The potential ameliorative role of Dimercaptosuccinic acid against the toxicity of Titanium Dioxide Nanoparticles on Caelatura nilotica clams

The prevalent use of nanoparticles has adverse negative effects on biosystems. Subsequently, this study aimed to use Caelatura nilotica to assess the ecotoxicity of TiO2 NPs and how Dimercaptosuccinic acid (DMSA) improves these effects. Two concentrations of TiO2 NPs (25 and 150 µg/L) were used for 28 days. TiO2 NPs bioaccumulation, gonadal weight, gonado-somatic index, and histopathological alterations of gonads were determined. The tissues' accumulation of TiO2 NPs was concentration-time-dependent: it was 78.5 ± 28.93 μg/g dry weight in the exposed clams to 150 µg/L TiO2 NPs after 4 weeks of exposure. The gonadal weight and gonado-somatic index significantly decreased of the exposed group to 150 µg/L TiO2 NPs over the experimental period that they ended with values (1.01 ± 0.57 gm, 19.15 ± 7.75%, respectively). There are some histological alterations in the gonads of C. nilotica such as necrosis, deteriorated connective tissue, increased fibrous tissue, a reduced presence of mature sperms and mature ova, and irregular shapes of testicular/ovarian follicles. When using Dimercaptosuccinic acid (DMSA), this led to a reduction in accumulation of TiO2 NPs by the end of the experiment. So, C. nilotica is a promising model to reflect the adverse nano-toxics. DMSA emerges as a potentially valuable chelating agent that abolishes the negative effects of these nanoparticles.

Biochemical and behavioral effects of zinc oxide nanorods on the freshwater mussel Potomida littoralis

Our study aimed to investigate the impact of nano-zinc oxide (nZnO), a widely used pollutant in industry, pharmaceuticals, and personal care products, on the behavior and oxidative stress of freshwater mussels (Potomida littoralis) an indicator species and also a model non-target organism in ecotoxicology. To this end mussels were exposed to nZnO (50 and 100 µg/L) and Zn2+ from ZnSO4 (50 and 100 µg/L) for 7 days. ZnSO4 was used for comparison purposes and to determine if the toxicity of nZnO was due to the release of ions into the aquatic environment. We evaluated changes in oxidative stress markers, including catalase (CAT), glutathione-S-transferase (GST), acetylcholinesterase (AChE), and malondialdehyde (MDA) levels, on the mussel gills and digestive glands. Additionally, the effect of nZnO on the filtration rate of bivalves was studied. The findings showed that the mussel tissue's different parameters were significantly affected by exposure to various concentrations of nZnO, causing changes in their behavior that led to a decrease in filtration rate. Additionally, noteworthy increments were observed in CAT activity, AChE activity, and MDA levels, whereas GST activity displayed a decreasing trend, implying that oxidative stress contributes to the toxicity of nZnO. The purpose of this review is to present a framework for comprehending the toxicological impacts of nanoparticles from an environmental standpoint. Additionally, it includes novel information about the connections between nanoparticles (NPs) and bivalve species.

Ecotoxicological effects of zinc oxide nanoparticles (ZnO-NPs) on aquatic organisms: Current research and emerging trends

The rapid advancement of nanotechnology has contributed to the development of several products that are being released to the consumer market without careful analysis of their potential impact on the environment. Zinc oxide nanoparticles (ZnO-NPs) are used in several fields and are applied in consumer products, technological innovations, and biomedicine. In this sense, this study aims to compile existing knowledge regarding the effects of ZnO-NPs on non-target organisms, with the goal of ensuring the safety of human health and the environment. To achieve this objective, a systematic review of the available data on the toxicity of these nanomaterials to freshwater and marine/estuarine aquatic organisms was carried out. The findings indicate that freshwater invertebrates are the most commonly used organisms in ecotoxicological tests. The environmental sensitivity of the studied species was categorized as follows: invertebrates > bacteria > algae > vertebrates. Among the most sensitive species at each trophic level in freshwater and marine/estuarine environments are Daphnia magna and Paracentrotus lividus; Escherichia coli and Vibrio fischeri; Scenedesmus obliquus and Isochrysis galbana; and Danio rerio and Rutilus caspicus. The primary mechanisms responsible for the toxicity of ZnO-NPs involve the release of Zn2+ ions and the generation of reactive oxygen species (ROS). Thus, the biosynthesis of ZnO-NPs has been presented as a less toxic form of production, although it requires further investigation. Therefore, the synthesis of the information presented in this review can help to decide which organisms and which exposure concentrations are suitable for estimating the toxicity of nanomaterials in aquatic ecosystems. It is expected that this information will serve as a foundation for future research aimed at reducing the reliance on animals in ecotoxicological testing, aligning with the goal of promoting the sustainable advancement of nanotechnology.

Impact of Pb Toxicity on the Freshwater Pearl Mussel, Lamellidens marginalis: Growth Metrics, Hemocyto-Immunology, and Histological Alterations in Gill, Kidney, and Muscle Tissue

Pb is one of the most extensively used harmful heavy metals in Bangladesh, and its occurrence in waters affects aquatic organisms significantly. The tropical pearl mussel, Lamellidens marginalis, was exposed to different concentrations (T₁ 21.93 mgL^-1, T₂ 43.86 mgL^-1, and T₃ 87.72 mgL^-1) of Pb(NO₃)₂ and was evaluated against a control C 0 mgL^-1 of Pb(NO₃)₂, followed by a 96 h acute toxicity test. The LC₅₀ value was recorded as 219.32 mgL^-1. The physicochemical parameters were documented regularly for each treatment unit. The values of % SGR, shell weight, soft tissue wet weight, and weight gain remained statistically higher for the control group in comparison with the treatment. No mortality was noted for control units, while a gradually decreased survival rate was recorded for the different treatment groups. Fulton's condition factor was recorded as highest in the control and lowest in the T₃ unit, while the condition indices did not vary between the control and treatment groups. The hemocyte was accounted as maximum in the control and T₁, while minimum in T₂ and T₃. The serum lysosomal parameters also followed a similar pattern, and a significantly low level of lysosomal membrane stability, and serum lysosome activity was noted for T₃ and T₂ units in comparison to the control group. The histology of the gill, kidney, and muscle was well structured in the control group, while distinct pathologies were observed in the gill, kidney, and muscle tissue of different treatment groups. The quantitative comparison revealed that the intensity of pathological alteration increased as the dosage of Pb increased. The current study, therefore, indicated that intrusion of Pb(NO₃)₂ in the living medium significantly alters growth performance and hemocyte counts, and chronic toxicity induces histomorphological abnormalities in vital organs.

Changes in energy reserves and responses of some biomarkers in freshwater mussels exposed to metal-oxide nanoparticles

In this study, responses of various biomarkers in the digestive gland and foot muscle of freshwater mussels (Unio tigridis) were investigated following exposure to Al₂O₃, CuO and TiO₂ nanoparticles (NPs) for 14 days at different concentrations (0, 1, 3 and 9 mg NP/L). Mussels were fed on unicellular algae (Chlorella vulgaris) cultured in the laboratory. NP exposures caused significant increases (p < 0.05) in the levels of total glutathione (GSH), reduced-glutathione (rGSH), oxidized-glutathione (GSSG) and malondialdehyde (MDA) in the digestive gland. Oppositely, there were significant (p < 0.05) decreases in acetylcholinesterase activity in the foot muscles. Total energy reserves of the digestive gland and foot muscle significantly (p < 0.05) decreased, but only at the highest NP exposures. Nevertheless, NP exposures did not alter (p > 0.05) the algae filtering capacity of mussels. This study demonstrated that the biomarkers belonging to different metabolic systems responded to NP exposures, suggesting their usage in the monitoring studies for freshwater systems.

Molluscicidal and biochemical effects of green-synthesized F-doped ZnO nanoparticles against land snail Monacha cartusiana under laboratory and field conditions

The glass clover snail, Monacha cartusiana (M. cartusiana) is one of the most seriously impacting economic animal pests spreading across Egypt which inflicts severe damages to the agriculture. A green route is developed by deploying an abundant Rosemary plant leaves aqueous extract to synthesize ZnO and F-doped ZnO (F-ZnO) nanoparticles (NPs) that display high molluscicidal activities against the M. cartusiana land snails via leaf dipping and contact techniques. The effect of lethal concentrations, that kills 50% of exposed snails (LC50) value of the treatments, is examined on the activity of alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), enzymes, total protein (TP), total lipids (TL) and cholesterol level of snails, including the histopathological evaluation of the digestive gland and foot of M. Cartusiana. Their molluscicidal activity as poisonous baits under field conditions is also evaluated and compared to the recommended molluscicide, Neomyl. The results show that F^- doping dramatically improves the snail control capability of ZnO NPs, and promotes a considerable increase in both ALT and AST enzymes with an enhancement of TL and Cholesterol levels, but a significant decrease in TP content and ALP activity in treated snails compared to the control group. The LC₅₀ values are found to be 1381.55 and 2197.59 ppm using the leaf dipping for F-ZnO and ZnO, while 237.51 and 245.90 ppm can be achieved using the contact technique, respectively. The greenly synthesized F-ZnO and ZnO NPs induce severe histological alterations in the digestive gland and foot of M. cartusiana, including a complete destruction of the digestive tubules. The histological evaluation of the foot of M. cartusiana exposed to ZnO, shows a rupture of the epithelial layer of the foot sole, while F- ZnO NPs causes the folds of the foot becoming deeper and the rupture of epithelial layer. Our field experiments further demonstrate that F-ZnO achieves 60.08% reduction, while ZnO attains 56.39% diminution in snail population compared to the commercial, Neomyl (69.55%), exhibiting great potentials in controlling the harmful land snail populations.

Investigation on characterization, antifouling and cytotoxic properties of zinc oxide nanoparticles biosynthesized by a mangrove-associated actinobacterium Streptomyces olivaceus (MSU3)

The present study was undertaken to biosynthesize zinc oxide nanoparticles (ZnONPs) using a mangrove-associated actinobacterium Streptomyces olivaceus (MSU3) under in vitro conditions. The synthesized ZnONPs were structurally characterized through UV, FT-IR, TG-DTA, XRD, SEM and EDX analysis. Analysis of biosynthesized ZnONPs in UV-Vis spectroscopy showed presence of functional groups between the wavelengths 325 and 380 nm. FT-IR analysis showed the functional groups, such as halo bromide (C-Br), alkyne (C≡C), carboxylic acid (O-H), nitro (N-O), fluoro (C-F), alkene (C=C) and aromatic (R-C-H) groups, respectively, within the wave numbers between 614.30 and 3074.41 cm^-1. The crystalline poly-dispersed quasi spherical nature of ZnONPs expressed the average particle size of 37.9 nm with the 2θ values of 11.802-37.885°. Antibacterial activity of ZnONPs showed pronounced inhibitory zone (25 mm) and least MIC and MBC values (125 and 250 µg ml^-1) against Escherchia sp. In the antifouling study, ZnONPs strongly inhibited byssal thread formation in mussel Perna indica and recorded LC₅₀ value of 424.47 µg ml^-1. Mollusc foot adherence assay inferred that the ZnONPs effectively inhibited settlement of limpet Patella vulgata and showed minimal fouling (26.43%) at 350 µg ml^-1 and recorded LC₅₀ value of 218.77 µg ml^-1. Results of anticrustacean assay depicted that, ZnONPs had registered LC₅₀ value of 676.08 µg ml^-1 against Artemia salina nauplii. From this study, it could be concluded that an eco-friendly approach could be used to open a new avenue for biosynthesis of ZnONPs from a mangrove associated actinobacterium S. olivaceus (MSU3) in antifouling studies.

Mechanism of action and toxicological evaluation of engineered layered double hydroxide nanomaterials in Biomphalaria alexandrina snails

Layered double hydroxide (LDH) nanomaterials have recently become immense research area as it is used widely in industries. So, it's chance of their release into natural environment and risk assessment to nontarget aquatic invertebrate increasing. So, the present study aimed to synthesize and confirm the crystalline formation of Co-Cd-Fe LDHs and Co-Cd-Fe/PbI₂ (LDH) and then to investigate the toxic impact of the two LDH on the adult freshwater snails (Biomphalaia alexandrina). Results showed that Co-Cd-Fe/PbI₂ LDH has more toxic effect to adult Biomphalaria than Co-Cd-Fe LDHs (LC₅₀ was 56.4 and 147.7 mg/L, 72 h of exposure, respectively). The effect of LC₂₅ (117.1 mg/L) of Co-Cd-Fe LDHs exposure on the embryo showed suppression of embryonic development and induced embryo malformation. Also, it showed alterations in the tegmental architectures of the mantle-foot region of B. alexandrina snails as declared in scanning electron micrograph. Also, exposure to this sublethal concentration caused abnormalities in hemocyte shapes and upregulated IL-2 level in soft tissue. In addition, it decreased levels of nonenzymatic reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), caspase-3 activity, and total protein content in significant manner. Glutathione S-transferase (GST) activity was not affected by LDH exposure. It caused histopathological damages in both glands of snails and also caused a genotoxic effect in their cells. The results from the present study indicated that LDH has risk assessment on aquatic B. alexandrina snails and that it can be used as a biological indicator of water pollution with LDH.

Silver/chitosan nanocomposites induce physiological and histological changes in freshwater bivalve

BACKGROUND

Bivalves can accumulate and concentrate most pollutants, even if they are present in somewhat low concentrations. The present study aimed to use freshwater bivalveas for the first time as vital indicator for silver/chitosan nanocomposites (Ag-CS NCs) in the freshwater environment.

METHODS

Following the preparation and characterization of Ag-CS NCs by using UV-vis spectrophotometer, X-ray diffraction, transmission electron microscopy, and acute toxicity study, the animals exposed to three different dose of nano chitosan (CS), AgNPs, and Ag-CS NCs (12.5, 25 and 50 mg/L) for consecutive 6 days.

RESULTS

Ag-CS particles were in size range of 8-19 nm. The nominal concentrations for Ag-CS NCs were 12.5, 25 and 50 mg Ag L^-1 were corresponding to measured concentration of AgNPs 0.37, 0.81, and 1.65 mg Ag L^-1, respectively. All concentrations of Ag-CS NCs caused a significant increase in MDA and NO, while GSH and CAT levels decreased significantly in all organs. Histological investigation of the gills, labial palp and foot tissues showed alternation after exposure to Ag-CS NCs, especially at dose 50 mg/L.

CONCLUSION

The present study showed that exposure to Ag-CS NCs caused oxidative stress responses in Coelatura aegyptiaca and histological changes in the organs. These physiological and histological changes observed after exposure to Ag-CS NCs were most likely the result of the action of AgNPs themselves while the effect of chitosan on these changes was negligible. We concluded that Coelatura aegyptiaca was a sensitive bio-indicator for monitoring of the past and the present water pollution by nanoparticles.

Antioxidant system biomarkers of freshwater mussel (Unio tigridis) respond to nanoparticle (Al2O3, CuO, TiO2) exposures

PURPOSE

Mussels are known as the natural filters of the aquatic systems and are accepted as one of the best bioindicator organism. There is no data on the response of Unio tigridis to metal-oxide nanoparticle (NP) exposures. This study aimed to investigate the response of the antioxidant enzymes of U. tigridis following exposure to NPs.

MATERIALS AND METHODS

The mussels were exposed to different concentrations (0, 1, 3, 9 mg NP/L) of Al₂O₃, CuO and TiO₂ NPs for 14 days and subsequently, the activities of CAT (catalase), SOD (superoxide dismutase), GPx (glutathione peroxidase), GST (glutathione S-transferase) and GR (glutathione reductase) were measured in the gill and digestive gland. Mussels were fed with cultured unicellular algae (Chlorella vulgaris) during experiments.

RESULTS

Data showed that algae consumptions of mussels were not significantly (p>0.05) altered by NPs. However, all enzyme activities in the digestive gland and gill altered significantly (p<0.05) after NP exposures. The activities of CAT and SOD decreased, while the activities of enzymes belonging to glutathione metabolism (GPx and GST) increased in both tissues.

CONCLUSION

This study representing the first record on the antioxidant system response of U. tigridis toward NP exposures suggests that NP toxicity should be investigated thoroughly in organisms and some regulations must be done on their usages.

Facile synthesis of Cu-doped ZnO nanoparticle in triethyleneglycol: photocatalytic activities and aquatic ecotoxicity

A new synthetisis method of Cu-doped ZnO nanoparticles is presented in this work, this novel approach allow one to produce Zinc oxide nanocristal owing to a modified Polyol process that makes use of triethyleneglycol (TREG) as a solvent. The structure and morphology of the nanoparticles were characterized by high-resolution transmission electron microscopy (HRTEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N₂ adsorption study, UV-Vis diffuse reflectance spectroscopy, inductively coupled plasma optical emission spectroscopy and Raman spectroscopy. The lightly doped Zn_1-xCu_xO photocatalysts consisted in a novel nanorods structure of Zn_0.9990Cu_0.0010O nanoparticles. Taking the photocatalytic degradation of diuron under solar light as liquid phase test reaction, the lightly doped Zn_0.9990Cu_0.0010O nanorods photocatalysts showed strongly enhanced photocatalytic activity when compared to the bare ZnO counterpart. The apparent rate constant value of Zn_0.9990Cu_0.0010O was 22 times higher than that of pure ZnO. In order to study the environmental risk of Cu-ZnO, clams Ruditapes decussatus were exposed to Cu-ZnOC1 = 0.5 mg/L, Cu-ZnOC2 = 1 mg/L and Cu-ZnO C3 = 5 mg/L. Catalase (CAT) activities, malondialdehyde (MDA) content and acetylcholinesterase (AChE) activity were determined in gills and digestive gland of treated and untreated clams. Thus, no significant effects were detected in the gills of exposed clams after 7 days compared to control. Thus, MDA level and CAT activity showed significant differences in digestive glands of groups treated by the highest concentration of Cu-ZnO NPs compared to the control. No adverse effects on AChE activity was detected after Cu-ZnO NPs exposure. These results demonstrated that, although Cu-ZnO NPs is not acutely toxic to Ruditapes decussatus, it does exert oxidative stress on clams. These results are encouraging for the Cu-ZnO NPs use in variety of applications due to its high photocatalytic and low environmental toxicity.

Hormonal and molecular alterations induced by sub-lethal toxicity of zinc oxide nanoparticles on Oreochromis niloticus

This study was carried out to determine the biochemical and molecular potential effects of Zn-ONPs sub-lethal toxicity on the hormonal profile of Oreochromis niloticus (O. niloticus). One hundred and fifty O. niloticus juvenile female were used in this experiment; Ninety for determination of LC50 and other 60 fish were divided into 3 groups with 20 fish each (two replicate in each group). Group I used as control group whereas other groups treated with 1/20 and 1/30 of LC50 respectively for 4 days. Serum, pituitary gland, hepatic, pancreatic and muscular tissues were obtained for hormonal and molecular evaluation. Serum growth hormone (GH), thyroid stimulating hormone (TSH), triiodothyronine (T3), tetraiodothyronine (T4), follicular stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), testosterone and insulin hormones were significantly decreased with a significant increase in both Adrenocorticosteroid hormone (ACTH) and cortisol levels with no change in serum glucagon levels. On molecular levels there were a significant down regulation in transcriptional levels of GH, Insulin like growth factor I (IGF-I), insulin and Insulin receptor-A (IRA genes. These results suggested that, hormonal and molecular alterations can be used as an early biomarkers for Zn-ONPs toxicity in fish.

Optimizing and Evaluating the Antihelminthic Activity of the Biocompatible Zinc Oxide Nanoparticles Against the Ascaridid Nematode, Parascaris equorum In Vitro

PURPOSE

In the present study, the effect of different biocompatible concentrations from ZnO nanoparticles (ZnO NPs) on the physiological state and surface topography of the nematode P. equorum was determined in vitro.

METHODS

Different concentrations of ZnO NPs (100, 200, 300 and 400 mg/l) synthesized using the egg white were prepared followed by the incubation of parasitic worms with these concentrations in vitro. The physiological state of treated worms such as oxidative stress markers, enzymatic activities and biochemical parameters in addition to the surface topography was determined and compared with control untreated worms.

RESULTS

In comparison to control worms, it was observed that at high concentrations of ZnO NPs, most of the treated worms showed an increase in the levels of ALT, AST and ALP (worm muscle damage, and gonad injury); enhancement of the total protein content (worm cellular dysfunction); significant increase in MDA level (free radical-mediated worm cell membrane damage); depletion in GST and GSH activities (reduced ability to clear toxic compounds like lipid peroxides); CAT depletion (superoxide dismutase and hydrogen peroxide toxicity) and NO increase (detoxification activity and stressful conditions on worms). SEM showed that there was a modified morphological appearance in the surface of treated worms; lips were wrinkled with irregularly arranged denticles, weathering of cuticle, bursts of cuticle layers, disruption of surface annulations and erosion of surface papillae of male around the cloacal opening.

CONCLUSION

ZnO NPs at environmentally relevant concentrations achieved a significant antihelminthic activity against P. equorum which represents a successful model used in parasite control experiments.

The influence of surface waters on the bioavailability and toxicity of zinc oxide nanoparticles in freshwater mussels

The release of engineered nanoparticles in the aquatic environment could pose a threat to the biota. The purpose of the study was to examine the influence of surface water characteristics on zinc oxide nanoparticles (nZnO) and ZnS0₄ toxicity to the freshwater mussel Dreissena polymorpha. Mussels were exposed to an equivalent concentration of 25 μg/L Zn as either nZnO or ZnSO₄ for 96 h at 15 °C in 4 types of surface waters: green water (high conductivity and pH with low natural organic matter content), brown water (low conductivity and pH with high natural organic matter content), diluted municipal effluent (high conductivity and pH with high urban organic matter content) and aquarium water (treated green water with organic matter removed). After the exposure period, mussels were analyzed for air-time survival, total and labile Zn levels in tissues, lipid metabolism (phospholipase A2, triglycerides levels) and oxidative stress (glutathione S-transferase, arachidonate cyclooxygenase, lipid peroxidation). The data revealed that mussels exposed to ZnSO₄ in controlled aquarium water accumulated more total and labile Zn tissues, decreased oxidative stress and triglycerides and increased air time survival. While nZnO had few effects in aquarium water, oxidative stress was enhanced and total Zn in tissues were decreased in brown water and diluted municipal effluent and triglycerides were higher in nZn-exposed mussels in brown water. Air-time survival was decreased in mussels kept in green water and nZnO. It was also decreased in mussels exposed to ZnSO₄ in green water and diluted municipal effluent. In conclusion, the fate and toxic effects of Zn could be influenced by both the chemical form (nanoparticles or ionic Zn) and surface water properties in freshwater mussels.

Toxicological impact of oxyfluorfen 24% herbicide on the reproductive system, antioxidant enzymes, and endocrine disruption of Biomphalaria alexandrina (Ehrenberg, 1831) snails

Oxyfluorfen (Goal 24%EC) herbicide is widely used in agriculture for weed control. Biomphalaria alexandrina snails can be used as bioindicator of the chemical pollution in the aquatic environment. The objective of this study was to evaluate the molluscicidal activity of this herbicide on Biomphalaria alexandrina snails and how it affected its biological system. The present study revealed a molluscicidal effect of oxyfluorfen 24%EC on these snails at LC₅₀ 5.9 mg/l. After exposure of snails to the sub-lethal concentrations (LC₀, LC₁₀, or LC₂₅) of this herbicide, the survival rates, reproductive rate (R₀), and fecundity (M_x) of adult B. alexandrina snails were significantly decreased in comparison with the control group. Also, levels of testosterone and estradiol were decreased significantly. It caused alterations in the antioxidant system, where exposure to sub-lethal concentration of this herbicide caused significant increases in levels of lipid peroxide malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD), while it significantly decreased glutathione transferase (GST). Histopathological changes in the digestive gland included severe damage in the digestive cells, where, they lost their tips and some were degenerated, while the secretory cells increased in number. Regarding the hermaphrodite gland, there were losses of the connective tissues, irregular sperms, and the eggs degenerated. These findings concluded that B. alexandrina snails can be used as a bioindicator for pollution with pesticide in the aquatic environment.

Metal accumulation, biochemical and behavioral responses on the Mediterranean clams Ruditapes decussatus exposed to two photocatalyst nanocomposites (TiO2 NPs and AuTiO2NPs)

Nanoparticle decoration with noble metal represents a promising alternative to improve their photocatalytic and photovoltaic properties. However, toxicity can be influenced by such modification, as the bioavailability of these substances may be influenced. To understand how decoration influences the NP impacts in marine ecosystems, we exposed suspension-feeding clams, Ruditapes decussatus, to two photocatalyst nanocomposites, TiO₂ NPs and AuTiO₂ NPs, over 2 concentrations, 50 μg L^-1and 100 μg L^-1, in a laboratory experiment. Accumulation of Au and Ti in gills and digestive gland was noted in clams after exposure to TiO₂ NPs and AuTiO₂ NPs using inductively coupled plasma optic emission spectroscopy (ICP-OES). TiO₂ and AuTiO₂ NPs alter the behavior of the clams Ruditapes decussatus by reducing filtration and respiration rates. Furthermore, the highest concentration of TiO₂NPs induces an overproduction of H₂O₂ in gills and digestive gland and NO production only in gills. Superoxide dismutase (SOD), Catalase (CAT), Glutathione-S-transferase (GST) and acetylcholinesterase (AChE) activities were induced in gills and digestives gland in concentration and nanocomposite type dependent manner. Decorated form presented higher Malondialdehyde (MDA) levels in gills and digestive gland than the undecorated form, suggesting different mechanisms of action that may be mediated through oxidative stress. In conclusion, the considered parameters could represent reliable biomarkers for the assessment of NP toxicity on R. decussatus as biological biomonitoring model. In addition, based on the obtained results, nanoparticle decoration influences the toxicity of metal nanoparticles in marine organism.

Oxidative Stress in the Muscles of the Fish Nile Tilapia Caused by Zinc Oxide Nanoparticles and Its Modulation by Vitamins C and E

The effects of zinc oxide nanoparticles (ZnONPs) on antioxidants in Nile tilapia muscles and the protective role of vitamins C and E were examined. Two hundred males of Nile tilapia were held in aquaria (10 fishes/aquarium). Fishes were divided into 5 groups: 40 fishes in each group; the first group was the control; the 2nd and 3rd groups were exposed to 1 and 2 mg/L of ZnONPs, respectively; and the 4th and 5th group were exposed to 1 and 2 mg/L of ZnONPs and treated with a (500 mg/kg diet) mixture of vitamin C and E mixture (250 mg/kg diet of each). Muscles were collected on the 7th and 15th day of treatments. Muscle malondialdehyde, reduced glutathione levels, superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GR), glutathione peroxidase (GPx), and glutathione-S-transferase (GST) activities were measured after treatments. Relative quantification of SOD, CAT, GR, GPx, and GST mRNA transcripts was detected in the muscles. Results showed that MDA and GSH concentration; SOD, CAT, GR, GPx, and GST activities; and mRNA expression were significantly decreased in groups exposed to ZnONPs. Vitamins C and E significantly ameliorated the toxic effects of ZnONPs. In conclusion, vitamins C and E have the ability to ameliorate ZnONP oxidative stress toxicity in Nile tilapia.