Nacre Research Articles

Derivation of the stress-strain behavior of the constituents of bio-inspired layered TiO2/PE-nanocomposites by inverse modeling based on FE-simulations of nanoindentation test.

Owing to the apparent simple morphology and peculiar properties, nacre, an iridescent layer, coating of the inner part of mollusk shells, has attracted considerable attention of biologists, material scientists and engineers. The basic structural motif in nacre is the assembly of oriented plate-like aragonite crystals with a 'brick' (CaCO3 crystals) and 'mortar' (macromolecular components like proteins) organization. Many scientific researchers recognize that such structures are associated with the excellent mechanical properties of nacre and biomimetic strategies have been proposed to produce new layered nanocomposites. During the past years, increasing efforts have been devoted towards exploiting nacre's structural design principle in the synthesis of novel nanocomposites. However, the direct transfer of nacre's architecture to an artificial inorganic material has not been achieved yet. In the present contribution we report on laminated architecture, composed of the inorganic oxide (TiO2) and organic polyelectrolyte (PE) layers which fulfill this task. To get a better insight and understanding concerning the mechanical behaviour of bio-inspired layered materials consisting of oxide ceramics and organic layers, the elastic-plastic properties of titanium dioxide and organic polyelectrolyte phase are determined via FE-modelling of the nanoindentation process. With the use of inverse modeling and based on numerical models which are applied on the microscopic scale, the material properties of the constituents are derived.

Beirut

For over thirty years now, Mr Abdel Halim Hicham has run a shop in the heart of Beirut's upmarket district of Hamra. On sale here is the woodwork inlaid with mother of pearl that he crafts by hand. Mr Hicham is a Lebanese artisan of a kind that is on the wane. He learned the trade at his father's knee and began work at the age of twelve. His is a family business, inherited through bloodline and Mr Hicham has a lifetime's knowledge of wood carving, of how to chisel the motehr of pearl into delicate, translucent shapes from broken bits of shell and how to inlay it carefully, in designs that are sometimes geometric and traditional, other times more flowing and dynamic. With utmost care, and slow precision, as if unaware of the passage of time, he glues each minute piece into the fragrant cedar wood of his country. Customers must wait until he is done. In fact, his show has more the air of a workshop, cluttered and used, the pieces of furniture, wall hangings and tabletops chaotically piled one on top of another. Some have collected dust and appear untouched for months. Others he polishes lovingly with a dirty rag dipped in turpentine. Mr Hicham keeps erratic hours. Often his shop is not open and potential customers can only peer in through the smudged window at the piles of inlaid woodwork inside. A handwritten message on the door cryptically says 'Call me', followed by a mobile number.

Fracture Mitigation Strategies in Gastropod Shells

For hundreds of millions of years, gastropods have been evolving, modifying their external calcified shells for defense against shell-breaking and drilling predators. They have evolved primarily to use two different aragonitic microstructures: the evolutionary older Nacre (mother of pearl) structure and the more recently developed crossed-lamellar structure. By using both of these structures, gastropods are able to produce shells that are significantly tougher then geologic aragonite. However, the crossed-lamellar structure allows for a wider variety of shell morphologies, ensuring its increasing presence since the Mesozoic Marine Revolution more than 200 million years ago.

ChemInform Abstract: Hierarchical Structure and Mechanical Properties of Nacre: A Review

AbstractReview: 123 refs.

Pearl extract enhances the migratory ability of fibroblasts in a wound healing model

Context: For 2000 years, traditional Chinese medicine has been used as a remedy for general health improvement, including the fight against aging. Pearl powder has recently been used as a health food that has antioxidant, antiaging, antiradioactive, and tonic activities for cells; it is also applied to cure aphthous ulcer, gastric ulcer, and duodenal ulcer on clinical therapy. In addition, the mother of pearl, nacre, could enhance the cell adhesion and tissue regeneration of skin fibroblasts.Objective: Fibroblast is regarded as indispensable in the processes of wound healing. Therefore, the effect of pearl extract (PL) on fibroblasts is investigated in this study.Materials and methods: PL is produced by a room temperature super extraction system (Taiwan patent no. I271 220). DMEM medium containing PL (300 μg/mL) was used to examine the effect of migration-promoting potential on human fibroblast cell line or human primary fibroblast cells in a wound healing model in vitro.Results: Medium containing PL (300 μg/mL) demonstrated that the migratory cell numbers of fibroblasts were three times more than that without PL, and mRNA expression of collagen type III was higher than in collagen type I in fibroblasts. It revealed a migration-promoting potential of human fibroblasts in a wound healing model in vitro.Discussion and conclusion: The present study found that the migration-promoting effect in PL, which could be a supplement in cell culture. These data suggest PL could be useful for enhancing the wound healing of fibroblasts.

Novel Basic Protein, PfN23, Functions as Key Macromolecule during Nacre Formation

The fine microstructure of nacre (mother of pearl) illustrates the beauty of nature. Proteins found in nacre were believed to be "natural hands" that control nacre formation. In the classical view of nacre formation, nucleation of the main minerals, calcium carbonate, is induced on and by the acidic proteins in nacre. However, the basic proteins were not expected to be components of nacre. Here, we reported that a novel basic protein, PfN23, was a key accelerator in the control over crystal growth in nacre. The expression profile, in situ immunostaining, and in vitro immunodetection assays showed that PfN23 was localized within calcium carbonate crystals in the nacre. Knocking down the expression of PfN23 in adults via double-stranded RNA injection led to a disordered nacre surface in adults. Blocking the translation of PfN23 in embryos using morpholino oligomers led to the arrest of larval development. The in vitro crystallization assay showed that PfN23 increases the rate of calcium carbonate deposition and induced the formation of aragonite crystals with characteristics close to nacre. In addition, we constructed the peptides and truncations of different regions of this protein and found that the positively charged C-terminal region was a key region for the function of PfN23 Taken together, the basic protein PfN23 may be a key accelerator in the control of crystal growth in nacre. This provides a valuable balance to the classic view that acidic proteins control calcium carbonate deposition in nacre.

Influence of the Depth on the Shape and Thickness of Nacre Tablets of Pinctada margaritifera Pearl Oyster, and on Oxygen Isotopic Composition

Nacre, or mother of pearl, is composed of aragonite tablets and is produced by some mollusks. Because of the highly organized internal structure, chemical complexity, mechanical properties and optical effects of nacre, its formation is among the best-studied examples of calcium carbonate biomineralization. The pearl oyster Pinctada margaritifera is harvested in French Polynesia for pearl farming. The quality of the pearl depends on the quality of the nacre on its surface and its iridescent colors are affected by the thickness of the layers. Here we report on an experimental study conducted to influence the shape and the thickness of nacre tablets by keeping pearl oysters at four different depths (7, 20, 30 and 39 m) for one week. Scanning electron microscopy was used to measure the thickness of the nacre tablets and to analyze their final shape. The shape of the tablets changed from hexagonal to rhomboid at a depth of 39 m. The change in shape led to a change in size. The thickness of the tablets was reduced by between 16 and 30% on average. We also measured the oxygen isotopic composition using Secondary Ion Mass Spectrometry. In this study, we demonstrated that depth can modify the size, shape and thickness of nacre tablets, but not the d18O. This environmental modification is important for the biomineralization of the shell of the pearl oyster Pinctada margaritifera.

Molecular characteristics and expression of calmodulin cDNA from the freshwater pearl mussel, Hyriopsis schlegelii

Calmodulin (CaM) is a multifunctional intracellular calcium ion receptor protein that participates in a range of cellular processes, including calcium metabolism in mussels. To investigate the role of CaM in freshwater mollusk shell calcium metabolism, the full-length CaM cDNA was isolated from the freshwater pearl mussel, Hyriopsis schlegelii (referred to as hsCaM) using SMART RACE technology. The full-length hsCaM was 855 bp in size, containing a 70-bp 5'-untranslated sequence, a 447-bp open reading frame, a 309-bp 3'-untranslated sequence, and a 26-nucleotide long poly(A) tail. The hsCaM mRNA expression in different mussel tissues was examined using real-time PCR. The hsCaM mRNA was found to be ubiquitously expressed, but far more abundant in the gill, foot, and mantle than in the posterior adductor muscle. Real-time PCR was also used to determine hsCaM mRNA expression levels in mantle tissues of H. schlegelii at different ages. No significant differences between one-, two-, and three-year-old mussels were detected, but expression increased in four-year-old mussels and then decreased in five-year-old mussels. CaM appears to be involved in calcium regulation of the mantle in four-year-old mussels, which may secrete more mother of pearl during pearl culture.

Hierarchical structure and mechanical properties of nacre: a review

Nacre (known as mother of pearl) is the iridescent inner shell layer of some mollusks. Nacre is composed of 95 wt% aragonite (a crystallographic form of CaCO3) and 5 wt% organic materials (proteins and polysaccharides). It is well known that it exhibits high fracture toughness, much greater than that of monolithic aragonite, because of its ingenious structure. It also exhibits energy absorption properties. It has a complex hierarchical microarchitecture that spans multiple length scales from the nanoscale to the macroscale. It includes columnar architectures and sheet tiles, mineral bridges, polygonal nanograins, nanoasperities, plastic microbuckling, crack deflection, and interlocking bricks, which exhibit a remarkable combination of stiffness, low weight and strength. Nacre's special self-assembly characteristics have attracted interest from materials scientists for the development of laminated composite materials, molecular scale self-assembly and biomineralization. This paper reviews the characteristics of hierarchical structure and the mechanical properties of nacre that provide the desired properties, and the latest developments and biomimetic applications.

Detection and partial identification of proteins in pearls formed in Hyriopsis cumingii (Lea)

Pearl and nacre (mother of pearl) have similar chemical compositions. However, more than 20 proteins have been identified in nacre, yet none have been detected in pearl thus far. This study aimed to detect and identify protein in pearl. Two batches of pearls formed in Hyriopsis cumingii (Lea) were purchased from two pearl farms. They were ground into a powder of >10,000 mesh followed by ultra-sonication and extraction in water for 4 h at room temperature. The solution was centrifuged and the supernatant was saved as pearl powder water extract. A portion of the extract was heated at 121°C for 20 min. TCA precipitation and tricine–SDS-PAGE were conducted on both the heated and non-heated extracts. After silver nitrate staining, the heated extract demonstrated a distinct protein signal, but the non-heated extract did not. The protein band from each of the two heated extracts was excised from the gel and subjected to tryptic digestion and RP-nano-HPLC-ESI-MS/MS analysis. A MASCOT search of the results indicated that one protein had significant sequence homology to a putative vitelline envelop receptor for lysine in the common marine mussel Mytilus edulis , and the other to the putative imaginal disc growth factor (IDGF) of Diaprepes abbreviatus . Key words : Pearl, nacre, Hyriopsis cumingii (Lea), RP-nano-HPLC-ESI-MS/MS analysis, MASCOT search, vitelline envelop receptor for lysine, imaginal disc growth factor.

Potential Induction of Bone Regeneration by Nacre: An In Vitro Study

Because of limitations of autogenous grafts, alternative bone substitute material was investigated for its capacity in promoting bone formation. This study compared the osteogenic effects of nacre (mother of pearl) and beta-tricalcium phosphate (β-TCP). Human bone cells (HBCs) were obtained from the culture of bone tissues after orthognathic surgery. The HBCs were cocultured with nacre chips of the giant oyster Pinctada maxima and with β-TCP particles for 1, 2, 3, and 4 weeks. Cells of each week specimens were used to study alkaline phosphatase (ALP), bone sialoprotein (BSP), and osteocalcin (OC) gene expression by noncompetitive reverse-transcriptase polymerase chain reaction and to study BSP synthesis by means of an immunocytochemical technique in conjunction with fluorescent microscopy. Reverse-transcriptase polymerase chain reaction demonstrated stronger expression levels of ALP mRNA in HBCs cocultured with the nacre chips than those with β-TCP at weeks 2 and 4. BSP gene expression levels in HBCs with nacre were more intense compared with β-TCP at weeks 3 and 4. Although the OC gene expression level in HBCs with β-TCP was higher than those with nacre at week 2, the expression was not different at weeks 3 to 4. Immunocytochemical study revealed that BSP synthesis were presented in the nacre and β-TCP from week 2 and decreased toward week 4. This study indicated that nacre promotes ALP, BSP, and OC gene expression.

Nanoscale structure and mechanical behavior of growth lines in shell of abalone Haliotis gigantea

In the natural world, bottom-up hierarchical construction of complex structures results in materials with remarkable properties. A well known example is the nacre of mollusk shells, commonly called "mother of pearl", whose excellent strength and toughness has been the subject of research for many decades. A significant discovery has been the presence of periodic layers called "growth lines". These are thin distinct layers within the bulk of the shell which form periodically, with their structure affected by environmental changes. Studies of their formation and behavior offer valuable insight into the architecture of seashells. In this work, the structure and mechanical behavior of growth lines in shells of abalone Haliotis gigantea were investigated using electron microscopy and nanoindentation. Growth lines form directly out of nacre into layers of blocks and irregular particles. In comparison to nacre, they have basic structures, form rapidly, and are harder, which suggest that they serve a protective role during lifecycle transitions. This exemplifies how natural structures are able to closely control growth architecture in order to form different structures for different functions, all from the same base materials.

Making Mother of Pearl

Nacre is an iridescent layer of calcium carbonate lining the inside of shells of marine mollusks and is commonly known as “mother of pearl.” It is composed of layers of uniformly oriented crystals of aragonite (a metastable form of calcium carbonate) separated by layers of organic matrix. How the ordered structure of aragonite layers is achieved has been unclear. Suzuki et al. (p. [1388][1], published online 13 August 2009; see the Perspective by [Kroger][2] ) identified two acidic matrix proteins (Pif 97 and Pif 80) that regulate nacre formation in the Japanese pearl oyster. The proteins appear to form a complex in which Pif 80 binds to aragonite and Pif 97 binds to other macromolecules in the organic matrix. [1]: /lookup/doi/10.1126/science.1173793 [2]: /lookup/doi/10.1126/science.1177055

An Acidic Matrix Protein, Pif, Is a Key Macromolecule for Nacre Formation

The mollusk shell is a hard tissue consisting of calcium carbonate crystals and an organic matrix. The nacre of the shell is characterized by a stacked compartment structure with a uniformly oriented c axis of aragonite crystals in each compartment. Using a calcium carbonate-binding assay, we identified an acidic matrix protein, Pif, in the pearl oyster Pinctada fucata that specifically binds to aragonite crystals. The Pif complementary DNA (cDNA) encoded a precursor protein, which was posttranslationally cleaved to produce Pif 97 and Pif 80. The results from immunolocalization, a knockdown experiment that used RNA interference, and in vitro calcium carbonate crystallization studies strongly indicate that Pif regulates nacre formation.

Biomimetic design of materials and biomaterials inspired by the structure of nacre

The micro-architecture of nacre (mother of pearl) has been classically illustrated as a 'brick-and-mortar' arrangement. It is clear now that hierarchical organization and other structural features play an important role in the amazing mechanical properties of this natural nanocomposite. The more important structural characteristics and mechanical properties of nacre are exposed as a base that has inspired scientists and engineers to develop biomimetic strategies that could be useful in areas such as materials science, biomaterials development and nanotechnology. A strong emphasis is given on the latest advances on the synthetic design and production of nacre-inspired materials and coatings, in particular to be used in biomedical applications.

Formation of aragonite mesocrystals and implication for biomineralization

Highly oriented aragonite tablets have been found in the nacre layers of molluscan shell (or mother of pearl). In this article, we show that highly organized aragonite rods can be prepared over a broad range of pH values (1.5 to 6.9) and in the absence of any bio- or organic macromolecules. The organized rods were characterized by XRD, FTIR, FESEM, TEM, SAED, and EDX techniques. FESEM results reveal that the mesoscale aragonite rods are not only assembled with aragonite microrods end-to-end, and side-to-side, but are also partially fused to one another, forming flat, faceted surfaces, i.e., mesocrystal structure. TEM and SAED analyses confirm that the organized rods have the same crystallographic symmetry as single-crystal aragonite, and thus the self-assembly process is energetically favorable. Similar assembly processes also occur for the mineral strontianite of the aragonite group, revealing the occurrence of a general self-assembly process. The driving force controlling the self-assembly process may originate from the inherent anisotropic dipole-dipole interactions between the assembled units. Such dipole interaction may generally occur in biomineralization of nacre layers in molluscan shell, and orchestrate aragonite nanocrystals in an aragonite tablet to coherently orient and array. Furthermore, the dipole-dipole interactions may also contribute to the co-orientation of the aragonite tablets in the same nacreous column. Therefore, our experimental results may provide insight into biomineralization mechanisms. It appears that biological genetic and crystallochemical factors may synergistically operate in biomineralization.

Reducing Effect of Feeding Powdered Nacre ofPinctada maximaon the Visceral Fat of Rats

An abdominal fat accumulation complicated by high blood triglycerides is regarded as a risk factor of metabolic syndrome. Feeding powdered nacre, mother of pearl, from Pinctada maxima, resulted in reduced body weight, visceral fat amount, and blood triglyceride level without influencing the food intake, body length, or amount of muscular tissue, suggesting that nacre powder specifically could decrease visceral fat.

Crecimiento y mortalidad de la concha nácar Pteria sterna en bancos silvestres de Baja California Sur, México

La concha nácar Pteria sterna sustenta los perlicultivos en México, y es la base de producción de perlas en el continente Americano. Está bajo protección especial desde 1994, y solo puede capturarse semilla natural para cultivo e investigación. Determinamos su crecimiento y mortalidad en bancos silvestres, registrando la altura de ostras de Santa Rosalía, Mulegé y Bahía de Loreto (1997-99). La longitud máxima estimada fue 130.35 mm (124.22-136.48 mm, P > 0.95). Las frecuencias de longitudes se ordenaron en un año virtual (Guanco 1991). Los parámetros de crecimiento de von Bertalanffy estimados con el programa ELEFAN I fueron: L8= 156.02 mm, k=0.48año-1, t0 =-0.216 años, C= 0.43 y WP = 0.73; el índice de desempeño de crecimiento fue Φ’ = 4.068. La mortalidad total fue de Z = 3.34 año -1 por longitud convertida a curva de captura. La regresión del peso total y la altura tuvo la expresión W = 0.000756 * L(i) 2.7075 (r2=0.90, n=233). Mostramos la diferencia entre los parámetros de crecimiento en condiciones de repoblamiento experimental y aquellos de individuos silvestres de P. sterna. El valor de mortalidad total es comparable a aquellos de Pinctada fucata en el mar Rojo o P. radiata en el mar Mediterráneo.

Inside Mother-of-Pearl

Inside Mother-of-Pearl

Characteristic crystal orientation of folia in oyster shell, Crassostrea gigas

The thin sheets of calcite, termed folia, that make up much of the shell of an oyster are composed of foliated lath. Folia of the giant Pacific oyster ( Crassostrea gigas) were examined using TEM (transmission electron microscopy) and tested using microindentation and nanoindentation techniques. Analysis of the Kikuchi patterns obtained from the folia showed that there are two types (type I and type II) of preferred orientation, with an angle of around 70° between them. Nanoindentation tests showed that the folia exhibit a hardness of about 3 GPa and elastic modulus of about 73 GPa. Microcracks were generated using a microindenter in order to study the fracture mechanisms of the folia. Following on from these investigations, fracture mechanisms are discussed in conjunction with the correlation between preferred orientation and structural characteristics during cracking of the folia. Comparing the morphology and the polymorphism with nacre (also known as mother of pearl), the advantages of the relatively fast crystal growth and less amount of organic matrix in folia may have interesting implications for the development of sophisticated synthetic materials.