Interfacial charge transfer and photocatalytic activity in a reverse designed Bi2O3/TiO2 core-shell

In this study, the electronic and photocatalytic properties of core-shell heterojunctions photocatalysts with reversible configuration of TiO₂ and Bi₂O₃ layers were studied. The core-shell nanostructure, obtained by efficient control of the sol-gel polymerization and impregnation method of variable precursors of semiconductors, makes it possible to study selectively the role of the interfacial charge transfer in each configuration. The morphological, optical, and chemical composition of the core-shell nanostructures were characterized by high-resolution transmission electron microscopy, UV-visible spectroscopy and X-ray photoelectron spectroscopy. The results show the formation of homogenous TiO₂ anatase and Bi₂O₃ layers with a thickness of around 10 and 8 nm, respectively. The interfacial charge carrier dynamic was tracked using time resolved microwave conductivity and transition photocurrent density. The charge transfer, their density, and lifetime were found to rely on the layout layers in the core-shell nanostructure. In optimal core-shell design, Bi₂O₃ collects holes from TiO₂, leaving electrons free to react and increase by 5 times the photocatalytic efficiency toward H₂ generation. This study provides new insight into the importance of the design and elaboration of optimal heterojunction based on the photocatalyst system to improve the photocatalytic activity.     

Novel N-Substituted 3-Aryl-4-(diethoxyphosphoryl)azetidin-2-ones as Antibiotic Enhancers and Antiviral Agents in Search for a Successful Treatment of Complex Infections

A novel series of N-substituted cis- and trans-3-aryl-4-(diethoxyphosphoryl)azetidin-2-ones were synthesized by the Kinugasa reaction of N-methyl- or N-benzyl-(diethyoxyphosphoryl)nitrone and selected aryl alkynes. Stereochemistry of diastereoisomeric adducts was established based on vicinal H3–H4 coupling constants in azetidin-2-one ring. All the obtained azetidin-2-ones were evaluated for the antiviral activity against a broad range of DNA and RNA viruses. Azetidin-2-one trans-11f showed moderate inhibitory activity against human coronavirus (229E) with EC₅₀ = 45 µM. The other isomer cis-11f was active against influenza A virus H1N1 subtype (EC₅₀ = 12 µM by visual CPE score; EC₅₀ = 8.3 µM by TMS score; MCC > 100 µM, CC₅₀ = 39.9 µM). Several azetidin-2-ones 10 and 11 were tested for their cytostatic activity toward nine cancerous cell lines and several of them appeared slightly active for Capan-1, Hap1 and HCT-116 cells values of IC₅₀ in the range 14.5–97.9 µM. Compound trans-11f was identified as adjuvant of oxacillin with significant ability to enhance the efficacy of this antibiotic toward the highly resistant S. aureus strain HEMSA 5. Docking and molecular dynamics simulations showed that enantiomer (3R,4S)-11f can be responsible for the promising activity due to the potency in displacing oxacillin at β-lactamase, thus protecting the antibiotic from undesirable biotransformation.     

Antifungal Effect of Mexican Oregano (Lippia berlandieri Schauer) Essential Oil on a Wheat Flour-Based Medium

The antimicrobial activity of oregano has been attributed mainly to the presence of volatile compounds found in its essential oil (EO), mainly carvacrol and thymol. The search for antimicrobial activity of oregano EO with different concentrations of thymol and carvacrol, can lead to products with a wider range of applications. The aim of this work was to describe the in vitro antifungal effect of Mexican oregano (Lippia berlandieri Schauer) EO fractions on the growth of Aspergillus, Penicillium, and Rhizopus sp. The Mexican oregano EO fractions studied had different concentrations of carvacrol, which decreased from fraction 1 to 5 (81% to 23%), while thymol content increased from 3% to 64%. Fungal inhibition was evaluated on a wheat flour-based medium with EO fractions concentrations ranging from 50 to 200 mg/kg. Radial growth curves were fitted using the modified Gompertz model (R(2) (adj) = 0.989 ± 0.01). No significant differences (P > 0.05) were found with the different composition of the Mexican oregano EO fractions; nevertheless, fraction concentration presented significant (P < 0.05) mold inhibition as concentration increased. Rhizopus sp. (Rh18) showed a linear reduction on specific growth rate, on the maximum mold growth at the stationary phase, and an increase in the lag time as the concentration of the oregano EO increased; mold growth inhibition were achieved at 150 mg/kg in fractions 1 to 4, and at 100 mg/kg for fraction 5. Aspergillus sp. (As6) and Penicillium sp. (Pe36) were inhibited at 150 and 200 mg/kg, respectively. Results obtained suggest that Mexican oregano EO (Lippia berlandieri Schauer) compounds could be used as antimicrobial agents to prevent fungal growth in bakery products.     

Flavonoids from the fruits of Nepalese sumac (Rhus parviflora) attenuate glutamate-induced neurotoxicity in HT22 cells

Nepalese sumac (Rhus parviflora) is a wild edible fruit used for the treatment of various ailments including neurological complications and stomach disorders in the traditional medicinal system of south Asia (Ayurveda). Four flavonoids were isolated from ethyl acetate (EtOAc) fraction of Nepalese sumac fruits and their chemical structures were determined on the basis of NMR, fast atom bombardment mass spectrometry (FAB/MS), and IR. The efficiency of isolated compounds in attenuating glutamateinduced cell death in an immortalized mouse hippocampal cell line (HT-22) and inhibition of cycline dependent kinase 5 (Cdk5) were investigated. Among the compounds, flavanols, fustin (1) and taxifolin (2), an aurone, aureusidin (3), and a biflavonoid, agathisflavone (4) were found to have protective effect against glutamate induced oxidative injury in HT22 cells. Aureusidin (3), a Cdk5/p25 inhibitor (IC₅₀ 3.5 μM), was the most potent neuroprotector with an EC₅₀ value of 11.90 μM.     

Digital Image Analysis Applied to Tumor Cell Proliferation,Aggressiveness, and Migration-Related Protein Synthesis in Neuroblastoma 3D Models

Patient-derived cancer 3D models are a promising tool that will revolutionize personalized cancer therapy but that require previous knowledge of optimal cell growth conditions and the most advantageous parameters to evaluate biomimetic relevance and monitor therapy efficacy. This study aims to establish general guidelines on 3D model characterization phenomena, focusing on neuroblastoma. We generated gelatin-based scaffolds with different stiffness and performed SK-N-BE(2) and SH-SY5Y aggressive neuroblastoma cell cultures, also performing co-cultures with mouse stromal Schwann cell line (SW10). Model characterization by digital image analysis at different time points revealed that cell proliferation, vitronectin production, and migration-related gene expression depend on growing conditions and are specific to the tumor cell line. Morphometric data show that 3D in vitro models can help generate optimal patient-derived cancer models, by creating, identifying, and choosing patterns of clinically relevant artificial microenvironments to predict patient tumor cell behavior and therapeutic responses.     

Ductile/brittle PA6/PS system: Effect of carbon nanoplatelets-modified interface on performance

Addition of rigid PS to ductile PA6 can lead to higher toughness provided plastic deformation of PS is achieved. The current study deals with upgrading of this system by graphene, graphene oxide (GO), and GO with grafted polystyrene (GO-g-PS). Low amount of these carbon nanoplatelets can enhance performance of the PA/PS 90/10 system with the best-balanced properties achieved with GO-g-PS by unique combination of reinforcement with the favorable effect of the GO-g-PS-modified interface on plastic deformation of the PS phase causing higher impact resistance. Simultaneous linking of PA chains and hydrogen bonding causes “anchoring” of PS inclusions in the PA6 phase. This results in support of hydrostatic pressure evolution during loading and thus extensive yielding of PS. Another positive effect is reduction of pullout of in situ formed fibrous inclusions, which is different from rigid short-fiber composites. The study highlights high potential of GO modified with polymer chains to upgrade polymer systems via tailoring the interface.     

Spherical indentation of a transversely isotropic elastic half-space reinforced with a thin layer

The frictionless spherical indentation test is considered for a transversely isotropic elastic half-space reinforced with a thin layer whose flexural stiffness is negligible compared to its tensile stiffness. It is assumed that the deformation of the reinforcing layer can be treated as the generalized plane stress state. Closed-form analytical approximate equations for the maximum contact pressure, contact radius, and contact force are presented. The isotropic case is considered in detail.     

Phytosterols and their extraction from various plant matrices using supercritical carbon dioxide: a review

Phytosterols provide important health benefits: in particular, the lowering of cholesterol. From environmental and commercial points of view, the most appropriate technique has been searched for extracting phytosterols from plant matrices. As a green technology, supercritical fluid extraction (SFE) using carbon dioxide (CO₂) is widely used to extract bioactive compounds from different plant matrices. Several studies have been performed to extract phytosterols using supercritical CO₂ (SC‐CO₂) and this technology has clearly offered potential advantages over conventional extraction methods. However, the efficiency of SFE technology fully relies on the processing parameters, chemistry of interest compounds, nature of the plant matrices and expertise of handling. This review covers SFE technology with particular reference to phytosterol extraction using SC‐CO₂. Moreover, the chemistry of phytosterols, properties of supercritical fluids (SFs) and the applied experimental designs have been discussed for better understanding of phytosterol solubility in SC‐CO₂. © 2014 Society of Chemical Industry