Aquifer-Scale Observations of Iron Redox Transformations in Arsenic-Impacted Environments to Predict Future Contamination

Iron oxides control the mobility of a host of contaminants in aquifer systems, and the microbial reduction of iron oxides in the subsurface is linked to high levels of arsenic in groundwater that affects greater than 150 million people globally. Paired observations of groundwater and solid-phase aquifer composition are critical to understand spatial and temporal trends in contamination and effectively manage changing water resources, yet field-representative mineralogical data are sparse across redox gradients relevant to arsenic contamination. We characterize iron mineralogy using X-ray absorption spectroscopy across a natural gradient of groundwater arsenic contamination in Vietnam. Hierarchical cluster analysis classifies sediments into meaningful groups delineating weathering and redox changes, diagnostic of depositional history, in this first direct characterization of redox transformations in the field. Notably, these groupings reveal a signature of iron minerals undergoing active reduction before the onset of arsenic contamination in groundwater. Pleistocene sediments undergoing postdepositional reduction may be more extensive than previously recognized due to previous misclassification. By upscaling to similar environments in South and Southeast Asia via multinomial logistic regression modeling, we show that active iron reduction, and therefore susceptibility to future arsenic contamination, is more widely distributed in presumably pristine aquifers than anticipated.

Structure-based discovery of interleukin-33 inhibitors: a pharmacophore modelling, molecular docking, and molecular dynamics simulation approach

Interleukin (IL)-33 is a new cytokine of the IL-1 family that is related to several inflammatory and autoimmune diseases. IL-33 binds to its ST2 receptor and leads to biological responses thereof. Currently, no drugs have been approved for the treatment of IL-33 related diseases. The aim of this study was to search for small molecules that inhibit the protein-protein interaction between IL-33 and ST2. A virtual screening was first performed to identify potential molecules that can bind IL-33. By analysing the interactions between key residues in the complex of IL-33/ST2, two pharmacophore hypotheses were then generated based on the 'mimicry' and 'pair-rule' principles. From a database of 62,074 compounds, 60 molecules satisfying the pharmacophore models were identified and docked to IL-33. Among 35 compounds successfully docked into the protein, 9 potential ligands in complex with IL-33 were selected for further analysis by molecular dynamics simulations. Based on the stability of the complexes and the interactions of each ligand with the key residues of IL-33, two compounds DB00158 and DB00642 were identified as the most potential inhibitors that can be further investigated as promising novel IL-33 inhibitory drugs.

Quantifying Riverine Recharge Impacts on Redox Conditions and Arsenic Release in Groundwater Aquifers Along the Red River, Vietnam

Widespread contamination of groundwater with geogenic arsenic is attributed to microbial dissolution of arsenic-bearing iron (oxyhydr)oxides minerals coupled to the oxidation of organic carbon. The recharge sources to an aquifer can influence groundwater arsenic concentrations by transport of dissolved arsenic or reactive constituents that affect arsenic mobilization. To understand how different recharge sources affect arsenic contamination-in particular through their influence on organic carbon and sulfate cycling-we delineated and quantified recharge sources in the arsenic affected region around Hanoi, Vietnam. We constrained potential end-member compositions and employed a novel end-member mixing model using an ensemble approach to apportion recharge sources. Groundwater arsenic and dissolved organic carbon concentrations are controlled by the dominant source of recharge. High arsenic concentrations are prevalent regardless of high dissolved organic carbon or ammonium levels, indicative of organic matter decomposition, where the dominant recharge source is riverine. In contrast, high dissolved organic carbon and significant organic matter decomposition are required to generate elevated groundwater arsenic where recharge is largely nonriverine. These findings suggest that in areas of riverine recharge, arsenic may be efficiently mobilized from reactive surficial environments and carried from river-aquifer interfaces into groundwater. In groundwaters derived from nonriverine recharge areas, significantly more organic carbon mineralization is required to obtain equivalent levels of arsenic mobilization within inland sediments. This method can be broadly applied to examine the connection between hydrology, geochemistry and groundwater quality.

Novel Drug Delivery System Based on Ginsenoside Rb1 Loaded to Chitosan/Alginate Nanocomposite Films

Recently, drug delivery using natural and biodegradable nanoparticles has attracted huge attention. This study focused to deliver an anti-cancer and anti-inflammatory drug Ginsenoside Rb1 through chitosan-Alginate nanocomposite film prepared by solution method. Ginsenoside Rb1 is a dammaran saponin group, which is extracted from an herbaceous plant Panax notoginseng. Ginsenoside loaded alginate-chitosan nanocomposite films were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) methods. The FTIR spectra of alginate/chitosan/ginsenoside Rb1 nanocomposite films show that chitosan, alginate, and ginsenoside Rb1 are linked through the hydrogen bonding and dipolar-dipolar interactions. The FESEM image indicates that the chitosan and ginsenoside Rb1 dispersed well in the alginate matrix. The DSC diagrams display that melting temperature of alginate/chitosan/ginsenoside Rb1 nanocomposite films higher than that of chitosan and lower than that of alginate. It means that alginate and chitosan interact together. Investigation of the ginsenoside Rb1 release from alginate/chitosan/ginsenoside Rb1 nanocomposite films at different pH solutions and different ginsenoside Rb1 content has been carried out by ultraviolet-visible spectroscopy method. The rate of drug release is proportional to the increase in pH solution and inversely proportional to the content of loaded ginsenoside Rb1. The Rb1 release process includes two stages: burst release in the first 10 hours, then constant release afterwards. The suitable ratio of alginate/chitosan to prepare the alginate/chitosan/ginsenoside Rb1 nanocomposite films for further investigations was found out to be 8:2. Ginsenoside Rb1 release process from alginate/chitosan/ginsenoside Rb1 nanocomposite films was believed to be first-order kinetics in the first stage, and then the Rb1 release complies with Higuchi kinetic model in the slow release stage. This study demonstrated the novel synthesis methodology to design drug delivery system based on ginsenoside Rb1 loaded to chitosan/alginate nanocomposite films.

Tensile, Thermal, Dielectric and Morphological Properties of Polyoxymethylene/Silica Nanocomposites

This paper presents the tensile, thermal, dielectric and morphological properties of composites based on polyoxymethylene (POM) and nanosilica (NS) prepared by melt mixing method at 190 °C. Based on the torque readings, the processing of POM/NS composites were found to be easier in comparison to only POM. The FT-IR spectra analysis of the POM/NS nanocomposites showed the presence of peak at approximately 910 cm-1, attributed to the Si-O and C-O groups in NS and POM on the POM/NS nanocomposite. The absorption at these peaks increased on gradually increasing the content of NS. Tensile property testing (tensile strength, elongation at break, and Young's modulus) indicated that the tensile strength of POM/NS nanocomposites increases as the NS content increases from 0.5 wt.% to 1.5 wt.%, and sharply dropped when the NS content was more than 2 wt.%. A similar trend was observed for Young's modulus and elongation at break of the nanocomposites. The DSC analysis of the nanocomposites showed that the melting temperature (Tm) of POM/NC composites increased in the presence of low weight % of NS which can be attributed to the interaction between POM and NS leading to the rising crystallinity of all nanocomposites. POM/NS have a slightly higher temperature resistance as confirmed from the TGA analysis and POM/NS 1.5 wt.% had the maximum degradation temperature (Tmax) value and consequently the lowest weight loss. The dielectric constant of the nanocomposites increased from 3.26 to 3.56, while the dielectric loss tangent and volume resistivity were dropped, corresponding to the NS content from 0.5 to 2 wt.%. The SEM images of POM/NS nanocomposites demonstrated that the NS particles were dispersed relatively regularly into POM with a size in the range of 100 to 500 nm. They were dispersed more regularly into the polymer matrix at 1.5 wt.% NS. Based on the obtained results, the suitable NS content for the preparation of the POM/NS nanocomposites was found to be 1.5 wt.%.

Polylactic Acid/Chitosan Nanoparticles Loading Nifedipine: Characterization Findings and In Vivo Investigation in Animal

This paper presents the results of zeta potential, water contact angle, atomic force microscopy image, in vitro solubility, and content of heavy metals in polylactic acid (PLA)/chitosan (CS) nanoparticles loading nifedipine. In addition, the In Vivo test of the PLA/CS nanoparticles loading nifedipine in the mice is also one of highlights of this work. The Zeta potential result shows that the charged surface of the PLA/CS nanoparticles loading nifedipine is neutral, negative or complex depending on nifedipine content. Nifedipine plays a role in increase of hydrophobic property, swelling degree and regular surface as well as decrease of surface rough of the nanoparticles. The PLA/CS/nifedipine nanoparticles are dissolved in the solutions with pH 6.8, pH 4.5 and pH 1.2. The In Vivo test of PLA/CS nanoparticles loading nifedipine on mice was evaluated by the change in diastolic pressure, systolic pressure, arterial pressure and heart rate. The obtained results confirm that the PLA/CS nanoparticles loading nifedipine is suitable to apply in the treatment of hypertension patients lately.

239+240Pu, 90Sr and 137Cs inventories in surface soils of Vietnam

Fallout 239+240Pu, 238Pu, 90Sr and 137Cs inventories in surface soils were measured for 20 locations in northern Vietnam yielding the mean values (+/- standard error) of 26.5+/-3.8 Bq m(-2) for 239+240Pu, 1048+/-143 Bq m(-2) for 137Cs and 212+/-28 Bq m(-2) for 90Sr. The concentrations of 137Cs and plutonium isotopes strongly correlate with each other resulting in a stable 239+240Pu/137Cs inventory ratio of 0.025+/-0.002. Among soil parameters, organic matter and fulvic acids strongly correlate with caesium and plutonium isotopes, especially in the 0-10 cm layer. 137Cs and 239+240Pu are distributed rather similarly over the 0-10 cm and 10-20 cm layers. At locations with high contents of sand (82-93%) along the South China Sea coast, the downward percolation by rainwater results in a higher accumulation of 239+240Pu and 137Cs in the 10-20 cm layer. The mean 137Cs/ 90Sr inventory ratio is 9.3+/-2.2, and the correlation is weak between these isotopes.

Reactive nitrogen intermediates and outcome in severe adult malaria

The role of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) in the pathophysiology of severe falciparum malaria remains unclear. We conducted a retrospective case-control study of Vietnamese adults with severe malaria to determine the relationship between outcome and admission plasma reactive nitrogen intermediates (RNI), the stable metabolites of NO. The study was designed to take into account the potential confounders of recent dietary nitrogen intake and renal function. Seventy-six patients who died from severe malaria were matched for age and sex with 76 survivors from a prospectively studied series of 560 patients. Median untransformed unadjusted plasma RNI levels were slightly higher in fatal cases (45 mumol/L, range 0-482) than in survivors (24.1 mumol/L, range 1.4-466) (P = 0.031, Wilcoxon signed-rank). There was a significant positive correlation between RNI levels and plasma creatinine (Spearman's rho = 0.35, P < 0.0001), and the addition of plasma creatinine as a covariate in a multivariate analysis abolished the trend towards higher RNI levels in fatal cases (P for the coefficient for RNI = 0.96). There was no association between RNI levels and either depth of coma on admission or time to regain consciousness. These findings do not support a pivotal role for systemic generation of NO in the pathogenesis of severe malaria in general, or cerebral malaria in particular.