Reversible collapse and Mg release of de- and rehydroxylated homoionic cis-vacant montmorillonites

Homoionic Na⁺, Ca²⁺, Sr²⁺, Li⁺, Cu²⁺ and Zn²⁺ samples of the <2 μm fraction of a cis-vacant montmorillonite from Linden (Bavaria) were steam treated at 200°C (≈1.5 MPa), 240°C (≈3.3 MPa) and 300°C (≈8.0 MPa) after dehydroxylation at temperatures up to 630°C. Cation exchange capacity (CEC) measurements, determination of exchangeable cations and X-ray diffraction (XRD), supplemented by thermoanalytical investigations of the evolved water in a thermobalance linked to a mass spectrometer, infrared (IR) and electron spin resonance (ESR) spectroscopy were employed to obtain information about the state of expandability and structural changes of swellable montmorillonite and the sites of interlayer and octahedral cations after heating and rehydroxylation.The XRD pattern of the initial samples showed a well-defined (001) reflection according to the interlayer cation and its hydration state under laboratory atmosphere. After dehydroxylation the pattern exhibited (001) reflections between 9.6 and 9.8 Å, corresponding to a collapsed structure for all samples. The Na⁺-, Ca²⁺- and Sr²⁺-rich montmorillonites regained partial expandability after rehydroxylation at 200°C and full expandability after rehydroxylation at 300°C if the dehydroxylation temperature was less than 630°C. Rehydroxylation at 300°C of the Cu²⁺- and Zn²⁺-rich montmorillonites did not cause reexpansion, whereas the Li⁺-rich samples recovered a partial swellability after rehydroxylation at 240°C and nearly the full swellability after rehydroxylation at 300°C.The Li⁺-, Cu²⁺- and Zn²⁺-rich samples underwent a strong CEC reduction due to migration of the interlayer cations into the 2:1 layer before dehydroxylation started. After rehydroxylation under water steam Cu²⁺- and Zn²⁺-rich samples released 16–30 meq/100 g of Mg²⁺ from the structure, increasing with the steam temperature. Mg²⁺ release was not observed for the Li⁺-rich montmorillonite.     

Development of a solid self-microemulsifying drug delivery system (SMEDDS) for solubility enhancement of naproxen

Context: Comparative evaluation of liquid and solid self-microemulsifying drug delivery systems (SMEDDS) as promising approaches for solubility enhancement.

Objective: The aim of this work was to develop, characterize, and evaluate a solid SMEDDS prepared via spray-drying of a liquid SMEDDS based on Gelucire® 44/14 to improve the solubility and dissolution rate of naproxen.

Material and methods: Various oils and co-surfactants in combination with Gelucire® 44/14 were evaluated during excipient selection study, solubility testing, and construction of (pseudo)ternary diagrams. The selected system was further evaluated for naproxen solubility, self-microemulsification ability, and in vitro dissolution of naproxen. In addition, its transformation into a solid SMEDDS by spray-drying using maltodextrin as a solid carrier was performed. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to evaluate the physical characteristics of the solid SMEDDS obtained.

Results: The selected formulation of SMEDDS was comprised of Miglyol 812®, Peceol?, Gelucire® 44/14, and Solutol® HS 15. The liquid and solid SMEDDS formed a microemulsion after dilution with comparable average droplet size and exhibited uniform droplet size distribution. In the solid SMEDDS, liquid SMEDDS was adsorbed onto the surface of maltodextrin and formed smooth granular particles with the encapsulated drug predominantly in a dissolved state and partially in an amorphous state. Overall, incorporation of naproxen in SMEDDS, either liquid or solid, resulted in improved solubility and dissolution rate compared to pure naproxen.

Conclusion: This study indicates that a liquid and solid SMEDDS is a strategy for solubility enhancement in the future development of orally delivered dosage forms.     

The Effect of Composition on the Optical Properties and Hardness of Transparent Al‐rich MgO·nAl2O3 Spinel Ceramics

The study investigates the transmittance and hardness of Al‐rich spinel ceramics (MgO·nAl₂O₃, 1 ≤ n ≤ 2.5) prepared by reaction air sintering (up to closed porosity) of different ratios of fine and coarse‐grained commercial Al₂O₃ and MgO raw powders completed by subsequent hot isostatic pressing (HiP). Different compositions give rise to a wide range of presintering temperatures. With starting compositions 1 ≤ n ≤ 1.5, presintering results in a formation of single‐phase spinel, in which the excess of Al is solved. With higher Al contents (n > 1.5), however, a biphasic ceramic of stoichiometric MgAl₂O₄ and residual alumina is formed first. This excess alumina is incorporated into the spinel lattice during the final HiP at a temperature of 1750°C. Single‐phase, highly transparent spinel is obtained by increasing the Al‐content up to n = 2.5, which gives about 85% in‐line transmittance in the visible range of light and about 63% at a UV wavelength of 200 nm. Whereas the optical properties can be improved, the hardness (HV1) slightly decreases with increasing Al content. Depending on the raw powders, the hardness of samples prepared by finer powders tend to higher values enabled by the development of a bimodal microstructure with a finer grain fraction (≤2 μm) between coarser grains (≤156 μm). In contrast, samples made of coarser powders need higher sintering temperatures and exhibit, then, a monomodal microstructure of very large grains (≤622 μm) only.     

Prototype and Chimera-Type Galectins in Placentas with Spontaneous and Recurrent Miscarriages

Galectins are galactose binding proteins and, in addition, factors for a wide range of pathologies in pregnancy. We have analyzed the expression of prototype (gal-1, -2, -7, -10) and chimera-type (gal-3) galectins in the placenta in cases of spontaneous abortions (SPA) and recurrent abortions (RA) in the first trimester. Fifteen placental samples from healthy pregnancies were used as a control group. Nine placentas were examined for spontaneous abortions, and 12 placentas for recurrent abortions. For differentiation and evaluation of different cell types of galectin-expression in the decidua, immunofluorescence was used. For all investigated prototype galectins (gal-1, -2, -7, -10) in SPA and RA placenta trophoblast cells the expression is significantly decreased. In the decidua/extravillous trophoblast only gal-2 expression was significantly lowered, which could be connected to its role in angiogenesis. In trophoblasts in first-trimester placentas and in cases of SPA and RA, prototype galectins are altered in the same way. We suspect prototype galectins have a similar function in placental tissue because of their common biochemical structure. Expression of galectin 3 as a chimera type galectin was not found to be significantly altered in abortive placentas.     

Laser pyrolyzed organosilazane-based Al/ZrO2 composite coating on stainless steel: Resulting microstructure and mechanical properties

Protective ceramic-based coatings are frequently the most suitable solutions for problems like corrosion and wear. It has been shown that the precursor technology is suitable for the preparation of ceramic coatings by pyrolysis in a furnace. However, the required high temperature for the preparation of the ceramic coatings limits this approach to high temperature-resistant substrates. A very innovative approach to overcome this restriction is the use of laser radiation as a thermal source for the pyrolysis of the preceramic polymer. In this paper, we report on a coating system, for steel substrates, consisting of a polysilazane (Durazane 2250) bond coat and a hard and dense top-coat composed of an organosilazane (Durazane 1800) with tetragonal ZrO₂ particles and aluminum flakes as fillers pyrolyzed using Nd:YVO₄ laser. The aluminum fillers led to a significant increase in absorption of the laser energy leading to the formation of a dense coating with a thickness up to 20 μm and a mainly cellular/columnar-dendritic microstructure. The microstructure, mechanical, and tribological behaviors of these composite coatings are reported and compared to those of laser pyrolyzed glass/ZrO₂-filled polysilazane-based coatings reported in the literature.     

Small Prokaryotic DNA-Binding Proteins Protect Genome Integrity throughout the Life Cycle

Genomes of all organisms are persistently threatened by endogenous and exogenous assaults. Bacterial mechanisms of genome maintenance must provide protection throughout the physiologically distinct phases of the life cycle. Spore-forming bacteria must also maintain genome integrity within the dormant endospore. The nucleoid-associated proteins (NAPs) influence nucleoid organization and may alter DNA topology to protect DNA or to alter gene expression patterns. NAPs are characteristically multifunctional; nevertheless, Dps, HU and CbpA are most strongly associated with DNA protection. Archaea display great variety in genome organization and many inhabit extreme environments. As of yet, only MC1, an archaeal NAP, has been shown to protect DNA against thermal denaturation and radiolysis. ssDNA are intermediates in vital cellular processes, such as DNA replication and recombination. Single-stranded binding proteins (SSBs) prevent the formation of secondary structures but also protect the hypersensitive ssDNA against chemical and nuclease degradation. Ionizing radiation upregulates SSBs in the extremophile Deinococcus radiodurans.     

Effects of organic and conventional growth systems on the content of carotenoids in carrot roots, and on intake and plasma status of carotenoids in humans

BACKGROUND: The demand for organic food products has increased during the last decades due to their probable health effects, among others. A higher content of secondary metabolites such as carotenoids in organic food products has been claimed, though not documented, to contribute to increased health effects of organic foods. The aim was to study the impact of organic and conventional agricultural systems on the content of carotenoids in carrots and human diets. In addition, a human cross‐over study was performed, measuring the plasma status of carotenoids in humans consuming diets made from crops from these agricultural systems. RESULTS: The content of carotenoids in carrot roots and human diets was not significantly affected by the agricultural production system or year, despite differences in fertilisation strategy and levels. The plasma status of carotenoids increased significantly after consumption of the organic and conventional diets, but no systematic differences between the agricultural production systems were observed. CONCLUSION: The expected higher content of presumed health‐promoting carotenoids in organic food products was not documented in this study. Copyright © 2011 Society of Chemical Industry     

Influence of Molybdenum Silicide Additions on High-Temperature Oxidation Resistance of Silicon Nitride Materials

The influence of additions of molybdenum disilicide (MoSi₂) on the microstructure and the mechanical properties of a silicon nitride (Si₃N₄) material, with neodymium oxide (Nd₂O₃) and aluminum nitride (AIN) as sintering aids, was studied. The composites, containing 5, 10, and 17.6 wt% MoSi₂, were fabricated by hot pressing. All materials exhibited a similar phase composition, detected by X-ray diffractometry. Up to MoSi₂ additions of 10 wt%, mechanical properties such as strength, fracture toughness, or creep at 1400°C were not affected significantly, in comparison to that of monolithic Si₃N₄. The oxidation resistance of the composites, in terms of weight gain, degraded. After 1000 h of oxidation at 1400° and 1450°C in air, a greater weight gain (by a factor of approximately three) was obtained, in comparison to that of the material without MoSi₂. Nevertheless, after 1000 h of oxidation, the degradation in strength of the composites was considerably less severe than that of the material without MoSi₂. An additional layer was formed, caused by processes at the surface of the Si₃N₄ material, preventing the formation of pores, cracks, or glassy-phase-rich areas, which are common features of oxidation damage in Si₃N₄ materials. This surface layer, containing Mo₅Si₃ and silicon oxynitride (Si₂ON₂), was the result of reactions between MoSi₂, Si₃N₄, and the oxygen penetrating by diffusion into the material during the hightemperature treatment.