Electrochemical Crosslinking of Alginate-Towards Doped Carbons for Oxygen Reduction.

Electrochemical crosslinking of alginate strands by in situ iron oxidation was explored using a potentiostatic regime. Carbon-based materials co-doped with iron, nitrogen, and/or sulfur were prepared via electrolyte composition variation with a nitrogen-rich compound (rivanol) or through post-treatments with sodium sulfide. Nanometer-sized iron particles were confirmed by transmission and field emission scanning electron microscopy in all samples as a consequence of the homogeneous dispersion of iron in the alginate scaffold and its concomitant growth-limiting effect of alginate chains. Raman spectra confirmed a rise in structural disorder with rivanol/Na2S treatment, which points to more defect sites and edges known to be active sites for oxygen reduction. Fourier transform infrared (FTIR) spectra confirmed the presence of different iron, nitrogen, and sulfur species, with a marked difference between Na2S treated/untreated samples. The most positive onset potential (-0.26 V vs. saturated calomel electrode, SCE) was evidenced for the sample co-doped with N, S, and Fe, surpassing the activity of those with single and/or double doping. The mechanism of oxygen reduction in 0.1 M KOH was dominated by the 2e- reduction pathway at low overpotentials and shifted towards complete 4e- reduction at the most negative explored values. The presented results put forward electrochemically formed alginate gels functionalized by homogeneously dispersed multivalent cations as an excellent starting point in nanomaterial design and engineering.

Spectral evidence of acetamiprid's thermal degradation products and mechanism.

Herein we unequivocally identify the mechanism of zeolite-catalysed thermal degradation of pesticide, employing Fourier-transform infrared spectroscopy (FTIR), Raman and mass spectrometry following temperature decomposition (TPDe/MS). We demonstrate that Y zeolite can effectively adsorb a significant amount of acetamiprid both in a single trial (168 mg/g) and in 10 cycles (1249 mg/g) with intermittent thermal regeneration at 300 °C. Sectional vibrational analysis of acetamiprid two-stage thermal degradation is performed for pristine and supported pesticide. The acetamiprid Raman spectral changes appear at 200 °C, while partial carbonization occurs at 250 °C. The gradual disappearance of the FTIR bands of acetamiprid is seen up to 270 °C when two Raman signature bands for carbonised material emerged. The TPDe/MS profiles reveal the evolution of mass fragments - in the first step, cleavage of the CC bond occurs between the aromatic core of the molecule and its tail-end, followed by cleavage of the CN bond. The mechanism of adsorbed acetamiprid degradation follows the same step, at significantly lower temperatures, as the process is catalysed by the interaction of acetamiprid nitrogens and zeolite support. Reduced temperature degradation allows for a quick recovery process that leaves 65% efficacy after 10 cycles. After numerous cycles of recovery, a subsequent one-time heat treatment at 700 °C completely restores initial efficacy. The efficient adsorption, novel details on degradation mechanism and ease of regeneration procedure place the Y zeolite at the forefront of future all-encompassing environmental solutions.

Modulation of cytotoxicity by consecutive adsorption of tannic acid and pesticides on surfactant functionalized zeolites.

This study investigated the environmental application of FAU type zeolites modified with cationic surfactants (cetylpyridinium chloride, tetrapropylammonium chloride and benzalkonium chloride). Adsorbent characterization was conducted using Fourier-transform infrared and Raman spectroscopy, thermogravimetry and differential thermal analysis, atomic force microscopy and X-ray powder diffraction. The efficiency for tannic acid adsorption from aqueous solution on the surface of prepared composites is studied and the adsorption process was modelled with different isotherm equations. Surfactant modifications of zeolites led to improved adsorption properties compared to FAU zeolites alone. The proposed mechanism controlling the adsorption of tannic acid onto surfactant modified zeolites mainly relies on π-π and hydrophobic interactions. The investigated materials are promising adsorbents for tannic acid and similar phenolics and may be important for environmental and dietary aspects of polyphenol persistence and usage. Further on, functionalized zeolites were studied for insecticide acetamiprid removal, prior to and after tannic acid retention. Promising findings of insecticide co-adsorption with tannic acid led to cytotoxicity evaluation. The cytotoxicity modulation effect of zeolites and tannic acid on acetamiprid points to the essential role of both components in insecticide toxicity reduction.

Double active BEA zeolite/silver tungstophosphates - Antimicrobial effects and pesticide removal.

Novel composites of BEA zeolite and silver tungstophosphate were prepared by different procedures: two-step impregnation, ion-exchange, and as physical mixtures with varying component mass ratios. Composites were characterized using Atomic force microscopy, Infrared, Raman and Atomic absorption spectroscopy, and results were related to adsorption properties and antimicrobial efficiencies of the composites. Prepared samples were tested as antimicrobial agents for fungal and different bacterial strains, as well as for adsorbents for pesticide nicosulfuron in aqueous solutions by using High-performance liquid chromatography. Experimental conditions for batch adsorption testing were optimized in order to efficiently eliminate nicosulfuron from aqueous solutions, while enabling antimicrobial activity of these advanced materials. Antimicrobial efficiency of composites was verified, and indicated that silver ion persistence in the solid phase is of utmost significance for the antimicrobial activity. Spectroscopic investigation revealed interaction of the silver tungstophosphate active phase and the zeolite framework, giving evidence of uniform distribution of active sites in the synthesized materials that proved to be essential for adsorption application. The best obtained adsorption capacity, as well as highest antimicrobial efficiency, is found for composite samples prepared by two-step impregnation with (BEA: silver tungstophosphate) mass ratio 2:1. The amount of nicosulfuron removed from water suspension was 38.2 mg per gram of composite, and the minimum inhibitory concentration determined for all investigated gram-negative bacteria was 125 µg mL-1.

Multi-analytical study of techniques and palettes of wall paintings of the monastery of Zica, Serbia.

The present multi-analytical study concentrates on establishing the painting techniques and the identity of the wall painting materials used by the artists from the 13th and 14th centuries to decorate the Zica monastery, Serbia. For this purpose, we demonstrate that micro-Raman spectroscopy is an efficient, non-destructive method with high spatial resolution which gives molecular and crystal structural information of a wide variety of both inorganic and organic materials. It is shown that elementary composition revealed through scanning electron microscopy with energy dispersive X-ray spectroscopy and energy dispersive X-ray fluorescence spectroscopy is necessary in some cases to confirm the identity of pigments and binders identified by micro-Raman spectroscopy. It was found that a fresco technique, in combination with mainly natural earth pigments such as red ochre, yellow ochre and green earth, was used. Expensive natural pigment lapis lazuli was exclusively used for obtaining blue colour while pure vermilion was used by the artists from the first period of decorations at the beginning of the 13th century. A mixture of pigments was used for attaining different colour shades. For the gilding of saint's haloes, thin golden foil was deposited over the tin sheet. In order to get a desirable optical and aesthetical impression, the metallic leaves were deposited over the yellow ochre preparatory layer. Deposits of gypsum on wall paintings as well as traces of weddellite are degradation products formed as a result of exposing wall paintings to environmental conditions.

Profiling differences in chemical composition of brain structures using Raman spectroscopy.

Raman spectroscopy enables non-invasive investigation of chemical composition of biological tissues. Due to similar chemical composition, the analysis of Raman spectra of brain structures and assignment of their spectral features to chemical constituents presents a particular challenge. In this study we demonstrate that standard and independent component analysis of Raman spectra is capable of assessment of differences in chemical composition between functionally related gray and white matter structures. Our results show the ability of Raman spectroscopy to successfully depict variation in chemical composition between structurally similar and/or functionally connected brain structures. The observed differences were attributed to variations in content of proteins and lipids in these structures. Independent component analysis enabled separation of contributions of major constituents in spectra and revealed spectral signatures of low-concentration metabolites. This provided finding of discrepancies between structures of striatum as well as between white matter structures. Raman spectroscopy can provide information about variations in contents of major chemical constituents in brain structures, while the application of independent component analysis performed on obtained spectra can help in revealing minute differences between closely related brain structures.

Radioprotectors - the evergreen topic.

To protect organisms from ionizing radiation (IR), and to reduce morbidity or mortality, various agents, called radioprotectors, have been utilized. Because radiation-induced cellular damage is attributed primarily to the harmful effects of free radicals, molecules with radical-scavenging properties are particularly promising as radioprotectors. Early development of such agents focused on thiol synthetic compounds, known as WR protectors, but only amifostine (WR-2721) has been used in clinical trials as an officially approved radioprotector. Besides thiol compounds, various compounds with different chemical structure were investigated, but an ideal radioprotector has not been found yet. Plants and natural products have been evaluated as promising sources of radioprotectors because of their low toxicity, although they exhibit an inferior protection level compared to synthetic thiol compounds. Active plant constituents seem to exert the radioprotection through antioxidant and free radical-scavenging activities. Our research established that plants containing polyphenolic compounds (raspberry, blueberry, strawberry, grape, etc.) exhibit antioxidative activities and protect genetic material from IR.

An improved HPLC method with the aid of a chemometric protocol: simultaneous determination of atorvastatin and its metabolites in plasma.

The aim of the present study was to optimize a chromatographic method for the analysis of atorvastatin (acid and lactone forms), ortho- and para-hydroxyatorvastatin by using an experimental design approach. Optimization experiments were conducted through a process of screening and optimization. The purpose of a screening design is to identify the factors that have significant effects on the selected chromatographic responses, and for this purpose a full 23 factorial design was used. The location of the true optimum was established by applying Derringer's desirability function, which provides simultaneously optimization of all seven responses. The ranges of the independent variables used for the optimization were content of acetonitrile in mobile phase (60-70%), temperature of column (30-40 °C) and flow rate (0.8-1.2 mL min⁻¹). The influences of these independent variables were evaluated for the output responses: retention time of first peak (p-hydroxyatorvastatin) and of last peak (atorvastatin, lactone form), symmetries of all four peaks and relative retention time of p-hydroxyatorvastatin. The primary goal of this investigation was establishing a new simple and sensitive method that could be used in analysis of biological samples. The method was validated and successfully applied for determination of atorvastatin (acid and lactone forms) and its metabolites in plasma.

Insulin mimetic effect of tungsten compounds on isolated rat adipocytes.

Investigations of effective, orally active, and safe antidiabetic metallopharmaceuticals have been carried out during the last two decades. It has been reported that tungsten compounds mimic the action of insulin in intact cell systems. As insulin mimetics, the most investigated tungsten compound was sodium tungstate (ST), rarely investigated was tungstophosphoric acid (WPA), but never alanine complex of tungstophosphoric acid (WPA-A). In this study, the insulin mimetic activity of three different tungsten compounds, ST, WPA, and WPA-A, was evaluated by means of in vitro measurements of the glucose uptake and inhibition of free fatty acids release from epinephrine-treated isolated rat white adipocytes. We investigated the influence of concentration (lower and higher, 0.1 and 1.0 mM, respectively) and solvent: isotonic salt solution-saline (0.9% w/v of NaCl) and dimethyl sulfoxide (DMSO; 2% v/v), on the biological effect of tested compounds. Our experimental data showed that all of the three investigated tungsten compounds possess insulin mimetic activity in vitro on the isolated adipocytes. Influence of concentration and solvents on insulin mimetic effect for the certain tungsten compounds were: WPA was shown effect independently of concentration and solvents; higher concentration and DMSO were significant decreasing insulin mimetic effect of ST; lower concentration and saline led to decreasing effect of WPA-A. Generally, there were no differences in insulin mimetic effect of three tungsten compounds in lower concentration and dissolved in DMSO. When saline was used as solvent, it was needed higher concentration of investigated compounds to accomplish the same effect. In conclusion, our results suggest that low concentration (0.1 mM) of ST, WPA, and WPA-A dissolved in 2% DMSO could be the good candidates for in vivo investigation of their antidiabetic properties.

Protective effects of tungstophosphoric acid and sodium tungstate on chemically induced liver necrosis in wistar rats.

PURPOSE: Many chemical compounds and infectious agents such as viruses induce liver damage like necrosis or fulminant hepatic failure which is sometimes difficult to manage by medical therapies. The induced liver necrosis by carbon tetrachloride (CCl4) and thioacetamide (TAA) are exemplary models for experimental liver necrosis caused by oxygen free radicals. The aim of this study was to investigate the effects of tungstophosphoric acid (TPA) and sodium tungstate (ST) on liver injury induced by CCl4 or TAA. METHODS: Hepatoprotective effects of TPA and ST on acute liver necrosis, chemically induced, were evaluated by the activity of serum enzymes (alkaline phosphatase, alanine transaminase and aspartate transaminase), oxidative stress parameters (activity of xanthine oxidase, concentrations of malondialdehyde and production of superoxide anion), antioxidative defence markers (concentration of reduced glutathione), and histopathology in Wistar rats. Liver necrosis was induced by administering a single intraperitoneal (i.p.) injection of CCl4 (1.0 ml/kg b.wt. of 80% CCl4 in corn oil) or a single i.p. injection of TAA (400 mg/kg b.w. dissolved in normal saline). TPA and ST were administrated to rats orally for 7 weeks (50 mg/kg b.wt.) prior to induction of liver necrosis. RESULTS: Induced liver necrosis caused significant elevation of activity of liver enzymes, parameters of oxidative stress and marked changes in histopathology, like necrosis of hepatocytes, hepatocyte degeneration and infiltration of inflammatory cells. In TPA and ST pretreated rats histopathological changes were almost absent, serum enzymes and oxidative stress parameters were decreased, while at the same time the concentration of reduced gluthathione was increased. CONCLUSION: The present findings suggest that treatment with TPA and ST for 7 weeks could be useful for the prevention of hepatic injury in rats.

Compounds of Mo, V and W in biochemistry and their biomedical activity.

Molybdenum, vanadium and tungsten compounds are widely applied as analytical reagents for determination of numerous pharmacologically active substances and different biochemical parameters. Recent data from the available literature pointed to a very potent biomedical activity of compounds containing these trace elements. The present paper represents a survey on the structure and chemical properties of these compounds, as well as on their biological activity, mostly based on their interaction with cations of biomolecules, such as phospholipids and proteins. Besides, their potent inhibitory effects on cellular targets, bacterial and viral DNA and RNA polymerases will be discussed, as well. Numerous authors clearly demonstrated the antiviral (especially anti-HIV), anticoagulant and antineoplastic properties of the compounds containing the above trace elements. It has been also shown that these compounds act on some cellular enzymatic systems leading to the normalisation of blood pressure, blood glucose and serum lipid levels. Also, compounds of these trace elements represent potent antiobesity agents and express hepatoprotective and antioxidative stress activity.