Comparative toxicity of silver nanoparticle and ionic silver in juvenile common carp (Cyprinus carpio): Accumulation, physiology and histopathology

Effects of Silver Nanoparticles on Ctenopharyngodon idella: Synthesis, Characterization, Antibacterial Activity, and Toxicological Assessment

Currently, nanotechnology (NT) and nanoparticles (NPs) have gained significant attention in the scientific field due to their diverse application history. Particularly, in environmental applications, their antibacterial efficiency in fisheries due to antibacterial resistance. However, the NPs have been found toxic in the environment. Therefore, the current study aimed to fabricate less toxic NPs using environmentally dried leaves to check their antibacterial efficacy and possible toxicity against grass carp. The findings confirmed the good dispersity of obtained AgNPs, which further showed promising antibacterial activity against several bacterial isolates including Staphylococcus with a zone of inhibition (23.73 ± 0.57 nm). Also, the AgNPs were exposed to the grass carp (Ctenopharyngodon idella) for possible toxicity and toxic effects. First, the bioaccumulation of AgNPs was significantly observed in gills followed by intestines and muscles (p < 0.05). Finally, the AgNPs mainly accumulate in the liver, followed by the intestine, gills, and muscles. Additionally, the deposition of AgNPs in various organs resulted in histological alteration such as necrosis and infiltration of red blood cells in the intestine and the fusion of gill lamella. Hence, the synthesized NPs using dried leaf extract could be a promising approach in applied science. The significant features of the nanoparticles in the present work using green synthesis can help in synthesizing less toxic materials.

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.

Mass Spectrometry Imaging Reveals the Morphology-Dependent Toxicological Effects of Nanosilvers on Multiple Organs of Adult Zebrafish (Danio rerio)

Nanosilvers with multifarious morphologies have been extensively used in many fields, but their morphology-dependent toxicity toward nontarget aquatic organisms remains largely unclear. Herein, we used matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to investigate the toxicological effects of silver nanomaterials with various morphologies on spatially resolved lipid profiles within multiple organs in adult zebrafish, especially for the gill, liver, and intestine. Integrated with histopathology, enzyme activity, accumulated Ag contents and amounts, as well as MSI results, we found that nanosilvers exhibit morphology-dependent nanotoxicity by disrupting lipid levels and producing oxidative stress. Silver nanospheres (AgNSs) had the highest toxicity toward adult zebrafish, whereas silver nanoflakes (AgNFs) exhibited greater toxicity than silver nanowires (AgNWs). Levels of differential phospholipids, such as PC, PE, PI, and PS, were associated with nanosilver morphology. Notably, we found that AgNSs induced greater toxicity in multiple organs, such as the brain, gill, and liver, while AgNWs and AgNFs caused greater toxicity in the intestine than AgNSs. Lipid functional disturbance and oxidative stress further caused inflammation and membrane damage after exposure to nanosilvers, especially with respect to sphere morphology. Taken together, these findings will contribute to clarifying the toxicological effects and mechanisms of different morphologies of nanosilvers in adult zebrafish.

Developmental impacts and toxicological hallmarks of silver nanoparticles across diverse biological models

Silver nanoparticles (AgNPs), revered for their antimicrobial prowess, have become ubiquitous in a range of products, from biomedical equipment to food packaging. However, amidst their rising popularity, concerns loom over their possible detrimental effects on fetal development and subsequent adult life. This review delves into the developmental toxicity of AgNPs across diverse models, from aquatic species like zebrafish and catfish to mammalian rodents and in vitro embryonic stem cells. Our focus encompasses the fate of AgNPs in different contexts, elucidating associated hazardous results such as embryotoxicity and adverse pregnancy outcomes. Furthermore, we scrutinize the enduring adverse impacts on offspring, spanning impaired neurobehavior function, reproductive disorders, cardiopulmonary lesions, and hepatotoxicity. Key hallmarks of developmental harm are identified, encompassing redox imbalances, inflammatory cascades, DNA damage, and mitochondrial stress. Notably, we explore potential explanations, linking immunoregulatory dysfunction and disrupted epigenetic modifications to AgNPs-induced developmental failures. Despite substantial progress, our understanding of the developmental risks posed by AgNPs remains incomplete, underscoring the urgency of further research in this critical area.

Bio-reductive synthesis of silver nanoparticles, its antibacterial efficiency, and possible toxicity in common carp fish (Cyprinus carpio)

The biological synthesis of nanoparticles is an emerging field of study that seeks to synthesize nanoparticles using non-chemical mechanisms such as microorganisms, plants, and animal blood serum. Among these, plants have gained particular attention due to their ease of handling, availability, and ability to synthesize a wide range of nanoparticles. Therefore, the current study aimed to fabricate the silver nanoparticles (AgNPs) using Chinese medicinal plants (CMP) for their possible toxicity in common carp fish (Cyprinus carpio). For this purpose, CMP was dried, ground, and used as a bio-reductive agent. The fabricated AgNPs were characterized and a well dispersed AgNPs were obtained. Moreover, the C. carpio was exposed to the AgNPs for bioaccumulation and histological alterations. The obtained findings revealed that the AgNPs were mostly accumulated in the intestines followed by the gills, muscles, liver, and brain. The accumulated AgNPs caused histological alterations in gills and intestines at the highest concentration (0.08 mg/L). However, very less alterations were caused by the lowest concentration, especially in the intestine. In conclusion, further in-depth research is needed to determine the risks associated with the usage of nanoparticles to reveal their harmful impacts on fish and the aquatic environment. HIGHLIGHTS: The biological fabrication of AgNPs is considered eco-friendly. Chinese medicinal plants play a significant role in AgNPs synthesis. AgNPs have excellent antibacterial activity. AgNPs are bioaccumulated in various organs of fish.

Plant based synthesis of silver nanoparticles, antimicrobial efficiency, and toxicological assessment using freshwater fish (Cyprinus carpio)

Silver nanoparticles (AgNPs) are widely used and have various applications, including medicine, electronics, and textiles. However, their increasing use raises concern about their potential environmental impact, particularly on aquatic organisms, such as fish, which are the primary consumers of aquatic environments and can be exposed to AgNPs through various routes. For this purpose, the leaves of the plant species Bellis perennis were used as a reductive agent to convert silver nitrate into AgNPs, to assess its toxicity against fish. Well-dispersed and undersized AgNPs were obtained and confirmed using analytical techniques, including Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Moreover, the AgNPs have shown significant antibacterial activity against Aeromonas hydrophila (25.71 ± 0.63) and Vibrio harveyi (22.39 ± 0.29). In addition, the toxicity of the obtained AgNPs was assessed by exposing Cyprinus carpio to various concentrations, including 0.06, 0.1, and 0.2 mg/L. The findings revealed that the AgNPs were significantly accumulated in the intestine, followed by the gills, liver, muscles, kidney, and brain. This bioaccumulation led to histological alterations and destruction in the villi of the intestine, regeneration of liver cells, and degeneration of the gill lamella. RESEARCH HIGHLIGHTS: Plants based synthesis of AgNPs is mostly considered as eco-friendly A significant antibacterial activity was obtained The plant mediated AgNPs were found less toxic The AgNPs was profoundly accumulated and causes histological alterations.

The effects of 100 nm pure boron nanoparticles on the primary antioxidant system of Nile tilapia (Oreochromisniloticus)

In this study, the effects of 100 nm boron nanoparticles (B-NPs) on the primary antioxidant status of Nile tilapia were researched via analysis of enzyme activities and related gene expressions. This is a new study which focuses on the relationship between B-NPs and oxidative stress that contribute to the literature in terms of its scope. Fish (n = 15) for each group were exposed to three different concentrations as 5, 25 (n2) and 125 (n3) mg/L during 96 h to see the response of the primary antioxidant system. According to the results, SOD expressions differed in all treatment groups compared to the control group (P < 0.05). CAT expressions were different in 5 and 125 mg/L groups compared to control and 25 mg/L groups (P < 0.05). GPX expressions were only different in 125 mg/L group (P < 0.05). The changes in enzyme activities of SOD and CAT were significantly different in 25 mg/L groups. GPX enzyme activities were not significant (P > 0.05). TBARS concentrations in 25 mg/L group were significantly different from those in the control and 125 mg/L groups (P < 0.05).

Adverse effects of silver nanoparticles on aquatic plants and zooplankton: A review

With the rapid development of nanotechnology in the past decades, AgNPs are widely used in various fields and have become one of the most widely used nanomaterials, which leads to the inevitable release of AgNPs to the aquatic environment through various pathways. It is important to understand the effects of AgNPs on aquatic plants and zooplankton, which are widely distributed and diverse, and are important components of the aquatic biota. This paper reviews the effects of AgNPs on aquatic plants and zooplankton at the individual, cellular and molecular levels. In addition, the internal and external factors affecting the toxicity of AgNPs to aquatic plants and zooplankton are discussed. In general, AgNPs can inhibit growth and development, cause tissue damage, induce oxidative stress, and produce genotoxicity and reproductive toxicity. Moreover, the toxicity of AgNPs is influenced by the size, concentration, and surface coating of AgNPs, environmental factors including pH, salinity, temperature, light and co-contaminants such as NaOCl, glyphosate, As(V), Cu and Cd, sensitivity of test organisms, experimental conditions and so on. In order to investigate the toxicity of AgNPs in the natural environment, it is recommended to conduct toxicity evaluation studies of AgNPs under the coexistence of multiple environmental factors and pollutants, especially at natural environmental concentrations.

Multiple effects of ZnO nanoparticles on goldfish (Carassius auratus): Skin mucus, gut microbiota and stable isotope composition

The skin and the gut are direct target tissues for nanoparticles, yet attention to effects of metal-based nanoparticles (MNPs) on these two and the discrepancy in these effects remain inadequate. Here, effects of ZnO nanoparticles (nZnO) on skin mucus and gut microbiota of goldfish (Carassius auratus) were investigated, as well as further elements turnover and metabolic variations. After 14 days of exposure, considerable variations in levels of biomarkers (protein, glucose, lysozyme and immunoglobulin M) in skin mucus demonstrated significant stress responses to nZnO. nZnO exposure significantly reduced the abundance of Cetobacterium in the gut while increased that of multiple pathogens, and further leading to down-regulation of pathways such as carbohydrate metabolism, translation, and replication and repair. Decreased δ¹⁵N values indicated declined N turnover in vivo, further demonstrating the negative effect of nZnO on metabolism in the organism. Integration analysis of each biomarker using the biomarker response index version 2 (IBRv2) revealed concentration-dependent effects of nZnO on skin mucus, while effects on physiology in vivo was not, demonstrating the discrepancy in the toxicity pathways and toxic effects of nZnO on different tissues. This work improved our understanding about the comprehensive toxicity of nZnO on aquatic organism.

Metabolomics and mass spectrometry imaging reveal the chronic toxicity of indoxacarb to adult zebrafish (Danio rerio) livers

Indoxacarb is a widely used insecticide in the prevention and control of agricultural pests, whereas its negative effects on non-target organisms remain largely unclear. Herein, we demonstrated the integrated metabolomics and mass spectrometry imaging (MSI) methods to investigate the chronic exposure toxicity of indoxacarb at environmentally relevant concentrations in adult zebrafish (Danio rerio) liver. Results showed that movement behaviors of zebrafish can be affected and catalase (CAT), glutamic oxalacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) activities were significantly increased after indoxacarb exposure for 28 days. Pathological analysis of zebrafish livers also showed that cavitation and pathological reactions occur. Metabolomics results indicated that metabolic pathways of zebrafish liver could be significantly affected by indoxacarb, such as tricarboxylic acid (TCA) cycle and various amino acid metabolisms. MSI results revealed the spatial differentiation of crucial metabolites involved in these metabolic pathways within zebrafish liver. Taken together, these integrated MSI and metabolomics results revealed that the toxicity of indoxacarb arises from metabolic pathways disturbance, which resulted in the decrease of liver detoxification ability. These findings will promote the current understanding of pesticide risks and metabolic disorders in zebrafish liver, which provide new insights into the environmental risk assessment of insecticides on aquatic organisms.

Impact of acute and sub-acute exposure of magnesium oxide nanoparticles on mrigal Cirrhinus mrigala

This experiment was conducted to investigate the impact of acute and sub-acute exposure of magnesium oxide nanoparticles on Mrigal Cirrhinus mrigala. For sub-acute tests 1/100,1/50,1/10 were selected based on the LC₅₀ at 96 h s. Protein, carbohydrate, and lipid, Aspartate aminotransferase, alanine transaminase, lactate dehydrogenase and DPPH, HRSA assays were analyzed in the gill, muscle, and liver of Mrigal. Protein and lipid levels increased on the 7th,14th day compared to control. Carbohydrate levels decreased on the 7th,14th day of exposure, and the enzymatical changes increased on the 7^th,14th day. Antioxidant levels highly increased in DPPH assay compared to the HRSA assay. This study provides the biochemical, antioxidant, and behavioral changes in relation to the exposure of MgO NPs.

Effect of Quercetin Nanoparticles on Hepatic and Intestinal Enzymes and Stress-Related Genes in Nile Tilapia Fish Exposed to Silver Nanoparticles

Recently, nanotechnology has become an important research field involved in the improvement of animals' productivity, including aquaculture. In this field, silver nanoparticles (AgNPs) have gained interest as antibacterial, antiviral, and antifungal agents. On the other hand, their extensive use in other fields increased natural water pollution causing hazardous effects on aquatic organisms. Quercetin is a natural polyphenolic compound of many plants and vegetables, and it acts as a potent antioxidant and therapeutic agent in biological systems. The current study investigated the potential mitigative effect of quercetin nanoparticles (QNPs) against AgNPs-induced toxicity in Nile tilapia via investigating liver function markers, hepatic antioxidant status, apoptosis, and bioaccumulation of silver residues in hepatic tissue in addition to the whole-body chemical composition, hormonal assay, intestinal enzymes activity, and gut microbiota. Fish were grouped into: control fish, fish exposed to 1.98 mg L-1 AgNPs, fish that received 400 mg L-1 QNPs, and fish that received QNPs and AgNPs at the same concentrations. All groups were exposed for 60 days. The moisture and ash contents of the AgNP group were significantly higher than those of the other groups. In contrast, the crude lipid and protein decreased in the whole body. AgNPs significantly increased serum levels of ALT, AST, total cholesterol, and triglycerides and decreased glycogen and growth hormone (*** p < 0.001). The liver and intestinal enzymes' activities were significantly inhibited (*** p < 0.001), while the oxidative damage liver enzymes, intestinal bacterial and Aeromonas counts, and Ag residues in the liver were significantly increased (*** p < 0.001, and * p < 0.05). AgNPs also significantly upregulated the expression of hepatic Hsp70, caspase3, and p53 genes (* p < 0.05). These findings indicate the oxidative and hepatotoxic effects of AgNPs. QNPs enhanced and restored physiological parameters and health status under normal conditions and after exposure to AgNPs.

Accumulation, Chronicity, and Induction of Oxidative Stress Regulating Genes Through Allium cepa L. Functionalized Silver Nanoparticles in Freshwater Common Carp (Cyprinus carpio)

Green evolutionary products such as biologically fabricated nanoparticles (NPs) pose a hazard to aquatic creatures. Herein, biogenic silver nanoparticles (AgNPs) were synthesized by the reaction between ionic silver (AgNO₃) and aqueous onion peel extract (Allium cepa L). The synthesized biogenic AgNPs were characterized with UV-Visible spectrophotometer, XRD, FT-IR, and TEM with EDS analysis; then, their toxicity was assessed on common carp fish (Cyprinus carpio) using biomarkers of haematological alterations, oxidative stress, histological changes, differential gene expression patterns, and bioaccumulation. The 96 h lethal toxicity was analysed with various concentrations (2, 4, 6, 8, and 10 mg/l) of biogenic AgNPs. Based on 96 h LC₅₀, sublethal concentrations (1/15^th, 1/10^th, and 1/5^th) were given to C. carpio for 28 days. At the end of experiment, the bioaccumulations of Ag content were accumulated mainly in the gills, followed by the liver and muscle. At an interval of 7 days, the haematological alterations showed significance (p < 0.05) and elevation of antioxidant defence mechanism reveals the toxicity of biogenic synthesized AgNPs. Adverse effects on oxidative stress were probably related to the histopathological damage of its vital organs like gill, liver, and muscle. Finally, the fish treated with biogenic synthesized AgNPs were significantly (p < 0.05) downregulates the oxidative stress genes such as Cu-Zn SOD, CAT, GPx1a, GST-α, CYP1A, and Nrf-2 expression patterns. The present study provides evidence of biogenic synthesized AgNPs influence on the aquatic life through induction of oxidative stress.

Toxicological risks of SDHIs and QoIs to zebrafish (Danio rerio) and the corresponding poisoning mechanism

Quinone outside inhibitor fungicides (QoIs) and succinate dehydrogenase inhibitor fungicides (SDHIs) were classified as highly or moderately toxic to nontarget aquatic organisms, which deterred their application in paddy scenario. Currently, the mechanism of toxicity regarding which factors govern their risk ranking in fish species are not fully explored. In this study, adult zebrafish were exposed to four QoIs (pyraclostrobin, trifloxystrobin, kresoxim-methyl, and azoxystrobin) and three SDHIs (isopyrazam, thifluzamide, and boscalid) to assess its acute toxicity and effects on tissue accumulation and gill injury. The results showed that the overall toxicity level was in the order of QoIs > SDHIs, whereas the order of accumulation capacity was SDHIs > QoIs. Seven mitochondrial respiratory inhibitors exposure induced serious histological damage in the gills, including aneurism, curling, telangiectasia and swelling, and caused mitochondrial dysfunction and weaker complex II and III activities. The correlation between their acute toxicities and in vitro gill cytotoxicity was significant (R = 0.868), whereas the bioaccumulation level was not markedly associated with their 96h-LC₅₀ values in zebrafish (R = -0.686), indicating the degree of target organ (gill) injury may be the decisive factor that governs the risk grade of respiratory inhibitors in fish. Additionally, the docking positions and binding energies of fungicides with the target proteins may be responsible for their differential branchial damage. These results offer a point of reference and theoretical support for the design of fungicides and appropriate formulations with improved environmental safety that could broaden their application scenario.

Co-exposure of zinc oxide nanoparticles and multi-layer graphenes in blackfish (Capoeta fusca): evaluation of lethal, behavioural, and histopathological effects

Zinc oxide nanoparticles (ZnO NPs) and multi-layer graphenes (MLGs) are widely used, and due to the lack of appropriate wastewater treatment may end up in the aquatic environment, with unknown consequences to biota. The main purpose of this study was to assess the acute toxicity, histopathological and behavioural changes caused by the exposure of ZnO NPs and MLGs, alone and combined, to the blackfish Capoeta fusca. The estimated mean 96 h-LC₅₀ for ZnO NPs was 4.9 mg L^-1 and 68.4 mg L^-1 for MLGs. In combination, MLGs increased the acute toxicity of the ZnO NPs. The effects of the different NPs on the gills included hyperplasia, aneurisms, and fusion of the lamellae. In the intestine, exposure to the NPs resulted in an increase in the number and swelling of goblet cells and tissue degeneration. Loss of balance, restlessness, erratic and abnormal swimming patterns were the most common behavioural changes seen in the ZnO NPs' exposed blackfish. In contrast with the acute toxicity findings, MLGs decreased the histopathological and behavioural effects of the ZnO NPs on both gills and intestinal tissues as well as fish behaviour. Our experimental results illustrated insights into the simultaneous exposure assessment of metal-based NPs and carbon nanomaterials, although further research is needed on the interactions exposure of these substances to interpreting the toxicological effects of metal-based nanomaterials seen in exposed organisms.

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.

Toxicological Impacts on Antioxidant Responses, Stress Protein, and Genotoxicity Parameters of Aluminum Oxide Nanoparticles in the Liver of Oreochromis niloticus

The aim of this study was to determine the toxic effects of aluminum oxide nanoparticles (Al₂O₃ NPs) on oxidative stress, stress protein, and genotoxicity parameters in Oreochromis niloticus. Ninety-six-hour LC₅₀ value of Al₂O₃ NPs was found as 52.4 ppm for O. niloticus. The fish were exposed to 2.6 ppm (5% of the 96-h LC₅₀) and 5.2 ppm (10% of the 96-h LC₅₀) for 3 days and 7 days. Various biochemical parameters, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) activities, glutathione (GSH), thiobarbituric acid reactive substance (TBARS), heat shock protein 70 (HSP70; stress protein), and genotoxicity biomarker 8-hydroxy-2-deoxyguanosine (8-OHdG) levels, were determined. Results showed that antioxidant enzymes were significantly decreased in SOD, CAT, and GPx enzyme activity, but GST enzyme activity was significantly increased in 7 days. The oxidative stress parameters, GSH levels, were significantly decreased while 8-OHdG and TBARS levels were increased in 3 and 7 days. HSP70 levels were decreased in the concentrations of Al₂O₃ NPs and exposure times. Our results showed that as a result of changes in oxidative stress parameters, stress protein, and genotoxicity parameters, O. niloticus liver tissue is highly sensitive and toxic to aluminum oxide nanoparticle exposure.

Toxicity of Pb continuous and pulse exposure on intestinal anatomy, bacterial diversity, and metabolites of Pelophylax nigromaculatus in pre-hibernation

Amphibians are often exposed to pulse pollution due to fluctuational inputs of pollutants in water. Traditional ecotoxicology research is mainly performed under constant exposure conditions, which is not consistent with the true environmental pollution. Frogs are sensitive to changes in water pollutants in pre-hibernation. Thus, to understand the toxicity difference to continuous and pulse exposure in environmental concentrations of Pb (100 μg/L), Pelophylax nigromaculatus adults were exposed to short-term treatments (8 days) in pre-hibernation. Individual mortality, intestinal anatomical structure, bacterial diversity, and metabolites were measured in a control group (CON), a Pb continuous treatment group (CEPb) and a Pb pulse treatment group (PEPb). The results showed that PEPb significantly increased individual mortality, compared to the control group and CEPb. PEPb induced pathological changes in the small intestinal tissues, such as mucosal erosion, swollen and distorted villi, large vacuoles, and the proliferation of goblet cells. In addition, PEPb altered the structure and diversity of intestinal bacteria, resulting in an increase in some pathogenic bacteria (e.g. Bacteroides and Ruminococcus) and a decrease in beneficial bacteria (e.g. Cetobacterium and Akkermansia). Both CEPb and PEPb significantly changed intestinal metabolites and metabolic pathways. Moreover, PEPb has a significant effect on the metabolism of amino acids by increasing the content of 5-Aminopentanoic acid, cis-4-Hydroxy-l-proline, Glycocholic acid, l-Alanine, and l-Isoleucine. We concluded that PEPb may lead to intestine impairment of P. nigromaculatus in pre-hibernation by inducing intestinal structural integrity destruction, bacterial imbalance, and metabolic dysfunction, resulting in a significant increase in mortality. The study provides new insights for understanding the intestinal responses of frogs to pulse metal exposure.

Lambda-cyhalothrin-loaded nanocapsules pose an unacceptable acute toxicological risk to zebrafish (Danio rerio) at the adult and larval stages but present an acceptable risk to embryos

Recently, size-controlled pesticide microcapsule (MC) delivery systems have played an important role in precision farming development; however, the potential environmental hazards of MCs with different particle sizes have not been fully characterized. In this study, we prepared a series of lambda-cyhalothrin (LC)-MCs with nano and micron-scale capsule sizes (average diameters of 209.4 nm, MC-N; 2.41 µm, MC-S; 4.87 µm, MC-M; and 12.41 µm, MC-L). The assessment results showed that the release and sedimentation behavior of LC-MCs in water and toxicity to zebrafish at three life stages were all particle size-dependent. As the diameter distribution of approximately 100 nm extended to the micron scale (~27 µm), the capsules released more slowly and sunk more quickly in water. In addition, micron-sized LC-MC exposure resulted in significantly less fish mortality and malformations of larvae and embryos compared with nanosized LC-MC exposure. The highest accumulation of MC-N in the gill and the severest toxicity to larvae suggested that the smaller size and stronger permeability of nanocapsules would pose unpredictable consequences for nontargeted organisms. The obvious toxicological differences of LC-MCs toward aquatic organisms implies that regulating MC production in an appropriate size range is an important prerequisite for achieving efficient but safe pesticide applications.

Evaluation of the antibacterial influence of silver nanoparticles against fish pathogenic bacterial isolates and their toxicity against common carp fish

At present, nanotechnology and nanomaterials are being emerged very quickly and gained the attention of researchers due to their frequent application history, especially their antibacterial effects against certain bacterial isolates. Therefore, the present study was aimed to check the antibacterial influence and toxic effects of the market available (Chemical Fabricated) silver nanoparticles (AgNPs). For this purpose, the AgNPs were obtained from the local market and used against fish pathogenic bacterial species. The highest zone of inhibition was observed against Aeromonas hydrophila (27.53 ± 0.69). Moreover, the AgNPs were exposed to the common carp fish for toxicity and toxic effects. The highest mortality was seen at the highest concentration (0.09 mg/L) of AgNPs. Finally, the AgNPs mainly were accumulated in the liver, followed by the intestine, gills, and muscles. The intestine absorbed the nanomaterials; therefore, it is critical to check the influence of these AgNPs on the fish intestinal bacterial community via MiSeq Illumina Sequencing.

Sea Bass Primary Cultures versus RTgill-W1 Cell Line: Influence of Cell Model on the Sensitivity to Nanoparticles

Determination of acute toxicity to vertebrates in aquatic environments is mainly performed following OECD test guideline 203, requiring the use of a large number of fish and with mortality as endpoint. This test is also used to determine toxicity of nanomaterials in aquatic environments. Since a replacement method for animal testing in nanotoxicity studies is desirable, the feasibility of fish primary cultures or cell lines as a model for nanotoxicity screenings is investigated here. Dicentrarchus labrax primary cultures and RTgill-W1 cell line were exposed to several concentrations (0.1 to 200 ug/mL) of different nanoparticles (TiO₂, polystyrene and silver), and cytotoxicity, metabolic activity and reactive oxygen species formation were investigated after 24 and 48 h of exposure. Protein corona as amount of protein bound, as well as the influence of surface modification (-COOH, -NH₂), exposure media (Leibovitz’s L15 or seawater), weathering and cell type were the experimental variables included to test their influence on the results of the assays. Data from all scenarios was split based on the significance each experimental variable had in the result of the cytotoxicity tests, in an exploratory approach that allows for better understanding of the determining factors affecting toxicity. Data shows that more variables significantly influenced the outcome of toxicity tests when the primary cultures were exposed to the different nanoparticles. Toxicity tests performed in RTgill-W1 were influenced only by exposure time and nanoparticle concentration. The whole data set was integrated in a biological response index to show the overall impact of nanoparticle exposures.

Resistance and Resilience of Fish Gut Microbiota to Silver Nanoparticles

Understanding mechanisms governing the resistance and resilience of microbial communities is essential for predicting their ecological responses to environmental disturbances. Although we have a good understanding of such issues for soil and lake ecosystems, how ecological resistance and resilience regulate the microbiota in the fish gut ecosystem remains unclear. Using the zebrafish model, we clarified the potential mechanisms governing the gut microbiota after exposure to silver nanoparticles (AgNPs). Here, we explored the ecological resistance and resilience of gut microbiota in zebrafish exposed to different concentrations of AgNPs (i.e., 10, 33 and 100 μg/liter) for 15, 45, 75 days. The high-throughput sequencing analysis of the 16S rRNA gene showed that AgNP exposure significantly reduced the α-diversity of gut microbiota and resulted in obvious dynamics of community composition and structure. However, the rebound of zebrafish gut microbiota was pushed toward an alternative state after 15 days of AgNP exposure. We found that homogeneous selection was a more prevalent contributor in driving gut community recovery after AgNP exposure. The resilience and resistance of gut microbiota responses to AgNP disturbance might be mainly determined by the predominant keystone taxa such as Acinetobacter and Gemmata. This study not only expanded our understanding of fish gut microbiota's responses to pollutants but also provided new insights into maintaining host-microbiome stability during environmental perturbations. IMPORTANCE Understanding the ecological mechanisms governing the resistance and resilience of microbial communities is a key issue to predict their responses to environmental disturbances. Using the zebrafish model, we wanted to clarify the potential mechanisms governing the resistance and resilience of gut microbiota after exposure to silver nanoparticles (AgNPs). We found that AgNP contamination significantly reduced the α-diversity of gut microbiota and resulted in obvious changes in community composition. The resilience and resistance of gut microbiota to AgNPs might be associated with the predominant keystone taxa (e.g., Acinetobacter and Gemmata). This study greatly expanded our understanding of how fish gut microbiota responds to environmental perturbations and maintains stability.

Microscopic analysis of plant-mediated silver nanoparticle toxicity in rainbow trout fish (Oncorhynchus mykiss)

Over the years, nanoscience and the application of nanomaterials have gained the attention of researchers due to their enormous application history. Especially, the application of AgNPs providing innovative solutions to a wide range of environmental issues, for instance, wastewater treatment, bioremediations, and environmental sensing. Besides all these, the environmental application of silver nanomaterials causes severe problems in the terrestrial and aquatic ecosystems. For their concern, the present study was conducted to expose rainbow trout fish (Oncorhynchus mykiss) to different concentrations of silver nanoparticles for 25 days. In the current study, mortality (LC50 ), accumulation, and histopathological changes were analyzed. The results have revealed that the silver nanoparticles were mostly accumulated in the liver followed by the intestine, gill, and muscles. The microscopic analysis has shown that the accumulation of silver nanoparticles led to histological changes in gill and intestinal tissues. Necrosis, degeneration, mucus substance on the surface of gill lamella, cell lysis, and gill lamella atrophy were found at (0.04 mg/L) and (0.06 mg/L). The findings in the current study showed less toxicity in the sense of mortality and accumulation of AgNPs. Therefore, further systematic studies are needed to access the influence of silver nanoparticles on the aquatic ecosystem.

Metabolic profiling of nanosilver toxicity in the gills of common carp

Studies have shown silver nanoparticles (AgNPs) exposure can result in a series of toxic effects in fish gills. However, it is still unclear how AgNPs affect metabolite expression and their related molecular metabolic pathways in fish gills. In this study, we employed untargeted metabolomics to study the effects of AgNPs and silver supernatant ions on fish gill metabolites. The results showed that AgNPs can induce significant changes in 96 differentially expressed metabolites, which mainly affect amino acid metabolism and energy metabolism in fish gills. Among these metabolites, AgNPs specifically induce significant changes in 72 differentially expressed metabolites, including L-histidine, L-isoleucine, L-phenylalanine, and citric acid. These metabolites were significantly enriched in the pathways of aminoacyl-tRNA biosynthesis, ABC transporters, and the citrate cycle. In contrast, Ag⁺ supernatant exposure can specifically induce significant changes in 14 differentially expressed metabolites that mainly interfere with sphingolipid metabolism in fish gills. These specifically regulated fish gill metabolites include sphinganine, sphingosine, and phytosphingosine, which were significantly enriched in the sphingolipid metabolism pathway. Our results clearly reveal the effects and potential toxicity mechanisms of AgNPs on fish gill metabolites. Furthermore, our study further determined the unique functions of released silver ions in AgNPs toxicity in fish gills.

Toxicity, inflammatory and antioxidant genes expression, and physiological changes of green synthesis silver nanoparticles on Nile tilapia (Oreochromis niloticus) fingerlings

The rapid increase of incorporating silver nanoparticles (Ag-NPs) in different anthropogenic and industrial activities increased the discharge of these particles in the aquatic ecosystem. The environmental impact of Ag-NPs, especially the green synthesized is still not completely understood on fish. Therefore, this study aimed to investigate the effects of exposure to graded series of starch-mediated Ag-NPs at levels of 0, 3.31, 6.63, 13.25, and 26.50 mg L^-1 representing 0, 6.25, 12.5, 25, and 50% of LC₅₀ on Nile tilapia (O. niloticus), respectively. Fish with initial weight 37.63 ± 0.41 g were maintained in 70 L glass aquaria and exposed to starch-mediated Ag-NPs (average particle size 40 nm) for 28 days. The results revealed that starch-mediated Ag-NPs induced severe changes in the mRNA levels of toxicity (CYP1A and Hsp70) and inflammatory (TNF-α and TGF-β) genes. The expression of antioxidant genes (SOD and CAT) was significantly suppressed, and the activities of their enzymes were inhibited significantly upon exposure. Simultaneously, the malondialdehyde level increased significantly with increasing the exposure levels of starch-mediated Ag-NPs. The red blood cells, hemoglobin, hematocrit and white blood cell values were decreased significantly with doses over 3.31 mg L^-1 of Ag-NPs. In addition, the total protein and globulin decreased significantly with increasing Ag-NPs in a dose-dependent manner. The liver function enzymes and kidney function indicators revealed severe toxicity with Ag-NPs exposure. In conclusion, the effect of starch-mediated Ag-NPs in doses over 3.31 mg L^-1 induced obvious toxicity in the molecular and proteomic levels in Nile tilapia fingerlings.

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.

Comparative toxicity of multiple exposure routes of pyraclostrobin in adult zebrafish (Danio rerio)

Pyraclostrobin, one of the most widely used fungicides globally, is highly toxic to aquatic organisms, which restricts its application in paddy fields. Most studies have focused on the molecular mechanism of pyraclostrobin toxicity; however, the exposure routes and target organs of pyraclostrobin in fish are poorly known. Here, we found that the lethal effects of aquatic exposure, head immersion, trunk immersion and oral exposure on the toxicity and accumulation of pyraclostrobin in adult zebrafish were different. The major pathway leading to pyraclostrobin accumulation, followed by high hazard to fish, was crossing over the gill rather than the intestine or skin. Additionally, serious histological abnormalities, mitochondrial dysfunction, energy deficiency and respiratory impairment occurred in the gills, while no overt change was observed in the heart and brain at the organic and cellular levels. This result suggested that the gill is the dominant portal and target organ of pyraclostrobin in fish, a fact that has been further verified by intravenous injection. The differences in the toxicity and translocation factor of crystalline and dissolved pyraclostrobin in fish demonstrated that reducing the concentration in the branchial environment is a vital direction for the future design of an effective toxicity regulation strategy to protect key sites from pyraclostrobin attack.

Metal-based Green Synthesized Nanoparticles: Boon for Sustainable Agriculture and Food Security

The applications of metal-based nanoparticles (MNPs) in the sustainable development of agriculture and food security have received greater attention in recent years in the science community. Different biological resources have been employed to replace harmful chemicals to reduce metal salts and stabilize MNPs, i.e., green methods for the synthesis have paid attention to the nanobiotechnological advances. This review mainly focused on the applications of green synthesized MNPs for the agriculture sector and food security. Because of the novel domains, the green synthesized MNPs could be helpful in the different areas of agriculture like plant growth promotion, plant disease, and insect/pest management, fungicidal agent, in food security for food packaging, for increasing the shelf life and protection from spoilage, and other purposes. In the present review, the global scenario of the recent studies on the applications of green synthesized MNPs, particularly in sustainable agriculture and food security, is comprehensively discussed.

A dosage-effect assessment of acute toxicology tests of microplastic exposure in filter-feeding fish

Abundant microplastics was found in aquatic ecosystem and aquatic organisms, which raised many concerns in public. Silver carp (Hypophthalmichthys molitrix), a species filter-feeding planktivorous fish, feed on particle between 4 and 85 μm in size, and the respiratory process works together with feeding mechanism when filtering plankton from water. The aim of this study was to assess the physiological response of silver carp exposed to 5 μm polystyrene microspheres during 48 h of exposure followed by 48 h of depuration through the gill histology, and oxidative stress biomarkers in intestine. The results revealed that microplastics can pass through the whole digestive tract of silver carp and be excreted by feces. Low microplastic concentration (80 μg/L) induced oxidative stress and up-regulation of TUB84 and HSP70 gene in intestine, and silver carp have ability to recover after the exposure to microplastic was removed. High microplastic concentration (800 μg/L) definitely cause significant damage to gills and intestines, in this situation, far beyond the possibility of fish own repair, and even when the threaten removed, silver carp can't recovery soon. Our studies assessed the dosage-effect relationship with physiological stress on silver carp when exposure to microplastics.

Synthesis and characterization of palladium nanoparticles by chemical and green methods: A comparative study on hepatic toxicity using zebrafish as an animal model

Nanoparticles synthesized by chemical methods are of a matter of concern, whereas, the green methods are said to be eco-friendly and environmentally safe. In this study, the toxicity of palladium nanoparticles (Pd NPs) synthesized through chemical co-precipitation and green route method using Annona squamosa seed kernels (As-Pd NPs) were evaluated using zebrafish as an animal model. The synthesized nanoparticles (NPs) were characterized using UV-Visible spectroscopy, Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray (EDX), Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS) and Zeta potential. Zebrafish (Danio rerio) were exposed to 0.4 ng/L of Pd NPs and As-Pd NPs for 96-h, further oxidative stress parameters and histological changes were evaluated. The superoxide dismutase (SOD), catalase (CAT) activity and the lipid peroxidation (LPO) levels were elevated in the Pd NPs groups. But in the As-Pd NPs group, the SOD activity showed a biphasic nature while the CAT activity gradually declined till the 96-h compared to the control and Pd NPs groups. The LPO levels in the As-Pd NPs groups showed a measurable increase till 72-h and sudden decline at the end of 96-h. Anomalies in the histological changes such as ruptured hepatocytes, sinusoidal congestion, vacuolation and accumulation of erythrocytes were observed in both the NPs treated groups but As-Pd NPs exhibited lesser lesions than the control and Pd NPs groups. However, our present study reveals the possible reliability of the nanoparticles and the mechanism of scavenging activity suggesting that the As-Pd NPs synthesized by green route are less toxic comparing to the chemically synthesized Pd NPs.

Characterizing the effects of titanium dioxide and silver nanoparticles released from painted surfaces due to weathering on zebrafish (Danio rerio)

Silver (nAg) and titanium dioxide nanoparticles (nTiO₂) are common engineered nanoparticles (ENPs) added into paint for their antimicrobial and whitening properties, respectively. Weathering of outdoor painted surfaces can release such ENPs, though little is known about the potential effects of released ENPs on aquatic species. The objective of this study was to characterize the toxicity of nAg and nTiO₂ released from painted panels using fish liver cells (CRL2643) and zebrafish embryos (OECD 236 embryotoxicity test). Cells and embryos were exposed to suspensions of pristine nAg or nTiO₂, panels (unpainted or painted with nAg or nTiO₂) or base paint, after sonication. Cell viability and gene expression were assessed using resazurin assay and qPCR, respectively, while embryo mortality and deformities were scored visually via microscopic examination. In the cell studies, both paint-released nanoparticles did not affect viability, but paint-released nAg resulted in differential expression of a few genes including gclc and ncf1. In embryos, paint-released nAg increased mortality and incidence of deformities, whereas paint-released nTiO₂ resulted in differential expression of several genes including gclc, ncf1, txnrd1, gpx1b, and cyp1c1 but without major phenotypic abnormalities. Comparing the two types of exposures, paint-released exposures affected both molecular (gene expression) and apical (embryotoxicity) endpoints, while pristine exposures affected the expression of some genes but had no apical effects. The differing effects of paint-released and pristine nanoparticle exposures suggest that further research is needed to further understand how paint coatings (and the products of their weathering and aging) may influence nanoparticle toxicity to aquatic organisms.

Biological synthesis of silver nanoparticles using animal blood, their preventive efficiency of bacterial species, and ecotoxicity in common carp fish

Possible high biodeterioration of the microorganisms due to their metabolic pathway and activities on stone materials causes solemn problems in cultural heritage. Different kinds of laboratory-scale methods have been used for the reduction of microbial growth, that is, chemical, mechanical, and physical, which are cost-effective and not ecofriendly. In the current study, an ecofriendly approach utilizing silver nanoparticles were synthesized using sheep blood serum. Transmission electron microscopy results have confirmed the spherical and well dispersed silver nanoparticles with an average size of 32.49 nm, while energy dispersive X-ray has shown the abundance of silver nanoparticles. The efficiency against bacterial species was verified through laboratory-scale testing. The strong antibacterial activity was confirmed when B-AgNPs was tested against different bacterial species isolated from the Beishiku Cave Temple. The largest zone of inhibition was measured 26.48 ± 0.14 mm against Sphingomonas sp. while the smallest zone of inhibition measured was 9.70 ± 0.27 mm against Massilia sp. Moreover, these ecofriendly B-AgNPs were tested for daily based dose in different concentrations (0.03, 0.06, and 0.09 mg/L) against common carp fish for a long exposure (20 days) and 6.5% fatality was found. The highest lethal concentration (LC₅₀ ) for fish (0.61 ± 0.09 mg/L). No doubt, the laboratory scale applications have revealed the best results with minute toxicity in fish. Therefore, sheep serum should be continued to synthesize silver nanoparticles on a large scale. A strict monitoring system should be developed for the synthesis and application of AgNPs.

Does the adsorbent capacity of orange and banana peels toward silver nanoparticles improve the biochemical status of Oreochromis niloticus?

Silver nanoparticles (Ag NPs) have wide medical and industrial applications; therefore, their release into aquatic environments is a problematic issue. The present study aims to evaluate the removal efficiency of Ag NPs from water using orange peel (OP) and banana peel (BP) to moderate their toxicity on Oreochromis niloticus. Fish were divided into 4 groups: control group (dechlorinated tap water), Ag NPs (4 mg/L) exposed group, Ag NPs (4 mg/L) + OP (40 mg/L) group, and Ag NPs (4 mg/L) + BP (40 mg/L) group for 24 h, 48 h, and 96 h. The adsorptive ability of both peels was confirmed by scanning electron microscope and energy-dispersive X-ray spectroscopy after the exposure processes. The biochemical results revealed a gradual elevation in plasma glucose, total proteins, globulin, liver enzymes (AST, ALT, and ALP), creatinine, and uric acid after Ag NPs exposure, while albumin and total lipid concentrations were significantly decreased. The recorded antioxidant biomarkers in gills, and liver tissues after Ag NPs exposure showed severe oxidative damages (maximally after 96 h) as indicated by marked elevations in thiobarbituric acid reactive substances, glutathione peroxidase, catalase, and superoxide dismutase values, and decreased glutathione reduced content. All studied parameters restored more or less to that of control groups after OP and BP water treatment. The adsorbent abilities of both peels could reduce Ag NPs bioavailability and moderate their toxicological impacts.

Exposure to silver impairs learning and social behaviors in adult zebrafish

Silver and silver nanoparticles are used in several consumer products, particularly sterilizing agents. Ag⁺ released from the particles causes physiological damages of aquatic organisms. However, the effects of silver on neural and behavioral functions of fish remain unclear. Here, we used zebrafish as a model to investigate the impacts of silver on social, learning and memory behaviors in teleost. Adult zebrafish showed mortality rates of 12.875% and 100% on 72 h exposure to 30 and ≥ 50 ppb of silver nitrate, respectively. Silver accumulation in the brain increased on exposure to 10 and 30 ppb of AgNO₃. The physical fitness of the zebrafish, measured by novel tank diving test and swimming performance, decreased after 72 h incubation in 30 ppb of AgNO₃. Exposure to 10 ppb of AgNO₃ impaired social preference, social recognition, learning, and memory, but did not affect anxiety level, aggressiveness, and shoaling behavior. In situ hybridization of c-fos mRNA showed that AgNO₃ treatment decreased neural activity in the brain areas crucial for learning, memory, and social behaviors, including the medial and dorsal zones of the dorsal telencephalic area. In conclusion, 72 h exposure to AgNO₃ in a sublethal level impaired learning and social behaviors, indicating neurotoxicity in adult zebrafish.

Proteomic profiling reveals the differential toxic responses of gills of common carp exposed to nanosilver and silver nitrate

Although the toxic effects of silver nanoparticles (AgNPs) on fish gills have been reported, the underlying mechanism of toxicity remains unclear. The present study aimed to elucidate the mechanism of toxicity in the gills of common carp following exposure to AgNPs and silver nitrate (AgNO₃) using histopathology and proteomics. Histopathological findings revealed that both AgNPs and AgNO₃ caused telangiectasia and epithelial cell hyperplasia in fish gills; however, the pathological features and location of lesions caused by the two forms of silver were markedly different. Proteomics revealed that AgNPs and AgNO₃ induced 139 and 185 differential expression proteins (DEPs) in gills, respectively, and the two forms of silver induced only 42 shared proteins. AgNPs specifically induced 87 DEPs which mainly involved signaling mechanisms, cytoskeleton, and the arachidonic acid metabolism processes. AgNO₃ specifically induced 125 DEPs that were mainly clustered in the glutathione metabolism and protease processes. These results suggested that the toxic effects of AgNPs and AgNO₃ were dramatically different in terms of protein expression in fish gills, which may provide novel perspectives for understanding the toxicity mechanism of silver nanoparticles in fish gills.

Sex-dependent and organ-specific toxicity of silver nanoparticles in livers and intestines of adult zebrafish

Silver nanoparticles (AgNPs) have been increasingly manufactured and thus are increasingly detected in aquatic systems. However, there are still some overlooked factors (e.g., organism sex) in the field of nano-toxicological assessment. In this study, to explore the role of sex in nanotoxicity, adult male and female zebrafish were exposed to 100 μg/L of two uncoated commercial AgNPs with primary sizes 20 nm and 80 nm for 2 weeks, after which the impacts of AgNPs on intestines and livers of both male and female zebrafish were assessed using a suite of biomarkers. Results demonstrated that the intestinal Na/K-ATPase activity as well as the superoxide dismutase activity in male zebrafish differed significantly between 20-nm AgNPs and 80-nm AgNPs treatments (p < 0.05), indicating 20-nm AgNPs showing higher toxicity to zebrafish than the 80-nm AgNPs. Also, we noted that the used AgNPs induced sex-dependent effects on growth indices, oxidative/anti-oxidative status, neural signaling and hepatic lipid metabolism, with the male zebrafish being more sensitive to AgNPs than the females. Further, the tested AgNPs impaired the intestine much more seriously than the liver, as evidenced by the disruptions of Na/K-ATPase and antioxidant system in intestine but not in liver. These findings imply that prolonged exposure to AgNPs might induce size-related, sex-dependent, and organ-specific toxicity to adult zebrafish, thereby may significantly extend our understanding of the toxic effects of AgNPs in aquatic environment.

Silver nanoparticles: Toxicity in model organisms as an overview of its hazard for human health and the environment

Silver nanoparticles (AgNPs) have attracted remarkable attention due to their powerful antimicrobial action as well as their particular physicochemical properties. This has led to their application in a wide variety of products with promising results. However, their interaction with the environment and toxicity in live terrestrial or aquatic organisms is still a matter of intense debate. More detailed knowledge is still required about the toxicity of AgNPs, their possible uptake mechanisms and their adverse effects in live organisms. Several studies have reported the interactions and potential negative effects of AgNPs in different organisms. In this review, we report and discuss the current state of the art and perspectives for the impact of AgNPs on different organisms present in the environment. Recent progress in interpreting uptake, translocation and accumulation mechanisms in different organisms and/or living animals are discussed, as well as the toxicity of AgNPs and possible tolerance mechanisms in live organisms to cope with their deleterious effects. Finally, we discuss the challenges of accurate physicochemical characterization of AgNPs and their ecotoxicity in environmentally realistic conditions such as soil and water media.

Surface charge-dependent bioaccumulation dynamics of silver nanoparticles in freshwater algae

Silver nanoparticles (AgNPs) can gradually accumulate in algae to exert their toxicity; however, there is little knowledge about their bioaccumulation dynamics. For the first time, this study reports the effect of surface charge of AgNPs on their bioaccumulation dynamics in freshwater algae (Chlorella vulgaris) using biodynamic modeling. Polyethylene-coated AgNPs (PEI-AgNPs) and citrate-coated AgNPs (Cit-AgNPs) were selected as positively and negatively charged AgNPs, i.e., P-AgNPs and N-AgNPs, respectively. Their uptake and elimination dynamics were investigated at a concentration of 50% inhibition of growth rate values (EC₅₀) and 10% inhibition of growth rate values (EC₁₀). The one-component model can generally well simulate the algal uptake and elimination kinetics of N-AgNPs but not of P-AgNPs. At both concentrations, the uptake rate constants (k_u) for P-AgNPs were ∼20 times higher than that for N-AgNPs. The parameters of biphasic elimination kinetics revealed that P-AgNPs were eliminated faster than N-AgNPs during depuration compared to in subsequent processes. Compared with N-AgNPs, extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and dark-field imaging revealed that P-AgNPs can be rapidly absorbed on the algal cell surface membrane owing to their remarkably lower energy barrier between algal cells, resulting in a faster adsorption/uptake process and aggregation of algal cells. Our results clearly demonstrate that the AgNPs exhibited surface charge-dependent bioaccumulation dynamics in algal cells. Thus, AgNP surface charge primarily influences the AgNP accumulation dynamics in algal cells.

The effects of silver nanoparticles (Ag-NPs) sublethal concentrations on common carp (Cyprinus carpio): Bioaccumulation, hematology, serum biochemistry and immunology, antioxidant enzymes, and skin mucosal responses

The present study aimed to evaluate the effects of different waterborne sublethal concentrations of Ag-NPs LC₅₀ (96h) on common carp Cyprinus carpio using a multi-biomarker approach. Fish (9.22 ± 0.12 g) were stocked in fiberglass tanks and exposed to concentrations of 0 (control), 12.5%, 25% and 50% of Ag-NPs LC₅₀ (96h) or Ag-NO₃ LC₅₀ (96h), as the source of Ag⁺ ion, for a period of 21 days. At the end of study, tissue Ag contents were significantly (P < 0.05) higher and different in fish exposed to concentrations of 25% and 50% compared to the control. The numbers of RBCs, hematocrit, and MCHC values at these concentrations differed significantly in respect to the control. No significant effects were observed for hemoglobin, MCH, and MCV values. The number of WBCs was significantly higher at concentrations of 12.5% and 25% compared to the control. Meanwhile, the percentage of neutrophils significantly elevated at concentrations of 25% and 50%. Serum total protein at concentration of 50% detected significantly lower than that of 12.5% or the control. The serum albumin and globulin levels significantly declined in Ag-NPs-exposed groups versus the control. The serum ACH50 and total immunoglobulins showed significantly lower values in the treatments of 25% and 50% compared to the control. The serum glucose, cortisol, ALT, and ALP values significantly escalated upon Ag-NPs exposure. The serum SOD and CAT showed enhanced activity in the treatment of 12.5% vice versa significantly diminished at concentrations of 25% and 50% compared to the control. The exposure to the concentrations of 25% and 50% significantly dwindled the lysozyme activity and total immunoglobulin levels in skin mucus. In conclusion, sublethal concentrations of Ag-NPs LC₅₀ (96h) impaired fish health status at higher concentrations and 12.5% of Ag-NPs LC₅₀ (96h) was presumably safe for common carp aquaculture.

Salinity modulates biochemical and histopathological changes caused by silver nanoparticles in juvenile Persian sturgeon (Acipenser persicus)

The objective of this study was to evaluate the effect of salinity on the acute and sub-chronic toxicity of silver nanoparticles (AgNPs) in Persian sturgeon. This was evaluated by exposing Persian sturgeon to AgNPs in three salinities: freshwater (F: 0.4 ppt), brackish water 1 (B₁: 6 ± 0.2 ppt), and brackish water 2 (B₂: 12 ± 0.3 ppt) for 14 days, which was followed by analysis of alterations in plasma chemistry and histopathology of the gills, liver, and intestine. Values of 96-h median lethal concentration (LC₅₀) were calculated as 0.89 mg/L in F, 2.07 mg/L in B₁, and 1.59 mg/L in B₂. After sub-chronic exposures, plasma cortisol, glucose, potassium, and sodium levels illustrated no significant changes within each salinity level. In F, 0.2 mg/L AgNP caused the highest levels of alkaline phosphatase and osmolality levels. In B₁, 0.6 mg/L AgNP induced the highest level of alkaline phosphatase and elevated plasma osmolality was recorded in all AgNP-exposed treatments in comparison with the controls. The B₂ treatment combined with 0.6 mg/L AgNP significantly reduced plasma chloride level. The results showed elevating salinity significantly increased osmolality, chloride, sodium, and potassium levels of plasma in the fish exposed to AgNPs. The abundance of the tissue lesions was AgNP concentration-dependent, where the highest number of damages was observed in the gills, followed by liver and intestine, respectively. The histopathological study also confirmed alterations such as degeneration of lamella, lifting of lamellar epithelium, hepatic vacuolation, pyknotic nuclei, and cellular infiltration of the lamina propria elicited by AgNPs in the gills, liver, and intestine of Persian sturgeon. In conclusion, the stability of AgNPs in aquatic environments can be regulated by changing the salinity, noting that AgNPs are more stable in low salinity waters.

Effects of reduced graphene oxide on humic acid-mediated transformation and environmental risks of silver ions

The reduction of Ag⁺ mediated by natural organic matters has been demonstrated to be an important process of Ag⁺ transformation and would influence the risks of Ag⁺ and Ag-containing materials in aquatic environment. Considering the large production of carbon nanomaterials (CNMs) and their inevitable release into the environment, the effects of CNMs on Ag transformation are of considerable interest. This study demonstrated that the humic acid-mediated reduction of Ag⁺ to free Ag nanoparticles (AgNPs) in aqueous phase was suppressed by coexisting reduced graphene oxide (rGO). A large amount of Ag⁺ was reduced on rGO surface, resulting in the generation of AgNPs-rGO composites. rGO at concentrations of 1-2 orders of magnitude lower than those of Ag⁺ would exhibit significant effects. The X-ray absorption fine structure spectroscopy study showed that Ag⁺ was first adsorbed on rGO surface cooperatively with humic acid and then rapidly reduced to AgNPs. The hydroxylic-OH on rGO could participate in the AgNPs formation and was oxidized to carbonyl during the reduction of Ag⁺. Additionally, the formed AgNPs-rGO had a relatively lower environmental risk compared to AgNPs or rGO alone. Overall, these results improve our understanding of the interaction between CNMs and Ag⁺ in aquatic systems.

Effects of L-Glufosinate-ammonium and temperature on reproduction controlled by neuroendocrine system in lizard (Eremias argus)

In the context of global warming, an important issue is that many pesticides become more toxic, putting non-target organisms at higher risk of pesticide exposure. Eremias argus (a native Chinese lizard) was selected as animal model in this study. As a kind of poikilothermic vertebrate, E.argus is sensitive to temperature change. The experimental design [(with or without L-Glufosinate-ammonium (L-GLA) pollution × two temperatures (25 and 30 °C)] was used in this study for 90 days to identify the chronic effects of the pesticide-temperature interaction on the lizards' neuroendocrine-regulated reproduction. Survival rate, body weight, clutch characteristics, testicular histopathology, the content of neurotransmitters and related enzyme activity, the level of sex steroid, the expression of Heat shock protein 70 (HSP70), antioxidant system, the accumulation and degradation of L-GLA were examined. Results showed that L-GLA disrupt reproduction of lizards through hypothalamus-pituitary-gonad (HPG) axis. In addition, temperature can not only change the environmental behavior of pesticides, but also alter the physiological characteristics of lizards. Thus, our results emphasized that temperature is an essential abiotic factor that should not be overlooked in ecotoxicological studies.

Effect of silver nanoparticles on gill membranes of common carp: Modification of fatty acid profile, lipid peroxidation and membrane fluidity

Although the toxicity of silver nanoparticles (AgNPs) in aquatic organisms has been extensively investigated, the mechanism by which AgNPs damage membranes remains unclear. This study investigated the toxic effects of a series of sub-lethal concentrations of AgNPs on the membranes of freshwater carp (Cyprinus carpio) gills, based on changes in membrane fatty acid (FA) profile, membrane fluidity, membrane lipid peroxidation, and histopathology. Most of the FAs in fish gill membrane was not significantly affected by exposure to multiple AgNPs concentrations, only few significant changes occurred in some specific FAs species at a high concentration of AgNPs exposure. In particular, high concentrations of AgNPs significantly decreased the proportions of two important long-chain n-3 series polyunsaturated FAs (C20: 5n3, and C22: 6n3), resulting in a decreased ratio of n-3 polyunsaturated FAs to n-6 polyunsaturated FAs (Σn-3UFA/Σn-6UFA). The AgNPs also caused a dose-dependent decrease in fish gill membrane fluidity, increased the level of lipid peroxidation, and inhibited Na⁺/K⁺-ATPase enzyme activity. Further histopathological examination revealed that exposure to AgNPs can cause toxic responses in the lamellae, including the thinning of the basement membrane, malformation, and inflammation. Together, the results suggest that the mechanism of AgNPs membrane toxicity involves the oxidization of long-chain omega-3 unsaturated FAs to saturated FAs via lipid peroxidation, resulting in, decreased membrane fluidity and ultimately the destruction of the normal physiological function of the fish gill membrane. The findings contribute significantly to our understanding of nanoparticle-induced membrane toxicity and potential risks in aquatic environments.

Will the antimicrobial properties of ZnONPs turn it into a more suitable option than AgNPs for water filtration? Comparative study in the removal of fish pathogen, Aeromonas hydrophila from the culture of juvenile common carp (Cyprinus carpio)

The purpose of this study was to investigate the possibility of using zinc oxide nanoparticles (ZnONPs) instead of silver nanoparticles (AgNPs) for removing Aeromonas hydrophila from water used to culture Cyprinus carpio juvenile. Antibacterial materials as filter media were prepared by coating ZnONPs (two coating methods, referred as ZnA and ZnB) or AgNPs (referred as Ag) on the porous surfaces of zeolite beads. The characterization of coated samples was determined using FESEM, EDS, and GFAAS. The antibacterial activities of prepared samples were evaluated by the zone of inhibition test, tube test, and flow test. The diameter of inhibitory zones formed by ZnONP- and AgNP-coated zeolite beads was significantly higher than uncoated zeolite (control) (P < 0.05). Also, the tube test results revealed 100% killing of the bacterial cells after 24 h of contact to all coated materials. In the flow test (without fish), the antibacterial efficiency of filter columns that contained ZnA, ZnB, and Ag found to be 34.84, 23.77, and 100% after 96 h, respectively. The mortality rate of carp juveniles cultured in infected water treated with AgNP filters was significantly lower than those cultured in infected water or treated with ZnONPs filters (P < 0.05). The results indicated that although ZnONP filter media have somewhat antimicrobial properties (especially in vitro), their ability to complete removal of microorganisms from the water is not as high as AgNP filters. So, it still seems that zeolite coated with AgNPs has a higher potential for water disinfection in aquaculture.

Combination analysis of the physiology and transcriptome provides insights into the mechanism of silver nanoparticles phytotoxicity

Silver nanoparticles (AgNPs) have adverse impacts on plants when released into environments, but their toxic mechanism is still a matter of debate. Here we present a combined analysis of physiology and transcriptome of Arabidopsis thaliana leaves exposure to 30 mg L^-1 AgNPs and Ag⁺ for six days to explore the toxicity mechanism of AgNPs on Arabidopsis. Both transcriptomic and physiological results showed that AgNPs induced reactive oxygen species (ROS) accumulation and damaged photosynthesis. The toxicity of AgNPs is not merely attributable to Ag⁺ release and much higher photosynthetic toxicity and ROS accumulation were observed in 30 mg L^-1 AgNPs than that in 0.12 mg L^-1 Ag⁺. About 60% genes were similarly up- or down-regulated at the same concentration of AgNPs and Ag⁺ and these genes were enriched in photosynthesis and response to the stimulus. However, 302 genes, including those involved in glucosinolates synthesis, were specifically regulated under AgNPs treatments. In conclusion, more than the released Ag⁺, nanoparticle-specific effects are responsible for the toxicity of AgNPs in Arabidopsis thaliana.

The effect of biogenic manufactured silver nanoparticles on human endothelial cells and zebrafish model

Human health and environment have been continuously getting exposure to toxic chemicals including nanomaterial; therefore, nontoxicity has recently attracted huge amount of attention. In this study, RU-AgNPs were synthesized by a green synthesis procedure and evaluated for their toxicity in human umbilical vein endothelial cells (HUVECs) as well as on zebrafish embryos via apoptotic pathway. The synthesized RU-AgNPs were average in size (20-25 nm) with a negative surface charge of -13.43 mV. As a result, RU-AgNPs potentiated the formation of reactive oxygen species (ROS) in HUVECs as confirmed by the results of immunoblotting analysis using apoptotic markers, such as Bax, Bcl2, and cytochrome C. Moreover, the induction of apoptosis in HUVECs was also authenticated in a dose-dependent manner after the treatment with RU-AgNPs by the Incucyte analysis. In vivo trials conducted on zebrafish visualized the mortality, malformation, and imbalanced in the heart rate, and cell death of the whole embryo, including severe morphological changes in the yolk sac and the tail of zebrafish. Furthermore, the results of western blot analysis demonstrated the increasing intensity of apoptotic biomarkers such as Bax, Bcl2, and Cyto C, including enhanced production of ROS, validating the cell death in zebrafish larvae. In addition, chemically functionalized silver nanoparticles found to be more cytotoxic than biogenic functionalized silver nanoparticles. Above-mentioned findings clearly demonstrate that Ru-AgNPs cause the toxicity via ROS-induced apoptotic pathway. Therefore, it is necessary to decide RU-AgNPs toxicity levels before being used in any biomedical application.