Silicone composites containing stabilized silver clusters or nanoparticles

Silver nanoparticles are of high importance due to their electrical, magnetic, and optical properties, as well as catalytic and biocidal activity that are superior to the bulk silver and other metals. To prepare certain devices, generally, silver is incorporated into a matrix either as preformed or in situ‐generated particles. Silver nanoparticles were generated in situ into a silicone matrix formed by cohydrolysis of the mixture of silanes, each of them having a certain role: dimethyldiethoxysilane (DMDES) as a precursor for highly flexible polydimethylsiloxane, methyltriethoxysilane (MTES) as a cross‐linker highly compatible with polydimethylsiloxane, and 3‐aminopropyltriethoxysilane as a stabilizer, since it can readily complex to silver atoms through its amine functionality. Dimethylformamide (DMF) was used as a solvent for the silver nitrate and reducing agent. The samples were investigated both in sol state and as aged coating films deposited on glass substrate. The complexation of the silver and the matrix formation were emphasized by FTIR. The size of the formed silicone particles encapsulating silver was estimated by dynamic light scattering (DLS) (about 100 nm) in sol and by AFM in film (about 90 nm). The formation of the clusters or nanoparticles depending on the ratio between the reducing and complexing agents was evidenced by UV–Vis absorption spectra. Thus, it would create conditions to stop and isolate clusters at the desired size by precise control of the experimental conditions. The composites could be used alone as antibacterial‐coating materials but also, porous silica having incorporated silver clusters with potential applicability in catalysis may result after their calcination. Copyright © 2010 John Wiley & Sons, Ltd.     

Process Intensification of Emulsion Polymerization in the Continuous Taylor Reactor

Summary: Process intensification is investigated by the emulsion polymerization of styrene in the continuous Taylor reactor. The result is an increase in space time yield up to a factor 200 in comparison to a semi-batch polymerization process. This is obtained by a fast emulsion polymerization with a mean residence time, which is reduced to 60 seconds. The article presented the results of the process and the economical aspects of the Taylor reactor plant.     

GD3- and O-acetylated GD3-gangliosides in the GM2 synthase-deficient mouse brain and their immunohistochemical localization

Gangliosides in the brain of the knockout mouse deficient in the activity of β1,4 N-acetylgalactosaminyl transferase (β1,4 GalNAc-T)(GM2 synthase) consisted of nearly exclusively of GM3- and GD3-gangliosides as expected from the known substrate specificity of the enzyme and in confirmation of the initial reports from two laboratories that generated the mutant mouse experimentally. The total molar amount of gangliosides was approximately 30% higher in the mutant mouse brain than that in the wild-type brain. However, contrary to the initial reports, one-fourth of total GD3-ganglioside was O-acetylated. It reacted positively with an anti-O-acetylated GD3 monoclonal antibody and disappeared with a corresponding increase in GD3-ganglioside after mild alkaline treatment. The absence of O-acetylated GD3 in the initial reports can be explained by the saponification step included in their analytical procedures. Although quantitatively much less and identification tentative, we also detected GT3 and O-acetylated GT3. Anti-GD3 and anti-O-acetylated GD3 monoclonal antibodies gave positive reactions in the brain of mutant mouse as expected from the analytical results. Either antibody barely stained wild-type brain except for immunoreactivity of GD3 in the cerebellar Purkinje cells. The distributions of GD3 and O-acetylated GD3 in the brain of mutant mouse were similar but differential localization was noted in the cerebellar Purkinje cells and cerebral cortex.     

Hexachloroantimonate(V) mit Nitroderivaten als Liganden, 3. Mitt.: Komplexe Verbindungen mit dreiwertigen Metallen

Complex compounds of trivalent metal chlorides (AlCl₃, CrCl₃, FeCl₃) are described, which had been obtained in a double complexation reaction in CCl₄ as a solvent with nitro compounds and SbCl₅:M ^III(C₆H₅NO₂) _m (SbCl₆)₃ (m=3,6),M ₂ ^III(C₆H₅NO₂)₄(SbCl₆)₄ and Al(-C₁₀H₇NO₂)₃(SbCl₆)₃. Synthesis, analytical results and i.r. spectra are discussed.     

Bioanalysis of pentoxifylline and related metabolites in plasma samples through LC‐MS/MS

Analytical aspects related to the assay of pentoxifylline (PTX), lisofylline (M1) and carboxypropyl dimethylxanthine (M5) metabolites are discussed through comparison of two alternative analytical methods based on liquid chromatography separation and atmospheric pressure electrospray ionization tandem mass spectrometry detection. One method is based on a ‘pure’ reversed‐phase liquid chromatography mechanism, while the second one uses the additional polar interactions with embedded amide spacers linking octadecyl moieties to the silicagel surface (C‐18 Aqua stationary phase). In both cases, elution is isocratic. Both methods are equally selective and allows separation of unknowns (four species associated to PTX, two species associated to M1) detected through specific mass transitions of the parent compounds and owning respective structural confirmation. Plasma concentration–time patterns of these compounds follow typical metabolic profiles. It has been advanced that in‐vivo formation of conjugates of PTX and M1 is possible, such compounds being cleaved back to the parent ones within the ion source. The first method was associated with a sample preparation procedure based on plasma protein precipitation by strong organic acid addition. The second method used protein precipitation by addition of a water miscible organic solvent. Both analytical methods were fully validated and used to assess bioequivalence between a prolonged release generic formulation and the reference product, under multidose and single dose approaches. Copyright © 2009 John Wiley & Sons, Ltd.     

New basic catalysts obtained from layered double hydroxides nanocomposites

A new route for the preparation of basic mixed oxides using nanocomposite precursors obtained from layered double hydroxides (LDH) was investigated. These nanocomposites have been prepared by intercalation of negatively charged guest entities containing Ca²⁺, Sr²⁺, Ba²⁺ or La³⁺ cations in the interlayer space of host Mg/Al LDH by anionic exchange. The guest entities have been previously prepared by complexation of the required cations in the presence of edta or citrate chelating anions. Intercalation of [Mⁿ⁺(edta)]^(4?n)? or [La(cit)OH]^? complexes is proved by elemental analysis, XRD analysis and FT-IR spectroscopy. However, in order to satisfy the charge equilibrium in the materials, (edta)^4? and (citrate)^3? species are also co-intercalated in the nanocomposites. The basic properties of the mixed oxides obtained after thermal decomposition of the nanocomposites precursors were evaluated in the disproportionation of 2-methyl-3-butyn-2-ol (MBOH) and the transesterification of 1-phenylethanol with diethylcarbonate (DEC). The Sr- and Ba-containing mixed oxides exhibit basicity close to the one of MgO and Mg(La)O mixed oxides. A comparative study of the reactivity of La-containing mixed oxides obtained following different preparation routes, i.e. coprecipitation or anionic exchange, allows to conclude that the nanocomposite route led to the most active samples.     

Synthesis of Enantiopure Sulfonimidamides and Elucidation of Their Absolute Configuration by Comparison of Measured and Calculated CD Spectra and X‐Ray Crystal Structure Determination

Straightforward syntheses of enantiopure N‐benzoyl‐ and N‐tert‐butyloxycarbonyl‐protected sulfonimidamides, which can be used as building blocks in newly designed catalysts, are presented. Key synthetic step is a dynamic resolution of a racemic sulfinic acid sodium salt. All subsequent transformations proceed stereospecifically. The absolute configurations at the sulfur atoms of both sulfonimidamides were determined by comparison of measured and calculated CD spectra. An X‐ray crystal structure determination of a sulfonimidoylguanidine derivative confirmed this result.     

Microfluidics in macro-biomolecules analysis: macro inside in a nano world

Use of microfluidic devices in the life sciences and medicine has created the possibility of performing investigations at the molecular level. Moreover, microfluidic devices are also part of the technological framework that has enabled a new type of scientific information to be revealed, i.e. that based on intensive screening of complete sets of gene and protein sequences. A deeper bioanalytical perspective may provide quantitative and qualitative tools, enabling study of various diseases and, eventually, may offer support for the development of accurate and reliable methods for clinical assessment. This would open the way to molecule-based diagnostics, i.e. establish accurate diagnosis and disease prognosis based on identification and/or quantification of biomacromolecules, for example proteins or nucleic acids. Finally, the development of disposable and portable devices for molecule-based diagnosis would provide the perfect translation of the science behind life-science research into practical applications dedicated to patients and health practitioners. This review provides an analytical perspective of the impact of microfluidics on the detection and characterization of bio-macromolecules involved in pathological processes. The main features of molecule-based diagnostics and the specific requirements for the diagnostic devices are discussed. Further, the techniques currently used for testing bio-macromolecules for potential diagnostic purposes are identified, emphasizing the newest developments. Subsequently, the challenges of this type of application and the status of commercially available devices are highlighted, and future trends are noted.     

Microorganism response to atmospheric pressure helium plasma DBD treatment

The effect of an atmospheric pressure plasma dielectric barrier discharge on some microorganisms was investigated, due to the possible extent of plasma applications in controlling microbial contamination. The present investigation involved both Gram-positive and Gram-negative germs – bacteria and yeasts – treated in helium plasma (asymmetric dielectric barrier discharge) for various time durations between 25 s and 100 s. Circular growth inhibition zones were measured for two distances between the discharge electrodes, the correlations with the plasma treatment time being analyzed. Differences between the sensitivities of the four tested microorganisms to helium plasma in open atmosphere were discussed.