ORCID Profile
0000-0003-3451-7211
Current Organisations
Tallinna Tehnikaulikool
,
Tartu Ülikool
,
UCLA Life Sciences
,
University of South Australia
,
University of Tartu
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Publisher: MDPI AG
Date: 06-12-2022
DOI: 10.3390/NANO12234338
Abstract: History has demonstrated that the uncontrolled fast thriving of potentially pathogenic microorganisms may lead to serious consequences and, thus, the approaches helping to control the microbial numbers in infectional hot-spots are necessary [...]
Publisher: Elsevier BV
Date: 04-2004
Publisher: Elsevier BV
Date: 09-2020
Publisher: MDPI AG
Date: 14-12-2021
DOI: 10.3390/NANO11123384
Abstract: In the context of healthcare-acquired infections, microbial cross-contamination and the spread of antibiotic resistance, additional passive measures to prevent pathogen carryover are urgently needed. Antimicrobial high-touch surfaces that kill microbes on contact or prevent their adhesion could be considered to mitigate the spread. Here, we demonstrate that photocatalytic nano-ZnO- and nano-ZnO/Ag-based antibacterial surfaces with efficacy of at least a 2.7-log reduction in Escherichia coli and Staphylococcus aureus viability in 2 h can be produced by simple measures using a commercial acrylic topcoat for wood surfaces. We characterize the surfaces taking into account cyclic wear and variable environmental conditions. The light-induced antibacterial and photocatalytic activities of the surfaces are enhanced by short-term cyclic wear, indicating their potential for prolonged effectivity in long-term use. As the produced surfaces are generally more effective at higher relative air humidity and silver-containing surfaces lost their contact-killing properties in dry conditions, it is important to critically evaluate the end-use conditions of materials and surfaces to be tested and select application-appropriate methods for their efficacy assessment.
Publisher: American Chemical Society (ACS)
Date: 02-03-2018
Publisher: American Chemical Society (ACS)
Date: 13-11-2012
DOI: 10.1021/AR3000212
Abstract: Some researchers consider nanotechnology the next industrial revolution, and consumer products and a variety of industries increasingly use synthetic nanoparticles. In this Account, we review the initial accomplishments of nanoecotoxicology, a discipline that is just a decade old. This new subdiscipline of ecotoxicology faces two important and challenging problems: the analysis of the safety of nanotechnologies in the natural environment and the promotion of sustainable development while mitigating the potential pitfalls of innovative nanotechnologies. In this Account, we provide a snapshot of the publicly available scientific information regarding the ecotoxicity of engineered nanoparticles. We pay special attention to information relevant to aquatic freshwater species commonly used for risk assessment and regulation. Just as the development of ecotoxicology has lagged behind that of toxicology, nanoecotoxicological research has developed much more slowly than nanotoxicology. Although the first nanotoxicolology papers were published in 1990s, the first nanoecotoxicology papers came out in 2006. A meta-analysis of scientific publications covering different environmental impacts of nanomaterials showed that the importance of research into the environmental impact of nanotechnology has gradually increased since 2005. Now the most frequently cited papers in the environmental disciplines are often those that focus on synthetic nanoparticles. The first nanoecotoxicology studies focused on adverse effects of nanoparticles on fish, algae and daphnids, which are ecotoxicological model organisms for classification and labeling of chemicals (these model organisms are also used in the EU chemical safety policy adopted in 2007: Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH)). Based on our experience, we propose a multitrophic battery of nanoecotoxicological testing that includes particle-feeding and a priori particle-"proof" prokaryotic and eukaryotic organisms at different food-chain levels. Using this battery of selected test organisms, we demonstrated that TiO₂ nanoparticles were toxic to algae and that ZnO and CuO nanoparticles were toxic to several aquatic invertebrate test species. Thus, one single biotest cannot predict the ecotoxicological effects of chemicals/nanoparticles, and researchers should use several tests instead. Moreover, produced nanoparticles usually vary in features such as size, shape, and coating therefore, a single nanoparticle species may actually include many entities with different physicochemical properties. An ecotoxicity analysis of all these variants would require a huge number of laboratory tests. To address these issues, high throughput bioassays and computational (QSAR) models that serve as powerful alternatives to conventional (eco)toxicity testing must be implemented to handle both the ersity of nanomaterials and the complexity of ecosystems.
Publisher: Elsevier BV
Date: 08-2013
Publisher: MDPI AG
Date: 05-02-2022
Abstract: Photocatalytic and antibacterial properties of TiO2-based SaniTise™ glass by Pilkington were studied with an aim to benchmark this first commercial UVA-activated antimicrobial glass and to evaluate its efficacy in indoor-like conditions. For comparison, the antibacterial and photocatalytic activity of self-cleaning BIOCLEAN® glass and photocatalytically inactive clear float PLANICLEAR® control glass were analysed. The presence of an anatase TiO2 layer was demonstrated on the surface of SaniTise™ and BIOCLEAN®. Photocatalytic degradation of organic model dye and antibacterial activity against Escherichia coli and Staphylococcus aureus were higher on SaniTise™ than on BIOCLEAN®. In a liquid antibacterial assay corresponding to ISO 27447 format, 4 h exposure of bacteria to the SaniTise™ surface under UVA resulted in .8 log decrease in E. coli and .5 log decrease in S. aureus viable cell counts. In experiments with the more application-relevant “dry droplet method”, significantly higher antibacterial activity was observed up to the level where during 4 h at ≤50% RH complete inactivation of bacteria was observed also on PLANICLEAR® control glass. The latter raises concerns about the real-life relevancy of the standard test conditions and suggests that at low air humidity conditions, shorter exposure periods than suggested by current antimicrobial testing protocols should be targeted by photocatalytically active antibacterial surfaces.
Publisher: Elsevier BV
Date: 08-2011
Publisher: Elsevier BV
Date: 08-2012
DOI: 10.1016/J.JHAZMAT.2012.05.095
Abstract: The combined chemical and ecotoxicological characterization of oil shale combustion fly ash was performed. Ash was s led from the most distant point of the ash-separation systems of the Balti and Eesti Thermal Power Plants in North-Eastern Estonia. The fly ash proved potentially hazardous for tested aquatic organisms and high alkalinity of the leachates (pH>10) is apparently the key factor determining its toxicity. The leachates were not genotoxic in the Ames assay. Also, the analysis showed that despite long-term intensive oil-shale combustion accompanied by considerable fly ash emissions has not led to significant soil contamination by hazardous trace elements in North-Eastern Estonia. Comparative study of the fly ash originating from the 'new' circulating fluidized bed (CFB) combustion technology and the 'old' pulverized-fired (PF) one showed that CFB fly ash was less toxic than PF fly ash. Thus, complete transfer to the 'new' technology will reduce (i) atmospheric emission of hazardous trace elements and (ii) fly ash toxicity to aquatic organisms as compared with the 'old' technology.
Publisher: Cold Spring Harbor Laboratory
Date: 20-03-2020
DOI: 10.1101/2020.03.18.996967
Abstract: Spread of pathogenic microbes and antibiotic-resistant bacteria in health-care settings and public spaces is a serious public health challenge. Materials that prevent solid surface colonization or impede touch-transfer of viable microbes could provide means to decrease pathogen transfer from high-touch surfaces in critical applications. ZnO and Ag nanoparticles have shown great potential in antimicrobial applications. Less is known about nano-enabled surfaces. Here we demonstrate that surfaces coated with nano-ZnO or nano-ZnO/Ag composites are not cytotoxic to human keratinocytes and possess species-selective medium-dependent antibiofilm activity against Escherichia coli, Staphylococcus aureus and Candida albicans . Colonization of nano-ZnO and nano-ZnO/Ag surfaces by E. coli and S. aureus was decreased in static oligotrophic conditions (no planktonic growth). Moderate to no effect was observed for bacterial biofilms in growth medium (supporting exponential growth). Inversely, nano-ZnO surfaces enhanced biofilm formation by C. albicans in oligotrophic conditions. However, enhanced C. albicans biofilm formation on nano-ZnO surfaces was effectively counteracted by the addition of Ag. Possible selective enhancement of biofilm formation by the yeast C. albicans on Zn-enabled surfaces should be taken into account in antimicrobial surface development. Our results also indicated the importance of the use of application-appropriate test conditions and exposure medium in antimicrobial surface testing.
Publisher: American Chemical Society (ACS)
Date: 15-11-2017
Abstract: Gold nanoclusters (Au NCs) have become a promising nanomaterial for cancer therapy because of their biocompatibility and fluorescent properties. In this study, the effect of ultrasmall protein-stabilized 2 nm Au NCs on six types of mammalian cells (fibroblasts, B-lymphocytes, glioblastoma, neuroblastoma, and two types of prostate cancer cells) under electromagnetic radiation is investigated. Cellular association of Au NCs in vitro is concentration-dependent, and Au NCs have low intrinsic toxicity. However, when Au NC-incubated cells are exposed to a 1 GHz electromagnetic field (microwave radiation), cell viability significantly decreases, thus demonstrating that Au NCs exhibit specific microwave-dependent cytotoxicity, likely resulting from localized heating. Upon i.v. injection in mice, Au NCs are still present at 24 h post administration. Considering the specific microwave-dependent cytotoxicity and low intrinsic toxicity, our work suggests the potential of Au NCs as effective and safe nanomedicines for cancer therapy.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7BM01012E
Abstract: Phosphoryl choline grafting secured high cellular uptake and increased transcytosis of superparamagnetic iron oxide nanoparticles through a model blood brain barrier.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6LC01261B
Abstract: A crossed flow microfluidic device was used for generation of cell-based arrays aiming for high throughput screening of applied bioactive chemicals to captured cells.
Publisher: Informa UK Limited
Date: 21-11-2013
DOI: 10.3109/17435390.2013.855831
Abstract: Silver, ZnO and CuO nanoparticles (NPs) are increasingly used as biocides. There is however increasing evidence of their threat to "non-target" organisms. In such a context, the understanding of the toxicity mechanisms is crucial for both the design of more efficient nano-antimicrobials, i.e. for "toxic by design" and at the same time for the design of nanomaterials that are biologically and/or environmentally benign throughout their life-cycle (safe by design). This review provides a comprehensive and critical literature overview on Ag, ZnO and CuO NPs' toxicity mechanisms on the basis of various environmentally relevant test species and mammalian cells in vitro. In addition, factors modifying the toxic effect of nanoparticles, e.g. impact of the test media, are discussed. Literature analysis revealed three major phenomena driving the toxicity of these nanoparticles: (i) dissolution of nanoparticles, (ii) organism-dependent cellular uptake of NPs and (iii) induction of oxidative stress and consequent cellular damages. The emerging information on quantitative structure-activity relationship modeling of nanomaterials' toxic effects and the challenges of extrapolation of laboratory results to the environment are also addressed.
Publisher: Elsevier BV
Date: 02-2007
DOI: 10.1016/J.BIOS.2006.06.019
Abstract: Fibre-optic biosensors for Hg and As were developed by attaching alginate-immobilised recombinant luminescent Hg- and As-sensor bacteria onto optical fibres. The optimised biosensors (consisting of seven layers of fibre-attached bacteria pre-grown till mid-logarithmic growth phase) enabled quantification of environmentally relevant concentrations of the target analytes: 2.6 microg l-1 of Hg(II) and 141 microg l-1 of As(V) or 18 microg l-1 of As(III). The highest viability and sensitivity for target analyte was obtained when fibre tips were stored in CaCl2 solution at -80 degrees C. Applicability of the fibre-optic biosensors in parallel to the respective non-immobilised sensors was assessed on 10 natural soil and sediment s les from Aznalcollar mining area (Spain). On the average 0.2% of the total Hg and 0.87% of the total As proved bioavailable to fibre-attached bacteria. Interestingly, about 20-fold more Hg and 4-fold more As was available to non-immobilised sensor bacteria indicating the importance of direct cell contact (possible only for non-immobilised cells) for enhanced bioavailability of these metals in solid s les.
Publisher: Beilstein Institut
Date: 25-08-2015
DOI: 10.3762/BJNANO.6.183
Abstract: The increasing production and use of engineered nanomaterials (ENMs) inevitably results in their higher concentrations in the environment. This may lead to undesirable environmental effects and thus warrants risk assessment. The ecotoxicity testing of a wide variety of ENMs rapidly evolving in the market is costly but also ethically questionable when bioassays with vertebrates are conducted. Therefore, alternative methods, e.g., models for predicting toxicity mechanisms of ENMs based on their physico-chemical properties (e.g., quantitative (nano)structure-activity relationships, QSARs/QNARs), should be developed. While the development of such models relies on good-quality experimental toxicity data, most of the available data in the literature even for the same test species are highly variable. In order to map and analyse the state of the art of the existing nanoecotoxicological information suitable for QNARs, we created a database NanoE-Tox that is available as Supporting Information File 2. The database is based on existing literature on ecotoxicology of eight ENMs with different chemical composition: carbon nanotubes (CNTs), fullerenes, silver (Ag), titanium dioxide (TiO 2 ), zinc oxide (ZnO), cerium dioxide (CeO 2 ), copper oxide (CuO), and iron oxide (FeO x Fe 2 O 3 , Fe 3 O 4 ). Altogether, NanoE-Tox database consolidates data from 224 articles and lists altogether 1,518 toxicity values (EC 50 /LC 50 /NOEC) with corresponding test conditions and physico-chemical parameters of the ENMs as well as reported toxicity mechanisms and uptake of ENMs in the organisms. 35% of the data in NanoE-Tox concerns ecotoxicity of Ag NPs, followed by TiO 2 (22%), CeO 2 (13%), and ZnO (10%). Most of the data originates from studies with crustaceans (26%), bacteria (17%), fish (13%), and algae (11%). Based on the median toxicity values of the most sensitive organism (data derived from three or more articles) the toxicity order was as follows: Ag ZnO CuO CeO 2 CNTs TiO 2 FeO x . We believe NanoE-Tox database contains valuable information for ENM environmental hazard estimation and development of models for predicting toxic potential of ENMs.
Publisher: Springer Science and Business Media LLC
Date: 10-08-2020
DOI: 10.1038/S41598-020-70169-W
Abstract: Spread of pathogenic microbes and antibiotic-resistant bacteria in health-care settings and public spaces is a serious public health challenge. Materials that prevent solid surface colonization or impede touch-transfer of viable microbes could provide means to decrease pathogen transfer from high-touch surfaces in critical applications. ZnO and Ag nanoparticles have shown great potential in antimicrobial applications. Less is known about nano-enabled surfaces. Here we demonstrate that surfaces coated with nano-ZnO or nano-ZnO/Ag composites are not cytotoxic to human keratinocytes and possess species-selective medium-dependent antibiofilm activity against Escherichia coli , Staphylococcus aureus and Candida albicans . Colonization of nano-ZnO and nano-ZnO/Ag surfaces by E. coli and S. aureus was decreased in static oligotrophic conditions (no planktonic growth). Moderate to no effect was observed for bacterial biofilms in growth medium (supporting exponential growth). Inversely, nano-ZnO surfaces enhanced biofilm formation by C. albicans in oligotrophic conditions. However, enhanced C. albicans biofilm formation on nano-ZnO surfaces was effectively counteracted by the addition of Ag. Possible selective enhancement of biofilm formation by the yeast C. albicans on Zn-enabled surfaces should be taken into account in antimicrobial surface development. Our results also indicated the importance of the use of application-appropriate test conditions and exposure medium in antimicrobial surface testing.
Publisher: Springer New York
Date: 2019
DOI: 10.1007/978-1-4939-9454-0_21
Abstract: This chapter was inadvertently published with the acknowledgement section leaving out the following sentence: "This work received funding from South Australian Government PRIF program Project "International Cluster on Nanosafety" of Nicolas H. Voelcker and Enzo Lombi." This correction has been updated in the chapter.
Publisher: Wiley
Date: 21-07-2017
DOI: 10.1002/WNAN.1486
Abstract: How to study nanoparticle–cell interactions is the key question that puzzles researchers in the fields of nanomedicine as well as in nanotoxicology. In nanotoxicology, the amount of nanoparticles internalized by the cells or bound to the external surfaces of cells determines the toxic profile of those particles. In medical applications, cellular uptake and binding of medically effective nanoparticles decides their efficacy. Despite the importance of understanding the extent and mode of nanoparticle–cell interactions, these processes are underinvestigated, mainly due to the lack of suitable user‐friendly methodologies. Here we discuss the advantages and limitations of currently available (and most advanced) microscopic, spectroscopic, and other bioanalytical methods that could be used to assess cell‐nanoparticle interactions either qualitatively or quantitatively. Special emphasis is given to the methods that enable analysis and identification of nanoparticles at single‐cell level, and allow intracellular localization and speciation analysis of nanoparticles. This article is categorized under: Nanotechnology Approaches to Biology Cells at the Nanoscale Toxicology and Regulatory Issues in Nanomedicine Toxicology of Nanomaterials
Publisher: Elsevier BV
Date: 09-2006
DOI: 10.1016/J.CHEMOSPHERE.2006.01.026
Abstract: A whole-cell recombinant bacterial sensor for the detection of phenolic compounds was constructed and used for the analysis of bioavailable phenols in natural s les. The sensor Pseudomonas fluorescens OS8(pDNdmpRlux) contains luxCDABE operon as a reporter under the control of phenol-inducible Po promoter from Pseudomonas sp. CF600. Expression of lux genes from the Po promoter, and thus the production of bioluminescence is controlled by the transcriptional activator DmpR, which initiates transcription in the presence of phenolic compounds. To take into account possible quenching (turbidity, toxicity) and/or stimulating effects of the environmental s les on the bacterial luminescence, control bacteria comparable to the sensors but lacking the phenol recognising elements were constructed and used in parallel in assays. The sensor bacteria were inducible with phenol, methylphenols, 2,3-, 2,4-, 2,6- and 3,4-dimethylphenol, resorcinol and 5-methylresorcinol but not with 2,5-dimethylresorcinol. The detection limits for different phenols varied from 0.03 mg/l (2-methylphenol) to 42.7 mg/l (5-methylresorcinol), being 0.08 mg/l for phenol, the most abundant phenolic contaminant in the environment. Different phenolic compounds had an additive effect on the inducibility of the sensor. The constructed sensor bacteria were applied on groundwaters and semi-coke leachates to estimate the bioavailable fraction of phenols. The sensor-determined amount of phenols in different s les varied from 6% to 95% of total phenol content depending on the nature of the s le. As the phenol-recognising unit in the sensor originates from a natural phenol biodegradation pathway, the sensor-determined amount of phenols corresponds to the biodegradable amount of phenolic pollutants in the s les and therefore this sensor could be used to estimate the natural biodegradation potential of phenolic compounds in the complex environmental mixtures and matrixes.
Publisher: American Chemical Society (ACS)
Date: 24-07-2017
DOI: 10.1021/ACS.ANALCHEM.7B01006
Abstract: Quantification of cell-associated nanoparticles (NPs) is a paramount question in both nanomedicine and nanotoxicology. Inductively coupled plasma mass spectrometry is a well-established method to resolve cell-associated (metal) NPs in bulk cell populations, however, such analysis at single cell level remains a challenge. Here we used mass cytometry, a technique that combines single cell analysis and time-of-flight mass spectrometry, to quantitatively analyze extra- and intracellular silver (Ag) in in idual Ag NP exposed human T-lymphocytes. The results revealed significant population heterogeneity: for ex le, in lymphocytes exposed to 3 μg of 30 nm branched polyethylene imine coated Ag NPs/mL the extracellularly bound Ag varied from 79 to 560 fg and cellular uptake from 17 to 121 fg. Similar litude of heterogeneity was observed in cells exposed to various doses of Ag NPs with other sizes and surface coatings, demonstrating the importance of single cell analysis when studying NP-cell interactions. Although mass cytometry has some shortcomings such as inability to analyze potential transformation or dissolution of NPs in cells, we consider this method as the most promising for quantitative assessment of cell-NP interaction at single cell level.
Publisher: Public Library of Science (PLoS)
Date: 23-08-2016
Publisher: Elsevier BV
Date: 06-2012
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C2EM30731F
Abstract: In the current study, cell-free exudates of the ciliated protozoan Tetrahymena thermophila were shown to progressively convert silver nitrate to silver nanoparticles (Ag NPs) under illumination at ambient temperature. The formation of Ag NPs in the reaction mixture was evidenced by gradual colour changes, appearance of a specific absorbance peak (420–450 nm) and visualization using scanning electron microscopy coupled to an energy-dispersive X-ray spectrometer. After 2 h of incubation the mean hydrodynamic size of the Ag NPs was 70 nm. Seven days of incubation resulted in larger agglomerates and a significant decrease in silver toxicity to T. thermophila, accompanied by about 100-fold reduction in the silver ion concentration. Protein analysis indicated an extensive extracellular protein binding by the Ag NPs formed in the protozoan exudates. As protozoa are important components in wastewater treatment, their ability to sequester silver ions into a less bioavailable and less toxic form of silver (e.g. NPs) may be one of the adaption mechanisms of ciliate survival in contaminated environments.
Publisher: Elsevier BV
Date: 08-2013
Publisher: Springer Science and Business Media LLC
Date: 22-06-2005
DOI: 10.1007/S00216-005-3338-6
Abstract: The present work studies the adsorption behaviour of mercury species on different soil components (montmorillonite, kaolinite and humic acid) spiked with CH3HgCl and CH3HgOH at different pH values, by using XAS techniques and bacterial mercury sensors in order to evaluate the availability of methyl mercury on soil components. The study details and discusses different aspects of the adsorption process, including s le preparation (with analysis of adsorbed methyl mercury by ICP-OES), the various adsorption conditions, and the characterization of spiked s les by XAS techniques performed at two synchrotron facilities (ESRF in Grenoble, France and HASYLAB in Hamburg, Germany), as well as bioavailability studies using mercury-specific sensor bacteria. Results show that XAS is a valuable qualitative technique that can be used to identify the bonding character of the Hg in mercury environment. The amount of methyl in mercury adsorbed to montmorillonite was pH-dependent while for all soil components studied, the bond character was not affected by pH. On the other hand, clays exhibited more ionic bonding character than humic acids did with methyl mercury. This interaction has a higher covalent character and so it is more stable for CH3HgOH than for CH3HgCl, due to the higher reactivity of the hydroxyl group arising from the possible formation of hydrogen bonds. The bioavailability of methyl mercury adsorbed to montmorillonite, kaolinite and humic acids was measured using recombinant luminescent sensor bacterium Escherichia coli MC1061 (pmerBR(BS)luc). In case of contact exposure (suspension assays), the results showed that the bioavailability was higher than it was for exposure to particle-free extracts prepared from these suspensions. The highest bioavailability of methyl mercury was found in suspensions of montmorillonite (about 50% of the total amount), while the bioavailabilities of kaolinite and humic acids were five times lower (about 10%). The behaviour of methyl mercury in the presence of montmorillonite could be explained by the more ionic bonding character of this system, in contrast to the more covalent bonding character observed for humic acids. Thus, XAS techniques seem to provide promising tools for investigating the mechanisms behind the observed bioavailabilities of metals in various environmental matrices, an important topic in environmental toxicology.
Publisher: Springer Science and Business Media LLC
Date: 15-01-2010
DOI: 10.1007/S00248-009-9626-5
Abstract: In this study, the mixture of mono- and di-rhamnolipids produced by Pseudomonas aeruginosa DS10-129 was characterized for its toxicity and modulatory effects on Cd availability to different bacteria. Gram-negative naturally bioluminescent Vibrio fischeri and recombinant bioluminescent Pseudomonas fluorescens, P. aeruginosa, Escherichia coli, and Gram-positive Bacillus subtilis were used as model organisms. Rhamnolipids reduced the bioluminescence of these bacteria in less than a second of exposure even in relatively low concentrations (30-min EC(50) 45-167 mg l(-1)). Toxicity of Cd to Gram-negative bacteria (30-min EC(50) values 0.16 mg l(-1) for E. coli, 0.96 mg l(-1) for P. fluorescens, and 4.4 mg l(-1) for V. fischeri) was remarkably (up to 10-fold) reduced in the presence of 50 mg l(-1) rhamnolipids. Interestingly, the toxicity of Cd to Gram-positive B. subtilis (30-min EC(50) value 0.49 mg l(-1)) was not affected by rhamnolipids. Rhamnolipids had an effect on desorption of Cd from soil: 40 mg l(-1) rhamnolipids increased the water-extracted fraction of Cd twice compared with untreated control. However, this additionally desorbed fraction of Cd remained bound with rhamnolipids and was not available to bacteria. Hence, in carefully chosen concentrations (still effectively complexing heavy metals but not yet toxic to soil bacteria), rhamnolipids could be applied in remediation of polluted areas.
Publisher: Springer Science and Business Media LLC
Date: 10-12-2016
DOI: 10.1007/S00204-016-1897-2
Abstract: The rapid development of nanotechnologies and increased production and use of nanomaterials raise concerns about their potential toxic effects for human health and environment. To evaluate the biological effects of nanomaterials, a set of reliable and reproducible methods and development of standard operating procedures (SOPs) is required. In the framework of the European FP7 NanoValid project, three different cell viability assays (MTS, ATP content, and caspase-3/7 activity) with different readouts (absorbance, luminescence and fluorescence) and two immune assays (ELISA of pro-inflammatory cytokines IL1-β and TNF-α) were evaluated by inter-laboratory comparison. The aim was to determine the suitability and reliability of these assays for nanosafety assessment. Studies on silver and copper oxide nanoparticles (NPs) were performed, and SOPs for particle handling, cell culture, and in vitro assays were established or adapted. These SOPs give precise descriptions of assay procedures, cell culture/seeding conditions, NPs ositive control preparation and dilutions, experimental well plate preparation, and evaluation of NPs interference. The following conclusions can be highlighted from the pan-European inter-laboratory studies: Testing of NPs interference with the toxicity assays should always be conducted. Interference tests should be designed as close as possible to the cell exposure conditions. ATP and MTS assays gave consistent toxicity results with low inter-laboratory variability using Ag and CuO NPs and different cell lines and therefore, could be recommended for further validation and standardization. High inter-laboratory variability was observed for Caspase 3/7 assay and ELISA for IL1-β and TNF-α measurements.
Publisher: American Chemical Society (ACS)
Date: 26-09-2001
DOI: 10.1021/AC010550V
Abstract: Mercury and its organic compounds, especially methylmercury, are hazardous compounds that concentrate in biota via biomagnification and cause severe neurological disorders in animals. In this paper, a recombinant whole-cell bacterial sensor for the detection of the organic compounds of mercury was constructed. The sensor carries firefly luciferase gene as a reporter under the control of the mercury-inducible regulatory part of broad spectrum mer operon from pDU1358. In addition, a gene-encoding organomercurial lyase (an enzyme necessary for cleavage of the mercury-carbon bond) was coexpressed in the sensor strain. The sensitivity of the sensor was evaluated on some environmentally important organomercurial compounds. The lowest detectable concentrations were 0.2 nM (50 ng/L), 1 nM (0.34 microg/L), and 10 microM (2.3 mg/L) for methylmercury chloride, phenylmercury acetate, and dimethylmercury, respectively. The sensor responded also to inorganic mercury and, therefore, using the sensor described here together with sensor bacteria responding only to inorganic mercury, it should be possible to characterize the mercury contamination, for ex le, in environmental s les.
Publisher: Cold Spring Harbor Laboratory
Date: 23-11-2018
DOI: 10.1101/475145
Abstract: Combining membrane impermeable DNA-binding stain propidium iodide (PI) with membrane-permeable DNA-binding counterstains is a widely used approach for bacterial viability staining. In this paper we show that PI staining of adherent cells in biofilms may significantly underestimate bacterial viability due to the presence of extracellular nucleic acids. We demonstrate that gram-positive Staphylococcus epidermidis and gram-negative Escherichia coli 24-hour initial biofilms on glass consist of 76 and 96% PI-positive red cells in situ , respectively, even though 68% the cells of either species in these aggregates are metabolically active. Furthermore, 82% of E. coli and 89% S. epidermidis are cultivable after harvesting. Confocal laser scanning microscopy (CLSM) revealed that this false dead layer of red cells is due to a subpopulation of double-stained cells that have green interiors under red coating layer which hints at extracellular DNA (eDNA) being stained outside intact membranes. Therefore, viability staining results of adherent cells should always be validated by an alternative method for estimating viability, preferably by cultivation.
Publisher: Elsevier BV
Date: 11-2005
DOI: 10.1016/J.SCITOTENV.2005.01.029
Abstract: Twenty urban soil s les, with a wide range of Pb (14-5323 mg/kg) and Cu (8-12987 mg/kg), were used to compare the operational speciation of a five-step sequential leach with the bioavailability determined with bioluminescent Pb (RN4220(pTOO24)) and Cu (MC1061(pSLcueR DNPcopAluc)) specific bacterial biosensors and a Cu specific yeast sensor. The bioavailable Pb concentrations were all similar or lower than the first sequential leach step (1M NaOAc). In contrast, in some s les the bioavailable concentrations of Cu clearly exceeded even the second sequential leach step (0.1 M Na4P2O7). With the yeast sensor 12/20 s les were below detection, however, the yeast sensor was capable of detecting all high Cu concentrations. The biosensors used in this study are not capable of detecting the natural soil concentrations of Pb and Cu in the studied area.
Publisher: Elsevier BV
Date: 04-2008
DOI: 10.1016/J.CHEMOSPHERE.2007.11.047
Abstract: As the production of nanoparticles of ZnO, TiO2 and CuO is increasing, their (eco)toxicity to bacteria Vibrio fischeri and crustaceans Daphnia magna and Thamnocephalus platyurus was studied with a special emphasis on product formulations (nano or bulk oxides) and solubilization of particles. Our innovative approach based on the combination of traditional ecotoxicology methods and metal-specific recombinant biosensors allowed to clearly differentiate the toxic effects of metal oxides per se and solubilized metal ions. Suspensions of nano and bulk TiO2 were not toxic even at 20 g l(-1). All Zn formulations were very toxic: L(E)C50 (mg l(-1)) for bulk ZnO, nanoZnO and ZnSO4.7H2O: 1.8, 1.9, 1.1 (V. fischeri) 8.8, 3.2, 6.1 (D. magna) and 0.24, 0.18, 0.98 (T. platyurus), respectively. The toxicity was due to solubilized Zn ions as proved with recombinant Zn-sensor bacteria. Differently from Zn compounds, Cu compounds had different toxicities: L(E)C50 (mg l(-1)) for bulk CuO, nano CuO and CuSO4: 3811, 79, 1.6 (V. fischeri), 165, 3.2, 0,17 (D. magna) and 95, 2.1, 0.11 (T. platyurus), respectively. Cu-sensor bacteria showed that toxicity to V. fischeri and T. platyurus was largely explained by soluble Cu ions. However, for Daphnia magna, nano and bulk CuO proved less bioavailable than for bacterial Cu-sensor. This is the first evaluation of ZnO, CuO and TiO2 toxicity to V. fischeri and T. platyurus. For nano ZnO and nano CuO this is also a first study for D. magna.
Publisher: American Chemical Society (ACS)
Date: 24-12-2013
DOI: 10.1021/NN4044047
Abstract: Silver nanoparticles (Ag NPs) are commonly added to various consumer products and materials to impair bacterial growth. Recent studies suggested that the primary mechanism of antibacterial action of silver nanoparticles is release of silver ion (Ag(+)) and that particle-specific activity of silver nanoparticles is negligible. Here, we used a genome-wide library of Escherichia coli consisting of ∼4000 single gene deletion mutants to elucidate which physiological pathways are involved in how E. coli responds to different Ag NPs. The nanoparticles studied herein varied in both size and surface charge. AgNO3 was used as a control for soluble silver ions. Within a series of differently sized citrate-coated Ag NPs, smaller size resulted in higher Ag ion dissolution and toxicity. Nanoparticles functionalized with cationic, branched polyethylene imine (BPEI) exhibited equal toxicity with AgNO3. When we used a genome-wide approach to investigate the pathways involved in the response of E. coli to different toxicants, we found that only one of the particles (Ag-cit10) exhibited a pattern of response that was statistically similar to that of silver ion. By contrast, the pathways involved in E. coli response to Ag-BPEI particles were more similar to those observed for another cationic nanoparticle that did not contain Ag. Overall, we found that the pathways involved in bacterial responses to Ag nanoparticles are highly dependent on physicochemical properties of the nanoparticles, particularly the surface characteristics. These results have important implications for the regulation and testing of silver nanoparticles.
Publisher: Elsevier BV
Date: 09-2023
Publisher: Springer Science and Business Media LLC
Date: 13-05-2021
DOI: 10.1038/S41565-021-00914-3
Abstract: Our knowledge of uptake, toxicity and detoxification mechanisms as related to nanoparticles' (NPs') characteristics remains incomplete. Here we combine the analytical power of three advanced techniques to study the cellular binding and uptake and the intracellular transformation of silver nanoparticles (AgNPs): single-particle inductively coupled mass spectrometry, mass cytometry and synchrotron X-ray absorption spectrometry. Our results show that although intracellular and extracellularly bound AgNPs undergo major transformation depending on their primary size and surface coating, intracellular Ag in 24 h AgNP-exposed human lymphocytes exists in nanoparticulate form. Biotransformation of AgNPs is dominated by sulfidation, which can be viewed as one of the cellular detoxification pathways for Ag. These results also show that the toxicity of AgNPs is primarily driven by internalized Ag. In fact, when toxicity thresholds are expressed as the intracellular mass of Ag per cell, differences in toxicity between NPs of different coatings and sizes are minimized. The analytical approach developed here has broad applicability in different systems where the aim is to understand and quantify cell-NP interactions and biotransformation.
Publisher: Wiley
Date: 26-03-2019
Abstract: Crop raiding by wildlife poses major threats to both wildlife conservation and human well-being in agroecosystems worldwide. These threats are particularly acute in many parts of Africa, where crop raiders include globally threatened megafauna such as elephants, and where smallholder agriculture is a primary source of human livelihood. One framework for understanding herbivore feeding behaviour, the forage-maturation hypothesis, predicts that herbivores should align their movements with intermediate forage biomass (i.e., peak green-up) this phenomenon is known as "surfing the green wave." Crop-raiding elephants, however, often consume not just foliage, but also fruits and tubers (e.g., maize and potatoes), which generally mature after seasonal peaks in photosynthetic activity. Thus, although elephants have been reported to surf the green wave in natural habitats, they may utilize a different strategy in cultivated landscapes by selecting crops that are "browning down." We sought to understand the factors that underpin movement of elephants into agricultural landscapes. In Mozambique's Gorongosa National Park, we used movement data from GPS-collared elephants, together with precipitation records, remotely sensed estimates of landscape greenness (NDVI), DNA-based diet analysis, measurements of plant nutritional quality and survey-based metrics of crop availability to understand spatiotemporal variation in elephant crop-raiding behaviour. Elephants tracked peak NDVI while foraging inside the Park. During the dry season, however, when NDVI within the Park declined and availability of mature crops was high, crop raiding increased dramatically, and elephants consistently selected crop plants that were browning down while foraging in cultivated landscapes. Crops contained significantly higher digestible energy than wild food plants, but comparable (and sometimes lower) levels of digestible protein, suggesting that this foraging strategy maximized energy rather than protein intake. Our study is the first to combine GPS tracking data with high-resolution diet analysis and community-based reporting of crop availability to reveal fine-scale plasticity in foraging behaviour of elephants at the human-wildlife interface. Our results extend the forage-maturation hypothesis by showing that elephants surf waves of plant brown-down in cultivated landscapes. These findings can aid efforts to reduce human-elephant conflict by enabling wildlife managers to prioritize mitigation actions in time and space with limited resources.
Publisher: Springer Science and Business Media LLC
Date: 13-07-2010
DOI: 10.1007/S00216-010-3962-7
Abstract: We propose a novel combination of high-throughput luminescent bacterial tests for the evaluation of the reactive oxygen species (ROS)-generating potential of engineered nanoparticles (eNPs) and the role of solubilised metal ions in this process. The set of tests consists of differently engineered recombinant Escherichia coli strains: (1) a new sensor strain, which bioluminescence is induced by superoxide anions (2) six recombinant E. coli strains (superoxide dismutase (sod) single, double and triple mutants and a respective wild-type strain), transformed with luxCDABE genes responding to toxic compounds by decreasing their luminescence and (3) three strains in which bioluminescence is specifically induced by bioavailable metals (Cu, Zn and Ag). The applicability of this battery of tests in profiling oxidative potential of eNPs was evaluated on nTiO(2), nCuO, nZnO and nAg (25, 30, 70 and 4,000 mg l(-1)) although nTiO(2) (but not bTiO(2)) induced the bioluminescence of the superoxide anion sensing bacteria starting from 100 mg l(-1). Thus, our innovative combined approach is expected to provide more consistent and informative data concerning the general toxicity, ROS-production potential and also solubilisation of metals in the case of metallic NPs.
Publisher: Public Library of Science (PLoS)
Date: 21-07-2014
Publisher: Springer Science and Business Media LLC
Date: 03-08-2015
Publisher: Elsevier BV
Date: 2010
DOI: 10.1016/J.ENVPOL.2009.08.017
Abstract: The acute toxicity of CuO and ZnO nanoparticles in artificial freshwater (AFW) and in natural waters to crustaceans Daphnia magna and Thamnocephalus platyurus and protozoan Tetrahymena thermophila was compared. The L(E)C(50) values of nanoCuO for both crustaceans in natural water ranged from 90 to 224 mg Cu/l and were about 10-fold lower than L(E)C(50) values of bulk CuO. In all test media, the L(E)C(50) values for both bulk and nanoZnO (1.1-16 mg Zn/l) were considerably lower than those of nanoCuO. The natural waters remarkably (up to 140-fold) decreased the toxicity of nanoCuO (but not that of nanoZnO) to crustaceans depending mainly on the concentration of dissolved organic carbon (DOC). The toxicity of both nanoCuO and nanoZnO was mostly due to the solubilised ions as determined by specific metal-sensing bacteria.
Publisher: Elsevier BV
Date: 2015
DOI: 10.1016/J.JPHOTOBIOL.2014.12.010
Abstract: Titanium dioxide is a photocatalyst with well-known ability to oxidise a wide range of organic contaminants as well as to destroy microbial cells. In the present work TiO2 nanoparticles with high specific surface area (150m(2)/g) were used to prepare nanostructured films. The TiO2 nanoparticle-based film in combination with UV-A illumination with intensity (22W/m(2)) comparable to that of the sunlight in the UV-A region was used to demonstrate light-induced antibacterial effects. Fast and effective inactivation of Escherichia coli cells on the prepared thin films was observed. Visualization of bacterial cells under scanning electron microscopy (SEM) showed enlargement of the cells, distortion of cellular membrane and possible leakage of cytoplasm after 10min of exposure to photoactivated TiO2. According to the plate counts there were no viable cells as early as after 20min of exposure to UV-A activated TiO2. In parallel to effects on bacterial cell viability and morphology, changes in saturated and unsaturated fatty acids - important components of bacterial cell membrane-were studied. Fast decomposition of saturated fatty acids and changes in chemical structure of unsaturated fatty acids were detected. Thus, we suggest that peroxidation and decomposition of membrane fatty acids could be one of the factors contributing to the morphological changes of bacteria observed under SEM, and ultimately, cell death.
Publisher: Informa UK Limited
Date: 28-06-2016
DOI: 10.1080/17435390.2016.1196251
Abstract: Within EU FP7 project NANOVALID, the (eco)toxicity of 7 well-characterized engineered nanomaterials (NMs) was evaluated by 15 bioassays in 4 laboratories. The highest tested nominal concentration of NMs was 100 mg/l. The panel of the bioassays yielded the following toxicity order: Ag > ZnO > CuO > TiO2 > MWCNTs > SiO2 > Au. Ag, ZnO and CuO proved very toxic in the majority of assays, assumingly due to dissolution. The latter was supported by the parallel analysis of the toxicity of respective soluble metal salts. The most sensitive tests/species were Daphnia magna (towards Ag NMs, 24-h EC50 = 0.003 mg Ag/l), algae Raphidocelis subcapitata (ZnO and CuO, 72-h EC50 = 0.14 mg Zn/l and 0.7 mg Cu/l, respectively) and murine fibroblasts BALB/3T3 (CuO, 48-h EC50 = 0.7 mg Cu/l). MWCNTs showed toxicity only towards rat alveolar macrophages (EC50 = 15.3 mg/l) assumingly due to high aspect ratio and TiO2 towards R. subcapitata (EC50 = 6.8 mg Ti/l) due to agglomeration of TiO2 and entrapment of algal cells. Finally, we constructed a decision tree to select the bioassays for hazard ranking of NMs. For NM testing, we recommend a multitrophic suite of 4 in vitro (eco)toxicity assays: 48-h D. magna immobilization (OECD202), 72-h R. subcapitata growth inhibition (OECD201), 30-min Vibrio fischeri bioluminescence inhibition (ISO2010) and 48-h murine fibroblast BALB/3T3 neutral red uptake in vitro (OECD129) representing crustaceans, algae, bacteria and mammalian cells, respectively. Notably, our results showed that these assays, standardized for toxicity evaluation of "regular" chemicals, proved efficient also for shortlisting of hazardous NMs. Additional assays are recommended for immunotoxicity evaluation of high aspect ratio NMs (such as MWCNTs).
Publisher: MDPI AG
Date: 12-04-2017
DOI: 10.3390/MI8040124
Publisher: Wiley
Date: 14-04-2014
DOI: 10.1002/ESP.3572
Publisher: Springer Science and Business Media LLC
Date: 10-09-2010
Publisher: Elsevier BV
Date: 10-2018
DOI: 10.1016/J.COLSURFB.2018.06.027
Abstract: Silver nanoparticles (nanoAg) are effective antimicrobials and promising alternatives to traditional antibiotics. This study aimed at evaluating potency of different nanoAg against healthcare infections associated bacteria: Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. A library of differently coated nanoAg of two different sizes (10 and 50 nm) were prepared using coating agents poly-L-Lysine (PLL), cetyltrimethyl-ammonium bromide (CTAB), citrate (CIT), polyvinyl-pyrrolidone (PVP), polysorbate 80 (Tween 80), and dioctyl-sodium sulfosuccinate (AOT). Stability evaluation by means of agglomeration and dissolution behaviour was performed for all nanoAg under conditions relevant for this study. Antibacterial properties of nanoAg were addressed by determining their minimal bactericidal concentrations (MBC) in deionised (DI) water to minimise the influence of silver speciation on its bioavailability. In parallel, AgNO
Publisher: Elsevier BV
Date: 06-2017
DOI: 10.1016/J.ENVPOL.2017.03.013
Abstract: Silver nanoparticles (AgNPs) are highly toxic to aquatic organisms, however, there is no consensus whether the toxicity is caused solely by released Ag-ions or also by reactive oxygen species (ROS). Here, the effects of protein-coated AgNPs (14.6 nm, Collargol) were studied on viability, oxidative stress and gene expression levels in wild type strains (CU427 and CU428) of ciliate Tetrahymena thermophila. Viability-based 24 h EC
Publisher: PeerJ
Date: 11-02-2019
DOI: 10.7717/PEERJ.6315
Abstract: This review was initiated by the COST action CA15114 AMICI “Anti-Microbial Coating Innovations to prevent infectious diseases,” where one important aspect is to analyze ecotoxicological impacts of antimicrobial coatings (AMCs) to ensure their sustainable use. Scopus database was used to collect scientific literature on the types and uses of AMCs, while market reports were used to collect data on production volumes. Special attention was paid on data obtained for the release of the most prevalent ingredients of AMCs into the aqueous phase that was used as the proxy for their possible ecotoxicological effects. Based on the critical analysis of 2,720 papers, it can be concluded that silver-based AMCs are by far the most studied and used coatings followed by those based on titanium, copper, zinc, chitosan and quaternary ammonium compounds. The literature analysis pointed to biomedicine, followed by marine industry, construction industry (paints), food industry and textiles as the main fields of application of AMCs. The published data on ecotoxicological effects of AMCs was scarce, and also only a small number of the papers provided information on release of antimicrobial ingredients from AMCs. The available release data allowed to conclude that silver, copper and zinc are often released in substantial amounts (up to 100%) from the coatings to the aqueous environment. Chitosan and titanium were mostly not used as active released ingredients in AMCs, but rather as carriers for other release-based antimicrobial ingredients (e.g., conventional antibiotics). While minimizing the prevalence of healthcare-associated infections appeared to be the most prosperous field of AMCs application, the release of environmentally hazardous ingredients of AMCs into hospital wastewaters and thus, also the environmental risks associated with AMCs, comprise currently only a fraction of the release and risks of traditional disinfectants. However, being proactive, while the use of antimicrobial/antifouling coatings could currently pose ecotoxicological effects mainly in marine applications, the broad use of AMCs in other applications like medicine, food packaging and textiles should be postponed until reaching evidences on the (i) profound efficiency of these materials in controlling the spread of pathogenic microbes and (ii) safety of AMCs for the human and ecosystems.
Publisher: American Chemical Society (ACS)
Date: 02-2012
DOI: 10.1021/ES203087M
Abstract: By exploiting a genome-wide collection of bacterial single-gene deletion mutants, we have studied the toxicological pathways of a 60-nm cationic (amino-functionalized) polystyrene nanomaterial (PS-NH(2)) in bacterial cells. The IC(50) of commercially available 60 nm PS-NH(2) was determined to be 158 μg/mL, the IC(5) is 108 μg/mL, and the IC(90) is 190 μg/mL for the parent E. coli strain of the gene deletion library. Over 4000 single nonessential gene deletion mutants of Escherichia coli were screened for the growth phenotype of each strain in the presence and absence of PS-NH(2). This revealed that genes clusters in the lipopolysaccharide biosynthetic pathway, outer membrane transport channels, ubiquinone biosynthetic pathways, flagellar movement, and DNA repair systems are all important to how this organism responds to cationic nanomaterials. These results, coupled with those from confirmatory assays described herein, suggest that the primary mechanisms of toxicity of the 60-nm PS-NH(2) nanomaterial in E. coli are destabilization of the outer membrane and production of reactive oxygen species. The methodology reported herein should prove generally useful for identifying pathways that are involved in how cells respond to a broad range of nanomaterials and for determining the mechanisms of cellular toxicity of different types of nanomaterials.
Publisher: Springer New York
Date: 2019
DOI: 10.1007/978-1-4939-9454-0_15
Abstract: Mass cytometry is a technique that uses inductively coupled plasma mass spectrometry (ICP-MS) to quantify the isotopic composition of cells in suspension. Traditionally it has been used in conjunction with antibodies labeled with stable lanthanide isotopes to investigate cellular heterogeneity. Here we describe its use to quantify uptake of metal nanoparticles by cells in suspension.
Publisher: Elsevier BV
Date: 04-2015
DOI: 10.1016/J.JHAZMAT.2014.12.027
Abstract: Toxicity testing of nanomaterials (NMs) is experimentally challenging because NMs may interfere with test environment and assay components. In this work we propose a simple and reliable method--a 'spot test' to compare biocidal potency of NMs to unicellular microorganisms such as bacteria, yeasts and algae. The assay is straightforward: cells are incubated in deionized water suspensions of NMs for up to 24h and then pipetted as a 'spot' on agarized medium. Altogether seven bacterial strains, yeast and a microalga were tested. CuO, TiO2 and two different Ag NPs, multi-wall C-nanotubes (MWCNTs), AgNO3, CuSO4, 3,5-dichlorophenol, triclosan and H2O2 were analyzed. The biocidal potency of tested substances ranged from 0.1mg/L to >1000 mg/L whereas, the least potent NMs toward all test species were TiO2 NPs and MWCNTs and most potent Ag and CuO NPs. Based on the similar toxicity pattern of the tested chemicals on the nine unicellular organisms in deionized water we conclude that toxicity mechanism of biocidal chemicals seems to be similar, whatever the organism (bacteria, yeast, alga). Therefore, when the organisms are not 'protected' by their environment that usually includes various organic and inorganic supplements their tolerance to toxicants is chemical- rather than organism-dependent.
Publisher: Canadian Periodical for Community Studies
Date: 04-2001
Abstract: This study explored the service needs of families with a parent with an affective illness. Focus-group and in idual interviews were conducted at selected locations across Canada with in iduals who had an affective disorder, their partners, and their adult children. A total of 67 participants were recruited. Corresponding service providers were mailed a questionnaire which asked information regarding these families' needs, the service provider's role with these families, and what prevented or assisted them in addressing those needs. A total of 419 service providers participated in the study. There was congruence between family-identified needs and the needs identified by service providers. However, there remains a large disparity between the knowledge of needs and having these needs met. The results of this study identify the gaps in service provision and make recommendations for changes in the areas of service, education, and policy-making.
Publisher: MDPI AG
Date: 31-03-2017
Publisher: Informa UK Limited
Date: 06-02-2017
Publisher: MDPI AG
Date: 28-08-2008
DOI: 10.3390/S8085153
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.CARBPOL.2015.09.093
Abstract: Levan, fructose-composed biopolymer of bacterial origin, has potential in biotechnology due to its prebiotic and immunostimulatory properties. In this study levan synthesized by levansucrase from Pseudomonas syringae was thoroughly characterized and used as multifunctional biocompatible coating material for microelement-nanoparticles (NPs) of selenium, iron and cobalt. Transmission electron microscopy (TEM), hydrodynamic size measurements (DLS) and X-ray photoelectron spectroscopy (XPS) showed the interaction of levan with NPs. Levan stabilized the dispersions of NPs, decreased their toxicity and had protective effect on human intestinal cells Caco-2. In addition, levan attached to cobalt NPs remained accessible as a substrate for the colon bacteria Bacteroides thetaiotaomicron. We suggest that the combination of levan and nutritionally important microelements in the form of NPs serves as a first step towards a novel "2 in 1" approach for food supplements to provide safe and efficient delivery of microelements for humans and support beneficial gut microbiota with nutritional oligosaccharides.
Publisher: Springer Science and Business Media LLC
Date: 06-2013
Publisher: Wiley
Date: 09-2004
DOI: 10.1002/JAT.1020
Abstract: At the EILATox-Oregon Workshop, nine luminescent whole-cell bacterial sensors were used for the determination of bioavailable metals in blind s les (17 synthetic and 3 environmental). A non-inducible luminescent control strain was used to determine s le matrix effects and bacterial toxicity. Whole-cell bacterial sensors capable of determining arsenic, inorganic mercury and its organic derivatives, cadmium, lead or copper were used in suspensions and a bacterial sensor for the detection of inorganic mercury was immobilized onto fibre-optic tips using calcium alginate. Bioavailable amounts of metals were estimated using calibration plots, that were constructed to determine the range of metals giving rise to a linear relationship between luminescence and the amount of metals present in the standard solutions. EILATox-Oregon s le 5, which contained 74 mg l(-1) of Hg, gave a significant response with both formats of the mercury sensor. The bioavailable amounts of mercury according to the measurement of bacterial sensor in suspension and immobilized onto a fibre-optic tip were 76 and 93 mg l(-1), respectively. The bacterial sensor for arsenic and copper showed a response with s le 6 (58 mg l(-1) of As) and s le 8 (400 mg l(-1) of metham sodium), respectively. This study showed that the bacterial sensors in suspension or immobilized onto optical fibres are capable of quantifying bioavailable metals from unknown s les. The measurement protocol of bacterial sensors is simple and possible to perform in the field. Moreover, the s les do not need any pretreatment before analysis. Construction and characterization of the strain for the detection of bioavailable copper are described.
Publisher: Wiley
Date: 11-2005
DOI: 10.1897/05-002R1.1
Abstract: The combined chemical and ecotoxicological hazard evaluation study was conducted on 60 smelter-influenced soils containing 1 to 13, 50 to 653, and 100 to 1,198 mg/kg of Cd, Pb, and Zn, respectively. For these soils (liquid-to-soil ratio = 10), water extractability of Zn, Cd, and Pb was less than 0.19% (median values). Acetic acid (0.11 M) extracted 23, 9.7, and 0.7% of Cd, Zn, and Pb, respectively. Although heavy metal concentrations in the studied soils were high, the toxic effects of water extracts were observed only in few s les and in few biotests (algae Selenastrum capricornutum and metal detector assay). For most of the aquatic test organisms (e.g., crustaceans, photobacteria), the bioavailable concentrations of metals in soil-water extracts were either subtoxic, or the adverse effects were compensated by soil nutrients, etc. However, analysis of the soils with recombinant Cd sensor Bacillus subtilis (pTOO24) showed that about 65% of these apparently subtoxic s les contained bioavailable Cd when analyzed in the suspension assay (detection limit 1.5 mg Cd/kg soil), indicating the desorption of Cd induced by direct contact of bacteria with soil particles. The median bioavailable fraction of Cd (1%) was 23-fold lower than the fraction extracted by acetic acid. The Pb-Cd sensor Staphylococcus aureus (pT0024) detected bioavailable Pb only in the suspensions of five of the most lead-polluted soils (>417 mg Pb/kg): the median bioavailability of Pb was 0.42%. Consequently, the hazard assessment relying on total metal levels in soils should be revised by critical comparison with data obtained from bioassays. Development and use of biosensors (excellent tools for mechanistic studies and signaling hazard already at subtoxic level) should be encouraged.
Publisher: IOP Publishing
Date: 30-11-2017
Publisher: Springer Science and Business Media LLC
Date: 25-05-2018
DOI: 10.1038/S41598-018-26391-8
Abstract: Release of metal ions from metal-based surfaces has been considered one of the main drivers of their antimicrobial activity. Here we describe a method that enables parallel assessment of metal ion release from solid metallic surfaces and antimicrobial efficacy of these surfaces in a short time period. The protocol involves placement of a small volume of bioluminescent bacteria onto the tested surface and direct measurement of bioluminescence at various time points. In this study, two recombinant Escherichia coli strains, one expressing bioluminescence constitutively and applicable for general antimicrobial testing, and the other induced by Cu ions, were selected. Decrease in bioluminescence of constitutive E . coli on the surfaces showed a good correlation with the decrease in bacterial viability. Response of Cu-inducible E . coli showed a correlation with Cu content in the tested surfaces but not with Cu dissolution suggesting the role of direct bacteria-surface contact in Cu ion-driven antibacterial effects. In summary, the presented protocol enables the analysis of microbial toxicity and bioavailability of surface-released metal ions directly on solid surfaces within 30–60 min. Although optimized for copper and copper alloy surfaces and E . coli , the method can be extended to other types of metallic surfaces and bacterial strains.
Publisher: Bentham Science Publishers Ltd.
Date: 16-06-2015
DOI: 10.2174/1568026615666150506150109
Abstract: The knowledge on potential harmful effects of metallic nanomaterials lags behind their increased use in consumer products and therefore, the safety data on various nanomaterials applicable for risk assessment are urgently needed. In this study, 11 metal oxide nanoparticles (MeOx NPs) prepared using flame pyrolysis method were analyzed for their toxicity against human alveolar epithelial cells A549, human epithelial colorectal cells Caco2 and murine fibroblast cell line Balb/c 3T3. The cell lines were exposed for 24 h to suspensions of 3-100 μg/mL MeOx NPs and cellular viability was evaluated using. Neutral Red Uptake (NRU) assay. In parallel to NPs, toxicity of soluble salts of respective metals was analyzed, to reveal the possible cellular effects of metal ions shedding from the NPs. The potency of MeOx to produce reactive oxygen species was evaluated in the cell-free assay. The used three cell lines showed comparable toxicity responses to NPs and their metal ion counterparts in the current test setting. Six MeOx NPs (Al2O3, Fe3O4, MgO, SiO2, TiO2, WO3) did not show toxic effects below 100 µg/mL. For five MeOx NPs, the averaged 24 h IC50 values for the three mammalian cell lines were 16.4 µg/mL for CuO, 22.4 µg/mL for ZnO, 57.3 µg/mL for Sb2O3, 132.3 µg/mL for Mn3O4 and 129 µg/mL for Co3O4. Comparison of the dissolution level of MeOx and the toxicity of soluble salts allowed to conclude that the toxicity of CuO, ZnO and Sb2O3 NPs was driven by release of metal ions. The toxic effects of Mn3O4 and Co3O4 could be attributed to the ROS-inducing ability of these NPs. All the NPs were internalized by the cells according to light microscopy studies but also proven by TEM, and internalization of Co3O4 NPs seemed to be most prominent in this aspect. In conclusion, this work provides valuable toxicological data for a library of 11 MeOx NPs. Combining the knowledge on toxic or non-toxic nature of nanomaterials may be used for safe-by-design approach.
Publisher: American Society for Microbiology
Date: 15-04-2008
DOI: 10.1128/JB.01494-07
Abstract: According to in silico analysis, the genome of Pseudomonas putida KT2440 encodes at least four Zn/Cd/Pb efflux transporters—two P-type ATPases (CadA1 and CadA2) and two czc chemiosmotic transporters (CzcCBA1 and CzcCBA2). In this study we showed that all these transporters are functional, but under laboratory conditions only two of them were involved in the mediation of heavy metal resistance in P. putida KT2440. CadA2 conferred Cd 2+ and Pb 2+ resistance, whereas CzcCBA1 was involved in export of Zn 2+ , Cd 2+ , and possibly Pb 2+ . CadA1, although nonfunctional in P. putida , improved Zn 2+ resistance and slightly improved Cd 2+ resistance when it was expressed in Escherichia coli . CzcCBA2 contributed to Zn resistance of a czcA1 -defective P. putida strain or when the CzcA2 subunit was overexpressed in a transporter-deficient strain. It seemed that CzcA2 could complex with CzcC1 and CzcB1 subunits and therefore complement the loss of CzcA1. The CzcCBA2 transporter itself, however, did not function. Expression of cadA1 , cadA2 , and czcCBA1 was induced by heavy metals, and the expression levels were dependent on the growth medium and growth phase. Expression of cadA2 and czcCBA1 was nonspecific both genes were induced by Zn 2+ , Cd 2+ , Pb 2+ , Ni 2+ , Co 2+ , and Hg 2+ . On the other hand, remarkably, expression of cadA1 was induced only by Zn 2+ . Possible roles of distinct but simultaneously functioning transporters are discussed.
Publisher: Elsevier BV
Date: 09-2009
DOI: 10.1016/J.TIV.2009.05.015
Abstract: The aim of this study was to evaluate the toxic effect of nanosized ZnO, CuO and TiO(2) to Saccharomyces cerevisiae - a widely used unicellular eukaryotic model organisms in molecular and cell biology. The effect of metal oxide nanoparticles, their bulk forms and respective ionic forms were compared. The bioavailable Zn(2+) and Cu(2+) ions in the growth medium were quantified by recombinant microbial sensors. Nano and bulk TiO(2) were not toxic even at 20000 mg/l. Both, nano and bulk ZnO were of comparable toxicity (8-h EC(50) 121-134 mg ZnO/l and 24-h EC(50) 131-158 mg/l). The toxicity was explained by soluble Zn-ions as proved by the microbial sensor. However, nano CuO was about 60-fold more toxic than bulk CuO: 8-h EC(50) were 20.7 and 1297 mg CuO/l and 24-h EC(50) were 13.4 and 873 mg/l, respectively. The increase in toxicity of both CuO formulations at 24th hour of growth was due to the increased dissolution of copper ions from CuO over time. Comparison of EC(50) values of nano CuO, bulk CuO and Cu(2+) with bioavailable copper concentrations in the growth medium showed that the solubilized Cu-ions explained only about 50% of the toxicity of both, nano and bulk CuO. To our knowledge, this is the first study that evaluates the toxicity of ZnO, CuO and TiO(2) nanoparticles to S.cerevisiae.
Publisher: MDPI AG
Date: 03-11-2011
DOI: 10.3390/S111110502
Publisher: Springer Science and Business Media LLC
Date: 24-04-2019
DOI: 10.1038/S41598-019-42906-3
Abstract: Combining membrane impermeable DNA-binding stain propidium iodide (PI) with membrane-permeable DNA-binding counterstains is a widely used approach for bacterial viability staining. In this paper we show that PI staining of adherent cells in biofilms may significantly underestimate bacterial viability due to the presence of extracellular nucleic acids (eNA). We demonstrate that gram-positive Staphylococcus epidermidis and gram-negative Escherichia coli 24-hour initial biofilms on glass consist of 76 and 96% PI-positive red cells in situ , respectively, even though 68% the cells of either species in these aggregates are metabolically active. Furthermore, 82% of E. coli and 89% S. epidermidis are cultivable after harvesting. Confocal laser scanning microscopy (CLSM) revealed that this false dead layer of red cells is due to a subpopulation of double-stained cells that have green interiors under red coating layer which hints at eNA being stained outside intact membranes. Therefore, viability staining results of adherent cells should always be validated by an alternative method for estimating viability, preferably by cultivation.
Publisher: MDPI AG
Date: 04-11-2008
DOI: 10.3390/S8116899
Publisher: Public Library of Science (PLoS)
Date: 30-05-2013
Publisher: Elsevier BV
Date: 10-2008
Publisher: Elsevier BV
Date: 08-2011
Publisher: MDPI AG
Date: 11-08-2011
DOI: 10.3390/S110807865
Publisher: Wiley
Date: 06-2017
Abstract: There is a pressing need to develop more effective therapeutics to fight cancer. An idyllic chemotherapeutic is expected to overcome drug resistance of tumors and minimize harmful side effects to healthy tissues. Antibody-functionalized porous silicon nanoparticles loaded with a combination of chemotherapy drug and gold nanoclusters (AuNCs) are developed. These nanocarriers are observed to selectively deliver both payloads, the chemotherapy drug and AuNCs, to human B cells. The accumulation of AuNCs to target cells and subsequent exposure to an external electromagnetic field in the microwave region render them more susceptible to the codelivered drug. This approach represents a targeted two-stage delivery nanocarrier that benefits from a dual therapeutic action that results in enhanced cytotoxicity.
Publisher: Elsevier BV
Date: 10-2002
Publisher: Springer Science and Business Media LLC
Date: 2009
Publisher: Elsevier BV
Date: 09-2018
DOI: 10.1016/J.COLSURFB.2018.05.009
Abstract: Application of efficient antimicrobial surfaces has been estimated to decrease both, the healthcare-associated infections and the spread of antibiotic-resistant bacteria. In this paper, we prepared ZnO and ZnO/Ag nanoparticle covered surfaces and evaluated their antimicrobial efficacy towards a Gram-negative bacterial model (Escherichia coli), a Gram-positive bacterial model (Staphylococcus aureus) and a fungal model (Candida albicans) in the dark and under UVA illumination. The surfaces were prepared by spin coating aliquots of ZnO and ZnO/Ag nanoparticle suspensions onto glass substrates. Surfaces contained 2 or 20 μg Zn/cm
Publisher: Elsevier BV
Date: 12-2022
DOI: 10.1016/J.CHEMOSPHERE.2022.136599
Abstract: Lack of microplastics (MP) toxicity studies involving environmentally relevant concentrations and exposure times is concerning. Here we analyzed the potential adverse effects of low density polyethylene (LDPE) MP at environmentally relevant concentration in sub-chronic exposure to two hipods Gmelinoides fasciatus and Gammarus lacustris, species that naturally compete with each other for their habitats. 14-day exposure to 2 μg/L (8 particles/L corresponding to low exposure) and 2 mg/L (∼8400 particles/L, corresponding to high exposure) of 53-100 μm LDPE MP were used to assess ingestion and egestion of MP, evaluate its effects on hipod mortality, swimming ability and oxidative stress level. Both hipod species were effectively ingesting and egesting LDPE MP. On the average, 0.8 and 2.5 MP particles were identified in the intestines of each hipod exposed to 2 μg/L and 2 mg/L LDPE MP, respectively. Therefore, intestinal MP after 14-day exposure did not fully reflect the differences in LDPE MP exposure concentrations. Increased mortality of both hipods was observed at 2 mg/L LDPE MP and in case of G. lacustris also at 2 μg/L exposure. The effect of LDPE on swimming activity was observed only in case of G. fasciatus. Oxidative stress marker enzymes SOD, GPx and reduced glutathione GSH varied according to hipod species and LDPE MP concentration. In general G. lacustris was more sensitive towards LDPE MP induced oxidative stress. Overall, the results suggested that in MP polluted environments, G. lacustris may lose its already naturally low competitiveness and become overcompeted by other more resistant species. The fact that in the sub-chronic foodborne exposure to environmentally relevant and higher LDPE MP concentrations all the observed toxicological endpoints were affected refers to the potential of MP to affect and disrupt aquatic communities in the longer perspective.
Publisher: American Chemical Society (ACS)
Date: 13-07-2015
Publisher: American Chemical Society (ACS)
Date: 07-01-2015
DOI: 10.1021/ES504259S
Abstract: Metal oxide nanoparticles (MOx NPs) are used for a host of applications, such as electronics, cosmetics, construction, and medicine, and as a result, the safety of these materials to humans and the environment is of considerable interest. A prior study of 24 MOx NPs in mammalian cells revealed that some of these materials show hazard potential. Here, we report the growth inhibitory effects of the same series of MOx NPs in the bacterium Escherichia coli and show that toxicity trends observed in E. coli parallel those seen previously in mammalian cells. Of the 24 materials studied, only ZnO, CuO, CoO, Mn2O3, Co3O4, Ni2O3, and Cr2O3 were found to exert significant growth inhibitory effects these effects were found to relate to membrane damage and oxidative stress responses in minimal trophic media. A correlation of the toxicological data with physicochemical parameters of MOx NPs revealed that the probability of a MOx NP being toxic increases as the hydration enthalpy becomes less negative and as the conduction band energy approaches those of biological molecules. These observations are consistent with prior results observed in mammalian cells, revealing that mechanisms of toxicity of MOx NPs are consistent across two very different taxa. These results suggest that studying nanotoxicity in E. coli may help to predict toxicity patterns in higher organisms.
Publisher: Informa UK Limited
Date: 15-10-2015
DOI: 10.3109/17435390.2015.1084059
Abstract: Here, we evaluate the extent of sorption of silver nanoparticles (AgNPs) with different primary sizes (30 and 70 nm) and surface properties (branched polyethylene imine, "bPEI" and citrate coating) to laboratory plastic during (eco)toxicological testing. Under conditions of algal growth inhibition assay, up to 97% of the added AgNPs were sorbed onto the test vessels whereas under conditions of in vitro toxicological assay with mammalian cells, the maximum loss of AgNPs was 15%. We propose that the high concentration of proteins and biomolecules in the in vitro toxicological assay originating from serum-containing cell culture medium prevented NP sorption due to steric stabilisation. The sorption of AgNPs to test vessels was clearly concentration dependent. In the conditions of algal growth inhibition assay at 10 ng AgNPs/mL, up to 97% of AgNPs were lost from the test while at higher concentrations (1000 ng AgNPs/mL), the loss of AgNPs was remarkably smaller, up to 64%. Sorption of positively charged bPEI-coated AgNPs was more extensive than the sorption of negatively charged citrate-coated AgNPs and, when calculated on a mass basis, more 70 nm-sized Ag than 30 nm Ag sorbed to plastic surfaces. In summary, this study demonstrates that the loss of AgNPs during (eco)toxicological tests due to sorption on test vessel surfaces is significant, especially in diluted media (e.g. in algal growth medium) and at low NP concentrations. Thus, to ensure the accurate interpretation of (eco)toxicological results, the loss of AgNPs due to adsorption to test vessels should not be overlooked and considered for each specific case.
Publisher: Elsevier BV
Date: 10-2008
Publisher: Elsevier BV
Date: 10-2012
DOI: 10.1016/J.ENVPOL.2012.05.009
Abstract: The sub-toxic effects of CuO nanoparticles (nano-CuO) were evaluated using three recombinant luminescent Escherichia coli bacteria responding specifically to (i) reactive oxygen species (ROS), (ii) single-stranded DNA breaks and (iii) bioavailable Cu ions. Using these sensors we showed that nano-CuO induces the formation of superoxide anions, hydrogen peroxide and single-stranded DNA already at very low sub-toxic levels (0.1 mg Cu/L). The maximal sub-toxic response of all biosensors to nominal concentrations of nano-CuO, micro-CuO (size control) and CuSO(4) (solubility control) occurred at ~6, ~600 and ~0.6 mg Cu/L, respectively. According to the chemical analysis all the latter concentrations yielded ~0.6 mg of soluble Cu/L, indicating that dissolution of CuO particles was the key factor triggering the ROS and DNA damage responses in bacteria. Cu-ions chelation studies also showed that CuO particles were not involved in these stress responses. The solubilization results were confirmed by Pseudomonas fluorescens Cu-ion sensor.
No related grants have been discovered for Angela Ivask.