Oren Meiron

Solubility and Bioavailability of Stabilized Amorphous Calcium Carbonate

Since its role in the prevention of osteoporosis in humans was proven some 30 years ago, calcium bioavailability has been the subject of numerous scientific studies. Recent technology allowing the production of a stable amorphous calcium carbonate (ACC) now enables a bioavailability analysis of this unique form of calcium. This study thus compares the solubility and fractional absorption of ACC, ACC with chitosan (ACC‐C), and crystalline calcium carbonate (CCC). Solubility was evaluated by dissolving these preparations in dilute phosphoric acid. The results demonstrated that both ACC and ACC‐C are more soluble than CCC. Fractional absorption was evaluated by intrinsically labeling calcium carbonate preparations with 45Ca, orally administrated to rats using gelatin capsules. Fractional absorption was determined by evaluating the percentage of the administrated radioactive dose per milliliter that was measured in the serum, calcium absorption in the femur, and whole‐body retention over a 34‐hour period. Calcium serum analysis revealed that calcium absorption from ACC and ACC‐C preparations was up to 40% higher than from CCC, whereas retention of ACC and ACC‐C was up to 26.5% higher than CCC. Absorbed calcium in the femurs of ACC‐administrated rats was 30% higher than in CCC‐treated animals, whereas 15% more calcium was absorbed following ACC‐C treatment than following CCC treatment. This study demonstrates the enhanced solubility and bioavailability of ACC over CCC. The use of stable ACC as a highly bioavailable dietary source for calcium is proposed based on the findings of this study.

Understanding the formation mechanism and the 3D structure of Mo(SxSe1−x)2 nanoflowers

Nanoflowers of layered materials are promising building blocks for photocatalysis due to their unique morphology and exposed edges. Colloidal synthesis of MoS2, MoSe2 and their alloys was used to produce fine nanoflowers with tunable composition. The alloys follow Vegards law, showing homogeneous composition. They exhibit fully tunable optical properties, where the exciton positions change with alloy composition. Samples annealed under vacuum retain their fine morphology and their composition, which closely follows the feed ratio. Time series analysis was used to investigate the formation mechanism. The results support a growth mechanism of fast-precipitating amorphous material, followed by crystallization of a few layers of small sheets, which curl and tangle around themselves. Electron tomography of the time series reveals a perforated structure without a dense core, supporting the suggested growth mechanism. These structures show multiple exposed edge sites, making them promising materials for applications such as photocatalysis.

Increased calcium absorption from synthetic stable amorphous calcium carbonate: double-blind randomized crossover clinical trial in postmenopausal women.

Calcium supplementation is a widely recognized strategy for achieving adequate calcium intake. We designed this blinded, randomized, crossover interventional trial to compare the bioavailability of a new stable synthetic amorphous calcium carbonate (ACC) with that of crystalline calcium carbonate (CCC) using the dual stable isotope technique. The study was conducted in the Unit of Clinical Nutrition, Tel Aviv Sourasky Medical Center, Israel. The study population included 15 early postmenopausal women aged 54.9 ± 2.8 (mean ± SD) years with no history of major medical illness or metabolic bone disorder, excess calcium intake, or vitamin D deficiency. Standardized breakfast was followed by randomly provided CCC or ACC capsules containing 192 mg elemental calcium labeled with 44Ca at intervals of at least 3 weeks. After swallowing the capsules, intravenous CaCl2 labeled with 42Ca on was administered on each occasion. Fractional calcium absorption (FCA) of ACC and CCC was calculated from the 24‐hour urine collection following calcium administration. The results indicated that FCA of ACC was doubled (± 0.96 SD) on average compared to that of CCC (p < 0.02). The higher absorption of the synthetic stable ACC may serve as a more efficacious way of calcium supplementation.

Correlating the Structure and Composition of 2D Materials with Their Catalytic Activity

Nanostructures are one of the most extensively researched systems in nanoscience. Various materials are investigated due to their size dependent optical properties or due to their enhanced functionality as catalysts. Although they have been extensively researched for a few decades now, even today new fabrication routes are still explored to improve properties and to gain precise control of their structure. While reports on the optical properties of single particles are available, the quantitative characterization of atomic order on a single particle level and the growth mechanism that resulted in that specific rearrangement, are still generally missing. The majority of characterization procedures are performed on ensembles that average properties and may hinder the understanding of fundamental aspects in the colloidal synthesis.