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Amorphous Calcium (amorphous + calcium)

Distribution by Scientific Domains

Polymers and Materials Science	81%

Terms modified by Amorphous Calcium

amorphous calcium phosphate

Selected Abstracts

Biomineralization: Amorphous Calcium Carbonate is Stabilized in Confinement (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2010
Mater.
F. C. Meldrum, H. K. Christenson, et al. describe on page 2108 a device based on two crossed cylinders used to study confinement effects on precipitation of calcium carbonate. Amorphous calcium carbonate (ACC) remains stable for days even when the confining surfaces are as far as a micrometer apart. Such stabilization of ACC in vitro may have important implications for the understanding of biomineralization. [source]

Amorphous Calcium Carbonate is Stabilized in Confinement

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2010
Christopher J. Stephens
Abstract Biominerals typically form within localized volumes, affording organisms great control over the mineralization process. The influence of such confinement on crystallization is studied here by precipitating CaCO3 within the confines of an annular wedge, formed around the contact point of two crossed half-cylinders. The cylinders are functionalized with self-assembled monolayers of mercaptohexadecanoic acid on gold. This configuration enables a systematic study of the effects of confinement since the surface separation increases continuously from zero at the contact point to macroscopic (mm) separations. While oriented rhombohedral calcite crystals form at large (>10,µm) separations, particles with irregular morphologies and partial crystallinity are observed as the surface separation approaches the dimensions of the unconfined crystals (5,10,µm). Further increase in the confinement has a significant effect on the crystallization process with flattened amorphous CaCO3 (ACC) particles being formed at micrometer separations. These ACC particles show remarkable stability when maintained within the wedge but rapidly crystallize on separation of the cylinders. A comparison of bulk and surface free-energy terms shows that ACC cannot be thermodynamically stable at these large separations, and the stability is attributed to kinetic factors. This study therefore shows that the environment in which minerals form can have a significant effect on their stability and demonstrates that ACC can be stabilized with respect to the crystalline polymorphs of CaCO3 by confinement alone. That ACC was stabilized at such large (micrometer) separations is striking, and demonstrates the versatility of this strategy, and its potential value in biological systems. [source]

Structural Characterization of the Transient Amorphous Calcium Carbonate Precursor Phase in Sea Urchin Embryos,

ADVANCED FUNCTIONAL MATERIALS, Issue 10 2006
Y. Politi
Abstract Sea urchin embryos form their calcitic spicular skeletons via a transient precursor phase composed of amorphous calcium carbonate (ACC). Transition of ACC to calcite in whole larvae and isolated spicules during development has been monitored using X-ray absorption spectroscopy (XAS). Remarkably, the changing nature of the mineral phase can clearly be monitored in the whole embryo samples. More detailed analyses of isolated spicules at different stages of development using both XAS and infrared spectroscopy demonstrate that the short-range order of the transient ACC phase resembles calcite, even though infrared spectra show that the spicules are mostly composed of an amorphous mineral phase. The coordination sphere is at first distorted but soon adopts the octahedral symmetry typical of calcite. Long-range lattice rearrangement follows to form the calcite single crystal of the mature spicule. These studies demonstrate the feasibility of real-time monitoring of mineralized-tissue development using XAS, including the structural characterization of transient amorphous phases at the atomic level. [source]

Biomineralization: Amorphous Calcium Carbonate is Stabilized in Confinement (Adv. Funct.

Structural Characterization of the Transient Amorphous Calcium Carbonate Precursor Phase in Sea Urchin Embryos,

On the Stability of Amorphous Minerals in Lobster Cuticle

ADVANCED MATERIALS, Issue 40 2009
Ali Al-Sawalmih
In situ X-ray diffraction during heating of lobster cuticle reveals three regions of thermally induced transformations: 1)Chitin decomposition, 2) amorphous calcium carbonate (ACC) , calcite transformation, and 3) amorphous calcium phosphate (ACP) , hydroxyapatite transformation. These results provide new insights into the stabilization mechanisms of amorphous biominerals based on ACC and ACP. [source]

Influence of Structural Principles on the Mechanics of a Biological Fiber-Based Composite Material with Hierarchical Organization: The Exoskeleton of the Lobster Homarus americanus

ADVANCED MATERIALS, Issue 4 2009
Helge-Otto Fabritius
Abstract The cuticle of the lobster Homarus americanus is a nanocomposite, such as most structural biological materials. It consists of a matrix of chitin-protein fibers associated with various amounts of crystalline and amorphous calcium carbonate in the rigid parts of the body, and is organized hierarchically at all length scales. One prominent design principle found in the hierarchical structure of such biological fibrous composite materials is the twisted plywood structure. In the lobster cuticle, it is formed by superimposing and gradually rotating planes of parallel aligned chitin-protein fibers. To adjust the mechanical properties to the requirements on the macroscopic level, the spatial arrangement and the grade of mineralization of the fibers can be modified. A second design principle of lobster cuticle is its honeycomb-like structure, generated by the well-developed pore canal system, whose twisted ribbon-shaped canals penetrate the cuticle perpendicular to its surface. Due to the hierarchical structure, the mechanical properties of the lobster cuticle have to be investigated at different length scales, which is essential for the understanding of the structure,mechanical function relations of mineralized tissues (e.g., potentially also bone and teeth). In order to investigate the influence of the structural principles on the mechanical properties on the macroscopic scale miniaturized tensile, compression, and shear tests were carried out to obtain integral mechanical data. Characterization of the microstructure included scanning electron microscopy (SEM) combined with energy dispersive X-ray (EDX) measurements. [source]

Fabrication of aragonite rosette superstructure through the weak interaction between nonionic polymers and Ca2+

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
Shuxian Shi
Abstract The controlled formation of aragonite by simple method under ambient condition is a big challenge for biomaterial scientists. In this article, we took poly (N -vinyl pyrrolidone) (PVP) as an example to investigate the influence of water-soluble nonionic polymers on the polymorphs of CaCO3 via CO2 diffusion method under ambient pressure and temperature, and found that the existence of PVP molecules favors the formation of aragonite with rosette superstructure. A possible mechanism is proposed that nonionic polymers can be doped into amorphous calcium carbonate (ACC) particles and further participate in the transformation process from ACC to aragonite and then promotes the formation of rosette superstructure through parallel aggregation by crosslinking the aragonite nuclei. The experiments of CaCO3 crystallization in presence of poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA) confirmed the mechanism. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Bioinspired Mineralization of Inorganics from Aqueous Media Controlled by Synthetic Polymers

MACROMOLECULAR BIOSCIENCE, Issue 2 2007
Katarzyna Gorna
Abstract The formation of inorganic structures in nature is commonly controlled by biogenic macromolecules. The understanding of mineralization phenomena and the nucleation and growth mechanisms involved is still a challenge in science but also of great industrial interest. This article focuses on the formation and mineralization of two archetypical inorganic materials: zinc oxide and amorphous calcium carbonate (ACC). Zinc oxide is selected as a model compound to investigate the role that polymers play in mineralization. Most of the effort has been devoted to the investigation of the effects of double-hydrophilic block and graft copolymers. Recent work has demonstrated that latex particles synthesized by miniemulsion polymerization, properly functionalized by various chemical groups, have similar effects to conventional block copolymers and are excellently suited for morphology control of ZnO crystals. Latex particles might serve as analogues of natural proteins in biomineralization. The second example presented, ACC, addresses the issue of whether this amorphous phase is an intermediate in the biomineralization of calcite, vaterite, or aragonite. Conditions under which amorphous calcium carbonate can be obtained as nanometer-sized spheres as a consequence of a liquid,liquid phase segregation are presented. Addition of specific block copolymers allows control of the particle size from the micrometer to the submicrometer length scale. The physical properties of novel materials synthesized from concentrated solution and their potential applications as a filler of polymers are also discussed. [source]

In vivo effects of amorphous calcium phosphate-containing orthodontic composite on enamel demineralization around orthodontic brackets

AUSTRALIAN DENTAL JOURNAL, Issue 3 2010
T Uysal
Abstract Background:, The aim of this study was to evaluate the in vivo effects of an amorphous calcium phosphate-containing orthodontic composite in reducing enamel demineralization around orthodontic brackets, and to compare it with the control. Methods:, Fourteen orthodontic patients were divided into two equal groups. They received brackets fitted to all first premolars, bonded with either Aegis Ortho® (The Bosworth Co.), an ACP-containing orthodontic composite (experimental group), or Concise® (3M Dental Products), a resin-based orthodontic composite (control group). After 30 days, the teeth were extracted and longitudinally sectioned, and evaluated by superficial-microhardness analysis. The determinations were made at the bracket edge cementing limits and at occlusal and cervical points 100 and 200 ,m away from the edge. In all of these positions, indentations were made at depths of 10, 20, 30, 50, 70, and 90 ,m from the enamel surface. Analysis of variance (ANOVA) and Tukey post hoc test was used. The statistical significance level was set at p <0.05. Results:, The ANOVA showed statistically significant differences for position, material, depth, and their interactions (p <0.001). The multiple comparison test showed that the ACP-containing orthodontic composite was significantly more efficient than the control composite, reducing enamel demineralization in almost all evaluations (p <0.001). Conclusions:, Present results indicated that ACP-containing orthodontic composite for bonding orthodontic brackets successfully inhibited demineralization in vivo. This effect was localized to the area around the brackets and was statistically significant after 30 days. [source]