TiO2 nanoparticles in the marine environment: impact on the toxicity of tributyltin to abalone (Haliotis diversicolor supertexta) embryos

Titanium dioxide nanoparticles modulate the toxicological response to cadmium in the gills of Mytilus galloprovincialis

We investigated the influence of titanium dioxide nanoparticles (nano-TiO2) on the response to cadmium in the gills of the marine mussel Mytilus galloprovincialis in terms of accumulation and toxicity. Mussels were in vivo exposed to nano-TiO2, CdCl2, alone and in combination. Several cellular biomarkers were investigated in gills: ABC transport proteins and metallothioneins at gene/protein (abcb1, abcc-like and mt-20) and functional level, GST activity, NO production and DNA damage (Comet assay). Accumulation of total Cd and titanium in gills as in whole soft tissue was also investigated. Significant responses to Cd exposure were observed in mussel gills as up-regulation of abcb1 and mt-20 gene transcription, increases in total MT content, P-gp efflux and GST activity, DNA damage and NO production. Nano-TiO2 alone increased P-gp efflux activity and NO production. When combined with Cd, nano-TiO2 reduced the metal-induced effects by significantly lowering abcb1 gene transcription, GST activity, and DNA damage, whereas, additive effects were observed on NO production. A lower concentration of Cd was observed in the gills upon co-exposure, whereas, Ti levels were unaffected. A competitive effect in uptake/accumulation of nano-TiO2 and Cd seems to occur in gills. A confirmation is given by the observed absence of adsorption of Cd onto nano-TiO2 in sea water media.

Genomic and chromosomal damage in the marine mussel Mytilus galloprovincialis: Effects of the combined exposure to titanium dioxide nanoparticles and cadmium chloride

Titanium dioxide nanoparticles (TiO2-NPs) continuously released into waters, may cause harmful effects to marine organisms and their potential interaction with conventional toxic contaminants represents a growing concern for biota. We investigated the genotoxic potential of nanosized titanium dioxide (n-TiO2) (100 μg L(-1)) alone and in combination with CdCl2 (100 μg L(-1)) in Mytilus galloprovincialis after 4 days of in vivo exposure. RAPD-PCR technique and Micronucleus test were used to study genotoxicity. The results showed genome template stability (GTS) being markedly reduced after single exposure to n-TiO2 and CdCl2. Otherwise, co-exposure resulted in a milder reduction of GTS. Exposure to n-TiO2 was responsible for a significant increase of micronucleated cell frequency in gill tissue, while no chromosomal damage was observed after CdCl2 exposure as well as after combined exposure to both substances.

Transport of TiO2 nanoparticles in soil in the presence of surfactants

This paper aimed to investigate the influences of surfactants on the nanoparticle transport behavior in soil. The transport behaviors of TiO2 nanoparticles (nTiO2) in soil with three different surfactants, including Triton X-100 (TX-100), sodium dodecylbenzene sulfonate (SDBS) and cationic cetyl trimethylammonium bromide (CTAB) were studied. Results showed that all the three surfactants decreased the mobility of nTiO2 in soil column, which were mainly caused by the strong adsorption of surfactants on soil and nTiO2. The inhibition order was as follows: CTAB>SDBS>TX-100. Combined effect experiments showed that when solution ionic strength (IS) increased, TX-100 or CTAB inhibited the mobility of nTiO2 in soil. However, the effect of SDBS on nTiO2 transport shifted from inhibition to facilitation when IS increased from 0.1 to 5mM. This was mainly attributed to the decreasing adsorption of SDBS on soil with increased IS, whereas the adsorption of TX-100 and CTAB was independent of IS. This innovative information motivates further insight into the role of surfactants on nanoparticle transport behavior in soil.

NanoE-Tox: New and in-depth database concerning ecotoxicity of nanomaterials

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 1. The database is based on existing literature on ecotoxicology of eight ENMs with different chemical composition: carbon nanotubes (CNTs), fullerenes, silver (Ag), titanium dioxide (TiO2), zinc oxide (ZnO), cerium dioxide (CeO2), copper oxide (CuO), and iron oxide (FeO x ; Fe2O3, Fe3O4). Altogether, NanoE-Tox database consolidates data from 224 articles and lists altogether 1,518 toxicity values (EC50/LC50/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 TiO2 (22%), CeO2 (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 > CeO2 > CNTs > TiO2 > 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.

Effects of the interaction between TiO2 with different percentages of exposed {001} facets and Cu(2+) on biotoxicity in Daphnia magna

Anatase TiO₂ nanosheets (NSs) with exposed {001} facets have been widely used because of their high activity and particular surface atomic configuration. However, investigations on their biotoxicity are rare. In this study, bioaccumulation of five different TiO₂ (with 10%, 61%, 71%, 74% and 78% exposed {001} facets), as well as copper and enzyme activities in Daphnia magna, are systematically investigated and rationalized. The results indicated that the addition of Cu²⁺ enhanced agglomeration–sedimentation of TiO₂, resulting in the reduction of TiO₂ bioaccumulation by 10% to 26%. TiO₂ nanoparticles (NPs) increased copper bioaccumulation by 9.8%, whereas the other four TiO₂ nanosheets (NSs) decreased it by 43% to 53%, which depended on TiO₂ variant adsorption and free Cu²⁺ concentrations in the supernatant. The levels of superoxide dismutase (SOD) enzyme and Na⁺/K⁺-ATPase activities suggested that oxidative stress, instead of membrane damage, was the main toxicity in D. magna. Meanwhile, the SOD enzyme activities increased with decreasing Cu accumulation and increasing Ti accumulation because of the different functions of Cu and Ti in organisms. This research highlighted the important role of the percentage of exposed {001} facets in nanostructured TiO₂ on bioaccumulation and biotoxicity of TiO₂ and Cu²⁺ in Daphnia magna.

Toxicity of solid residues resulting from wastewater treatment with nanomaterials

Nanomaterials (NMs) are widely recommended for wastewater treatments due to their unique properties. Several studies report the different advantages of nanotechnology in the remediation of wastewaters, but limited research has been directed toward the fate and potential impacts of the solid residues (SRs) produced after the application of such technologies. The present work aimed at investigating the ecotoxicity of SRs resulting from the treatment of three effluents (OOMW, kraft pulp mill, and mining drainage) with two NMs (TiO2 and Fe2O3). The invertebrate Chironomus riparius was selected as test organism and exposed to the residues. The effect on percentage of survival and growth was assessed. Results showed that the SRs from the treatments nano-TiO2(1.0gL(-1))/H2O2(0.5M) and nano-Fe2O3(1.0gL(-1))/H2O2(1.0M) from OOMW and nano-Fe2O3(0.75gL(-1))/H2O2(0.01M) from kraft pulp mill effluent exhibited lethal toxicity to C. riparius. Only the exposure to SRs resulting from the treatment with nano-Fe2O3(0.75gL(-1))/H2O2(0.01M) applied to the kraft pulp mill effluent significantly affected the growth rate based on the head capsule width. In terms of growth rate, based on the body length, it decreased significantly after exposure to the SRs from the treatments nano-TiO2 (1.0gL(-1)) and nano-Fe2O3(0.75gL(-1))/H2O2(0.01M) of kraft paper mill effluent and nano-Fe2O3(1.0gL(-1))/H2O2(1.0M) of OOMW. According to our study the SRs can promote negative effects on C. riparius. However, the effects are dependent on the type of effluent treated as well as on the organic and inorganic compounds attached to the NMs.

The impact of TiO2 nanoparticles on uptake and toxicity of benzo(a)pyrene in the blue mussel (Mytilus edulis)

Nanoparticles are emerging contaminants of concern. Knowledge on their environmental impacts is scarce, especially on their interactive effects with other contaminants. In this study we investigated effects of titanium dioxide nanoparticles (TiO2NP) on the blue mussel (Mytilus edulis) and determined their influence on the bioavailability and toxicity of benzo(a)pyrene (B(a)P), a carcinogenic polyaromatic hydrocarbon (PAH). Blue mussels were exposed to either TiO2NP (0.2 and 2.0 mg L(-1)) or B(a)P (20 μg L(-1)) and to the respective combinations of these two compounds. Aqueous contaminant concentrations, the uptake of Ti and B(a)P into mussel soft tissue, effects on oxidative stress and chromosomal damage were analyzed. The uncoated TiO2NP agglomerated rapidly in the seawater. The presence of TiO2NP significantly reduced the bioavailability of B(a)P, shown by lowered B(a)P concentrations in exposure tanks and in mussel tissue. The activities of antioxidant enzyme superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were impacted by the various exposure regimes, indicating oxidative stress in the contaminant exposure groups. While SOD activity was increased only in the 0.2TiO2NP exposure group, CAT activity was enhanced in both combined exposure groups. The GPx activity was increased only in the groups exposed to the two single compounds. In hemocytes, increased chromosomal damage was detected in mussels exposed to the single compounds, which was further increased after exposure to the combination of compounds. In this study we show that the presence of TiO2NP in the exposure system reduced B(a)P uptake in blue mussels. However, since most biomarker responses did not decrease despite of the lower B(a)P uptake in combined exposures, the results suggest that TiO2NP can act as additional stressor, or potentially alters B(a)P toxicity by activation.

Effect of 17β-estradiol on stability and mobility of TiO2 rutile nanoparticles

Contaminants including titanium dioxide nanoparticles (n-TiO2), as well as organic wastewater contaminants (OWCs), have been detected in wastewater treatment plant effluents, however, no information is yet available on how OWCs may modify the surface properties of TiO2 nanoparticles, or influence their stability in water and subsequent mobility in porous media. In this study, 17β-estradiol (E2) was chosen as a representative OWC to investigate the interaction between OWCs and n-TiO2. Batch and kinetic sorption experiments and Fourier Transform Infrared (FTIR) Spectrometer measurements confirmed that E2 was quickly sorbed onto the surface of n-TiO2 aggregates in water. Aggregation experiments showed that the presence of E2 has a minor influence on the size of n-TiO2 aggregates under lower ionic strength conditions at natural pH. In high ionic strength solution, the presence of E2 led to an increased average hydrodynamic diameter and a wider distribution of n-TiO2 aggregate sizes. Interaction energy analyses indicated that steric repulsion likely contributed to the stability of the n-TiO2 suspension in the presence of E2. Mobility analysis based on the clean bed filtration theory indicated that the impact of E2 on the mobility of n-TiO2 in porous media is minimal in comparison to the influence of solution ionic strength.

Interaction of TiO2 nanoparticles with the marine microalga Nitzschia closterium: growth inhibition, oxidative stress and internalization

The toxicity of TiO2 engineered nanoparticles (NPs) to the marine microalga Nitzschia closterium was investigated by examining growth inhibition, oxidative stress and uptake. The results indicated that the toxicity of TiO2 particles to algal cells significantly increased with decreasing nominal particle size, which was evidenced by the 96 EC50 values of 88.78, 118.80 and 179.05 mg/L for 21 nm, 60 nm and 400 nm TiO2 particles, respectively. The growth rate was significantly inhibited when the alga was exposed to 5mg/L TiO2 NPs (21 nm). Measurements of antioxidant enzyme activities showed that superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities were first induced and subsequently inhibited following exposure to 5mg/L TiO2 NPs. The depletion of antioxidant enzymes with a concomitant increase in malondialdehyde (MDA) levels and reactive oxygen species (ROS) posed a hazard to membrane integrity. A combination of flow cytometry analysis, transmission electron microscopy and Ti content measurement indicated that TiO2 NPs were internalized in N. closterium cells. The level of extracellular ROS, which was induced by TiO2 NPs under visible light, was negligible when compared with the intracellular ROS level (accounting for less than 6.0% of the total ROS level). These findings suggest that elevated TiO2 nanotoxicity in marine environments is related to increased ROS levels caused by internalization of TiO2 NPs.

Bioaccumulation and biotransformation of polybrominated diphenyl ethers in the marine bivalve (Scapharca subcrenata): influence of titanium dioxide nanoparticles

Titanium dioxide nanoparticles (nTiO2) have the potential to adsorb co-existing contaminants in aqueous environment to form nanoparticle-contaminant complexes. Adsorption by nTiO2 might impact the fate of contaminants in water. Bioaccumulation experiments were conducted to compare the accumulation of polybrominated diphenyl ethers (PBDEs) in marine bivalve (Scapharca subcrenata) exposed to PBDEs in the presence and absence of nTiO2. PBDEs can be taken up by S. subcrenata through aqueous exposure. nTiO2 acts as a carrier and can enhance the ingestion of PBDEs, but the bioaccumulation of PBDEs was not facilitated significantly in the presence of nTiO2. Similar accumulation kinetics pattern was found after exposing to PBDEs in the presence and absence of nTiO2. Further analysis showed that no significant difference between the congener profiles of PBDEs in the presence and absence of nTiO2, suggesting that nTiO2 would not influence the biotransformation of PBDEs in clams.

Inorganic nano-adsorbents for the removal of heavy metals and arsenic: a review

Schematic of inorganic adsorbents (INA) for heavy metal removal.

Influence of titanium dioxide nanoparticles on 2,3,7,8-tetrachlorodibenzo-p-dioxin bioconcentration and toxicity in the marine fish European sea bass (Dicentrarchus labrax)

The present study investigated the influence of nano-TiO(2) (1 mg L(-1)) on 2,3,7,8-tetrachlorodibenzo-p-dioxin(2,3,7,8-TCDD) (46 pg L(-1)) bioconcentration and toxicity in the European sea bass (Dicentrarchus labrax) during 7 days in vivo exposure. A multimarkers approach was applied in different organs: detoxification in liver; innate immunity and pro-inflammatory response and adaptive immunity in gills and spleen; genotoxicity in peripheral erythrocytes and muscle. Bioconcentration of 2,3,7,8-TCDD in presence of nano-TiO2 was investigated in liver, skin and muscle as well as interaction between nano-TiO2 and organic pollutants in artificial sea water (ASW). Nano-TiO2 negatively influenced immune response induced by 2,3,7,8-TCDD in spleen but not in gills and reduced the DNA damage induced by 2,3,7,8-TCDD in erythrocytes. nano-TiO2 did not interfere with 2,3,7,8-TCDD detoxification and bioconcentration according to the observed no interaction of the nano-TiO2 with organic pollutants in ASW.

Effect of titanium dioxide nanoparticles on the bioavailability, metabolism, and toxicity of pentachlorophenol in zebrafish larvae

This study investigated the influence of titanium dioxide nanoparticles (n-TiO2) on the bioavailability, metabolism, and toxicity of pentachlorophenol (PCP) in fish. Zebrafish (Danio rerio) embryos or larvae (2-h post-fertilization) were exposed to PCP (0, 3, 10, and 30 μg/L) alone or in combination with n-TiO2 (0.1mg/L) until 6 days post-fertilization. Results showed that n-TiO2 treatment alone did not induce lipid peroxidation, DNA damage, as well as the generation of reactive oxygen species (ROS) in the larvae. As compared with PCP treatment, the co-exposure of PCP and n-TiO2 enhanced the induction of ROS generation, eventually leading to lipid peroxidation and DNA damage. The nuclear factor erythroid 2-related factor 2 gene transcriptions were significantly upregulated in both PCP treatment alone and in combination with n-TiO2. Chemical analysis and histological examination showed that n-TiO2 adsorb PCP, and n-TiO2 are taken up by developing zebrafish larvae; however, PCP content was not enhanced in the presence of n-TiO2, but the metabolism of PCP to tetrachlorohydroquinone was enhanced in larvae. The results indicate that n-TiO2 enhanced the metabolism of PCP and caused oxidative damage and developmental toxicity, suggesting that NPs can influence the fate and toxicity of associated organic pollutants in the aquatic environment.

Titanium dioxide nanoparticles as carrier facilitate bioaccumulation of phenanthrene in marine bivalve, ark shell (Scapharca subcrenata)

To evaluate the impact of titanium dioxide nanoparticles (nTiO2) on the uptake of hydrophobic organic chemicals by marine bivalves, we conducted a comparative bioaccumulation study by exposing clam, Scapharca subcrenata, to phenanthrene (Phe) in the presence and absence of nTiO2. The large surface area of nTiO2 resulted in adsorption of co-existing Phe in aqueous solution to form nTiO2-Phe complexes. Accumulation of nTiO2 was not observed in clams at exposed concentration (500 μg/L) in this study. However, enhanced uptake of Phe by clams was observed in the presence of nTiO2, with ku and BAFs values being 2 and 1.7 times higher than that of Phe alone, respectively. The enhanced uptake can be explained by ingestion of nTiO2-Phe complexes into the gut and subsequent desorption of Phe there. Therefore, nTiO2 as a carrier facilitated the uptake of Phe by marine bivalves.

Interactive effects of n-TiO2 and 2,3,7,8-TCDD on the marine bivalve Mytilus galloprovincialis

Despite the growing concern over the potential biological impact of nanoparticles (NPs) in the aquatic environment, little is known about their interactions with other pollutants. The bivalve Mytilus sp, largely utilized as a sentinel for marine contamination, has been shown to represent a significant target for different types of NP, including n-TiO2, one of the most widespread in use. In this work, the possible interactive effects of n-TiO2 and 2,3,7,8-TCDD, chosen as models of NP and organic contaminant, respectively, were investigated in Mytilus galloprovincialis. In vitro experiments with n-TiO2 and TCDD, alone and in combination, were carried out in different conditions (concentrations and times of exposure), depending on the target (hemocytes, gill cells and biopsies) and the endpoint measured. Mussels were also exposed in vivo to n-TiO2 (100 μg L(-1)) or to TCDD (0.25 μg L(-1)), alone and in combination, for 96 h. A wide range of biomarkers, from molecular to tissue level, were measured: lysosomal membrane stability and phagocytosis in hemocytes, ATP-binding cassette efflux transporters in gills (gene transcription and efflux activity), several biomarkers of genotoxicity in gill and digestive cells (DNA damage, random amplified polymorphic DNA-RAPD changes), lysosomal biomarkers and transcription of selected genes in the digestive gland. The results demonstrate that n-TiO2 and TCDD can exert synergistic or antagonistic effects, depending on experimental condition, cell/tissue and type of measured response. Some of these interactions may result from a significant increase in TCDD accumulation in whole mussel organisms in the presence of n-TiO2, indicating a Trojan horse effect. The results represent the most extensive data obtained so far on the sub-lethal effects of NPs and organic contaminants in aquatic organisms. Moreover, these data extend the knowledge on the molecular and cellular targets of NPs in bivalves.

Toxicity of different-sized copper nano- and submicron particles and their shed copper ions to zebrafish embryos

Three sizes of copper nanoparticles (Cu NPs; 25 nm, 50 nm, and 100 nm), 1 submicron-sized particle, and Cu(NO3 )2 were added to the culture buffer of zebrafish embryos from 24 h postfertilization to 120 h postfertilization. In suspensions of Cu NPs and the Cu submicron-sized particle, the main contribution to the toxicity to zebrafish embryos was from the particle form of Cu particles (Cu NPparticle , >71%) rather than from dissolved Cu from the Cu particles (Cu NPion ). All particles tested as well as copper nitrate inhibited hatching, altered behavioral responses, and increased the incidence of malformations. Different kinds of abnormalities were observed in the morphology and behavior of the zebrafish embryos, depending on the particle size of the Cu suspensions tested. The median lethal concentrations of Cu NPparticle (25 nm, 50 nm, and 100 nm), the submicron-sized particle, and copper nitrate were 0.58 mg/L, 1.65 mg/L, 1.90 mg/L, 0.35 mg/L, and 0.70 mg/L, respectively. Submicron-sized particles and copper nitrate were more toxic than Cu NPs, and smaller Cu NPs were more toxic than larger Cu NPs. Dissolution of Cu NPs and the subsequent ion toxicity was not the primary mechanism of Cu NP toxicity in zebrafish embryos.

Effects of the interaction of single-walled carbon nanotubes with 4-nonylphenol on their in vitro toxicity

The aim of this study was to assess the toxicological risks arising from the coexistence of polyethylene glycol coated single-walled carbon nanotubes (SWCNTs-PEG) and a known environmental contaminant: 4-nonylphenol (NP). To this end, in vitro toxicity assays involving the exposure of 3T3-L1 cells (mouse embryonic fibroblasts) to SWCNTs-PEG alone or in combination with NP for 24 or 48 h were performed. Experimental treatments were conducted in both presence (10%) and absence of serum in order to evaluate its influence on the toxicity of SWCNTs-PEG. Although the results provided no unambiguous evidences of synergistic toxicity between SWCNTs-PEG and NP, some specific treatments with mixtures (SWCNTs-PEG+NP) resulted in an unexpected combined toxicity in relation to the individual treatments. Only in those cases the interaction between SWCNTs-PEG and NP could have a synergistic effect on the resulting toxicity. The addition of 10% serum increased the stability of SWCNTs-PEG in the culture medium-possibly by steric repulsions-and reduced the toxicity of nanoparticles as a result. Overall, the serum had a "protective effect" on cells against all treatments: SWCNTs-PEG, NP or their mixtures (SWCNTs-PEG+NP). Raman spectroscopy allowed the intracellular distribution of SWCNTs-PEG to be elucidated.

Adsorption of tetracycline to nano-NiO: the effect of co-existing Cu(ii) ions and environmental implications

Nano-sized nickel oxide (nano-NiO) is a new nanomaterial that has shown great promise in many areas of application. Understanding its environmental fate and effects is critical for minimizing the potential environmental implications of this new material due to incidental and accidental releases in the future. In this study, we observed strong adsorption of tetracycline to nano-NiO and found that the adsorption affinity can be further enhanced by Cu(ii) ions - the observed distribution coefficient (Kd) values are 10(3.1) to 10(4.2) L kg(-1) in the absence of Cu(ii) and 10(3.0) to 10(5.5) L kg(-1) in the presence of Cu(ii); such adsorption affinities are even comparable to those of tetracycline to carbonaceous materials. The strong adsorptive affinities of nano-NiO for tetracycline are likely attributable to several mechanisms, including surface complexation, cation exchange, and electrostatic attraction. As a strong complexing agent, Cu(ii) can significantly enhance adsorption of tetracycline by serving as a bridging agent between tetracycline and nano-NiO. The findings of this study have important implications for the risk assessment of engineered nanomaterials - in aquatic environments nano-NiO (and likely other metal oxide nanomaterials) can strongly adsorb tetracycline antibiotics, resulting in the changes of environmental risks of the metal oxide nanomaterials and/or bioavailability of the adsorbed contaminants.

Ecotoxicity of engineered TiO2 nanoparticles to saltwater organisms: an overview

The innovative properties of nanomaterials make them suitable for various applications in many fields. In particular, TiO2 nanoparticles (nTiO2) are widely used in paints, in cosmetics and in sunscreens that are products accessible to the mass market. Despite the great increase in the use of such nanomaterials, there is a paucity of general information about their potential effects to the aquatic species, especially to saltwater ones. Moreover, the difficulties of determining the effective exposure scenario make the acquired information low comparable. In this work, questions about the complexity of the real exposure scenario determination are discussed. The state of the art, concerning the experimental activities with nTiO2 toward the saltwater organisms is firstly illustrated, providing statistical information about the different matrices, organisms and nanoparticles employed. A comparison of the nTiO2 ecotoxicity effects, grouped by taxonomic classes, is provided illustrating their relative experimental conditions. Findings show the need to develop specific protocols for toxicity tests with ENPs to control the variability of experimental conditions. Some advices are finally proposed for the future experimental activities.

Enhanced bioaccumulation of pentachlorophenol in carp in the presence of multi-walled carbon nanotubes

The impact of suspended particles on the bioavailability of pollutants has long been a controversial topic. In this study, adsorption of pentachlorophenol (PCP) onto a natural suspended particulate matter (SPM) and multi-walled carbon nanotubes (MWCNTs) was studied. Facilitated transports of PCP into carp by SPM and MWCNTs were evaluated by bioaccumulation tests exposing carp (Carassius auratus red var.) to PCP-contaminated water in the presence of SPM and MWCNTs, respectively. Desorption of PCP on SPM and MWCNTs in simulated digested fluids was also investigated. The results demonstrate that MWCNTs (K F = 7.99 × 10(4)) had a significantly stronger adsorption capacity for PCP than the SPM (K F = 19.0). The presence of SPM and MWCNTs both improved PCP accumulation in the carp during the 21 days of exposure, and the 21 days PCP concentration in the carp was enhanced by 25.9 and 12.8 % than that without particles, respectively. The enhancement in bioaccumulation by MWCNTs was less than that by the SPM. Considerably more PCP was accumulated in the viscera of the fish (BCF = 519495 for SPM and 148955 for MWCNTs), and the difference in PCP concentrations between different tissues became greater with particles. PCP desorption in the simulated digestive fluids was faster than that in the background solution. Compared to MWCNTs-bound PCP, more SPM-bound PCP was desorbed, and K F of desorption for SPM was at least 4 orders of magnitude higher than that for MWCNTs, which can explain the greater enhancement in bioaccumulation in the presence of SPM. Particle-bound pollutants might pose more risk than pollutants alone.

Cell rescue by nanosequestration: reduced cytotoxicity of an environmental remediation residue, Mg(OH)2 nanoflake/Cr(VI) adduct

Some nanomaterials, such as Mg(OH)2 nanoflakes, are heavily used in pollutant adsorption and removal. Residues from these environmental remediations are potential hazardous materials. Safety evaluations of these materials are needed for environmental protection and human health. Although nanotoxicity has been widely investigated in recent years, research on the toxicity of nanoparticle/pollutant adducts has been rather inadequate. Here, we report the cellular perturbations and cytotoxicity of nano-Mg(OH)2/Cr(VI) adducts as a case study to elucidate how nanoparticle/pollutant adducts impact human cells. We found that Mg(OH)2 nanoflakes barely enter cells, while desorbed Cr(VI) anions enter cells, generate ROS, induce cell apoptosis, and cause cytotoxicity. This cytotoxicity is only a fraction of the cytotoxicity of free Cr(VI) because nano-Mg(OH)2 particles are able to retain more than half of their Cr(VI) anions.

Embryotoxicity of TiO2 nanoparticles to Mytilus galloprovincialis (Lmk)

Few data exist on the ecotoxicological effects of nanosized titanium dioxide (nTiO2) towards marine species with specific reference to bivalve molluscs and their relative life stages. Mytilus galloprovincialis Lamarck was selected to assess the potential adverse effects of nTiO2 (0-64 mg/L) on its early larval development stages (pre-D shell stage, malformed D-shell stage and normal D-shell stage larvae) considering two exposure scenarios characterised by total darkness (ASTM protocol) and natural photoperiod (light/dark). This approach was considered to check the presence of potential effects associated to the photocatalytic properties of nTiO2. Parallel experiments were carried on with the bulk reference TiCl4. The toxicity of nTiO2 showed to be mainly related to its "nano" condition and to be influenced by the exposure to light that supported the increase in the number of pre-D shell stage (retarded) larvae compared to the malformed ones especially at the maximum effect concentrations (4 and 8 mg nTiO2/L). The non-linear regression toxicity data analysis showed the presence of two EC50 values per exposure scenario: a) EC(50)1 = 1.23 mg/L (0.00-4.15 mg/L) and EC(50)2 = 38.56 mg/L (35.64-41.47 mg/L) for the dark exposure conditions; b) EC(50)1 = 1.65 mg/L (0.00-4.74 mg/L) and EC(50)2 = 16.39 mg/L (13.31-19.48 mg/L) for the light/dark exposure conditions. The potential implication of agglomeration and sedimentation phenomena on ecotoxicological data was discussed.

Acute Toxicities of Penta-BDE in TiO2 Nanoparticle Suspensions to Daphnia magna

The ecotoxicity of penta-BDE in nanosized TiO2 (nTiO2) water suspensions was examined using a method developed based on the standard OECD Guidelines for the Testing of Chemicals ( i . e . OECD 202). The water flea (Daphnia magna) were used as the testing organisms. The results showed that penta-BDE alone has no acute toxicities to the testing organisms, but exhibited acute toxicities in nTiO2 water suspensions. The 72 h NOEC of penta-BDE with 1 mg L-1 nTiO2 to D. magna was calculated as less than 0.1 μg L-1 , and the 72 h EC50 and LC50 are 50.2 μg L-1 (95% CI: 0.872.45) and 100.2 μg L-1(95% CI: 1.222.86), respectively. The toxicity results indicate that nanoparticles might pose potential environmental impact through increasing toxicities of organic pollutants. Further research on the joint ecotoxicity of nanoparticles and organic pollutants is warranted in order to minimize the adverse ecological effects and human health risk of nanotechnology development.

Evaluating legacy contaminants and emerging chemicals in marine environments using adverse outcome pathways and biological effects-directed analysis

Natural and synthetic chemicals are essential to our daily lives, food supplies, health care, industries and safe sanitation. At the same time protecting marine ecosystems and seafood resources from the adverse effects of chemical contaminants remains an important issue. Since the 1970s, monitoring of persistent, bioaccumulative and toxic (PBT) chemicals using analytical chemistry has provided important spatial and temporal trend data in three important contexts; relating to human health protection from seafood contamination, addressing threats to marine top predators and finally providing essential evidence to better protect the biodiversity of commercial and non-commercial marine species. A number of regional conventions have led to controls on certain PBT chemicals over several years (termed 'legacy contaminants'; e.g. cadmium, lindane, polycyclic aromatic hydrocarbons [PAHs] and polychlorinated biphenyls [PCBs]). Analytical chemistry plays a key role in evaluating to what extent such regulatory steps have been effective in leading to reduced emissions of these legacy contaminants into marine environments. In parallel, the application of biomarkers (e.g. DNA adducts, CYP1A-EROD, vitellogenin) and bioassays integrated with analytical chemistry has strengthened the evidence base to support an ecosystem approach to manage marine pollution problems. In recent years, however,the increased sensitivity of analytical chemistry, toxicity alerts and wider environmental awareness has led to a focus on emerging chemical contaminants (defined as chemicals that have been detected in the environment, but which are currently not included in regulatory monitoring programmes and whose fate and biological impacts are poorly understood). It is also known that natural chemicals (e.g. algal biotoxins) may also pose a threat to marine species and seafood quality. Hence complex mixtures of legacy contaminants, emerging chemicals and natural biotoxins in marine ecosystems represent important scientific, economic and health challenges. In order to meet these challenges and pursue cost-effective scientific approaches that can provide evidence necessary to support policy needs (e.g. the European Marine Strategy Framework Directive), it is widely recognised that there is a need to (i) provide marine exposure assessments for priority contaminants using a range of validated models, passive samplers and biomarkers; (ii) integrate chemical monitoring data with biological effects data across spatial and temporal scales (including quality controls); and (iii) strengthen the evidence base to understand the relationship between exposure to complex chemical mixtures, biological and ecological impacts through integrated approaches and molecular data (e.g. genomics, proteomics and metabolomics). Additionally, we support the widely held view that (iv) that rather than increasing the analytical chemistry monitoring of large number of emerging contaminants, it will be important to target analytical chemistry towards key groups of chemicals of concern using effects-directed analysis. It is also important to evaluate to what extent existing biomarkers and bioassays can address various classes of emerging chemicals using the adverse outcome pathway (AOP) approach now being developed by the Organization for Economic Cooperation and Development (OECD) with respect to human toxicology and ecotoxicology.

Synergistic effects of nano-sized titanium dioxide and zinc on the photosynthetic capacity and survival of Anabaena sp

Anabaena sp. was used to examine the toxicity of exposure to a nano-TiO2 suspension, Zn2+ solution, and mixtures of nano-TiO2 and Zn2+ suspensions. Typical chlorophyll fluorescence parameters, including effective quantum yield, photosynthetic efficiency and maximal electron transport rate, were measured by a pulse-amplitude modulated fluorometer. Nano-TiO2 particles exhibited no significant toxicity at concentrations lower than 10.0 mg/L. The 96 h concentration for the 50% maximal effect (EC50) of Zn2+ alone to Anabaena sp. was 0.38 ± 0.004 mg/L. The presence of nano-TiO2 at low concentrations (<1.0 mg/L) significantly enhanced the toxicity of Zn2+ and consequently reduced the EC50 value to 0.29 ± 0.003 mg/L. However, the toxicity of the Zn2+/TiO2 system decreased with increasing nano-TiO2 concentration because of the substantial adsorption of Zn2+ by nano-TiO2. The toxicity curve of the Zn2+/TiO2 system as a function of incremental nano-TiO2 concentrations was parabolic. The toxicity significantly increased at the initial stage, reached its maximum, and then decreased with increasing nano-TiO2 concentration. Hydrodynamic sizes, concentration of nano-TiO2 and Zn2+ loaded nano-TiO2 were the main parameters for synergistic toxicity.

Risks of single-walled carbon nanotubes acting as contaminants-carriers: potential release of phenanthrene in Japanese medaka (Oryzias latipes)

The performance of carbon nanotubes (CNTs) acting as contaminants-carriers in vivo is critical for understanding the environmental risks of CNTs. In this study, the whole-body accumulation and tissue distribution of phenanthrene in Japanese medaka was examined in the presence of single-walled carbon nanotubes (SWCNTs) and the potential release of phenanthrene was investigated from two types of SWCNTs suspensions that differed in surface charge and stability. The results showed that the coexistence of SWCNTs facilitated the accumulation of phenanthrene in the digestive track of fish and therefore enhanced the whole-body phenanthrene concentration by 2.1 fold after exposure for 72 h. Meanwhile, 6.4-48 and 20-34 times higher phenanthrene concentrations were measured in the liver and brain of fish exposure to the two mixtures, respectively, when comparing with the phenanthrene alone treatment with equal concentration of soluble phenanthrene. The extra phenanthrene was from the SWCNTs-associated phenanthrene that accumulated in the digestive track indicating the release of phenanthrene from SWCNTs did occur in fish. Moreover, the neutrally charged SWCNTs showed different agglomeration behaviors from the negatively charged SWCNTs, which could affect the accumulation of SWCNTs in the digestive track of fish and subsequently influence the retention of phenanthrene associated with the carbon nanotubes.

Deposition and release kinetics of nano-TiO2 in saturated porous media: effects of solution ionic strength and surfactants

The aggregation, transport and deposition kinetics (i.e. attachment and release) of TiO(2) nanoparticles (nano-TiO(2)) were investigated as a function of ionic strength and the presence of anionic (sodium dodecylbenzene sulfonate, SDBS) and non-ionic (Triton X-100) surfactants in 100% critical micelle concentration (CMC). The electrolyte concentration of the suspensions dictated the kinetic stability of nano-TiO(2) thus influencing the transport and retention of the nanoaggregates in the saturated porous medium. With increasing ionic strength, the interaction between approaching nano-TiO(2) and nano-TiO(2) already deposited onto collectors surfaces seemed to be more favorable than the interaction between approaching nano-TiO(2) and bare collectors surfaces. The abrupt and gradual reduction in electrolyte concentration during the flushing cycles of the column experiments induced the release of previously deposited nano-TiO(2) suggesting attachment of nano-TiO(2) through secondary energy minimum.

The biophysicochemical interactions at the interfaces between nanoparticles and aquatic organisms: adsorption and internalization

Nano–bio interfacial interactions that can likely regulate the potential toxicity of nanoparticles (NPs) toward aquatic organisms are receiving increasing research interest worldwide and warrant more investigation. This review presents an overview of already-known nano–bio interactions and some speculations on the interfaces between NPs and aquatic organisms, in order to gain a new insight into the biological effects of NPs in the aquatic environment. The fundamental interfaces between NPs and organism cells and the main biophysicochemical interactions that occur at the nano–bio interfaces are described. The interfacial interactions, focused on adsorption and internalization, during the contact of NPs with microorganisms, hydrophytes, invertebrates and fish were reviewed. The effects of NP properties and suspending states as well as environmental conditions including pH, ionic strength, natural organic matter and other factors on the interfacial interactions were elucidated. Furthermore, the analytical methods employed in the interfacial interaction investigations were also briefly introduced. Future research directions of nano–bio interactions were prospected.

Effects of nanopolystyrene on the feeding behavior of the blue mussel (Mytilus edulis L.)

As the industrial production of nanoplastic and the degradation of microplastic into smaller particles at sea increase, the potential amount of nanoplastics in the marine environment rises. It has been reported that mussels uptake 100-nm polystyrene (PS) beads; to date, however, the effects of this uptake on the organism are unknown. In the present study, the authors investigated the effects of 30-nm PS on the feeding behavior of the blue mussel (Mytilus edulis) by exposing the organism to different nano PS and different algae (Pavlova lutheri) concentrations. The state of nano PS aggregation in the exposure medium was assessed using dynamic light scattering. In all treatments that contained nano PS, M. edulis produced pseudofeces. The total weight of the feces and pseudofeces increased with increasing nano PS and increasing algae concentration. Furthermore, M. edulis reduced its filtering activity when nano PS was present but still caused a decrease in the apparent nano PS concentration in the water. The presence of nano PS around the foot of M. edulis after the bioassay confirmed that the organism removed nano PS from the water. Chronic effect studies are therefore needed to investigate the effects of nanoplastics in M. edulis and possible consequences for its predators, including humans.

Cd2+ toxicity as affected by bare TiO2 nanoparticles and their bulk counterpart

Toxicity of engineered nanoparticles has received extensive attention in recent years. However, nanoparticles always co-exist with other pollutants in natural environment. Whether there are any interactions between these classical pollutants and nanoparticles; and how these interactions may influence the environmental behavior, effects and fate of each other remain largely unclear. For this purpose, effects of bare titanium dioxide engineered nanoparticles (TiO(2)-NP) and their bulk counterpart (TiO(2)-BC) on Cd(2+) bioavailability and toxicity to the green alga Chlamydomonas reinhardtii were examined in the present study. We first investigated the kinetics and equilibrium isotherm of Cd(2+) adsorption on both particles in the algal culture medium. Pseudo-first-order adsorption kinetics was observed with equilibrium rate constant ranging from 0.19 to 0.33min(-1). Increase in Cd(2+) adsorption with its ambient concentration at equilibrium followed a single Langmuir isotherm for different concentrations of TiO(2). Furthermore, surface-area-based Cd(2+) adsorption by TiO(2)-BC was higher than that by TiO(2)-NP in most Cd(2+) concentration treatments suggesting that particle size was not the only cause for different adsorption. Both forms of TiO(2) could alleviate Cd(2+) inhibitive effects on C. reinhardtii. However, Cd(2+) toxicity and its bioaccumulation were comparable as long as its free ion concentration in ambient toxicity media was similar regardless the particle size and concentration of TiO(2). There was no TiO(2) inside the algal cells either. Therefore, it was Cd(2+) adsorption by TiO(2) which decreased its ambient free ion concentration and further its intracellular accumulation as well as toxicity.

Toxicity assessment of iron oxide nanoparticles in zebrafish (Danio rerio) early life stages

Iron oxide nanoparticles have been explored recently for their beneficial applications in many biomedical areas, in environmental remediation, and in various industrial applications. However, potential risks have also been identified with the release of nanoparticles into the environment. To study the ecological effects of iron oxide nanoparticles on aquatic organisms, we used early life stages of the zebrafish (Danio rerio) to examine such effects on embryonic development in this species. The results showed that ≥10 mg/L of iron oxide nanoparticles instigated developmental toxicity in these embryos, causing mortality, hatching delay, and malformation. Moreover, an early life stage test using zebrafish embryos/larvae is also discussed and recommended in this study as an effective protocol for assessing the potential toxicity of nanoparticles. This study is one of the first on developmental toxicity in fish caused by iron oxide nanoparticles in aquatic environments. The results will contribute to the current understanding of the potential ecotoxicological effects of nanoparticles and support the sustainable development of nanotechnology.

Distinct effects of humic acid on transport and retention of TiO2 rutile nanoparticles in saturated sand columns

The distinct effects of humic acid (HA, 0-10 mg L(-1)) on the transport of titanium dioxide (rutile) nanoparticles (nTiO(2)) through saturated sand columns were observed under conditions of environmental relevance (ionic strength 3-200 mM NaCl, pH 5.7 and 9.0). Specifically, the transport of nTiO(2) was dramatically enhanced in the presence of HA at pH 5.7, even at a low HA concentration of 1 mg L(-1). The mobility of nTiO(2) was further increased with greater concentrations of HA. In contrast, this enhancement of the nTiO(2) transportability due to the presence of HA was limited at pH 9.0 because of the negligible adsorption of HA onto nTiO(2), regardless of the concentrations of HA examined in this study. The distinct effects can be explained by the adsorption behaviors of HA to nTiO(2) and sand surfaces and the resulting interactions between nTiO(2) and sand surfaces under different conditions, which resulted in a large variation of the nTiO(2) transport and deposition behaviors at various conditions. In addition, theoretical interaction energy calculations and additional elution experiments indicate that the secondary energy minimum played an important role in controlling the nTiO(2) transport and deposition in porous media observed in this study. Moreover, the interaction energy calculations suggest that at pH 5.7, HA affected nTiO(2) transport by increasing the negative surface charge of nTiO(2) at low HA adsorption densities; whereas, combinations of increased electrostatic and steric interactions due to the presence of HA were the main mechanisms of enhanced transportability of nTiO(2) at high HA adsorption densities. Overall, results from this study suggest that natural organic matter and solution pH are likely key factors that govern the stability and mobility of nTiO(2) in the natural aquatic environment.

The binding of phenanthrene to engineered silver and gold nanoparticles

The steadily rising production and use of engineered nanoparticles (ENP) leads to their entry into the aquatic environment. In addition to the various adverse effects that have been seen for different organisms, ENP are suspected to influence the transport, bioavailability and toxic properties of a range of environmental contaminants that may adsorb to their surface. In this study, the binding properties of the polycyclic aromatic hydrocarbon phenanthrene to stabilized silver and gold ENP were investigated using a novel mass balance based single-equilibrium approach. Only citrate coated gold ENP (AuNP(CIT)) were found to bind phenanthrene. No binding was observed for polyvinylpyrolidone coated silver ENP (AgNP(PVP)) nor citrate coated silver ENP (AgNP(CIT)) suggesting that the properties of the core material have a major influence on binding reactions. A binding coefficient K(b) was defined as the ratio between the concentration of phenanthrene associated to the AuNP(CIT) and that freely dissolved in the exposure medium. Temperature was not seen to significantly influence K(b) within an environmentally relevant range (4-25 °C). The presence of methanol significantly reduced or prevented the formation of the AuNP(CIT)-phenathrene complex. Results suggest that the binding is a low energy physio-sorption, likely associated to a partial displacement or specific arrangement of the citrate capping on the gold core.

Toxic effects of engineered nanoparticles in the marine environment: model organisms and molecular approaches

Engineered nanoparticles (ENPs) have been produced by nano-biotech companies in recent decades to generate innovative goods in various fields, including agriculture, electronics, biomedicine, manufacturing, pharmaceuticals and cosmetics. The nano-scale size of the particles can confer novel and significantly improved physical, chemical and biological properties to scientific phenomena and processes. As their applications to science and technology expand, the need to understand the putative noxious effects of ENPs on humans and ecosystems is becoming increasingly important. ENPs are emerging as a new class of pollutants with eco-toxicological impacts on marine ecosystems because the particles can end up in waterways and reach the sea. Recent laboratory studies in invertebrates and fishes suggest that exposure to ENPs could have harmful effects. Because there is not much data available for gauging the effects of ENPs on marine wildlife, the ultimate ecotoxicological impacts of chronic exposure to ENPs should be investigated further using laboratory tests and field studies. We propose the use of model organisms to understand the molecular pathways involved in the mechanisms that may be affected by exposure to ENPs. Sensitive and innovative molecular methods will provide information regarding the hazards of ENPs that may exist in the marine environment. Model organisms that have not been conventionally used for risk assessment and the development of eco-toxicogenomic approaches will result in an improved understanding of the mechanistic modes of action of contaminating ENPs in the marine environment.

Cd2+ Toxicity to a green alga Chlamydomonas reinhardtii as influenced by its adsorption on TiO2 engineered nanoparticles

In the present study, Cd²⁺ adsorption on polyacrylate-coated TiO₂ engineered nanoparticles (TiO₂-ENs) and its effect on the bioavailability as well as toxicity of Cd²⁺ to a green alga Chlamydomonas reinhardtii were investigated. TiO₂-ENs could be well dispersed in the experimental medium and their pH_pzc is approximately 2. There was a quick adsorption of Cd²⁺ on TiO₂-ENs and a steady state was reached within 30 min. A pseudo-first order kinetics was found for the time-related changes in the amount of Cd²⁺ complexed with TiO₂-ENs. At equilibrium, Cd²⁺ adsorption followed the Langmuir isotherm with the maximum binding capacity 31.9, 177.1, and 242.2 mg/g when the TiO₂-EN concentration was 1, 10, and 100 mg/l, respectively. On the other hand, Cd²⁺ toxicity was alleviated in the presence of TiO₂-ENs. Algal growth was less suppressed in treatments with comparable total Cd²⁺ concentration but more TiO₂-ENs. However, such toxicity difference disappeared and all the data points could be fitted to a single Logistic dose-response curve when cell growth inhibition was plotted against the free Cd²⁺ concentration. No detectable amount of TiO₂-ENs was found to be associated with the algal cells. Therefore, TiO₂-ENs could reduce the free Cd²⁺ concentration in the toxicity media, which further lowered its bioavailability and toxicity to C. reinhardtii.