crystals are described. Metastable formation of aragonite was observed only at temperatures below 270 °C.     

Using an electrochemical technique to study the effective variables on morphology and deposition of CaCO3 and BaSO4 at the metal surface

In this work using an electrochemical technique, deposition and crystal growth of calcium carbonate and barium sulphate at a stainless steel electrode is investigated through a rotating disk electrode involving oxygen reduction under diffusion condition. The influence of some parameters such as pressure, temperature, surfactant, cosalt and pH on morphology and deposition of CaCO₃ and BaSO₄ at surface of the stainless steel are studied. The results of the temperature tests reveal that the surface deposition is reduced by increase of the temperature and decrease of pH. The pressure also proves to have a significant influence on the morphology and the structure of calcium carbonate and barium sulphate deposition at the metal surface. With establishing a flow condition at high pressure, nucleation and deposition of calcium carbonate and barium sulphate at the metal surface generate the nano size of CaCO₃ and BaSO₄ crystals and leads to reduction of the coverage of the surface. In the presence of surfactant, it is shown that deposition of the calcium carbonate decreases the surface coverage so that after the point of the critical molar concentration of surfactant, a reduction of deposition of the calcium carbonate and barium sulphate at the surface can be clearly observed. Finally, influence of monovalent cosalts such as NaCl and KCl are investigated so that it does not present any certain trend in the deposition; however the morphology of the deposited crystal considerably changes.     

多糖模板调控纳米无机晶体生长

以多糖为模板调控无机晶体的生长是近年来一个新的研究方向。利用组成多糖的单糖残基种类差异、连接位置和糖苷键的差异,链内或链间形成氢键的二级结构差异,可以组成具有多样化构象、不同分子质量的多糖模板,从而制备出具有不同结构和独特性能的无机晶体材料。本文重点讨论了多糖模板调控碳酸钙、纤铁矿、二氧化硅及硅酸盐、纳米硒、磷酸钙、金属和金属氧化物等无机晶体的生长,指出了该领域所面临的问题和将来的发展方向。     

Synthesis and Design of MnCO<Subscript>3</Subscript> Crystals with Different Morphologies by Supported Liquid Membrane

Abstract  A biomimetic supported liquid membrane (SLM) system was employed to control the morphology of manganese carbonate. Some interesting morphologies including nanowire/hollow spheres/twinborn spheres could be readily generated by using EDA (ethylenediamine), EDTA (ethylenediaminetetracid) or NTA (nitrilotriacetic acid) as cooperative modifiers in the mineralization process, under the conditions of pH 10, 0.01% of crystal modifier and ambient temperature. The key factor in this system was the cooperative template effect of SLM and the crystal modifiers. The clarification of fantastic morphogenesis of them could be valuable for understanding of biomineralization processes. Index Abstract  A biomimetic supported liquid membrane (SLM) system was employed to control the morphology of manganese carbonate. Some interesting results including nanowires/hollow spheres/twinborn spheres/etc. could be readily generated by using EDA (ethylenediamine), EDTA (ethylenediaminetetracid) or NTA (nitrilotriacetic acid) as cooperative modifiers in the mineralization process. The clarification of fantastic morphogenesis of them could be valuable for the understanding of biomineralization processes..