Guinea fowl eggshell structural analysis at different scales reveals how organic matrix induces microstructural shifts that enhance its mechanical properties.

Guinea fowl eggshells have an unusual structural arrangement that is different from that of most birds, consisting of two distinct layers with different microstructures. This bilayered organization, and distinct microstructural characteristics, provides it with exceptional mechanical properties. The inner layer, constituting about one third of the eggshell thickness, contains columnar calcite crystal units arranged vertically as in most bird shells.

Chemical and Ultrastructural Characterization of Dentin Treated with Remineralizing Dentifrices.

The aim of this study is to investigate dentin chemical and ultrastructural changes upon exposure to remineralizing dentifrices. Dentin disks were obtained from permanent human molars and treated for 7 days with the dentifrices: (1) C group-control (no dentifrice); (2) S group-Sensodyne Repair & Protect; (3) D group-Dentalclean Daily Regenerating Gel; and (4) DB group-D group + Dentalclean regenerating booster. Afterwards, samples were submitted to an additional 7 days of toothbrushing associated with daily acidic challenge.

Focusing on the Native Matrix Proteins in Calcific Aortic Valve Stenosis.

Calcific aortic valve stenosis (CAVS) is a widespread valvular heart disease affecting people in aging societies, primarily characterized by fibrosis, inflammation, and progressive calcification, leading to valve orifice stenosis. Understanding the factors associated with CAVS onset and progression is crucial to develop effective future pharmaceutical therapies. In CAVS, native extracellular matrix proteins modifications, play a significant role in calcification in vitro and in vivo.

DNA hydrogels for bone regeneration.

DNA-based biomaterials have been proposed for tissue engineering approaches due to their predictable assembly into complex morphologies and ease of functionalization. For bone tissue regeneration, the ability to bind Ca and promote hydroxyapatite (HAP) growth along the DNA backbone combined with their degradation and release of extracellular phosphate, a known promoter of osteogenic differentiation, make DNA-based biomaterials unlike other currently used materials. However, their use as biodegradable scaffolds for bone repair remains scarce.

Peptide-Decorated DNA Nanostructures Promote Site-Specific Hydroxyapatite Growth.

The guiding principle for mineralized tissue formation is that mineral growth occurs through the interaction of Ca and phosphate ions with extracellular matrix (ECM) proteins. Recently, nanoengineered DNA structures have been proposed as mimics to ECM scaffolds. However, these principles have not been applied to mineralized tissues.

Uniaxial Hydroxyapatite Growth on a Self-Assembled Protein Scaffold.

Biomineralization is a crucial process whereby organisms produce mineralized tissues such as teeth for mastication, bones for support, and shells for protection. Mineralized tissues are composed of hierarchically organized hydroxyapatite crystals, with a limited capacity to regenerate when demineralized or damaged past a critical size. Thus, the development of protein-based materials that act as artificial scaffolds to guide hydroxyapatite growth is an attractive goal both for the design of ordered nanomaterials and for tissue regeneration.

DNA nanostructures as templates for biomineralization.

Nature uses extracellular matrix scaffolds to organize biominerals into hierarchical structures over various length scales. This has inspired the design of biomimetic mineralization scaffolds, with DNA nanostructures being among the most promising. DNA nanotechnology makes use of molecular recognition to controllably give 1D, 2D and 3D nanostructures.

Nanostructure of mouse otoconia.

Mammalian otoconia of the inner ear vestibular apparatus are calcium carbonate-containing mineralized structures critical for maintaining balance and detecting linear acceleration. The mineral phase of otoconia is calcite, which coherently diffracts X-rays much like a single-crystal. Otoconia contain osteopontin (OPN), a mineral-binding protein influencing mineralization processes in bones, teeth and avian eggshells, for example, and in pathologic mineral deposits.

Homochirality in biomineral suprastructures induced by assembly of single-enantiomer amino acids from a nonracemic mixture.

Since Pasteur first successfully separated right-handed and left-handed tartrate crystals in 1848, the understanding of how homochirality is achieved from enantiomeric mixtures has long been incomplete. Here, we report on a chirality dominance effect where organized, three-dimensional homochiral suprastructures of the biomineral calcium carbonate (vaterite) can be induced from a mixed nonracemic amino acid system. Right-handed (counterclockwise) homochiral vaterite helicoids are induced when the amino acid L-Asp is in the majority, whereas left-handed (clockwise) homochiral morphology is induced when D-Asp is in the majority.

Nanostructure, osteopontin, and mechanical properties of calcitic avian eggshell.

Avian (and formerly dinosaur) eggshells form a hard, protective biomineralized chamber for embryonic growth-an evolutionary strategy that has existed for hundreds of millions of years. We show in the calcitic chicken eggshell how the mineral and organic phases organize hierarchically across different length scales and how variation in nanostructure across the shell thickness modifies its hardness, elastic modulus, and dissolution properties. We also show that the nanostructure changes during egg incubation, weakening the shell for chick hatching.

Chiral acidic amino acids induce chiral hierarchical structure in calcium carbonate.

Chirality is ubiquitous in biology, including in biomineralization, where it is found in many hardened structures of invertebrate marine and terrestrial organisms (for example, spiralling gastropod shells). Here we show that chiral, hierarchically organized architectures for calcium carbonate (vaterite) can be controlled simply by adding chiral acidic amino acids (Asp and Glu). Chiral, vaterite toroidal suprastructure having a 'right-handed' (counterclockwise) spiralling morphology is induced by L-enantiomers of Asp and Glu, whereas 'left-handed' (clockwise) morphology is induced by D-enantiomers, and sequentially switching between amino-acid enantiomers causes a switch in chirality.

New insights into the chemical and isotopic composition of human-body biominerals. I: Cholesterol gallstones from England and Greece.

We have analyzed gallstones from four patients of Europe and particularly from England (including samples from a mother and a daughter) and Greece. According to the XRD, FTIR, NMR and laser micro-Raman results the studied materials correspond to typical cholesterol monohydrate (ChM). The micro-morphology of cholesterol microcrystals was investigated by means of SEM-EDS.

Development of a pentaplex X-chromosomal short tandem repeat typing system and population genetic studies.

Quadruplex and pentaplex systems for polymerase chain reaction amplification of X-chromosomal short tandem repeats DXS101, HPRTB, DXS8377, DXS981 (STRX1) and DXS6789 were developed for automated profiling of liquid and membrane-bound DNA samples. Chinese, Japanese and Thai populations were typed using a quadruplex system, while German and Philippine populations were analyzed using a five-locus system. Out of 88 meioses studied in Philippine family samples at each locus, a possible one repeat deletion (allele 51 to 50) at DXS8377 was observed in a father-daughter pair.

Paclitaxel and gemcitabine combination in a biweekly schedule in patients with advanced non small-cell lung cancer: a phase I study.

Purpose: This phase I study was designed to determine the maximum tolerated dose (MTD) and dose limiting toxicities (DLTs) of the paclitaxel-gemcitabine combination in a biweekly schedule in chemotherapy-naive patients with advanced non small-cell lung cancer (NSCLC).

Patients And Methods: Treatment was administered on an outpatient basis every 2 weeks: paclitaxel over a 1-h IV infusion and gemcitabine as a 30-min IV infusion immediately following paclitaxel.

Results: Twenty-nine patients were treated at six different dose levels, ranging from paclitaxel 135-175 mg/m2 and gemcitabine 1,500-3,000 mg/m2.