Citrate-coated AgNPs Research Articles

Simultaneous determination of the size and concentration of AgNPs in water samples by UV–vis spectrophotometry and chemometrics tools

The combination of UV–vis spectrophotometry with a chemometric calibration tool based on partial least squares (PLS) has allowed us the development of a multivariate analytical method that simultaneously estimates the concentration and size of mixtures of silver nanoparticles (AgNPs) in environmental water samples. The method is based on changes in the surface plasmon resonance band (SPRB) of AgNPs when they form aggregated/assembled structures with L-cysteine (L-cys). Measurementts were performed by employed a fixed-time kinetics method that implies that the final spectra (response) are obtained by subtstracting the solutions spectra at fixed times. Optimization of experimental conditions affecting aggregation such as time, temperature, pH and concentration of aggregating substance was performed by experimental design and response surface methodologies (RSM). A multivariate calibration model using AgNPs of known diameter size ((20 ± 3), (41 ± 3), (59 ± 5) and (79 ± 7) nm) within a concentration range between 0.62 and 2.5 mg L−1 was constructed by using a mixture experimental design and PLS. The method was finally applied to estimate size and concentration of AgNPs in AgNPs-spiked river and tap water samples. Water samples were spiked with individual, binary and ternary mixtures of AgNPs of different sizes and by using two types of AgNPs: citrate-coated AgNPs (cit-AgNPs) and polyvinylpyrrolidone-coated AgNPs (PVP-AgNPs). A good correspondence was obtained between predicted values and the total amount of AgNPs added with recovery values ranged within 80–160% for the individual mixtures, 68–108% for the binary mixtures and 60–64% for the ternary mixtures of AgNPs. Finally, transmission electron microscopy (TEM) measurements were performed for those cases where discrepancies between the expected and the obtained values were observed. TEM micrographs evidenced the presence of agglomerates or aggregates of AgNPs in some of the mixtures or water tested.

NMR Metabolomics Reveals Metabolism-Mediated Protective Effects in Liver (HepG2) Cells Exposed to Subtoxic Levels of Silver Nanoparticles.

The expansion of biomedical and therapeutic applications of silver nanoparticles (AgNPs) raises the need to further understand their biological effects on human cells. In this work, NMR metabolomics has been applied to reveal the metabolic effects of AgNPs toward human hepatoma (HepG2) cells, which are relevant with respect to nanoparticle accumulation and detoxification. Cellular responses to widely disseminated citrate-coated AgNPs (Cit30) and to emergent biogenic AgNPs prepared using an aqueous plant extract as reducing and stabilizing agent (GS30) have been compared with a view to assess the influence of nanoparticle coating on the metabolic effects produced. Subtoxic concentrations (IC5 and IC20) of both nanoparticle types caused profound changes in the cellular metabolome, suggesting adaptations in energy production processes (glucose metabolism and the phosphocreatine system), antioxidant defenses, protein degradation and lipid metabolism. These signatures were proposed to reflect mainly metabolism-mediated protective mechanisms and were found to be largely common to Cit30 and GS30 AgNPs, although differences in the magnitude of response, not captured by conventional cytotoxicity assessment, were detected. Overall, this study highlights the value of NMR metabolomics for revealing subtoxic biological effects and helping to understand cell-nanomaterial interactions.

Silver nanoparticles induce neurotoxicity in a human embryonic stem cell-derived neuron and astrocyte network

Silver nanoparticles (AgNPs) are among the most extensively used nanoparticles and are found in a variety of products. This ubiquity leads to inevitable exposure to these particles in everyday life. However, the effects of AgNPs on neuron and astrocyte networks are still largely unknown. In this study, we used neurons and astrocytes derived from human embryonic stem cells as a cellular model to study the neurotoxicity that is induced by citrate-coated AgNPs (AgSCs). Immunostaining with the astrocyte and neuron markers, glial fibrillary acidic protein and microtubule-associated protein-2 (MAP2), respectively, showed that exposure to AgSCs at the concentration of 0.1 µg/mL increased the astrocyte/neuron ratio. In contrast, a higher concentration of AgSCs (5.0 µg/ml) significantly changed the morphology of astrocytes. These results suggest that astrocytes are sensitive to AgSC exposure and that low concentrations of AgSCs promote astrogenesis. Furthermore, our results showed that AgSCs reduced neurite outgrowth, decreased the expression of postsynaptic density protein 95 and synaptophysin, and induced neurodegeneration in a concentration-dependent manner. Our findings additionally suggest that the expression and phosphorylation status of MAP2 isoforms, as modulated by the activation of the Akt/glycogen synthase kinase-3/caspase-3 signaling pathway, may play an important role in AgSC-mediated neurotoxicity. We also found that AgNO3 exposure only slightly reduced neurite outgrowth and had little effect on MAP2 expression, suggesting that AgSCs and AgNO3 have different neuronal toxicity mechanisms. In addition, most of these effects were reduced when the cell culture was co-treated with AgSCs and the antioxidant ascorbic acid, which implies that oxidative stress is the major cause of AgSC-mediated astrocytic/neuronal toxicity and that antioxidants may have a neuroprotective effect.

Measurement of engineered nanoparticles in consumer products by surface-enhanced Raman spectroscopy and neutron activation analysis

There has been an increasing number of consumer and food products sold on the market that contain various engineered nanomaterials (ENMs) such as silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs). These nanomaterials possess novel physical and chemical properties that can be used for wide applications in agriculture and food safety. However, current analytical methods to detect and measure ENMs are time-consuming, labor-intensive, and expensive. The objective of this study was to develop a novel, simple, rapid, and accurate method to detect AgNPs and AuNPs in consumer products using surface-enhanced Raman spectroscopy (SERS). SERS measurement was conducted to detect AgNPs and AuNPs using an effective Raman indicator, 4-aminothiophenol (pATP). The pATP can strongly bind onto nanoparticles, generating greatly enhanced Raman signals that can be used for measurement. The pATP was combined with Ag or Au stock solution, AgNO3, citrate-coated AgNPs, citrate-coated AuNPs, AuCl, AgNPs, AuNPs, and five commercial products to study the differences in their SERS spectral data. The observed spectra of AgNPs and AuNPs have similar peaks at ~ 390, ~ 1087, and ~ 1590 cm−1 that can be attributed to the C–S stretching vibration, C–C stretching vibration, and C–H stretching vibration, respectively. Neutron activation analysis (NAA) and electron microscopy was used to characterize and quantify AgNPs and AuNPs in the consumer products. The results demonstrate that SERS method in combination with NAA can be an effective method for detection of ENMs, and it can easily distinguish AgNPs and AuNPs from other non-nanoparticle species in the complex matrices.

Distinct toxicity of silver nanoparticles and silver nitrate to Daphnia magna in M4 medium and surface water

Toxicity of silver nanoparticles (AgNPs) has been studied in various culture media. However, these media notably differ from the natural aquatic system, thus the conclusions may be inapplicable for real environment condition. The toxicity and its underlying mechanism of AgNPs in surface waters warrant more investigations. This study investigated the acute toxicity, chronic toxicity, bioaccumulation, and alga-daphnia food chain transfer of citrate-coated AgNPs (C-AgNPs) and Ag+ (from AgNO3) to D. magna in a culture medium (M4) and a surface water sample. Results show that the acute toxicity in the surface water was significantly lower than that in the M4 medium and the toxicity of Ag+ was greatly higher than that of C-AgNPs. The 48h median effect concentration (EC50) of C-AgNPs to D. magna in the M4 medium and the surface water was 110±9.3μg/L and 270±26μg/L, respectively, while that of Ag+ was 1.8±0.7μg/L and 8.0±0.6μg/L, respectively. The released Ag+ contributed to but not dominated the acute toxicity of C-AgNPs. At the EC50 of C-AgNPs, the contribution of released Ag+ was 35.7% and 28.0% to the apparent nanotoxicity in the M4 medium and the surface water sample, respectively. The chronic toxicity of C-AgNPs and Ag+ was also lower in the surface water sample than in the M4 medium as indicated by the significantly higher survival of daphnia in the surface water during the 21d exposure. The daphnia took up less but depurated more Ag in the surface water than in the M4 medium, which could account for the lower toxicity in the surface water. Biological magnification of Ag through the alga-daphnia food chain was not observed. These findings will be helpful for assessing the environmental risk of AgNPs and understanding the mechanism of nanotoxcity.

Toxic Effects and Molecular Mechanism of Different Types of Silver Nanoparticles to the Aquatic Crustacean Daphnia magna

Silver nanoparticles (AgNPs) have been assessed to have a high exposure risk for humans and aquatic organisms. Toxicity varies considerably between different types of AgNPs. This study aimed to investigate the toxic effects of AgNPs with different particle sizes (40 and 110 nm) and different surface coatings (sodium citrate and polyvinylpyrrolidone, PVP) on Daphnia magna and their mechanisms of action. The results revealed that the citrate-coated AgNPs were more toxic than PVP-coated AgNPs and that the 40 nm AgNPs were more toxic than the 110 nm AgNPs. Transcriptome analysis further revealed that the toxic effects of AgNPs on D. magna were related to the mechanisms of ion binding and several metabolic pathways, such as the "RNA polymerase" pathway and the "protein digestion and absorption" pathway. Moreover, the principal component analysis (PAC) results found that surface coating was the major factor that determines the toxicities compared to particle size. These results could help us better understand the possible mechanism of AgNP toxicity in aquatic invertebrates at the transcriptome level and establish an important foundation for revealing the broad impacts of nanoparticles on aquatic environments.

Differential effects of silver nanoparticles on DNA damage and DNA repair gene expression in Ogg1-deficient and wild type mice

Due to extensive use in consumer goods, it is important to understand the genotoxicity of silver nanoparticles (AgNPs) and identify susceptible populations. 8-Oxoguanine DNA glycosylase 1 (OGG1) excises 8-oxo-7,8-dihydro-2-deoxyguanine (8-oxoG), a pro-mutagenic lesion induced by oxidative stress. To understand whether defects in OGG1 is a possible genetic factor increasing an individual’s susceptibly to AgNPs, we determined DNA damage, genome rearrangements, and expression of DNA repair genes in Ogg1-deficient and wild type mice exposed orally to 4 mg/kg of citrate-coated AgNPs over a period of 7 d. DNA damage was examined at 3 and 7 d of exposure and 7 and 14 d post-exposure. AgNPs induced 8-oxoG, double strand breaks (DSBs), chromosomal damage, and DNA deletions in both genotypes. However, 8-oxoG was induced earlier in Ogg1-deficient mice and 8-oxoG levels were higher after 7-d treatment and persisted longer after exposure termination. AgNPs downregulated DNA glycosylases Ogg1, Neil1, and Neil2 in wild type mice, but upregulated Myh, Neil1, and Neil2 glycosylases in Ogg1-deficient mice. Neil1 and Neil2 can repair 8-oxoG. Thus, AgNP-mediated downregulation of DNA glycosylases in wild type mice may contribute to genotoxicity, while upregulation thereof in Ogg1-deficient mice could serve as an adaptive response to AgNP-induced DNA damage. However, our data show that Ogg1 is indispensable for the efficient repair of AgNP-induced damage. In summary, citrate-coated AgNPs are genotoxic in both genotypes and Ogg1 deficiency exacerbates the effect. These data suggest that humans with genetic polymorphisms and mutations in OGG1 may have increased susceptibility to AgNP-mediated DNA damage.

Genetic determinants of susceptibility to silver nanoparticle-induced acute lung inflammation in mice.

Silver nanoparticles (AgNPs) are employed in a variety of consumer products; however, in vivo rodent studies indicate that AgNPs can cause lung inflammation and toxicity in a strain- and particle type-dependent manner, but mechanisms of susceptibility remain unclear. The aim of this study was to assess the variation in AgNP-induced lung inflammation and toxicity across multiple inbred mouse strains and to use genome-wide association (GWA) mapping to identify potential candidate susceptibility genes. Mice received doses of 0.25 mg/kg of either 20-nm citrate-coated AgNPs or citrate buffer using oropharyngeal aspiration. Neutrophils in bronchoalveolar lavage fluid (BALF) served as markers of inflammation. We found significant strain- and treatment-dependent variation in neutrophils in BALF. GWA mapping identified 10 significant single-nucleotide polymorphisms (false discovery rate, 15%) in 4 quantitative trait loci on mouse chromosomes 1, 4, 15, and 18, and Nedd4l (neural precursor cell expressed developmentally downregulated gene 4-like; chromosome 18), Ano6 (anocatmin 6; chromosome 15), and Rnf220 (Ring finger protein 220; chromosome 4) were considered candidate genes. Quantitative RT-PCR revealed significant inverse associations between mRNA levels of these genes and neutrophil influx. Nedd4l, Ano6, and Rnf220 are candidate susceptibility genes for AgNP-induced lung inflammation that warrant additional exploration in future studies.-Scoville, D. K., Botta, D., Galdanes, K., Schmuck, S. C., White, C. C., Stapleton, P. L., Bammler, T. K., MacDonald, J. W., Altemeier, W. A., Hernandez, M., Kleeberger, S. R., Chen, L.-C., Gordon, T., Kavanagh, T. J. Genetic determinants of susceptibility to silver nanoparticle-induced acute lung inflammation in mice.

Citrate-Coated Silver Nanoparticles Growth-Independently Inhibit Aflatoxin Synthesis in Aspergillus parasiticus

Manufactured silver nanoparticles (Ag NPs) have long been used as antimicrobials. However, little is known about how these NPs affect fungal cell functions. While multiple previous studies reveal that Ag NPs inhibit secondary metabolite syntheses in several mycotoxin producing filamentous fungi, these effects are associated with growth repression and hence need sublethal to lethal NP doses, which besides stopping fungal growth, can potentially accumulate in the environment. Here we demonstrate that citrate-coated Ag NPs of size 20 nm, when applied at a selected nonlethal dose, can result in a >2 fold inhibition of biosynthesis of the carcinogenic mycotoxin and secondary metabolite, aflatoxin B1 in the filamentous fungus and an important plant pathogen, Aspergillus parasiticus, without inhibiting fungal growth. We also show that the observed inhibition was not due to Ag ions, but was specifically associated with the mycelial uptake of Ag NPs. The NP exposure resulted in a significant decrease in transcript levels of five aflatoxin genes and at least two key global regulators of secondary metabolism, laeA and veA, with a concomitant reduction of total reactive oxygen species (ROS). Finally, the depletion of Ag NPs in the growth medium allowed the fungus to regain completely its ability of aflatoxin biosynthesis. Our results therefore demonstrate the feasibility of Ag NPs to inhibit fungal secondary metabolism at nonlethal concentrations, hence providing a novel starting point for discovery of custom designed engineered nanoparticles that can efficiently prevent mycotoxins with minimal risk to health and environment.

Surface ligand controls silver ion release of nanosilver and its antibacterial activity against <em>Escherichia coli</em>

Understanding the mechanism of nanosilver-dependent antibacterial activity against microorganisms helps optimize the design and usage of the related nanomaterials. In this study, we prepared four kinds of 10 nm-sized silver nanoparticles (AgNPs) with dictated surface chemistry by capping different ligands, including citrate, mercaptopropionic acid, mercaptohexanoic acid, and mercaptopropionic sulfonic acid. Their surface-dependent chemistry and antibacterial activities were investigated. Owing to the weak bond to surface Ag, short carbon chain, and low silver ion attraction, citrate-coated AgNPs caused the highest silver ion release and the strongest antibacterial activity against Escherichia coli, when compared to the other tested AgNPs. The study on the underlying antibacterial mechanisms indicated that cellular membrane uptake of Ag, NAD+/NADH ratio increase, and intracellular reactive oxygen species (ROS) generation were significantly induced in both AgNP and silver ion exposure groups. The released silver ions from AgNPs inside cells through a Trojan-horse-type mechanism were suggested to interact with respiratory chain proteins on the membrane, interrupt intracellular O2 reduction, and induce ROS production. The further oxidative damages of lipid peroxidation and membrane breakdown caused the lethal effect on E. coli. Altogether, this study demonstrated that AgNPs exerted antibacterial activity through the release of silver ions and the subsequent induction of intracellular ROS generation by interacting with the cell membrane. The findings are helpful in guiding the controllable synthesis through the regulation of surface coating for medical care purpose.

Teratogenic hazard of BPEI-coated silver nanoparticles to Xenopus laevis

Silver nanoparticles (AgNPs) are among the most exploited antimicrobial agents and are used in many consumer products. Size and surface reactivity are critical physico-chemical properties responsible for NPs toxicity, and surface coatings, often used to functionalize or stabilize AgNPs, can influence their toxic profile and biocompatibility. In the current study the developmental toxicity of (1) negatively charged citrate-coated AgNPs (Cit-AgNPs), (2) positively charged branched polyethylenimine-coated AgNPs (BPEI-AgNPs), and (3) Ag+ (from 0.0625 to 0.75 mg Ag/L) was investigated by the standard Frog Embryo Teratogenesis Assay – Xenopus (FETAX). In order to identify the most sensitive developmental phase, embryos were also exposed during different embryonic stages. Morphological and bio-physical studies were performed to characterize tissue lesions and NP uptake. The results suggest that Ag+ was strongly embryo-lethal. Contrary to Cit-AgNPs, the positively charged BPEI-AgNPs exert a concentration-dependent effect on lethality and malformations of embryos. The BPEI-AgNPs showed the highest teratogenic index (TI = 1.6), pointing out the role of functional coating in determining the developmental hazard. The highest susceptibility to BPEI-AgNPs was during early embryogenesis, when embryos are still enclosed in the fertilization envelope, and the post-stomodeum opening stages, when NPs ingestion occurs. In BPEI-AgNPs treated larvae, the histological examination revealed irregular intestinal diverticula coupled with edematous connective tissue. Small NPs aggregates are mapped throughout the intestinal mucosa and secondary target organs by two-photon excitation microscopy. We conclude that a teratogenic risk may be associated with BPEI-AgNPs exposure, but the modality of NP-tissue interactions and the teratogenic mechanism need further investigations to be better defined.

Nematode-based biomarkers as critical risk indicators on assessing the impact of silver nanoparticles on soil ecosystems

Soil contamination caused by silver nanoparticles (AgNPs) released from sewage treatment plants (STPs) is of great public concern. Understanding the relationships between the physicochemical properties of AgNPs and their toxicity is critical for environmental and health risk analysis. Here we presented an approach for rapidly screening and assessing the potential toxicity risk of AgNPs in general and sludge-treated soils based on the nematode Caenhorhabditis elegans-based probabilistic risk assessment framework. The soil environmental risks were estimated depending on the characteristics of AgNPs and geographic regions. We assessed the risk for soils exceeding a threshold of C. elegans neurotoxicity based on the statistical models. Our results indicated that locomotion inhibition of C. elegans was depending on surface properties, diameter, and exposure time of AgNPs. Here we showed that the overall sewage sludge-released AgNPs-associated soil contamination risk was very low among Europe, U.S., and Switzerland. However, large production and widespread use of AgNPs are highly likely to pose long-term ecotoxicity risk on general and sludge-treated soils, particularly for 26nm citrate-coated AgNPs. Our approach of integrating probabilistic risk model and C. elegans-based ecological indicator provides an effective tool to rapidly screen and assess the impacts of STPs-released AgNPs on soil environment. We suggest that C. elegans as a proxy for estimating soil risk metrics can help develop methods of management for mitigating the metal NPs-induced toxicity on terrestrial ecosystems.

Particle coatings but not silver ions mediate genotoxicity of ingested silver nanoparticles in a mouse model

Incorporation of silver nanoparticles (AgNPs) in toothpaste, food containers, dietary supplements and other consumer products can result in oral exposure to AgNPs and/or silver ions (Ag+) released from the surface of AgNPs. To examine whether ingestion of AgNPs or Ag+ results in genotoxic damage and whether AgNP coatings modulate the effect, we exposed mice orally to 20nm citrate-coated AgNPs, polyvinylpyrrolidone (PVP)-coated AgNPs, silver acetate or respective vehicles at a 4mg/kg dose (equivalent to 800× the EPA reference dose for Ag) for 7days. Genotoxicity was examined in the systemic circulation and bone marrow at 1, 7, and 14days post-exposure. We found that citrate-coated AgNPs induced chromosomal damage in bone marrow and oxidative DNA damage and double strand breaks in peripheral blood. These damages persisted for at least 14days after exposure termination. Because oxidative DNA damage and strand breaks are repaired rapidly, their presence after exposure cessation indicates that citrate-coated AgNPs persist in the body. In contrast, PVP-coated AgNPs and silver acetate did not induce DNA or chromosomal damage at any time point measured. To determine whether coating-dependent genotoxicity is related to different AgNP changes in the gastrointestinal tract, we examined AgNP behavior and fate in an in vitro gastrointestinal digestion model using UV–visible spectroscopy and DLS. Citrate-coated AgNPs were more susceptible to agglomeration than PVP-coated AgNPs in digestive juices with or without proteins. In summary, AgNPs but not Ag+ are genotoxic following oral ingestion. Nanoparticle coatings modulate gastrointestinal transformation and genotoxicity of AgNPs, where higher agglomeration of AgNPs in gastrointestinal juices is associated with higher genotoxicity in tissues. Since genotoxicity is a strong indicator of cancer risk, further long-term studies focusing on cancer are warranted.

Unraveling the Complex Behavior of AgNPs Driving NP-Cell Interactions and Toxicity to Algal Cells.

While the importance of nanoparticle (NP) characterization under relevant test conditions is widely recognized in nanotoxicology, few studies monitor NPs behavior in the presence of exposed organisms. Here we studied the behavior of nine types of silver nanoparticles (AgNPs) during the 48 h algal toxicity test. In particular, we investigated NP aggregation and dissolution by time-resolved inductively coupled plasma mass spectrometry and ultrafiltration and performed mass balance measurements to study the distribution of Ag in the test system. We also determined the amount of extra- and intracellular Ag by chemically etching AgNPs on the surface of algal cells and used dark field microscopy for their imaging. We observed that positively charged branched polyethilenimine (bPEI)-coated AgNPs tend to aggregate in the presence of algae and interact with test vessels and algal cells, while citrate-coated AgNPs have a tendency to dissolve. On the other hand, with large variation of half-maximum effective concentration (EC50) across tested NPs (5.4 to 300 ngAg mL-1), Ag internalized by the algal cells at EC50 was similar (0.8 to 3.6 ngAg mL-1) for all AgNP types. These data show that while sorption to the vessels, dissolution, and aggregation impact on the distribution of AgNPs in the test system and on interactions with algal cells, AgNP toxicity is strongly correlated with the NP-cell surface interaction and internalization of Ag.

Differential antimicrobial activity of silver nanoparticles to bacteria Bacillus subtilis and Escherichia coli, and toxicity to crop plant Zea mays and beneficial B. subtilis-inoculated Z. mays

As silver nanoparticles (AgNPs) have become increasingly used in commercial antimicrobial agents and industrial and military products, concerns are increasing over their broad environmental and health impacts and risks because they are finding their way to the environment. This study was designed to quantify the antimicrobial activity of citrate-coated AgNPs (c-AgNPs; transmission electron microscope size of 44.9 ± 7.2 nm) to two species of bacteria, i.e., Gram-positive Bacillus subtilis and Gram-negative Escherichia coli, and toxicity to a major crop plant Zea mays and beneficial bacteria-inoculated plant (i.e., B. subtilis-inoculated Z. mays symbiont). Our results reveal that the exposure of c-AgNPs significantly inhibited bacteria growth and altered their growth kinetics. Z. mays experienced significant sublethal effects including reduced root length and biomass, and hyper-accumulation of Ag in roots. The beneficial interactions between B. subtilis and Z. mays were weakened as well because both species suffered sublethal effects. Potential mechanisms leading to the antimicrobial activity and toxicity of c-AgNPs to the bacteria, plant, and plant–bacteria symbiont examined in this study were discussed. Taken together, our findings advance the current knowledge of AgNPs antimicrobial property or toxicity to bacteria, crop plant, and beneficial plant–bacteria symbiotic interaction, which is a critical component for NPs environmental impact and risk assessment.

Silver nanoparticles exhibit coating and dose-dependent neurotoxicity in glutamatergic neurons derived from human embryonic stem cells

Silver nanoparticles (AgNPs) are used extensively as anti-microbial agents in various products, but little is known about their potential neurotoxic effects. In this study, we used glutamatergic neurons derived from human embryonic stem cells as a cellular model to study 20nm citrate-coated AgNPs (AgSCs) and Polyvinylpyrrolidone-coated AgNPs (AgSPs) induced neurotoxicity. AgSCs significantly damaged neurite outgrowths; increased the production of reactive oxygen species and Ca2+ influxes; reduced the expression of MAP2, PSD95, vGlut1 and NMDA receptor proteins at concentrations as low as 0.1μg/ml. In contrast, AgSPs exhibited neurotoxicity only at higher concentration. Furthermore, our results showed that AgSCs induced glutamate excitotoxicity by the activation of calmodulin and the induction of nitric oxide synthase; increased the phosphorylation of glycogen synthase kinase-3 α/β at Tyr216 and Tau at Ser396 and reduced the expression of Tau46, which are typically observed in Alzheimer’s disease. This study indicated that stem cells can provide an excellent platform for studying nanoparticle induced neurotoxicity.

Behavior and chronic toxicity of two differently stabilized silver nanoparticles to Daphnia magna

While differences in silver nanoparticle (AgNP) colloidal stability, surface potential, or acute aquatic toxicity for differently stabilized AgNP have often been reported, these have rarely been studied in long-term ecotoxicity tests. In the current study, we investigated the chronic toxicity of AgNP to Daphnia magna over a 21-day period with two different stabilizers (citrate and detergent), representative for charge and sterical stabilizers, respectively. This was coupled with a series of short-term experiments, such as mass balance and uptake/depuration testing, to investigate the behavior of both types of AgNP during a typical media exchange period in the D. magna test for chronic toxicity. As expected, the sterically stabilized AgNP was more stable in the test medium, also in the presence of food; however, a higher uptake of silver after 24h exposure of the charge stabilized AgNP was found compared to the detergent-stabilized AgNP (0.046±0.006μgAgμgDW−1 and 0.023±0.005μgAgμgDW−1, respectively). In accordance with this, the higher reproductive effects and mortality were found for the charge-stabilized than for the sterically-stabilized silver nanoparticles in 21-d tests for chronic toxicity. LOEC was 19.2μgAgL−1 for both endpoints for citrate-coated AgNP and >27.5μgAgL−1 (highest tested concentration for detergent-stabilized AgNP). This indicates a link between uptake and toxicity. The inclusion of additional short-term experiments on uptake and depuration is recommended when longer-term chronic experiments with nanoparticles are conducted.

Phytotoxicity of Ag nanoparticles prepared by biogenic and chemical methods

Silver nanoparticles (Ag NPs) are now widely used as antibacterial and antifungal materials in different consumer products. We report here the preparation of Ag NPs by neem leaves extract (Azadirachta) reduction and trisodium citrate–sodium borohydride reduction methods, and study of their phytotoxicity. The nanoparticles were characterized by UV–Vis spectroscopy, FTIR, and atomic force microscopy (AFM) techniques. Both neem-coated and citrate-coated Ag NPs exhibit surface plasmon around 400 nm, and their average sizes measured by AFM are about 100 and 20 nm, respectively. Antibacterial and antifungal activities of these nanomaterials have been studied by simple pea seed germination and disk diffusion methods. It has been observed from the growth of root and shoot, citrate-coated Ag NPs significantly affect seedling growth, but neem-coated Ag NPs exhibit somehow mild toxicity toward germination process due to the nutrient supplements from neem. On the other hand, antifungal activity of neem-coated Ag NPs has been found much higher than that of citrate-coated Ag NPs due to the combined effects of antifungal activity of neem and Ag NPs. Present research primarily indicates a possible application of neem-coated Ag NPs as a potential fungicide.

Silver nanoparticles defeat p53-positive and p53-negative osteosarcoma cells by triggering mitochondrial stress and apoptosis.

Loss of function of the tumour suppressor p53 observed frequently in human cancers challenges the drug-induced apoptotic elimination of cancer cells from the body. This phenomenon is a major concern and provides much of the impetus for current attempts to develop a new generation of anticancer drugs capable of provoking apoptosis in a p53-independent manner. Since silver nanoparticles (AgNPs) possess unique cytotoxic features, we examined, whether their activity could be exploited to kill tumour suppressor-deficient cancer cells. Therefore, we investigated the effects of AgNPs on osteosarcoma cells of different p53 genetic backgrounds. As particle diameters might influence the molecular mechanisms leading to AgNP-induced cell death we applied 5 nm and 35 nm sized citrate-coated AgNPs. We found that both sized AgNPs targeted mitochondria and induced apoptosis in wild-type p53-containing U2Os and p53-deficient Saos-2 cells. According to our findings AgNPs are able to kill osteosarcoma cells independently from their actual p53 status and induce p53-independent cancer cell apoptosis. This feature renders AgNPs attractive candidates for novel chemotherapeutic approaches.

Organelles and chromatin fragmentation of human umbilical vein endothelial cell influence by the effects of zeta potential and size of silver nanoparticles in different manners

Recently, it has been disclosed that silver nanoparticles (AgNPs) have the potential to inhibit infection and cancerous cells and eventually penetrate through injected site into the capillary due to their small size. This study focuses on the effect of size and zeta potential of bare and citrate-coated AgNPs on human umbilical vein endothelial cells (HUVECs) as main capillary cells. AgNPs with high and low concentrations and no citrate coating were synthesized by using simple wet chemical method and named as AgNP/HC, AgNP/LC, and AgNP, respectively. Citrate coated particles showed larger zeta potential of −22 mV and AgNp/HC showed the smallest size of 13.2 nm. UV-Visible spectroscopy and dynamic light scattering (DLS) were performed to evaluate particle size and hydrodynamic diameter of NPs in water and cell culture media. Results indicated that higher concentrations of citrate decreased hydrodynamic diameter and NP agglomeration. reactive oxygen species (ROS) production of all AgNPs was similar at 28 ppm although it was significantly higher than control group. Their effects on cell membrane and chromosomal structure were studied using LDH measurement and 4′,6-diamidino-2-phenylindole (DAPI) staining, as well. Results demonstrated that AgNP/LC was less toxic to cells owing to higher value of IC50, minimum inhibitory concentration (MIC), and less release of LDH. Cancerous (Human Caucasian neuroblastoma) and immortal cells (Mouse embryonic fibroblast cell line) were about twice more sensitive than HUVECs to toxic effects of AgNPs. DAPI staining results showed that AgNP and AgNP/HC induced highest and lowest breaking of chromosome. Overall results suggest that viability of HUVECs will be higher than 90% when viability of cancerous cells is 50% in AgNPs chemotherapy.