Vanadium Uptake Research Articles

Vanadium Accumulation and Reduction by Vanadium-Accumulating Bacteria Isolated from the Intestinal Contents of Ciona robusta

The sea squirt Ciona robusta (formerly Ciona intestinalis type A) has been the subject of many interdisciplinary studies. Known as a vanadium-rich ascidian, C. robusta is an ideal model for exploring microbes associated with the ascidian and the roles of these microbes in vanadium accumulation and reduction. In this study, we discovered two bacterial strains that accumulate large amounts of vanadium, CD2-88 and CD2-102, which belong to the genera Pseudoalteromonas and Vibrio, respectively. The growth medium composition impacted vanadium uptake. Furthermore, pH was also an important factor in the accumulation and localization of vanadium. Most of the vanadium(V) accumulated by these bacteria was converted to less toxic vanadium(IV). Our results provide insights into vanadium accumulation and reduction by bacteria isolated from the ascidian C. robusta to further study the relations between ascidians and microbes and their possible applications for bioremediation or biomineralization.

Facing diseases caused by trypanosomatid parasites: rational design of multifunctional oxidovanadium(IV) complexes with bioactive ligands

Searching for new prospective drugs against Chagas disease (American trypanosomiasis) and Leishmaniasis, a series of five heteroleptic vanadium compounds, [VIVO(L-H)(mpo)], where L are 8-hydroxyquinoline derivatives and mpo is 2-mercaptopyridine N-oxide, are synthesized and characterized. Comprehensive characterizations are conducted in solid state and in solution. The compounds are evaluated on epimastigotes and trypomastigotes of Trypanosoma cruzi and in promastigotes of Leishmania infantum, alongside on VERO cells, as a mammalian cell model. The compounds exhibit activity against both forms of T. cruzi and promastigotes of L. infantum, with the trypomastigote infective stage of T. cruzi displaying the highest sensitivity. The most selective vanadium compound [VIVO(L2-H)(mpo)], with L2 = 5-chloro-7-iodo-8-hydroxyquinoline, globally shows adequate selectivity towards the parasite and was selected to carry out further in-depth biological studies. [VIVO(L2-H)(mpo)] significantly impacted the infection potential of cell-derived trypomastigotes and hindered the replication of the T. cruzi amastigote form. Low total vanadium uptake by T. cruzi parasites and preferential accumulation in the soluble proteins fraction, with negligible localization in the DNA fraction, are determined. A trypanocide effect is observed across various concentrations of the compound. The generation of oxidative stress and the induction of mitochondria-dependent apoptosis are proposed as the main mechanisms of the parasite’s death by the VIVO compounds. Both theoretical predictions and experimental data support the hypothesis that inhibiting the parasite-specific enzyme NADH-fumarate reductase activity plays a crucial role in the trypanocidal action of these complexes. Globally, [VIVO(L-H)(mpo)] complexes could be considered interesting anti-T. cruzi agents that deserve further research.

Uptake of vanadium and its intracellular metabolism by Coprinellus truncorum mycelial biomass

BackgroundFungi absorb and solubilize a broad spectrum of heavy metals such as vanadium (V), which makes them a main route of its entry into the biosphere. V as vanadate (V5+) is a potential medical agent due to its many metabolic actions such as interaction with phosphates in the cell, and especially its insulin-mimetic activity. Antidiabetic activity of V-enriched fungi has been studied in recent years, but the biological and chemical bases of vanadium action and status in fungi in general are poorly understood, with almost no information on edible fungi. MethodsThis manuscript gives a deeper insight into the interaction of V5+ with Coprinellus truncorum, an edible autochthonous species widely distributed in Europe and North America. Vanadium uptake and accumulation as V5+ was studied by 51V NMR, while the reducing abilities of the mycelium were determined by EPR. 31P NMR was used to determine its effects on the metabolism of phosphate compounds, with particular focus on phosphate sugars identified using HPLC. ResultsVanadate enters the mycelium in monomeric form and shows no immediate detrimental effects on intracellular pH or polyphosphate (PPc) levels, even when applied at physiologically high concentrations (20 mM Na3VO4). Once absorbed, it is partially reduced to less toxic vanadyl (V4+) with notable unreduced portion, which leads to a large increase in phosphorylated sugar levels, especially glucose-1-phosphate (G1P) and fructose-6-phosphate (F6P). ConclusionsPreservation of pH and especially PPc reflects maintenance of the energy status of the mycelium, i.e., its tolerance to high V5+ concentrations. Rise in G1P and F6P levels implies that the main targets of V5+ are most likely phosphoglucomutase and phosphoglucokinase(s), enzymes involved in early stages of G6P transformation in glycolysis and glycogen metabolism. This study recommends C. truncorum for further investigation as a potential antidiabetic agent.

Vanadium uptake and storage in the fabrication and function of mussel byssus

The preferential use of vanadium to form metal–protein cross-links by Mytilus edulis mussels in their byssal fibers was highlighted through a cross-disciplinary study combining histology, spectroscopy, rheology, and computational modeling.

The removal of toxic metals from liquid effluents by ion exchange resins. Part XVIII: Vanadium(V)/H+/Amberlite 958

The ion exchange resin Amberlite 958 was used to investigate its behaviour on the removal of hazardous vanadium(V) from aqueous media. This investigation was carried out under various hydrodynamic conditions and chemical conditions, such as variation of the stirring speed, variation of the pH of the aqueous solution, resin dosage, initial vanadium(V) in the aqueous solution, and temperature. Vanadium(V) uptake onto the resin was highly dependent on the pH of the solution, and thus, to the vanadium(V) speciation in this phase; the ion exchange process had an endothermic character. The experimental data, under different experimental conditions, were fitted to various models: kinetics (stirring speed), rate law (vanadium concentration) and model isotherms (resin dosage). Multiwalled carbon nanotubes were also investigated on vanadium(V) removal from the solution. Vanadium(V) loaded onto the resin can be eluted under acidic conditions.

Effect of kinetics, pH, aqueous speciation and presence of ferrihydrite on vanadium (V) uptake by allophanic and smectitic clays

Sorption of oxyanions, such as pentavalent vanadium (V(V)), by reactive, poorly crystallized clay minerals and Fe-(hydr)oxides surfaces significantly contributes to the nutrient and pollutant transport in soils. However, only a few studies yet exist, which evaluate and quantify the role of such common soil substituents on V sorption. In this contribution, the uptake of V(V) by allophane with molar Al/Si ratios of 1.5 (ALO-1) and 1.8 (ALO-2) and by montmorillonite-beidellite (MNT-BEI) clays was investigated using kinetic and equilibrium experiments. The effects of pH, V speciation, contact time and presence of 6-line ferrihydrite (FHY) were evaluated at 25 °C. The clayey substrates with(out) FHY were characterized using X-ray diffraction, X-ray fluorescence, high-resolution transmission electron microscopy with energy-dispersive X-ray spectroscopy and selected area electron diffraction and N2-Brunauer-Emmett-Teller physisorption methods. Fast (≥ 15 min) adsorption of V(V) was followed by pseudo-first-order reaction kinetics and progressed through instantaneous diffusion processes at the exterior surface. Subsequently, V(V) transportation and adsorption within the interior substrate, as inferred from Weber-Morris intra-particle diffusion model plots, was observed. The presence of FHY had a positive effect on V(V) adsorption ([V]T = 0.02 mmol/L), which followed in the order MNT-BEI-FHY and MNT-BEI (≥ 95% removal), ALO-1-FHY and ALO-2-FHY (≥ 90% removal), ALO-1 (≥ 70% removal) and ALO-2 (≥ 40% removal) in the pH range from ~6 to ~8. The results of this study demonstrate the high affinity of ferrihydrite as well as allophanic and smectitic clays for V(V) adsorption, suggesting that these components can limit the V mobility in soils over a wide pH range.

Vanadium Toxicity Induced Changes in Growth, Antioxidant Profiling, and Vanadium Uptake in Pepper (Capsicum annum L.) Seedlings

Heavy metal contamination is one of the current serious environmental and agricultural soil issues, and it is mainly due to anthropogenic activities. Vanadium (V) is found in low concentrations in a wide range of plants and is widely distributed in soils. The current study aimed to determine how pepper seedlings responded to various V concentrations, as well as the detrimental effects of V on growth, root morphological traits, photosynthetic performance, reactive oxygen species (ROS), osmolytes production, antioxidant enzyme activities, and V uptake. Pepper seedlings (5 weeks old) were grown in hydroponic culture with six V levels (0, 10, 20, 30, 40, and 50 mg L−1 NH4VO3). After two weeks of V treatment, low level of V (10, 20 mg L−1) enhanced the growth status, conversely higher V (30, 40, and 50 mg L−1) level reduced the growth. The leaf gas exchange elements, pigments molecules, and root growth characteristics are also affected by higher V concentrations. Moreover, V uptake was higher in roots than in the shoot of pepper seedlings. Similarly, osmolytes content, ROS production, and antioxidant enzymes activities were significantly improved under V stress. Concluding, lower V (10, 20 mg L−1) concentration positively affected pepper growth, and higher V (30, 40, and 50 mg L−1) concentration had a detrimental effect on pepper physiological and biochemical mechanisms.

Heteroleptic Oxidovanadium(V) Complexes with Activity against Infective and Non-Infective Stages of Trypanosoma cruzi.

Five heteroleptic compounds, [VVO(IN-2H)(L-H)], where L are 8-hydroxyquinoline derivatives and IN is a Schiff base ligand, were synthesized and characterized in both the solid and solution state. The compounds were evaluated on epimastigotes and trypomastigotes of Trypanosoma cruzi as well as on VERO cells, as a mammalian cell model. Compounds showed activity against trypomastigotes with IC50 values of 0.29–3.02 μM. IN ligand and the new [VVO2(IN-H)] complex showed negligible activity. The most active compound [VVO(IN-2H)(L2-H)], with L2 = 5-chloro-7-iodo-8-hydroxyquinoline, showed good selectivity towards the parasite and was selected to carry out further biological studies. Stability studies suggested a partial decomposition in solution. [VVO(IN-2H)(L2-H)] affects the infection potential of cell-derived trypomastigotes. Low total vanadium uptake by parasites and preferential accumulation in the soluble proteins fraction were determined. A trypanocide effect was observed when incubating epimastigotes with 10 × IC50 values of [VVO(IN-2H)(L2-H)] and the generation of ROS after treatments was suggested. Fluorescence competition measurements with DNA:ethidium bromide adduct showed a moderate DNA interaction of the complexes. In vivo toxicity study on C. elegans model showed no toxicity up to a 100 μM concentration of [VVO(IN-2H)(L2-H)]. This compound could be considered a prospective anti-T. cruzi agent that deserves further research.

Characterization of Dimeric Vanadium Uptake and Species in Nafion™ and Novel Membranes from Vanadium Redox Flow Batteries Electrolytes

A core component of energy storage systems like vanadium redox flow batteries (VRFB) is the polymer electrolyte membrane (PEM). In this work, the frequently used perfluorosulfonic-acid (PFSA) membrane Nafion™ 117 and a novel poly (vinylidene difluoride) (PVDF)-based membrane are investigated. A well-known problem in VRFBs is the vanadium permeation through the membrane. The consequence of this so-called vanadium crossover is a severe loss of capacity. For a better understanding of vanadium transport in membranes, the uptake of vanadium ions from electrolytes containing Vdimer(IV–V) and for comparison also V(II), V(III), V(IV), and V(V) by both membranes was studied. UV/VIS spectroscopy, X-ray absorption near edge structure spectroscopy (XANES), total reflection X-ray fluorescence spectroscopy (TXRF), inductively coupled plasma optical emission spectrometry (ICP-OES), and micro X-ray fluorescence spectroscopy (microXRF) were used to determine the vanadium concentrations and the species inside the membrane. The results strongly support that Vdimer(IV–V), a dimer formed from V(IV) and V(V), enters the nanoscopic water-body of Nafion™ 117 as such. This is interesting, because as of now, only the individual ions V(IV) and V(V) were considered to be transported through the membrane. Additionally, it was found that the Vdimer(IV–V) dimer partly dissociates to the individual ions in the novel PVDF-based membrane. The Vdimer(IV–V) dimer concentration in Nafion™ was determined and compared to those of the other species. After three days of equilibration time, the concentration of the dimer is the lowest compared to the monomeric vanadium species. The concentration of vanadium in terms of the relative uptake λ = n(V)/n(SO3) are as follows: V(II) [λ = 0.155] > V(III) [λ = 0.137] > V(IV) [λ = 0.124] > V(V) [λ = 0.053] > Vdimer(IV–V) [λ = 0.039]. The results show that the Vdimer(IV–V) dimer needs to be considered in addition to the other monomeric species to properly describe the transport of vanadium through Nafion™ in VRFBs.

Vanadium(V/IV)-Transferrin Binding Disrupts the Transferrin Cycle and Reduces Vanadium Uptake and Antiproliferative Activity in Human Lung Cancer Cells.

The role of vanadium binding to transferrin (Tf) in the biological activities of vanadium-based drugs is a matter of considerable debate. In order to determine whether V(V) and/or V(IV) binding to Tf (in apo, monoferric(III), and diferric(III) forms) enhances or inhibits biological activities, cellular V uptake and in vitro antiproliferative activity were examined in the presence and absence of different forms of Tf and other biomolecules under normoxic conditions. These data were combined with studies on V-Tf binding in cell culture medium and its role in Tf interactions with transferrin receptor 1 (TfR1), using the biolayer interferometry (BLI) model of the Tf cycle that was developed in our group. The results showed that both V(V) and V(IV) oxidation states efficiently bind to vacant Fe(III) binding sites of Tf even in the presence of a 20-fold molar excess of albumin, although V does not displace Tf-bound Fe(III) under these conditions. Binding of V(V) or V(IV) to Tf in cell culture medium drastically reduced its cellular uptake and antiproliferative activity in the A549 (human lung cancer) cell line that expresses TfR1. BLI and gel electrophoresis studies showed that V(V/IV) binding to partially Fe(III) saturated Tf did not enhance the affinity of Tf binding to TfR1 at pH 7.4 but did disrupt Tf conformational changes under endosome-mimicking conditions (pH 5.6, 0.10 mM citrate). Hence, it is postulated that the absence of a significant cellular uptake of Tf-bound V(V/IV) is likely to be due to the return of undissociated V(V/IV)-Tf adducts to the cell surface after the endosomal step. Collectively, these data show that the biotransformation of V-based drugs leads to V(V/IV)-Tf binding in the blood serum and inhibits, rather than enhances, the biological activity of such drugs under aerobic conditions. These results indicate that the design of V-based drugs that are stable enough to survive in the blood, enter cells intact, and release the active components intracellularly is likely to be required for their clinical success.

Brain metal distribution and neuro-inflammatory profiles after chronic vanadium administration and withdrawal in mice

Vanadium is a potentially toxic environmental pollutant and induces oxidative damage in biological systems including the central nervous system. Its deposition in brain tissue may be involved in the pathogenesis of certain neurological disorders which after prolonged exposure can culminate into more severe pathology. Most studies on vanadium neurotoxicity have been done after acute exposure but in reality some populations are exposed for a lifetime. This work was designed to ascertain neurodegenerative consequences of chronic vanadium administration and to investigate the progressive changes in the brain after withdrawal from vanadium treatment. A total of 85 male BALB/c mice were used for the experiment and divided into three major groups of vanadium treated (intraperitoneally (i.p) injected with 3 mg/kg body weight of sodium metavanadate and sacrificed every 3 months till 18 months); matched controls; and animals that were exposed to vanadium for three months and thereafter the metal was withdrawn. Brain tissues were obtained after animal sacrifice. Sagittal cut sections of paraffin embedded tissue (5μm) were analysed by the Laser ablation-inductively coupled plasma-mass spectrometry (LA – ICP – MS) to show the absorption and distribution of vanadium metal. Also, Heamatoxylin and Eosin (H&E) staining of brain sections, and immunohistochemistry for Microglia (Iba-1), Astrocytes (GFAP), Neurons (Neu-N) and Neu-N + Dapi double labelling immunofluorescence were observed for morphological and morphometric parameters. The LA – ICP – MS results showed progressive increase in vanadium uptake with time in different brain regions with prediction for regions like the olfactory bulb, brain stem and cerebellum. The withdrawal brains still show presence of vanadium metal in the brain slightly more than the controls. There were morphological alterations (of the layering profile, nuclear shrinkage) in the prefrontal cortex, cellular degeneration (loss of dendritic arborization) and cell death in the Hippocampal CA1 pyramidal cells and Purkinje cells of the cerebellum, including astrocytic and microglial activation in vanadium exposed brains which were all attenuated in the withdrawal group . With exposure into old age, the evident neuropathology was microgliosis, while progressive astrogliosis became more attenuated. We have shown that chronic administration of vanadium over a lifetime in mice resulted

Equilibrium and Dynamic Absorption of Electrolyte Species in Cation/Anion Exchange Membranes of Vanadium Redox Flow Batteries.

Vanadium redox flow batteries (VRFBs) rely on ion exchange membranes (IEMs) to separate the positive and negative compartments while maintaining electrical neutrality of the cell, by allowing the transport of ionic charge carriers. Cation exchange membranes (CEMs) and anion exchange membranes (AEMs), the two principal types of IEM, have both been employed in VRFBs. The performance of these IEMs can be influenced by the absorption of species from the electrolyte. In this study, a typical commercial CEM (Nafion 117) and AEM (FAP 450), were examined with respect to vanadium uptake, after exposure to electrolyte at different states of charge. The two types of membrane were found to behave very differently, with the AEM showing very high selectivity for VV , which resulted in a significant increase in area-specific resistivity. In contrast, the CEM absorbed VII more strongly than vanadium in other oxidation states. These findings are essential for the development of an effective membrane for VRFB applications.

Effects of Vanadium and Nickel on Morphological Characteristics and on Vanadium and Nickel Uptake by Shoots of Mojito (Mentha × villosa) and Lavender (Lavandula anqustifolia)

Vanadium and Nickel may enter the human food chain through medicinal and culinary plants which in great doses are toxic to human, so it is important to determine their potential toxicity and health risk. Therefore, the objective of this work was to study the effects of Vanadium and Nickel on morphological characteristics and on Vanadium and Nickel uptake by shoots of mojito (Mentha × vilosa) and lavender (Lavandula anqustifolia). A completely randomized block design with five Vanadium treatments (0, 5, 10, 20, 40 mg V L-1) and five replications per treatment and another one with five Nickel treatments (0, 5, 10, 20 and 40 mg Ni L-1) and five replications per treatment for mojito and lavender were conducted in pots. No visible toxic or inhibitory symptoms were observed on the plants due to the increasing amounts of Vanadium or Nickel. Shoot dry matter and root dry matter of mojito and lavender decreased with increasing Vanadium rates. Vanadium uptake by shoots of mojito and lavender increased linearly with increasing Vanadium rates. Nickel uptake by shoots of lavender increased linearly with increasing rates of Nickel. Mojito is a Nickel accumulator.

Physiological and anthocyanin biosynthesis genes response induced by vanadium stress in mustard genotypes with distinct photosynthetic activity

The present study aimed to elucidate the photosynthetic performance, antioxidant enzyme activities, anthocyanin contents, anthocyanin biosynthetic gene expression, and vanadium uptake in mustard genotypes (purple and green) that differ in photosynthetic capacity under vanadium stress. The results indicated that vanadium significantly reduced photosynthetic activity in both genotypes. The activities of the antioxidant enzymes were increased significantly in response to vanadium in both genotypes, although the purple exhibited higher. The anthocyanin contents were also reduced under vanadium stress. The anthocyanin biosynthetic genes were highly expressed in the purple genotype, notably the genes TT8, F3H, and MYBL2 under vanadium stress. The results indicate that induction of TT8, F3H, and MYBL2 genes was associated with upregulation of the biosynthetic genes required for higher anthocyanin biosynthesis in purple compared with the green mustard. The roots accumulated higher vanadium than shoots in both mustard genotypes. The results indicate that the purple mustard had higher vanadium tolerance.

Effect of Membrane Pretreatment on the Mass Transport of Vanadium Redox Flow Batteries

Vanadium redox flow batteries (VRFBs) offer a scalable, long lasting, highly efficient means of energy storage and are a good option for large scale energy storage systems that can work on hand with renewable energy sources such as wind and solar farms. The proton exchange membrane that separates the negative and positive electrodes is a fundamental part of the system, since it allows the diffusion of H+ ions between electrodes to make possible the oxidation/reduction reactions in the half cells.1 In VRFBs the membrane electrolyte is desired to have high proton conductivity, low vanadium permeability to avoid battery discharge caused by vanadium crossover and good durability. The most common membrane used in VRFBs has been Nafion due to its success in fuel cells. Previous work in our laboratory suggests that other membranes offer improved performance.2,3 However, in a VRFB the working environment differs greatly from that of a fuel cell, for example, the membrane can adsorb electrolyte species other than protons and the high electrolyte concentration will tend to dehydrate the membrane. These conditions can substantially affect the membrane’s conductivity as well as other transport properties. In the flow battery, the trade-off between membrane conductivity and species transport across the membrane is key and is largely driven by the tendency of the membrane to imbibe different solution components as well as their intrinsic mobility. Our group has developed a core set of measurements for membrane characterization that includes conductivity, porosity, acid, water and vanadium uptake, and vanadium permeability.2,4 In this work we studied a series of 3M ionomer membranes, conditioned in solutions of different concentrations of sulfuric acid and vanadium. Membranes were tested as received and also after boiling them in water to expand the polymer channels by hydrating the ionic clusters.5 The effect of channel expansion in the polymer electrolyte was studied as function of the membranes equivalent weight. In addition, a set of membranes was subjected to heat treatments near the polymer glass transition temperature, to determine the temperature effect on the membranes properties. Boiling the membranes dramatically increases their conductivity, porosity, water, acid and vanadium uptake, which is ideal for VRFBs, but also increases the vanadium permeability which is directly related to the undesired crossover. Figure 1, shows an example of how the membrane porosity, which is determined from density measurements obtained by gas pycnometry, is affected in a 3M825EW membrane. The boiled membrane shows higher porosity compared to that of the as received membrane. Higher porosity is an indication of the channels expansion in the membrane after boiling. Acknowledgements We would like to thank Dr. Greg Haugen and Dr. Tyler Matthews at 3M company for providing the membranes and funding for this study. References M. Sukkar, T., Skyllas-Kazacos, J. Memb. Sci., 222, 249–264 (2003).Z. Tang et al., J. Electrochem. Soc., 161, A1860–A1868 (2014).R. A. Elgammal, Z. Tang, C.-N. Sun, J. Lawton, and T. A. Zawodzinski, Electrochim. Acta, 237, 1–11 (2017)J. S. Lawton et al., J. Electrochem. Soc., 163, A5229–A5235 (2016).T. E. S. and S. G. Thomas A. Zawodzinski Jr., Charles Derouin, Susan Radzinski, Ruth J. Sherman, Van T. Smith, J. Electrochem. Soc., 140, 1041–1047 (1993). Figure 1

Vanadium in landscape components of western Transbaikalia

Vanadium in soil-forming rocks, soils, and vegetation of forest-steppe, steppe, and dry-steppe landscapes of Transbaikalia has been studied. The mean element contents in rocks and soils are equal to its mean natural abundances (clarke values). The content of vanadium in soils is strictly determined by its content in parent materials; its dependence on the vanadium concentration in plants and on the soil pH and humus is less pronounced. With respect to the coefficient of biological uptake by plants, vanadium is assigned to the group of elements of slight accumulation (0.10–0.33) on mineral soils and of moderate accumulation (1.1–1.5) on peat bog soils. The mean vanadium concentration in steppe, meadow, and cultivated vegetation exceeds the norm for animals by 1.7–2.6 times but does not rich toxic levels. Vanadium uptake by plants is most intensive in meadow cenoses and is less intensive in dry-steppe cenoses.

Vanadium removal by organo-zeolites and iron-based products from contaminated natural water

Natural water with a high specific ultraviolet absorbance (SUVA) value (4.3) and high vanadium concentration (1.2–1.9 mg/l) was investigated for vanadium(V) removal through sorption using solid sorbents and co-precipitation with a ferric sulphate coagulant. Although there are studies on vanadium removal by sorption and co-precipitation, the removal of vanadium in the presence of natural organic matter has not been adequately addressed. In the sorption method, hexadecyltrimethylammonium bromide (HDTMA) modified clinoptilolite (Cp) and synthetic zeolite (Na-P1), and ferric oxyhydroxide (CFH-12) were tested as sorbents. In the co-precipitation method, vanadium removal may occur simultaneously with the coagulation process of humic substances. Co-precipitation with iron was proven to be more efficient than sorbent-based processes. A ferric sulphate coagulant dosage (as product) of 75 mg/l resulted in a residual vanadium concentration of 70–80 μg/l and vanadium removal closely followed the removal of humic substances. This might be related to the binding of vanadium by the humic substances. Regarding sorbents, 1–2 g/l dosages of Na-P1 (at pH ∼6) and CFH-12 (pH 3.7–4.7) were required to reach a low vanadium concentration. A much higher dosage was required for Cp, which can be explained by the lower loading of HDTMA on the zeolite surface. Na-P1 increased the pH of the treated water whereas CFH-12 decreased the pH. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses revealed that the pH change was due to the leaching of hydroxides and calcite from the Na-P1 and jarosite from the CFH-12. The organo-zeolites exhibited fast kinetics. The surface binding of vanadium and vanadium-humic substances can be regarded as the main mechanism. For CFH-12, the diffusion of vanadium into pores was a significant, albeit slow mechanism, in addition to the sorption on the external surface. The humic substances present in natural water significantly affected the mechanism of vanadium uptake. The XPS data confirmed the strong binding of organic matter on CFH-12 whereas organic matter was only weakly bound to the organo-zeolites.

Speciation in aqueous solution and interaction with low and high molecular mass blood bioligands of [V IV O(oda)(H 2 O) 2 ], a V compound with in vitro anticancer activity

Abstract In this work the speciation in aqueous solution of the compound [V IV O(oda)(H 2 O) 2 ], where oda is oxydiacetate dianion (OOCCH 2 ) 2 O, which shows in vitro anticancer activity, was studied. Its interaction with the two serum bioligands with highest affinity for V IV , lactic (Hlact) and citric (H 3 citr) acid, and with the two proteins candidate to participate to the transport of V IV O compounds in the organism, transferrin (hTf) and albumin (HSA), was also examined. The study was carried out with the combined application of spectroscopic (Electron Paramagnetic Resonance, EPR), analytical (pH-potentiometry) and computational (Density Functional Theory, DFT) methods. The results showed that in aqueous solution [VO(oda)(H 2 O) 2 ] undergoes hydrolysis above pH 4–5 with formation of the EPR-active species [(VO) 2 (oda) 2 (OH) 2 ] 2− around pH 6 and of [(VO) 2 (OH) 5 ] − at physiological pH. DFT calculations suggested that the most stable isomers of 1:1 species are the hexa-coordinated OC -6-23 with a mer arrangement of oda – similar to that observed in the solid state – and the penta-coordinated SPY -5-14, whereas for 1:2 species the fac arrangement of oda is favored. Citrate is able to displace completely the oda ligand in [VO(oda)(H 2 O) 2 ] and only the dinuclear species [(VO) 2 (citrH -1 ) 2 ] 4− was detected at pH 7.4, while with lactate the formation of a mixed complex V IV O–oda–lact was observed. [VO(oda)(H 2 O) 2 ] interacts with apo-transferrin forming a mixed complex (VO)(hTf)(oda) where vanadium is bound in the iron sites and oda behaves as a synergistic anion, while with albumin no interaction was revealed. Model calculations suggest that when [VO(oda)(H 2 O) 2 ] is administered orally (concentration ca . 1–10 μM) or by injection (concentration approximately in the range 10–100 μM), (VO)(hTf) and (VO) 2 (hTf) should be formed; these species could reach the target organs and be recognized by the hTf receptors of the cells, favoring the vanadium uptake.

Successful Coupling of a Bis-Amidoxime Uranophile with a Hydrophilic Backbone for Selective Uranium Sequestration.

The amidoxime group (-RNH2NOH) has long been used to extract uranium from seawater on account of its high affinity toward uranium. The development of tunable sorbent materials for uranium sequestration remains a research priority as well as a significant challenge. Herein, we report the design, synthesis, and uranium sorption properties of bis-amidoxime-functionalized polymeric materials (BAP 1-3). Bifunctional amidoxime monomers were copolymerized with an acrylamide cross-linker to obtain bis-amidoxime incorporation as high as 2 mmol g-1 after five synthetic steps. The resulting sorbents were able to uptake nearly 600 mg of uranium per gram of polymer after 37 days of contact with a seawater simulant containing 8 ppm uranium. Moreover, the polymeric materials exhibited low vanadium uptake with a maximum capacity of 128 mg of vanadium per gram of polymer. This computationally predicted and experimentally realized selectivity of uranium over vanadium, nearly 5 to 1 w/w, is one of the highest reported to date and represents an advancement in the rational design of sorbent materials with high uptake capacity and selectivity.

Brain Metal Distribution and Neuro-Inflammatory Profiles after Chronic Vanadium Administration and Withdrawal in Mice.

Vanadium is a potentially toxic environmental pollutant and induces oxidative damage in biological systems including the central nervous system (CNS). Its deposition in brain tissue may be involved in the pathogenesis of certain neurological disorders which after prolonged exposure can culminate into more severe pathology. Most studies on vanadium neurotoxicity have been done after acute exposure but in reality some populations are exposed for a lifetime. This work was designed to ascertain neurodegenerative consequences of chronic vanadium administration and to investigate the progressive changes in the brain after withdrawal from vanadium treatment. A total of 85 male BALB/c mice were used for the experiment and divided into three major groups of vanadium treated (intraperitoneally (i.p.) injected with 3 mg/kg body weight of sodium metavanadate and sacrificed every 3 months till 18 months); matched controls; and animals that were exposed to vanadium for 3 months and thereafter the metal was withdrawn. Brain tissues were obtained after animal sacrifice. Sagittal cut sections of paraffin embedded tissue (5 μm) were analyzed by the Laser ablation-inductively coupled plasma-mass spectrometry (LA–ICP–MS) to show the absorption and distribution of vanadium metal. Also, Haematoxylin and Eosin (H&E) staining of brain sections, and immunohistochemistry for Microglia (Iba-1), Astrocytes (GFAP), Neurons (Neu-N) and Neu-N + 4′,6-diamidine-2′-pheynylindole dihydrochloride (Dapi) Immunofluorescent labeling were observed for morphological and morphometric parameters. The LA–ICP–MS results showed progressive increase in vanadium uptake with time in different brain regions with prediction for regions like the olfactory bulb, brain stem and cerebellum. The withdrawal brains still show presence of vanadium metal in the brain slightly more than the controls. There were morphological alterations (of the layering profile, nuclear shrinkage) in the prefrontal cortex, cellular degeneration (loss of dendritic arborization) and cell death in the Hippocampal CA1 pyramidal cells and Purkinje cells of the cerebellum, including astrocytic and microglial activation in vanadium exposed brains which were all attenuated in the withdrawal group. With exposure into old age, the evident neuropathology was microgliosis, while progressive astrogliosis became more attenuated. We have shown that chronic administration of vanadium over a lifetime in mice resulted in metal accumulation which showed regional variabilities with time. The metal profile and pathological effects were not completely eliminated from the brain even after a long time withdrawal from vanadium metal.