Evaluation of the in vivo acute toxicity of poly(thioether-ester) and superparamagnetic poly(thioether-ester) nanoparticles obtained by thiol-ene miniemulsion polymerization.

Poly(thioether-ester) (PTEe) nanoparticles obtained by thiol-ene polymerization have received attention of many researchers due to several advantages, including, biocompatibility and biodegradability. The search for new nanomaterials requires toxicity studies to assess potential toxic effects of their administration. Therefore, the aim of this study was to evaluate the in vivo acute toxicity of PTEe and poly(thioether-ester)-coated magnetic nanoparticles prepared by thiol-ene polymerization in miniemulsion. These nanoparticles presented a mean size of approximately 120 nm, spherical morphology, and negative surface charge. Doses of 40 mg/kg were administered intraperitoneally to Swiss mice and nociceptive, behavioral and biochemical parameters were investigated in five different organs. None of the nanoparticles led to any alterations in the nociceptive and behavioral responses. Biochemical alterations were observed in liver, decreasing the sulfhydryl and glutathione (GSH) levels, suggesting the dependence of the GSH metabolism in the elimination of the nanoparticles. In general, both nanoparticle types did not cause disturbances in biochemical parameters analyzed in others organs. These results suggest that both nanoparticle types did not induce acute toxicity to the different organs evaluated, reinforcing the biocompatibility of PTEe nanoparticles synthetized by thiol-ene polymerization.

Wide visible-range activatable fluorescence ZnSe:Eu3+/Mn2+@ZnS quantum dots: local atomic structure order and application as a nanoprobe for bioimaging.

The development of QDs-based fluorescent bionanoprobe for cellular imaging fundamentally relies upon the precise knowledge of particle-cell interaction, optical properties of QDs inside and outside of the cell, movement of a particle in and out of the cell, and the fate of particle. We reported engineering and physicochemical characterization of water-dispersible Eu3+/Mn2+ co-doped ZnSe@ZnS core/shell QDs and studied their potential as a bionanoprobe for biomedical applications, evaluating their biocompatibility, fluorescence behaviour by CytoViva dual mode fluorescence imaging, time-dependent uptake, endocytosis and exocytosis in RAW 264.7 macrophages. The oxidation state and local atomic structure of the Eu dopant studied by X-ray absorption fine structure (XAFS) analysis manifested that the Eu3+ ions occupied sites in both ZnSe and ZnS lattices for the core/shell QDs. A novel approach was developed to relieve the excitation constraint of wide bandgap ZnSe by co-incorporation of Eu3+/Mn2+ codopants, enabling the QDs to be excited at a wide UV-visible range. The QDs displayed tunable emission colors by a gradual increase in Eu3+ concentration at a fixed amount of Mn2+, systematically enhancing the Mn2+ emission intensity via energy transfer from the Eu3+ to Mn2+ ion. The ZnSe:Eu3+/Mn2+@ZnS QDs presented high cell viability above 85% and induced no cell activation. The detailed analyses of QDs-treated cells by dual mode fluorescence CytoViva microscopy confirmed the systematic color-tunable fluorescence and its intensity enhances as a function of incubation time. The QDs were internalized by the cells predominantly via macropinocytosis and other lipid raft-mediated endocytic pathways, retaining an efficient amount for 24 h. The unique color tunability and consistent high intensity emission make these QDs useful for developing a multiplex fluorescent bionanoprobe, activatable in wide-visible region.

Mangrove Fishes Rely on Emersion Behavior and Physiological Tolerance to Persist in Sulfidic Environments.

Hydrogen sulfide (H 2 S) is a potent respiratory toxin that makes sulfidic environments tolerable to only a few organisms. We report the presence of fishes ( Kryptolebias marmoratus , Poecilia orri , Gambusia sp., and Dormitator maculatus ) in Belizean mangrove pools with extremely high H 2 S concentrations (up to 1,166 µM) that would be lethal for most fishes. Thus, we asked whether the three most prevalent species ( Kryptolebias , Poecilia , and Gambusia ) persist in sulfidic pools because they are exceptionally H 2 S tolerant and/or because they can leave water (emerse) and completely avoid H 2 S. We show that both physiological tolerance and emersion behavior are important. Kryptolebias demonstrated high H 2 S tolerance, as they lost equilibrium significantly later than Poecilia and Gambusia during H 2 S exposure ( 1,188±21 µM H 2 S). However, the fact that all species lost equilibrium at an ecologically relevant [H 2 S] suggests that physiological tolerance may suffice at moderate H 2 S concentrations but that another strategy is required to endure higher concentrations. In support of the avoidance behavior hypothesis, H 2 S elicited an emersion response in all species. Kryptolebias was most sensitive to H 2 S and emersed at H 2 S concentrations 52% and 34% lower than Poecilia and Gambusia , respectively. Moreover, H 2 S exposure caused Kryptolebias to emerse more frequently and spend more time out of water compared to control conditions. We suggest that physiological H 2 S tolerance and emersion behavior are complementary strategies. The superior H 2 S tolerance and amphibious capability of Kryptolebias may explain why this species was more prevalent in H 2 S-rich environments than other local fishes.

Assessment of biofilm changes and concentration-depth profiles during arsenopyrite oxidation by Acidithiobacillus thiooxidans.

Biofilm formation and evolution are key factors to consider to better understand the kinetics of arsenopyrite biooxidation. Chemical and surface analyses were carried out using Raman spectroscopy, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), glow discharge spectroscopy (GDS), and protein analysis (i.e., quantification) in order to evaluate the formation of intermediate secondary compounds and any significant changes arising in the biofilm structure of Acidithiobacillus thiooxidans during a 120-h period of biooxidation. Results show that the biofilm first evolves from a low cell density structure (1 to 12 h) into a formation of microcolonies (24 to 120 h) and then finally becomes enclosed by a secondary compound matrix that includes pyrite (FeS2)-like, S n2-/S0, and As2S3 compounds, as shown by Raman and SEM-EDS. GDS analyses (concentration-depth profiles, i.e., 12 h) indicate significant differences for depth speciation between abiotic control and biooxidized surfaces, thus providing a quantitative assessment of surface-bulk changes across samples (i.e. reactivity and /or structure-activity relationship). Respectively, quantitative protein analyses and CLSM analyses suggest variations in the type of extracellular protein expressed and changes in the biofilm structure from hydrophilic (i.e., exopolysaccharides) to hydrophobic (i.e., lipids) due to arsenopyrite and cell interactions during the 120-h period of biooxidation. We suggest feasible environmental and industrial implications for arsenopyrite biooxidation based on the findings of this study.

Short term inhalation toxicity of a liquid aerosol of glutaraldehyde-coated CdS/Cd(OH)2 core shell quantum dots in rats.

Quantum dots exhibit extraordinary optical and mechanical properties, and the number of their applications is increasing. In order to investigate a possible effect of coating on the inhalation toxicity of previously tested non-coated CdS/Cd(OH)2 quantum dots and translocation of these very small particles from the lungs, rats were exposed to coated quantum dots or CdCl2 aerosol (since Cd(2+) was present as impurity), 6h/d for 5 consecutive days. Cd content was determined in organs and excreta after the end of exposure and three weeks thereafter. Toxicity was determined by examination of broncho-alveolar lavage fluid and microscopic evaluation of the entire respiratory tract. There was no evidence for translocation of particles from the respiratory tract. Evidence of a minimal inflammatory process was observed by examination of broncho-alveolar lavage fluid. Microscopically, minimal to mild epithelial alteration was seen in the larynx. The effects observed with coated quantum dots, non-coated quantum dots and CdCl2 were comparable, indicating that quantum dots elicited no significant effects beyond the toxicity of the Cd(2+) ion itself. Compared to other compounds with larger particle size tested at similarly low concentrations, quantum dots caused much less pronounced toxicological effects. Therefore, the present data show that small particle sizes with corresponding high surfaces are not the only factor triggering the toxic response or translocation.

Lime sulfur toxicity to broad mite, to its host plants and to natural enemies.

BACKGROUND: An acaricidal effect of lime sulfur has not been demonstrated for Polyphagotarsonemus latus. However, lime sulfur can cause toxicity to natural enemies and to host plants. In this study, the toxicity of different concentrations of lime sulfur to P. latus, to the predatory mite Amblyseius herbicolus and to the predatory insect Chrysoperla externa was evaluated. Additionally, the phytotoxicity of lime sulfur to two P. latus hosts, chili pepper and physic nut plants, was determined. RESULTS: Lime sulfur at a concentration of 9.5 mL L(-1) restrained P. latus population growth. However, this concentration was deleterious to natural enemies. The predatory mite A. herbicolus showed a negative value of instantaneous growth rate, and only 50% of the tested larvae of C. externa reached adulthood when exposed to 10 mL L(-1) . Physic nut had severe injury symptoms when sprayed with all tested lime sulfur concentrations. For chili pepper plants, no phytoxicity was observed at any tested concentration. CONCLUSION: Lime sulfur might be used for P. latus control on chili pepper but not on physic nut owing to phytotoxicity. Care should be taken when using lime sulfur in view of negative effects on natural enemies. Selective lime sulfur concentration integrated with other management tactics may provide an effective and sustainable P. latus control on chili pepper.

Oxidative stress induced by arsenopyrite and the role of desferrioxamine-B as radical scavenger.

Arsenopyrite (FeAsS) is one of the earth's primary mineral sources of As, yet its effects on cell damage remain largely unknown. This paper addresses the question whether FeAsS induces lipid peroxidation (LP), a major indicator of oxidative stress. Screening and monitoring of LP was conducted using Thiobarbituric Acid Reactive Substances (TBARSs) assay. The lipid source was supernatant of rat brain homogenates. The formation of TBARS by FeAsS was rapid and took place just after 10 min. Maximum TBARS levels (ca. 14 nmol TBARS per mg of protein) were observed after 1h and remained constant thereafter. Suspension fraction separations showed that dissolved and structural components contributed to LP. The formation of TBARS by soluble As, As(III) or As(V), compared to basal levels. The initiation of LP by FeAsS was consistent with a mechanism initiated by the Fe(3+)/O(2)(-) redox system, and differed initiated by Fe(2+)/O(2). The effectiveness of FeAsS and FeSO(4) as inducer compared, and surpassed that of AAPH. On the other hand, the initiation of LP by FeAsS is consistent with a mechanism initiated by perferryl ion and Fe(3+)/O(2)(-), and differs from the mechanism characteristic of FeSO(4) initiated by the Fe(2+)/O(2) redox system. Proposedly, FeAsS surfaces contain a mixture of Fe(3+) and Fe(2+) that, along with O(2) and O(2)(-), participate in multiple mechanisms of electron transfer. EPR determinations show decreases in DMPO-OH adduct signal in FeAsS suspensions after adding desferrioxamine-B (DFO-B), consistent with the idea that DFO-B serves as a radical scavenger.

Synthesis, characterization and toxicological evaluation of maltodextrin capped cadmium sulfide nanoparticles in human cell lines and chicken embryos.

BACKGROUND: Semiconductor Quantum dots (QDs) have become quite popular thanks to their properties and wide use in biological and biomedical studies. However, these same properties entail new challenges in understanding, predicting, and managing potential adverse health effects following exposure. Cadmium and selenium, which are the major components of the majority of quantum dots, are known to be acutely and chronically toxic to cells and organisms. Protecting the core of nanoparticles can, to some degree, control the toxicity related to cadmium and selenium leakage. RESULTS: This study successfully synthesized and characterized maltodextrin coated cadmium sulfide semiconductor nanoparticles. The results show that CdS-MD nanoparticles are cytotoxic and embryotoxic. CdS-MD nanoparticles in low concentrations (4.92 and 6.56 nM) lightly increased the number of HepG2 cell. A reduction in MDA-MB-231 cells was observed with concentrations higher than 4.92 nM in a dose response manner, while Caco-2 cells showed an important increase starting at 1.64 nM. CdS-MD nanoparticles induced cell death by apoptosis and necrosis in MDA-MD-231 cells starting at 8.20 nM concentrations in a dose response manner. The exposure of these cells to 11.48-14.76 nM of CdS-MD nanoparticles induced ROS production. The analysis of cell proliferation in MDA-MB-231 showed different effects. Low concentrations (1.64 nM) increased cell proliferation (6%) at 7 days (p < 0.05). However, higher concentrations (>4.92 nM) increased cell proliferation in a dose response manner (15-30%) at 7 days. Exposures of chicken embryos to CdS-MD nanoparticles resulted in a dose-dependent increase in anomalies that, starting at 9.84 nM, centered on the heart, central nervous system, placodes, neural tube and somites. No toxic alterations were observed with concentrations of < 3.28 nM, neither in cells nor chicken embryos. CONCLUSIONS: Our results indicate that CdS-MD nanoparticles induce cell death and alter cell proliferation in human cell lines at concentrations higher than 4.92 nM. We also demonstrated that they are embryotoxic. However, no toxic effects were observed with doses lower than 3.28 nM in neither cells nor chicken embryos. The CdS-MD nanoparticles used in this study can be potentially used in bio-imaging applications. However, further studies using mammalian species are required in order to discard more toxic effects.

Arsenic for the fool: an exponential connection.

Anthropogenic arsenic is insidiously building up together with natural arsenic to a level unprecedented in the history of mankind. Arsenopyrite (FeAsS) is the principal ore of arsenic and gold in hard rock mines; it is formed by a coupled substitution of sulphur by arsenic in the structure of pyrite (FeS(2)) - nicknamed "fool's gold". Other important sources of anthropogenic arsenic are fossil fuels such as coal and oil. Here I report on the first indication that the environmental concentration of total arsenic in topsoils - in the 7-18ppm range - is exponentially related to the prevalence and mortality of Alzheimer's disease and other dementias in European countries. This evidence defies the imputed absence of verified cases of human morbidity or mortality resulting from exposure to low-level arsenic in topsoils.

Physiological responses to sulfide toxicity by the air-breathing catfish, Hoplosternum littorale (Siluriformes, Callichthyidae).

Hemolytic anemia accompanied by changes in the immunology system is one of the sulfide intoxication harmful effects on Hoplosternum littorale. Hematological parameters are considered as effective indicators of stress caused by this hydrogen sulfide. During sulfide exposure, H. littorale neither alters the methemoglobin concentration nor forms sulfhemoglobin in the presence of high levels of dissolved sulfide in the water. Cytochrome c oxidase shows little activity in the gills and blood of H. littorale when exposed to sulfide. Alternative metabolic routes are suggested through which the accumulation of pyruvate leads to the formation of an end product other than lactate.

Tannery wastewater characterization and toxicity effects on Daphnia spp.

Tannery wastewater contains large quantities of organic and inorganic compounds, including toxic substances such as sulfides and chromium salts. The evaluation of wastewater quality in Chile nowadays is based on chemical specific measurements and toxicity tests. The goal of this research was to characterize tannery wastewater and to relate its physical/chemical parameters with its acute toxicity effect on Daphnia pulex. To distinguish the most important toxic compounds, physical/chemical techniques were applied to a grab sample of a final effluent based on the Phase I toxicity identification evaluation (TIE) procedure. In addition, the toxicity of a beamhouse effluent after an activated sludge reactor treatment was investigated on Daphnia magna (introduced species) and D. pulex (native species). Effluent from different tannery processes (soaking, beamhouse, tanning and final) demonstrated high values of chemical organic demand (COD; 2840-27,600 mg L(-1)), chloride (1813-16,500 mg L(-1)), sulfate (230-35,200 mg L(-1)), and total solids (8600-87,100 mg L(-1)). All effluents showed extremely toxic effects on D. pulex, with 24-h mean lethal values (LC(50)) ranging from 0.36% to 3.61%. The Phase I TIE profile showed that toxicity was significantly reduced by air stripping, filtration, and a cationic exchange resin, with toxicity reductions ranging between 46% and 76%. The aerobically treated beamhouse effluent showed significantly less toxicity for both species (43%-74%). The chemical parameters demonstrated that the remaining toxicity of the treated beamhouse effluent was associated with its ammonia (120 mg N-NH(3) L(-1)) and chloride (11,300 mg Cl(-) L(-1)) contents.

Blood parameters and metabolites in the teleost fish Colossoma macropomum exposed to sulfide or hypoxia.

Juvenile tambaqui, Colossoma macropomum, were exposed to sulfide and hypoxia for 12, 24, 48 and 96 h. Hemoglobin concentrations, red blood cell counts, and mean cell hemoglobin, were higher at 12 h in fish exposed to hypoxia. However, control fish and those exposed to sulfide and hypoxia had lower red blood cell count, hemoglobin concentration and hematocrit at 96 h. Methemoglobin was higher than in the controls, probably due to the hypoxemia induced by these stressors. Sulfhemoglobin was not detected in significant amounts in the blood of fish exposed to sulfide (in vivo), yet hemoglobin converted into sulfhemoglobin at 1-15 mM sulfide in vitro. Anaerobic metabolism seemed to be an important mechanism for adapting to sulfide exposure and blood pH returned to control values after 24 h of sulfide, preventing acidosis. The high sulfide tolerance in tambaqui is associated with its high tolerance to hypoxia.

Metal sulfides in oxygenated aquatic systems: implications for the biotic ligand model.

The Biotic Ligand Model (BLM) attempts to predict metal toxicity to aquatic organisms on the basis of metal speciation and effects at the cell surface. Current versions of the BLM for silver and copper consider metal binding by inorganic ligands, dissolved organic matter (DOM) and also competition at the cell surface from calcium and protons (pH). Recent studies reported in the geochemical and ecotoxicological literature have indicated the importance of sulfide as a ligand, even in fully oxygenated aquatic systems. Speciation calculations for oxygenated waters do not currently include reduced sulfur as a ligand and as a consequence, no version of the BLM model has been published including reduced sulfur. This reflects the limitations on our knowledge regarding reduced sulfur in aquatic systems. In this paper we highlight the need to include reduced sulfur in the Biotic Ligand Model, with the interaction between silver and inorganic metal sulfides as a specific example. The geochemical importance of metal sulfides as ligands for silver and the effect of 'dissolved' metal sulfide and other ligands on metal toxicity and accumulation are described and reviewed. Recommendations are made for future work needed to incorporate sulfide ligands into the BLM's modeling framework.