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

Comparative biotoxicity study for identifying better alternative insecticide especially green nano-emulsion which used as mosquitocides

This research work was planned to test biosafety of different nanomaterials on the different animals models. These nanoparticles were previously used as potential insecticides of mosquito larvae. The biosafety of these nanoproducts were evaluated on certain organs of non target animals that associated with mosquito breeding sites in Egypt. Animal organs such as the kidneys of rats, toads, and the fish's spleen were used as models to study the biological toxicity of these nanomaterials. After 30 days of the animals receiving the nanomaterials in their water supply, different cell mediated immune cells were assessed in these tissues. Both TNF-α and BAX immuno-expression were also used as immunohistochemical markers. Histopathology was conducted to detect the effect of the tested nanoproducts at the tissue level of the liver and kidneys of both the rats and toads. Green nanoemulsion of the lavender essential oil was relatively more effective, safe, and biodegradable to be used as insecticides against mosquito larvae than the metal-based nanomaterials.

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.

Is the trend toward a sustainable green synthesis of copper oxide nanoparticles completely safe for Oreochromis niloticus when compared to chemical ones?: using oxidative stress, bioaccumulation, and histological biomarkers

Scientists worldwide have noticed that cutting-edge technologies can be used to produce nanoparticles (NPs) in a sustainable and environmentally friendly way, instead of the old methods. However, the effectiveness of this approach for aquatic environments and species still needs to be determined. Therefore, this study aims to compare between the toxicity of green and chemically synthesized copper oxide nanoparticles (GS and CS) CuO NPs at two different concentrations on Nile tilapia (Oreochromis niloticus) using various biomarkers. CuO NPs' formation was proved, and their different characterizations were recorded. Then, the fish samples were randomly allocated in glass aquaria into five groups: one acted as a control group, and the other groups were exposed to two concentrations (25 and 50 mg/L) of GS-CuO NPs and CS-CuO NPs, separately, for 4 days. After the experimental time, in all groups that were exposed to two concentrations of both synthesized CuO NPs, the results revealed that glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), and thiobarbituric acid reactive substances (TBARS) levels were elevated in the liver and gills compared to glutathione reduced (GSH) content, which showed a significant decline. Bioaccumulation of Cu was more prevalent in the liver than in the gills, and the highest bioaccumulation capacity was more evident in the groups exposed to CS-CuO NPs. Moreover, the bioaccumulation of Cu caused severe histological changes in the liver and gills. In conclusion, the results suggested that GS-CuO NPs revealed less toxicity than CS-CuO NPs to the examined fish. However, they are still toxic, and their toxic effect cannot be overlooked.

Effect of long-term exposure of mixture of ZnO and CuO nanoparticles on Scenedesmus obliquus

The present study investigated the possible toxic effect of ZnO and CuO nanoparticles (NPs) on freshwater microalgae, Scenedesmus obliquus at environmentally- relevant nanoparticle concentration (1 mg/L) and high concentration (10 mg/L) in BG-11 medium under white light LED-illumination over 35 days. The effect of time on the stability of media, nanoparticles, and their relation to toxicity to algae was also studied. The transmission electron microscopy indicated structural damage to algae due to the presence of a mixture of nanoparticles (at 10 mg/L). FTIR (Fourier Transform infrared) analysis of a sample containing a mixture of nanoparticles showed an addition of bonds and a difference in the peak location and its intensity values. The inhibition time for biomass was observed between 14 days and 21 days at 10 mg/L NPs. At 1 mg/L, the order of toxicity of NPs to algae was found to be: CuO NPs (highest toxicity) > ZnO NPs>ZnO + CuO NPs (least toxicity). During exposure of algae cells to a mixture of NPs at 10 mg/L NP concentration, a smaller value of metal deposition was observed than that during exposure to individual NPs. Antagonistic toxic effects of two NPs on dry cell weight of algae was observed at both concentration levels. Future work is needed to understand the steps involved in toxicity due to mixture of NPs to algae so that environmental exposures of algae to NPs can be managed and minimized.

Ameliorative effects of Dunaliella salina microalgae on nanoparticle (ZnO NPs)-induced toxicity in fish

Dunaliella salina (D. salina) is a well-known microalga that contains considerable amounts of nutritious and medicinal bioactive components. This work studied the modulatory role of D. salina against zinc oxide nanoparticle (ZnO NPs)-induced neurotoxic effects in adult zebrafish. Fishes were subjected to 0.69 mg L-1 (1/5th 96-h LC50) for 4 weeks; then, fishes were supplemented with D. salina in the diet for 2 weeks at two levels (15 and 30%). Exposure to ZnO NPs induced a significant increase in the levels of reactive oxygen species (ROS), hydrogen peroxide (H2O2), malondialdehyde (MDA), and 8-hydroxy-2-deoxyguanosine (8-OH-dG) while accompanied with downregulation of antioxidant genes in the brain of exposed fishes. Brain neurochemistry and enzyme activities were also altered following ZnO NP exposure. ZnO NPs significantly reduced the neurotransmitters and acetylcholinesterase (AchE) activity while increasing Alzheimer's disease-related proteins and inflammatory response via upregulation of tumor necrosis factor (TNF-α). Additionally, ZnO NPs increased the indices of brain's DNA oxidative damage, increasing brain tissue's metallothionein (MT) and zinc residues. ZnO NPs upregulated the transcription patterns of apoptosis-related genes (casp3 and p53). D. salina dietary co-supplementation with ZnO NPs alleviated the ZnO NPsZnO NP-induced neuro-oxidative damages by lowering the lipid, DNA damage, and inflammatory biomarkers. Besides, D. salina alleviating responses were linked with increasing the levels of the assessed antioxidants. Conclusively, D. salina dietary supplementation induced potential alleviating effects of the ZnO NP-induced neurotoxicity in adult zebrafish.

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.

Investigation on the Toxicity of Nanoparticle Mixture in Rainbow Trout Juveniles

The environmental impacts of nanoparticle mixtures in the aquatic environment is not well understood. The purpose of this study examined the sub-lethal toxicity of low concentrations (ug/L range) of selected nanoparticles alone and in mixtures in juvenile trout. Fish were exposed to to individual and two environmentally relevant mixtures of silver (nAg), copper oxide (nCuO) and cerium oxide (nCeO) nanoparticles for 96 h at 15 °C. After the exposure period, fish were depurated overnight and tissue levels in Ag, Ce, Cu and Zn were determined along with a suite of effects biomarkers such as oxidative stress/inflammation, denatured protein tagging (ubiquitin), DNA strand breaks (genotoxicity) and acetylcholinesterase (AChE) activity. The data showed that these nanoparticles behaved as suspended matter but were nevertheless bioavailable for fish with bioconcentration factors of 6, 8 and 2 for nAg, nCeO and nCuO respectively. Only nCuO alone increased malonaldehyde (lipid peroxidation) contents but all nanoparticles increased DNA damage, protein-ubiquitin labeling, and decreased AChE activity. Globally, the toxicity of nCeO and nCuO was generally stronger than nAg, and antagonist effects were found in the mixtures. The interactions involved in these antagonisms are not well understood but do not involve the liberation of free ions and labile zinc in tissues. In conclusion, the bioavailability and toxicity of these nanoparticles are influenced by mixtures of nanoparticles, which is likely to occur in contaminated environments.