A Fluorescent Silver(I) Carbene Complex with Anticancer Properties: Synthesis,Characterization, and Biological Studies

The silver(I) N-heterocyclic carbene (NHC) complex bis(1-(anthracen-9-ylmethyl)-3-ethylimidazol-2-ylidene) silver chloride ([Ag(EIA)₂]Cl), bearing two anthracenyl fluorescent probes, has been synthesized and characterized. [Ag(EIA)₂]Cl is stable in organic solvents and under physiological conditions, and shows potent cytotoxic effects in vitro toward human SH-SY5Y neuroblastoma cells. The interactions of [Ag(EIA)₂]Cl with a few model biological targets have been studied as well as its ability to be internalized in cells. The in vitro anticancer activity is apparently related to the level of drug internalization. Notably, [Ag(EIA)₂]Cl does not react with a few model proteins, but is capable of binding the C-terminal dodecapeptide of thioredoxin reductase hTrxR(488–499) and to strongly inhibit the activity of this enzyme. Binding occurs through an unconventional process leading to covalent binding of one or two carbene ligands to the C-terminal dodecapeptide with concomitant release of the silver cation. To the best of our knowledge, this mode of interaction is reported here for the first time for Ag(NHC)₂ complexes.     

Microwave Cavity Perturbation as a Tool for Laboratory In Situ Measurement of the Oxidation State of Three Way Catalysts

Three-way catalyst-based automotive exhaust gas aftertreatment is of high importance to meet today’s emission standards. To determine in situ the oxygen loading state of three-way catalysts, a microwave cavity perturbation method is used. In this study, it is investigated whether this measurement setup that had originally been described for full-sized catalysts can be transferred to a lab test bench using cores of 1″ diameter. The initial tests were successful and a high correlation between the oxygen loading degree dependent resonance frequency and the conversion was found. As an application example of the new in situ characterization technique, the steady state degree of oxidation of a three way catalyst was measured as a function of the exhaust stoichiometry. The experimental results are compared with the prediction of a recently published improved kinetic model that takes into account the oxidation of reduced ceria by H₂O and CO₂. It is shown that the experimental observations agree very well with this improved model. This result provides evidence that under typical operating conditions, the degree of oxidation of the three way catalyst is controlled by equilibrium effects.     

Environmental Pollution: A Tangible Risk for NAFLD Pathogenesis

The liver is crucial for human life, and the health of this organ often mirrors the health of the individual. The liver can be the target of several diseases, the most prevalent of which, as a consequence of development and changes in human lifestyles, is the nonalcoholic fatty liver disease (NAFLD). NAFLD is a multifactorial disease that embraces many histo-pathologic conditions and is highly linked to metabolic derangements. Technological progress and industrialization have also had the consequence of releasing pollutants in the environment, for instance pesticides or solvents, as well as by-products of discharge, such as the particulate matter. In the last decade, a growing body of evidence has emerged, shedding light on the potential impact of environmental pollutants on liver health and, in particular, on NAFLD occurrence. These contaminants have a great steatogenic potential and need to be considered as tangible NAFLD risk factors. There is an urgent need for a deeper comprehension of their molecular mechanisms of action, as well as for new lines of intervention to reduce their worldwide diffusion. This review wishes to sensitize the community to the effects of several environmental pollutants on liver health.     

Advanced Knowledge of Three Important Classes of Grape Phenolics: Anthocyanins,Stilbenes and Flavonols

Grape is qualitatively and quantitatively very rich in polyphenols. In particular, anthocyanins, flavonols and stilbene derivatives play very important roles in plant metabolism, thanks to their peculiar characteristics. Anthocyanins are responsible for the color of red grapes and wines and confer organoleptic characteristics on the wine. They are used for chemotaxonomic studies and to evaluate the polyphenolic ripening stage of grape. They are natural colorants, have antioxidant, antimicrobial and anticarcinogenic activity, exert protective effects on the human cardiovascular system, and are used in the food and pharmaceutical industries. Stilbenes are vine phytoalexins present in grape berries and associated with the beneficial effects of drinking wine. The principal stilbene, resveratrol, is characterized by anticancer, antioxidant, anti-inflammatory and cardioprotective activity. Resveratrol dimers and oligomers also occur in grape, and are synthetized by the vine as active defenses against exogenous attack, or produced by extracellular enzymes released from pathogens in an attempt to eliminate undesirable toxic compounds. Flavonols are a ubiquitous class of flavonoids with photo-protection and copigmentation (together with anthocyanins) functions. The lack of expression of the enzyme flavonoid 3′,5′-hydroxylase in white grapes restricts the presence of these compounds to quercetin, kaempferol and isorhamnetin derivatives, whereas red grapes usually also contain myricetin, laricitrin and syringetin derivatives. In the last ten years, the technological development of analytical instrumentation, particularly mass spectrometry, has led to great improvements and further knowledge of the chemistry of these compounds. In this review, the biosynthesis and biological role of these grape polyphenols are briefly introduced, together with the latest knowledge of their chemistry.     

Annealing temperature influence on sol-gel processed zirconium oxide thin films for electronic applications

A study of zirconium oxide (ZrO₂) thin films obtained by the non-alkoxide sol-gel method at different annealing temperatures, up to 450?°C, is presented. Morphological, compositional, and optical characterizations of zirconia thin films show high transparency and high bandgap, besides homogeneous and non-porous surface. Metal-insulating-metal (MIM) devices were assembled from this zirconia material for electrical characterizations and have shown high electric resistivity and high specific capacitance. A study of the thin film composition shows residues of S and Cl elements from the precursor solution that contributes for reduction of the dielectric constant of the zirconia thin films, even though they still present higher values when compared to SiO₂, which is a positive alternative to replace this oxide in electronic devices. A parallel study of MIM assembled on polymeric substrate and annealed at 100?°C also leads to positive results concerning high electrical insulating and capacitance. This study aims the understanding of the relations between annealing temperature and impurities found in sol-gel based thin films, as well as their relations to dielectric characteristics of zirconia thin films that impact the final properties of electronic devices, such as in field effect transistors.     

Plasmonic Photoresistor Based on Interconnected Metal-Semiconductor Grating

Metal-semiconductor nanostructures in various configurations are extensively used in photodetection, photocatalysis, and photovoltaics. For photodetection purposes, the working principle is straightforward; on illumination, generated charge carriers in excess lead to a decrease in resistance. Notably, using an interconnected metal-semiconductor grating, it is observed and now reported an opposite response, an increase in the resistance. Such photoresistors are fabricated through wrinkle structuring and oblique angle material deposition methods. It is found that the controlled wrinkling leads to large-area 1D periodic structures with coexisting cracking perpendicular to the grating direction—such cracks are used as connections between the two-point contact measurement through the associated gold layer deposition. An enhanced current reduction is further observed on photoexcitation for an additional deposition of an amorphous titania layer. Subsequently, a discussion on the mechanisms and interaction between hot electron injection, charge carrier recombination, and thermalization is presented. Supported by numerical modeling, the angle-resolved plasmonic modes with the photoresistance can be correlated. The ease of layered deposition of the materials allows one to extend the studies on cavity-based structures with sandwiched titania layers as hotspots. This simple, scalable, and robust fabrication method thus promises an efficient routeway toward photosensor development in which plasmon-mediated hot electrons play a crucial role.