Functional toxicity and tolerance patterns of bioavailable Pd(II), Pt(II), and Rh(III) on suspended Saccharomyces cerevisiae cells assayed in tandem by a respirometric biosensor

Exploring the Extent of Phosphorus and Heavy Metal Uptake by Single Cells of Saccharomyces cerevisiae and Their Effects on Intrinsic Elements by SC-ICP-TOF-MS

The effect of six heavy metals, namely, silver (Ag), lead (Pb), palladium (Pd), copper (Cu), nickel (Ni), and chromium (Cr), on phosphorus (P) uptake by yeast was investigated by single-cell analysis using inductively coupled plasma time-of-flight mass spectrometry (SC-ICP-TOF-MS). It was found that the P content in cells with 1.55 g L^–1 P feeding after P starvation was increased by ∼70% compared to control cells. Heavy metals at 10 ppm, except Cu, had a negative impact on P accumulation by cells. Pd reduced the P content by 26% in single cells compared to control cells. Metal uptake was strongest for Ag and Pd (0.7 × 10^–12 L cell^–1) and weakest for Cr (0.05 × 10^–12 L cell^–1). Exposure to Cr markedly reduced (−50%) Mg in cells and had the greatest impact on the intrinsic element composition. The SC-ICP-TOF-MS shows the diversity of elemental content in single cells: for example, the P content under standard conditions varied between 12.4 and 890 fg cell^–1. This technique allows studying both the uptake of elements and sublethal effects on physiology at a single-cell level.

Development of Cadmium Multiple-Signal Biosensing and Bioadsorption Systems Based on Artificial Cad Operons

The development of genetic engineering, especially synthetic biology, greatly contributes to the development of novel metal biosensors. The cad operon encoding cadmium resistance was previously characterized from Pseudomonas putida. In this study, single-, dual-, and triple-signal output Cd(II) biosensors were successfully developed using artificial translationally coupled cad operons. Sensitivity, selectivity, and response toward Cd(II) and Hg(II), of three biosensors were all determined. Reporter signals of three biosensors all increased within the range 0.1-3.125 μM Cd(II). Three biosensors responded strongly to Cd(II), and weakly to Hg(II). However, the detection ranges of Cd(II) and Hg(II) do not overlap in all three biosensors. Next, novel Cd(II) biosensing coupled with bioadsorptive artificial cad operons were assembled for the first time. Cd(II)-induced fluorescence emission, enzymatic indication, and Cd(II) binding protein surface display can be achieved simultaneously. This study provides an example of one way to realize multiple signal outputs and bioadsorption based on the redesigned heavy metal resistance operons, which may be a potential strategy for biodetection and removal of toxic metal in the environment, facilitating the study of the mechanism and dynamics of bioremediation.

Amperometric Cytosensor for Studying Mitochondrial Interferences Induced by Plasticizers Bisphenol B and Bisphenol A

The widespread presence of plasticizers Bisphenol B (BPB) and Bisphenol A (BPA) in food contact materials, medical equipment, and common household products is a toxicological risk factor for health due to internal exposure after environmental dietary exposure. This work describes the use of an amperometric cytosensor (i.e., a whole cell-based amperometric biosensoristic device) for studying mitochondrial interferences of BPA and BPB (5-100 µg/mL) in the yeast Saccharomyces cerevisiae model following long-term (24 h) exposure (acute toxicity). Percentage interference (%ρ) on yeast aerobic mitochondrial catabolism was calculated after comparison of aerobic respiration of exposed and control S. cerevisiae cell suspensions. Results suggested the hypothesis of a dose-dependent co-action of two mechanisms, namely uncoupling of oxidative phosphorylation and oxidative stress. These mechanisms respectively matched with opposite effects of hyperstimulation and inhibition of cellular respiration. While uncoupling of oxidative phosphorylation and oxidative stress have been previously described as separate effects from in vitro BPA exposure using other biochemical endpoints and biological systems, effects of BPB on cellular aerobic respiration are here reported for the first time. Results highlighted a similar hyperstimulation effect after exposure to 5 µg/mL BPA and BPB. About a 2-fold higher cellular respiration inhibition potency was observed after exposures to 15, 30, and 100 µg/mL BPB compared to BPA. 2,4-Dinitrophenol (2,4-DNP) was used as model uncoupling agent. A time-dependent mechanism of mitochondrial interference was also highlighted.

Towards Simazine Monitoring in Agro-Zootechnical Productions: A Yeast Cell Bioprobe for Real Samples Screening

Simazine is an herbicide that is able to contaminate surface waters, ground waters, and milk/dairy products, thus posing concerns in both environmental health and food safety. A yeast-based bioprobe was utilized to detect simazine in spiked real samples of livestock drinking water and raw cow's milk. Yeast aerobic respiration was taken as short-term toxicological endpoint. We carried out comparative measures of yeast oxygen consumption between simazine-spiked samples and blank samples. Percentage interference (%ρ) on yeast aerobic respiration was calculated through the comparison of aerobic respiration of simazine-exposed and non-exposed yeast cells. The method was optimized for raw cow's milk samples by using boric acid as fungistatic agent in order to avoid cellular proliferation. Overall, the results have shown that simazine can be detected up to concentrations five times below the EU legal concentration limits for drinking water (0.02 ppb) and cow's milk (2 ppb) (%ρ values of 18.53% and 20.43% respectively; %RSD ≤ 15%). Dose-effect relationships of simazine were assessed. The findings of the bioassays match reasonably well with known mechanisms of toxicity and intracellular detoxification in yeast. A correlation between fat content in milk samples and analytical performance of the bioprobe was established. Results suggest the involvement of a matrix effect, presumably due to lipid sequestration of simazine. The yeast-based bioprobe has proved to be sensitive and suitable for the detection of simazine in real samples in concentrations of interest.

Toxicity of platinum, palladium and rhodium to Daphnia magna in single and binary metal exposure experiments

Mainly due to automobile traffic, but also due to other sources, the platinum group elements (PGE) platinum (Pt), palladium (Pd) and rhodium (Rh) are introduced into aquatic biotopes where they accumulate in sediments of lakes and rivers. However, the toxicity of these noble metals to aquatic organisms is not well understood and especially toxicity studies under standardized condition are lacking. Thus, the toxicity of Pt, Pd and Rh to Daphnia magna was tested in single metal exposure experiments according to OECD guideline 202. Immobility and lethality was recorded after 24 h and 48 h of exposure and EC₅₀ and LC₅₀, respectively, were determined. As the nominal exposure concentration of Pd differed significantly from the quantified concentration, the control of the real exposure concentration by chemical analysis is mandatory, especially for Pd. The toxicity decreased in the order Pd > Pt ≫ Rh with e.g. LC₅₀(48 h) values of 14 μg/L for Pd, 157 μg/L for Pt and 56,800 μg/L for Rh. The exposure period had a clear effect on the toxicity of Pt, Pd and Rh. For Pt and Rh the endpoint immobility was more sensitive than the endpoint lethality whereas Pd toxicity was similar for both endpoints. The Hill slopes, which are a measure for the steepness of the concentration-response curves, showed no significant discrepancies between the different metals. The binary metal exposure to Pt and Pd revealed a more-than-additive, i.e. a synergistic toxicity using the toxic unit approach. The present study is a start to understand the toxicity of interacting PGE. The modes of action behind the synergistic effect are unclear.

Palladium nanoparticles exposure: Evaluation of permeation through damaged and intact human skin

The intensified use of palladium nanoparticles (PdNPs) in many chemical reactions, jewellery, electronic devices, in car catalytic converters and in biomedical applications lead to a significant increase in palladium exposure. Pd can cause allergic contact dermatitis when in contact with the skin. However, there is still a lack of toxicological data related to nano-structured palladium and information on human cutaneous absorption. In fact, PdNPs, can be absorbed through the skin in higher amounts than bulk Pd because NPs can release more ions. In our study, we evaluated the absorption of PdNPs, with a size of 10.7 ± 2.8 nm, using intact and damaged human skin in Franz cells. 0.60 mg cm(-2) of PdNPs were applied on skin surface for 24 h. Pd concentrations in the receiving solutions at the end of experiments were 0.098 ± 0.067 μg cm(-2) and 1.06 ± 0.44 μg cm(-2) in intact skin and damaged skin, respectively. Pd flux permeation after 24 h was 0.005 ± 0.003 μg cm(-2) h(-1) and 0.057 ± 0.030 μg cm(-2) h(-1) and lag time 4.8 ± 1.7 and 4.2 ± 3.6 h, for intact and damaged skin respectively. This study indicates that Pd can penetrate human skin.

Antioxidant power as biochemical endpoint in bread for screening and early managing quality and toxicant-related safety anomalies in food production

Flaxseeds are both a food ingredient and a natural source of antioxidants (e.g. lignans, PUFAs) and pro-oxidant contaminants (e.g. cadmium): the variable mixture of anti- and pro-oxidant substances may impact on the redox homeostasis of flaxseed-enriched foods. The antioxidant power is studied here as biochemical activity of flaxseeds in white wheat bread and as endpoint for possible screening of anomalous variations of bioactive mixtures (antioxidants vs. prooxidants) in food matrices. A bioprobe assay based on the superoxide dismutase (SOD) enzyme (6 channels of the multiprobe bioelectronic platform BEST) was performed on white wheat bread with and without flaxseeds. Nine BEST channels were simultaneously used for validation and monitoring of measuring conditions (temperature, pH, conductivity). Findings were compared with quantitative analysis of antioxidants and pro-oxidant contaminants. Organic and aqueous extracts of both bread types were examined in parallel. The SOD-probe detected the difference in antioxidant power given by 10% flaxseed, thus supporting the use of antioxidant power detected by bioenzymatic screening as sensitive biochemical endpoint. Mixtures of bioactive molecules in foods generate biochemical activities that can be monitored as time-effective indicators of invariability, which is pivotal in the daily control of anomalies in food production and therefore in the protection of consumers' health.

Diuron in water: functional toxicity and intracellular detoxification patterns of active concentrations assayed in tandem by a yeast-based probe

A study on the acute and chronic effects of the herbicide diuron was carried out. The test, basing on a yeast cell probe, investigated the interference with cellular catabolism and possible self-detoxification capacity of Saccharomyces cerevisiae. Aerobic respiration was taken as the toxicological end-point. Percentage interference (%r) with cellular respiration was measured in water by increased dissolved O2 concentration (ppm) after exposure to different doses. Interference was calculated through the comparison of respiratory activity of exposed and non-exposed cells. Short-term and long-term (6 and 24 h respectively) exposures were also considered. The test for short-term exposure gave positive %r values except that for 10-6 M (11.11%, 11.76%, 13.33% and 0% for 10-10 M, 10-8 M, 10-7 M and 10-6 M respectively). In the case of long-term exposure the test showed positive %r values, but less effect than short-term exposure until 10-8 M and much higher at 10-6 M (7.41%, 8.82%, 11.76% and 6.06% for 10-10 M, 10-8 M, 10-7 M and 10-6 M respectively). The findings of aerobic respiration as toxicological end-point were in agreement with known mechanisms of toxicity and intracellular detoxification for both the doses and exposure times employed.

The One Health Perspective in Trace Elements Biomonitoring

Health risks in both animals and humans are associated with chronic exposures to levels of trace elements (TE) eliciting toxic and/or antinutritional effects, including excess exposures to some essential elements. Interferences with essential TE may also lead to secondary nutritional deficiencies and/or imbalances. Although research is still required, biomarkers of exposure, including bioavailability, for TE are established tools for human biomonitoring that can also be applied to animal surveillance. Biomarkers of effect as well as, where available, of susceptibility and bioavailability are necessary to understand whether an ongoing exposure may pose a current or future health concern. In the field of animal health the use of biomarkers is less developed and less widespread than in human health; however, under a One Health perspective, animal biomonitoring can provide important information on the interfaces among humans, animals, and the environment, supporting the prevention and management of health risks. Therefore, a transfer of knowledge from human biomonitoring to farm or free-ranging animals is critical in a risk assessment framework from farm to humans. Advantages and critical aspects in designing and conducting integrative biomonitoring activities in humans and animals were critically reviewed focusing on biomarkers of exposure, effect, susceptibility, and bioavailability for toxic and essential TE. Highlighted aspects include TE metabolism, bioaccessibility, and interactions. Farm or free-ranging animals may provide noninvasive matrices suitable for evaluating animal welfare, environmental stressors, food safety, and potential risks for human health, as proposed by the interdisciplinary concept of One Health.

The effects on soil/water/plant/animal systems by platinum group elements

Emissions of toxic substances such as oxides of carbon, nitrogen, sulphur, and, in addition, aromatic hydrocarbons, aldehydes and heavy metals are the most serious problem of road traffic affecting landscape. Platinum group elements (PGE), which are the main component of the catalyst, are one of the main sources of heavy metals in the environment. Here, we review the way by which emissions and forms of the emitted PGE end up in the environment especially to the soil-water-plant-animal system. The major points discussed are the following: 1) the main sources of PGE emission are automobile exhaust catalysts; 2) hospitals, where platinum is widely used to treat malignant neoplasm, and urban waste water belonging to other important sources of PGE in the environment; 3) soil is one of the most important components of the environment that may be contaminated with platinum metals; 4) phytotoxicity of PGE depends on the following conditions: the concentration of metals in the soil, time of exposure, the chemical form of metal, the chemical composition of exposed soil and plant species; 5) animals are also endangered by the increasing concentration of PGE in the environment. Moreover, we pay our attention to thiol-based mechanisms of how an organism protects itself against platinum group elements.

Evaluating the cytotoxicity of palladium/magnetite nano-catalysts intended for wastewater treatment

Palladium/magnetite nanoparticulate catalysts were developed for efficient elimination of halogenated organic pollutants from contaminated wastewater. Particle recovery from treated water can be ensured via magnetic separation. However, in worst-case scenarios, this catalyst removal step might fail, leading to particle release into the environment. Therefore, a toxicological study was conducted to investigate the impact of both pure magnetite and palladium/magnetite nanoparticle exposure upon human skin (HaCaT) and human colon (CaCo-2) cell lines and a cell line from rainbow trout gills (RTgill-W1). To quantify cell viability after particle exposure, three endpoints were examined for all tested cell lines. Additionally, the formation of reactive oxygen species was studied for the human cells. The results showed only minor effects of the particles on the tested cell systems and support the assumption that palladium/magnetite nano-catalysts can be implemented for a new wastewater treatment technology in which advantageous catalyst properties outweigh the risks.

Airborne particulate matter, platinum group elements and human health: a review of recent evidence

Environmental concentrations of the platinum group elements (PGE) platinum (Pt), palladium (Pd) and rhodium (Rh) have been on the rise, due largely to the use of automobile catalytic converters which employ these metals as exhaust catalysts. It has generally been assumed that the health risks associated with environmental exposures to PGE are minimal. More recent studies on PGE toxicity, environmental bioavailability and concentrations in biologically relevant media indicate however that environmental exposures to these metals may indeed pose a health risk, especially at a chronic, subclinical level. The purpose of this paper is to review the most recent evidence and provide an up-to-date assessment of the risks related to environmental exposures of PGE, particularly in airborne particulate matter (PM). This review concludes that these metals may pose a greater health risk than once thought for several reasons. First, emitted PGE may be easily mobilised and solubilised by various compounds commonly present in the environment, thereby enhancing their bioavailability. Second, PGE may be transformed into more toxic species upon uptake by organisms. The presence of chloride in lung fluids, for instance, may lead to the formation of halogenated PGE complexes that have a greater potential to induce cellular damage. Third, a significant proportion of PGE found in airborne PM is present in the fine fraction that been found to be associated with increases in morbidity and mortality. PGE are also a concern to the extent that they contribute to the suite of metals found in fine PM suspected of eliciting a variety of health effects, especially in vulnerable populations. All these factors highlight the need to monitor environmental levels of PGE and continue research on their bioavailability, behaviour, speciation and associated toxicity to enable us to better assess their potential to elicit health effects in humans.

A new respirometric endpoint-based biosensor to assess the relative toxicity of chemicals on immobilized human cells

Several functional and biochemical parameters have been proposed as biomarkers of effect of environmental pollutants. A rapid biosensor working with immobilized human U-937 cells was developed and applied to environmentally relevant chemicals with different structures and toxicological pathways, i.e. benzalkonium chloride, clofibric acid, diclofenac, mercury nitrate, ofloxacin, and sodium dodecyl sulphate. Respiration of cells was relied upon as a comprehensive biochemical effect for screening purposes. Analytical parameter (DeltappmO(2)) and toxicological index (respiratory inhibition, delta%) measured after 1h of exposure were utilized for dose-response relationship study. Results (toxicity rating scales based on delta(50)% and steepness) were compared with those obtained by the same approach previously optimized on Saccharomyces cerevisiae. The toxicity rating scale obtained by the biomarker based on human mitochondrial and cell metabolic activities compared well with previous scale obtained on yeast cells and with available in-vivo acute toxicity indexes; respiration was confirmed as toxicological endpoint reliably measurable by the biosensor.