Manufactured nanoparticles in the aquatic environment-biochemical responses on freshwater organisms: A critical overview

Copper-oxide nanoparticles effects on goldfish (Carassius auratus): Lethal toxicity, haematological, and biochemical effects

The advancement of nanotechnology and the widespread use of nanoparticles (NPs) in various industries have highlighted the importance of studying the potential harmful effects of nanomaterials on organisms. This study aimed to evaluate the lethal toxicity thresholds of Copper Oxide Nanoparticles (CuO-NPs). The investigation focused on examining the sub-lethal toxicity effects of CuO-NPs on blood parameters, as well as their influence on the gill tissue and liver of goldfish (Carassius auratus). Goldfish were exposed to varying concentrations of CuO-NPs (10, 20, 30, 40, 60, 80, and 100 mg/L) for 96 h. The Probit software was employed to determine the LC50 (lethal concentration causing 50% fish mortality) by monitoring and documenting fish deaths at 24, 48, 72, and 96-hour intervals. Subsequently, sub-lethal concentrations of 5% LC50 (T1), 10% LC50 (T2), and 15% LC50 (T3) of CuO-NPs were administered based on the LC50 level to investigate their effects on haematological parameters, encompassing the number of red blood cells and white blood cells, hematocrit and haemoglobin levels, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration. Additionally, histopathological examinations were conducted on the gill and liver tissues of the studied fish. Results indicated concentration-response of fish mortalities. In general, changes in the blood biochemical parameters of fish exposed to sub-lethal concentrations of CuO-NPs included a significant decrease in leukocyte count and glucose level and an increase in protein and triglyceride levels. Furthermore, an escalation in tissue damage such as gill apical and basal hyperplasia, lamellae attachment, squamous cell swelling, blood cell infiltration, and cellular oedema in gills tissue. and bleeding, increased sinusoidal space, necrosis, lateralization of the nucleus, cell swelling, and water retention in the liver. The findings showed dose-dependent increasing toxicity in goldfish specimens exposed to CuO-NPs.

Ecotoxicity and trophic transfer of metallic nanomaterials in aquatic ecosystems

Metallic nanomaterials (MNMs) possess unique properties that have led to their widespread application in fields such as electronics and medicine. However, concerns about their interactions with environmental factors and potential toxicity to aquatic life have emerged. There is growing evidence suggesting MNMs can have detrimental effects on aquatic ecosystems, and are potential for bioaccumulation and biomagnification in the food chain, posing risks to higher trophic levels and potentially humans. While many studies have focused on the general ecotoxicity of MNMs, fewer have delved into their trophic transfer within aquatic food chains. This review highlights the ecotoxicological effects of MNMs on aquatic systems via waterborne exposure or dietary exposure, emphasizing their accumulation and transformation across the food web. Biomagnification factor (BMF), the ratio of the contaminant concentration in predator to that in prey, was used to evaluate the biomagnification due to the complex nature of aquatic food chains. However, most current studies have BMF values of less than 1 indicating no biomagnification. Factors influencing MNM toxicity in aquatic environments include nanomaterial properties, ion variations, light, dissolved oxygen, and pH. The multifaceted interactions of these variables with MNM toxicity remain to be fully elucidated. We conclude with recommendations for future research directions to mitigate the adverse effects of MNMs in aquatic ecosystems and advocate for a cautious approach to the production and application of MNMs.

Comparative Toxicity of TiO2 and Sn-Doped TiO2 Nanoparticles in Zebrafish After Acute and Chronic Exposure

This study was conducted to assess the toxicological potential of synthesized pure and Sn-doped TiO2 NPs (Sn-TiO2 NPs) in zebrafish after acute and chronic exposure. The pure TiO2 NPs, 4%, and 8% Sn-TiO2 NPs were synthesized and characterized using X-ray diffraction, Scanning Electron Microscope, diffuse reflectance spectra, dynamic light scattering, and zeta potential analyses. The pure TiO2 NPs, 4%, and 8% Sn-TiO2 NPs were spherical with average sizes of about 40, 28, and 21 nm, respectively, indicating significant size reduction of TiO2 NPs following Sn doping. According to our results, the LC50-96h increased in the order of 8% Sn-TiO2 NPs (45 mg L-1) < 4% Sn-TiO2 NPs (80.14 mg L-1) < pure TiO2 NPs (105.47 mg L-1), respectively. Exposure of fish to Sn-TiO2 NPs after 30 days resulted in more severe histopathological alterations in gills, liver, intestine, and kidneys than pure TiO2 NPs. Furthermore, Sn-doping significantly elevated malondialdehyde levels and micronuclei frequency, indicating increased oxidative stress and genotoxicity. Expression analysis revealed altered expression of various genes, including upregulation of pro-apoptotic Bax gene and downregulation of anti-apoptotic Bcl-2 gene, suggesting potential induction of apoptosis in response to Sn-doped NPs. Additionally, antioxidant genes (Gpx, Sod, Cat, and Ucp-2) and stress response gene (Hsp70) showed altered expression, suggesting complex cellular responses to mitigate the toxic effects. Overall, this study highlights the concerning impact of Sn-doping on the toxicity of TiO2 NPs in zebrafish and emphasizes the need for further research to elucidate the exact mechanisms underlying this enhanced toxicity.

Antioxidant response to ZnO nanoparticles in juvenile Takifugu obscurus: protective effects of salinity

The extensive utilization of Zinc Oxide nanoparticles (ZnO NPs) has garnered significant attention due to their detrimental impacts on ecosystem. Unfortunately, ecotoxicity of ZnO NPs in coastal waters with fluctuating salinity has been disregarded. This study mainly discussed the toxic effects of ZnO NPs on species inhabiting the transition zones between freshwater and brackish water, who are of great ecological and economic importance among fish. To serve as the model organism, Takifugu obscurus, a juvenile euryhaline fish, was exposed to different ZnO NPs concentrations (0-200 mg/L) and salinity levels (0 and 15 ppt). The results showed that a moderate increase in salinity (15 ppt) could alleviate the toxic effect of ZnO NPs, as evidenced by improved survival rates. The integrated biomarker response index on oxidative stress also revealed that the toxicity of ZnO NPs was higher in freshwater compared to brackish water. These outcomes can be attributed to higher salinity (15 ppt) reducing the bioavailability of ZnO NPs by facilitating their aggregation and inhibiting the release of metal ions. It is noteworthy that elevated salinity was found to alleviate ZnO NPs toxicity by means of osmotic adjustment via the activation of Na+/K+-ATPase activity. This study demonstrates the salinity-dependent effect of ZnO NPs on T. obscurus, suggesting the possibility for euryhaline fish like T. obscurus to adapt their habitat towards more saline environments, under constant exposure to ZnO NPs.

Evaluation of Developmental Toxicity and Oxidative Stress Caused by Zinc Oxide Nanoparticles in Zebra Fish Embryos/ Larvae

Zinc oxide nanoparticles (ZnO NPs) are used in various fields, including biological ones. ZnO NPs are eventually disposed of in the environment where they may affect natural systems, and there is no international law to regulate their manufacture, usage, and disposal. Hence, this present study is carried out to synthesise a more non-toxic and bioactive ZnO NPs from the marine algae Sargassum polycystum. The ZnO NPs were biologically produced using the marine algae Sargassum polycystum. The dynamic light scattering result describes that synthesised particles' average size is about 100 nm in diameter. Transmission electron microscopy (TEM) analysis demonstrated the rod-like morphology of ZnO NPs. Fourier tranform-infrared spectroscopy (FT-IR) results revealed the presence of functional groups in ZnO NPs. The selected area electron diffraction (SAED) results strongly suggested the ZnO NPs crystallinity. ZnO NPs surface morphology and compositions were identified by scanning electron microscopy (SEM- EDX) values. To analyse the toxicity of synthesised nanoparticles, zebra fish larvae were used, which involved subjecting embryos to various ZnO NPs concentrations at 1 hpf and analysing the results at 96 hpf. The 60 and 80 ppm sub-lethal doses were chosen for further studies based on the LC50 (82.23 ppm). In the ZnO NPs-treated groups, a significant slowdown in pulse rate and a delay in hatching were seen, both of which impacted the embryonic processes. A teratogenic study revealed a dose-dependent increase in the incidence of developmental deformities in the treated groups. Along with increased oxidants and a corresponding reduction in antioxidant enzymes, Na+ K+-ATPase and AChE activity changes were seen in ZnO NPs-treated zebra fish larvae groups. The apoptosis process was increased in ZnO NPs-treated groups revealed by acridine orange staining. These results indicate that the green synthesis process cannot mitigate the oxidative stress induced by ZnO NPs on oxidative signalling.

Toxicity of Beauty Salon Effluents Contaminated with Hair Dye on Aquatic Organisms

Cosmetic residues have been found in water resources, especially trace elements of precursors, couplers, and pigments of hair dyes, which are indiscriminately disposed of in the sewage system. These contaminants are persistent, bioactive, and bioaccumulative, and may pose risks to living beings. Thus, the present study assessed the ecotoxicity of two types of effluents generated in beauty salons after the hair dyeing process. The toxicity of effluent derived from capillary washing with water, shampoo, and conditioner (complete effluent-CE) and effluent not associated with these products (dye effluent-DE) was evaluated by tests carried out with the aquatic organisms Artemia salina, Daphnia similis, and Danio rerio. The bioindicators were exposed to pure samples and different dilutions of both effluents. The results showed toxicity in D. similis (CE50 of 3.43% and 0.54% for CE and DE, respectively); A. salina (LC50 8.327% and 3.874% for CE and DE, respectively); and D. rerio (LC50 of 4.25-4.59% and 7.33-8.18% for CE and DE, respectively). Given these results, we can infer that hair dyes, even at low concentrations, have a high toxic potential for aquatic biota, as they induced deleterious effects in all tested bioindicators.

Baicalein inhibits apoptosis and autophagy induced by chlorpyrifos exposure to kidney of Cyprinus carpio through activation of PI3K/AKT pathway

Chlorpyrifos (CPF), a widely used organophosphate pesticide that has caused large-scale contamination globally, has become a major concern. Baicalein (BAI), as a flavonoid extract, shows anti-inflammatory as well as antioxidant activities. The kidneys of fish serve to excrete toxins and are major target organs for environmental contaminants. However, it is not obvious whether BAI can counteract the damage caused by CPF exposure to fish kidneys. Therefore, we conducted a 30-day simulation of CPF poisoning and/or BAI treatment by adding 23.2 μg/L CPF to water and/or 0.15 g/kg BAI to feed. In the transmission electron microscopy results, we observed obvious phenomenon of autophagy and apoptosis in the CPF group, and the TUNEL staining and immunofluorescence of LC3B and p62 double-staining results confirmed that CPF induced autophagy and apoptosis in the kidney of common carp. Furthermore, CPF induced the increase of ROS level and inhibition of PI3K and Nrf2 pathways, which in turn triggered oxidative stress, autophagy and apoptosis in carp kidney according to western blot, RT-qPCR and kit assays. However, addition of BAI significantly alleviated oxidative stress, autophagy and apoptosis due to binding to PI3K protein. Additionally, through phylogenetic tree and structural domain analyses, we also found that the binding sites of BAI and PI3K are conserved in a variety of representative species. These results suggest that BAI antagonizes CPF-caused renal impairments in carp involving the PI3K/AKT pathway and the Nrf2 pathway. Our findings provide new insights into the nephrotoxicity effects of CPF and the potential use of BAI as a detoxification agent for CPF intoxication.

Differential toxicity of various mineral nanoparticles to Synechocystis sp.: With and without ciprofloxacin

Mineral nanoparticles (M-NPs) are ubiquitous in aquatic environments, but their potential harms to primary producers and impacts on the toxicity of coexisting pollutants are largely unknown. Herein, the toxicity mechanisms of various M-NPs (i.e., SiO2, Fe2O3, Al2O3, and TiO2 NPs) to Synechocystis sp. in absence and presence of ciprofloxacin (CIP) were comprehensively investigated. The heteroaggregation of cells and M-NPs can hinder substrate transfer or light acquisition. The attraction between Synechocystis sp. and M-NPs increased in the order of SiO2 < Fe2O3 < Al2O3 ≈ TiO2 NPs. Therefore, SiO2 and Fe2O3 NPs exerted slight effects on physiology and proteome of Synechocystis sp.. Al2O3 NPs with the rod-like shape caused physical damage to cells. Differently, TiO2 NPs with photocatalytic activities provided photogenerated electrons for Synechocystis sp., promoting photosynthesis and the Calvin cycle for CO2 fixation. SiO2, Fe2O3, and Al2O3 NPs alleviated the toxicity of CIP in an adsorption-depended manner. Conversely, the combination of CIP and TiO2 NPs exerted more pronounced toxic effects compared to their individuals, and CIP disturbed the extracellular electron transfer from TiO2 NPs to cells. The findings highlight the different effects of TiO2 NPs from other M-NPs on cyanobacteria, either alone or in combination with CIP, and improve the understanding of toxic mechanisms of M-NPs.

Copper oxide nanoparticles exhibit variable response against enzymatic toxicity biomarkers of Moina macrocopa

Growing toxicity of nanomaterials to aquatic organisms is a major area of concern as it is destroying the carefully evolved aquatic ecosystem and food web. Copper oxide nanoparticles (CuONPs) are among the top industrially manufactured nanomaterials having multifaceted applications in medicine, agriculture, energy, water technology, and other areas. However, reports on detailed scientific understanding behind toxic effects of CuONPs on aquatic organisms are scant. The present work reports on the interaction of CuONPs of 10 ± 05 nm with an ecologically significant aquatic species, Moina macrocopa, at morphological and enzymatic levels. CuONPs were found to be severely toxic just within 48 h of exposure as seen from the lethal value (48 h LC50) of 0.137 ± 0.002 ppm. Profiling of enzymatic toxicity biomarkers indicated variable response of CuONPs on selected enzymes of M. macrocopa at two sub-lethal concentrations (0.013 to 0.039 ppm). While the activities of acetyl cholinesterase and digestive enzymes (trypsin, amylase) were found to be significantly (p < 0.001) lowered after exposure to CuONPs, the β-galactosidase activity was completely inhibited. Among the antioxidant enzymes that were assayed, superoxide dismutase and glutathione-S-transferase activity was found to increase (p > 0.001), while that of catalase decreased (p > 0.001, < 0.05) with increase in exposure to CuONPs. An upsurge of several folds was seen in the activity of alkaline phosphatase after exposure to CuONPs as compared to the control group. CuONPs accumulated in the gut region of M. macrocopa which provided an ideal environment for CuONP to interact and alter the enzymes in M. macrocopa. This report highlights the use of enzymes as sensitive biomarker to detect toxicity of trace amount of CuONPs in a very sensitive non-target crustacean species found in water bodies.

Oxidative stress, genotoxic effects, and other damages caused by chronic exposure to silver nanoparticles (Ag NPs) and zinc oxide nanoparticles (ZnO NPs), and their mixtures in zebrafish (Danio rerio)

This study assessed the oxidative stress impacts of Ag NPs and ZnO NPs and their mixtures in zebrafish (Danio rerio). Zebrafish were exposed to sublethal concentrations of each NP and a mixture for 28 days followed by a 28-day recovery period (without NP exposure) and measurements made on hepatic levels of antioxidant enzymes (CAT, SOD, and GPx), MDA levels, expression of the genes for the Hsp70 and Hsp90, and MT, blood biochemical parameters (total protein, globulin, albumin, AST, ALT, ALP, and LDH), and genotoxicity in erythrocytes (via measurement of micronuclei (MN) and nuclear (NA) abnormalities). There was a tendency for an increase in the variation in the responses of antioxidant defense systems and there were higher MDA levels with increasing exposure concentration of Ag NPs and with increasing exposure time. Total protein, globulin, and albumin decreased during the exposure period, especially on the days of 28. Moreover, levels of AST and LDH increased significantly in the NPs co-exposure treatments, while levels of ALT and ALP significantly decreased. The highest expression levels for these genes occurred on day 14 and in the NPs co-exposure treatments. For exposure to both NPs individually and as a mixture, the frequency of MN and other NA were significantly increased (p < 0.05). During the recovery periods, most of the effects seen were reduced, most notably in the individual NPs treatments. The overall results suggest that the toxic effects of Ag NPs and ZnO NPs in combination significantly increase their toxicity in zebrafish.

Are iron ore microparticles toxic for the European clam Ruditapes decussatus? Response elements from biomarker activities and in silico modeling

Inevitably, high concentrations of iron, the most widely produced ore globally, can be found in aquatic environments. To assess the toxicity of iron on aquatic organisms, Ruditapes decussatus specimens were subjected to microparticles derived from two types of iron ore (hematite and magnetite) at four different concentrations (0.5, 1, 1.5, and 5 g/L). The findings revealed that both types of iron ore were absorbed by clams in a concentration-dependent manner. Biomarkers analysis demonstrated significant and organ-specific impacts on the health of the clams caused by these microparticles, which was further supported by computational analyses on bioavailability. Within seven days of exposure, changes were observed in the activities of several enzymes, including catalase, acetylcholinesterase, and glutathione S-transferases, as well as in the rate of lipid peroxidation in both the digestive gland and gills. This study provides an environmental perspective on the toxicological effects of iron ore microparticles.

Comparison of Toxicity of Nano and Bulk Titanium Dioxide on Nile Tilapia (Oreochromis niloticus): Acetylcholinesterase Activity Modulation and DNA Damage

This study compared effects of low concentrations (0.05 and 0.1 mg/L) of nano-TiO₂ and bulk-TiO₂ on brain, gill and liver acetylcholinesterase (AChE) and erythrocytic DNA of Nile tilapia over 7 and 14 days exposure. Both TiO₂ forms did not affect brain AChE activities. Bulk-TiO₂ induced elevation of gill AChE activities only after 7 days while nano-TiO₂ had no effect. Liver AChE activities were increased by 0.1 mg/L bulk- and nano-TiO₂ to similar extents. At 7 days, erythrocytic DNA damage was induced only by 0.1 mg/L nano- and bulk-TiO₂ to similar extents, but damage was not repaired to control levels at 7 days recovery period. At 14 days continuous exposure, DNA damage was induced by 0.05, 0.1 mg/L nano-TiO₂ and 0.1 mg/L of bulk-TiO₂ to similar extents. Results show that both forms of TiO₂ can pose genotoxic hazards to fish populations under sub-chronic exposure. However, their neurotoxic potential was not evident.

Responses of Bacillus sp. under Cu(II) stress in relation to extracellular polymeric substances and functional gene expression level

The production and composition of extracellular polymeric substances (EPS), as well as the EPS-related functional resistance genes and metabolic levels of Bacillus sp. under Cu(II) stress, were investigated. EPS production increased by 2.73 ± 0.29 times compared to the control when the strain was treated with 30 mg L^-1 Cu(II). Specifically, the polysaccharide (PS) content in EPS increased by 2.26 ± 0.28 g CDW^-1 and the PN/PS (protein/polysaccharide) ratio value increased by 3.18 ± 0.33 times under 30 mg L^-1 Cu(II) compared to the control. The increased EPS secretion and higher PN/PS ratio in EPS strengthened the cells' ability to resist the toxic effect of Cu(II). Differential expression of functional genes under Cu(II) stress was revealed by Gene Ontology pathway enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. The enriched genes were most obviously upregulated in the UMP biosynthesis pathway, the pyrimidine metabolism pathway, and the TCS metabolism pathway. This indicates an enhancement of EPS regulation-related metabolic levels and their role as a defense mechanism for cells to adapt to Cu(II) stress. Additionally, seven copper resistance genes were upregulated while three were downregulated. The upregulated genes were related to the heavy metal resistance, while downregulated genes were related to cell differentiation, indicating that the strain had initiated an obvious resistance to Cu(II) despite its severe cell toxicity. These results provided a basis for promoting EPS-regulated associated functional genes and the application of gene-regulated bacteria in heavy metal-containing wastewater treatment.

Metal Oxide Nanoparticles in Food Packaging and Their Influence on Human Health

It is a matter of common knowledge in the literature that engineered metal oxide nanoparticles have properties that are efficient for the design of innovative food/beverage packages. Although nanopackages have many benefits, there are circumstances when these materials are able to release nanoparticles into the food/beverage matrix. Once dispersed into food, engineered metal oxide nanoparticles travel through the gastrointestinal tract and subsequently enter human cells, where they display various behaviors influencing human health or wellbeing. This review article provides an insight into the antimicrobial mechanisms of metal oxide nanoparticles as essential for their benefits in food/beverage packaging and provides a discussion on the oral route of these nanoparticles from nanopackages to the human body. This contribution also highlights the potential toxicity of metal oxide nanoparticles for human health. The fact that only a small number of studies address the issue of food packaging based on engineered metal oxide nanoparticles should be particularly noted.

Characterization of oxidative damage induced by nanoparticles via mechanism-driven machine learning approaches

The wide application of TiO₂-based engineered nanoparticles (nTiO₂) inevitably led to release into aquatic ecosystems. Importantly, increasing studies have emphasized the high risks of nTiO₂ to coastal environments. Bivalves, the representative benthic filter feeders in coastal zones, acted as important roles to assess and monitor the toxic effects of nanoparticles. Oxidative damage was one of the main toxic mechanisms of nTiO₂ on bivalves, but the experimental variables/nanomaterial characteristics were diverse and the toxicity mechanism was complex. Therefore, it was very necessary to develop machine learning model to characterize and predict the potential toxicity. In this study, thirty-six machine learning models were built by nanodescriptors combined with six machine learning algorithms. Among them, random forest (RF) - catalase (CAT), k-neighbors classifier (KNN) - glutathione peroxidase (GPx), neural networks - multilayer perceptron (ANN) - glutathione s-transferase (GST), random forest (RF) - malondialdehyde (MDA), random forest (RF) - reactive oxygen species (ROS), and extreme gradient boosting decision tree (XGB) - superoxide dismutase (SOD) models performed good with high accuracy and balanced accuracy for both training sets and external validation sets. Furthermore, the best model revealed the predominant factors (exposure concentration, exposure periods, and exposure matrix) influencing the oxidative stress induced by nTiO₂. These results showed that high exposure concentrations and short exposure-intervals tended to cause oxidative damage to bivalves. In addition, gills and digestive glands could be vulnerable to nTiO₂-induced oxidative damage as tissues/organs differences were the important factors controlling MDA activity. This study provided insights into important nano-features responsible for the different indicators of oxidative stress and thereby extended the application of machine learning approaches in toxicological assessment for nanoparticles.

Possible Interaction between ZnS Nanoparticles and Phosphonates on Mediterranean Clams Ruditapes decussatus

This study aims to evaluate the toxicity of ZnS nanoparticles (ZnS NP50 = 50 µg/L and ZnS NP100 = 100 µg/L) and diethyl (3-cyano-1-hydroxy-2-methyl-1-phenylpropyl)phosphonate or P (P50 = 50 µg/L and P100 = 100 µg/L) in the clams Ruditapes decussatus using chemical and biochemical approaches. The results demonstrated that clams accumulate ZnS NPs and other metallic elements following exposure. Moreover, ZnS NPs and P separately lead to ROS overproduction, while a mixture of both contaminants has no effect. In addition, data showed that exposure to P100 resulted in increased levels of oxidative stress enzyme activities catalase (CAT) in the gills and digestive glands. A similar trend was also observed in the digestive glands of clams treated with ZnS100. In contrast, CAT activity was decreased in the gills at the same concentration. Exposure to ZnS100 and P100 separately leads to a decrease in acetylcholinesterase (AChE) levels in both gills and digestive glands. Thus, AChE and CAT after co-exposure to an environmental mixture of nanoparticles (ZnS100) and phosphonate (P100) did not show any differences between treated and non-treated clams. The outcome of this work certifies the use of biomarkers and chemical assay when estimating the effects of phosphonate and nanoparticles as part of an ecotoxicological assessment program. An exceptional focus was given to the interaction between ZnS NPs and P. The antioxidant activity of P has been demonstrated to have an additive effect on metal accumulation and antagonistic agents against oxidative stress in clams treated with ZnS NPs.

Assessing the effects of silver nanoparticles on the ecophysiology of Gammarus roeseli

Being part of the macrobenthic fauna, gammarids are efficient indicators of contamination of aquatic ecosystems by nanoparticles that are likely to sediment on the bottom. The present study investigates the effects of silver nanoparticles (nAg) on ecophysiological functions in Gammarus roeseli by using a realistic scenario of contamination. Indeed, an experiment was conducted during 72 h, assessing the effects of 5 silver nAg from 10 to 100 nm diluted at concentrations of maximum 5 µg L^-1 in a natural water retrieved from a stream and supplemented with food. The measured endpoints in gammarids were survival, silver concentrations in tissues, consumption of oxygen and ventilation of gills. Additionally, a set of biomarkers of the energetic metabolism was measured. After a 72-h exposure, results showed a concentration-dependent increase of silver levels in G. roeseli that was significant for the smallest nAg size (10 nm). Ecophysiological responses in G. roeseli were affected and the most striking effect was a concentration-dependent increase in oxygen consumption especially for the smallest nAg (10 to 40 nm), whereas ventilation of gills by gammarids was not changed. The potential mechanisms underlying these findings are discussed. Thus, we demonstrated the very low exposure concentration of 0.5 µg L^-1 for the small nAg size led to significant ecophysiological effects reinforcing the need to further investigate subtle effects on nanoparticles on aquatic organisms.

Nano-titanium dioxide induced genotoxicity and histological lesions in a tropical fish model, Nile tilapia (Oreochromis niloticus)

This study evaluated potential genotoxic and histopathological effects of nano-TiO₂ (0.1, 0.5 and 1 mg/L) in Nile tilapia over 7, 14 and 21 days of exposure. Bulk TiO₂ (1 mg/L) along with controls was used for comparison. Comet assay revealed that nano-TiO₂ can induce erythrocytic DNA damage in a concentration dependent manner. However, micronuclei induction was observed only at the lowest concentration. Elevated organ damage indices indicate nano-TiO₂ induced histological alterations in liver and intestine. Severe histological alterations induced by nano-TiO₂ in the fish were necrosis of hepatic parenchyma and intestinal mucosa. Bulk TiO₂ exposure had no effect on the histological structure of the intestine but increased liver damage indices and erythrocytic DNA damage compared to the controls indicating dissolved form of TiO₂ is not biologically inert. More research efforts are needed to generate in vivo toxicity data on realistic levels of nano-TiO₂ and bulk TiO₂ for environmental risk assessments.

Unraveling the joint toxicity of transition-metal dichalcogenides and per- and polyfluoroalkyl substances in aqueous mediums by experimentation, machine learning and molecular dynamics

The environmental fate of transition-metal dichalcogenides (TMDCs) may be further complicated by interacting with existing pollutants, especially per- and polyfluoroalkyl substances (PFAS). However, due to their sheer volume, it is impossible to explore all possible interactions by simply utilizing experimental methods. Herein, we used two model TMDC nanosheets, molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂), and seven PFAS to explore their interactions and subsequent impacts on model cell lines and zebrafish. Utilizing experimental methods and machine learning approaches, we showed that TMDCs-PFAS interactions can pose unique challenges due to their interaction-specific toxicity niches towards cell lines. Further in vivo experiments, together with molecular dynamics simulation, suggested that TMDCs-PFAS interactions in aqueous environments significantly increased their bioaccumulation in zebrafish towards different target organs, mostly due to the differences in loading PFAS. Such enhanced bioaccumulation increased the oxidative stress in zebrafish liver and intestine, as demonstrated by the increased reactive oxygen species (ROS) level and other enzyme activities, which eventually led to obvious histopathological alterations in the liver and intestine. Our study highlights the importance of exploring interactions between emerging and existing contaminants with state-of-art techniques in aqueous environments and its significance in safeguarding aquatic environment health.

Preparation, Characterization, and Environmental Safety Assessment of Dithiocarbazate Loaded Mesoporous Silica Nanoparticles

Dithiocarbazates comprise an important class of Schiff bases with remarkable biological applications due to the imine group present in their structure. However, full exploitation of the biological activity of 3-methyl-5-phenyl-pyrazoline-1-(S-benzyldithiocarbazate) (DTC) is limited due to its easy degradation and poor solubility in aqueous solutions. The loading of DTC into mesoporous silica nanoparticles (MSiNPs) can be an excellent strategy to improve the solubility of DTC in the aqueous medium. Therefore, the main goal of the present work was to design MSiNP-DTC and to evaluate the success of the loading process by measuring its physicochemical properties and evaluating the environmental safety of the new DTC formulation using different aquatic organisms, such as the microalgae Raphidocelis subcapitata, the macrophyte Lemna minor, and the marine bacterium Aliivibrio fischeri. DTC, MSiNP, and MSiNP-DTC concentrations ranging from 8.8 to 150 mg L^-1 were tested for all the species, showing low toxicity against aquatic organisms. Loading DTC into MSiNPs caused a slight increase in the toxicity at the concentrations tested, only allowing for the estimation of the effect concentration causing a 20% reduction in bioluminescence or growth rate (EC₂₀). Therefore, despite the potential of MSiNPs as a drug delivery system (DDS), it is of utmost importance to assess its impact on the safety of the new formulations.

Toxicity of Silver Nanoparticles in the Presence of Zinc Oxide Nanoparticles Differs for Acute and Chronic Exposures in Zebrafish

We assessed the acute toxicity effects (96 h) of silver nanoparticles (Ag NPs) and zinc oxide nanoparticles (ZnO NPs) and chronic (28 d) exposure to Ag NPs, including in combination with ZnO NPs. In the chronic studies, we further assessed the toxicokinetics and bioaccumulation of Ag and the resulting histopathological effects in the gill, intestine, and liver of zebrafish. Co-exposures with ZnO NPs reduced the toxicity of Ag NPs for acute (lethality) but enhanced the toxicity effects (tissue histopathology) for chronic exposures. The histological lesions for both NPs exposures in the gill included necrosis and fusion of lamellae, for the intestine necrosis and degeneration, and in the liver, mainly necrosis. The severity of the histological lesions induced by the Ag NPs was related to the amount of accumulated Ag in the zebrafish organs. The Ag accumulation in different organs was higher in the presence of ZnO NPs in the order of the gill > intestine > liver. Depuration kinetics illustrated the lowest half-life for Ag occurred in the gill and for the combined exposure of Ag with ZnO NPs. Our findings illustrate that in addition to tissue, time, and exposure concentration dependencies, the Ag NPs toxicity can also be influenced by the co-exposure to other NPs (here ZnO NPs), emphasizing the need for more combination exposure effects studies for NPs to more fully understand their potential environmental health risks.

Particle size-dependent effects of silver nanoparticles on swim bladder damage in zebrafish larvae

Particle size-dependent biological effects of silver nanoparticles (AgNPs) are of great interest; however, the mechanism of action of silver ions (Ag⁺) released from AgNPs concerning AgNP particle size remains unclear. Thus, we evaluated the influence of particle size (20, 40, 60, and 80 nm) on the acute 96-h bioaccumulation and toxicity (swim bladder damage) of AgNPs in zebrafish (Danio rerio) larvae, with a focus on the mechanism of action of Ag⁺ released from differently sized AgNPs. The 40- and 60-nm AgNPs were more toxic than the 20- and 80-nm versions in terms of inflammation and oxidative damage to the swim bladder, as indicated by inhibition of type 2 iodothyroxine deiodinase enzyme activity, mitochondrial injury, and reduced 30-50% adenosine triphosphate content. Furthermore, up-regulation and down-regulation of swim bladder development-related gene expression was not observed for pbx1a and anxa5, but up-regulation expression of shha and ihha was observed with no statistical significance. That 20-nm AgNPs were less toxic was attributed to their rapid elimination from larvae in comparison with the elimination of 40-, 60-, and 80-nm AgNPs; thus, less Ag⁺ was released in 20-nm AgNP-exposed larvae. Failed inflation of swim bladders was affected by released Ag⁺ rather than AgNPs themselves. Overall, we reveal the toxicity contribution of Ag⁺ underlying the observed size-dependent effects of AgNPs and provide a scientific basis for comprehensively assessing the ecological risk and biosafety of AgNPs.

Progress on the toxicity of quantum dots to model organism-zebrafish

In vivo toxicological studies are currently necessary to analyze the probable dangers of quantum dots (QDs) to the environment and human safety, due to the fast expansion of QDs in a range of applications. Because of its high fecundity, cost-effectiveness, well-defined developmental phases, and optical transparency, zebrafish has long been considered the "gold standard" for biosafety assessment of chemical substances and pollutants. In this review, the advantages of using zebrafish in QD toxicity assessment were explored. Then, the target organ toxicities such as developmental toxicity, immunotoxicity, cardiovascular toxicity, neurotoxicity, and hepatotoxicity were summarized. The hazardous effects of different QDs, including cadmium-containing QDs like CdTe, CdSe, and CdSe/ZnS, as well as cadmium-free QDs like graphene QDs (GQDs), graphene oxide QDs (GOQDs), and others, were emphasized and described in detail, as well as the underlying mechanisms of QDs generating these effects. Furthermore, general physicochemical parameters determining QD-induced toxicity in zebrafish were introduced, such as chemical composition and surface coating/modification. The limitations and special concerns of using zebrafish in QD toxicity studies were also mentioned. Finally, we predicted that the utilization of high-throughput screening assays and omics, such as transcriptome sequencing, proteomics, and metabolomics will be popular topic in nanotoxicology.

Short-Term Exposure to MPs and DEHP Disrupted Gill Functions in Marine Bivalves

The synergistic impact of microplastics (MPs) and organic pollutants remains poorly understood in the marine environment. This study aimed to assess the toxicity of polypropylene microplastics (PS) and/or di-(2-ethylhexyl) phthalate (DEHP) on marine clams. Both Ruditapes philippinarum and Tegillarca granosa were exposed to PS and DEHP individually and combined at environmentally relevant concentrations for 48 h. The filtration rate, antioxidant enzymes activity, lipid peroxidation, reactive oxygen species accumulation, and histological alterations were evaluated. Our results show that single or co-exposure to MPs and DEHP significantly decreases the filtration rate in both type of clams, but the latter exhibited stronger inhibition effect. Close examination of accumulation of reactive oxygen species and related biomarkers revealed that combined exposure exerts greater oxidative stress in the cells, which causes more serious histopathological damage in the gills of the bivalves. Our study implies that MPs, in synergy with organic pollutants, can be more harmful for marine organisms.

Proteomic evaluation of nanotoxicity in aquatic organisms: A review

The alteration of organisms protein functions by engineered nanoparticles (ENPs) is dependent on the complex interplay between their inherent physicochemical properties (e.g., size, surface coating, shape) and environmental conditions (e.g., pH, organic matter). To date, there is increasing interest on the use of 'omics' approaches, such as proteomics, genomics, and others, to study ENPs-biomolecules interactions in aquatic organisms. However, although proteomics has recently been applied to investigate effects of ENPs and associated mechanisms in aquatic organisms, its use remain limited. Herein, proteomics techniques widely applied to investigate ENPs-protein interactions in aquatic organisms are reviewed. Data demonstrates that 2DE and mass spectrometry and/or their combination, thereof, are the most suitable techniques to elucidate ENPs-protein interactions. Furthermore, current status on ENPs and protein interactions, and possible mechanisms of nanotoxicity with emphasis on those that exert influence at protein expression levels, and key influencing factors on ENPs-proteins interactions are outlined. Most reported studies were done using synthetic media and essay protocols and had wide variability (not standardized); this may consequently limit data application in actual environmental systems. Therefore, there is a need for studies using realistic environmental concentrations of ENPs, and actual environmental matrixes (e.g., surface water) to aid better model development of ENPs-proteins interactions in aquatic systems.

Impact of synthetic silver nanoparticles on the biofilm microbial communities and wastewater treatment efficiency in experimental hybrid filter system treating municipal wastewater

Silver nanoparticles (AgNPs) threaten human and ecosystem health, and are among the most widely used engineered nanomaterials that reach wastewater during production, usage, and disposal phases. This study evaluated the effect of a 100-fold increase in collargol (protein-coated AgNP) and Ag⁺ ions concentrations in municipal wastewater on the microbial community composition of the filter material biofilms (FMB) and the purification efficiency of the hybrid treatment system consisting of vertical (VF) and horizontal (HF) subsurface flow filters. We found that increased amounts of collargol and AgNO₃ in wastewater had a modest effect on the prokaryotic community composition in FMB and did not significantly affect the performance of the studied system. Regardless of how Ag was introduced, 99.9% of it was removed by the system. AgNPs and AgNO₃ concentrations did not significantly affect the purification efficiency of the system. AgNO₃ induced a higher increase in the genetic potential of certain Ag resistance mechanisms in VFs than collargol; however, the increase in Ag resistance potential was similar for both substances in HF. Hence, the microbial community composition in biofilms of vertical and horizontal flow filters is largely resistant, resilient, or functionally redundant in response to AgNPs addition in the form of collargol.

Effects of wastewater-spiked nanoparticles of silver and titanium dioxide on survival, growth, reproduction and biochemical markers of Daphnia magna

Silver (Ag) and titanium dioxide (TiO₂) nanoparticles (NPs) are released into aquatic environments through wastewater treatment plants (WWTPs). Even though these NPs are mostly retained in WWTPs, a small fraction can be found in released effluents and may exert toxic effects on aquatic biota. Currently, the available information about the sublethal effects of wastewater-borne NPs on aquatic organisms is inconclusive and the importance of exposure media remains poorly understood. Previously, we demonstrated that rainbow trout juveniles chronically exposed to wastewater-borne AgNPs or TiO₂NPs caused no effects on growth, but antioxidative stress mechanisms were triggered in fish organs. Accordingly, this study aimed to: (i) assess the chronic (21-d) effects of wastewater-borne AgNPs (0.3-23.5 μg L^-1 Ag) and TiO₂NPs (2.7-3.9 μg L^-1 Ti) on survival, growth and reproduction of Daphnia magna; (ii) determine the short-term (96-h) effects of wastewater-borne AgNPs (30.3 μg L^-1 Ag) and TiO₂NPs (6.3 μg L^-1 Ti) at the subcellular level (biochemical markers of neurotoxicity, anaerobic metabolism and oxidative stress); and (iii) compare the effects obtained in (i) and (ii) with the corresponding ones induced by effluent-supplemented and water-dispersed NPs. Total Ag and Ti levels were analytically quantified in all treatments. It was demonstrated that both wastewater-borne NPs are considered non-toxic to daphnids at tested concentrations, considering the endpoints at the individual (survival, growth, reproduction) and subcellular (biochemical markers) levels. Contrarily, when pristine forms of NPs were supplemented to effluents or water, concentration-dependent effects were noticed, particularly on cumulative offspring of daphnids. The significant effects on anaerobic metabolism and detoxification pathways caused by the effluent indicate background toxicity. Bearing in mind the achievement of a suitable risk assessment of NPs in aquatic environments, this combined approach looking at both the individual and subcellular levels responses come up with relevant information about the ecotoxicological harmlessness of wastewater-borne NPs in complex environmental matrices like WWTP effluents.

Copper uptake kinetics and toxicological effects of ionic Cu and CuO nanoparticles on the seaweed Ulva rigida

Copper ion (Cu²⁺) and copper oxide (CuO) nanoparticle (NP) ecotoxicity are of increasing concern as they are considered to be a potential risk to marine systems. This study represents the first attempt to evaluate CuO NP impacts on the seaweeds and Cu²⁺ on the chlorophyte Ulva rigida. Effects on oxidative stress, antioxidant defence markers, photosystem II function, thalli growth, and cell viability in U. rigida exposed for 4 up 72 h to1 and 5 mg L^-1 Cu²⁺ and CuO NPs were examined. Hydrogen peroxide (H₂O₂) generation, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, and growth inhibition seemed to be reliable and early warning markers of toxicity. The most important variables of the principal component analysis (PCA): H₂O₂ generation, antioxidant stress markers, and growth-based toxicity index, were higher at 1 mg L^-1 CuO NPs compared to CuSO₄ and at 5 mg L^-1 CuSO₄ compared to CuO NPs. Intracellular uptake kinetics fit well to the Michaelis-Menten equation. The higher toxicity at 5 mg L^-1 CuSO₄ compared to 1 mg L^-1 was due to the higher Cu uptake with increasing concentration, suggesting and higher accumulation ability. On the contrary, 1 mg L^-1 CuO NPs induced more strongly toxicity effects than 5 mg L^-1. The relatively stronger effect of CuO NPs at 1 mg L^-1 than the respective CuSO₄ concentration could be attributed to the higher rate of initial uptake (V_c) and the mean rate of Cu uptake [C_max/(2 × K_m)] at CuO NP treatment. The intracellular seaweed experimental threshold of Cu, which coincided with the onset of oxidative stress, was within the Cu concentration range recorded in Mediterranean Ulva spp., indicating that it may pose a substantial risk to marine environments.

Evaluation of Maghemite Nanoparticles-Induced Developmental Toxicity and Oxidative Stress in Zebrafish Embryos/Larvae

Maghemite nanoparticles ([Formula: see text] NPs) have a wide array of applications in various industries including biomedical field. There is an absence of legislation globally for the regulation of the production, use, and disposal of such NPs as they are eventually dumped into the environment where these NPs might affect the living systems. This study evaluates the effect of the [Formula: see text] NP-induced developmental toxicity in zebrafish embryos/larvae. The commercially available Fe₂O₃ NPs were purchased, and zebrafish embryos toxicity test was done by exposing embryos to various concentrations of [Formula: see text] NPs at 1 hpf and analyzed at 96 hpf. Based on the LC₅₀ value (60.17 ppm), the sub-lethal concentrations of 40 and 60 ppm were used for further experiments. Hatching, lethality, developmental malformations, and heartbeat rate were measured in the control and treated embryos/larvae. The ionic Fe content in the media, and the larvae was quantified using ICP-MS and AAS. The biomolecular alterations in the control and treated groups were analyzed using FT-IR. The Fe ions present in the larvae were visualized using SEM-EDXS. In situ detection of AChE and apoptotic bodies was done using staining techniques. Biochemical markers (total protein content, AChE, and Na⁺ K⁺-ATPase) along with oxidants and antioxidants were assessed. A significant decrease in the heartbeat rate and hatching delay was observed in the treated groups affecting the developmental processes. Teratogenic analysis showed increased developmental deformity incidence in treated groups in a dose-dependent manner. The accumulation of Fe was evidenced from the ICP-MS, AAS, and SEM-EDXS. Alterations in AChE and Na⁺ K⁺-ATPase activity were observed along with an increment in the oxidants level with a concomitant decrease in antioxidant enzymes. These results show [Formula: see text] NP exposure leads to developmental malformation and results in the alteration of redox homeostasis.

Building the Bridge From Aquatic Nanotoxicology to Safety by Design Silver Nanoparticles

Nanotechnologies have rapidly grown, and they are considered the new industrial revolution. However, the augmented production and wide applications of engineered nanomaterials (ENMs) and nanoparticles (NPs) inevitably lead to environmental exposure with consequences on human and environmental health. Engineered nanomaterial and nanoparticle (ENM/P) effects on humans and the environment are complex and largely depend on the interplay between their peculiar properties such as size, shape, coating, surface charge, and degree of agglomeration or aggregation and those of the receiving media/body. These rebounds on ENM/P safety and newly developed concepts such as the safety by design are gaining importance in the field of sustainable nanotechnologies. This article aims to review the critical characteristics of the ENM/Ps that need to be addressed in the safe by design process to develop ENM/Ps with the ablility to reduce/minimize any potential toxicological risks for living beings associated with their exposure. Specifically, we focused on silver nanoparticles (AgNPs) due to an increasing number of nanoproducts containing AgNPs, as well as an increasing knowledge about these nanomaterials (NMs) and their effects. We review the ecotoxicological effects documented on freshwater and marine species that demonstrate the importance of the relationship between the ENM/P design and their biological outcomes in terms of environmental safety.

Toxicity of α-Ag2WO4 microcrystals to freshwater microalga Raphidocelis subcapitata at cellular and population levels

Silver-based materials have microbicidal action, photocatalytic activity and electronic properties. The increase in manufacturing and consumption of these compounds, given their wide functionality and application, is a source of contamination to freshwater ecosystems and causes toxicity to aquatic biota. Therefore, for the first time, we evaluated the toxicity of the silver tungstate (α-Ag₂WO₄), in different morphologies (cube and rod), for the microalga Raphidocelis subcapitata. To investigate the toxicity, we evaluated the growth rate, cell complexity and size, reactive oxygen species (ROS) production and chlorophyll a (Chl a) fluorescence. The α-Ag₂WO₄ - R (rod) was 1.7 times more toxic than α-Ag₂WO₄-C (cube), with IC₁₀ and IC₅₀ values of, respectively, 8.68 ± 0.91 μg L^-1 and 13.72 ± 1.48 μg L^-1 for α-Ag₂WO₄ - R and 18.60 ± 1.61 μg L^-1 and 23.47 ± 1.16 μg L^-1 for α-Ag₂WO₄-C. The release of silver ions was quantified and indicated that the silver ions dissolution from the α-Ag₂WO₄ - R ranged from 34 to 71%, while the Ag ions from the α-Ag₂WO₄-C varied from 35 to 97%. The α-Ag₂WO₄-C induced, after 24 h exposure, the increase of ROS at the lowest concentrations (8.81 and 19.32 μg L^-1), whereas the α-Ag₂WO₄ - R significantly induced ROS production at 96 h at the highest concentration (31.76 μg L^-1). Both microcrystal shapes significantly altered the cellular complexity and decreased the Chl a fluorescence at all tested concentrations. We conclude that the different morphologies of α-Ag₂WO₄ negatively affect the microalga and are important sources of silver ions leading to harmful consequences to the aquatic ecosystem.

Dietary exposure of zinc oxide nanoparticles (ZnO-NPs) from canned seafood by single particle ICP-MS: Balancing of risks and benefits for human health

The present study aims to give information regarding the quantification of ZnO-NPs in canned seafood, which may be intentionally or unintentionally added, and to provide a first esteem of dietary exposure. Samples were subjected to an alkaline digestion and assessment of ZnO-NPs was performed by the single particle ICP-MS technique. ZnO-NPs were found with concentrations range from 0.003 to 0.010 mg/kg and a size mean range from 61.3 and 78.6 nm. It was not observed a clear bioaccumulation trend according to trophic level and size of seafood species, although the mollusk species has slightly higher concentrations and larger size. The number of ZnO-NPs/g does not differ significantly among food samples, observing an average range of 5.51 × 10⁶ - 9.97 × 10⁶. Dissolved Zn determined with spICP-MS revealed comparable concentration to total Zn determined with ICP-MS in standard mode, confirming the efficiency of alkaline digestion on the extraction of the Zn. The same accumulation trend found for ZnO-NPs was observed more clearly for dissolved Zn. The ZnO-NPs intake derived from a meal does not differ significantly among seafood products and it ranges from 0.010 to 0.031 µg/kg b.w. in adult, and from 0.022 to 0.067 µg/kg b.w. in child. Conversely, the intake of dissolved Zn is significantly higher if it is assumed a meal of mollusks versus the fish products, with values of 109.3 µg/kg b.w. for adult and 240.1 µg/kg b.w. for child. Our findings revealed that ZnO-NPs have the potential to bioaccumulate in marine organisms, and seafood could be an important uptake route of ZnO-NPs. These results could be a first important step to understand the ZnO-NPs human dietary exposure, but the characterization and quantification of ZnO-NPs is necessary for a large number of food items.

Inhibition of wastewater pollutants on the anammox process: A review

The anaerobic ammonium oxidation (anammox) process has been recognized as an efficient nitrogen removal technology. However, anammox bacteria are susceptible to surrounding environments and different pollutants, which limits the extensive application of the anammox process worldwide. Numerous researchers investigate the effects of various pollutants on the anammox process or bacteria, and related findings have also been reviewed with the focused on their inhibitory effects on process performance and microbial community. This review systemically summarized the recent advances in the inhibition, mechanism and recovery process of traditional and emerging pollutants on the anammox process over a decade, such as organics, metals, antibiotics, nanoparticles, etc. Generally, low-concentration pollutants exhibited a promotion on the anammox activity, while high-concentration pollutants showed inhibitory effects. The inhibitory threshold concentration of different pollutants varied. The combined effects of multipollutant also attracts more attentions, including synergistic, antagonistic and independent effects. Additionally, remaining problems and research needs are further proposed. This review provides a foundation for future research on the inhibition in anammox process, and promotes the proper operation of anammox processes treating different types of wastewaters.

Impacts of nanoparticles and phosphonates in the behavior and oxidative status of the mediterranean mussels (Mytilus galloprovincialis)

The current study investigated the exposure of the Mediterranean mussel (Mytilus galloprovincialis) to gold nanoparticles decorated zinc oxide (Au-ZnO NPs) and phosphonate [Diethyl (3-cyano-1-hydroxy-1-phenyl-2-methylpropyl)] phosphate (PC). The mussels were exposed to concentrations of 50 and 100 µg L^-1 of both compounds alone, as well as to a mixture of both pollutants (i.e. Mix). The singular and the combined effect of each pollutant was investigated by measuring the concentration of various metals (i.e., Cu, Fe, Mn, Zn and Au) in the the digestive glands and gills of mussels, their filtration capacity (FC), respiration rate (RR) and the response of oxidative biomarkers, respectively, following 14 days of exposure. The concentrations of Cu, Fe, Mn, Zn and Au increased directly with Au-ZnO NPs in mussel tissues, but significantly only for Zn. In contrast, the mixture of Au-ZnO100 NPs and PC100 did not induce any significant increase in the content of metals in digetsve glands and gills, suggesting antagonistic interactions between contaminants. In addition, FC and RR levels decreased following exposure to Au-ZnO100 NPs and PC100 treatments and no significant alterations were observed after the exposure to 50 µg.L^-1 of both contaminants and Mix. Hydrogen peroxide (H₂O₂) level, GSH/GSSG ratio, superoxide dismutase (SOD), catalase (CAT) and acetylcholinesterase (AChE) activities showed significant changes following the exposure to both Au-ZnO NPs and PC, in the gills and the digestive glands of the mussel. However, no significant modifications were observed in both organs following the exposure to Mix. The current study advances the understanding of the toxicity of NPs and phosphonates on M. galloprovincialis and sets the path for future ecotoxicological studies regarding the synergic effects of these substances on marine species. Moreover, the current experiment suggests that the oxidative stress and the neurotoxic pathways are responsive following the exposure of marine invertebrates to both nanoparticles and phosphonates, with potential antagonist interactions of these substances on the physiology of targeted species.

Toxicity of Titanium Dioxide Nanoparticles to Tadpoles of Asian Common Toad (Duttaphrynus melanostictus) Following Short Term and Chronic Exposures

Nanotoxicity data for amphibians are limited compared to other taxonomic groups. The present study assessed toxicity of titanium dioxide nanoparticles (nanoTiO₂, anatase form, particle size < 25 nm) on tadpoles of Duttaphrynus melanostictus after short term and chronic exposures. Exposure to nanoTiO₂ (≤ 100 mg/L) for 96 h had no significant effect on survival but upon transfer to nanoTiO₂ free water for another 21 days, survival of the tadpoles pre-exposed to nanoTiO₂ was greatly reduced and their development was delayed. Chronic exposure to nanoTiO₂ (0.1 to 10 mg/L) for 14 days had no significant effects on acetylcholinesterase activities but induced mortalities (up to 40%) and histological alterations in the intestine and liver tissues. The results indicate that release of nanoTiO₂ to aquatic ecosystems could pose negative impacts to amphibian populations.

Interaction Effect of EDTA, Salinity, and Oxide Nanoparticles on Alga Chlamydomonas reinhardtii and Chlamydomonas euryale

The interaction effects of organic ligand ethylene diamine tetra-acetic acid (EDTA) and oxide nanoparticles (magnetite Fe₃O₄-NPs and copper CuO-NPs) were investigated during a 72 h period on two green algal species-Chlamydomonas reinhardtii under freshwater conditions and Chlamydomonas euryale under saltwater conditions. Fe₃O₄-NPs had larger agglomerates and very low solubility. CuO-NPs, having smaller agglomerates and higher solubility, were more toxic than Fe₃O₄-NPs in freshwater conditions for similar mass-based concentrations, especially at 72 h under 100 mg L^-1. Furthermore, the effect of EDTA increased nanoparticle solubility, and the salinity caused a decrease in their solubility. Our results on C. euryale showed that the increase in salinity to 32 g L^-1 caused the formation of larger nanoparticle agglomerates, leading to a decrease in the toxicity impact on algal cells. In addition, EDTA treatments induced a toxicity effect on both freshwater and saltwater Chlamydomonas species, by altering the nutrient uptake of algal cells. However, C. euryale was more resistant to EDTA toxicity than C. reinhardtii. Moreover, nanoparticle treatments caused a reduction in EDTA toxicity, especially for CuO-NPs. Therefore, the toxicity impact caused by these environmental factors should be considered in risk assessment for metallic nanoparticles.

Integration of transcriptomics and metabolomics reveals damage and recovery mechanisms of fish gills in response to nanosilver exposure

Toxic effects of silver nanoparticles (AgNPs) on fish gills have been widely reported but the recoverability of AgNPs-induced fish gill injuries is still unknown. In this study, combined multiomics and conventional toxicological analytical methods were used to investigate the changes in the gills of common carp responses to AgNPs (0.1 mg/L) toxicity after 24 h exposure and 7-day recovery. Conventional toxicological results showed that AgNPs exposure significantly increased silver content in gills and caused epithelial hyperplasia and lamellar fusion. After the recovery period, the silver content in fish gills significantly decreased; accompanied by the disappearance of histopathological characteristics in fish gills. Multiomics results revealed that AgNPs exposure resulted in the differential expression of 687 genes and 96 metabolites in fish gills. These differentially expressed genes (DEGs) and metabolites mainly participate in amino acid, carbohydrate, and lipid metabolisms, and are significantly enriched in the tricarboxylic acid (TCA) cycle. After the recovery period, the number of DEGs and metabolites in gills decreased to 33 and 90, respectively. Moreover, DEGs and metabolites in the TCA cycle recovered to control levels. In summary, the present study found that AgNPs-induced fish gill toxicity showed potential recoverability at molecular and phenotype levels.

Comparison of biomarker responses after acute and chronic bioassays in Lumbriculus variegatus

Differential biomarker responses may occur after acute or chronic bioassays when animals are unfed. In many aquatic species, food deprivation may lead to a pro-oxidant condition. However, information about its effects on the oligochaete Lumbriculus variegatus, a bioindicator organism for water and sediment toxicity tests, is almost completely lacking. Acute (48 h) and chronic (21 days) bioassays were performed using unfed L. variegatus to assess the impact of food deprivation on several biomarkers related to the redox cellular status. Results showed that food deprivation inhibited the antioxidant enzymes superoxide dismutase and catalase, whilst levels of total glutathione (t-GSH) and lipid peroxidation processes increased with respect to controls. The same biomarkers were evaluated in unfed organisms exposed to tributyltin (TBT), nano-goethite or a binary mixture of both, for 48 h and 21 days. After 48 h, the organisms were able to cope with chemical stressors by enhancing antioxidant defences and lipid peroxidation processes were not observed. After 21 days, both TBT and the binary mixture induced the most noxious effects. At this time, the antioxidant enzymatic defences were still higher than controls, but levels of t-GSH were significantly decreased and lipid peroxidation was found. Therefore, differential biomarker responses were observed between starved organisms for 21 days and those simultaneously exposed to other chemical stressors. The activity of the enzyme acetylcholinesterase was also determined, but it remained unchanged in all cases.

The impacts of metal-based engineered nanomaterial mixtures on microbial systems: A review

The last decade has witnessed tremendous growth in the commercial use of metal-based engineered nanomaterials (ENMs) for a wide range of products and processes. Consequently, direct and indirect release into environmental systems may no longer be considered negligible or insignificant. Yet, there is an active debate as to whether there are real risks to human or ecological health with environmental exposure to ENMs. Previous research has focused primarily on the acute effects of individual ENMs using pure cultures under controlled laboratory environments, which may not accurately reveal the ecological impacts of ENMs under real environmental conditions. The goal of this review is to assess our current understanding of ENM effects as we move from exposure of single to multiple ENMs or microbial species. For instance, are ENMs' impacts on microbial communities predicted by their intrinsic physical or chemical characteristics or their effects on single microbial populations; how do chronic ENM interactions compare to acute toxicity; does behavior under simplified laboratory conditions reflect that in environmental media; finally, is biological stress modified by interactions in ENM mixtures relative to that of individual ENM? This review summarizes key findings and our evolving understanding of the ecological effects of ENMs under complex environmental conditions on microbial systems, identifies the gaps in our current knowledge, and indicates the direction of future research.

Toxicity of boron and vanadium nanoparticles on Danio rerio embryos - Phenotypical, biochemical, and behavioral alterations

Engineered nanoparticles (NPs) are emerging contaminants of concern and it is important to understand their environmental behavior and ecological risks to exposed organisms. Despite their ubiquitous presence in the environment, there is little information about the hazards of certain NPs, such as boron (BNPs) and vanadium (VNPs). The aim of the present research was to investigate the effects of commercial BNPs and VNPs (80 to 100 nm) to zebrafish embryos, at different levels of biological organization. A range of nominal concentrations for both NPs (0, 0.01, 0.1, 1, and 10 mg/L) was tested. Due to the presence of triton X-100 in the NPs' stock dispersions, an additional control group was included (0.001% triton X-100). Survival, hatching, and malformations of embryos were assessed for 96 hours (h) exposure. Locomotor behavior was evaluated at 120 h. Furthermore, embryos were exposed to 0, 1, and 10 mg/L of NPs to evaluate a set of biomarker responses after 96 h: cholinesterase (ChE) and glutathione S-transferase (GST) activities, total glutathione (TG) and energy budgets levels. VNPs induced malformations (10 mg/L), hyperactivity (10 mg/L), erratic swimming (0.01 mg/L), altered swimming pattern (>0.01 mg/L), delayed hatching (10 mg/L) and altered biochemical responses involved in antioxidant defense (GST and TG at >1 mg/L), neurotransmission (ChE at 10 mg/L) and energy metabolism (lipids at >1 mg/L and carbohydrates at 10 mg/L). BNPs caused malformations (10 mg/L), affected swimming pattern (>0.01 mg/L), induced erratic swimming (10 mg/L) and decreased TG content and GST activity (>1 mg/L). At the same concentrations, VNPs affected a greater number of endpoints than BNPs, demonstrating a greater toxicity to zebrafish embryos. The present study shows that BNPs and VNPs may affect aquatic organisms, albeit at relatively great non-environmentally relevant concentrations, reinforcing the importance of the risk assessment of different NPs.

Toxicity of Zinc Oxide Nanoparticles on the Embryo of Javanese Medaka (Oryzias javanicus Bleeker, 1854): A Comparative Study

Simple Summary

In recent years, the production and distribution of ZnO NPs have gradually increased. As the number of ZnO NPs containing products grows, and the release of these products into the environment—particularly to the aquatic environment—has increased, several questions about their toxic effects on aquatic organisms have arisen. In this study, we explore the embryotoxicity of ZnO NPs by using the newly introduced model organism Oryzias javanicus (Javanese medaka). We found that the 96 h LC₅₀ of ZnO NPs on the embryo of Javanese medaka were 0.643 mg/L, 1.333 mg/L, and 2.370 mg/L in ultra-pure, deionized, and dechlorinated tap water. The toxicity of ZnO NPs increased as both the concentration and time of exposure increased. The results of this study demonstrate that ZnO NPs are extremely toxic for the early life stage of Javanese medaka.

Abstract

(1) Background: Zinc oxide nanoparticles (ZnO NPs) are widely applied in various human products. However, they can be extremely toxic for aquatic organisms, particularly fish. This research was conducted to determine the LC₅₀ of ZnO NPs on the embryos of Javanese medaka (Oryzias javanicus) in ultra-pure, deionized, and dechlorinated tap water; (2) Methods: The experiments were conducted in a completely randomized design (CRD) with three replicates for six treatments for acute (0.100, 0.250, 0.500, 1.00, 5.00, and 10.00 mg/L) exposures for each type of water; (3) Results: The LC₅₀ of ZnO NPs at 96 h was determined as 0.643 mg/L in ultra-pure water, 1.333 mg/L in deionized water, and 2.370 in dechlorinated tap water. In addition to concentration-dependent toxicity, we also observed time-dependent toxicity for ZnO NPs. In addition, the sizes of ZnO NPs increased immediately after dispersion and were 1079 nm, 3209 nm, and 3652 nm in ultra-pure, deionized, and dechlorinated tap water. The highest concentration of measured Zn²⁺ in exposure concentrations was found in ultra-pure water, followed by deionized and dechlorinated tap water suspensions. Furthermore, Javanese medaka showed high sensitivity to acute exposure of ZnO NPs in all types of water.

Study on the impacts of chemical and green synthesized (Leucas aspera and oxy-cyclodextrin complex) dietary zinc oxide nanoparticles in Nile tilapia (Oreochromis niloticus)

The present study was designed to evaluate the health effects of dietary nanozinc prepared by two methods: conventional chemical method and green method. The parameters evaluated were the extent of bioaccumulation, antioxidant status, histological, immunological changes and DNA damage in Nile tilapia fed nanozinc feed. Zinc oxide nanoparticles were first prepared by green and chemical methods. Before feed preparation, the in vitro antioxidant activity and antibacterial activity of both types of nanoparticle solutions were tested and the results revealed enhanced activities in green synthesized ZnO NP solution. After the acclimatization period, 420 Nile tilapias were distributed randomly into 21 glass tanks with 20 fish per tank in triplicates. Fish were fed control diet without any ZnO NP and (i) GT1-green synthesized ZnO NP diet at 100 mg/kg, (ii) CT1-chemically synthesized ZnO NP diet at 100 mg/kg, (iii) GT2-green synthesized ZnO NP diet at 200 mg/kg, (iv) CT2-chemically synthesized ZnO NP diet at 200 mg/kg, (v) GT3-green synthesized ZnO NP diet at 400 mg/kg and (vi) CT3-chemically synthesized ZnO NP diet at 400 mg/kg for 60 days. After 60 days, gill and liver samples were collected for analysing oxidative stress, histopathological alterations and bioaccumulation of zinc, whereas serum samples were collected for evaluating immune response. The results revealed that the GT3 diet significantly (P < 0.05) enhanced the level of antioxidant enzymes (CAT, SOD, GPx, GR and GSH) than dietary nanozinc prepared by the chemical method. Similarly, the innate immunological parameters were significantly (P < 0.05) augmented in fish fed GT3 diet. Comparative histological study of liver and gill tissues revealed normal architecture in the tissues of fish fed green synthesized NP-enriched feed, whereas the tissues of fish fed chemically synthesized NP feed exhibited histological alterations. Bioaccumulation of zinc was more in the liver followed by the muscle and least in the gills and DNA damage was more evident in fish fed chemically synthesized ZnO NP-enriched feed. In conclusion, the results suggest that the inclusion of 400 mg/kg GT3 diet in fish diet enhanced the level of antioxidant enzymes, boosted immune response and did not cause histological damage to organs, and therefore, GT3 nanofeed can be recommended for fish health improvement.

Chemically and Green Synthesized ZnO Nanoparticles Alter Key Immunological Molecules in Common Carp (Cyprinus carpio) Skin Mucus

This study was conducted to compare the effects of commercially available (C) and green synthesized (GS) Zinc oxide nanoparticles (ZnO-NPs) on immunological responses of common carp (Cyprinus carpio) skin mucus. GS ZnO-NPs were generated using Thymus pubescent and characterized by UV–vis diffuse reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX). Fish (n = 150) were randomly allocated into five groups in triplicate and received a waterborne concentration of 0% (control), 25%, and 50% of LC50 96 h of commercially available (C1 and C2) and green synthesized ZnO-NPs (GS1 and GS2) for 21 days. Results from XRD displayed ZnO-NPs with 58 nm in size and UV-vis DRS, EDX, and FT-IR analysis showed that some functional groups from plant extract bonded to the surface of NPs. The SEM images showed that ZnO-NPs have conical morphology. Acute toxicity study showed a higher dose of LC50_96h for green synthesized ZnO-NPs (78.9 mg.L⁻¹) compared to the commercial source (59.95 mg.L⁻¹). The highest activity of lysozyme and alternative complement activity (ACH50) were found in control and GS1 groups. A significant decrease in alkaline phosphatase activity (ALP) was found in C1 and C2 groups compared to other treatments. Protease activity (P) was significantly decreased in the C2 group compared to the control and GS groups. Total immunoglobulin (total Ig) content was the highest in the control. In addition, total Ig in the GS1 group was higher than GS2. The exposure to ZnO-NPs lowered total protein content in all experimental groups when compared to control. Present findings revealed lower induced immunosuppressive effects by green synthesized ZnO-NPs on key parameters of fish skin mucus.

Sub-chronic effects of AgNPs and AuNPs on Gammarus fossarum (Crustacea Amphipoda): From molecular to behavioural responses

The aim of the present study was the assessment of the sub-chronic effects of silver (AgNPs) and gold nanoparticles (AuNPs) of 40 nm primary size either stabilised with citrate (CIT) or coated with polyethylene glycol (PEG) on the freshwater invertebrate Gammarus fossarum. Silver nitrate (AgNO₃) was used as a positive control in order to study the contribution of silver ions potentially released from AgNPs on the observed effects. A multibiomarker approach was used to assess the long-term effects of AgNPs and AuNPs 40 nm on molecular, cellular, physiological and behavioural responses of G. fossarum. Specimen of G. fossarum were exposed for 15 days to 0.5 and 5 µgL^-1 of CIT and PEG AgNPs and AuNPs 40 nm in the presence of food. A significant uptake of both Ag and Au was observed in exposed animals but was under the toxic threshold leading to mortality of G. fossarum. Silver nanoparticles (CIT-AgNPs and PEG-AgNPs 40 nm) led to an up-regulation of Na⁺K⁺ATPase gene expression. An up-regulation of Catalse and Chitinase gene expressions due to exposure to PEG-AgNPs 40 nm was also observed. Gold nanoparticles (CIT and PEG-AuNPs 40 nm) led to an increase of CuZnSOD gene expression. Furthermore, both AgNPs and AuNPs led to a more developed digestive lysosomal system indicating a general stress response in G. fossarum. Both AgNPs and AuNPs 40 nm significantly affected locomotor activity of G. fossarum while no effects were observed on haemolymphatic ions and ventilation.

Harmful effects of metal(loid) oxide nanoparticles

Abstract

The incorporation of nanomaterials (NMs), including metal(loid) oxide (MOx) nanoparticles (NPs), in the most diversified consumer products, has grown enormously in recent decades. Consequently, the contact between humans and these materials increased, as well as their presence in the environment. This fact has raised concerns and uncertainties about the possible risks of NMs to human health and the adverse effects on the environment. These concerns underline the need and importance of assessing its nanosecurity. The present review focuses on the main mechanisms underlying the MOx NPs toxicity, illustrated with different biological models: release of toxic ions, cellular uptake of NPs, oxidative stress, shading effect on photosynthetic microorganisms, physical restrain and damage of cell wall. Additionally, the biological models used to evaluate the potential hazardous of nanomaterials are briefly presented, with particular emphasis on the yeast Saccharomyces cerevisiae, as an alternative model in nanotoxicology. An overview containing recent scientific advances on cellular responses (toxic symptoms exhibited by yeasts) resulting from the interaction with MOx NPs (inhibition of cell proliferation, cell wall damage, alteration of function and morphology of organelles, presence of oxidative stress bio-indicators, gene expression changes, genotoxicity and cell dead) is critically presented. The elucidation of the toxic modes of action of MOx NPs in yeast cells can be very useful in providing additional clues about the impact of NPs on the physiology and metabolism of the eukaryotic cell. Current and future trends of MOx NPs toxicity, regarding their possible impacts on the environment and human health, are discussed.

Key points

• The potential hazardous effects of MOx NPs are critically reviewed.

• An overview of the main mechanisms associated with MOx NPs toxicity is presented.

• Scientific advances about yeast cell responses to MOx NPs are updated and discussed.

Environmental concentrations of copper nanoparticles affect vital functions in Ankistrodesmus densus

Nanoparticles (NPs) have unique properties, leading to their widespread application in industry, consequently increasing their concentration in aquatic ecosystems. Although environmentally significant concentrations are still low, they tend to increase because of the intense use, posing into risk microalgae communities. Microalgae are primary producers that support food chains in aquatic ecosystems; thus factors that interfere with their physiology can be propagated throughout the food web. The present research investigated the effects of copper nanoparticles (Cu-NPs) in the physiology of a cosmopolitan green microalgae, Ankistrodesmus densus. Here, we focused on environmental NPs levels, so an ample Cu-NPs range was used, 0.3-635 μg L^-1. Considering that NPs dissolve into the medium releasing their constituent material, free Cu²⁺ ions were determined and considered as surrogate for NPs concentration, which varied from 2.1 × 10^-9 to 8.4 × 10^-9 mol L^-1. The experiment was based in 72 h Cu-NPs exposure, and to access the physiology of A. densus, we monitored population growth, photochemistry of photosynthesis and the content of cell biomolecules (total proteins, carbohydrates and lipids). The results showed that 2.1 × 10^-9 mol L^-1 free Cu²⁺ was enough to decrease growth rate, but 2.5x higher Cu was necessary to affect the photosynthetic parameters. Inorganic carbon fixation rate calculated by absolute electron transport rates was affected. Considering cell biomolecules, total proteins accumulated at 6.5 × 10^-9 and kept increasing up to 8.4 × 10^-9 mol L^-1 free Cu²⁺. Because this was not related to biomass formation, we suggest a possible association with cell detoxification mechanisms. The most clear finding that emerged from this study is that environmental Cu-NPs concentrations affect vital functions in the green microalgae A. densus. An implication of this is the possibility of facing problems related to a increase of NPs in aquatic ecosystems in the near future.

Effects of ferroelectric oxides of barium strontium titanate (Ba0.85Sr0.15TiO3) nanoparticles on Ruditapes decussatus assessed through chemical, physiological, and biochemical methods

Here, the effects of a newly designed ferroelectric oxide synthesized by solid reaction, barium strontium titanate [BST (85/15)] (Ba_0.85Sr_0.15TiO₃), on the carpet shell clam Ruditapes decussatus were investigated. These clams were exposed to four concentrations of BST (85/15) nanoparticles (0.001, 0.01, 0.1, and 1 mg.L^-1), and BST (85/15) was absorbed by R. decussatus in an exposure intensity-dependent manner. Measurements of clearance rate and biomarkers confirmed that the nanoparticles significantly affected the health of clams in an organ-dependent manner. Interestingly, BST (85/15) nanoparticles stimulated acetylcholinesterase (AChE) activity in the clams, suggesting their usefulness as antagonists of AChE inhibiting pollutants. These findings demonstrate the suitability of R. decussatus as a test organism to provide a framework for understanding the toxicological effects of these newly designed ferroelectrics. Moreover, concentrations of BST (85/15) < 0.1 mg.L^-1 could be good alternatives to lead-based ferroelectric oxides and could be sustainable tools for use in electronic applications.

Antioxidant responses of the mussel Mytilus coruscus co-exposed to ocean acidification, hypoxia and warming

In the present study, the combined effects of pH, dissolved oxygen (DO) and temperature levels on the antioxidant responses of the mussel Mytilus coruscus were evaluated. Mussels were exposed to two pH (8.1, 7.7-acidification), two DO (6 mg L^-1, 2 mg L^-1-hypoxia) and two temperature levels (20 °C, 30 °C-warming) for 30 days. SOD, CAT, MDA, GPx, GSH, GST, TAOC, AKP, ACP, GPT, AST levels were measured in the gills of mussels. All tested biochemical parameters were altered by these three environmental stressors. Values for all the test parameters except GSH first increased and then decreased at various experimental treatments during days 15 and 30 as a result of acidification, hypoxia and warming. GSH content always increased with decreased pH, decreased DO and increased temperature. PCA showed a positive correlation among all the measured biochemical indexes. IBR results showed that M. coruscus were adversely affected by reduced pH, low DO and elevated temperature.

Developmental toxicity induced by Cu(OH)2 nanopesticide in zebrafish embryos

The current study evaluates the adverse effects of Cu(OH)₂ nanopesticide (CNPE) on the early life stages of zebrafish (Danio rerio). The developmental toxicity was determined using different parameters such as mortality (including LC₅₀ ), hatching, heart rates, malformations, and alteration of the gene expressions. Zebrafish embryos (4 hpf-hours postfertilization) were exposed to 1.0, 2.0, 4.0, 8.0, and 16.0 mg/l CNPE doses until 96 hpf. The 96 hours LC₅₀ was recorded at 6.258 mg/l. Seventy-two hpf total malformation index values for 2.0, 4.0, and 8.0 mg/l CNPE doses were 4.3, 7.2 and 7.9, respectively. 1.0 mg/l CNPE is not toxic for the zebrafish embryos/larvae. 2.0 to 8.0 CNPE doses caused some abnormalities in embryos/larvae morphology, including lack of body parts, tail deformities, chorda deformity, bubbled head, scoliosis, lordosis, weak or non-pigmentation, decreased heart rate and larva length. 16.0 mg/l CNPE caused mortality in 72 hpf. The expression levels of seven immune system-related genes (il-1β, il-8, cebp, tlr4, hsp70, NF-kB, and mtf-1) were examined. The transcription level of il-1β, il-8, tlr4, hsp70, and NF-kB genes significantly increased in the CNPE exposure groups. While the expression of the mtf-1 gene considerably decreased, the cebp gene expression level did not change in the 4.0 and 8.0 mg/l CNPE doses. In conclusion, CNPE could induce developmental toxicity with malformations in embryos/larvae and alter the gene expression.