Comparative in vivo toxicokinetics of silver powder, nanosilver and soluble silver compounds after oral administration to rats.

Silver (Ag; massive, powder and nanoform) and Ag compounds are used in industrial, medical and consumer applications, with potential for human exposure. Uncertainties exist about their comparative mammalian toxicokinetic ('TK') profiles, including their relative oral route bioavailability, especially for Ag massive and powder forms. This knowledge gap impedes concluding on the grouping of Ag and Ag compounds for hazard assessment purposes. Therefore, an in vivo TK study was performed in a rat model. Sprague-Dawley rats were exposed via oral gavage for up to 28 days to silver acetate (AgAc; 5, 55, 175 mg/kg(bw)/d), silver nitrate (AgNO3; 5, 55, 125 mg/kg(bw)/d), nanosilver (AgNP; 15 nm diameter; 3.6, 36, 360 mg/kg(bw)/d) or silver powder (AgMP; 0.35 µm diameter; 36, 180, 1000 mg/kg(bw)/d). Total Ag concentrations were determined in blood and tissues to provide data on comparative systemic exposure to Ag and differentials in achieved tissue Ag levels. AgAc and AgNO3 were the most bioavailable forms with comparable and linear TK profiles (achieved systemic exposures and tissue concentrations). AgMP administration led to systemic exposures of about an order of magnitude less, with tissue Ag concentrations 2-3 orders of magnitude lower and demonstrating non-linear kinetics. The apparent oral bioavailability of AgNP was intermediate between AgAc/AgNO3 and AgMP. For all test items, highest tissue Ag concentrations were in the gastrointestinal tract and reticuloendothelial organs, whereas brain and testis were minor sites of distribution. It was concluded that the oral bioavailability of AgMP was very limited. These findings provide hazard assessment context for various Ag test items and support the prediction that Ag in massive and powder forms exhibit low toxicity potential.

Brucella species-induced brucellosis: Antimicrobial effects, potential resistance and toxicity of silver and gold nanosized particles.

Brucellosis is an endemic zoonotic disease caused by Brucella species, which are intramacrophage pathogens that make treating this disease challenging. The negative effects of the treatment regime have prompted the development of new antimicrobials against brucellosis. A new treatment modality for antibiotic-resistant microorganisms is the use of nanoparticles (NPs). In this study, we examined the antibacterial activities of silver and gold NPs (SNPs and GNPs, respectively), the resistance developed by Brucella melitensis (B. melitensis) and Brucella abortus (B. abortus) strains and the toxicity of both of these NPs in experimental rats. To test the bactericidal effects of the SNPs and GNPs, we used 22 multidrug-resistant Brucella isolates (10 B. melitensis and 12 B. abortus). The minimal inhibitory concentrations (MICs) of both types of NPs were determined utilizing the microdilution technique. To test the stability of resistance, 7 B. melitensis and 6 B. abortus isolates were passaged ten times in culture with subinhibitory concentrations of NPs and another ten times without NPs. Histopathological analysis was completed after rats were given 0.25, 0.5, 1, and 2 mg/kg NPs orally for 28 consecutive days. The MIC values (µg/ml) of the 10-nm SNPs and 20-nm GNPs against B. melitensis were 22.43 ± 2.32 and 13.56 ± 1.22, while these values were 18.77 ± 1.33 and 12.45 ± 1.59 for B. abortus, respectively. After extensive in vitro exposure, most strains showed no resistance to the 10-nm SNPs or 20-nm GNPs. The NPs and antibiotics did not cross-react in any of the evolved Brucella strains. SNPs and GNPs at doses below 2 mg/kg were not harmful to rat tissue according to organ histopathological examinations. However, a greater dose of NPs (2 mg/kg) harmed all of the tissues studied. The bactericidal properties of NPs are demonstrated in this work. Brucella strains develop similar resistance to SNPs and GNPs, and at low dosages, neither SNPs nor GNPs were hazardous to rats.

Sustainable phyto-fabrication of silver nanoparticles using Gmelina arborea exhibit antimicrobial and biofilm inhibition activity.

Increase in bacterial resistance to commonly used antibiotics is a major public health concern generating interest in novel antibacterial treatments. Aim of this scientific endeavor was to find an alternative efficient antibacterial agent from non-conventional plant source for human health applications. We used an eco-friendly approach for phyto-fabrication of silver nanoparticles (AgNPs) by utilizing logging residue from timber trees Gmelina arborea (GA). GC-MS analysis of leaves, barks, flowers, fruits, and roots was conducted to determine the bioactive compounds. Biosynthesis, morphological and structural characterization of GA-AgNPs were undertaken by UV-Vis spectroscopy, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometer (XRD). GA-AgNPs were evaluated for antibacterial, antibiofilm, antioxidant, wound healing properties and their toxicity studies were carried out. Results identified the presence of terpenoids, sterols, aliphatic alcohols, aldehydes, and flavonoids in leaves, making leaf extract the ideal choice for phyto-fabrication of silver nanoparticles. The synthesis of GA-AgNPs was confirmed by dark brown colored colloidal solution and spectral absorption peak at 420 nm. Spherical, uniformly dispersed, crystalline GA-AgNPs were 34-40 nm in diameter and stable in solutions at room temperature. Functional groups attributed to the presence of flavonoids, terpenoids, and phenols that acted as reducing and capping agents. Antibacterial potency was confirmed against pathogenic bacteria Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus by disc diffusion assay, MIC and MBC assay, biofilm inhibition assay, electron-microscopy, cell staining and colony counting techniques. The results from zone of inhibition, number of ruptured cells and dead-cell-count analysis confirmed that GA-AgNPs were more effective than GA-extract and their bacteria inhibition activity level increased further when loaded on hydrogel as GA-AgNPs-PF127, making it a novel distinguishing feature. Antioxidant activity was confirmed by the free radical scavenging assays (DPPH and ABTS). Wound healing potential was confirmed by cell scratch assay in human dermal fibroblast cell lines. Cell-proliferation study in human chang liver cell lines and optical microscopic observations confirmed non-toxicity of GA-AgNPs at low doses. Our study concluded that biosynthesized GA-AgNPs had enhanced antibacterial, antibiofilm, antioxidant, and wound healing properties.

Cytotoxicity Analysis of Human Dental Pulp Stem Cells After Silver Diamine Fluoride Application.

Purpose: The purpose of this study was to evaluate the cytotoxicity of silver diamine fluoride (SDF) to human dental pulp stem cells (hDPSC). Methods: hDPSC were exposed to dilutions of 38 percent SDF ( 10-3, 10-4, and 10-5) and incubated for 24 hours. Cell viability was assessed with colorimetric detection assay at 24 hours. Fresh media was used as a negative control, and 0.1% sodium dodecyl sulfate was used as a positive control. Three independent experiments were performed in triplicate. Cell viability data were analyzed using analysis of variance and Tukey's multiple comparison test. Results: Cells exposed to dilution of 38 percent SDF 10-3 had an average cell viability of 17.0±3.5 (standard deviation) percent. Cells exposed to SDF 10-4 and 10-5 had an average cell viability of 101±2.5 percent and 94±4.4 percent, respectively. Dilution of 10-3 had significantly lower cell viability than the negative control (P<0.001). Dilution of 10-4 and 10-5 SDF had significantly higher cell viability than the positive control (P<0.001) and cells treated with a dilution of 10-3 (P<0.001). Conclusions: Thirty-eight percent silver diamine fluoride was cytotoxic to human dental pulp stem cells at a dilution of 10-3, but not at 10-4 and 10-5. In light of the cytotoxicity of SDF to hDPSC, this in vitro study supports the concern that exposure of the full concentration of 38 percent SDF to the pulp should be avoided.

Genótipos e Fenótipos de Resistência a Metais Pesados e Agrotóxicos em Patógenos de Alto Risco em Saúde Única / Genotypes and Phenotypes of Resistance to Heavy Metals and Pesticides in High-Risk Pathogens in Single Health

As atividades industriais e de agronegócio, embora necessárias para o desenvolvimento da sociedade, tem causado sérios problemas ambientais devido à eliminação inadequada de seus efluentes, sendo o tratamento destes um dos assuntos mais importantes em relação ao controle de poluição. Os microrganismos podem ser utilizados como biomarcadores de contaminação, portanto, o conhecimento de mecanismos associados à resistência e a capacidade de imobilização e biotransformação de poluentes é um fator importante para a identificação de linhagens adaptadas, que podem ser eficientes no tratamento e na recuperação de áreas contaminadas. O objetivo do presente projeto foi avaliar o perfil de tolerância de patógenos bacterianos de alto risco em saúde única, aos metais pesados (mercúrio, prata, telúrio e arsênio) e ao agrotóxico glifosato; identificando o resistoma associado. A correlação fenótipo-genótipo foi avaliada em isolados de Klebsiella pneumoniae (n= 35), Escherichia coli (n=46), e Salmonella spp. (n=19), determinando a CIM pelo método de microdiluição, e analisando as respectivas sequências genômicas. Entre os isolados de K. pneumoniae, 32 cepas apresentaram CIM elevadas (64- 512µg/mL) para o metal prata, dos quais 20 carregam o operon silPABCRSE responsável por conferir resistência. Uma cepa de K. pneumoniae carregando genes terABCE apresentou uma CIM de 64 µg/mL para telúrio. Seis cepas de E. coli apresentaram uma CIM >32 µg/mL para telúrio, sendo que 3 cepas carregam os genes tehA/B. Outras 6 cepas de E. coli apresentaram CIM para prata de 256-512 µg/mL, mas só duas carregaram genes silPFCE. Duas cepas de Salmonella apresentaram CIM 64-128 µg/mL para telúrio, e carregam genes tehA/B e terABCDEF. Em relação ao arsênio, 24 cepas de E. coli apresentaram uma CIM ≥ 512 µg/mL, e destas, 12 cepas carregam os genes arsRBC. Salmonella spp., que carregam o gene merR apresentaram CIMs de 8-16 µg/mL para mercúrio. Não foi possível correlacionar a presença do operon phnC-P (sugerido como responsável pela tolerância ao glifosato) com CIMs elevadas para este composto. Os resultados obtidos suportam a hipóteses que a exposição de bactérias de origem humana, animal e ambiental, aos metais pesados pode estar contribuindo para a seleção de linhagens tolerantes, sendo que a tolerância à prata mediada pelo operon silPABCRSE em K. pneumoniae foi predominante no grupo clonal CG258, característica com potencial de biomarcador que pode ser utilizado para monitorar o impacto do uso deste metal nas diferentes atividades humanas. Neste trabalho foi possível padronizar a técnica de PCR com os genes do operon sil de interesse

Industrial and agribusiness activities have caused serious environmental problems due to the inadequate disposal of their effluents, the treatment of which being one of the most important issues in relation to pollution control. Microorganisms can be used as biomarkers of contamination, therefore the knowledge of mechanisms associated with resistance and the immobilization and biotransformation capacity of pollutants can be an important factor for the identification of adapted strains, efficient in the treatment and recovery of contaminated areas. The aim of this study was to evaluate the tolerance profile of critical priority bacterial pathogens relevant in One Health, to heavy metals (mercury, silver, tellurium, and arsenic) and to the pesticide glyphosate, identifying the associated resistome. The phenotype-genotype correlation was evaluated in antibiotic-resistant isolates of Klebsiella pneumoniae (n= 35), Escherichia coli (n= 46), and Salmonella spp. (n= 19), by MIC determination using the microdilution method, and by analysis of their respective genomic sequences. Among the isolates of K. pneumoniae, 32 strains showed elevated MIC (64-512 µg/mL) for silver metal, of which 20 carried the silPABCRSE operon responsible for conferring resistance. A strain of K. pneumoniae carrying terrace genes showed a MIC of 64 µg/mL for tellurium. Six strains of E. coli showed an MIC> 32 µg/mL for tellurium, with 3 strains carrying the Thea/B genes. Other 6 strainsof E. coli showed MIC for silver of 256-512 µg/mL, but only two carried silPFCE genes. Two strains of Salmonella showed MIC 64-128 µg/mL for tellurium and carried the/B and terABCDEF genes. In relation to arsenic, 24 strains of E. coli had a MIC 512 µg/mL, and of these, 12 strains carried the arsRBC genes. Salmonella spp., which carriedthe mer gene, had MICs of 8-16 µg/mL for mercury. It was not possible to correlate thepresence of the phonic-P operon (suggested as responsible for glyphosate tolerance) with elevated MICs for this compound. The silver tolerance mediated by the operon sil was a predominant feature in K. pneumoniae strains belonging to the clonal group CG258, suggesting a intrinsic property that has contributed to the persistence and wide dissemination of CG258 within a One Health context, which could be as a biomarkerto monitor the impact of the use of silver compounds and silver-based biomaterial on different human activities. In this work it was possible to standardize the PCR technique with the genes of the sil operon of interest

Disruption of pulmonary resolution mediators contribute to exacerbated silver nanoparticle-induced acute inflammation in a metabolic syndrome mouse model.

Pre-existing conditions modulate sensitivity to numerous xenobiotic exposures such as air pollution. Specifically, individuals suffering from metabolic syndrome (MetS) demonstrate enhanced acute inflammatory responses following particulate matter inhalation. The mechanisms associated with these exacerbated inflammatory responses are unknown, impairing interventional strategies and our understanding of susceptible populations. We hypothesize MetS-associated lipid dysregulation influences mediators of inflammatory resolution signaling contributing to increased acute pulmonary toxicity. To evaluate this hypothesis, healthy and MetS mouse models were treated with either 18-hydroxy eicosapentaenoic acid (18-HEPE), 14-hydroxy docosahexaenoic acid (14-HDHA), 17-hydroxy docosahexaenoic acid (17-HDHA), or saline (control) via intraperitoneal injection prior to oropharyngeal aspiration of silver nanoparticles (AgNP). In mice receiving saline treatment, AgNP exposure resulted in an acute pulmonary inflammatory response that was exacerbated in MetS mice. A targeted lipid assessment demonstrated 18-HEPE, 14-HDHA, and 17-HDHA treatments altered lung levels of specialized pro-resolving lipid mediators (SPMs). 14-HDHA and 17-HDHA treatments more efficiently reduced the exacerbated acute inflammatory response in AgNP exposed MetS mice as compared to 18-HEPE. This included decreased neutrophilic influx, diminished induction of inflammatory cytokines/chemokines, and reduced alterations in SPMs. Examination of SPM receptors determined baseline reductions in MetS mice compared to healthy as well as decreases due to AgNP exposure. Overall, these results demonstrate AgNP exposure disrupts inflammatory resolution, specifically 14-HDHA and 17-HDHA derived SPMs, in MetS contributing to exacerbated acute inflammatory responses. Our findings identify a potential mechanism responsible for enhanced susceptibility in MetS that can be targeted for interventional therapeutic approaches.

A systematic review of preclinical data regarding commercial silver-coated vascular grafts.

OBJECTIVE: Vascular graft infection (VGI) is a serious complication with high mortality and morbidity rates. Several measures could be taken to decrease this risk, including the use of silver-containing vascular grafts. However, to date, no clinical advantages have been reported. This study reviews the outcome of preclinical studies focusing on the role of commercially available silver-coated grafts in the prevention of VGI. METHODS: A systematic review was performed with a focus on the preclinical role of commercially available silver-coated vascular grafts in the prevention and treatment of VGI. A comprehensive search was conducted in Medline, Embase, and Web of Science. RESULTS: Nine in vitro and five in vivo studies were included. Two commercial grafts were used (INTERGARD SILVER and Silver Graft). In vitro studies used both gram-positive and gram-negative strains. A positive antimicrobial effect was observed in seven of nine studies (77.8%). A delayed antifungal effect against Candida species was observed in vitro, but disappeared when adding serum proteins. In vivo studies witnessed a microbicidal effect in two out of five studies (40%), but only tested a single causative pathogen (ie, Staphylococcus aureus). CONCLUSIONS: Both in vitro and in vivo studies demonstrated conflicting and mixed results concerning the antimicrobial efficacy of commercially available silver-containing grafts in the prevention of VGI. In general, the study setup was heterogeneous in the different articles. Given the lack of convincing preclinical evidence and their poor performance in clinical studies, more data are needed at this time to guide the appropriate use of silver grafts.

Systemic effects and impact on the gut microbiota upon subacute oral exposure to silver acetate in rats.

CONTEXT: The addition of silver (Ag) to food items, and its migration from food packaging and appliances results in a dietary exposure in humans, estimated to 70-90 µg Ag/day. In view of the well-known bactericidal activity of Ag ions, concerns arise about a possible impact of dietary Ag on the gut microbiota (GM), which is a master determinant of human health and diseases. Repeated oral administration of Ag acetate (AgAc) can also cause systemic toxicity in rats with reported NOAELs of 4 mg AgAc/b.w./d for impaired fertility and 0.4 mg AgAc/b.w./d for developmental toxicity. OBJECTIVE: The objective of this study was to investigate whether oral exposure to AgAc can induce GM alterations at doses causing reproductive toxicity in rats. METHODS: Male and female Wistar rats were exposed during 10 weeks to AgAc incorporated into food (0, 0.4, 4 or 40 mg/kg b.w./d), and we analyzed the composition of the GM (α- and ß-diversity). We documented bacterial function by measuring short-chain fatty acid (SCFA) production in cecal content. Ferroxidase activity, a biomarker of systemic Ag toxicity, was measured in serum. RESULTS AND CONCLUSIONS: From 4 mg/kg b.w./d onwards, we recorded systemic toxicity, as indicated by the reduction of serum ferroxidase activity, as well as serum Cu and Se concentrations. This systemic toxic response to AgAc might contribute to explain reprotoxic manifestations. We observed a dose-dependent modification of the GM composition in male rats exposed to AgAc. No impact of AgAc exposure on the production of bacterial SCFA was recorded. The limited GM changes recorded in this study do not appear related to a reprotoxicity outcome.

The toxic influence of silver and titanium dioxide nanoparticles on cultured ovarian granulosa cells.

The application of metal nanoparticles in modern society is growing, but there is insufficient data concerning their influence on reproductive processes and comparison of their biological activity. The present experiments aimed to compare the effects of silver and titanium dioxide nanoparticles (AgNPs and TiO2NPs) on ovarian granulosa cell functions. AgNPs and TiO2NPs were added to culture of porcine granulosa cells at doses 0, 0.01, 0.1, 1 or 10 µg/mL. The mRNAs for proliferating cell nuclear antigen (PCNA), cyclin B1, bax and caspase 3 were quantified by RT-PCR; release of progesterone was analyzed by ELISA. It was shown that both AgNPs and TiO2NPs significantly reduced all the measured parameters. ED50 of the inhibitory influence of AgNPs on the main ovarian cell parameters was higher than ED50 of TiO2NPs. The ability of AgNPs and TiO2NPs to suppress ovarian granulosa cell functions should be taken into account by their application.

Temporal Exposure of Dermal Fibroblasts to Silver Diamine Fluoride and Fluorine NMR Quantitation.

OBJECTIVE: Silver diamine fluoride has been advocated as a caries arresting material for Early Childhood Caries (ECC) and has received considerable public attention as the "silver bullet". However, cytotoxicity tests on the current concentrations of Silver Diamine Fluoride (SDF) to soft tissue have not been thoroughly assessed and analyzed at selected time intervals. The level of fluoride that is present within human cells has yet to be quantified. Preliminary SDF toxicity studies in our lab determined exposures of Dermal Fibroblasts to 0.03% SDF for 18 hours resulted in 100% cytotoxicity and complete monolayer loss. Endpoint titration of SDF determined that morphologic cytotoxic effects were ameliorated at input SDF levels lower than 0.002%. Because of the small culture sample volumes, we were unable to effectively assay fluoride concentrations using commercially available assays. In this study we attempted to assess fluoride levels in culture supernatants in a temporal fashion using quantitative Nuclear Magnetic Resonance (NMR). STUDY DESIGN: Dermal Fibroblast (DF) cells were grown in 24 well cluster plates fitted with 0.4 micron TranswellTM inserts to confluency in 0.9mL of DF culture media. Then the DF cells were challenged with 0.1 mL of SDF in sterile water in the Transwell chamber to achieve a final concentration of 0.03% SDF. Cultures were reincubated for 30 minutes, 1, 2, 4 and 8 hours. At the selected time points Transwell inserts were removed. SDF culture media was removed and replaced with fresh media and allowed to re-incubate up to 8 hours. Harvested SDF culture media was centrifuged at 15,000 x g to remove any resulting SDF precipitates and supernatants were harvested and stored at -70°C for fluoride assay. After 8 hours, media was aspirated from all wells and DF cells were fixed and then stained with methylene blue and assessed for cytotoxicity. Harvested supernatants were assessed for fluoride content. While SDF is soluble in pure water, it precipitates instantly in the presence of other media constituents and 0.85% saline. Transwells inserts capture the precipitate but allow soluble SDF and constituents pass through to the cell monolayer. NMR was used to assess SDF (fluoride) prepared in water, in DF media or in normal saline at the same concentrations used in the DF cell studies. The 19F NMR spectra were acquired at 25 °C on an Agilent DD2 500 MHz spectrometer equipped with a 5mm HFX z gradient probe operating at 470.3 MHz for fluorine. For quantitative measurements, all spectra were collected with 64 scans and a delay of 5 seconds. The spectrum width is 220 ppm with offset at resonance of -110 ppm. The processing and analyzing were done by MNOVA. The dataset consists 45371 complex points and is zero-filled to the size of 128k points after applying 5Hz exponential line broadening. The 19F chemical shift was referenced indirectly based on proton chemical shift, which was referenced with respect to the water proton signal of 4.75 ppm at 25°C. RESULTS: Visible DF cell morphology changes begin to appear as early as 1 hour exposure to 0.03% SDF in Transwells and continue with degradation of cell morphology through 8 hours exposure at which point 100% of the cell monolayer is lost. The 8 hour image shows complete cell loss which is consistent with earlier studies using 24 hour exposures at 0.03% concentration. Note that the actual concentration of SDF affecting cell viability is shown in this study to be far lower than the 0.03% input because of the aggregate precipitation captured with the Transwell inserts. In this study, our NMR fluoride assessments showed that only 6-12 % of the input SDF fluoride reaches the lower cell chamber. CONCLUSIONS: Considering that the SDF reagent is applied orally at ~40%, these results warrant more refined testing to identify true lower limit of toxicity end points of SDF. SDF should be utilized only by trained professionals and never contact soft tissue. NMR may be utilized to determine relative amounts of fluoride both in cell culture media and within fluoride exposed cells.

Gold and silver nanoparticles effects to the earthworm Eisenia fetida - the importance of tissue over soil concentrations.

To address and to compare the respective impact of gold and silver nanoparticles (Au and Ag NPs) in soil invertebrate, the earthworm Eisenia fetida was exposed to soil containing 2, 10, and 50 mg/kg of Au and Ag in both nanoparticulate and ionic forms for 10 days. Both metal NPs were 2-15 times less bioavailable than their ionic forms, and displayed similar transfer coefficients from soil to earthworm tissues. Both metal NPs triggered the onset of an oxidative stress as illustrated by increased glutathione S-transferase levels, decreased catalase levels, and increased malondialdehyde concentrations. Protein carbonylation distinguished the nanoparticular from the ionic forms as its increase was observed only after exposure to the highest concentration of both metal NPs. Au and Ag NPs triggered DNA modifications even at the lowest concentration, and both repressed the expression of genes involved in the general defense and stress response at high concentrations as did their ionic counterparts. Despite the fact that both metal NPs were less bioavailable than their ionic forms, at equivalent concentrations accumulated within earthworms tissues they exerted equal or higher toxic potential than their ionic counterparts.Capsule: At equivalent concentrations accumulated within earthworm tissues Au and Ag NPs exert equal or higher toxic potential than their ionic forms.

Tranilast ameliorated subchronic silver nanoparticles-induced cerebral toxicity in rats: Effect on TLR4/NLRP3 and Nrf-2.

Silver nanoparticles (AgNPs) are widely applied in various aspects of life. However, recent studies reported their potential toxicity both on environment and human health. The present study aimed to unravel the underlying molecular mechanisms involved in AgNPs-induced brain toxicity. Moreover, chemopreventive effect of tranilast, an analogue of tryptophan metabolite and a mast cell membrane stabilizer was evaluated. Thirty Sprague Dawley rats were enrolled equally into Normal control group, AgNPs-intoxicated group (50 mg/kg, 3 times/week) and tranilast (300 mg/kg, 3 times/week)+AgNPs group. AgNPs administration triggered brain oxidative stress as depicted by reduced Nrf-2 expression, decreased TAC and GSH as well as upregulated brain lipid peroxidation. The apparent brain oxidative damage was accompanied by elevated levels of inflammatory cytokines (IL-1ß, IL-6 and TNF-α). Moreover, brain levels of TLR4, NLRP3 and caspase-1 were up-regulated. Additionally, histological study indicated marked cellular injury in cerebrum and cerebellum specimens. This was concomitant with elevated serum CK activity and CK-BB level. On the other hand, tanilast administration remarkably alleviated AgNPs-induced brain toxicity. The present study shed the light on implication of TLR4/NLRP3 axis and NrF2 in AgNPs-induced brain toxicity. In addition, it explored the potential protective effect of tranilast on AgNPs-induced brain injury via antioxidant and anti-inflammatory efficacies.

Impact of Ag2S NPs on soil bacterial community - A terrestrial mesocosm approach.

Soils might be a final sink for Ag2S nanoparticles (NPs). Still, there are limited data on their effects on soil bacterial communities (SBC). To bridge this gap, we investigated the effects of Ag2S NPs (10 mg kg-1 soil) on the structure and function of SBC in a terrestrial indoor mesocosm, using a multi-species design. During 28 days of exposure, the SBC function-related parameters were analysed in terms of enzymatic activity, community level physiological profile, culture of functional bacterial groups [phosphorous-solubilizing bacteria (P-SB) and heterotrophic bacteria (HB)], and SBC structure was analysed by 16S rRNA gene-targeted denaturing gradient gel electrophoresis. The SBC exposed to Ag2S NPs showed a significative decrease of functional parameters, such as ß-glucosidase activity and L-arginine consumption, and increase of the acid phosphatase activity. At the structural level, significantly lower richness and diversity were detected, but at later exposure times compared to the AgNO3 treatment, likely because of a low dissolution rate of Ag2S NPs. In fact, stronger effects were observed in soils spiked with AgNO3, in both functional and structural parameters. Changes in SBC structure seem to negatively correlate with parameters related to phosphorous (acid phosphatase activity) and carbon cycling (abundance of HB, P-SB, and ß-glucosidase activity). Our results indicate a significant effect of Ag2S NPs on SBC, specifically on parameters related to carbon and phosphorous cycling, at doses as low as 10 mg kg-1 soil. These effects were only observed after 28 days, highlighting the importance of long-term exposure experiments for slowly dissolving NPs.

Phospholipids modifications in human hepatoma cell lines (HepG2) exposed to silver and iron oxide nanoparticles.

Metallic nanoparticles such as silver (Ag NPs) and iron oxide (Fe3O4 NPs) nanoparticles are high production volume materials due to their applications in various consumer products, and in nanomedicine. However, their inherent toxicities to human cells remain a challenge. The present study was aimed at combining lipidomics data with common phenotypically-based toxicological assays to gain better understanding into cellular response to Ag NPs and Fe3O4 NPs exposure. HepG2 cells were exposed to different concentrations (3.125, 6.25, 12.5, 25, 50 and 100 µg/ml) of the nanoparticles for 24 h, after which they were assayed for toxic effects using toxicological assays like cytotoxicity, mutagenicity, apoptosis and oxidative stress. The cell membrane phospholipid profile of the cells was also performed using shotgun tandem mass spectrometry. The results showed that nanoparticles exposure resulted in concentration-dependent cytotoxicity as well as reduced cytokinesis-block proliferation index (CBPI). Also, there was an increase in the production of ROS and superoxide anions in exposed cells compared to the negative control. The lipidomics data revealed that nanoparticles exposure caused a modulation of the phospholipidome of the cells. A total of 155 lipid species were identified, out of which the fold changes of 23 were significant. The high number of differentially changed phosphatidylcholine species could be an indication that inflammation is one of the major mechanisms of toxicity of the nanoparticles to the cells.

Combination of the BeWo b30 placental transport model and the embryonic stem cell test to assess the potential developmental toxicity of silver nanoparticles.

BACKGROUND: Silver nanoparticles (AgNPs) are used extensively in various consumer products because of their antimicrobial potential. This requires insight in their potential hazards and risks including adverse effects during pregnancy on the developing fetus. Using a combination of the BeWo b30 placental transport model and the mouse embryonic stem cell test (EST), we investigated the capability of pristine AgNPs with different surface chemistries and aged AgNPs (silver sulfide (Ag2S) NPs) to cross the placental barrier and induce developmental toxicity. The uptake/association and transport of AgNPs through the BeWo b30 was characterized using ICP-MS and single particle (sp)ICP-MS at different time points. The developmental toxicity of the AgNPs was investigated by characterizing their potential to inhibit the differentiation of mouse embryonic stem cells (mESCs) into beating cardiomyocytes. RESULTS: The AgNPs are able to cross the BeWo b30 cell layer to a level that was limited and dependent on their surface chemistry. In the EST, no in vitro developmental toxicity was observed as the effects on differentiation of the mESCs were only detected at cytotoxic concentrations. The aged AgNPs were significantly less cytotoxic, less bioavailable and did not induce developmental toxicity. CONCLUSIONS: Pristine AgNPs are capable to cross the placental barrier to an extent that is influenced by their surface chemistry and that this transport is likely low but not negligible. Next to that, the tested AgNPs have low intrinsic potencies for developmental toxicity. The combination of the BeWo b30 model with the EST is of added value in developmental toxicity screening and prioritization of AgNPs.

Histopathological study of the maternal exposure to the biologically produced silver nanoparticles on different organs of the offspring.

This research for the first time presents the possibility of crossing the biologically produced SNPs through the placenta to different organs of rat offspring. SNPs were produced using Fusarium oxysporum. After adding 1 mmol final concentration of silver nitrate solution to the culture supernatant and 5 min heating, SNPs were produced, and their production was proved using visible spectrum, transmission electron microscope (TEM), and X-ray diffraction (XRD) analyses. SNPs were washed, and their concentration determined using inductively coupled plasma (ICP) instrument. SNPs were used for 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and after determination of their half maximal inhibitory concentration (IC50) dose, their toxic and nontoxic doses were determined and used for in vivo studies. A total of 24 female rats, after detection of their vaginal plugs, were divided into 3 groups each having 8 members. A control group was treated with normal saline. The other two groups were treated by toxic and nontoxic doses of SNPs, respectively. After delivery and breastfeeding, the pups were scarified, and their organs were collected and analyzed using histological examinations. Results showed that SNPs had a maximum absorbance peak around 450 nm, with polygonal and round shapes. XRD results confirmed the presence of SNPs. The concentration of the SNPs after washing was 19 ppm/mL based on the ICP results. MTT assay results showed that SNPs had a dose-dependent toxic effect. Histopathological examination results showed that SNPs could pass through the placenta; both their nontoxic and toxic doses induced somehow mild alternations in the liver, kidney, testis, and ovary and had no effects on the brains of the rat offspring. In conclusions, the use of the biologically produced SNPs should be limited during pregnancy and breastfeeding.

Biodistribution and organ oxidative damage following 28 days oral administration of nanosilver with/without coating in mice.

This study evaluated the biodistribution and organ oxidative effects of silver nanoparticles (AgNPs) coated with/without polyvinylpyrrolidone (PVP) (AgNP-20 and AgNP-PVP) in mice; these were administered by gavage at a dose of 10-250 mg/kg body weight per day for 28 days. The results showed that both the AgNPs could induce subacute toxicity and oxidative damage to mice and were mainly accumulated in the liver and spleen and excreted by feces. AgNPs could be absorbed into blood and might cross the blood-brain barrier, and be distributed extensively in mice. The malondialdehyde content in the liver, lungs and kidneys increased in both AgNP groups, while the content of glutathione decreased, and the activity of superoxide dismutase increased at first and then decreased along with the increased doses. Inflammatory pathological changes in the lung and liver at high dose of both AgNPs were consistent with increases in glutamate pyruvic transaminase, glutamate oxaloacetic transaminase and the total protein in serum detection. The Ag content was detected in organs, with the highest content in the liver, followed by spleen, while the Ag content in feces was about 500 times higher than that in urine. AgNP-PVP could induce higher oxidative stress and subacute toxicity than AgNP-20 at the same dose, which might be related to the higher concentrations and more Ag+ ions released in mice after AgNP-PVP exposure. The data from this research provided information on toxicity and biodistribution of AgNPs following gavage administration in mice, and might shed light for future application of AgNPs in daily life.

Comparative study of antibacterial activity between Schiff base nicotinic hydrazide derivative and its silver architected nanoparticles with atomic force microscopic study of bacterial cell wall.

The threat of multi-drug resistant bacterial pathogens evokes researchers to synthesized safe and effective chemotherapeutic agents for nano-drug delivery system. In current study, Schiff base of nicotinic hydrazide(NHD) and its silver nanoparticles(NHD-AgNPs) were synthesized and characterized. These compounds were investigated for cytotoxicity, antibacterial and AFM activity. The NHD showed LD50 at >1000µg/mL while NHD-AgNPs didn't exhibit toxicity at 1000µg/mL against 3T3 cell line. The NHD showed zone of inhibition against two strains of salmonella enteric (ATCC 14028 and 700408) 45.29±1.66 and 48.01±1.43mm respectively at 160µg/mL (p<0.01) while NHD-AgNPs exhibited 55.87±2.08 and 52.88±1.42 mm respectively at 130µg/mL (p<0.001) in disc diffusion method. NHD showed more than 70% growth inhibition for both strains at 85 and 125µg/ml (p<0.01) respectively, while NHD-AgNPs inhibit 80% and 75% respectively at 75 and 125 µg/ml (p<0.01, p<0.001) against Alamar blue antibacterial assay. For morphological changes in bacterial cell wall NHD and NHD-AgNPs treated bacterial cells were observed under atomic force microscope(AFM) and treated bacterial cells were severely damaged with leaked cytoplasmic contents as compare to untreated bacterial cell. These results validate that NHD-AgNPs were highly active as compared to NHD against both strains at their MIC concentrations. In future, comparative wound healing potential will be emphasized.

Ecotoxicology of silver nanoparticles and their derivatives introduced in soil with or without sewage sludge: A review of effects on microorganisms, plants and animals.

Silver nanoparticles (AgNPs) are widely incorporated in many products, partly due to their antimicrobial properties. The subsequent discharge of this form of silver into wastewater leads to an accumulation of silver species (AgNPs and derivatives resulting from their chemical transformation), in sewage sludge. As a result of the land application of sewage sludge for agricultural or remediation purposes, soils are the primary receiver media of silver contamination. Research on the long-term impact of AgNPs on the environment is ongoing, and this paper is the first review that summarizes the existing state of scientific knowledge on the potential impact of silver species introduced into the soil via sewage sludge, from microorganisms to earthworms and plants. Silver species can easily enter cells through biological membranes and affect the physiology of organisms, resulting in toxic effects. In soils, exposure to AgNPs may change microbial biomass and diversity, decrease plant growth and inhibit soil invertebrate reproduction. Physiological, biochemical and molecular effects have been documented in various soil organisms and microorganisms. Negative effects on organisms of the dominant form of silver in sewage sludge, silver sulfide (Ag2S), have been observed, although these effects are attenuated compared to the effects of metallic AgNPs. However, silver toxicity is complex to evaluate and much remains unknown about the ecotoxicology of silver species in soils, especially with respect to the possibility of transfer along the trophic chain via accumulation in plant and animal tissues. Critical points related to the hazards associated with the presence of silver species in the environment are described, and important issues concerning the ecotoxicity of sewage sludge applied to soil are discussed to highlight gaps in existing scientific knowledge and essential research directions for improving risk assessment.

Cytotoxic effects of silver diamine fluoride.

PURPOSE: To investigate the effect of silver diamine fluoride (SDF) and fluoride varnish (FV) on human gingival fibroblasts (HGF) and bacteria. METHODS: HGF cell viability was assessed after exposure to various dilutions of SDF or FV. Hydroxyapatite (HA) discs treated with SDF, FV, or saline were rinsed in artificial saliva for 84 days. HGF were exposed to treated discs and viability assessed fluorescently. Oral bacteria were exposed to treated discs and survival quantified. RESULTS: At 0.01%, SDF was almost 100% cytotoxic to HGF. SDF and FV treated HA discs, induced near-complete cell death after 24 hours of contact. After rinsing FV discs for 21 days, cell survival exceeded 95%. SDF treated discs were toxic to HGF and bacteria after 9 weeks of rinsing. CLINICAL SIGNIFICANCE: SDF and FV can induce cell death. FV lost its cytotoxicity within 3 weeks, while SDF remained cytotoxic even after 9 weeks of rinsing. This research confirms that SDF has long lasting antimicrobial effects at very low concentrations although it does raise concerns regarding cytotoxicity. However, HGF cells are exposed to other cytotoxic substances in dentistry with little, if any, long-term effects.