Tunable colors and conductivity by electroless growth of Cu/Cu2O particles on sol-gel modified cellulose

Nano Research - Development of colored surfaces by formation of nano-structured aggregates is a widely used strategy in nature to color lightweight structures (e.g. butterflies) without the use of...     

Detection of Mercapturic Acids and Nucleoside Adducts in Blood,Urine and Feces of Rats Treated with Metabolites of Methylpyrene

The carcinogen 1-methylpyrene (MP) is metabolized via 1-hydroxymethylpyrene (HMP) to a sulfuric acid ester (SMP), which can covalently bind to nucleophiles such as glutathione and DNA. These primary reaction products may be processed to 1-methylpyrenyl mercapturic acid (MPMA) and free nucleoside adducts [e.g. N ²?(1-methylpyrenyl)-deoxyguanosine, MPdG], and then be excreted. MPMA may be considered as a marker for the amount of SMP which was detoxified, whereas MPdG represents that part which underwent uncontrolled reactions with tissue constituents. We have designed sensitive HPLC-MS/MS methods to determine levels of MPMA and MPdG in biological samples. Shortly after administration of HMP to rats, MPMA was detected in blood and was then excreted in urine (> 70 %) and feces (> 30 %), chiefly within 24 h. The level of urinary MPMA was higher in females than in males. MPdG was detected in urine of rat treated with SMP. Future investigations will focus on factors which modify the ratio of the excreted amounts of MPdG and MPMA in animals treated with MP or its metabolites.     

Testing Metal‐Oxide Nanomaterials for Human Safety

Nanomaterials can display distinct biological effects compared with bulk materials of the same chemical composition. The physico‐chemical characterization of nanomaterials and their interaction with biological media are essential for reliable studies and are reviewed here with a focus on widely used metal oxide and carbon nanomaterials. Available rat inhalation and cell culture studies compared to original results suggest that hazard potential is not determined by a single physico‐chemical property but instead depends on a combination of material properties. Reactive oxygen species generation, fiber shape, size, solubility and crystalline phase are known indicators of nanomaterials biological impact. According to these properties the summarized hazard potential decreases in the order multi‐walled carbon nanotubes >> CeO₂, ZnO > TiO₂ > functionalized SiO₂ > SiO₂, ZrO₂, carbon black. Enhanced understanding of biophysical properties and cellular effects results in improved testing strategies and enables the selection and production of safe materials.     

On the Lifecycle of Nanocomposites: Comparing Released Fragments and their In‐Vivo Hazards from Three Release Mechanisms and Four Nanocomposites

Nanocomposites are the dominating class of nanomaterials to come into consumer contact, and were in general assumed to pose low risk. The first data is now emerging on the exposure from nanocomposites, but little is yet known about their hypothetical nanospecific physiological effects, giving ample room for speculation. For the first time, this comprehensive study addresses these aspects in a systematic series of thermoplastic and cementitious nanocomposite materials. Earlier reports that ‘chalking’, the release of pigments from weathered paints, also occurs for nanocomposites, are confirmed. In contrast, mechanical forces by normal consumer use or do‐it‐yourself sanding do not disrupt nanofillers (nanoparticles or nanofibers) from the matrix. Detailed evidence is provided for the nature of the degradation products: no free nanofillers are detected up to the detection threshold of 100 ppm. Sanding powders measuring 1 to 80 μm in diameter are identified with the original material, still containing the nanofillers. The potential hazard from aerosols generated by sanding nanocomposites up to the nuisance dust limit is also investigated. In‐vivo instillation in rats is used to quantify physiological effects on degradation products from abraded nanocomposites, in comparison to the abraded matrix without nanofiller and to the pure nanofiller. In this pioneering and preliminary evaluation, the hazards cannot be distinguished with or without nanofiller.     

Untersuchung über die Beständigkeit von Tributylzinoxid im Holz

Due to its excellent biocidic properties, tributyltinoxide (TBTO) has been used for several years in a wide range of protective applications, especially as a wood protecting agent. In the literature, TBTO is often referred to as being quickly degraded by UV-light and having a high rate of evaporation. Analytical and fungicical tests carried out on TBTO-treated spruce wood, halfburied for 9 years, show that stabilized TBTO is degraded only to a small amount by the various influences during outside exposure.     

Sulfotransferase-mediated activation of mutagens studied using heterologous expression systems

Sulfation is a common final step in the biotransformation of xenobiotics and is traditionally associated with inactivation. However, the sulfate group is electron-withdrawing and may be cleaved off heterolytically in some molecules leading to electrophilic cations which may form adducts with DNA and other important cellular structures. Since endogenous sulfotransferases do not appear to be expressed in indicator cells of standard mutagenicity tests, rat and human sulfotransferases have been stably expressed in his- Salmonella typhimurium strain TA1538 and Chinese hamster V79 cells. Using these recombinant indicator cells, sulfotransferase-dependent genotoxic activities were detected with N-hydroxy-2-acetylaminofluorene, 2-acetylaminofluorene (in the presence of co-expressed rat cytochrome P450 1A2), hycanthone, 1'-hydroxysafrole, alpha-hydroxytamoxifen and various benzylic alcohols derived from polycyclic aromatic hydrocarbons. In several cases, it was critical that the reactive sulfuric acid conjugates were formed directly within the indicator cells, owing to the inefficient penetration of cell membranes. In other cases, spontaneous benzylic substitution reactions with medium components, such as halogenide ions or amino acids, led to secondary, membrane-penetrating reactive species. Different sulfotransferases, including related forms from rat and human, substantially differed in their substrate specificity towards the investigated promutagens. It is known that some sulfotransferases are expressed with high tissue and cell type specificities. This site-dependent expression together with the limitations in the distribution of reactive sulfuric acid conjugates may explain organotropic effects of compounds activated by this metabolic pathway.     

Benzylic Sulfuric Acid Esters React with Diverse Functional Groups and Often form Secondary Reactive Species

The mutagenicity of some benzylic sulfuric acid esters to Salmonella typhimurium is strongly influenced by monovalent anions and other medium components. The formation of highly mutagenic 1-chloromethylpyrene has been previously demonstrated. In the present study we found that the sulfuric acid esters of a primary benzylic alcohol, 1-sulfooxymethylpyrene, and a secondary benzylic alcohol, 4H-sulfooxycyclopenta[def]phenanthrene, exhibit reactivity towards many functional groups abundant in vivo. We identified various reaction products and determined their rates of formation. Many reaction products were still reactive. Their reactivity and selectivity towards nucleophiles varied over a wide range and was differentfrom those of the parent sulfuric acid esters. Thus the formation of these secondary reactive species may explain many of the observed influences of medium components on the mutagenicity of benzylic sulfuric acid esters in vitro and may also affect their effects in vivo.     

Untersuchungen zur Flüchtigkeit von Tributylzinn-Verbindungen

Tributyltin compounds, predominantly tributyltinoxide (TBTO), have been used for many years for protecting materials especially for wood-protection, because of their excellent biocide effects. In the literature in this field TBTO is often described as readily volatile.—From evaporation experiments at +65°C it is demonstrated that tributyltinester made from long-chain carbon acids show distinctly lower volatility than TBTO. A method of testing to determine tin concentration in air is described. According to this method the emission rates of TBTO in comparison with TBT-naphthenate respectively TBT-linoleate from wood were determined over a period of one year. The results were transferred to a model-room and the tin-concentration in the air in this room was calculated.