Cr-Detector: A simple chemosensing system for onsite Cr (VI) detection in water

Due to the increase in urbanization and industrialization, the load of toxicants in the environment is alarming. The most common toxicants, including heavy metals and metalloids such as hexavalent Chromium, have severe pathophysiological impacts on humans and other aquatic biotas. Therefore, developing a portable rapid detection device for such toxicants in the aquatic environment is necessary. This work portrays the development of a field-portable image analysis device coupled with 3,3',5,5'-tetramethylbenzidine (TMB) as a sensing probe for chromium (VI) detection in the aquatic ecosystem. Sensor parameters, such as reagent concentration, reaction time, etc., were optimized for the sensor development and validation using a commercial UV-Vis spectrophotometer. The chemoreceptor integrated with a uniform illumination imaging system (UIIS) revealed the system's applicability toward Cr(VI) detection. The calibration curve using the R-value of image parameters allows Cr(VI) detection in the linear range of 25 to 600 ppb, which covers the prescribed permissible limit by various regulatory authorities. Furthermore, the adjusted R2 = 0.992 of the linear fit and correlation coefficients of 0.99018 against the spectrophotometric method signifies the suitability of the developed system. This TMB-coupled field-portable sensing system is the first-ever reported image analysis-based technology for detecting a wide range of Cr(VI) in aquatic ecosystems to our knowledge.

Domestic microwave assisted one-step co-precipitation of Ag–CuO nanocomposite of Cu/Ag ratio optimized for photocatalysis and comparison with blending CuO with Ag nanoparticles

The Ag–CuO metal–semiconductor nanocomposite (NC) is an important component in various nanomaterial-based applications. Several approaches have been studied to facilitate its synthesis. However, most of them encounter some drawbacks. In the present work, we show the synthesis of Ag–CuO NCs through one-pot co-precipitation with the aid of simple starting chemicals and measures including metal nitrates, hexamine, agar, and domestic microwave heating. Photocatalyzed degradation of Congo Red in addition to the structural and optical characteristics show that this method is successful in production of the Schottky barrier in Ag–CuO NCs with improved photocatalytic activity (PCA). Changing the Cu content shows that the NC is not successfully formed at low Cu mol%. Consequently, the PCA of Ag–CuO of low Cu (2%–6%) lies within 4.5 × 10−4 – 5.1 × 10−4 min−1, which is even lower than those of plain Ag and CuO nanoparticles (6.0 × 10−4 – 8.1 × 10−4 min−1, respectively). 60 mol% was the optimum Cu content with the highest PCA (18.8 × 10−4 min−1). Blending plain Ag and CuO nanoparticles to mimic the co-precipitated 60 mol% Ag–CuO showed very low PCA, even lower than the plain Ag and CuO, which once again confirms the efficiency of the simple one-pot co-precipitation approach in producing Ag–CuO with the Schottky barrier and promoted PCA.

Chromium Pollution in European Water, Sources, Health Risk, and Remediation Strategies: An Overview

Chromium is a potentially toxic metal occurring in water and groundwater as a result of natural and anthropogenic sources. Microbial interaction with mafic and ultramafic rocks together with geogenic processes release Cr (VI) in natural environment by chromite oxidation. Moreover, Cr (VI) pollution is largely related to several Cr (VI) industrial applications in the field of energy production, manufacturing of metals and chemicals, and subsequent waste and wastewater management. Chromium discharge in European Union (EU) waters is subjected to nationwide recommendations, which vary depending on the type of industry and receiving water body. Once in water, chromium mainly occurs in two oxidation states Cr (III) and Cr (VI) and related ion forms depending on pH values, redox potential, and presence of natural reducing agents. Public concerns with chromium are primarily related to hexavalent compounds owing to their toxic effects on humans, animals, plants, and microorganisms. Risks for human health range from skin irritation to DNA damages and cancer development, depending on dose, exposure level, and duration. Remediation strategies commonly used for Cr (VI) removal include physico-chemical and biological methods. This work critically presents their advantages and disadvantages, suggesting a site-specific and accurate evaluation for choosing the best available recovering technology.

Gene-environment interaction and maternal arsenic methylation efficiency during pregnancy

BACKGROUND

Single nucleotide polymorphisms (SNPs) may influence arsenic methylation efficiency, affecting arsenic metabolism. Whether gene-environment interactions affect arsenic metabolism during pregnancy remains unclear, which may have implications for pregnancy outcomes.

OBJECTIVE

We aimed to investigate main effects as well as potential SNP-arsenic interactions on arsenic methylation efficiency in pregnant women.

METHOD

We recruited 1613 pregnant women in Bangladesh, and collected two urine samples from each participant, one at 4-16 weeks, and the second at 21-37 weeks of pregnancy. We determined the proportions of each arsenic metabolite [inorganic As (iAs)%, monomethylarsonic acid (MMA)%, and dimethylarsinic acid (DMA)%] from the total urinary arsenic level of each sample. A panel of 63 candidate SNPs was selected for genotyping based on their reported associations with arsenic metabolism (including in As3MT, N6AMT1, and GSTO2 genes). We used linear regression models to assess the association between each SNP and DMA% with an additive allelic assumption, as well as SNP-arsenic interaction on DMA%. These analyses were performed separately for two urine collection time-points to capture differences in susceptibility to arsenic toxicity.

RESULT

Intron variants for As3MT were associated with DMA%. rs9527 (β = -2.98%, P_FDR = 0.008) and rs1046778 (β = 1.64%, P_FDR = 0.008) were associated with this measure in the early gestational period; rs3740393 (β = 2.54%, P_FDR = 0.002) and rs1046778 (β = 1.97%, P_FDR = 0.003) in the mid-to-late gestational period. Further, As3MT, GSTO2, and N6AMT1 polymorphisms showed different effect sizes on DMA% conditional on arsenic exposure levels. However, SNP-arsenic interactions were not statistically significant after adjusting for false discovery rate (FDR). rs1048546 in N6AMT1 had the highest significance level in the SNP-arsenic interaction test during mid-to-late gestation (β = -1.8% vs. 1.4%, P_{GxE_FDR} = 0.075). Finally, As3MT and As3MT/CNNM2 haplotypes were associated with DMA% at both time points.

CONCLUSION

We found that not all genetic associations reported in arsenic methylation efficiency replicate in pregnant women. Arsenic exposure level has a limited effect in modifying the association between genetic variation and arsenic methylation efficiency.

Photo-induced H2 production by [NiFe]-hydrogenase from T. roseopersicina covalently linked to a Ru(II) photosensitizer

The potential of hydrogen as a clean renewable fuel source and the finite reserves of platinum metal to be utilized in hydrogen production catalysts have provided the motivation for the development of non-noble metal-based solutions for catalytic hydrogen production. There are a number of microorganisms that possess highly efficient hydrogen production catalysts termed hydrogenases that generate hydrogen under certain metabolic conditions. Although hydrogenases occur in photosynthetic microorganisms, the oxygen sensitivity of these enzymes represents a significant barrier in directly coupling hydrogen production to oxygenic photosynthesis. To overcome this barrier, there has been considerable interest in identifying or engineering oxygen tolerant hydrogenases or generating mimetic systems that do not rely on oxygen producing photocatalysts. In this work, we demonstrate photo-induced hydrogen production from a stable [NiFe]-hydrogenase coupled to a [Ru(2,2'-bipyridine)(2)(5-amino-1,10-phenanthroline)](2+) photocatalyst. When the Ru(II) complex is covalently attached to the hydrogenase, photocatalytic hydrogen production occurs more efficiently in the presence of a redox mediator than if the Ru(II) complex is simply present in solution. Furthermore, sustained hydrogen production occurs even in the presence of oxygen by presumably creating a local anoxic environment through the reduction of oxygen similar to what is proposed for oxygen tolerant hydrogenases. These results provide a strong proof of concept for engineering photocatalytic hydrogen production in the presence of oxygen using biohybrid mimetic systems.

Hydrogen enhances nickel tolerance in the purple sulfur bacterium Thiocapsa roseopersicina

A common microbial strategy for detoxifying metals involves redox transformation which often results in metal precipitation and/or immobilization. In the present study, the influence of ionic nickel [Ni(II)] on growth of the purple sulfur bacterium Thiocapsa roseopersicina was investigated. The results suggest that Ni(II) in the bulk medium at micromolar concentrations results in growth inhibition, specifically an increase in the lag phase of growth, a decrease in the specific growth rate, and a decrease in total protein concentration when compared to growth controls containing no added Ni(II). The inhibitory effects of Ni(II) on the growth of T. roseopersicina could be partially overcome by the addition of hydrogen (H(2)) gas. However, the inhibitory effects of Ni(II) on the growth of T. roseopersicina were not alleviated by H(2) in a strain containing deletions in all hydrogenase-encoding genes. Transmission electron micrographs of wild-type T. roseopersicina grown in the presence of Ni(II) and H(2) revealed a significantly greater number of dense nanoparticulates associated with the cells when compared to wild-type cells grown in the absence of H(2) and hydrogenase mutant strains grown in the presence of H(2). X-ray diffraction and vibrating sample magnetometry of the dense nanoparticles indicated the presence of zerovalent Ni, suggesting Ni(II) reduction. Purified T. roseopersicina hyn-encoded hydrogenase catalyzed the formation of zerovalent Ni particles in vitro, suggesting a role for this hydrogenase in Ni(II) reduction in vivo. Collectively, these results suggest a link among H(2) metabolism, Ni(II) tolerance, and Ni(II) reduction in T. roseopersicina .

Effects of vitamin E and selenium on serum trace and major elements in horses

The combined effects of vitamin E and selenium were studied in native Anatolian horses subject to strenuous exercise. The concentrations of copper, zinc, iron, calcium, potassium, and magnesium were determined in serum by atomic absorption spectrometry in two study groups (n = 25 each), one of which served as untreated controls. After exercising the horses by running 1,500 m in about 7 min, only the copper level and the copper/zinc ratio significantly increased (p < 0.05), but the concentrations of calcium, potassium, iron, and magnesium remained unchanged. In horses treated with vitamin E and selenium, the calcium and potassium levels decreased to levels lower than those of untreated controls before and after exercise. The iron levels were not changed by exercise or treatment alone but increased when the horses had been supplemented and exercised. The copper level and the copper/zinc ration increased as a result of exercise in both treated and untreated horses. These changes suggest that supplementation with vitamin E and selenium had an important effect on the serum concentrations of calcium, potassium, copper, iron, and the copper/zinc ratio.

Plasma levels of zinc, copper, copper/zinc ratio, and activity of carbonic anhydrase in equine piroplasmosis

We have determined the plasma concentrations of copper, zinc, copper/zinc ratio, and carbonic anhydrase activity in horses infected with Babesia equi. The study was conducted in 14 horses with the disease and 10 healthy animals that served as controls. The infection was confirmed by the clinical manifestations of the disease and by Giemsa staining of thin blood smears showing the parasites inside red blood cells. The horses with piroplasmosis had lower plasma levels of zinc, elevated copper, and increased activity of carbonic anhydrase. Consequently, the copper/zinc ratio was also higher than in the healthy controls.

Liquid-liquid extraction of cadmium by sodium diethyldithiocarbamate from biological matrixes for isotope dilution inductively coupled plasma mass spectrometry

A published procedure for the liquid-liquid extraction of Cd by sodium diethyldithiocarbamate (NaDDC) was modified and tested on 12 biological matrixes of plant and animal origin for use with isotope dilution (ID) inductively coupled plasma mass spectrometry (ICPMS). The tested matrixes were reference materials, certified for Cd, and a feces in-house standard. The digested and extracted standards were analyzed for Cd stable isotopes by ICPMS and the resulting isotope ratios examined for isobaric and polyatomic interferences. Cadmium recoveries, after extraction, ranged from 73% to 20% and apparently were inversely related to Cd concentration, even in the presence of excess chelator. For each reference material, the measured isotope ratios for Cd were corrected for instrumental bias and compared to natural abundance Cd isotope ratios. Nonextracted samples had large isotope ratio deviations for all but one or two ratios. Extraction improved all the isotope ratios measured (lowered % error relative to natural abundances), but interferences were noted for a few samples. The extracted human in-house feces standard was found to have Sn signals reduced by 300-fold, but residual Sn concentrations still interfered with 116Cd, though not 112Cd or 114Cd. Thus, evaluation of the NADDC-extracted in-house fecal standard and reference materials indicate the successful removal of interferences that otherwise prevented accurate determinations of Cd by IDICPMS and show that a number of Cd isotope ratios could be accurately measured (< 1.5% error) for multiple stable isotope tracer studies in a broad range of NaDDC-extracted biological matrixes.