The contamination of the aquatic environment by plastic nanoparticles is becoming a major concern due to their potential adverse effects in aquatic biota. Therefore, in-depth knowledge of their ...uptake, trafficking and effects at cellular and systemic levels is essential to understand their potential impacts for aquatic species. In this work, zebrafish (Danio rerio) was used as a model and our aims were: i) to determine the distribution, uptake, trafficking, degradation and genotoxicity of polystyrene (PS) NPs of different sizes in a zebrafish cell line; ii) to study PS NPs accumulation, migration of immune cells and genotoxicity in larvae exposed to PS NPs; and iii) to assess how PS NPs condition the survival of zebrafish larvae exposed to a pathogen and/or how they impact the resistance of an immunodeficient zebrafish. Our results revealed that the cellular distribution differed depending on the particle size: the 50 nm PS NPs were more homogeneously distributed in the cytoplasm and the 1 μM PS NPs more agglomerated. The main endocytic mechanisms for the uptake of NPs were dynamin-dependent internalization for the 50 nm NPs and phagocytosis for the 1 μm nanoparticles. In both cases, degradation in lysosomes was the main fate of the PS NPs, which generated alkalinisation and modified cathepsin genes expression. These effects at cellular level agree with the results in vivo, since lysosomal alkalization increases oxidative stress and vice versa. Nanoparticles mainly accumulated in the gut, where they triggered reactive oxygen species, decreased expression of the antioxidant gene catalase and induced migration of immune cells. Finally, although PS NPs did not induce mortality in wild-type larvae, immunodeficient and infected larvae had decreased survival upon exposure to PS NPs. This fact could be explained by the mechanical disruption and/or the oxidative damage caused by these NPs that increase their susceptibility to pathogens.
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•The impact of PS NPs was studied at the cellular, molecular and systemic levels.•The distribution and uptake of PS NPs in the ZF4 cell line were size dependent.•PS NPs colocalized with lysosomes and raised the pH of these organelles.•In vivo, PS NPs accumulated mainly in the gut and induced leukocyte migration.•PS NPs decreased the survival of immunosuppressed or infected larvae.
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•The accumulation of PS NPs in M. galloprovincialis tissues was size-dependent.•Translocation to the hemolymph was higher for 50 nm PS NPs.•The uptake of PS NPs into hemocytes was ...controlled by different endocytic pathways.•Hemocytes exposed to PS NPs had their motility and immune function compromised.•Myt C was downmodulated after PS NPs and V. splendidus exposure, but not phagocytosis.
Plastic litter is an issue of global concern. In this work Mytilus galloprovincialis was used to study the distribution and effects of polystyrene nanoplastics (PS NPs) of different sizes (50 nm, 100 nm and 1 μm) on immune cells. Internalization and translocation of NPs to hemolymph were carried out by in vivo experiments, while endocytic routes and effects of PS NPs on hemocytes were studied in vitro. The smallest PS NPs tested were detected in the digestive gland and muscle. A fast and size-dependent translocation of PS NPs to the hemolymph was recorded after 3 h of exposure. The internalization rate of 50 nm PS NPs was lower when caveolae and clathrin endocytosis pathways were inhibited. On the other hand, the internalization of larger particles decreased when phagocytosis was inhibited. The hemocytes exposed to NPs had changes in motility, apoptosis, ROS and phagocytic capacity. However, they showed resilience when were infected with bacteria after PS NP exposure being able to recover their phagocytic capacity although the expression of the antimicrobial peptide Myticin C was reduced. Our findings show for the first time the translocation of PS NPs into hemocytes and how their effects trigger the loss of its functional parameters.
The last decade has seen a considerable increase in the use of silver nanoparticles (AgNPs), which are found in many every-day consumer products including textiles, plastics, cosmetics, household ...sprays and paints. The release of those AgNPs into aquatic environments could be causing ecological damage. In this study we assess the toxicity of AgNPs of different sizes to two species of microalgae, from freshwater and marine environment (Chlamydomonas reinhardtii and Phaeodactylum tricornutum respectively). Dissolution processes affect the form and concentration of AgNPs in both environments. Dissolution of Ag from AgNPs was around 25 times higher in marine water. Nevertheless, dissolution of AgNPs in both culture media seems to be related to the small size and higher surface area of NPs. In marine water, the main chemical species were AgCl2− (53.7%) and AgCl3−2 (45.2%). In contrast, for freshwater, the main chemical species were Ag+ (26.7%) and AgCl− (4.3%). The assessment of toxicological responses, specifically growth, cell size, cell complexity, chlorophyll a, reactive oxygen species, cell membrane damage and effective quantum yield of PSII, corroborated the existence of different toxicity mechanisms for microalgae. Indirect effects, notably dissolved Ag ions, seem to control toxicity to freshwater microalgae, whereas direct effects, notably attachment onto the cell surface and the internalization of AgNPs inside cells, seem to determine toxicity to the marine species studied. This research contributes to knowledge on the role of intrinsic and extrinsic factors in determining the behavior of NPs in different aquatic environments and the interaction with microalgae.
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•Ionic strength and size of AgNPs govern the dissolution process.•Toxicity of AgNPs to freshwater microalgae seems to be determined by the presence of Ag+ in culture media (indirect effect).•Toxicity of AgNPs in marine microalgae seems to be ruled by direct effects of AgNPs, as adsorption and internalization.
Use of titanium dioxide nanoparticles (TiO2 NPs) has become a part of our daily life and the high environmental concentrations predicted to accumulate in aquatic ecosystems are cause for concern. ...Although TiO2 has only limited reactivity, at the nanoscale level its physico-chemical properties and toxicity are different compared with bulk material. Phytoplankton is a key trophic level in fresh and marine ecosystems, and the toxicity provoked by these nanoparticles can affect the structure and functioning of ecosystems. Two microalgae species, one freshwater (Chlamydomonas reinhardtii) and the other marine (Phaeodactylum tricornutum), have been selected for testing the toxicity of TiO2 in NP and conventional bulk form and, given its photo-catalytic properties, the effect of UV-A was also checked. Growth inhibition, quantum yield reduction, increase of intracellular ROS production, membrane cell damage and production of exo-polymeric substances (EPS) were selected as variables to measure.
TiO2 NPs and bulk TiO2 show a relationship between the size of agglomerates and time in freshwater and saltwater, but not in ultrapure water. Under two treatments, UV-A (6 h per day) and no UV-A exposure, NPs triggered stronger cytotoxic responses than bulk material. TiO2 NPs were also associated with greater production of reactive oxygen species and damage to membrane. However, microalgae exposed to TiO2 NPs and bulk TiO2 under UV-A were found to be more sensitive than in the visible light condition. The marine species (P. tricornutum) was more sensitive than the freshwater species, and higher Ti internalization was measured. Exopolymeric substances (EPS) were released from microalgae in the culture media, in the presence of TiO2 in both forms. This may be a possible defense mechanism by these cells, which would enhance processes of homoagglomeration and settling, and thus reduce bioavailability.
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•Agglomeration of NPs is similar in different media.•Intrinsic characteristics of microalgae drives NPs toxicity.•Both microalgae species accumulate TiO2 NPs.•Exopolymeric substances (EPS) contribute to microalgae detoxification processes.
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•Bimetallic PdNb catalysts show promising results in the dry reforming of methane.•A synergic effect between Pd and Nb is observed.•The addition of Nb improved the catalytic activity ...minimizing carbon deposits formation.•The catalytic stability depended on the reoxidation degree of active sites.
This work describes the use of Pd-Nb catalysts supported on commercial silica in the dry reforming of methane. The effect of Pd/Nb ratio was evaluated and it determined the catalytic response of the prepared catalysts. Thus, it was observed that the catalytic activity increased with the Pd/Nb ratio and bimetallic samples were more active than the monometallic ones. The sample with the highest Pd/Nb ratio was the best in terms of conversion, selectivity and stability. Nb presence decreased the amount of carbon deposited on the catalysts since the decomposition of CH4 is minimised in the operating conditions.
CeO2 nanoparticles (CeO2 NPs) are well-known for their catalytic properties and antioxidant potential. Recent uses in therapy are based on the Ce+3 ions released by CeO2 NPs. Reactions involving ...redox cycles between Ce+3 and Ce+4 oxidation stage seem to promote scavenging of reactive oxygen species (ROS), thus protecting cells from oxygen damage. However, the internalization of CeO2 NPs and release of Ce+3 could be responsible for a toxic effect on cells. The literature reports controversial results on the toxicity of CeO2 NPs to phytoplankton. Therefore, we have tested the potential toxic effect of two CeO2 NPs (with positive and negative zeta potential) and bulk CeO2 (at 0.1, 1, 10, 100 and 200mg·L−1) on three species of microalgae from different environments: marine diatom (Phaeodactylum tricornutum), marine chlorophyte (Nannochloris atomus) and freshwater chlorophyte (Chlamydomonas reinhardtii) over 72h in batch cultures. Responses measured in the microalgae population are: growth, chlorophyll a, cell size, cell complexity, percentage of ROS, and percentage of cell membrane damage. Positive zeta potential CeO2 NPs provoked greater cell complexity (up to 78, 172 and 23 times more cell complexity than in controls found for C. reinhardtii, P. tricornutum and N. atomus respectively) than negative zeta potential CeO2 NPs. The SSC signal detected by flow cytometry measured increases of particles entering cells, and this is related to cell viability and levels of intracellular ROS (correlation between SSC and percentage of ROS of 0.72 and 0.97 found for C. reinhardtii and P. tricornutum). When increased cellular complexity over controls is between 2 and 6 times greater, CeO2 (in bulk or nanoparticulate form) seems to protect against ROS. When increased cellular complexity is from 7 to 23 times greater, CeO2 does not provoke toxic responses; however, when increased cellular complexity over controls is very high, from 61 to 172 times, increased ROS production and toxic responses are found. Results show that two factors, the charge of CeO2 NPs and cell wall structure, constitute the primary barrier to the possible accumulation of CeO2 NPs within phytoplankton cytosol.
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•Toxicity of CeO2 NPs to C. reinhardtii, P. tricornutum and N. atomus is studied.•Changes in cell complexity mean CeO2 NPs may be either toxic or protective.•Positively-charged CeO2 NPs alter cell complexity more and increase cytotoxicity.•Internalization of CeO2 NPs depends on ultrastructure and composition of cell walls.
TiO2 nanoparticles (TiO2 NPs) are employed in many products (paints, personal care products, especially sunscreens, plastics, paper, water potabilization and food products) and are then released into ...the environment from these products. These nanoparticles present potential risk to freshwater and marine microalgae. The primary toxicity mechanism is adsorption between NPs and microalgae (heteroagglomeration); however, studies of interactions of this kind are scarce. We investigated the heteroagglomeration process that occurs between two forms of TiO2 material, nanoparticles and bulk, and three different microalgae species, and under different environmental conditions (freshwater and marine water), in order to assess the influence of pH and ionic strength (IS). The heteroagglomeration process was examined by means of co-settling experiments and the Derjaguin-Landau-Verwey-Overbeek (DLVO) approach. The homoagglomeration process (only NPs to NPs) did not show differences between culture media (freshwater and marine water). However, in the heteroagglomeration process between NPs and cells, IS played an important role. Ions can compress the electro-double layer between NPs and microalgae, allowing a heteroagglomeration process to take place, as shown by settling experiments. TiO2 NPs presented a settling rate higher than bulk TiO2. The DLVO theory could only partially explain heteroagglomeration because, in this model, it is not considered that NP-NP and Cell-Cell homoagglomeration co-occur. In this study neither the role of exopolymeric substances in the interaction between NPs and cells nor detoxification are considered. The authors suggest that the interaction between NPs and microalgae could be considered as the first stage in the process by which nanoparticles affect microalgae.
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•Interaction between TiO2 NPs and cells could be considered as the first mechanism of contact and toxicity.•Heteroagglomeration is more intense when ionic strength increases.•NP-NP interaction is greater for TiO2 NPs than for bulk TiO2.•NP-cell interaction is not explained by DLVO theory; more complex interactions are given in the culture media.
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•Two types of CeO2 NPs were tested on mussel hemocytes using in vitro assays.•CeO2 NPs with a negative zeta potential and Cu,Zn-SOD biocorona showed more significant effects than ...neutral NPs.•CeO2 NPs with a rounded shape showed more toxic effect than well-faceted ones.•Immunosuppressive effects were observed in hemocyte cells when exposed to CeO2 NPs.
Over the last decades, the growth in nanotechnology has provoked an increase in the number of its applications and consumer products that incorporate nanomaterials in their formulation. Metal nanoparticles are released to the marine environment and they can interact with cells by colloids forces establish a nano-bio interface. This interface can be compatible or generate bioadverse effects to cells. The daily use of CeO2 nanoparticles (CeO2 NPs) in industrial catalysis, sunscreen, fuel cells, fuel additives and biomedicine and their potential release into aquatic environments has turned them into a new emerging pollutant of concern. It is necessary to assess of effects of CeO2 NPs in aquatic organisms and understand the potential mechanisms of action of CeO2 NP toxicity to improve our knowledge about the intrinsic and extrinsic characteristic of CeO2 NPs and the interaction of CeO2 NPs with biomolecules in different environment and biological fluids. The conserved innate immune system of bivalves represents a useful tool for studying immunoregulatory responses when cells are exposed to NPs. In this context, the effects of two different CeO2 NPs with different physico-chemical characteristics (size, shape, zeta potential and Ce+3/Ce+4 ratio) and different behavior with biomolecules in plasma fluid were studied in a series of in vitro assays using primary hemocytes from Mytilus galloprovincialis. Different cellular responses such as lysosome membrane stability, phagocytosis capacity and extracellular reactive oxygen species (ROS) production were evaluated. Our results indicate that the agglomeration state of CeO2 NPs in the exposure media did not appear to have a substantial role in particle effects, while differences in shape, zeta potential and biocorona formation in NPs appear to be important in provoking negative impacts on hemocytes.
The negative charge and the rounded shape of CeO2 NPs, which formed Cu, Zn-SOD biocorona in hemolymph serum (HS), triggered higher changes in the biomarker of stress (LMS) and immunological parameters (ROS and phagocytosis capacity). On the other hand, the almost neutral surface charge and well-faceted shape of CeO2 NPs did not show either biocorona formation in HS under tested conditions or significant responses. According to the results, the most relevant conclusion of this work is that not only the physicochemical characterization of CeO2 NPs plays an important role in NPs toxicity but also the study of the interaction of NPs with biological fluids is essential to know it behavior and toxicity at cellular level.
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•Synthesis at low temperature of Cu-Fe mixed oxides with controlled composition.•Optimum specific surface area and lattice oxygen mobility for a 2 Fe/Cu molar ratio.•Cuprospinel ...CuFe2O4 formation was confirmed by fine structural characterization.•High conversion, selectivity to CO2 and stability in catalytic CO-PROX reaction.•Fe enhances Cu resistance to full reduction during reaction delaying deactivation.
Copper-iron mixed oxides with Fe/Cu molar ratios ranging from pure CuO to Fe2O3 were synthesised by a low temperature co-precipitation method, and tested in the CO-PROX reaction. The extensive characterization performed by means of different techniques showed the progressive variation of physical and chemical properties including composition, texture, structure and reducibility of the prepared oxides. Rietveld analysis of X-ray diffraction data, XPS and Raman spectra, and especially TEM study revealed the formation of CuFe2O4. All the samples were more active and selective below 200 °C than a commercial Pt/Al2O3 catalyst used as a reference. In particular, the catalyst having a 2 Fe/Cu molar ratio, corresponding to the cuprospinel stoichiometry, exhibited the best performance with a 76% conversion and a 60% selectivity at 125 °C, operating with 50% of H2 in the gas stream, being relatively stable in long-term time-on-stream experiments. On the contrary, pure CuO rapidly deactivated in the course of reaction at 150 °C. Differences in catalytic stability were related to a promoting effect of iron in the mixed oxide which makes copper more resistant to full reduction.
This work is devoted to evaluating the relationship between the oxygen content and catalytic activity in the CO oxidation process of the 6H-type BaFeO
system. Strong evidence is provided about the ...improvement of catalytic performance with increasing Fe average oxidation state, thus suggesting the involvement of lattice oxygen in the catalytic process. The compositional and structural changes taking place in both the anionic and cationic sublattices of the catalysts during redox cycles have been determined by temperature-resolved neutron diffraction. The obtained results evidence a structural transition from hexagonal (
6
/
) to orthorhombic (
) symmetry. This transition is linked to octahedra distortion when the Fe
concentration exceeds 40% (δ values higher than 0.2). The topotactical character of the redox process is maintained in the δ range 0 < δ < 0.4. This suggests that the cationic framework is only subjected to slight structural modifications during the oxygen exchange process occurring during the catalytic cycle.
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