Methacrylate Copolymers with Liquid Crystalline Side Chains for Organic Gate Dielectric Applications

Polymers for all-organic field-effect transistors are under development to cope with the increasing demand for novel materials for organic electronics. Besides the semiconductor, the dielectric layer determines the efficiency of the final device. Poly(methyl methacrylate) (PMMA) is a frequently used dielectric. In this work, the chemical structure of this material was stepwise altered by incorporation of cross-linkable and/or self-organizing comonomers to improve the chemical stability and the dielectric properties. Different types of cross-linking methods were used to prevent dissolution, swelling or intermixing of the dielectric e.g. during formation processes of top electrodes or semiconducting layers. Self-organizing comonomers were expected to influence the dielectric/semiconductor interface, and moreover, to enhance the chemical resistance of the dielectric. Random copolymers were obtained by free radical and reversible addition-fragmentation chain transfer (RAFT) polymerization. With 6-[4-(4'-cyanophenyl)phenoxy]alkyl side chains having hexyl or octyl spacer, thermotropic liquid crystalline (LC) behavior and nanophase separation into smectic layers was observed, while copolymerization with methyl methacrylate induced molecular disorder. In addition to chemical, thermal and structural properties, electrical characteristics like breakdown field strength (EBD) and relative permittivity (k) were determined. The dielectric films were studied in metal-insulator-metal setups. EBD appeared to be strongly dependent on the type of electrode used and especially the ink formulation. Cross-linking of PMMA yielded an increase in EBD up to 4.0 MV/cm with Ag and 5.7 MV/cm with

PEDOT

PSS electrodes because of the increased solvent resistance. The LC side chains reduce the ability for cross-linking resulting in decreased breakdown field strengths.

Synthesis of multifunctional plasmonic nanopillar array using soft thermal nanoimprint lithography for highly sensitive refractive index sensing

A low-cost plasmonic nanopillar array was synthesized using soft thermal nanoimprint lithography, and its sensitivity was determined through far-field spectroscopic measurements. Its transmission spectrum was highly dependent on the refractive index of the surrounding medium, with its sensitivity being 375 nm per refractive index unit according to the spectral shift. Moreover, a simple sensor whose reflected color changed with a change in the plasma frequency on varying the surrounding medium was fabricated.

Food intake monitoring: automated chew event detection in chewing sounds

The analysis of the food intake behavior has the potential to provide insights into the development of obesity and eating disorders. As an elementary part of this analysis, chewing strokes have to be detected and counted. Our approach for food intake analysis is the evaluation of chewing sounds generated during the process of eating. These sounds were recorded by microphones applied to the outer ear canal of the user. Eight different algorithms for automated chew event detection were presented and evaluated on two datasets. The first dataset contained food intake sounds from the consumption of six types of food. The second dataset consisted of recordings of different environmental sounds. These datasets contained 68,094 chew events in around 18 h recording data. The results of the automated chew event detection were compared to manual annotations. Precision and recall over 80% were achieved by most of the algorithms. A simple noise reduction algorithm using spectral subtraction was implemented for signal enhancement. Its benefit on the chew event detection performance was evaluated. A reduction of the number of false detections by 28% on average was achieved by maintaining the detection performance. The system is able to be used for calculation of the chewing frequency in laboratory settings.

Biologically inspired omniphobic surfaces by reverse imprint lithography

Springtail skin morphology is translated into robust omniphobic polymer membranes by reverse imprint lithography. The combination of overhanging cross-sections and their arrangement in a self-supporting comblike pattern are crucial for mechanically stable coatings that can be even applied to curved surfaces.

Determination of the wine preservative sulphur dioxide with cyclic voltammetry using inkjet printed electrodes

During winemaking sulphur dioxide is added to prevent undesirable reactions. However, concerns over the harmful effects of sulphites have led to legal limits being placed upon such additives. There is thus a need for simple and selective determinations of sulphur dioxide in wine, especially during winemaking. The simultaneous detection of polyphenols and sulphur dioxide, using cyclic voltammetry at inert electrodes is challenging due to close oxidation potentials. In the present study, inkjet printed electrodes were developed with a suitable voltammetric signal on which the polyphenol oxidation is suppressed and the oxidation peak height for sulphur dioxide corresponds linearly to the concentration. Different types of working electrodes were printed. Electrodes consisting of gold nanoparticles mixed with silver showed the highest sensitivity towards sulphur dioxide. Low cost production of the sensor elements and ultra fast determination of sulphur dioxide by cyclic voltammetry makes this technique very promising for the wine industry.

Food intake monitoring: an acoustical approach to automated food intake activity detection and classification of consumed food

Obesity and nutrition-related diseases are currently growing challenges for medicine. A precise and timesaving method for food intake monitoring is needed. For this purpose, an approach based on the classification of sounds produced during food intake is presented. Sounds are recorded non-invasively by miniature microphones in the outer ear canal. A database of 51 participants eating seven types of food and consuming one drink has been developed for algorithm development and model training. The database is labeled manually using a protocol with introductions for annotation. The annotation procedure is evaluated using Cohen's kappa coefficient. The food intake activity is detected by the comparison of the signal energy of in-ear sounds to environmental sounds recorded by a reference microphone. Hidden Markov models are used for the recognition of single chew or swallowing events. Intake cycles are modeled as event sequences in finite-state grammars. Classification of consumed food is realized by a finite-state grammar decoder based on the Viterbi algorithm. We achieved a detection accuracy of 83% and a food classification accuracy of 79% on a test set of 10% of all records. Our approach faces the need of monitoring the time and occurrence of eating. With differentiation of consumed food, a first step toward the goal of meal weight estimation is taken.

Organic anion transporting polypeptides expressed in liver and brain mediate uptake of microcystin

Microcystins are toxins produced by freshwater cyanobacteria. They are cyclic heptapeptides that exhibit hepato- and neurotoxicity. However, the transport systems that mediate uptake of microcystins into hepatocytes and across the blood-brain barrier have not yet been identified. Using the Xenopus laevis oocyte expression system we tested whether members of the organic anion transporting polypeptide superfamily (rodent: Oatps; human: OATPs) are involved in transport of the most common microcystin variant microcystin-LR by measuring uptake of a radiolabeled derivative dihydromicrocystin-LR. Among the tested Oatps/OATPs, rat Oatp1b2, human OATP1B1, human OATP1B3, and human OATP1A2 transported microcystin-LR 2- to 5-fold above water-injected control oocytes. This microcystin-LR transport was inhibited by co-incubation with the known Oatp/OATP substrates taurocholate (TC) and bromosulfophthalein (BSP). Microcystin-LR transport mediated by the human OATPs was further characterized and showed saturability with increasing microcystin-LR concentrations. The apparent K(m) values amounted to 7 +/- 3 microM for OATP1B1, 9 +/- 3 microM for OATP1B3, and 20 +/- 8 microM for OATP1A2. No microcystin-LR transport was observed in oocytes expressing Oatp1a1, Oatp1a4, and OATP2B1. These results may explain some of the observed organ-specific toxicity of microcystin-LR. Oatp1b2, OATP1B1, and OATP1B3 are responsible for microcystin transport into hepatocytes, whereas OATP1A2 mediates microcystin-LR transport across the blood-brain barrier.

Congener-independent immunoassay for microcystins and nodularins

Cyanobacteria (blue-green algae) (e.g., Microcystis and Nodularia spp.) capable of producing toxic peptides are found in fresh and brackish water worldwide. These toxins include the microcystin (MC) heptapeptides (>60 congeners) and the nodularin pentapeptides (ca. 5 congeners). Cyanobacterial cyclic peptide toxins are harmful to man, other mammals, birds, and fish. Acute exposure to high concentrations of these toxins causes liver damage, while subchronic or chronic exposure may promote liver tumor formation. The detection of cyclic peptide cyanobacterial toxins in surface and drinking waters has been hampered by the low limits of detection required and that the present routine detection is restricted to a few of the congeners. The unusual beta-amino acid ADDA (4E,6E-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid) is present in most (>80%) of the known toxic penta- and heptapeptide toxin congeners. Here, we report the synthesis of two ADDA-haptens, the raising of antibodies to ADDA, and the development of a competitive indirect ELISA for the detection of microcystins and nodularins utilizing these antibodies. The assay has a limit of quantitation of 0.02-0.07 ng/mL (depending on which congeners are present), lower than the WHO-proposed guideline (1 ng/mL) for drinking water, irrespective of the sample matrix (raw water, drinking water, or pure toxin in PBS). This new ELISA is robust, can be performed without sample preconcentration, detects toxins in freshwater samples at lower concentrations than does the protein phosphatase inhibition assay, and shows very good cross-reactivity with all cyanobacterial cyclic peptide toxin congeners tested to date (MC-LR, -RR, -YR, -LW, -LF, 3-desmethyl-MC-LR, 3-desmethyl-MC-RR, and nodularin).

Toxicity of the cyanobacterial cyclic heptapeptide toxins microcystin-LR and -RR in early life-stages of the African clawed frog (Xenopus laevis)

Numerous cyanobacterial species are capable of producing potent toxins, which have been known to cause intoxications and fatalities in wildlife, livestock and humans. Microcystis is amongst the most ubiquitously distributed blue-green algal genus and almost invariably produces cyclic heptapeptide toxins called microcystins (MC). These toxins are highly persistent in water (several weeks). Highest concentrations are found in shallow littoral areas, the primary environment for aquatic early life-stage development. Therefore, the present study focussed on the potential embryotoxic effects of MC (MC-LR and -RR) in early life-stages of the amphibian Xenopus laevis. The endpoints chosen were mortality, malformation and growth inhibition. To achieve an improved dose-response relationship the uptake of MC was quantified simultaneously, using a radiolabeled derivative of MC-LR. As one of the best described molecular mechanisms of MC toxicity involves the specific inhibition of serine/threonine protein phosphatases-1 and -2A (PP), essential enzymes involved in the mechanisms of cell cycle regulation and maintenance of cellular morphology, the inhibition of PP in X. laevis exposed to MC was monitored. For this the presence of both PP-1 and PP-2A was confirmed by means of SDS-PAGE and immunoblotting. Second, the capacity of MC to inhibit X. laevis embryo-larval PP was corroborated by in vitro incubation of embryo-larval homogenates with MC-LR and -RR and subsequent determination of PP-inhibition. No increased mortality, malformation, or growth inhibition was observed even at the highest MC concentrations employed. MC had neither a demonstrable inhibitory effect on X. laevis PP-activity in vivo in the first 96 h of exposure. However, as of 96 and 120 h exposure a significant inhibition of PP activity was observed at the highest dose (2000 µg/l) in MC-LR and MC-RR exposed embryo-larvae, respectively. By the same token, no notable amounts of radiolabeled [3H]-MC-LR were taken up during the first 96 h, whereas a drastic increase in [3H]-MC-LR was observed after feeding of the larvae had commenced. The [3H]-MC-LR concentration was consistently found to be highest in the viscerothoracal sections of the larvae (2112+/-429 µg MC/kg dry weight after 120 h). The present findings indicate that transchorional/transdermal absorption of MC in X. laevis is minimal or absent and that oral uptake of MC with ambient water is necessary for the development of MC related toxicity. Furthermore, the comparison of the MC doses used in this study with the concentrations reported in surface waters indicate that early life-stages of amphibians (up to 5 days of development) are unlikely to be affected by cyanobacterial blooms producing MC-LR and -RR.

Pathological and biochemical characterization of microcystin-induced hepatopancreas and kidney damage in carp (Cyprinus carpio)

Mass occurrences of cyanobacteria, due to their inherent capacity for toxin production, specifically of microcystins (MC), have been associated with fish kills worldwide. The uptake of MC-LR and the sequence of pathological and associated biochemical changes was investigated in carp (Cyprinus carpio) in vivo over 72 h. Carp were gavaged with a single sublethal bolus dose of toxic Microcystis aeruginosa (PCC 7806) amounting to an equivalent of 400 microg MC-LR/kg body wt. Damage of renal proximal tubular cells and hepatocytes was observed as early as 1 h, followed by pathological changes in the intestinal mucosa at approximately 12 h postdosing. These alterations were characterized in hepatopancreas by a dissociation of hepatocytes, an early onset of apoptotic cell death, and delayed cell lysis. In the renal proximal tubules (P2) observations included increased vacuolation of individual tubular epithelial cells, apoptosis, cell shedding, and finally proteinaceous casts at the cortico-medullary junction. Concurrently with the pathological alterations, MC-immunopositive staining was observed in hepatocytes and the proximal tubular cells; the staining increasing in the hepatopancreas in intensity with increasing time postdosing. The presence of apoptotic cell death was determined using in situ fragment end labeling (ISEL) of the respective tissue sections and agarose gel electrophoresis for detection of DNA-laddering. The analysis of carp tissue extracts (hepatopancreas, kidney, GI tract, skeletal muscle, brain, heart, spleen, and gills) demonstrated MC-LR adducts having molecular weights of 38 kDa (putatively catalytic subunit of protein phosphatases-1 and -2A) and 28 kDa, respectively. An additional band was found to be present at 23 kDa in both hepatopancreas and kidney. The present data demonstrate that, in comparison to the pathological events in salmonids exposed to MC, where a slower development of pathology and primarily necrotic cell death prevails, the pathology in carp develops rapidly and at lower toxin concentrations. This is most likely due to a more efficient uptake of toxin, while the mechanism of cell death is primarily apoptosis.

Microcystin-LR toxicodynamics, induced pathology, and immunohistochemical localization in livers of blue-green algae exposed rainbow trout (oncorhynchus mykiss)

With this retrospective study, we investigated the temporal pattern of toxin exposure and pathology, as well as the topical relationship between hepatotoxic injury and localization of microcystin-LR, a potent hepatotoxin, tumor promoter, and inhibitor of protein phosphatases-1 and -2A (PP), in livers of MC-gavaged rainbow trout (Oncorhynchus mykiss) yearlings, using an immunohistochemical detection method and MC-specific antibodies. H&E stains of liver sections were used to determine pathological changes. Nuclear morphology of hepatocytes and ISEL analysis were employed as endpoints to detect the advent of apoptotic cell death in hepatocytes. Trout had been gavaged with lyophilized cyanobacteria (Microcystis aeruginosa, strain PCC 7806) at acutely toxic doses of 5700 microg microcystin (MC) per kg of body weight (bw), as described previously (Tencalla and Dietrich, 1997). Briefly, 3 control and 3 test animal were killed 1, 3, 12, 24, 48, and 72 h after bolus dosing, and livers were fixed and paraffin embedded for histological analysis and later retrospective histochemical analyses. The results of the immunohistochemistry reported here revealed a time dependent, discernible increase in MC-positive staining intensity throughout the liver, clearly not concurring with the kinetics of hepatic PP inhibition observed in the same fish and reported in an earlier publication by Tencalla and Dietrich (1997). After 3 h, marked and increasing MC-immunopositivity was observed in the cytoplasm, as well as the nuclei of hepatocytes. Apoptotic cell death could be detected after 48 h, at the very earliest. These data suggest that accumulation of MC and subsequent changes in cellular morphology, PP inhibition, and hepatocyte necrosis represent the primary events in microcystin induced hepatotoxicity and appear to be associated with the reversible interaction of MC with the PP. In contrast, apoptotic cell death, as demonstrated here, seems to be of only secondary nature and presumably results from the covalent interaction of MC with cellular and nuclear PP as well as other thiol containing cellular proteins.