Toxicological Effects Induced by Silver Nanoparticles in Zebra Fish (Danio Rerio) and in the Bacteria Communities Living at Their Surface

Acidified water promotes silver-induced toxicity in zebrafish embryos

Freshwater acidification is a global environmental challenge, yet the effects of acidic water on fish resistance to toxic Ag+ remain an unexplored area. To address this knowledge gap, zebrafish embryos were exposed to different concentrations (0 (control), 0.1, and 0.25 mg/L) of AgNO3 under pH 5 or 7 for 7 days. Notably, AgNO3 at 0.25 mg/L resulted in 100 % mortality in both pH conditions, while AgNO3 at 0.1 mg/L resulted in higher mortality at pH 5 (85 %) compared to pH 7 (20 %), indicating that acidic water enhanced Ag+ toxicity. Several parameters, including body length, inner ear (otic vesicle and otolith) and yolk sac areas, lateral line hair cell number and morphology, the number of ionocytes (H+-ATP-rich cells and Na+/K+-ATP-rich cells), and ion contents (Ag+, Na+, and Ca2+) were assessed at 96 h (day 4) to investigate individual and combined effects of Ag+ and acid on embryos. Acid alone did not significantly alter most parameters, but it decreased the yolk sac area and increased the ionocyte number. Conversely, Ag+ alone caused reductions in most parameters, including body length, the inner ear area, hair cell number, and ionocyte number. Combining acid and Ag+ resulted in greater suppression of the otolith area, hair cell number, and Na+/Ca2+ contents. In conclusion, acidification of freshwater poses a potential risk to fish embryo viability by increasing their susceptibility to silver toxicity, specifically affecting sensory function and ion regulation.

Nanosilica and copper ecotoxicity in Gambusia holbrooki fish

When silica nanoparticles (SiNP) reach the water bodies interact with the already existing pollutants in the environments. This study aimed to evaluate the ecotoxicity of SiNP under the presence/absence of Cu in mosquitofish (Gambusia holbrooki). Fish were exposed to 0, 10 and 100 mg SiNP L-1, alone or mixed with Cu (0.25 mg L-1). After 96 h, the amount of colony forming units (CFU) of bacteria living on the skin mucus was analysed, and oxidative stress, tissue damage enzymes, and neurotoxicity were evaluated. We observed a reduction in CFU when Cu was present in the media. The liver was the target organ, evidencing a decrease in tissue damage enzymatic activities, activation of the antioxidant system in all treatments, and lipid oxidative damage when the SiNP and Cu were mixed. Overall, SiNP ecotoxicity was proved, which could also be enhanced by the presence of ubiquitous elements such as metals.

Toxicity assessment of lead, nickel and cadmium on zebra fish augmented with Bacillus xiamenensis VITMSJ3: An insight on the defense mechanism against oxidative stress due to heavy metals

Increase urbanization in recent years has let to discharge of heavy metals into the environment which has caused severe impacts on soil as well as water. Therefore the current study was aimed to assess the toxicity of lead (Pb), nickel (Ni), and cadmium (Cd) from the contaminated water using zebra fish Danio rerio and detoxification of metals upon augmentation with Bacillus xiamenensis. Exposure doses till 150 mg L^-1 of Pb, Ni and Cd in water showed lethal effects on fish. Similarly the histopathological analysis showed severe tissue disruption in the gills and liver which were less upon supplementation with bacterial strain VITMSJ3. On the 20th day, the uptake concentration of Pb, Ni and Cd in zebra fish was found to be 87 mg L^-1, 89 mg L^-1 and 91 mg L^-1 respectively with VITMSJ3, from the water. Antioxidant enzymatic activities showed an increase upon bacterial supplementation, which reduced the oxidative stress. Further SEM-EDAX analysis confirmed the presence of Pb, Ni and Cd ions adsorbed on the gills. The results clearly showed less oxidative damages in fish with increased head and reduced tail %. Overall, the results showed a significant difference (p < 0.05) among the treatments compared with the control.

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.

Acute Exposure to Biogenic Nanosilver Produced from Fusarium oxysporum in a Neotropical Fish

Biogenic nanosilver (bNAg) has emerged as a potentially less toxic alternative to synthetic nanosilver. However, no studies have evaluated its effects on a fish species from the Neotropical region. Thus, our aim was to evaluate the effects of a bNAg on the Neotropical fish Prochilodus lineatus. For this purpose, after 24 h of exposure to 100 µg L^-1 of bNAg, blood samples were collected to evaluate hematological, genotoxic, and plasma parameters. Gills and liver were sampled to evaluate biomarkers of oxidative stress and brain samples were used to assess neurotoxicity. The fish presented hyperglycemia, an increased number of erythrocytes, a reduction in antioxidant enzyme activity in both tissues evaluated, and a decrease in lipid peroxidation in the gills. We concluded that P. lineatus is a sensitive species to this nanoparticle, since it presented alterations in several biomarkers after an acute exposure.

Nanosilver and Silver Nitrate Toxicity in Ex Vivo-Exposed Gills of Fish and Mitigation by Humic Acids

Silver nanoparticles (AgNP) are unique because of their biocide properties. Once released to environment, AgNP interact with the natural organic matter which impact on their fate, dispersion, and ultimate toxicity. We carried out an ex vivo exposure of gill of Corydoras paleatus fish to 100 µg L^-1 of AgNP or AgNO₃, alone and in combination with 10 mg L^-1 of humic acids (HA), with the aim to evaluate the potential mitigation of HA on AgNP toxic effects. We analyzed Ag accumulation and oxidative stress biomarkers. The results showed high bioaccumulation after the AgNO₃+HA exposure. An inhibition of glutathione-S-transferase enzymatic activity and depletion of reduced glutathione levels were registered after the AgNO₃ exposure, and increased lipid peroxidation levels in the case of AgNP one. Oxidative responses were mitigated when the HA were present in the media. Overall, the knowledge about the fate of this emergent pollutant was deepened through this study.

Mitigation of silver nanoparticle toxicity by humic acids in gills of Piaractus mesopotamicus fish

Silver nanoparticles (AgNPs) are one of the most produced nanoproducts due to their unique biocide properties. The natural organic matter has an important impact on nanoparticle's dispersion as it may alter their fate and transport, as well as their bioavailability and toxicity. Therefore, this study aimed to evaluate the mitigatory effect of humic acids (HAs) on AgNP toxicity. For this purpose, we carried out an ex vivo exposure of gill of Piaractus mesopotamicus fish to 100 μg L^-1 of AgNPs or AgNO₃, alone and in combination with 10 mg L^-1 of HAs. In parallel, a complete AgNP characterization in the media, including the presence of HAs, was provided, and the Ag⁺ release was measured. We analyzed Ag bioaccumulation, antioxidant enzymes activities, lipid peroxidation, antioxidant capacity against peroxyl radicals, and reduced glutathione levels in fish tissue. Our results indicated the Ag⁺ release from AgNPs decreased 28% when the HAs were present in the media. The Ag accumulation in gill tissue exposed to AgNPs alone was higher than the AgNO₃ exposure, and sixfold higher than the treatment with the HA addition. Moreover, after both Ag forms, the catalase enzyme augmented its activity. However, those responses were mitigated when the HAs were present in the media. Then, our results suggested the mitigation by HAs under the exposure to both Ag forms, providing valuable information about the fate and behavior of this emergent pollutant.

Commentary: Revisiting nanoparticle-assay interference: There's plenty of room at the bottom for misinterpretation

Engineered nanomaterials (ENMs) are a diverse class of materials whose distinct properties make them desirable in a multitude of applications. The proliferation of nanotoxicology research has improved our understanding of ENM toxicity, but an under appreciation for their potential to interfere with biochemical assays has hampered progress in the field. The physicochemical properties of ENMs can promote their interaction with membranes or biomacromolecules (e.g. proteins, genomic material). This can influence the activity of enzymes used as biomarkers or as reagents in biochemical assay protocols, bind indicator dyes in cytotoxicity tests, and/or interfere with the cellular mechanisms controlling the uptake of such dyes. The spectral characteristics of some ENMs can cause interference with common assay chromophores, fluorophores, and radioisotope scintillation cocktails. Finally, the inherent chemical reactivity of some ENMs can short circuit assay mechanisms by directly oxidizing or reducing indicator dyes. These processes affect data quality and may lead to significant misinterpretations regarding ENM safety. We provide an overview of some ENM properties that facilitate assay interference, examples of interference and the erroneous conclusions that may result from it, and a number of general and specific recommendations for validating cellular and biochemical assay protocols in nanotoxicology studies.

Zebrafish as an Emerging Model System in the Global South: Two Decades of Research in Brazil

The zebrafish (Danio rerio) is an emerging model system in several research areas worldwide, especially in the Global South. In this context, the present study revised the historical use and trends of zebrafish as experimental models in Brazil. The data concerning the bibliometric parameters, research areas, geographic distribution, experimental design, zebrafish strain, and reporter lines, as well as recent advances were revised. In addition, the comparative trends of Brazilian and global research were discussed. Revised data showed the rapid growth of Brazilian scientific production using zebrafish as a model, especially in three main research areas (Neuroscience &and Behavior, Pharmacology and Toxicology, and Environment/Ecology). Studies were conducted in 19 Brazilian states (70.37%), confirming the wide geographic distribution and importance of zebrafish research. Results indicated that research related to toxicological approaches are widespread in Global South countries such as Brazil. Studies were performed mainly using in vivo tests (89.58%) with adult fish (59.75%) and embryos (30.67%). Moreover, significant research gaps and recommendations for future research are presented. The present study shows that the zebrafish is a suitable vertebrate model system in the Global South.

Efficacy of silver nanoparticles to control flavobacteriosis caused by Flavobacterium johnsoniae in common carp Cyprinus carpio

Flavobacterial infections are among the causes of fish losses in farms with the emergence of antibiotic-resistant isolates. Silver nanoparticles (AgNPs) are known for their potent antimicrobial activity against different types of bacteria. In this study, we evaluated the antibacterial properties of AgNPs (diameter: 23 nm) against Flavobacterium johnsoniae infection in common carp Cyprinus carpio. The assays included both in vitro and in vivo antibacterial tests in addition to evaluation of cell toxicity effects on the fish cell lines. The in vitro results revealed potent inhibitory effects of AgNPs on the growth of F. johnsoniae with a minimum inhibitory concentration of 34 µg ml-1. Fish cell (epithelioma papulosum cyprini and koi carp fin) viability was 95-100% after exposure to 500 ng ml-1 (and lower concentrations) of AgNPs. In the exposure experiment, mortality rates decreased from 45% in the infected non-treated group to 30 and 15% in the intraperitoneal injection and immersion-treated groups, respectively. Neither of the treated groups showed any clinical signs or histopathological lesions. The single-dose treatment with AgNPs during early infection with F. johnsoniae aided in minimizing fish losses.

The toxicity of non-aged and aged coated silver nanoparticles to the freshwater shrimp Paratya australiensis

Nanoparticles (NPs) transform in the environment which result in alterations to their physicochemical properties. However, the effects of aging on the toxicity of NPs to aquatic organisms remain to be determined. Further the reports that have been published present contradictory results. The aim of this study was to examine the stability of differently coated silver nanoparticles (AgNPs) in media and the influence of aging of these NP on potential toxicity to freshwater shrimp Paratya australiensis. Coating-dependent changes in the stability of AgNP were observed with aging. Curcumin (C) coated AgNPs were stable, while tyrosine (T) coated AgNPs and epigallocatechin gallate (E) coated AgNPs aggregated in the P. australiensis medium. Increased lipid peroxidation and catalase activity was noted in P. australiensis exposed to AgNPs, suggesting oxidative stress was associated with NP exposure. The enhanced oxidative stress initiated by aged C-AgNPs suggests that aging of these NPs produced different toxicological responses. In summary, data suggest that coating-dependent alterations in NPs, together with aging affect both persistence and subsequent toxicity of NPs to freshwater organisms. Thus, the coating-dependent fate and toxicity of AgNPs together with the effect of their aging need to be considered in assessing the environmental risk of AgNPs to aquatic organisms.

Safety assessment of antibiotic administration by magnetic nanoparticles in in vitro zebrafish liver and intestine cultures

Different in vitro models have been suggested to replace in vivo studies. In vitro studies are of great interest and give the opportunity to analyze cellular responses in a closed system with stable experimental conditions and to avoid direct animal exposure and distress during the experiments. These methods are useful to test drugs and chemicals toxicity in order to better understand their environmental impact. In the present study, fish organ cultures have been used to test different oxytetracycline exposure methods, including oxide nanoparticles (IONPs), using zebrafish as experimental model. Results showed that oxytetracycline accumulation at the end of the experiment (24 h) in the exposed organs did not show any significant difference in the analyzed samples and was not dependent on the exposure way (free or IONPs-bound oxytetracycline). However, as regards molecular analysis, the different exposure ways tested in this study showed some differences in the expression of genes involved in stress response. The present data did not completely agree with a previous in vivo study performed in zebrafish using IONPs, underlying that replacement of in vivo models with in vitro studies cannot always represent the complexity of interactions typical of a biological system.

Adverse effects of nanosilver on human health and the environment

Silver and silver nanoparticles (AgNPs) exhibit antimicrobial properties against some bacteria, fungi and viruses, however, the ever-increasing application of nanosilver in consumer products, water disinfection and healthcare settings, have raised concerns over the public health/environmental safety of this nanomaterial. The current ubiquity of nanosilver may result in repeated exposure through various routes (skin, inhalation, or ingestion) which may lead to health complications. While there are a number of review articles and case studies published to date on the subject, an updated coherent review that clearly delineates thresholds and safe doses is lacking. Thus, it is plausible to have an overview of the most recent findings on the threshold limits, safe doses of silver and its related nanoscale forms, and the needed actions to ensure the safety and health of human, terrestrial and aquatic lives. This review provides an account of the effects of nanosilver in our daily lives. STATEMENT OF SIGNIFICANCE: This manuscripts is a review of the toxicity of nanosized silver. With respect to the existing literature, it goes beyond stating that there is a knowledge gap, drawing the attention of a wider readership to the ever-growing evidence of nanosilver toxicity to human and nature, and outlining the dose thresholds based on comprehensive data mining and visualisation. There are nearly 500 consumer products that claim to contain nanosilver. Thus, we trust a review of recent conclusive findings is timely. This manuscript is in line with the scope of the Journal, enabling a better understanding of the biological response to a widely-used bionanomaterial. Moreover, it provides a bigger picture of the link between surface properties and biocompatibility of nanosilver in different forms.

Antimicrobial and photophysical properties of chemically grafted ultra-high-molecular-weight polyethylene

Surface of ultra-high-molecular-weight polyethylene (UHMWPE) was modified by chemical methods. Surface was firstly activated by Piranha solution and then grafted with selected amino-compounds (cysteamine, ethylenediamine or chitosan). The next step was grafting of some borane cluster compounds, highly fluorescent borane hydride cluster anti-B₁₈H₂₂ or its thiolated derivative 4,4'-(HS)₂-anti-B₁₈H₂₀. Polymer foils were studied using various methods to characterize surface chemistry (X-ray photoelectron spectroscopy), roughness and morphology (atomic force microscopy, scanning electron microscopy), chemistry and polarity (electrokinetic analysis), wettability (goniometry) and photophysical properties (UV-Vis spectroscopy) before and after modification steps. Subsequently some kinds of antimicrobial tests were performed. Immobilization of anti-B₁₈H₂₂ in small quantities onto UHMWPE surface leads to materials with a luminescence. Samples grafted with borane clusters showed significant inhibition of growth for gram-positive bacteria (S. epidermidis). These approaches can be used for (i) luminophores on the base of polymers nanocomposites development and/or (ii) preparation of materials with antimicrobial effects.

Synthesis of biogenic silver nanoparticles using Althaea officinalis as reducing agent: evaluation of toxicity and ecotoxicity

Silver nanoparticles (AgNPs) are known mainly because of their bactericidal properties. Among the different types of synthesis, there is the biogenic synthesis, which allows the synergy between the nanocomposites and substances from the organism employed for the synthesis. This study describes the synthesis of AgNPs using infusion of roots (AgNpR) and extract (AgNpE) of the plant Althaea officinalis. After the synthesis through reduction of silver nitrate with compounds of A. officinalis, physico-chemical analyzes were performed by UV-Vis spectroscopy, nanoparticles tracking analysis (NTA), dynamic light scattering (DLS) and scanning electron microscopy (SEM). Toxicity was evaluated through Allium cepa assay, comet test with cell lines, cell viability by mitochondrial activity and image cytometry and minimal inhibitory concentration on pathogenic microorganisms. Biochemical analyzes (CAT - catalase, GPx - glutathione peroxidase e GST - glutationa S-transferase) and genotoxicity evaluation in vivo on Zebrafish were also performed. AgNpE and AgNpR showed size of 157 ± 11 nm and 293 ± 12 nm, polydispersity of 0.47 ± 0.08 and 0.25 ± 0.01, and zeta potential of 20.4 ± 1.4 and 26.5 ± 1.2 mV, respectively. With regard to toxicity, the AgNpE were the most toxic when compared with AgNpR. Biochemical analyzes on fish showed increase of CAT activity in most of the organs, whereas GPx showed few changes and the activity of GST decreased. Also regarding to bactericidal activity, both nanoparticles were effective, however AgNpR showed greater activity. Althaea officinalis can be employed as reducing agent for the synthesis of silver nanoparticles, although it is necessary to consider its potential toxicity and ecotoxicity.