Toxicity Of ZnO Nanoparticles Research Articles

Toxicity of zinc oxide nanoparticles: Cellular and behavioural effects

Due to their extensive use, the release of zinc oxide nanoparticles (ZnO NP) into the environment is increasing and may lead to unintended risk to both human health and ecosystems. Access of ZnO NP to the brain has been demonstrated, so their potential toxicity on the nervous system is a matter of particular concern. Although evaluation of ZnO NP toxicity has been reported in several previous studies, the specific effects on the nervous system are not completely understood and, particularly, effects on genetic material and on organism behaviour are poorly addressed. We evaluated the potential toxic effects of ZnO NP in vitro and in vivo, and the role of zinc ions (Zn2+) in these effects. In vitro, the ability of ZnO NP to be internalized by A172 glial cells was verified, and the cytotoxic and genotoxic effects of ZnO NP or the released Zn2+ ions were addressed by means of vital dye exclusion and comet assay, respectively. In vivo, behavioural alterations were evaluated in zebrafish embryos using a total locomotion assay. ZnO NP induced decreases in viability of A172 cells after 24 h of exposure and genetic damage after 3 and 24 h. The involvement of the Zn2+ ions released from the NP in genotoxicity was confirmed. ZnO NP exposure also resulted in decreased locomotor activity of zebrafish embryos, with a clear role of released Zn2+ ions in this effect. These findings support the toxic potential of ZnO NP showing, for the first time, genetic effects on glial cells and proving the intervention of Zn2+ ions.

Ecotoxicological Research on the Toxic Impact of Zinc Oxide and Silver Nanoparticles on Oreochromis mossambicus.

Silver nanoparticles (AgNPs) and Zinc oxide nanoparticles (ZnONPs) have been widely used and are eventually been discharged into the natural aquatic ecosystem. The current study examined and correlated the toxicity of AgNPs and ZnONPs on the Mozambique tilapia, Oreochromis mossambicus. Lethal concentration (LC50) was determined with four different concentrations (0.05, 0.10, 0.15, and 0.20 mg/L) of AgNPs and ZnONPs; subsequently, the fishes were exposed to sublethal concentrations for a period of 21 days, and the oxidative stress and antioxidant and nonantioxidant parameters were studied. Results revealed oxidative stress evinced by increased lipid peroxidation (LPO) protein carbonyl activity (PCA), glutathione-S-transferase (GST), glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT) activity, metallothionein (MT) activity, and reduced glutathione in chronic exposure compared with acute exposure. Nonspecific immunological characteristics such as lysozyme (LYZ), myeloperoxidase (MPO), and respiratory burst activity (RBA) were also noticed in the serum. Furthermore, severe histological damages including damages in telangiectasia and epithelial cell hyperplasia were found in the combined treated group with Ag and ZnONPs than in individual treatments. When Ag and ZnONPs were combined, a reduction in the accumulation of Ag was observed in the liver, which increased drastically in individual exposure. The current findings highlight the importance of taking into account the combined exposure and correlation of NPs, their bioavailability, and toxicity in the aquatic ecosystem.

Mechanistic insights into zinc oxide nanoparticles induced embryotoxicity via H3K9me3 modulation

The widespread application of nanoparticles (NPs) in various fields has raised health concerns, especially in reproductive health. Our research has shown zinc oxide nanoparticles (ZnONPs) exhibit the most significant toxicity to pre-implantation embryos in mice compared to other common NPs. In patients undergoing assisted reproduction technology (ART), a significant negative correlation was observed between Zn concentration and clinical outcomes. Therefore, this study explores the impact of ZnONPs exposure on pre-implantation embryonic development and its underlying mechanisms. We revealed that both in vivo and in vitro exposure to ZnONPs impairs pre-implantation embryonic development. Moreover, ZnONPs were found to reduce the pluripotency of mouse embryonic stem cells (mESCs), as evidenced by teratoma and diploid chimera assays. Employing multi-omics approaches, including RNA-Seq, CUT&Tag, and ATAC-seq, the embryotoxicity mechanisms of ZnONPs were elucidated. The findings indicate that ZnONPs elevate H3K9me3 levels, leading to increased heterochromatin and consequent inhibition of gene expression related to development and pluripotency. Notably, Chaetocin, a H3K9me3 inhibitor, sucessfully reversed the embryotoxicity effects induced by ZnONPs. Additionally, the direct interaction between ZnONPs and H3K9me3 was verified through pull-down and immunoprecipitation assays. Collectively, these findings offer new insights into the epigenetic mechanisms of ZnONPs toxicity, enhancing our understanding of their impact on human reproductive health.

Comparative evaluation of zinc oxide nanoparticles (ZnONPs): Photocatalysis, antibacterial, toxicity and genotoxicity

This study compares the physicochemical, photocatalytic, antimicrobial, toxicity and genotoxic properties of zinc oxide nanoparticles (ZnONPs) produced by hydrothermal and sol–gel methods as an alternative biomaterial. The comparative antibacterial activities, toxicity and DNA damage effects of ZnONPs on Drosophila melanogaster were determined using different doses. The study also investigates the effects of ZnONPs on malondialdehyde (MDA) and glutathione (GSH) levels, as well as superoxide dismutase (SOD) and catalase (CAT) activity. The structural, optical, and morphological properties of ZnONPs were investigated using X-ray diffractometer (XRD), UV–Visible spectrophotometry (UV–Vis), and field emission scanning electron microscopy (FESEM). The photocatalytic activity of ZnONPs in methylene blue solution was determined, and a high photocatalytic efficiency of 87 % was achieved in a short time. ZnONPs were found to have a significant antimicrobial effect on Streptococcus mutans ATCC 10449. Additionally, ZnONPs were non-toxic doses and did not cause DNA damage. In conclusion, ZnONPs synthesized can be safely used as filling material and bracket material especially in the field of dentistry since they are non-toxic, have a strong antimicrobial effect on S. mutans and do not cause DNA damage.

Zinc oxide nanoparticles mediate bacterial toxicity in Mueller-Hinton Broth via Zn2.

As antibiotic resistance increases and antibiotic development dwindles, new antimicrobial agents are needed. Recent advances in nanoscale engineering have increased interest in metal oxide nanoparticles, particularly zinc oxide nanoparticles, as antimicrobial agents. Zinc oxide nanoparticles are promising due to their broad-spectrum antibacterial activity and low production cost. Despite many studies demonstrating the effectiveness of zinc oxide nanoparticles, the antibacterial mechanism is still unknown. Previous work has implicated the role of reactive oxygen species such as hydrogen peroxide, physical damage of the cell envelope, and/or release of toxic Zn2+ ions as possible mechanisms of action. To evaluate the role of these proposed methods, we assessed the susceptibility of S. aureus mutant strains, ΔkatA and ΔmprF, to zinc oxide nanoparticles of approximately 50 nm in size. These assays demonstrated that hydrogen peroxide and electrostatic interactions are not crucial for mediating zinc oxide nanoparticle toxicity. Instead, we found that Zn2+ accumulates in Mueller-Hinton Broth over time and that removal of Zn2+ through chelation reverses this toxicity. Furthermore, we found that the physical separation of zinc oxide nanoparticles and bacterial cells using a semi-permeable membrane still allows for growth inhibition. We concluded that soluble Zn2+ is the primary mechanism by which zinc oxide nanoparticles mediate toxicity in Mueller-Hinton Broth. Future work investigating how factors such as particle morphology (e.g., size, polarity, surface defects) and media contribute to Zn2+ dissolution could allow for the synthesis of zinc oxide nanoparticles that possess chemical and morphological properties best suited for antibacterial efficacy.

Toxicity and Hepatoprotective Effects of ZnO Nanoparticles on Normal and High-Fat Diet-Fed Rat Livers: Mechanism of Action.

This experiment aimed to evaluate the beneficial and toxic properties of synthetic zinc oxide nanoparticles (ZnO NPs) on the liver of normal and high-fat diet (HFD) fed-rats. The ZnO NPs were synthesized and, its characterizations were determined by different techniques. Effect of ZnO NP on cell viability, liver enzymes and lipid accumulation were measured in HepG2 cells after 24h. After that, rats orally received various dosages of ZnO NPs for period of 4weeks. Toxicity tests were done to determine the appropriate dose. In the subsequent step, the hepatoprotective effects of 5mg/kg ZnO NPs were determined in HFD-fed rats (experiment 2). The oxidative stress, NLRP3 inflammasome, inflammatory, and apoptosis pathways were measured. Additionally, the activity of caspase 3, nitric oxide levels, antioxidant capacity, and various biochemical factors were measured. Morphological changes in the rat livers were also evaluated by hematoxylin and eosin (H & E) and Masson trichrome. Liver apoptosis rate was also approved by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. Treatment of animals with 5mg/ZnO NPs revealed potential hepatoprotective properties, while ZnO NPs at the doses of above 10mg/kg showed toxic effects. Antioxidant enzyme gene expression and activity were significantly augmented, while apoptosis, NLRP3 inflammasome, and inflammation pathways were significantly reduced by 5mg/kg ZnO NPs. Liver histopathological alterations were restored by 5mg/kg ZnO NPs in HFD. Our study highlights the hepatoprotective effects of ZnO NPs against the HFD-induced liver damage, involving antioxidant, anti-inflammatory, and anti-apoptotic pathways, indicating their promising therapeutic potential.

Response and Resilience of Scenedesmus rubescens Microalgae to ZnO Nanoparticles

Microalgae are microorganisms of great importance for aquatic ecosystems. The investigation of their interaction with potential environmental stressors like nanoparticles (NPs) is essential in order to assess their behavior and fate in aquatic ecosystems. The scope of this work is to investigate the response and potential toxic effects of the short-term exposure of Scenedesmus rubescens microalga to zinc oxide (ZnO) NPs with various initial nitrate concentrations in the culture medium. Scenedesmus rubescens was cultivated in four different compositions of modified BG-11 with a nitrate content varying from 0 to 300 mg/L, and it was exposed to four concentrations of ZnO NPs, ranging from 0.081 to 81 mg/L. S. rubescens was found to be resilient towards ZnO NP toxicity. The results also highlight the fact that the toxic effects of ZnO NPs on microalgae are highly dependent on the species tested. The nitrate content of the medium did not affect the toxicity of ZnO NPs but had a significant impact on cell concentration, as it was observed at an initial nitrate concentration of 300 mg/L. Further investigation should focus on studying the morphological and metabolic characteristics and mechanisms contributing to this species’ resilience.

Antibacterial Efficacy of ZnO/Bentonite (Clay) Nanocomposites against Multidrug-Resistant Escherichia coli.

The emergence of multidrug-resistant (MDR) bacteria has spurred the exploration of therapeutic nanomaterials such as ZnO nanoparticles. However, the inherent nonspecific toxicity of ZnO has posed a significant obstacle to their clinical utilization. In this research, we propose a novel approach to improve the selectivity of the toxicity of ZnO nanoparticles by impregnating them onto a less toxic clay mineral, Bentonite, resulting in ZB nanocomposites (ZB NCs). We hypothesize that these ZB NCs not only reduce toxicity toward both normal and carcinogenic cell lines but also retain the antibacterial properties of pure ZnO nanoparticles. To test this hypothesis, we synthesized ZB NCs by using a precipitation technique and confirmed their structural characteristics through X-ray diffraction and Raman spectroscopy. Electron microscopy revealed composite particles in the size range of 20-50 nm. The BET surface area of ZB NCs, within a relative pressure (P/P0) range of 0.407-0.985, was estimated to be 31.182 m2/g. Notably, 50 mg/mL ZB NCs demonstrated biocompatibility with HCT 116 and HEK 293 cell lines, supported by flow cytometry and fluorescence microscopy analysis. In vitro experiments further confirmed a remarkable five-log reduction in the population of MDR Escherichia coli in the presence of 50 mg/mL of ZB NCs. Antibacterial activity of the nanocomposites was also validated in the HEK293 and HCT 116 cell lines. These findings substantiate our hypothesis and underscore the effectiveness of ZB NCs against MDR E. coli while minimizing nonspecific toxicity toward healthy cells.

Subacute toxicity and endocrine-disrupting effects of Fe2O3, ZnO, and CeO2 nanoparticles on amphibian metamorphosis.

This study evaluated the potential toxic and endocrine-disrupting effects of sublethal concentrations of Fe2O3, CeO2 and ZnO nanoparticles (NPs) on amphibian metamorphosis. Tadpoles were exposed to several NPs concentrations, reaching a maximum of 1000µg/L, for up to 21days according to the amphibian metamorphosis assay (AMA). Some standard morphological parameters, such as developmental stage (DS), hind limb length (HLL), snout-to-vent length (SVL), wet body weight (WBW), and as well as post-exposure lethality were recorded in exposed organisms on days 7 and 21 of the bioassay. Furthermore, triiodothyronine (T3), thyroxine (T4) and malondialdehyde (MDA) levels and the activities of glutathione S-transferases (GST), glutathione reductase (GR), catalase (CAT), carboxylesterase (CaE), and acetylcholinesterase (AChE) were determined in exposed tadpoles as biomarkers. The results indicate that short-term exposure to Fe2O3 NPs leads to toxic effects, both exposure periods cause toxic effects and growth inhibition for ZnO NPs, while short-term exposure to CeO2 NPs results in toxic effects and long-term exposure causes endocrine-disrupting effects. The responses observed after exposure to the tested NPs during amphibian metamorphosis suggest that they may have ecotoxicological effects and their effects should be monitored through field studies.

Epigallocatechin gallate alleviated the in vivo toxicity of ZnO nanoparticles to mouse intestine.

To evaluate the oral toxicity of nanoparticles (NPs), it is necessary to consider the interactions between NPs and nutrient molecules. Recently, we reported that epigallocatechin gallate (EGCG), a healthy component in green tea, alleviated the toxicity of ZnO NPs to 3D Caco-2 spheroids in vitro. The present study investigated the combined effects of EGCG and ZnO NPs to mice in vivo. Mice were administrated with 35 or 105 mg/kg bodyweight ZnO NPs with or without the presence of 80 mg/kg bodyweight EGCG via gastric route, once a day, for 21 days, and the influences of EGCG on the toxicity of ZnO NPs to intestine were investigated. We found that EGCG altered the colloidal properties of ZnO NPs both in water and artificial intestine juice. As expected, ZnO NPs induced toxicological effects, such as decreased bodyweight, higher Chiu's scores, and ultrastructural changes in intestine, whereas EGCG alleviated these effects. Combined exposure to EGCG and ZnO NPs also changed trace element levels in mouse intestine. For example, the levels of Ti, Co, and Ni were only significantly elevated after co-exposure to EGCG and ZnO NPs, and Fe levels were only significantly decreased by ZnO NPs. Western blot analysis suggested that tight junction (TJ) and endoplasmic reticulum (ER) proteins were elevated by ZnO NPs, but EGCG inhibited this trend. Combined, these data suggested that gastric exposure to ZnO NPs induced intestinal damage, trace element imbalance, and TJ/ER protein expression in mouse intestine, whereas EGCG alleviated these effects of ZnO NPs.

Antibacterial Activity and Toxicity of Zinc Oxide Nanoparticles Combined with Supernatants of Lactobacillus spp. Against ESKAPE Bacteria: A Novel Mixture.

The emergence of multidrug resistance among nosocomial pathogens has prompted researchers to look for new antibacterial sources. Metal nanoparticles and probiotic products have attracted the attention of researchers. However, combination therapy is an attractive alternative in this field. This study evaluated the antibacterial activity and toxicity of Zinc Oxide nanoparticles (ZnO-NPs) combined with cell-free supernatant (CFS) of Lactobacillus plantarum and Lactobacillus acidophilus alone and in a novel mixture. Antibacterial effects and cytotoxic properties of ZnO-NPs, CFS of L. plantarum (SLP), and CFS of L. acidophilus (SLA) were determined alone and in a mixture against ESKAPE strains. In addition, the viability percentage of the cells was evaluated after exposure to these agents. Antibacterial mixtures (ZnO-NPs with SLP or ZnO-NPs with SLA) demonstrated synergistic and additive effects against Pseudomonas aeruginosa (FIC≤0.75), Acinetobacter baumannii (FIC = 1), and Escherichia coli (FIC≤0.75). The viability percentage of the cells after 24 h of exposure to a mixture of ZnO-NPs and SLA (about 50%) was more than when the cells were exposed to ZnO-NPs alone (about 30%) at the same concentration. A mixture of ZnO-NPs and CFS of probiotics can be an alternative to antibiotics, with more effectiveness and fewer side effects.

Evaluation of the toxicity of ZnO nanoparticles obtained by a chemical route on the nasal respiratory epithelium of the biomodel Mus musculus

Zinc oxide nanoparticles (ZnO-NPs) have antimicrobial and a number of other properties, rendering apt their use in biomedicine, environmental remediation, agriculture, and other fields. Given the potential use of these nanoparticles (NPs) in these areas, it is necessary to determine their toxic effects on biological systems. This work therefore analyzed the histological changes in the respiratory nasal epithelium of Mus musculus biomodels exposed to atmospheres containing ZnO-NPs at different concentrations (6, 15, and 40 mg/m3). The NPs were synthesized using the Pechini polymeric complex method and characterized using techniques such as IR and Raman spectroscopies, X-ray diffraction (XRD), transmission (TEM), and scanning electron microscopy (SEM). The ZnO-NPs obtained had a wurtzite-type structure, with spheroidal morphology and a particle size of ~ 50 nm, and the Raman spectrum showed the presence of defects in its structure. The results of the treatments to which the biomodels were subjected showed that the inhalation of ZnO-NPs caused significant morphological changes in their nasal epithelium (squamous metaplasia and vascular congestion) and an acute inflammatory response when exposed to high concentrations of NPs (40 and 15 mg/m3).Graphical

Influence of multi-walled carbon nanotubes on the toxicity of ZnO nanoparticles in the intestinal histopathology, apoptosis, and microbial community of common carp

In recent years, carbon nanotubes (CNTs) have gained tremendous attention due to their widespread application. Previous research indicated that carbon nanomaterials can affect the toxicity of some pollutants. In this study, we investigated the influence of multi-walled CNTs (MWCNTs) on the toxicity of ZnO nanoparticles (ZnONPs) in the intestine of common carp (Cyprinus carpio). After four-week exposure, histopathological observation and TUNEL assay showed concentration ratio-dependent intestinal lesions and apoptosis, with the most severe in the HSC-ZnONPs group (50 mg L−1 ZnONPs and 2.5 mg L−1 MWCNTs), less severe in the ZnONPs group (50 mg L−1 ZnONPs) and the least in the LSC-ZnONPs group (50 mg L−1 ZnONPs and 0.25 mg L−1 MWCNTs). Furthermore, ICP-OES indicated that intercellular zinc accumulation was significantly decreased by the presence of the MWCNTs, which suggested the varied contribution of ZnONPs to intestine injury in different groups. Moreover, 16 s rDNA sequencing revealed that ZnONPs alone and in combination with MWCNTs significantly altered the microbial community diversity and composition of the gut microbiota compared with controls. In addition, the predominant phylum, class, order, family, and genus were significantly different among these groups. In conclusion, the influence of MWCNTs on the toxicity of ZnONPs was related to the concentration and concentration ratio of the mixture.

Chronic effects induced by zinc oxide nanoparticles against larvae of the northern house mosquito Culex pipiens (Diptera: Culicidae)

It is estimated that up to a million person are subject to death every year from mosquito-borne diseases. To avoid the epidemic situations arising from mosquito-borne diseases, it is necessary to reduce the mosquito populations. Challenges against efficient mosquito management are mainly related to emergence of insecticide resistance leading to increased need for the development of alternative methods. Ideal insecticides cause permanent impacts on the target insects in order to ensure powerful insecticidal effect. This study hypothesized that the impact of zinc oxide nanoparticles (ZnONPs) on the larvae of Culex pipiens Linnaeus, 1758 (Diptera: Culicidae) mosquito is irreversible and chronic. The first instar C. pipiens larvae were treated with a sublethal concentration (LC20, 0.24 g/L) of ZnONPs for 72 h and then allowed to recover for additional 72 h. Following the recovery period, the changes in zinc accumulation, growth rate, gut ultrastructure, biochemical changes in the hydrogen peroxide, antioxidant and detoxification enzymes were recorded and compared between recovered larvae and untreated (control). Recovered larvae showed significant increase in the accumulated zinc and reduced growth rate by about 50% compared to untreated (control). Furthermore, the ultrastructure of the alimentary canal epithelium showed several forms of pathological signs in different parts of the midgut of recovered larvae. Treatment with ZnONPs induced oxidative stress (OS) which appeared in the form of significant increase in hydrogen peroxide concentration. In response to OS, insects activate the detoxification system to get rid of the toxic nanoparticles. The detoxification enzyme alkaline phosphatase (ALP) and the antioxidant enzyme glutathione peroxidase (GPX) were inhibited while superoxide dismutase (SOD) was activated against ZnONPs toxicity. Additionally, recovered larvae didn’t show differences in the catalase activity from untreated control. These results verified that ZnONPs induce chronic impacts on C. pipiens larvae suggesting that it can be used in their management via direct application in standing water sources including accumulated rains and swimming pools.

Plant mediated-green synthesis of zinc oxide nanoparticles: An insight into biomedical applications

Abstract Green synthesis of zinc oxide (ZnO) nanoparticles (NPs) using various plant extracts as reducing and capping agents has gained attention in recent research. The green synthesis of ZnO NPs offers several advantages such as being simple, eco-friendly, safe, cost-effective, and reproducible approach with high stability. Hence, this article provides an overview of zinc metal and ZnO compounds, and traditional chemical and physical synthesis of ZnO NPs with primary focuses on the green synthesis of ZnO NPs. This study discusses various plant extracts used and the proposed mechanisms in the green synthesis of ZnO NPs. Additionally, it explores the cytotoxic mechanisms of the green-synthesized ZnO NPs and addresses the various biomedical applications of ZnO NPs, including antibacterial, anticancer, antidiabetic, antioxidant, antifungal, antiviral, antiparasitic, anti-inflammatory, and wound healing. Moreover, the review critically discusses the toxicity of ZnO NPs and emphasizes the need for more toxicological studies to ensure the safety and facilitate the risk assessments and risk management of ZnO NPs. Furthermore, this review underlines the challenges associated with the translation process of ZnO NPs from bench to market, including the complex and time-consuming regulatory approval process for ZnO NPs, which requires a multidisciplinary approach involving scientists, regulators, and manufacturers.

Free zinc ions, as a major factor of ZnONP toxicity, disrupts free radical homeostasis in CCRF-CEM cells

Nanotechnology has become a ubiquitous part of our everyday life. Besides the already-known nanoparticles (NPs), plenty of new nanomaterials are being synthesized every day. Here, we explain the mechanism of the zinc oxide nanoparticles (ZnONPs) cytotoxicity in a cellular model of acute lymphoblastic leukaemia (CCRF-CEM). To do so, we investigated both possible hypotheses about the ZnONPs mechanism of toxicity: a free zinc ions release and/or reactive oxygen species (ROS) generation. Presented here results show that:A)EDTA protects the cells, whereas a common antioxidant agent (NAC) enhances the cytotoxic effect induced by ZnONPs,B)ZnONPs release zinc ions in vitro,C)ZnONPs upregulate the activity of antioxidative defence enzymes, which are Nrf2 transcription factor-dependent,D)The upregulation of ROS generation is correlated with the upregulation of reductive stress markers,E)ZnONPs treatment induces NADPH oxidases that cause excessive production of superoxide radicals in tested cellular model.Our results support the hypothesis that the mechanism of ZnONPs cytotoxicity is based on the release of free zinc ions. Nevertheless, both previously quoted hypotheses incompletely described the mechanism of action of ZnONPs. In this paper, we show that the mechanism of cytotoxicity of ZnONPs is based on the induction of reductive stress in CCRF-CEM cells, which is caused by free zinc ions released from ZnONPs. Therefore, the increase of oxidative stress markers is most likely a secondary response of the cells towards the Zn2+. These results provide a crucial expansion of the zinc ion hypothesis and thus explain the biphasic cellular response of CCRF-CEM cells treated with ZnONPs.

Toxicological effects of zinc oxide nanoparticles on hemato-biochemical profile of common carp (Cyprinus carpio)

Nanoparticles (NPs) are considered a major risk for aquatic ecosystemss, and zinc oxide nanoparticles (ZnO-NPs) are among generally utilized NPs in the modern era. Aquatic life cannot escalate away from the negative effects of NPs. This study aimed to evaluate the toxicity of ZnO-NPs on the the hemato-biochemical profile of Cyprinus carpio (C. carpio). 150C. carpio fish were tested; they had average weights of 108 g, lengths of 21.65 cm, and acclimated to typical living conditions while maintaining pH, temperature, and fresh aerations. Fish were given intraperitoneal injections (2–3 cm) deep into the abdominal cavity and were exposed to ZnO-NPs through aquatic means. Fish were exposed to biosynthesized ZnO-NPs via intraperitoneal injection at T4, 10, 15, and 20 ml/g body weight of fish and aquatic mode of exposure at T0, 0.00, T1, 1.00, T2, 2.00, and T3, 3.00 mg/L to each aquarium, respectively. The findings of the investigation demonstrated that exposure to ZnO NPs caused considerable modifications in the hematological and biochemical parameters of the fish. The hematological examination revealed significant changes in the RBC count, Hb, and Hct levels, which indicated the possibility of detrimental impacts on the fish's ability to transport oxygen. The biochemical study revealed significant shifts in the levels of serum total protein, albumin, globulin, and glucose, which pointed to the possibility of harm to the fish's liver and kidney functions. According to the findings of the study, exposure to ZnO nanoparticles can induce considerable variations in the hemato-biochemical profile of common carp, which indicates that there may be possible dangers to their general health and survival. The findings of this study underline the need of regulating the usage of these nanoparticles as well as their disposal in order to reduce the possible impact that they could have on aquatic ecosystems and on public health. The findings also highlight the need for more research to properly understand the effects of ZnO NPs on the health of fish and the ecosystem over the long term. In conclusion, the research makes a contribution to our understanding of the possible concerns connected with the use of ZnO NPs in a variety of industries and provides vital insights into the toxicological effects that these nanoparticles have on aquatic creatures. The findings could potentially be used to influence regulatory decisions on the use and disposal of ZnO NPs, with the objective of limiting the potential dangers that these particles pose to the environment and to public health.

Combined cytotoxicity of ZnO nanoparticles and chlorpyrifos in the rainbow trout, Oncorhynchus mikyss, gonadal cell line RTG-2

The toxicity of ZnO nanoparticles (ZnO NPs) in aquatic organisms has been extensively studied, but little information is available on the effects associated with their interaction with other contaminants. In this context, the in vitro effects of co-exposure of chlorpyrifos (CPF) and ZnO NPs on fish-derived cells were investigated. A selection of concentrations was tested in single and binary exposures: CPF (0.312 - 75 mg/L) and ZnO NPs (10 - 100 mg/L). Cytotoxicity was measured using commonly used cellular endpoints: Alamar Blue/CFDA-AM for viability and plasma membrane integrity, NRU for lysosomal disruption and MTT for mitochondrial function. In addition, specific mechanisms of toxicity for CPF and ZnO NPs were tested: acetylcholinesterase (AChE) activity and ROS generation, respectively. AChE was by far the most sensitive assay for single exposure to CPF. There was no concentration-response relationship for ROS after single exposure to ZnO NPs, but 10 mg/L produced significant effects only for this cellular endpoint. Co-exposure of CPF with 10 m/L of ZnO NPs produced significant effects in almost all endpoints tested, which were enhanced by co-exposure with 100 mg/L of ZnO NPs. AChE testing of additional co-exposures with bulk ZnO, together with the application of the Independent Action (IA) prediction model, which allowed us to draw more in-depth conclusions on the toxicological behavior of the mixture. Synergism was observed at 0.625 mg/L CPF concentration and antagonism at 5 mg/L CPF in mixtures containing 100 mg/L of both ZnO NPs and bulk ZnO. However, more cases of synergism between CPF and ZnO NPs occurred at intermediate CPF concentrations, demonstrating that nano-sized particles have a more toxic interaction with CPF than bulk ZnO. Therefore it can be argued that in vitro assays allow the identification of interaction profiles of NP-containing mixtures by achieving multiple endpoints with a large number of concentration combinations.

Interactive effects of temperature and salinity on toxicity of zinc oxide nanoparticles towards the marine mussel Xenostrobus securis

Growing application of zinc oxide nanoparticles (ZnO-NPs) in global market has led to the concern over their potential environmental impacts. Filter feeders like mussels are prone to nanoparticles due to their superior filter-feeding ability. Temperature and salinity of coastal and estuarine seawaters often vary seasonally and spatially, and their changes may jointly influence physicochemical properties of ZnO-NPs and thus their toxicity. This study, therefore, aimed to investigate the interactive effect of temperatures (15, 25 and 30 °C) and salinities (12 and 32 PSU) on physicochemical properties and sublethal toxicity of ZnO-NPs towards a marine mussel Xenostrobus securis, and to compare that with the toxicity caused by Zn2+ ions (zinc sulphate heptahydrate). The results revealed increased particle agglomeration but decreased zinc ion release of ZnO-NPs at the highest temperature and salinity condition (30 °C and 32 PSU). After exposure, ZnO-NPs significantly reduced survival, byssal attachment rate and filtration rate of the mussels at high temperature and salinity (30 °C and 32 PSU). Glutathione S-transferase and superoxide dismutase activities in the mussels were suppressed at 30 °C. These aligned with the augmented zinc accumulation with increasing temperature and salinity which could likely be attributable to increased particle agglomeration of ZnO-NP and enhanced intrinsic filtration rate of the mussels under these conditions. Together with the observed lower toxic potency of Zn2+ compared to ZnO-NPs, our results suggested that the mussels might accumulate more zinc through particle filtration under higher temperature and salinity, eventually resulting in elevated toxicity of ZnO-NPs. Overall, this study demonstrated the necessity to consider the interactive effect of environmental factors such as temperature and salinity during the toxicity assessment of nanoparticles.

Short-Term Toxicity of ZnO Nanoparticles on Microalgae at Different Initial Nutrient Concentrations

The aim of this work was to investigate the combined short-term toxic effect of zinc oxide (ZnO) nanoparticles (NPs) and nitrate concentration of the medium on freshwater microalgae. For this purpose, freshwater microalgae Chlorococcum sp. was cultivated in modified Blue-Green medium (BG-11) containing nitrate concentrations ranging from 0 to 300 mg/L, and exposed to ZnO NPs in different concentrations (0.081 to 810 mg/L) for a period up to 96 h. The experimental results revealed that algal growth was affected by the exposure time, NPs concentrations, and mainly the initial nitrate concentration. Differences in microalgae growth rates were observed. The toxic effect of ZnO NPs was higher on microalgae cultured in modified BG-11 with low and high nitrate concentrations. During the 4-day exposure, the highest growth rates were observed at 24 h at an initial nitrate concentration of 50 mg/L; 1.94 d−1 and 0.22 d−1 for 0 and 810 mg/L ZnO NPs, respectively. Nitrate uptake by algal biomass reached up to 40.1% after 96 h of operation in the control culture with an initial nitrate concentration of 50 mg/L. Finally, the results of this study showed the need for the investigation of ZnO NPs toxicity on microalgae under optimum and stressful nutrient conditions for microalgae growth.