Toxicity assessment of 16 inorganic environmental pollutants by six bioassays

Cytotoxicity and Oxidative Stress Induced by Technology-Critical Elements versus Traditional Metal Contaminants: An In Vitro Bioassay Study

Technology-critical elements (TCEs), essential in emerging technologies, are increasingly finding their way into our environment, raising concerns about their sparsely studied behavior and toxicity. To contribute insights into the toxicological aspects, we employed in vitro bioassays to investigate the possible cytotoxic effects in four representative cell lines (AR-EcoScreen GR-KO-M1, DR-EcoScreen, MCF7AREc32, VM7Luc4E2) and the potential to induce oxidative stress via the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway for a number of these elements. Nine TCEs, three rare-earth elements (REEs: Gd, Nd, Yb) and six less-studied TCEs (LSTCEs: Ga, Ge, In, Ta, Te, Tl), were selected for this study, along with three well-studied traditional metal contaminants (TMCs: As, Cd, Pb) for comparison. Among the 12 studied elements, nine showed signs of inducing cytotoxicity: As, Cd, Ga, Nd, and Te in three out of the four studied cell lines and Gd, Ta, Tl, and Yb in one to two cell lines. Tellurium repeatedly exhibited the highest potency. The TCEs Ga and In, similar to As and Cd, also demonstrated the potential to induce oxidative stress. The results of this study suggest that some TCEs may potentially cause adverse health effects similar to As and Cd, thus prompting further investigations.

The Involvement of Lactic Acid Bacteria and Their Exopolysaccharides in the Biosorption and Detoxication of Heavy Metals in the Gut

Heavy metal pollution has become one of the most important global environmental issues. The human health risk posed by heavy metals encountered through the food chain and occupational and environmental exposure is increasing, resulting in a series of serious diseases. Ingested heavy metals might disturb the function of the gut barrier and cause toxicity to organs or tissues in other sites of the body. Probiotics, including some lactic acid bacteria (LAB), can be used as an alternative strategy to detoxify heavy metals in the host body due to their safety and effectiveness. Exopolysaccharides (EPS) produced by LAB possess varied chemical structures and functional properties and take part in the adsorption of heavy metals via keeping the producing cells vigorous. The main objective of this paper was to summarize the roles of LAB and their EPS in the adsorption and detoxification of heavy metals in the gut. Accumulated evidence has demonstrated that microbial EPS play a pivotal role in heavy metal biosorption. Specifically, EPS-producing LAB have been reported to show superior absorption, tolerance, and efficient abatement of the toxicity of heavy metals in vitro and/or in vivo to non-EPS-producing species. The mechanisms underlying EPS-metal binding are mainly related to the negatively charged acidic groups and unique steric structure on the surface of EPS. However, whether the enriched heavy metals on the bacterial cell surface increase toxicity to local mammal cells or tissues in the intestine and whether they are released during excretion remain to be elucidated.

Fe-Zn alloy, a new biodegradable material capable of reducing ROS and inhibiting oxidative stress

Fe-based biodegradable materials have attracted significant attention due to their exceptional mechanical properties and favorable biocompatibility. Currently, research on Fe-based materials mainly focuses on regulating the degradation rate. However, excessive release of Fe ions during material degradation will induce the generation of reactive oxygen species (ROS), leading to oxidative stress and ferroptosis. Therefore, the control of ROS release and the improvement of biocompatibility for Fe-based materials are very important. In this study, new Fe-Zn alloys were prepared by electrodeposition with the intention of using Zn as an antioxidant to reduce oxidative damage during alloy degradation. Initially, the impact of three potential degradation ions (Fe2+, Fe3+, Zn2+) from the Fe-Zn alloy on human endothelial cell (EC) activity and migration ability was investigated. Subsequently, cell adhesion, cell activity, ROS production and DNA damage were assessed at various locations surrounding the alloy. Finally, the influence of different concentrations of Zn2+ in the medium on cell viability and ROS production was evaluated. High levels of ROS exhibited evident toxic effects on ECs and promoted DNA damage. As an antioxidant, Zn2+ effectively reduced ROS production around Fe and improved the cell viability on its surface at a concentration of 0.04 mmol/l. These findings demonstrate that Fe-Zn alloy can attenuate the ROS generated from Fe degradation thereby enhancing cytocompatibility.

A community-based approach to analyzing the ecotoxicity of nitrofurazone using periphytic protozoa

The ecotoxicity of nitrofurazone was analyzed based on a community-based approach using periphytic protozoa. Median lethal concentrations (LC₅₀) within an exposure time of 30 min were determined by an acute toxicity test at 0, 1.5, 3, 6 and 12 mg ml^-1 nitrofurazone. Toxicity curve tests demonstrated a decreasing trend with increasing exposure time and was well fitted to the toxicity equation LC₅₀ = 32.85e^-0.8143t (t = exposure time; R² = 0.91; P < 0.05). Median inhibition concentrations (IC₅₀) for periphytic protozoan growth rates were obtained by chronic tests at 0, 1, 2, 4 and 8 mg ml^-1 nitrofurazone within 10 days exposure and were well fitted to the equation r_% = 0.3686e^-0.35Cnit (C_nit is the concentration of nitrofurazone; R² = 0.92 and P < 0.05). These findings suggest that the LC₅₀ and IC₅₀ values of nitrofurazone can be predicted for any exposure time using periphytic protozoan communities as a bioassay model.

Insights into the ecotoxicity of nitrofurazone in marine ecosystems based on body-size spectra of periphytic ciliates

In ecotoxicological studies, some biological responses known as biomarkers can be used as powerful tools to evaluate the ecotoxicity. In this study, we investigated the disparity of responses shown by body-size spectra of periphytic ciliate communities when used as biomarkers to detect the toxicity of the broad-spectrum veternary antibiotic nitrofurazone. Briefly, in chronic exposure experiments ciliate communities were exposed to different concentrations (0, 1, 2, 4 and 8 mg ml^-1) of nitrofurazone. Relative Abundance of ciliates in all body-size categories decreased significantly, whereas their frequency of occurrence and probability densities showed hormetic-like responses in a dose dependent manner. Additionally, body-size distinctness indices were influenced by toxic stress and significantly departed from an expectation at higher nitrofurazone concentrations. Taken together, our results demonstrated that body-size spectra and body-size distinctness offered clear evidence of nitrofurazone toxicity in periphytic ciliates. Body-size spectra can therefore be used as a pivotal biomarker to determine the ecotoxicity of nitrofurazone in aquatic environments.

Opposite Effects Induced by Cholinium-Based Ionic Liquid Electrolytes in the Formation of Aqueous Biphasic Systems Comprising Polyethylene Glycol and Sodium Polyacrylate

Cholinium-based ionic liquids ([Ch]-based ILs) were investigated as electrolytes in the formation of aqueous biphasic systems (ABS) composed of polyethylene glycol (PEG) and sodium polyacrylate (NaPA) polymers. Both enhancement and decrease in the liquid-liquid demixing ability induced by electrolytes in PEG-NaPA aqueous biphasic systems were observed. It is shown that the ILs that most extensively partition to the PEG-rich phase tend to act as inorganic salts enhancing the two-phase formation ability, while those that display a more significant partition to the NaPA-rich phase decrease the ABS formation capacity. The gathered results allowed us to confirm the tailoring ability of ILs and to identify, for the first time, opposite effects induced by electrolytes on the PEG-NaPA ABS formation ability. The distribution of the electrolyte ions between the coexisting phases and the polyelectrolyte ion compartmentalization are key factors behind the formation of PEG-NaPA-based ABS.

Cytotoxicity of Gallium-Indium Liquid Metal in an Aqueous Environment

Eutectic gallium-indium alloy (EGaIn) liquid metal is highly conductive, moldable, and extremely deformable and has attracted significant attention for many applications, ranging from stretchable electronics to drug delivery. Even though EGaIn liquid metal is generally known to have low toxicity, the toxicity of the metal, rather than a salt form of Ga or In, has not been systematically studied yet. In this paper, we investigate the time-dependent concentration of the ions released from EGaIn liquid metal in an aqueous environment and their cytotoxicity to human cells. It is observed that only the Ga ion is dominantly released from EGaIn when no external agitation is applied, whereas the concentration of the In ion drastically increases with sonication. The cytotoxicity study reveals that all human cells tested are viable in the growth media with naturally released EGaIn ions, but the cytotoxicity becomes significant with sonication-induced EGaIn releasates. On the basis of the comparative study with other representative toxic elements, that is, Hg and Cd, it could be concluded that EGaIn is reasonably safe to use in an aqueous environment; however, it should be cautiously handled when any mechanical agitation is applied.

Cytotoxicity of alloying elements and experimental titanium alloys by WST-1 and agar overlay tests

OBJECTIVE

This study was performed to evaluate the biocompatibility of nine types of pure metals using 36 experimental prosthetic titanium-based alloys containing 5, 10, 15, and 20wt% of each substituted metal.

METHODS

The cell viabilities for pure metals on Ti alloys that contain these elements were compared with that of commercially pure (CP) Ti using the WST-1 test and agar overlay test.

RESULTS

The ranking of pure metal cytotoxicity from most potent to least potent was: Co>Cu>In>Ag>Cr>Sn>Au>Pd>Pt>CP Ti. The cell viability ratios for pure Co, Cu, In, and Ag were 13.9±4.6%, 21.7±10.4%, 24.1±5.7%, and 24.8±6.0%, respectively, which were significantly lower than that for the control group (p<0.05). Pure Pd and Pt demonstrated good biocompatibility with cell viabilities of 93.8±9.6% and 97.2±7.1%, respectively. The Ti-5Pd alloy exhibited the highest cell viability (128.4±21.4%), which was greater than that of CP Ti. By alloying pure Co or Cu with Ti, the cell viabilities for the Ti-xCo and Ti-xCu alloys increased significantly up to 10wt% of the alloying element followed by a gradual decrease with a further increase in the concentration of the alloying element. Based on the agar overlay test, pure Ag, Co, Cr, Cu, and In were ranked as 'moderately cytotoxic', whereas all Ti alloys were ranked as 'noncytotoxic'.

SIGNIFICANCE

The cytotoxicity of pure Ag, Co, Cr, Cu, and In suggests a need for attention in alloy design. The cytotoxicity of alloying elements became more biocompatible when they were alloyed with titanium. However, the cytotoxicity of titanium alloys was observed when the concentration of the alloying element exceeded its respective allowable limit. The results obtained in this study can serve as a guide for the development of new Ti-based alloy systems.

Cytocompatibility of pure metals and experimental binary titanium alloys for implant materials

OBJECTIVE

This study was performed to evaluate the biocompatibility of nine types of pure metal ingots (Ag, Al, Cr, Cu, Mn, Mo, Nb, V, Zr) and 36 experimental titanium (Ti) alloys containing 5, 10, 15, and 20 wt% of each alloying element.

METHODS

The cell viabilities for each test group were compared with that of CP-Ti using the WST-1 test and agar overlay test.

RESULTS

The ranking of pure metal cytotoxicity from most potent to least potent was as follows: Cu>Al>Ag>V>Mn>Cr>Zr>Nb>Mo>CP-Ti. The mean cell viabilities for pure Cu, Al, Ag, V, and Mn were 21.6%, 25.3%, 31.7%, 31.7%, and 32.7%, respectively, which were significantly lower than that for the control group (p<0.05). The mean cell viabilities for pure Zr and Cr were 74.1% and 60.6%, respectively (p<0.05). Pure Mo and Nb demonstrated good biocompatibility with mean cell viabilities of 93.3% and 93.0%, respectively. The mean cell viabilities for all the Ti-based alloy groups were higher than 80% except for Ti-20 Nb (79.6%) and Ti-10 V (66.9%). The Ti-10 Nb alloy exhibited the highest cell viability (124.8%), which was higher than that of CP-Ti. Based on agar overlay test, pure Ag, Cr, Cu, Mn, and V were ranked as 'moderately cytotoxic', whereas the rest of the tested pure metals and all Ti alloys, except Ti-10 V (mild cytotoxicity), were ranked as 'noncytotoxic'.

SIGNIFICANCE

The results obtained in this study can serve as a guide for the development of new Ti-based alloy implant systems.

RAPD-PCR analysis for molecular characterization and genotoxic studies of a new marine fish cell line derived from Dicentrarchus labrax

Continuous cell lines could provide an important tool for studying epidemiology, toxicology, cellular physiology and the host-pathogen interactions. Random amplified polymorphic deoxyribonucleic acid analysis by PCR (RAPD-PCR) was used for the molecular characterization of Dicentrarchus labrax embryonic cells (DLEC) as a possible tool to detect DNA alterations in environmental genotoxic studies. We studied the DNA pattern of the DLEC fish cell line, a fibroblast-like cell line derived from European sea bass. From a total of 15 primers only six showed good discriminatory power for the amplification process on DNA samples collected from cells by three different methods (organic extraction, salting-out method and chelating agent extraction). The results obtained show that the cell line chosen for this study could be used as a possible tool for the detection of potential genotoxicity of numerous chemical compounds.

Development of q-PCR approaches to assess water quality: effects of cadmium on gene expression of the diatom Eolimna minima

This study was undertaken to develop molecular tools to assess water quality using diatoms as the biological model. Molecular approaches were designed following the development of a rapid and easy RNA extraction method suited to diatoms and the sequencing of genes involved in mitochondrial and photosystem metabolism. Secondly the impact of cadmium was evaluated at the genetic level by q-PCR on 9 genes of interest after exposure of Eolimna minima diatom populations cultured in suspension under controlled laboratory conditions. Their growth kinetics and Cd bioaccumulation were followed. Population growth rates revealed the high impact of Cd at 100 μg/L with total inhibition of growth. These results are linked to the high bioaccumulation values calculated after 14 days of exposure, 57.0±6.3 μg Cd/g dw and 734.1±70 μg Cd/g dw for exposures of 10 and 100 μg Cd/L respectively. Genetic responses revealed the impact of Cd on the mitochondrial metabolism and the chloroplast photosystem of E. minima exposed to 10 and 100 μg Cd/L with induction of cox1, 12S, d1 and psaA after 7 days of exposure for the concentration of 100 μg Cd/L and of nad5, d1 and psaA after 14 days of exposure for both conditions. This is the first reported use of q-PCR for the assessment of toxic pollution on benthic river diatoms. The results obtained presage interesting perspectives, but the techniques developed need to be optimized before the design of new water quality diagnosis tools for use on natural biofilms.

Tetrahymena in the laboratory: strain resources, methods for culture, maintenance, and storage

The ciliated protozoan Tetrahymena thermophila has been an important model system for biological research for many years. During that time, a variety of useful strains, including highly inbred stocks, a collection of diverse mutant strains, and wild cultivars from a variety of geographical locations have been identified. In addition, thanks to the efforts of many different laboratories, optimal conditions for growth, maintenance, and storage of Tetrahymena have been worked out. To facilitate the efficient use of Tetrahymena, especially by those new to the system, this chapter presents a brief description of many available Tetrahymena strains and lists possible resources for obtaining viable cultures of T. thermophila and other Tetrahymena species. Descriptions of commonly used media, methods for cell culture and maintenance, and protocols for short- and long-term storage are also presented.

Use of RAPD to detect DNA damage induced by nitrofurazone in marine ciliate, Euplotes vannus (Protozoa, Ciliophora)

The random amplified polymorphic DNA (RAPD) assay was evaluated as a potential tool to detect the ecotoxicity induced by nitrofurazone in marine ciliate, Euplotes vannus. The data revealed a reduction in viability of the test ciliates with increasing nitrofurazone concentration in the range of 0-24 mgl(-1) and time of exposure from 24 to 96 h. The nitrofurazone treated ciliates were subjected to DNA damage analysis by RAPD assay. Among the 33 test RAPD primers used in this study, 11 primers with 60-70% GC content produced unique polymorphic band patterns. A total of 213 bands of 155-3317 bp in molecular size range were observed in the untreated cells. In comparison with the control ciliates, the nitrofurazone treated groups showed differences in RAPD profiles with respect to the band intensity, disappearance of bands and appearance of new bands of amplified DNA. The variation of RAPD profiles showed both the time- and concentration-dependent relationships. The data suggested significant genomic template instability, which corresponds well with the viability of the test ciliates. Thus the results demonstrated the potential of the RAPD assay for application as a powerful tool for detecting genotoxicity induced by fishy drugs in aquatic environment.

Toxicity profiles of four metals and 17 xenobiotics in the human hepatoma cell line HepG2 and the protozoa Tetrahymena pyriformis--a comparison

We performed an interspecies comparison for the human hepatoma cell line HepG2 and the eukaryotic single cell organism Tetrahymena pyriformis (T. pyriformis) for 17 xenobiotics with diverse structures and four metals. The cytotoxicity was assessed by four different cell viability assays (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide reduction (MTT), neutral red uptake (NRU), resazurin dye (AlamarBlue), 5-carboxyfluorescein diacetate acetoxymethyl ester (CFDA-AM)) for the HepG2 and by cell count and MTT for T. pyriformis. For HepG2 cells, the results revealed interassay variations depending on the compound. The highest assay conformity was found for the metal Hg(2+) and the fungicide prochloraz. The AlamarBlue assay was the most sensitive assay according to low-effect concentrations. By contrast, the NRU assay was comprised of more frequent whole concentration response relationships and was more susceptible to EC(50). For T. pyriformis the EC(50) values of the two applied assays displayed a high conformity (R(2) = 0.97). Comparing the EC(50) values obtained by the MTT assay for the two cell models, a direct correlation was absent for the xenobiotics and only present for the metals (Cd(2+), Cu(2+), and Ni(2+)). Moreover, the protozoa T. pyriformis displayed a 20 times higher sensitivity than the cell line. The highest interspecies difference of three log degrees was obtained for the polycyclic aromatic hydrocarbon fluoranthene. In addition, a correlation of the EC(50) values and octanol-water partition coefficient (log K(OW)) of the xenobiotics was performed. No correlation was found for HepG2, and a weak one for T. pyriformis. Interestingly, the interspecies difference of logarithmized EC(50) correlated positive with the log K(OW) (R(2) = 0.65). In conclusion, to obtain reliable evidence for human cytotoxicity, more than one viability/cytotoxicity assay had to be applied for cell lines. Second, the human hepatoma cell line was less affected by the organic compounds than the eukaryotic single-cell organism and was also less dependent on the log K(OW) of the xenobiotic.

Mutagenicity and genotoxicity of tannery effluents used for irrigation at Kanpur, India

The tannery effluents at Kanpur (India) have been in use for irrigation since last many years, polluting soil directly while ground water and food crops indirectly. Gas chromatography-mass spectrometric analysis of the test samples revealed the presence of organic compounds including diisooctyl phthalate, phenyl N-methylcarbamate, dibutyl phthalate, bis 2-methoxyethyl phthalate, and higher alkanes. Tannery effluent extracts were prepared using XAD-4/8 resins, dichloromethane, chloroform, and hexane and tested with Ames Salmonella test and DNA repair-defective Escherichia coli K-12 mutants. In the presence of XAD-concentrated tannery effluent, TA98 found to be the most sensitive strain in terms of mutagenic index followed by TA97a whereas in terms of mutagenic potential TA102 was most responsive. The extracts were also found genotoxic as determined in terms of survival of E. coli K-12 mutants, suggesting the presence of DNA damaging compounds in the tannery effluents. In the light of results, precautious use of tannery effluents for irrigation is suggested.

Acute toxicity of metals and reference toxicants to a freshwater ostracod, Cypris subglobosa Sowerby, 1840 and correlation to EC(50) values of other test models

The ostracod Cypris subglobosa Sowerby, 1840 static bioassay test on the basis of a 48h of 50% of immobilization (EC(50)) has been used to measure the toxicity of 36 metals and metalloids and 12 reference toxicants. Among the 36 metals and metalloids, osmium (Os) was found to be the most toxic in the test while boron (B), the least toxic. The EC(50) values of this study revealed positive linear relationship with the established test models of cladoceran (Daphnia magna), sludge worm (Tubifex tubifex), chironomid larvae (Chironomus tentans), protozoan (Tetrahymena pyriformis), fathead minnow (Pimephales promelas), bluegill sunfish (Lepomis macrochirus), and aquatic macrophyte duckweed (Lemna minor). Correlation coefficients (r(2)) for 17 physicochemical properties of metals or metal ions and EC(50)s (as pM) were examined by linear regression analysis. The electronegativity, ionization potential, melting point, solubility product of metal sulfides (pK(sp)), softness parameter and some other physicochemical characteristics were significantly correlated with EC(50)s of metals to C. subglobosa. The reproducibility of toxicity test was determined using 12 reference toxicants. The coefficient of variability of the EC(50)s ranged from 6.95% to 55.37% and variability was comparable to that noticed for D. magna and other aquatic test models. The study demonstrated the need to include crustacean ostracods in a battery of biotests to detect the presence of hazardous chemicals in soils, sewage sludges, sediments and aquatic systems.

Prediction of acute mammalian toxicity from QSARs and interspecies correlations

With the ever-growing number of xenobiotics that can potentially contaminate the environment, the determination of their mammalian toxicity is of prime importance. In this context, LD50 tests on rats and mice have been used for a long time to express the relative hazard associated with the acute toxicity of inorganic and organic chemicals. However, these laboratory tests encounter important hurdles. They are costly, time consuming and actively opposed by animal rights activists. Moreover, new legislation policies, such as REACH (Registration, Evaluation, Authorization and Restriction of Chemicals), aim at reducing the use of toxicity tests on vertebrates. Consequently, there is a need to find alternative methods for estimating the acute mammalian toxicity of chemicals. The quantitative structure-activity relationships (QSARs) and interspecies correlations appear particularly suited to reaching this goal. In this context, this paper reviews more than 150 models aiming at predicting rat and mouse LD50 values from molecular descriptors or (and) ecotoxicity data. The interest of these computational tools is discussed.

Heavy metals generate reactive oxygen species in terrestrial and aquatic ciliated protozoa

Reactive oxygen species (ROS) induction by exposure to heavy metals (Cd, Cu or Zn) in diverse free-living ciliated protozoa (Tetrahymena sp. and three strains of Colpoda steinii, isolated from freshwater and soils with different level of metal pollution) has been evaluated. Using specific fluorophores, such as 2',7'-dichlorofluorescein diacetate, hydroethidine and dihydrorhodamine 123, and a fluorescence microscope with the program MetaMorph Imaging System 4.0, we have analyzed both the average fluorescence emission and the heterogeneous distribution of fluorescence in control and treated cells. This is the first time that these fluorophores are used to detect ROS production in ciliated protozoa. All metals generate ROS, mainly superoxide and peroxides, showing a remarkable inter- and intra-specific variations. Likewise, resistance against each metal was also very diverse. Cu and specially Cd, the most toxic heavy metal for these ciliates, are the best oxidative stress inducers. However, a correlation between fluorescence emission intensity and cellular metal sensitivity for each strain cannot be established. Results are discussed and compared with similar findings previously published in other unicellular and pluricellular organisms.

Impact of water saturation level on arsenic and metal mobility in the Fe-amended soil

The impact of water saturation level (oxidizing-reducing environment) on As and metal solubility in chromium, copper, arsenic (CCA)-contaminated soil amended with Fe-containing materials was studied. The soil was mixed with 0.1 and 1 wt% of iron grit (Fe(0)) and 1, 7 and 15 wt% of oxygen scarfing granulate (OSG, a by-product of steel processing). Solubility of As and metals was evaluated by a batch leaching test and analysis of soil pore water. Soil saturation with water greatly increased As solubility in the untreated as well as in the Fe-amended soil. This was related to the reductive dissolution of Fe oxides and increased concentration of As(III) species. Fe amendments showed As reducing capacity under both oxic and anoxic conditions. The cytotoxicity of the soil pore water correlated with the concentration of As(III). The Fe-treatments as well as water saturation of soil were less significant for the solubility of Cu, Cr and Zn than for As. The batch leaching test used for waste characterization substantially underestimated As solubility that could occur under water-saturated (anaerobic) conditions. In the case of soil landfilling, other techniques than Fe-stabilization of As containing soil should be considered.

Bioenergetic investigation of the effects of La(III) and Ca(II) on the metabolic activity of Tetrahymena thermophila BF5

The heat flux of Tetrahymena thermophila BF5 during growth and the effects of La(3+) and Ca(2+) on them were investigated with microcalorimetry; simultaneously, morphological changes of T. thermophila were obtained by light microscope. La(3+) in low concentration (0-5.0 x 10(-4) mol/l) remarkably stimulated T. thermophila metabolism, but high dose of La(3+) (5.8-8.6 x 10(-4) mol/l) restrained it in a linear manner with IC(50) being 7.2 x 10(-4) mol/l. In contrast, low concentration of Ca(2+) did not manifest obvious stimulation on T. thermophila metabolism; moreover, the IC(50) of Ca(2+) was much higher than that of La(3+). Low concentration of La(3+) did not lead to changes in appearance of T. thermophila, but low dose of Ca(2+) clearly promoted the cell proliferation. In addition, the morphological changes of T. thermophila evoked by high concentrations of La(3+) and Ca(2+) were consistent with relevant microcalorimetric results. It is concluded that La and Ca influence T. thermophila via different pathways, and La represents toxic action rather than Ca analogy.

Single-walled carbon nanotube interactions with HeLa cells

This work concerns exposing cultured human epithelial-like HeLa cells to single-walled carbon nanotubes (SWNTs) dispersed in cell culture media supplemented with serum. First, the as-received CoMoCAT SWNT-containing powder was characterized using scanning electron microscopy and thermal gravimetric analyses. Characterizations of the purified dispersions, termed DM-SWNTs, involved atomic force microscopy, inductively coupled plasma - mass spectrometry, and absorption and Raman spectroscopies. Confocal microRaman spectroscopy was used to demonstrate that DM-SWNTs were taken up by HeLa cells in a time- and temperature-dependent fashion. Transmission electron microscopy revealed SWNT-like material in intracellular vacuoles. The morphologies and growth rates of HeLa cells exposed to DM-SWNTs were statistically similar to control cells over the course of 4 d. Finally, flow cytometry was used to show that the fluorescence from MitoSOXtrade mark Red, a selective indicator of superoxide in mitochondria, was statistically similar in both control cells and cells incubated in DM-SWNTs. The combined results indicate that under our sample preparation protocols and assay conditions, CoMoCAT DM-SWNT dispersions are not inherently cytotoxic to HeLa cells. We conclude with recommendations for improving the accuracy and comparability of carbon nanotube (CNT) cytotoxicity reports.

Environmental hazard screening of a metal-polluted site using pressurized liquid extraction and two in vitro bioassays

Rapid screening methods can improve the cost effectiveness, throughput, and quality of risk assessments of contaminated sites. In the present case study, the objective was to evaluate a combination of pressurized liquid extraction and 2 in vitro bioassays for the hazard assessment of surface soil sampled from 46 points across a pyrotechnical industrial site. Pressurized liquid extraction was used to rapidly produce soil-water extracts compatible with 2 high-capacity bioassays. Hazard assessment using combined toxicological and chemical screening revealed zones with relatively high potential risks of metal pollution. Multivariate data analysis provided indications that significant inhibition in the bioassays was correlated with levels of metals in the extracts, suggesting an elevated toxic potential from certain metals. Low pH and high concentrations of dissolved organic carbon were associated with increased cytotoxicity of extracts, indicating that these factors influence metal bioavailability. The cytotoxicity observed was more strongly correlated to metal concentrations in the extracts than in the soil, suggesting that measurements of total metal concentrations in soils do not provide good indications of the soil's potential toxicity.

Techniques for the stabilization and assessment of treated copper-, chromium-, and arsenic-contaminated soil

Remediation mainly based on excavation and burial of the contaminated soil is impractical with regard to the large numbers of sites identified as being in need of remediation. Therefore, alternative methods are needed for brownfield remediation. This study was conducted to assess a chemical stabilization procedure of CCA-contaminated soil using iron (Fe)-containing blaster sand (BS) or oxygen-scarfing granulate (OSG). The stabilization technique was assessed with regard to the feasibility of mixing ameliorants at an industrial scale and the efficiency of the stabilization under different redox conditions. The stability was investigated under natural conditions in 1-m3 lysimeters in a field experiment, and the effect of redox conditions was assessed in a laboratory experiment (10 L). The treatments with high additions of ameliorant (8% and 17%) were more successful in both the laboratory and field experiments, even though there was enough Fe on a stochiometric basis even at the lowest addition rates (0.1% and 1%). The particle size of the Fe and the mixing influenced the stabilization efficiency. The development of anaerobic conditions, simulated by water saturation, increases the fraction of arsenic (AsIII) and, consequently, As mobility. The use of high concentrations of OSG under aerobic conditions increased the concentrations of nickel (Ni) and copper (Cu) in the pore water. However, under anaerobic conditions, it decreased the As leaching compared with the untreated soil, and Ni and Cu leaching was not critical. The final destination of the treated soil should govern the amendment choice, that is, an OSG concentration of approximately 10% may be suitable if the soil is to be landfilled under anaerobic conditions. Alternatively, the soil mixed with 1% BS could be kept under aerobic conditions in a landfill cover or in situ at a brownfield site. In addition, the treatment with BS appeared to produce better effects in the long term than treatment with OSG.

Improving soil investigations at brownfield sites using a flexible work strategy and screening methods inspired by the US Environmental Protection Agency's triad approach

Investigations of polluted brownfield sites and sample analyses are expensive, and the resulting data are often of poor quality. Efforts are needed, therefore, to improve the methods used in investigations of brownfield sites to both reduce costs and improve the quality of the results. One approach that could be useful for both of these purposes is the triad strategy, developed by the US Environmental Protection Agency, in which managing uncertainty is a central feature. In the investigations reported here, a field study was conducted to identify possible ways in which uncertainties could be managed in practice. One example considered involves optimizing the uncertainty by adjusting the sizes of samples and the efforts expended in analytical work according to the specific aims of the project. In addition, the potential utility of several toxicity assessment methods for screening sites was evaluated. As well as presenting the results of these assessments, in this contribution we discuss ways in which a flexible work strategy and screening methods inspired of the triad philosophy could be incorporated into the Swedish approach to remediate brownfield sites. A tiered approach taking advantage of field and screening methods is proposed to assess brownfield sites focusing on the response and acceptable uncertainty that are required for the task.

Biocompatibility of dental casting alloys

Most cast dental restorations are made from alloys or commercially pure titanium (cpTi). Many orthodontic appliances are also fabricated from metallic materials. It has been documented in vitro and in vivo that metallic dental devices release metal ions, mainly due to corrosion. Those metallic components may be locally and systemically distributed and could play a role in the etiology of oral and systemic pathological conditions. The quality and quantity of the released cations depend upon the type of alloy and various corrosion parameters. No general correlation has been observed between alloy nobility and corrosion. However, it has been documented that some Ni-based alloys, such as beryllium-containing Ni alloys, exhibit increased corrosion, specifically at low pH. Further, microparticles are abraded from metallic restorations due to wear. In sufficient quantities, released metal ions-particularly Cu, Ni, Be, and abraded microparticles-can also induce inflammation of the adjacent periodontal tissues and the oral mucosa. While there is also some in vitro evidence that the immune response can be altered by various metal ions, the role of these ions in oral inflammatory diseases such as gingivitis and periodontitis is unknown. Allergic reactions due to metallic dental restorations have been documented. Ni has especially been identified as being highly allergenic. Interestingly, from 34% to 65.5% of the patients who are allergic to Ni are also allergic to Pd. Further, Pd allergy always occurrs with Ni sensitivity. In contrast, no study has been published which supports the hypothesis that dental metallic materials are mutagenic/genotoxic or might be a carcinogenic hazard to man. Taken together, very contradictory data have been documented regarding the local and systemic effects of dental casting alloys and metallic ions released from them. Therefore, it is of critical importance to elucidate the release of cations from metallic dental restorations in the oral environment and to determine the biological interactions of released metal components with oral and systemic tissues.

Flow cytometry assessment of cytotoxicity and reactive oxygen species generation by single and binary mixtures of cadmium, zinc and copper on populations of the ciliated protozoan Tetrahymena thermophila

In the present study, we have assessed by flow cytometry, the cytotoxicity of the heavy metals Cd, Zn and Cu on populations of the ciliated protozoan Tetrahymena thermophila. The obtained LC(50) for these metals was estimated as 0.195mgCdl(-1), 3.58mgZnl(-1) and 0.47mgCul(-1), respectively. As a result, the toxicity rank for this eukaryotic microorganism is Cd>Cu>>Zn. Using the same methodology and the Concentration Addition approach, the toxicity of binary mixtures of these metals was evaluated in order to detect the type of interaction between these metals. Results indicated that antagonism is the predominant interaction but it can change to additivity or even to synergism at high metal concentrations. Besides, the concentration ratio between metals plays also a crucial role in determining the type of metallic interaction, at least in Tetrahymena. Cytotoxicity data from single and bimetallic mixtures have been compared with those from selected microalgae, other species of ciliates, fish and mammalian cell lines and metazoan. By other hand, we have detected the mitochondrial generation of peroxides induced by both single and binary treatments with Cd, Zn and Cu on populations of Tetrahymena, using the specific fluorophore dyhidrorhodamine. The nature and concentrations of metal as well as the metallic ratio were important factors in reactive oxygen species production. All results found in T. thermophila are compared with previous reports in other organisms and, some explanations and hypothesis to support results are given, including the involvement of metallothioneins as antioxidants and their role in the binding of metal cations.

Ion release from gold/platinum dental alloy: could release of other elements be accountable in the contact allergy attributed to the gold?

OBJECTIVES

The release of metal ions (Al, Ag, Au, Ca, Cd, Co, Cr, Cu, Mg, Mo, Ni, Pd, Pt, Ti, and Zn) from the commercial gold/platinum (Au/Pt) dental alloy of declared composition was studied.

METHODS

Au/Pt was soaked in pH 6.0 phosphate buffer, 3.5 pH phosphate buffer and pH 3.5 mixture of lactic, formic and acetic acid, and incubated at 37 degrees C for 1, 2, 3, 4, 5, 6, 7, 14, 21, and 30 days. Six samples (n = 6) of every solution were prepared for any time period. Inductively coupled plasma atomic emission spectroscopy was used for analysis of the released elements.

RESULTS

Results demonstrated release of only Cr, Cu, Fe, and Zn from the tested Au/Pt dental alloy (ANOVA, p < 0.001 for buffer, time, and interaction, respectively); however, only Cu and Zn were declared.

CONCLUSIONS

The undeclared chromium from Au/Pt dental alloy, or some other element might be responsible for the contact allergy thus far attributed to the gold.

Cytotoxicity of Phenanthrenes Extracted from Aristolochia contorta in Human Proximal Tubular Epithelial Cell Line

BACKGROUND/AIMS

Aristolochic acid nephropathy, a progressive tubulointerstitial renal disease, is predominantly a result of aristolochic acid I (AA-I) intoxication. However, other unidentified phytotoxins have indeed been postulated as the cause of this unique interstitial nephropathy. The purpose of this study was to investigate the cytotoxicity of other phenanthrene derivatives extracted from Aristolochia contorta in the human proximal tubular epithelial cell line HK-2.

METHODS

After HK-2 cells were incubated with an indicated concentration of test compounds for 24 h, cell viability was assessed by lactate dehydrogenase (LDH) leakage assay (cell membrane damage) in combination with MTT assay (metabolic capability). Cellular morphologic assessments were performed with a phase-contrast inverted microscope and transmission electron microscope.

RESULTS

In all test compounds at 5 microg/ml, AA-I, 7-methoxy-aristololactam IV and aristololactam IVa showed cytotoxic activity in HK-2 cells in both MTT assay and LDH leakage assay (p < 0.01). At high concentration (5-80 microg/ml), these three compounds caused a dose-dependent decrease in MTT reduction and a dose-dependent increase in LDH leakage compared to non-treated cells (p <0.01). In LDH leakage assay, 40 mug/ml 7-methoxy-aristololactam IV induced a 1.58-fold LDH leakage compared to AA-I at the same concentration (p < 0.01). Moreover, the IC50 of these three compounds were 16.675 microg/ml for AA-I, 4.535 microg/ml for 7-methoxy-aristololactam IV, and 30.244 microg/ml for aristololactam IVa in MTT assay. The cellular morphologic assessments suggest interactions with cell membrane and intracellular structures such as lysosome and mitochondria are likely to be involved in cell injury induced by these three compounds.

CONCLUSION

The potency of cytotoxic activity of aristololactam IVa and 7-methoxy-aristololactam IV extracted from A. contorta is similar to or even stronger than that of AA-I.

Cytotoxicity of metals common in mining effluent to rainbow trout cell lines and to the ciliated protozoan, Tetrahymena thermophila

As fish cell lines and ciliates are potential alternatives to whole animals in testing environmental samples for toxicity, two cell lines from rainbow trout, RTgill-W1 and RTL-W1, and the ciliate, Tetrahymena thermophila, were compared for their sensitivity to the toxicity of five metals that are commonly found in mining effluents: copper, cadmium, zinc, nickel, and iron. Adding copper to growth medium for either cell system failed to elicit toxicity. Therefore, metal exposures were done in simple buffers, which allowed all metals to exert toxicity, except for nickel on fish cells. Cell viability was measured successfully with alamar Blue (AB) for metabolic activity and 5'-carboxyfluoroscein diacetate acetoxymethyl ester (CFDA-AM) for membrane integrity, whereas neutral red uptake, which was quantified fluorometrically, gave confounding results with copper. Cadmium was the most toxic metal to Tetrahymena and killed the ciliate at approximately a 10-fold lower concentration than needed to kill fish cells. Fish cells were more sensitive than Tetrahymena to the cytotoxic action of zinc. Copper and iron were cytotoxic to fish cells and Tetrahymena at similar concentrations. Therefore, the relative sensitivity of fish cells and Tetrahymena to the cytotoxicity of metals depended on the metal, being similar for some but very different for others.

Comparing a ciliate and a fish cell line for their sensitivity to several classes of toxicants by the novel application of multiwell filter plates to Tetrahymena

Although ciliated protozoa such as Tetrahymena have many desirable properties as toxicological test organisms, their attributes would be better realized if multiple cultures could be simultaneously exposed to toxicants, quickly washed to terminate toxicant exposure, and conveniently evaluated for changes in cellular functions. Therefore, multiwell filter plates (MWFPs), manufactured primarily for biochemical applications, were used to expose Tetrahymena thermophila to copper, Triton X-100, and gliotoxin and compared to results of exposure in microcentrifuge tubes (MCTs). For MWFP, removal of toxicant solutions and retention of Tetrahymena in wells was done by placing plates on a manifold and applying pressure with a vacuum pump. Retained cells were resuspended in the same wells and their functions assessed with the fluorescent indicator dyes, Alamar blue to measure energy metabolism, and 5'-carboxyfluorescein diacetate acetoxymethyl ester to evaluate membrane integrity. For MCTs, exposures were terminated by centrifugation, and resuspended Tetrahymena were transferred to conventional multiwell plates for viability assessment with the same fluorescent dyes. Results were measured with a fluorescent multiwell plate reader and dose-response curves were obtained successfully with both procedures. However, MWFPs were much more convenient and rapid, potentially allowing 96 cultures to be processed at a time. Exposing Tetrahymena in MWFPs also allowed the ciliate and a rainbow trout gill cell line, RTgill-W1, to be compared for their sensitivity to toxicants under similar conditions of exposure and by common viability assays. Both cell systems showed toxic responses to Triton X-100 and copper at similar concentrations, but RTgill-W1 was more sensitive to gliotoxin.

In vitro cytotoxicity testing of three zinc metal salts using established fish cell lines

The utilisation of fish cell lines has proven to be a valuable, rapid and cost-effective tool in the ecotoxicological assessment of chemicals and environmental samples. The main objective of this study was to investigate the value of multiple endpoint measurements in evaluating the cytotoxicity of three divalent zinc salts in three established fish cell lines (EPC, CHSE and RTG-2) and the potential for their employment as effective screening tools for zinc contaminated environmental samples. A significant stimulatory effect was detected with the neutral red assay in EPC and RTG-2 cells exposed to the lower doses of some zinc compounds. Significant (p < or = 0.01) lactate dehydrogenase release was detectable only with the highest exposure concentration of ZnCl2. Toxicity ranking based on IC50 values calculated from the neutral red and coomassie blue assay data found that in general, ZnC2 was the most cytotoxic metal compound to the cell lines employed. Differential cell sensitivities were observed to be dependant on the particular compound tested and the endpoint employed. It was found that the use of light microscopy in the identification of cell morphological changes was a valuable adjunct in verifying the results of colorimetric tests. In conclusion, careful consideration should be given to study design and statistics applied and use of a battery style approach is recommended for toxicological screening studies.

The effects of glutathione and vitamin E on iron toxicity in isolated rat hepatocytes

This study examined the acute toxicity of ferrous sulfate on rat hepatocyte suspensions, the correlation between lipid peroxidation and cell death, and the roles of glutathione and vitamin E in protecting against iron toxicity. Incubation with ferrous sulfate for 2 h produced lipid peroxidation, but did not decrease cell viability in the hepatocytes. When diethyl maleate (DEM) was added to deplete cellular glutathione concentrations, ferrous sulfate treatment (2.0-5.0 mM) did cause cell death and lipid peroxidation developed more extensively, suggesting that iron-mediated hepatotoxicity is influenced by glutathione content. Reduced glutathione (GSH), N-acetylcysteine (NAC) and alpha-tocopherol (vitamin E), alone and in combination, were added to hepatocyte suspensions in an attempt to protect cells against iron-induced damage. In iron-DEM-treated cells, GSH and NAC treatment increased viability by 43 and 36%, respectively, but only the combination of the two agents reduced lipid peroxidation (53% decrease). Vitamin E treatment reduced lipid peroxidation by 39% and also increased cell viability by 12%. The greatest protection against iron-induced lipid peroxidation occurred with the combination of GSH, NAC and vitamin E, which reduced lipid peroxidation by 94% in iron-treated cells, and by 98% in iron-DEM-treated cells. However, this combination did not prevent iron-induced cell death, although it did increase viability by 18%. These results suggest that iron-induced cell death may not be dependent upon lipid peroxidation, at least in short-term exposures. The results also suggest an interaction between GSH and vitamin E in protecting against lipid peroxidation.

Ecotoxicity tests for compost applications

Interest in the ecological effects of composting has been growing recently. However, no established methods are available for testing the toxicity of composted materials. Despite this, international and national quality requirements define that compost shall not contain any environmentally harmful substances. Safety requirements have to be fulfilled if the produced compost is intended for agricultural use. This literature review focuses on methods that could potentially be used to evaluate the ecotoxicity of compost. The toxicity test methods discussed are those employing microbes, enzymes, soil fauna, and plants.

BACTOX, a rapid bioassay that uses protozoa to assess the toxicity of bacteria

A new type of toxicity test based on the protozoan Tetrahymena pyriformis has been developed to assess the overall toxicity of bacterial strains given as prey. This simple and rapid test is able to detect toxicant-producing bacteria, which may present a biohazard. It can also be used for the risk assessment of microbes designed for deliberate release.