Bioavailability and Toxicokinetics of citrate-coated silver nanoparticles in rats

Chiral silver nanoparticles with surface-anchored L(D)-Cys exhibit dissimilar biological characteristics in vitro but not in vivo

This work investigated the influence of surface chirality on cellular internalization, cytotoxicity, and tissue distribution of silver nanoparticles (AgNPs). D-cysteine and L-cysteine are chiral forms of the amino acid cysteine. These enantiomers exhibit distinct spatial arrangements, with D-cysteine having a different configuration from L-cysteine. This structural dissimilarity can lead to variations in how these forms interact with biological systems, potentially impacting their cytotoxic responses. Four distinct types of AgNPs were synthesized, each possessing a unique surface coating: pristine AgNPs (pAgNPs), L-cysteine coated AgNPs (AgNPs@L-Cys), D-cysteine coated AgNPs (AgNPs@D-Cys), and racemic AgNPs coated with both L-Cys and D-Cys (AgNPs@L/D-Cys). We found chiral-dependent cytotoxicity of AgNPs on J774A.1 cells. Specifically, AgNPs@L-Cys exhibited the highest toxicity, and AgNPs@D-Cys exhibited the lowest toxicity. Meanwhile, the cellular uptake of the AgNPs correlated nicely with their cytotoxicity, with AgNPs@L-Cys being internalized to the greatest extent while AgNPs@D-Cys displays the least internalization. Scavenger receptors and clathrin predominantly mediate the cellular internalization of these AgNPs. Strikingly, the dissimilar cellular internalization and cytotoxicity of AgNPs with different chirality were eliminated upon protein corona coverage. Notably, following intravenous injection in mice, these four types of AgNPs showed similar patterns among various organs due to the inevitable protein adsorption in the bloodstream. These findings underscored the pivotal role of surface chirality in governing the biological interactions and toxicity of AgNPs.

Assessment of Toxicity of Green Synthesized Silver Nanoparticle-coated Titanium Mini-implants with Uncoated Mini-implants: Comparison in an Animal Model Study

AIM

To assess the potential for systemic toxicity when silver nanoparticle-coated mini-implants were implanted in Wistar albino rats conducted as a comparative study in the animal model by assessing the blood biochemistry, liver and kidney function, and histology of the implanted site.

MATERIALS AND METHODS

The surface of the mini-implant was coated with a green-mediated silver nanoparticle. Uncoated mini-implants were placed in two groups of eight Wistar albino rats, and silver nanoparticle-coated mini-implants were placed in another eight rats. The bone's general conditions, blood biochemistry assessing for ALT, AST, GPT, GOT, and histological sections using H and E stain and Masson's Trichrome stain were examined at 7, 14, and 28-day intervals.

RESULTS

The creatinine, urea, ALP, and ALT showed no signs of systemic toxicity during the 28-day follow-up period in the Wistar rats both in the test and control groups. The histological evaluation, which was conducted using HE and MTS stain, revealed osteogenesis and adequate healing of the insertion site in the group where coated mini-implant was placed. The bone sample revealed no abnormalities in the control group with uncoated mini-implants.

CONCLUSION

Green synthesized silver nanoparticle-coated mini-implant does not cause systemic toxicity as indicated by no abnormalities in the levels of creatinine, urea, ALT, ALP, GPT, and GOT. The bone histology indicates that the coated mini-implants placed in animal bone healed with adequate osteogenesis.

CLINICAL SIGNIFICANCE

Silver nanoparticles have potential for antimicrobial activity. Mini-implants placed as temporary anchorage devices in orthodontics often fail due to inflammation and plaque. Silver nanoparticle-coated mini-implants would reduce the risk of mini-implant failure as it would have antimicrobial potential and eliminate this cause for failure of mini-implants. How to cite this article: Sreenivasagan S, Subramanian AK, Mohanraj KG, et al. Assessment of Toxicity of Green Synthesized Silver Nanoparticle-coated Titanium Mini-implants with Uncoated Mini-implants: Comparison in an Animal Model Study. J Contemp Dent Pract 2023;24(12):944-950.

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.

Transformation, Absorption and Toxicological Mechanisms of Silver Nanoparticles in the Gastrointestinal Tract Following Oral Exposure

Oral exposure is known as the primary way for silver nanoparticles (AgNPs), which are commonly used as food additives or antibacterial agents in commercial products, to enter the human body. Although the health risk of AgNPs has been a concern and extensively researched over the past few decades, there are still numerous knowledge gaps that need to be filled to disclose what AgNPs experience in the gastrointestinal tract (GIT) and how they cause oral toxicity. In order to gain more insight into the fate of AgNPs in the GIT, the main gastrointestinal transformation of AgNPs, including aggregation/disaggregation, oxidative dissolution, chlorination, sulfuration, and corona formation, is first described. Second, the intestinal absorption of AgNPs is presented to show how AgNPs interact with epithelial cells and cross the intestinal barrier. Then, more importantly, we make an overview of the mechanisms underlying the oral toxicity of AgNPs in light of recent advances as well as the factors affecting the nano-bio interactions in the GIT, which have rarely been thoroughly elaborated in published literature. At last, we emphatically discuss the issues that need to be addressed in the future to answer the question "How does oral exposure to AgNPs cause detrimental effects on the human body?".

Effects of silver nanoparticles on maternal mammary glands and offspring development under lactation exposure

The widespread applications of silver nanoparticles (AgNPs) throughout our daily lives have raised concerns regarding their environmental health and safety (EHS). Despite an increasing number of studies focused on the EHS impacts of AgNPs, there remain significant knowledge gaps with respect to their potential health impacts on susceptible populations, such as lactating mothers and infants. Herein, we aimed to investigate the deleterious effects of AgNPs with different sizes (20 and 40 nm) and surface coatings (PVP and BPEI) on maternal mice and their offspring following lactation exposure at doses of 20, 100 and 400 μg/kg body weight. We discovered that AgNPs could accumulate in the maternal mammary glands and disrupt the epithelial barrier in a dose-dependent manner. Notably, BPEI-coated AgNPs caused more damage to the mammary glands than PVP-coated particles. Importantly, we observed that, while AgNPs were distributed throughout the blood and main tissues, they were particularly enriched in the brains of breastfed offspring after maternal exposure during lactation, exhibiting exposure dosage- and particle coating-dependent patterns. Compared to PVP-coated nanoparticles, BPEI-coated AgNPs were more readily transferred to the offspring, possibly due to their enhanced deposition in maternal mammary glands. Moreover, we observed reduced body weight, blood cell toxicity, and tissue injuries in breastfed offspring whose dams received AgNPs. As a whole, these results reveal that maternal exposure to AgNPs results in the translocation of AgNPs into offspring via breastfeeding, inducing developmental impairments in these breastfed offspring. This study provides important new insights into the EHS impacts of AgNP consumption during lactation.

Silver contamination and its toxicity and risk management in terrestrial and aquatic ecosystems

Silver (Ag), a naturally occurring, rare and precious metal, is found in major minerals such as cerargyrite (AgCl), pyrargyrite (Ag₃SbS₃), proustite (Ag₃AsS₃), and stephanite (Ag₅SbS₄). From these minerals, Ag is released into soil and water through the weathering of rocks and mining activities. Silver also enters the environment by manufacturing and using Ag compounds in electroplating and photography, catalysts, medical devices, and batteries. With >400 t of Ag NPs produced yearly, Ag NPs have become a rapidly growing source of anthropogenic Ag input in the environment. In soils and natural waters, most Ag is sorbed to soil particles and sediments and precipitated as oxides, carbonates, sulphides, chlorides and hydroxides. Silver and its compounds are toxic, and humans and other animals are exposed to Ag through inhalation of air and the consumption of Ag-contaminated food and drinking water. Remediation of Ag-contaminated soil and water sources can be achieved through immobilization and mobilization processes. Immobilization of Ag in soil and groundwater reduces the bioavailability and mobility of Ag, while mobilization of Ag in the soil can facilitate its removal. This review provides an overview of the current understanding of the sources, geochemistry, health hazards, remediation practices and regulatory mandates of Ag contamination in complex environmental settings, including soil and aquatic ecosystems. Knowledge gaps and future research priorities in the sustainable management of Ag contamination in these settings are also discussed.

Osteoregeneration of Critical-Size Defects Using Hydroxyapatite-Chitosan and Silver-Chitosan Nanocomposites

Bone is a natural nanocomposite composed of proteins and minerals that can regenerate itself. However, there are conditions in which this process is impaired, such as extensive bone defects and infections of the bone or surrounding tissue. This study evaluates the osteoregenerative capacity of bone grafting materials in animals with induced bone defects. Colloidal chitosan dispersion nanocomposites, nanohydroxyapatite−chitosan (NHAP-Q) and nanosilver−chitosan (AgNP-Q), were synthesized and characterized. Non-critical-size defects in Wistar rats were used to evaluate the material’s biocompatibility, and critical-size defects in the calvarias of guinea pigs were used to evaluate the regenerative capacity of the bones. Moreover, the toxicity of the nanocomposites was evaluated in the heart, liver, spleen, kidneys, and skin. Histological, radiographic, and electron microscopy tests were also performed. The results showed that neither material produced pathological changes. Radiographic examination showed a significant reduction in defects (75.1% for NHAP-Q and 79.3% for AgNP-Q), angiogenesis, and trabecular formation. A toxicological assessment of all the organs did not show changes in the ultrastructure of tissues, and the distribution of silver was different for different organs (spleen > skin > heart > kidney > liver). The results suggest that both materials are highly biocompatible, and AgNP-Q achieved similar bone regeneration to that reported with autologous bone. The main research outcome of the present study was the combination of two types of NPs to enhance antimicrobial and osteoregeneration activities. These colloidal chitosan dispersions show promise as future biomaterials in the medical field for applications in fast-healing fractures, including broken bones in the oral cavity and hip replacement infections.

Different coatings on magnetic nanoparticles dictate their degradation kinetics in vivo for 15 months after intravenous administration in mice

BACKGROUND

The surface coating of iron oxide magnetic nanoparticle (MNPs) drives their intracellular trafficking and degradation in endolysosomes, as well as dictating other cellular outcomes. As such, we assessed whether MNP coatings might influence their biodistribution, their accumulation in certain organs and their turnover therein, processes that must be understood in vivo to optimize the design of nanoformulations for specific therapeutic/diagnostic needs.

RESULTS

In this study, three different MNP coatings were analyzed, each conferring the identical 12 nm iron oxide cores with different physicochemical characteristics: 3-aminopropyl-triethoxysilane (APS), dextran (DEX), and dimercaptosuccinic acid (DMSA). When the biodistribution of these MNPs was analyzed in C57BL/6 mice, they all mainly accumulated in the spleen and liver one week after administration. The coating influenced the proportion of the MNPs in each organ, with more APS-MNPs accumulating in the spleen and more DMSA-MNPs accumulating in the liver, remaining there until they were fully degraded. The changes in the physicochemical properties of the MNPs (core size and magnetic properties) was also assessed during their intracellular degradation when internalized by two murine macrophage cell lines. The decrease in the size of the MNPs iron core was influenced by their coating and the organ in which they accumulated. Finally, MNP degradation was analyzed in the liver and spleen of C57BL/6 mice from 7 days to 15 months after the last intravenous MNP administration.

CONCLUSIONS

The MNPs degraded at different rates depending on the organ and their coating, the former representing the feature that was fundamental in determining the time they persisted. In the liver, the rate of degradation was similar for all three coatings, and it was faster than in the spleen. This information regarding the influence of coatings on the in vivo degradation of MNPs will help to choose the best coating for each biomedical application depending on the specific clinical requirements.

Mitotic and chromosomal effects induced for biosynthesized nanoparticles from three mediators on Allium cepa root cells

The genotoxicity of biogenic silver nanoparticles (AgNPs) obtained from three microbial mediators was assessed using the Allium cepa assay. Three clusters were differentiated for the highest frequency of end points of clastogenicity (stick-ends, fragments and bridges), end points of missegregation (C-metaphases and disorder anaphases), and lowest frequency of all the end points. In these clusters, the treatments were grouped respectively as I) positive control (GSF); II) silver nanoparticles form Aspergillus niger (AgNPs-An); and III) silver nanoparticles from both Cryptococcus laurentii (AgNPs-Cl) and Rhodotorula glutinis (AgNPs-Rg), Ag + , and negative control (NC). These results were in according to the principal component analisys (PCA) where treatments were associated to each component of the genotoxic effects. The statistical comparative analysis of the mitotic index (IM) and the abnormal mitosis frequency (AM) indicated that both GSF and AgNPsAn induce significant genotoxic effect. Low genotoxic effects were attributed to AgNPs-Cl and AgNPs-Rg, but mitogenic stimuli, similar to that obtained by the silver ions Ag + , were observed. Results suggested that different features of biogenic nanoparticles such as composition, size, and coating may be involved in the different cytological responses of the meristematic cells.

Greater Bioaccessibility of Silver Nanoparticles in Earthworm than in Soils

The buildup of silver nanoparticles (AgNPs) in soil has raised mounting concerns on their impact on human health. Human are exposed to AgNPs in soils via hand-to-mouth activities (direct exposure) and food consumption (indirect exposure). However, the bioaccessibility of AgNPs under these exposure scenarios remains largely unknown. We used a physiologically based extraction test (PBET) to assess Ag bioaccessibility in AgNP-containing soils and in earthworms (Pheretima guillemi) cultured in these soils. Silver bioaccessibility was 1.2 - 8.4% and 8.1 - 78.7% upon direct exposure and indirect exposure, respectively. These results indicated greater Ag bioaccessibility in earthworms than in soils. Moreover, particle size decreased upon direct exposure, but remained constant upon indirect exposure in wetland soil, as revealed by single particle inductively coupled plasma-mass spectrometry (spICP-MS) analysis. Our results highlight the importance of indirect exposure to NPs.

Investigation of Antimicrobial Activity and Biocompatibility of Biogenic Silver Nanoparticles Synthesized using Syzigyum cymosum Extract

Nanotherapeutics has emerged as the most sought after approach to tackle the menace of drug-resistant pathogenic bacteria. Among others, biogenic silver nanoparticles (bAgNPs) synthesized using medicinal plant extracts demonstrate promising antibacterial propensity with excellent biocompatibility. Herein, bAgNPs were synthesized through the green chemistry approach using Syzygium cymosum leaf extract as a reducing agent at different pH values (i.e., 5, 7, 8, and 10). The average size of bAgNPs synthesized at pH 5, 7, 8, and 10 was 23.3, 21.3, 17.2, and 35.3 nm, respectively, and all the nanoparticles were negatively charged. Their antibacterial potential was investigated against Bacillus subtilis, Escherichia coli DH5α, E. coli K12, enteropathogenic E. coli, and Salmonella typhi. The highest antibacterial activity was exhibited by bAgNPs synthesized at pH 8 against all the tested bacterial strains, which can be attributed to their small size and greater surface area to volume ratio. The bAgNPs demonstrated the highest zone of inhibition (29.5 ± 0.8 mm) against B. subtilis through oxidation of membrane fatty acids that resulted in the formation of the malondialdehyde-thiobarbituric acid (MDA-TBA) adduct. However, bAgNPs demonstrated excellent hemocompatibility with rat and human red blood cells. Biogenic AgNPs synthesized at pH 8 also exhibited biocompatibility in terms of liver and kidney function biomarkers. Furthermore, hematoxylin and eosin staining of the tissue sections of vital organs (i.e., liver, kidneys, lungs, heart, spleen, and brain) also confirmed the biocompatibility of bAgNPs.

Histomorphological changes and molecular mechanisms underlying the ameliorative effect of resveratrol on the liver of silver nanoparticles-exposed rats

Exposure to the deleterious effects of silver nanoparticles (AgNPs) is inevitable due to their wide use in medicine and daily life. The current study aimed to delineate the histomorphological changes and the molecular mechanisms underlying the ameliorative effect of Resveratrol (RSV) on rats' livers exposed to AgNPs. Fifty healthy adult male Wistar albino rats were divided into four groups: control, AgNPs-exposed, RSV-treated after AgNPs exposure, and recovery groups. Liver sections were examined by light and electron microscopes, and immunohistochemistry was performed for detection of activated caspase3 and TNFα. Serum ALT and AST, plasma levels of TNFα, IL-6, GSH and SOD were measured. mRNA expression of SIRT1, ADORA3, PAI, CDK1, Nrf2 and NFκB genes in liver tissue homogenate was performed using qRT-PCR. AgNPs-exposure for 28 days caused marked liver tissue damage with trapping in hepatocytes and Kupffer cells, while RSV treatment ameliorated liver ultrastructure and function. Our results clarified the molecular basis of RSV ameliorative effect on liver tissue by significant upregulation of SIRT1-NrF2 signaling pathway with increased levels of the antioxidant GSH and SOD, which represent the antioxidant effect of RSV. Significant upregulation of the protective ADORA3 with downregulation of the proinflammatory PAI-1 and NFκB mRNA expression levels besides decreased plasma levels of TNFα, IL-6 and decreased immunoexpression of TNFα in liver tissue, represent the anti-inflammatory effect of RSV. In addition, decreased immunoexpression of caspase3 and downregulation of CDK1 expression, represent its antiapoptotic effect. In conclusion: RSV ameliorates AgNPs-induced liver damage by antioxidant, anti-inflammatory and antiapoptotic effects.Abbreviations: AgNPs: Silver nanoparticles, RSV: Resveratrol, ROS: Reactive oxygen species, ESR: Electron spin resonance, DMPO: 5,5-Dimethyl-1-pyrroline-N-oxide, H₂O₂: Hydrogen peroxide, SOD: Superoxide dismutase, CAT: Catalase, GPx: Glutathione peroxidase, MPTP: Methyl-4-phenyl-1.2.3.6-tetrahydropyridine, MDA: Malondialdehyde, TNF: Tumor necrosis factor, GSH: Glutathione, Nrf2: Nuclear factor-erythroid 2-related factor 2, ARE: Antioxidant response elements, KEAP1: Kelch-1ike ECH-associated protein l, AMPK: AMP-activated protein kinase, HO-1: Heme oxygenase-1, NF-κB: Nuclear factor-kappa B, SIRT1: Sirtuins, FOXO: Forkhead box, UCP2: Uncoupling protein 2, STZ: Streptozotocin nicotinamide, HSC: hepatic stellate cells, ECM: extracellular matrix.

Cancer Therapy by Silver Nanoparticles: Fiction or Reality?

As an emerging new class, metal nanoparticles and especially silver nanoparticles hold great potential in the field of cancer biology. Due to cancer-specific targeting, the consequently attenuated side-effects and the massive anti-cancer features render nanoparticle therapeutics desirable platforms for clinically relevant drug development. In this review, we highlight those characteristics of silver nanoparticle-based therapeutic concepts that are unique, exploitable, and achievable, as well as those that represent the critical hurdle in their advancement to clinical utilization. The collection of findings presented here will describe the features that distinguish silver nanoparticles from other anti-cancer agents and display the realistic opportunities and implications in oncotherapeutic innovations to find out whether cancer therapy by silver nanoparticles is fiction or reality.

Sex affects the response of Wistar rats to polyvinyl pyrrolidone (PVP)-coated silver nanoparticles in an oral 28 days repeated dose toxicity study

BACKGROUND

Silver nanoparticles (AgNPs) are widely used in biomedicine due to their strong antimicrobial, antifungal, and antiviral activities. Concerns about their possible negative impacts on human and environmental health directed many researchers towards the assessment of the safety and toxicity of AgNPs in both in vitro and in vivo settings. A growing body of scientific information confirms that the biodistribution of AgNPs and their toxic effects vary depending on the particle size, coating, and dose as well as on the route of administration and duration of exposure. This study aimed to clarify the sex-related differences in the outcomes of oral 28 days repeated dose exposure to AgNPs.

METHODS

Wistar rats of both sexes were gavaged daily using low doses (0.1 and 1 mg Ag/kg b.w.) of polyvinylpyrrolidone (PVP)-coated small-sized (10 nm) AgNPs. After exposure, blood and organs of all rats were analysed through biodistribution and accumulation of Ag, whereas the state of the liver and kidneys was evaluated by the levels of reactive oxygen species (ROS) and glutathione (GSH), catalase (CAT) activity, superoxide dismutase (SOD) and glutathione peroxidase (GPx), expression of metallothionein (Mt) genes and levels of Mt proteins.

RESULTS

In all animals, changes in oxidative stress markers and blood parameters were observed indicating the toxicity of AgNPs applied orally even at low doses. Sex-related differences were noticed in all assessed parameters. While female rats eliminated AgNPs from the liver and kidneys more efficiently than males when treated with low doses, the opposite was observed for animals treated with higher doses of AgNPs. Female Wistar rats exposed to 1 mg PVP-coated AgNPs/kg b.w. accumulated two to three times more silver in the blood, liver, kidney and hearth than males, while the accumulation in most organs of digestive tract was more than ten times higher compared to males. Oxidative stress responses in the organs of males, except the liver of males treated with high doses, were less intense than in the organs of females. However, both Mt genes and Mt protein expression were significantly reduced after treatment in the liver and kidneys of males, while they remained unchanged in females.

CONCLUSIONS

Observed toxicity effects of AgNPs in Wistar rats revealed sex-related differences in response to an oral 28 days repeated exposure.

Minocycline-Derived Silver Nanoparticles for Assessment of Their Antidiabetic Potential against Alloxan-Induced Diabetic Mice

Diabetes is a life-threatening disease, and chronic diabetes affects parts of the body including the liver, kidney, and pancreas. The root cause of diabetes is mainly associated with oxidative stress produced by reactive oxygen species. Minocycline is a drug with a multi-substituted phenol ring and has shown excellent antioxidant activities. The objective of the present study was to investigate the antidiabetic potential of minocycline-modified silver nanoparticles (mino/AgNPs) against alloxan-induced diabetic mice. The mino/AgNPs were synthesized using minocycline as reducing and stabilizing agents. UV-visible, FT-IR, X-ray diffraction (XRD), and transmission electron microscopy (TEM) were applied for the characterization of mino/AgNPs. A 2,2-diphenyl-1-picrylhydrazyl free radical scavenging assay was conducted to determine the antioxidant potential of newly synthesized mino/AgNPs. The results revealed that the mino/AgNPs showed higher radical scavenging activity (IC₅₀ = 19.7 µg/mL) compared to the minocycline (IC₅₀ = 26.0 µg/mL) and ascorbic acid (IC₅₀ = 25.2 µg/mL). Further, mino/AgNPs were successfully employed to examine their antidiabetic potential against alloxan-induced diabetic mice. Hematological results showed that the mice treated with mino/AgNPs demonstrated a significant decrease in fasting blood glucose level and lipid profile compared to the untreated diabetic group. A histopathological examination confirmed that the diabetic mice treated with mino/AgNPs showed significant recovery and revival of the histo-morphology of the kidney, central vein of the liver, and islet cells of the pancreas compared to the untreated diabetic mice. Hence, mino/AgNPs have good antidiabetic potential and could be an appropriate nanomedicine to prevent the development of diabetes.

The Bio-Persistence of Reversible Inflammatory, Histological Changes and Metabolic Profile Alterations in Rat Livers after Silver/Gold Nanorod Administration

As a widely applied nanomaterial, silver nanomaterials (AgNMs) have increased public concern about their potential adverse biological effects. However, there are few related researches on the long-term toxicity, especially on the reversibility of AgNMs in vivo. In the current study, this issue was tackled by exploring liver damage after an intravenous injection of silver nanorods with golden cores (Au@AgNRs) and its potential recovery in a relatively long term (8 w). After the administration of Au@AgNRs into rats, Ag was found to be rapidly cleared from blood within 10 min and mainly accumulated in liver as well as spleen until 8 w. All detected parameters almost displayed a two-stage response to Au@AgNRs administration, including biological markers, histological changes and metabolic variations. For the short-term (2 w) responses, some toxicological parameters (hematological changes, cytokines, liver damages etc.) significantly changed compared to control and AuNRs group. However, after a 6-week recovery, all abovementioned changes mostly returned to the normal levels in the Au@AgNRs group. These indicated that after a lengthy period, acute bioeffects elicited by AgNMs could be followed by the adaptive recovery, which will provide a novel and valuable toxicity mechanism of AgNMs for potential biomedical applications of AgNMs.

Fructose-coated Ångstrom silver prevents sepsis by killing bacteria and attenuating bacterial toxin-induced injuries

Serious infection caused by multi-drug-resistant bacteria is a major threat to human health. Bacteria can invade the host tissue and produce various toxins to damage or kill host cells, which may induce life-threatening sepsis. Here, we aimed to explore whether fructose-coated Ångstrom-scale silver particles (F-AgÅPs), which were prepared by our self-developed evaporation-condensation system and optimized coating approach, could kill bacteria and sequester bacterial toxins to attenuate fatal bacterial infections.

Methods: A series of in vitro assays were conducted to test the anti-bacterial efficacy of F-AgÅPs, and to investigate whether F-AgÅPs could protect against multi-drug resistant Staphylococcus aureus (S. aureus)- and Escherichia coli (E. coli)-induced cell death, and suppress their toxins (S. aureus hemolysin and E. coli lipopolysaccharide)-induced cell injury or inflammation. The mouse models of cecal ligation and puncture (CLP)- or E. coli bloodstream infection-induced lethal sepsis were established to assess whether the intravenous administration of F-AgÅPs could decrease bacterial burden, inhibit inflammation, and improve the survival rates of mice. The levels of silver in urine and feces of mice were examined to evaluate the excretion of F-AgÅPs.

Results: F-AgÅPs efficiently killed various bacteria that can cause lethal infections and also competed with host cells to bind with S. aureus α-hemolysin, thus blocking its cytotoxic activity. F-AgÅPs inhibited E. coli lipopolysaccharide-induced endothelial injury and macrophage inflammation, but not by directly binding to lipopolysaccharide. F-AgÅPs potently reduced bacterial burden, reversed dysregulated inflammation, and enhanced survival in mice with CLP- or E. coli bloodstream infection-induced sepsis, either alone or combined with antibiotic therapy. After three times injections within 48 h, 79.18% of F-AgÅPs were excreted via feces at the end of the 14-day observation period.

Conclusion: This study suggests the prospect of F-AgÅPs as a promising intravenous agent for treating severe bacterial infections.

Repeated oral administration of low doses of silver in mice: tissue distribution and effects on central nervous system

BACKGROUND

Widespread use of silver in its different forms raises concerns about potential adverse effects after ingestion, the main exposure route for humans. The aim of this study was to investigate in CD-1 (ICR) male mice the tissue distribution and in vivo effects of 4-week oral exposure to 0.25 and 1 mg Ag/kg bw 10 nm citrate coated silver nanoparticles (AgNPs) and 1 mg Ag/kg bw silver acetate (AgAc) at the end of treatment (EoT) and after 4 weeks of recovery.

RESULTS

There were no treatment-related clinical signs and mortality, and no significant effects on body and organ weights at the EoT and after recovery. Treatment-related changes in hematology and clinical chemistry were found after recovery, the most relevant being a dose-dependent lymphopenia and increased triglycerides in AgNP-treated mice, and increased levels of urea in all treated groups, associated with decreased albumin only in AgAc-treated mice. At the EoT the highest silver concentration determined by Triple Quadrupole ICP-MS analysis was found in the brain, followed by testis, liver, and spleen; much lower concentrations were present in the small intestine and kidney. Tissue silver concentrations were slightly higher after exposure to AgAc than AgNPs and dose dependent for AgNPs. After recovery silver was still present in the brain and testis, highlighting slow elimination. No histopathological changes and absence of silver staining by autometallography were observed in the organs of treated mice. At the EoT GFAP (astrocytes) immunoreactivity was significantly increased in the hippocampus of AgNP-treated mice in a dose-dependent manner and Iba1 (microglial cells) immunoreactivity was significantly increased in the cortex of 1 mg/kg bw AgNP-treated mice. After recovery, a significant reduction of Iba1 was observed in the cortex of all treated groups. TEM analysis of the hippocampus revealed splitting of basement membrane of the capillaries and swelling of astrocytic perivascular end-feet in 1 mg/kg bw AgNP- and AgAc-treated mice at the EoT.

CONCLUSIONS

Our study revealed accumulation and slow clearance of silver in the brain after oral administration of 10 nm AgNPs and AgAc at low doses in mice, associated with effects on glial cells and ultrastructural alterations of the Blood-Brain Barrier.

Perinatal exposure to silver nanoparticles reprograms immunometabolism and promotes pancreatic beta-cell death and kidney damage in mice

Silver nanoparticles (AgNPs) are extensively utilized in food, cosmetics, and healthcare products. Though the effects of AgNPs exposure on adults are well documented, the long-term effects of gestational/perinatal exposure upon the health of offspring have not been addressed. Herein, we show that only perinatal exposure to AgNPs through the mother could lead to chronic inflammation in offspring which persists till adulthood. Further, AgNPs exposure altered offspring's immune responses against environmental stresses. AgNPs exposed offspring showed an altered response in splenocyte proliferation assay when challenged to lipopolysaccharide, concanavalin-A, AgNPs, or silver ions. Perinatal AgNPs exposure affected metabolic parameters (resistin, glucagon-like peptide-1, leptin, insulin) and upregulated JNK/P38/ERK signaling in the pancreas. We observed pancreatic damage, reduced insulin level, and increased blood glucose levels. Further, we observed renal damage, particularly to tubular and glomerular regions as indicated by histopathology and electron microscopy. Our study thus shows that only perinatal exposure to AgNPs could induce persistent inflammation, alter immune responses against foreign antigens and metabolism which may contribute to pancreatic and renal damage later in life.

Metallic nanoparticles as drug delivery system for the treatment of cancer

INTRODUCTION

The targeted delivery of anticancer agents to tumor is a major challenge because most of the drugs show off-target effect resulting in nonspecific cell death. Multifunctionalized metallic nanoparticles (NPs) are explored as new carrier system in the era of cancer therapeutics. Researchers investigated the potential of metallic NPs to target tumor cells by active and passive mechanisms, thereby reducing off-target effects of anticancer agents. Moreover, photocatalytic activity of upconversion nanoparticles (UCNPs) and the enhanced permeation and retention (EPR) effect have also gained wide potential in cancer treatment. Recent advancement in the field of nanotechnology highlights their potency for cancer therapy.

AREAS COVERED

This review summarizes the types of gold and silver metallic NPs with targeting mechanisms and their potentiality in cancer therapy.

EXPERT OPINION

Recent advances in the field of nanotechnology for cancer therapy offer high specificity and targeting efficiency. Targeting tumor cells through mechanistic pathways using metallic NPs for the disruption/alteration of molecular profile and survival rate of the tumor cells has led to an effective approach for cancer therapeutics. This alteration in the survival rate of the tumor cells might decrease the proliferation thereby resulting in more efficient management in the treatment of cancer.

Applications of Silver Nanoparticles in Dentistry: Advances and Technological Innovation

Silver nanoparticles (AgNPs) have been successfully applied in several areas due to their significant antimicrobial activity against several microorganisms. In dentistry, AgNP can be applied in disinfection, prophylaxis, and prevention of infections in the oral cavity. In this work, the use of silver nanoparticles in dentistry and associated technological innovations was analyzed. The scientific literature was searched using PubMed and Scopus databases with descriptors related to the use of silver nanoparticles in dentistry, resulting in 90 open-access articles. The search for patents was restricted to the A61K code (International Patent Classification), using the same descriptors, resulting in 206 patents. The results found were ordered by dental specialties and demonstrated the incorporation of AgNPs in different areas of dentistry. In this context, the search for patents reaffirmed the growth of this technology and the dominance of the USA pharmaceutical industry over AgNPs product development. It could be concluded that nanotechnology is a promising area in dentistry with several applications.

Cirrhotic Liver of Liver Transplant Recipients Accumulate Silver and Co-Accumulate Copper

Silver-based materials are widely used in clinical medicine. Furthermore, the usage of silver containing materials and devices is widely recommended and clinically approved. The impact on human health of the increasing use of silver nanoparticles in medical devices remains understudied, even though Ag-containing dressings are known to release silver into the bloodstream. In this study, we detected a widespread and sometimes significant silver accumulation both in healthy and sick liver biopsies, levels being statistically higher in patients with various hepatic pathologies. 28 healthy and 44 cirrhotic liver samples were investigated. The median amount of 0.049 ppm Ag in livers was measured in cirrhotic livers while the median was 0.0016 ppm for healthy livers (a more than 30-fold difference). The mean tissue concentrations of essential metals, Fe and Zn in cirrhotic livers did not differ substantially from healthy livers, while Cu was positively correlated with Ag. The serum levels of gamma-glutamyl transpeptidase (GGTP) was also positively correlated with Ag in cirrhotic livers. The increased Ag accumulation in cirrhotic livers could be a side effect of wide application of silver in clinical settings. As recent studies indicated a significant toxicity of silver nanoparticles for human cells, the above observation could be of high importance for the public health.

Biodistribution and pulmonary metabolic effects of silver nanoparticles in mice following acute intratracheal instillations

The respiratory tract is the route of entry for accidentally inhaled AgNPs, which can reach the lungs and redistribute to other main organs through systemic circulation. In the present work, we aimed to evaluate silver biodistribution and biological effects after 1 or 2 intratracheal instillations (IT) of two differently sized PVP-coated AgNPs (5 and 50 nm-3 mg/kg) and ionic silver (AgNO₃-1 mg/kg bw) in mice. Furthermore, nuclear magnetic resonance (NMR) metabolomics was applied to unveil pulmonary metabolic variations. Animals exposed to 5 nm AgNP (AgNP5) showed higher levels of ionic silver in organs, especially in the lung, spleen, kidney and liver, while animals exposed to 50 nm AgNP (AgNP50) showed higher levels of silver in the blood. Animals exposed to AgNP50 excreted higher amounts of silver than those exposed to AgNP5, which is consistent with higher tissue accumulation of silver in animals exposed to the latter. Lung metabolic profiling revealed several Ag-induced alterations in metabolites involved in different pathways, such as glycolysis and tricarboxylic acid (TCA) cycle, amino acid and phospholipid metabolism, and antioxidant defense. Notably, most of the metabolic changes observed after 1 IT were absent in animals subjected to 2 IT of AgNO₃, or reversed for AgNPs, suggesting adaptation mechanisms to cope with the initial insult and recover homeostasis. Graphical abstract.

Silver nanoparticles-induced nephrotoxicity in rats: the protective role of red beetroot (Beta vulgaris) juice

The present study was designed to investigate the nephrotoxicity of silver nanoparticles (AgNPs; 80 mg/kg; > 100 nm) and to evaluate the protective effect exercised by Beta vulgaris (beetroot) juice (RBR; 200 mg/kg) on male rats' kidney. Serum-specific parameters (urea, creatinine, electrolytes and histopathology of kidney tissue) were examined to assess the AgNPs nephrotoxicity effect. Moreover, this study analysed oxidative stress (lipid peroxidation, glutathione, superoxide dismutase and catalase) and anti-apoptotic markers (Bcl-2). AgNPs intoxication increased kidney function marker levels and lipid peroxidation and decreased the glutathione, superoxide dismutase and catalase activities in kidney tissue. Additionally, Bcl-2 expression was downregulated following AgNPs intoxication. Moreover, AgNPs induced a significant increase in renal DNA damage displayed as an elevation in tail length, tail DNA percentage and tail moment. Interestingly, RBR post-treatment restored the biochemical and histological alterations induced by AgNPs exposure, reflecting its nephroprotective effect. Collectively, the present data suggest that RBR could be used as a potential therapeutic intervention to prevent AgNPs-induced nephrotoxicity.

Acute reproductive toxicology after intratesticular injection of silver nanoparticles (AgNPs) in Wistar rats

This study aimed to evaluate the effects of an intratesticular injection of silver nanoparticles (AgNPs) on reproductive parameters and health of rats, and to evaluate the AgNPs biodistribution in order to develop a nanotechnological contraceptive agent for male animals. Treated animals received 220 μL of AgNPs solution (0.46 µg-Ag/ml) in each testicle and were euthanized: seven, 14, 28, and 56 days after injection. A significant decrease (p < 0.05) in the percentage of motile sperm in D7 (8.8%) was observed, comparing to the control (73.3%), D14 (86.0%), D28 (68.2%), and D56 (90.0%) groups. D7 group also presented a decrease (p < 0.05) in the percentage of normal spermatozoa. Additionally, D7 group showed an increase (p < 0.05) in abnormal midpiece and sperm head morphology compared to the Control group. Seminiferous tubules presented all germline cell types and spermatozoa for all groups. However, D7 group did not present spermatozoa in the epididymis, whereas some spermatozoa and cellular debris were visible in D14 and D28 groups. All animals presented hematological parameters, creatinine, and alanine aminotransferase values within the normal limits for Wistar rats. The percentage of silver found in the liver was always higher than in the other organs analyzed. A pioneering mathematical model is proposed, from which the half-life time of silver in the liver (17 days), spleen (23 days), lungs (30 days), and kidneys (35 days) was extracted. In conclusion, some acute and severe toxic effects were observed in sperm cells following intratesticular injection of AgNPs, although these effects were reversible. No adverse effects to general animal health were observed.

Multigenerational Exposures of Daphnia Magna to Pristine and Aged Silver Nanoparticles: Epigenetic Changes and Phenotypical Ageing Related Effects

Engineered nanoparticles (NPs) undergo physical, chemical, and biological transformation after environmental release, resulting in different properties of the "aged" versus "pristine" forms. While many studies have investigated the ecotoxicological effects of silver (Ag) NPs, the majority focus on "pristine" Ag NPs in simple exposure media, rather than investigating realistic environmental exposure scenarios with transformed NPs. Here, the effects of "pristine" and "aged" Ag NPs are systematically evaluated with different surface coatings on Daphnia magna over four generations, comparing continuous exposure versus parental only exposure to assess recovery potential for three generations. Biological endpoints including survival, growth and reproduction and genetic effects associated with Ag NP exposure are investigated. Parental exposure to "pristine" Ag NPs has an inhibitory effect on reproduction, inducing expression of antioxidant stress related genes and reducing survival. Pristine Ag NPs also induce morphological changes including tail losses and lipid accumulation associated with aging phenotypes in the heart, abdomen, and abdominal claw. These effects are epigenetic remaining two generations post-maternal exposure (F2 and F3). Exposure to identical Ag NPs (same concentrations) aged for 6 months in environmentally realistic water containing natural organic matter shows considerably reduced toxicological effects in continuously exposed generations and to the recovery generations.

Green Chemistry Synthesis of Silver Nanoparticles and Their Potential Anticancer Effects

Nanobiotechnology has grown rapidly and become an integral part of modern disease diagnosis and treatment. Biosynthesized silver nanoparticles (AgNPs) are a class of eco-friendly, cost-effective and biocompatible agents that have attracted attention for their possible biomedical and bioengineering applications. Like many other inorganic and organic nanoparticles, such as AuNPs, iron oxide and quantum dots, AgNPs have also been widely studied as components of advanced anticancer agents in order to better manage cancer in the clinic. AgNPs are typically produced by the action of reducing reagents on silver ions. In addition to numerous laboratory-based methods for reduction of silver ions, living organisms and natural products can be effective and superior source for synthesis of AgNPs precursors. Currently, plants, bacteria and fungi can afford biogenic AgNPs precursors with diverse geometries and surface properties. In this review, we summarized the recent progress and achievements in biogenic AgNPs synthesis and their potential uses as anticancer agents.

Silver nanoparticle immunomodulatory potential in absence of direct cytotoxicity in RAW 264.7 macrophages and MPRO 2.1 neutrophils

Engineered nanomaterials (ENM) are being used in a wide range of consumer products and pharmaceuticals; hence, there is an increasing risk for human exposure and potential adverse outcomes. The immune system, vital in host defense and protection against environmental agents, is typically initiated and executed by innate effector immune cells including macrophages and neutrophils. Previous literature has reported the immune system as a major target of ENM toxicity; however, there is inconsistency regarding the immunotoxicity of ENM. This could be attributed to differences in ENM physicochemical properties, cellular models examined, biocorona formation, etc. Thus, the current study examined the toxicity and immunomodulatory effects of silver nanoparticles (AgNP), one of the most utilized ENM in consumer and medical products, in two key innate immune cell models, e.g. RAW 264.7 cells (macrophages) and differentiated MPRO 2.1 cells (promyelocytes/neutrophils). The results showed that despite a generation of reactive oxygen species, exposure to 20 nm citrate-coated AgNP was not associated with major oxidative damage, inflammatory responses, nor cytotoxicity. Nevertheless, and most importantly, pre-exposure to the AgNP for 24 h enhanced RAW 264.7 cell phagocytic ability as well as the release of inflammatory cytokine interleukin-6 in response to lipopolysaccharide (LPS). In MPRO 2.1 cells, AgNP pre-exposure also resulted in enhanced phagocytic ability; however, these cells manifest reduced cell degranulation (elastase release) and oxidative burst in response to phorbol myristate acetate (PMA). Taken together, these findings indicated to us that exposure to AgNP, despite not being directly (cyto)toxic to these cells, had the potential to alter immune cell responses. The findings underscore the import of assessing immune cell function post-exposure to ENM beyond the standard endpoints such as oxidative stress and cytotoxicity. In addition, these findings further illustrate the importance of understanding the underlying molecular mechanisms of ENM-cellular interactions, particularly in the immune system.

Growth, serum biochemical, and histopathological responses of broilers administered with silver nanoparticles as a drinking water disinfectant

The supplementation of 50 ppm dosed silver nanoparticles (AgNPs) as a disinfectant in broilers drinking water was investigated to examine their growth performance, blood serum biochemistry, and organ histology in the case group, compared to the control. The growth performance parameters, such as water intake, feed intake, and body weight were recorded 6 times, each in an interval of 7 days, over a period of 42 days. At the end of each 42 days, the blood and major organs of the 1 case boiler out of 75 and 1 control broiler out of 75 were collected in random. The procedure was repeated 3 sets one after another, each consisting 42 day intervening period. The liver enzyme, lipid profile, glucose level, organ histology, and concentration of AgNPs in liver, spleen, heart, and small intestine were determined. The obtained results show that the growth performance of the case broilers was significantly higher than the control section (p < 0.05). However, in all the three sets the changes in lipid profile, liver enzyme, and glucose level of the case broilers were not statistically significantly different compared to the control (p > 0.05). The histology of liver, kidney, heart, spleen, and small intestine of broilers has not shown any damages to the cells as compared to the control samples. In the case samples, the highest concentration of AgNPs was observed in the small intestine (5.44 µg/g) followed by liver (4.32 µg/g), kidney (3.94 µg/g), heart (3.82 µg/g), and spleen (3.49 µg/g). The present study concludes that the administering 50 ppm AgNPs of average 15 nm size in the poultry drinking water was found safe for consumption as well as for growth enhancing, due to better bird comfort.

Rapid Intestinal Uptake and Targeted Delivery to the Liver Endothelium Using Orally Administered Silver Sulfide Quantum Dots

Quantum dots (QDs) are used for imaging and transport of therapeutics. Here we demonstrate rapid absorption across the small intestine and targeted delivery of QDs with bound materials to the liver sinusoidal endothelial cells (LSECs) or hepatocytes in vitro and in vivo following oral administration. QDs were radiolabeled with ³H-oleic acid, with a fluorescent tag or ¹⁴C-metformin placed within a drug binding site. Three different biopolymer shell coatings were compared (formaldehyde-treated serum albumin (FSA), gelatin, heparin). Passage across the small intestine into mesenteric veins is mediated by clathrin endocytosis and micropinocytosis. 60% of an oral dose of QDs was rapidly distributed to the liver within 30 min, and this increased to 85% with FSA biopolymer coating. Uptake into LSECs also increased 3-fold with FSA coating, while uptake into hepatocytes was increased from 40% to 85% with gelatin biopolymer coating. Localization of QDs to LSECs was confirmed with immunofluorescence and transmission electron microscopy. 85% of QDs were cleared within 24 h of administration. The bioavailability of ¹⁴C-metformin 2 h post-ingestion was increased 5-fold by conjugation with QD-FSA, while uptake of metformin into LSECs was improved 50-fold by using these QDs. Endocytosis of QDs by SK-Hep1 cells (an LSEC immortal cell line) was via clathrin- and caveolae-mediated pathways with QDs taken up into lysosomes. In conclusion, we have shown high specificity targeting of the LSEC or hepatocytes after oral administration of QDs coated with a biopolymer layer of FSA or gelatin, which improved the bioavailability and delivery of metformin to LSECs.

Surface coatings alter transcriptional responses to silver nanoparticles following oral exposure

Silver nanoparticles (AgNPs) are used in food packaging materials, dental care products and other consumer goods and can result in oral exposure. To determine whether AgNP coatings modulate transcriptional responses to AgNP exposure, we exposed mice orally to 20 nm citrate (cit)-coated AgNPs (cit-AgNPs) or polyvinylpyrrolidone (PVP)-coated AgNPs (PVP-AgNPs) at a 4 mg/kg dose for 7 consecutive days and analyzed changes in the expression of protein-coding genes and long noncoding RNAs (lncRNAs), a new class of regulatory RNAs, in the liver. We identified unique and common expression signatures of protein-coding and lncRNA genes, altered biological processes and signaling pathways, and coding-non-coding gene interactions for cit-AgNPs and PVP-AgNPs. Commonly regulated genes comprised only about 10 and 20 percent of all differentially expressed genes in PVP-AgNP and cit-AgNP exposed mice, respectively. Commonly regulated biological processes included glutathione metabolic process and cellular oxidant detoxification. Commonly regulated pathways included Keap-Nrf2, PPAR, MAPK and IL-6 signaling pathways. The coding-non-coding gene co-expression analysis revealed that protein-coding genes were co-expressed with a variable number of lncRNAs ranging from one to twenty three and may share functional roles with the protein-coding genes. PVP-AgNP exposure induced a more robust transcriptional response than cit-AgNP exposure characterized by more than two-fold higher number of differentially expressed both protein- coding and lncRNA genes. Our data demonstrate that the surface coating strongly modulates the spectrum and the number of differentially expressed genes after oral AgNP exposure. On the other hand, our data suggest that AgNP exposure can alter drug and chemical sensitivity, metabolic homeostasis and cancer risk irrespective of the coating type, warranting further investigations.

Meta-Analysis of Pharmacokinetic Studies of Nanobiomaterials for the Prediction of Excretion Depending on Particle Characteristics

The growth in development and use of nanobiomaterials (NBMs) has raised questions regarding their possible distribution in the environment. Because most NBMs are not yet available on the market and exposure monitoring is thus not possible, prospective exposure modeling is the method of choice to get information on their future environmental exposure. An important input for such models is the fraction of the NBM excreted after their application to humans. The aim of this study was to analyze the current literature on excretion of NBMs using a meta-analysis. Published pharmacokinetic data from in vivo animal experiments was collected and compiled in a database, including information on the material characteristics. An evaluation of the data showed that there is no correlation between the excretion (in % of injected dose, ID) and the material type, the dose, the zeta potential or the size of the particles. However, the excretion is dependent on the type of administration with orally administered NBMs being excreted to a larger extent than intravenously administered ones. A statistically significant difference was found for IV vs. oral and oral vs. inhalation. The database provided by this work can be used for future studies to parameterize the transfer of NBMs from humans to wastewater. Generic probability distributions of excretion for oral and IV-administration are provided to enable excretion modeling of NBMs without data for a specific NBM.

Tissue Distribution of Radiolabeled 110mAg Nanoparticles in Fish: Arctic Charr (Salvelinus alpinus)

This study presents the first whole-body tissue distributions of dissolved (Ag_I) and 20 nm silver nanoparticles (Ag₀NPs₂₀) in fish (Arctic charr, Salvelinus alpinus). The distributions are provided for fish exposed to three different treatments: (i) intravenous (IV), (ii) dietary, and (iii) waterborne. Quantitative whole-body autoradiography (QWBA) analyses obtained on high-resolution images reveal distinct silver distribution patterns according to the treatments. The IV exposures showed that AgNPs₂₀ were mainly located in bile and kidney after 8 d, while Ag_I was distributed through the whole body and reached particular tissues such as bones, eyes, skin, liver, spleen, kidney, and intestine. The Ag₀NPs₂₀ distribution with the dietary exposures suggests that some dissolution occurred within fish organs. We propose that dissolved silver could later precipitate as chloride, sulfide, or selenide and be incorporated in bones during the growth. Consequently, it is yet difficult to state if Ag₀NPs₂₀ cross biological barriers. Finally, the waterborne exposures revealed that the gills can capture Ag₀NPs₂₀, but in small quantities. This suggests that the stability of Ag₀NPs₂₀ in water is critical for the uptake via the gills.

Anti-Methicillin-Resistant Staphylococcus aureus Nanoantibiotics

Nanoparticle-based antibiotic constructs have become a popular area of investigation in the biomedical sciences. Much of this work has pertained to human diseases, largely in the cancer therapy arena. However, considerable research has also been devoted to the nanochemistry for controlling infectious diseases. Among these are ones due to bacterial infections, which can cause serious illnesses leading to death. The onset of multi-drug-resistant (MDR) infections such as those caused by the human pathogen Staphylococcus aureus has created a dearth of problems such as surgical complications, persistent infections, and lack of available treatments. In this article, we set out to review the primary literature on the design and development of new nanoparticle materials for the potential treatment of S. aureus infections, and areas that could be further expanded upon to make nanoparticle antibiotics a mainstay in clinical settings.

Nanoantibiotics: A Novel Rational Approach to Antibiotic Resistant Infections

Background:

The main drawbacks for using conventional antimicrobial agents are the development of multiple drug resistance due to the use of high concentrations of antibiotics for extended periods. This vicious cycle often generates complications of persistent infections, and intolerable antibiotic toxicity. The problem is that while all new discovered antimicrobials are effective and promising, they remain as only short-term solutions to the overall challenge of drug-resistant bacteria.

Objective:

Recently, nanoantibiotics (nAbts) have been of tremendous interest in overcoming the drug resistance developed by several pathogenic microorganisms against most of the commonly used antibiotics. Compared with free antibiotic at the same concentration, drug delivered via a nanoparticle carrier has a much more prominent inhibitory effect on bacterial growth, and drug toxicity, along with prolonged drug release. Additionally, multiple drugs or antimicrobials can be packaged within the same smart polymer which can be designed with stimuli-responsive linkers. These stimuli-responsive nAbts open up the possibility of creating multipurpose and targeted antimicrobials. Biofilm formation still remains the leading cause of conventional antibiotic treatment failure. In contrast to conventional antibiotics nAbts easily penetrate into the biofilm, and selectively target biofilm matrix constituents through the introduction of bacteria specific ligands. In this context, various nanoparticles can be stabilized and functionalized with conventional antibiotics. These composites have a largely enhanced bactericidal efficiency compared to the free antibiotic.

Conclusion:

Nanoparticle-based carriers deliver antibiotics with better biofilm penetration and lower toxicity, thus combating bacterial resistance. However, the successful adaptation of nanoformulations to clinical practice involves a detailed assessment of their safety profiles and potential immunotoxicity.

Toxicity and safety study of silver and gold nanoparticles functionalized with cysteine and glutathione

This study was designed to evaluate the nano-bio interactions between endogenous biothiols (cysteine and glutathione) with biomedically relevant, metallic nanoparticles (silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs)), in order to assess the biocompatibility and fate of nanoparticles in biological systems. A systematic and comprehensive analysis revealed that the preparation of AgNPs and AuNPs in the presence of biothiols leads to nanoparticles stabilized with oxidized forms of biothiols. Their safety was tested by evaluation of cell viability, reactive oxygen species (ROS) production, apoptosis induction and DNA damage in murine fibroblast cells (L929), while ecotoxicity was tested using the aquatic model organism Daphnia magna. The toxicity of these nanoparticles was considerably lower compared to their ionic metal forms (i.e., Ag+ and Au3+). The comparison with data published on polymer-coated nanoparticles evidenced that surface modification with biothiols made them safer for the biological environment. In vitro evaluation on human cells demonstrated that the toxicity of AgNPs and AuNPs prepared in the presence of cysteine was similar to the polymer-based nanoparticles with the same core material, while the use of glutathione for nanoparticle stabilization was considerably less toxic. These results represent a significant contribution to understanding the role of biothiols on the fate and behavior of metal-based nanomaterials.

Emerging investigator series: characterization of silver and silver nanoparticle interactions with zinc finger peptides

In biological systems, chemical and physical transformations of engineered silver nanomaterials (AgENMs) are mediated, in part, by proteins and other biomolecules. Metalloprotein interactions with AgENMs are also central in understanding toxicity and antimicrobial and resistance mechanisms. Despite their readily available thiolate and amine ligands, zinc finger (ZF) peptides have thus far escaped study in reaction with AgENMs and their Ag(I) oxidative dissolution product. We report spectroscopic studies that characterize AgENM and Ag(I) interactions with two ZF peptides that differ in sequence, but not in metal binding ligands: the ZF consensus peptide CP-CCHC and the C-terminal zinc finger domain of HIV-1 nucleocapsid protein p7 (NCp7_C). Both ZF peptides catalyze AgENM (10 and 40 nm, citrate coated) dissolution and agglomeration, two important AgENM transformations that impact bioreactivity. AgENMs and their oxidative dissolution product, Ag(I)(aq), mediate changes to ZF peptide structure and metalation as well. Spectroscopic titrations of Ag(I) into apo-ZF peptides show an Ag(I)-thiolate charge transfer band, indicative of Ag(I)-ZF binding. Fluorescence studies of the Zn(II)-NCp_7 complex indicate that the Ag(I) also effectively competes with the Zn(II) to drive Zn(II) displacement from the ZFs. Upon interaction with AgENMs, Zn(II) bound ZF peptides show a secondary structural change in circular dichroism spectroscopy toward an apo-like structure. The results suggest that Ag(I) and AgENMs may alter ZF protein function within the cell.

Silver nanoparticles promote procoagulant activity of red blood cells: a potential risk of thrombosis in susceptible population

Background

Silver nanoparticles (AgNP) are widely used in medical practices owing to their distinct antibacterial, antiviral and anticancer activities. However, with increasing use of AgNP, concerns over its potential toxicity are also escalating. Here, we demonstrated the potential thrombotic effect of AgNP which was mediated by the procoagulant activity of red blood cells (RBCs).

Results

In freshly isolated human RBCs, AgNP, but not silver microparticles (AgMP), elicited morphological changes, phosphatidylserine (PS) exposure and microvesicles (MV) generation, the key indicators of procoagulant activity in RBCs at concentration ranges (≤ 100 μg/mL) that were free of significant hemolysis. In line with this, AgNP potentiated thrombin generation and adherence of RBCs to endothelial cells, while AgMP did not. Oxidative stress, intracellular calcium increase and ATP depletion were found to underlie the procoagulant effects of AgNP, which led to altered activity of membrane aminophospholipid translocases. These in vitro findings were well reproduced in rat in vivo, where intravenously exposure to AgNP promoted venous thrombosis significantly. Of note, RBCs isolated from cancer patients, who inherently convey the risk of thrombogenesis, were more sensitive to the procoagulant effects of AgNP. In addition, AgNP significantly potentiated the procoagulant effects of a chemotherapeutic drug, paclitaxel.

Conclusion

Collectively, these results suggest that AgNP may have prothrombotic risks by promoting procoagulant activity of RBCs and caution shall be taken for its use in the population sensitive to thrombosis like cancer patients.

Electronic supplementary material

The online version of this article (10.1186/s12989-019-0292-6) contains supplementary material, which is available to authorized users.

Assessment of in vivo genotoxicity of citrated-coated silver nanoparticles via transcriptomic analysis of rabbit liver tissue

Background

Silver nanoparticles (AgNPs) are widely used in industrial and household applications, arousing concern regarding their safety in humans. The risks posed by stabilizer-coated AgNPs continue to be unclear, and assessing their toxicity is for an understanding of the safety issues involved in their use in various applications.

Purpose

We aimed to investigated the long-term toxicity of citrate-coated silver nanoparticles (cAgNPs) in liver tissue using several toxicity tests and transcriptomic analysis at 7 and 28 days after a single intravenous injection into rabbit ear veins (n=4).

Materials and methods

The cAgNPs used in this study were in the form of a 20% (w/v) aqueous solution, and their size was 7.9±0.95 nm, measured using transmission electron microscopy. The animal experiments were performed based on the principles of good laboratory practice.

Results

Our results showed that the structure and function of liver tissue were disrupted due to a single exposure to cAgNPs. In addition, in vivo comet assay showed unrepaired genotoxicity in liver tissue until 4 weeks after a single injection, suggesting a potential carcinogenic effect of cAgNPs. In our transcriptomic analysis, a total of 244 genes were found to have differential expression at 28 days after a single cAgNP injection. Carefully curated pathway analysis of these genes using Pathway Studio and Ingenuity Pathway Analysis tools revealed major molecular networks responding to cAgNP exposure and indicated a high correlation of the genes with inflammation, hepatotoxicity, and cancer. Molecular validation suggested potential biomarkers for assessing the toxicity of accumulated cAgNPs.

Conclusion

Our investigation highlights the risk associated with a single cAgNP exposure with unrepaired damage persisting for at least a month.

Oral bioaccessibility of silver nanoparticles and ions in natural soils: Importance of soil properties

The abundance of silver nanoparticles (AgNPs) in consumer products has led to their environmental release and therefore to concern about their impact on human health. The ingestion of AgNP-contaminated soil from urban sites is an important exposure pathway, especially for children. Given the limited information on oral bioaccessibility of soil Ag, we used a physiologically based extraction test (PBET) to evaluate the bioaccessibility of AgNPs and AgNO₃ from soil digestion. The AgNPs underwent several biochemical transformations, including their simultaneous dissolution and agglomeration in gastric fluid followed by the disintegration in the intestinal fluid of the agglomerates into NPs containing silver and chlorine. Therefore, Ag-containing soil exposed the intestine to nanoparticulate Ag in forms that were structurally different from the original forms. The bioaccessibility of AgNPs (0.5 ± 0.05%-10.9 ± 0.7%) was significantly lower than that of AgNO₃ (4.7 ± 0.6%-14.4 ± 0.1%), as a result of the lower adsorption of nanoparticles to soil residues during the digestive process. For the soils tested, the bioaccessibility of AgNPs increased with decreasing clay contents and lower pH. By identifying the soil properties that control AgNP bioaccessibility, a more efficient and accurate screening can be performed of soil types that pose the greatest health risk associated with AgNP exposure.

Toxicity and tissue distribution of cerium oxide nanoparticles in rats by two different routes: single intravenous injection and single oral administration

Toxicity and target organ distribution of cerium oxide nanoparticles (CeNPs) were investigated via single intravenous injection and single oral administration, respectively. Rats were sacrificed at 24 h after treatment with doses of 30 and 300 mg/kg, and cerium concentrations were measured in liver, kidney, spleen, lung, blood, urine and feces. Results revealed cerium levels in blood and tissues were considerably low in oral treated groups and most cerium was detected in feces, meaning CeNPs would not be absorbed in the gastro-intestinal system. Conversely, high concentrations of cerium were detected in all tissues of rats after intravenous injection. Liver and spleen were main target organs. Cerium levels in liver were 594.9 ± 95.3 μg/g tissue in 30 mg/kg treat group and 3741.7 ± 932.7 μg/g tissue in 300 mg/kg treat group. Cerium levels in spleen reached almost levels of liver. Cerium was also detected, that is relatively low compared to oral administration, in feces of rats treated via intravenous injection, that supports biliary excretion of CeNPs. Urine excretion of CeNPs was not detected in oral treatment and intravenous injection. In accordance with level of cerium distribution, toxicities based on hematology, serum biochemistry and histopathology were observed in rats treated by intravenous injection while no significance was revealed in orally treated groups.

Effect of nanoparticles of silver on redox status and the accumulation of Ag in chicken tissues

BACKGROUND

The aim of the study was to verify the hypothesis that there are doses of silver nanoparticles (Ag-NPs) that improve antioxidant defence in chickens without compromising their growth performance and health.

RESULTS

The results of our study suggest that, irrespective of the concentration, the administration of Ag-NPs (5 nm) at a dose not exceeding 54 mg/bird has no negative effect on the growth performance of chickens. The administration of Ag-NPs (5 nm) in the amount of 2.87 to 63.74 mg/bird does not cause silver to accumulate in the breast muscle. The ingestion of 2.87 mg/bird was found to result in the accumulation of this element in the wall of the small intestine and in the liver, and a further increase in the dose increases the accumulation of Ag in these tissues. Accumulation of Ag in the heart of the chickens was not observed until the dose reached 22.5 mg/bird.

CONCLUSION

Our research has shown that the application of Ag-NPs (5 nm), especially at doses greater than the 'no observable adverse effect level' (NOAEL) of 9.47 mg/bird, can induce oxidative reactions in the blood, small intestinal wall, liver and breast muscle of chickens. © 2018 Society of Chemical Industry.