Pentavalent Arsenic Research Articles

Metalloproteomics Reveals Multi-Level Stress Response in Escherichia coli When Exposed to Arsenite.

The arsRBC operon encodes a three-protein arsenic resistance system. ArsR regulates the transcription of the operon, while ArsB and ArsC are involved in exporting trivalent arsenic and reducing pentavalent arsenic, respectively. Previous research into Agrobacterium tumefaciens 5A has demonstrated that ArsR has regulatory control over a wide range of metal-related proteins and metabolic pathways. We hypothesized that ArsR has broad regulatory control in other Gram-negative bacteria and set out to test this. Here, we use differential proteomics to investigate changes caused by the presence of the arsR gene in human microbiome-relevant Escherichia coli during arsenite (AsIII) exposure. We show that ArsR has broad-ranging impacts such as the expression of TCA cycle enzymes during AsIII stress. Additionally, we found that the Isc [Fe-S] cluster and molybdenum cofactor assembly proteins are upregulated regardless of the presence of ArsR under these same conditions. An important finding from this differential proteomics analysis was the identification of response mechanisms that were strain-, ArsR-, and arsenic-specific, providing new clarity to this complex regulon. Given the widespread occurrence of the arsRBC operon, these findings should have broad applicability across microbial genera, including sensitive environments such as the human gastrointestinal tract.

Novel Strategy for Efficient Recovery of CuO-Based Multiple-Metals from Copper Smelter Dust toward CO2 Electrocatalytic Reduction.

Copper smelter dust, a typical hazardous waste that is abundant in valuable heavy metals, holds the potential to be regarded as a promising resource. This study introduces a new approach that integrates chlorination roasting and cascade condensation to efficiently recover heavy metals from copper smelter dust. The findings demonstrate the successful separation of heavy metals (Cu, Pb, and Zn) as chlorides at nearly 100% efficiency while also effectively converting trivalent arsenic (As(III)) into pentavalent arsenic (As(V)) and immobilizing it in the roasting residues, thereby reducing environmental risk. Through the utilization of thermogravimetric mass spectrum analysis and thermodynamic equilibrium calculations, the chlorination process for heavy metals was investigated, revealing both direct and indirect chlorination processes. Additionally, the study resulted in the development of a CuO-based multiple-metals electrocatalyst from the oxidized roasting-recovered heavy metal chlorides, exhibiting significantly enhanced catalytic activity and faradaic efficiency for the electroreduction of CO2 into CO and CH4 compared to pure CuO electrocatalyst under similar electrocatalytic conditions. Overall, this work presents a sustainable and scalable method and new insights for addressing environmental risks while repurposing copper smelter dust.

Application of biohybrid membranes for arsenic and chromium removal and their impact on pollutant accumulation in soybean (Glycine max L.) seedlings.

Chromium and arsenic are among the priority pollutants to be controlled by regulatory and health agencies due to their ability to accumulate in food chains and the harmful effects on health resulting from the ingestion of food contaminated with metals and metalloids. In the present work, four biohybrid membrane systems were developed as alternatives for the removal of these pollutants, three based on polyvinyl alcohol polymeric mesh (PVA, PVA-magnetite, PVA L-cysteine) and one based on polybutylene adipate terephthalate (PBAT), all associated with bioremediation agents. The efficiency of the bioassociation process was assessed through count methods and microscopy. The removal capacity of these systems was evaluated in synthetic liquid medium, both in the absence and in the presence of soybean (Glycine max L.) seedlings. The content of chromium and arsenic was also analyzed in aerial and hypogeous tissues of seedlings grown on contaminated solid substrate. PVA and PVA-magnetite biohybrid membranes showed the highest removal rates, between 57 and 75% of the initial arsenic content and more than 80% of the initial chromium content after 48h of treatment, when evaluated in synthetic liquid media with initial concentrations of 2.5ppm of pentavalent arsenic and 5ppm of hexavalent chromium, both in presence and absence of seedlings. PVA and PBAT promoted a significant reduction of arsenic translocation to the aerial parts, generally edible, of this crop of agronomic interest. The systems tested showed a high potential for biotechnological applications in matrices affected by the presence of arsenic and chromium.

Effect of long-term inorganic arsenic exposure on erythropoietin production in vitro

Arsenic is widely present in the environment in trivalent and pentavalent forms; long-term arsenic exposure due to environmental pollution has become a problem. Previous reports have shown that 24-h exposure to arsenate (as pentavalent arsenic) potentiates erythropoietin (EPO) production via reactive oxygen species (ROS) in EPO-producing HepG2 cells. However, the effects of long-term arsenate exposure on EPO production remain unclear. In HepG2 cells subcultured for 3 weeks in the presence of arsenate, EPO mRNA levels were lower than those in untreated cells. Levels of ARSENITE METHYLTRANSFERASE mRNA, as well as those of Nuclear factor erythroid 2-related factor 2, glutathione, and superoxide dismutase proteins, were increased compared to untreated cells, but levels of malondialdehyde were not significantly altered. Thus, long-term exposure to arsenate enhances ROS scavenging, suggesting that the ROS-induced accumulation of EPO mRNA is attenuated by arsenate exposure. The induction of EPO accumulation by hypoxia also was attenuated by long-term arsenate exposure, suggesting an impairment in responsivity of EPO production. Furthermore, mRNA levels of SIRTUIN-1, which affects EPO transcription, were potentiated by long-term arsenate exposure. These results suggest that long-term arsenate exposure has multiple, distinct effects on EPO production in vitro.

Selective and efficient removal of As(III) from water by Ce-Mn oxide-modified biochar: Synergetic role of rapid oxidation and enhanced adsorption

Pre-oxidation of trivalent arsenic (As(III)) to pentavalent arsenic (As(V)) with subsequent in-situ adsorption serves as a viable strategy for the As(III) removal from water environment. Herein, a simple pyrolysis-impregnation-pyrolysis method was used to create the Ce-Mn oxides modified biochar (CMBC) and the as-prepared CMBC was applied to a persulfate (PS) system to establish a multiphase catalytic process for the rapid oxidation of As(III) and efficient adsorption of As(V) in aqueous solution. The maximum adsorption capacity of As(III) arrived up to 162.09 mg g−1 under CMBC/PS system, and the excellent removal performance of As(III) could be achieved in both acidic and alkaline situations (pH ranging from 3 to 11). Ionic strength, natural organic matter, as well as coexisting anions (except for phosphate) and cations did not inhibit As(III) removal in CMBC/PS system. Especially, the adsorption of As(III) under diverse coexisting ions reached adsorption dynamic equilibrium within 90 minutes, implying that the process has relatively fast adsorption kinetics and is resistant to interference. Moreover, the adsorbent could be effortlessly renewed with regenerant while retaining the desired removal rate. Persulfate activated by CMBC generated radical species, however, the free radical trapping experiments, EPR experiments, and electrochemical technique analysis revealed that there existed a non-radical-dominated electron transfer pathway in the CMBC/PS system. The ideal regeneration performance, anti-disturbance ability, and high adsorption capacity imply that CMBC/PS may serve as a promising approach to removal As(III) via adsorption method, and the results also gain insight into the electron transfer pathway in the system.

Characterizing the toxicological responses to inorganic arsenicals and their metabolites in immortalized human bladder epithelial cells.

Arsenic is highly toxic to the human bladder. In the present study, we established a human bladder epithelial cell line that closely mimics normal human bladder epithelial cells by immortalizing primary uroplakin 1B-positive human bladder epithelial cells with human telomerase reverse transcriptase (HBladEC-T). The uroplakin 1B-positive human bladder epithelial cell line was then used to evaluate the toxicity of seven arsenicals (iAsV, iAsIII, MMAV, MMAIII, DMAV, DMAIII, and DMMTAV). The cellular uptake and metabolism of each arsenical was different. Trivalent arsenicals and DMMTAV exhibited higher cellular uptake than pentavalent arsenicals. Except for MMAV, arsenicals were transported into cells by aquaglyceroporin 9 (AQP9). In addition to AQP9, DMAIII and DMMTAV were also taken up by glucose transporter 5. Microarray analysis demonstrated that arsenical treatment commonly activated the NRF2-mediated oxidative stress response pathway. ROS production increased with all arsenicals, except for MMAV. The activating transcription factor 3 (ATF3) was commonly upregulated in response to oxidative stress in HBladEC-T cells: ATF3 is an important regulator of necroptosis, which is crucial in arsenical-induced bladder carcinogenesis. Inorganic arsenics induced apoptosis while MMAV and DMAIII induced necroptosis. MMAIII, DMAV, and DMMTAV induced both cell death pathways. In summary, MMAIII exhibited the strongest cytotoxicity, followed by DMMTAV, iAsIII, DMAIII, iAsV, DMAV, and MMAV. The cytotoxicity of the tested arsenicals on HBladEC-T cells correlated with their cellular uptake and ROS generation. The ROS/NRF2/ATF3/CHOP signaling pathway emerged as a common mechanism mediating the cytotoxicity and carcinogenicity of arsenicals in HBladEC-T cells.

A novel graphene oxide-microalgae hybrid material for the removal of pentavalent arsenic from natural water and industrial wastewater

A novel graphene oxide-microalgae hybrid material for the removal of pentavalent arsenic from natural water and industrial wastewater

Fabrication of Fe3O4@GO@ZIF-8 nanohybrids via in-situ self-assembly with magnetic collectability for efficient adsorption of As(III) and As(V)

Fe3O4@GO@ZIF-8 nanohybrids were successfully fabricated as a novel magnetic graphene adsorbent via in-situ self-assembly of ZIF-8 and graphene oxide (GO) onto magnetic ferroferric oxide nanoparticles. The adsorbent was thoroughly characterized using various techniques. The results showed that Fe3O4@GO@ZIF-8 exhibits strong magnetic properties, abundant functional groups and a large specific surface area of 779.48 m2 g−1. Additionally, the effects of time, pH, initial concentration and temperature on the adsorption performances of Fe3O4@GO@ZIF-8 for trivalent arsenite (As(III)) and pentavalent arsenate (As(V)) were explored. The results revealed that Fe3O4@GO@ZIF-8 possesses fast reaction kinetics (reaching saturation in approximately 180 min for As(III) and 120 min for As(V)), as well as excellent adsorption capabilities (achieving adsorption capacities of 87.621 mg g−1 for As(III) and 113.37 mg g−1 for As(V)). Furthermore, recycling experiments demonstrated that Fe3O4@GO@ZIF-8 exhibits favorable adsorption ability, enabling easy recovery under an applied magnetic field. These results highlight the magnetic properties, good reusability, and adsorption capacity of Fe3O4@GO@ZIF-8, rendering it highly practical for extracting arsenic wastes in harsh environments.

Arsenic species in soil profiles from chemical weapons (CWs) burial sites of China: Contamination characteristics, degradation process and migration mechanism

In this study, soil profiles and pore water from Japanese abandoned arsenic-containing chemical weapons (CWs) burial sites in Dunhua, China were analyzed to understand the distribution of arsenic (As) contamination, degradation, and migration processes. Results of As species analysis showed that the As-containing agents underwent degradation with an average rate of 87.55 ± 0.13%, producing inorganic pentavalent arsenic (As5+) and organic arsenic such as 2-chlorovinylarsonic acid (CVAOA), triphenylarsenic (TPA), and phenylarsine oxide (PAO). Organic arsenic pollutants accounted for 1.27–18.20% of soil As. In the vertical profiles, total As concentrations peaked at about 40–60 cm burial depth, and the surface agricultural soil exhibited moderate to heavy contamination level, whereas the contamination level was insignificant below 1 m, reflecting As migration was relatively limited throughout the soil profile. Sequential extraction showed Fe/Al-bound As was the predominant fraction, and poorly-crystalline Fe minerals adsorbed 33.23–73.13% of soil As. Oxygen-susceptible surface soil formed poorly-crystalline Fe3+ minerals, greatly reducing downward migration of arsenic. However, the reduction of oxidizing conditions below 2 m soil depth may promote As activity and require attention.

Arsenic toxicity: sources, pathophysiology and mechanism.

Arsenic is a naturally occurring element that poses a significant threat to human health due to its widespread presence in the environment, affecting millions worldwide. Sources of arsenic exposure are diverse, stemming from mining activities, manufacturing processes, and natural geological formations. Arsenic manifests in both organic and inorganic forms, with trivalent meta-arsenite (As3+) and pentavalent arsenate (As5+) being the most common inorganic forms. The trivalent state, in particular, holds toxicological significance due to its potent interactions with sulfur-containing proteins. The primary objective of this review is to consolidate current knowledge on arsenic toxicity, addressing its sources, chemical forms, and the diverse pathways through which it affects human health. It also focuses on the impact of arsenic toxicity on various organs and systems, as well as potential molecular and cellular mechanisms involved in arsenic-induced pathogenesis. A systematic literature review was conducted, encompassing studies from diverse fields such as environmental science, toxicology, and epidemiology. Key databases like PubMed, Scopus, Google Scholar, and Science Direct were searched using predetermined criteria to select relevant articles, with a focus on recent research and comprehensive reviews to unravel the toxicological manifestations of arsenic, employing various animal models to discern the underlying mechanisms of arsenic toxicity. The review outlines the multifaceted aspects of arsenic toxicity, including its association with chronic diseases such as cancer, cardiovascular disorders, and neurotoxicity. The emphasis is placed on elucidating the role of oxidative stress, genotoxicity, and epigenetic modifications in arsenic-induced cellular damage. Additionally, the impact of arsenic on vulnerable populations and potential interventions are discussed. Arsenic toxicity represents a complex and pervasive public health issue with far-reaching implications. Understanding the diverse pathways through which arsenic exerts its toxic effects is crucial to developing effective mitigation strategies and interventions. Further research is needed to fill gaps in our understanding of arsenic toxicity and to inform public health policies aimed at minimising exposure.Arsenic toxicity is a crucial public health problem influencing millions of people around the world. The possible sources of arsenic toxicity includes mining, manufacturing processes and natural geological sources. Arsenic exists in organic as well as in inorganic forms. Trivalent meta-arsenite (As3+) and pentavalent arsenate (As5+) are two most common inorganic forms of arsenic. Trivalent oxidation state is toxicologically more potent due to its potential to interact with sulfur containing proteins. Humans are exposed to arsenic in many ways such as environment and consumption of arsenic containing foods. Drinking of arsenic-contaminated groundwater is an unavoidable source of poisoning, especially in India, Bangladesh, China, and some Central and South American countries. Plenty of research has been carried out on toxicological manifestation of arsenic in different animal models to identify the actual mechanism of aresenic toxicity. Therefore, we have made an effort to summarize the toxicology of arsenic, its pathophysiological impacts on various organs and its molecular mechanism of action.

Efficient treatment of smelting wastewater: 3D nickel foam @MOF shatters the previous limitation, enabling high-throughput selective capture of arsenic to form non-homogeneous nuclei

A significant challenge in environmental remediation involves designing adsorbents that can effectively remove arsenic from smelting wastewater. This study aimed to address issues related to Metal-Organic Framework (MOF) pore blockage and insufficient active sites. To do this, we prepared MIL-101(Fe) and MIL-101(Cr) directly on three-dimensional nickel foam (NF) using a sustainable hydrothermal one-pot method. Using the NF as a carrier allowed for a uniform distribution of MIL-101(Fe) and MIL-101(Cr). This increased their contact area with the solution and enhanced the exposure of active sites. We investigated the adsorption capacities of trivalent and pentavalent arsenic by NF/MOFs through experiments and computational simulations. Our findings indicated that NF/MIL-101(Fe) and NF/MIL-101(Cr) adsorbed arsenic at concentrations of 152.65 mg/g and 132.615 mg/g, under conditions of room temperature and pH levels of 7 and 4, respectively. Analysis of the adsorption kinetics and thermodynamics revealed that the adsorption process for both adsorbents was chemical in nature, with monolayer adsorption being predominant. Molecular dynamics results indicated diffusion coefficients of 0.556667 × 10–6 for Fe3+ ions and 0.44 × 10–6 for Cr3+ ions. This suggests that NF/MIL-101(Fe) has a strong adsorption capacity. The proposed adsorption site model accurately predicted arsenic adsorption on the NF/MIL-101(Cr) and NF/MIL-101(Fe) structures. Given these properties, NF/MIL-101(Cr) and NF/MIL-101(Fe) are versatile materials with specificity and storage capacity for arsenic removal from smelting wastewater. Their potential in industrial wastewater purification is promising.

Magnesium Oxide Nanoparticles for the Adsorption of Pentavalent Arsenic from Water: Effects of Calcination.

The occurrence of heavy metal ions in water is intractable, and it has currently become a serious environmental issue to deal with. The effects of calcining magnesium oxide at 650 °C and the impacts on the adsorption of pentavalent arsenic from water are reported in this paper. The pore nature of a material has a direct impact on its ability to function as an adsorbent for its respective pollutant. Calcining magnesium oxide is not only beneficial in enhancing its purity but has also been proven to increase the pore size distribution. Magnesium oxide, as an exceptionally important inorganic material, has been widely studied in view of its unique surface properties, but the correlation between its surface structure and physicochemical performance is still scarce. In this paper, magnesium oxide nanoparticles calcined at 650 °C are assessed to remove the negatively charged arsenate ions from an aqueous solution. The increased pore size distribution was able to give an experimental maximum adsorption capacity of 115.27 mg/g with an adsorbent dosage of 0.5 g/L. Non-linear kinetics and isotherm models were studied to identify the adsorption process of ions onto the calcined nanoparticles. From the adsorption kinetics study, the non-linear pseudo-first order showed an effective adsorption mechanism, and the most suitable adsorption isotherm was the non-linear Freundlich isotherm. The resulting R2 values of other kinetic models, namely Webber-Morris and Elovich, were still below those of the non-linear pseudo-first-order model. The regeneration of magnesium oxide in the adsorption of negatively charged ions was determined by making comparisons between fresh and recycled adsorbent that has been treated with a 1 M NaOH solution.

The ArsQ permease and transport of the antibiotic arsinothricin.

The pentavalent organoarsenical arsinothricin (AST) is a natural product synthesized by the rhizosphere bacterium Burkholderia gladioli GSRB05. AST is a broad-spectrum antibiotic effective against human pathogens such as carbapenem-resistant Enterobacter cloacae. It is a non-proteogenic amino acid and glutamate mimetic that inhibits bacterial glutamine synthetase. The AST biosynthetic pathway is composed of a three-gene cluster, arsQML. ArsL catalyzes synthesis of reduced trivalent hydroxyarsinothricin (R-AST-OH), which is methylated by ArsM to the reduced trivalent form of AST (R-AST). In the culture medium of B. gladioli, both trivalent species appear as the corresponding pentavalent arsenicals, likely due to oxidation in air. ArsQ is an efflux permease that is proposed to transport AST or related species out of the cells, but the chemical nature of the actual transport substrate is unclear. In this study, B. gladioli arsQ was expressed in Escherichia coli and shown to confer resistance to AST and its derivatives. Cells of E. coli accumulate R-AST, and exponentially growing cells expressing arsQ take up less R-AST. The cells exhibit little transport of their pentavalent forms. Transport was independent of cellular energy and appears to be equilibrative. A homology model of ArsQ suggests that Ser320 is in the substrate binding site. A S320A mutant exhibits reduced R-AST-OH transport, suggesting that it plays a role in ArsQ function. The ArsQ permease is proposed to be an energy-independent uniporter responsible for downhill transport of the trivalent form of AST out of cells, which is oxidized extracellularly to the active form of the antibiotic.

Determination of six arsenic species in urine by high-performance liquid chromatography-inductively coupled plasma-mass spectrometr

Objective: Establishing an analysis method for the detection of six arsenic compounds trivalent arsenic, pentavalent arsenic, methyl arsenic, dimethyl arsenic, arsenical choline and arsenical betaine in urine by high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) and providing a theoretical basis for health assessment of arsenic poisoning patients. Methods: HPLC-ICP-MS was used to detect six arsenic compounds with the hamilton PRP-X100 column and aqueous ammonium phosphate in a gradient elution as mobile phase. Results: There was a good linear relationship in the selected range of six arsenic compounds evidenced by a linear correlation coefficient greater than 0.999. The detection limit of 6 arsenic compounds was 0.46~0.57 μg/L, and the minimum quantitative concentration were 1.52~1.91 μg/L. The recovery rates of six arsenic compounds were 96.5%~106.4%, The within-run and between-run relative standard deviation was 2.9%~6.2% and 3.8%~8.7%. Conclusion: The established method with high accuracy and precision is suitable for detecting arsenic levels in urine of occupational arsenic exposure population.

Nano-alumina wrapped carbon microspheres for ultrahigh elimination of pentavalent arsenic and fluoride from potable water

Materials with ultrahigh adsorption competences are extensively required for effective wastewater remediation. Unfortunately, leaching and agglomeration of nanomaterial-based adsorbents is a common problem to be resolved. Carbon-based hybrid nanocomposite showing enormous capability in the field of wastewater treatment. Arsenic and fluoride in water have unpropitious effects on people’s health, and remediation of these ions through adsorption is one of the foremost challenges and high priority to the research. The present study deals with fabricating a novel composite using alumina wrapped carbon microspheres (Al-CMs) with high adsorption capacities and investigating the mechanism for removing pentavalent arsenic/arsenate (As(V)) and fluoride (F−) at the molecular level. The maximum adsorption capacities for As(V) and F− calculated from the Langmuir model are 68 and 371.1 mg/g, respectively, comparatively higher than other reported nano-adsorbents. Under optimized conditions, Al-CMs are able to remove more than 98% of F− and As(V) under wide range of pH (2–12). Further, the interaction energy of Al-CMs with F− and As(V) was examined using density functional theory (DFT). The reported work exhibits a feasible adsorbent for removing F− and As(V) from the wastewater.

A Review on Detection Techniques, Health Hazards and Human Health Risk Assessment of Arsenic Pollution in Soil and Groundwater

One of the most significant elements in the environment is arsenic (As). It is a hazardous metalloid that causes contamination of soil and water supplies as a result of numerous anthropogenic and natural sources. This pollution has detrimental impacts on human health and the ecosystem, making it crucial to monitor and control. The release of As from minerals into the soil and groundwater depends on the kind of mineral, pH, and redox conditions. As is typically found in two forms, trivalent arsenic (As3+, arsenite) and pentavalent arsenic (As5+, arsenate), both of which are inorganic and extremely deadly. When it comes to toxicity, arsenite is more dangerous than arsenate. Many people have been affected by As poisoning, due to exposure to As through water and food. Nowadays, accurate, fast measurement of As in the field remains a technical challenge; however, the X-ray fluorescence method is considered the most reliable, cost effective and capable of measuring a wide spectrum of metals. Health risk assessment is a crucial parameter to estimate the health hazards of the As molecule. The risk assessment approach proposed by the USEPA is common and widely used, amongst others. On the numerous health risk assessment models/frameworks used to foresee the carcinogenic and non-carcinogenic health impacts brought on by As-contaminated water, little information is currently accessible. This discussion also emphasizes the need for more study on the risks to human health posed by specific As species (both organic and inorganic) found in As-contaminated water.

Arsenic and heavy metals at Japanese abandoned chemical weapons site in China: distribution characterization, source identification and contamination risk assessment.

As-containing chemical weapons (CWs) and their degraded products pose a great threat to the environment and to human health. In this study, concentration and distribution characteristics, source identification, and health risk assessments were determined for As, Cr, Ni, Cu, Zn, Cd and Pb in environmental samples from Lianhuapao (LHP), a typical site of Japanese abandoned chemical weapons (JACWs) in China. The results show that the concentration levels of As, Cr and Ni in the LHP soils are abnormally high, with 69.57%, 83.33% and 91.67%, respectively, of the total sample exceeding the risk screening values for soil contamination of agricultural land. As levels in water samples were generally within safety limits, with the exception of perched water in the core contamination area. In the study area, none of the dominant plant species were enriched with As, except for the Pteris vittata L. Pentavalent arsenic was found to be the predominant arsenic species in the topsoil and water samples. Source identification using statistical approaches indicated that the concentrations of As, Pb, Cu, Cd and Zn are likely influenced by JACWs, while Cr and Ni levels may be related to the natural weathering process. The total concentrations of As, Cr and Ni showed a significant degree of contamination, but only As displayed high potential ecological risk. The calculated indexes of health risk evaluation strongly indicate an unacceptable carcinogenic risk (1E-04) to children, and higher non-carcinogenic risk, relative to that of adults. Our data indicate that the health risk from the resulting As contamination is still a cause for concern, although the JACWs were excavated decades ago from these soils.

Layered Double Hydroxide-Based Micro "Chemical Factory" with Arsenic Processing and Screening Functions on Nitinol for Gallbladder Cancer Treatment.

Gallbladder cancer is a common malignant tumor of the biliary system with a high fatality rate. Nitinol (Ni-Ti) stents, a standard treatment for prolonging patients' lives, are susceptible to reocclusion and cannot inhibit tumor recurrence because they lack antitumor and antibacterial activity. Herein, an arsenic-loaded layered double-hydroxide film is constructed on Ni-Ti, forming a micro "chemical factory." The LDH plays the role of a "processer" which absorbs highly toxic trivalent arsenic (As(III)) and processes it into lowly toxic pentavalent arsenic (As(V)). It also acts as a "quality-inspector," confining As(III) in the interlayer and releasing only As(V) (the finished product) to the outside. This control mechanism minimizes the toxicity during contact with normal tissue. The acidic microenvironment and overexpression of glutathione in tumor tissues not only accelerates the release of arsenic from the platform but also triggers the in situ transformation of arsenic from lowly toxic As(V) to highly toxic As(III), exerting a strong arsenic-mediated antineoplastic effect. Such a microenvironment-responsive "chemical factory" with arsenic processing and screening functions is expected to prevent tumor overgrowth, metastasis, and bacterial infection and provide new insights into the design of Ni-Ti drug-eluting stents for gallbladder cancer treatment.

Arsenic: A Review on a Great Health Issue Worldwide

Arsenic intoxication represents a worldwide health problem and occurs mainly through drinking water. Arsenic, a metalloid and naturally occurring element, is one of the most abundant elements in the earth’s crust, whose toxicity depends on the reduction state. The trivalent arsenicals are more toxic than the pentavalent arsenicals. In the trivalent state, inorganic and organic arsenic may react with thiol groups in proteins inhibiting their activity, whereas inorganic arsenic in the pentavalent state may replace phosphate ions in several reactions. Arsenic induces various epigenetic changes in mammalian cells, both in vivo and in vitro, often leading to the development of various types of cancers, including skin, lung, liver, urinary tract, prostate, and hematopoietic cancers. Potential mechanisms of arsenic toxicity in cancer include genotoxicity, altered DNA methylation and cell proliferation, co-carcinogenesis, tumor promotion, and oxidative stress. On the other hand, the FDA-certified drug arsenic trioxide provides solutions for various diseases, including several types of cancers. Detoxification from arsenic includes chelation therapy. Recently, investigations of the capability of some plants, such as Eucalyptus camadulensis L., Terminalia arjuna L. and Salix tetrasperma L., to remove arsenic from polluted soil and water have been studied. Moreover, nanophytoremediation is a green technology including the nanoscale materials used for absorption and degradation of organic and inorganic pollutants, such as arsenic compounds. This brief review represents an overview of arsenic uses, toxicity, epigenetics, and detoxification therapies.

PREPARATION AND CHARACTERIZATION OF MESOPOROUS CERIUM OXIDE FOR TOXIC AS(V) REMOVAL: PERFORMANCE AND MECHANISTIC STUDIE

In the present work, the adsorption of carcinogenic pentavalent arsenic (As(V)) from an aqueous solution was studied using mesoporous cerium oxide (MCO). The MCO was synthesized in the precipitation process and confirmed by FT-IR, SEM-EDX, XRD, and BET instrumental techniques. Batch adsorption showed that 95% of As(V) was removed in the optimum conditions of 0.60 g/L adsorbent dose, 10 mg/L initial concentration, time 30 min, and pH 3. Pseudo-secondorder kinetics and the Langmuir isotherm model were fitted to the experimental data. The MCO had a high surface area of 191.97 m2/g and a maximum adsorption capacity of 58.25 mg/g at pH 3. MCO could be able to remove 88% and 82% in the first and second cycles after being desorbed with 0.1 M NaOH solution. The Zeta potential and FTIR studies suggested that electrostatic attraction and ligand exchange mechanisms were responsible for As(V) adsorption.