Acute pulmonary toxicity and body distribution of inhaled metallic silver nanoparticles

Silver nanoparticle-based drug delivery systems in the fight against COVID-19: enhancing efficacy, reducing toxicity and improving drug bioavailability

Nanoparticles (NPs) have played a pivotal role in various biomedical applications, spanning from sensing to drug delivery, imaging and anti-viral therapy. The therapeutic utilisation of NPs in clinical trials was established in the early 1990s. Silver nanoparticles (AgNPs) possess anti-microbial, anti-cancer and anti-viral properties, which make them a possible anti-viral drug to combat the COVID-19 virus. Free radicals and reactive oxygen species are produced by AgNPs, which causes apoptosis induction and prevents viral contamination. The shape and size of AgNPs can influence their interactions and biological activities. Therefore, it is recommended that silver nanoparticles (AgNPs) be used as a valuable tool in the management of COVID-19 pandemic. These nanoparticles possess strong anti-microbial properties, allowing them to penetrate and destroy microbial cells. Additionally, the toxicity level of nanoparticles depends on the administered dose, and surface modifications are necessary to reduce toxicity, preventing direct interaction between metal surfaces and cells. By utilising silver nanoparticles, drugs can be targeted to specific areas in the body. For example, in the case of COVID-19, anti-viral drugs can be stimulated as nanoparticles in the lungs to accelerate disease recovery. Nanoparticle-based systems have the capability to transport drugs and treat specific body parts. This review offers an examination of silver nanoparticle-based drug delivery systems for combatting COVID-19, with the objective of boosting the bioavailability of existing medications, decreasing their toxicity and raising their efficiency.

Toxicity dose descriptors from animal inhalation studies of 13 nanomaterials and their bulk and ionic counterparts and variation with primary particle characteristics

This study collects toxicity data from animal inhalation studies of some nanomaterials and their bulk and ionic counterparts. To allow potential grouping and interpretations, we retrieved the primary physicochemical and exposure data to the extent possible for each of the materials. Reviewed materials are compounds (mainly elements, oxides and salts) of carbon (carbon black, carbon nanotubes, and graphene), silver, cerium, cobalt, copper, iron, nickel, silicium (amorphous silica and quartz), titanium (titanium dioxide), and zinc (chemical symbols: Ag, C, Ce, Co, Cu, Fe, Ni, Si, Ti, TiO₂, and Zn). Collected endpoints are: a) pulmonary inflammation, measured as neutrophils in bronchoalveolar lavage (BAL) fluid at 0-24 hours after last exposure; and b) genotoxicity/carcinogenicity. We present the dose descriptors no-observed-adverse-effect concentrations (NOAECs) and lowest-observed-adverse-effect concentrations (LOAECs) for 88 nanomaterial investigations in data-library and graph formats. We also calculate 'the value where 25% of exposed animals develop tumors' (T25) for carcinogenicity studies. We describe how the data may be used for hazard assessment of the materials using carbon black as an example. The collected data also enable hazard comparison between different materials. An important observation for poorly soluble particles is that the NOAEC for neutrophil numbers in general lies around 1 to 2 mg/m³. We further discuss why some materials' dose descriptors deviate from this level, likely reflecting the effects of the ionic form and effects of the fiber-shape. Finally, we discuss that long-term studies, in general, provide the lowest dose descriptors, and dose descriptors are positively correlated with particle size for near-spherical materials.

Silver Nanoparticles as Potential Antiviral Agents

Since the early 1990s, nanotechnology has led to new horizons in nanomedicine, which encompasses all spheres of science including chemistry, material science, biology, and biotechnology. Emerging viral infections are creating severe hazards to public health worldwide, recently, COVID-19 has caused mass human casualties with significant economic impacts. Interestingly, silver nanoparticles (AgNPs) exhibited the potential to destroy viruses, bacteria, and fungi using various methods. However, developing safe and effective antiviral drugs is challenging, as viruses use host cells for replication. Designing drugs that do not harm host cells while targeting viruses is complicated. In recent years, the impact of AgNPs on viruses has been evaluated. Here, we discuss the potential role of silver nanoparticles as antiviral agents. In this review, we focus on the properties of AgNPs such as their characterization methods, antiviral activity, mechanisms, applications, and toxicity.

Kinetics of Silver Accumulation in Tissues of Laboratory Mice after Long-Term Oral Administration of Silver Nanoparticles

Since ancient times, silver has been known for its pronounced bactericidal, antiviral and fungicidal properties. Currently, nanoparticles of this metal are widely used in the food, light and pharmaceutical industries, as well as in medicine. Silver in any form can have a toxic effect not only on pathogens, but also on healthy cells. The biological activity and bioavailability of silver preparations depend on the degree of their solubility in water. In addition, the maximum permissible concentration of soluble forms of silver is an order of magnitude lower than that of insoluble forms. This makes nanoparticles of silver with a hydrophilic coating that form stable colloidal solutions in aqueous media potentially unsafe objects. In this work, we studied the kinetics of the accumulation of silver nanoparticles with an average size of 34 ± 5 nm stabilized with polyvinylpyrrolidone in the organs of laboratory C57Bl/6 mice. The administration of nanoparticles was carried out orally for 30, 60, 120 and 180 days at the dose of 50 µg/day/animal. All the mice developed and gained weight normally during the experiment. No adverse effects were observed. Determination of the silver content in biological tissues of mammals was accomplished by neutron activation analysis. The masses and concentrations of silver in the brain and its different sections (hippocampus, cerebellum, cortex and remnants), as well as in the lungs, testes, liver, blood, kidneys, spleen and heart, were determined. The injection times at which the accumulation curves reached saturation were established. An extremely high accumulation of silver in the testes was shown at 120 days of administration, and a significant accumulation of silver in the lungs and brain was observed. The accumulation of silver in all parts of the brain except the cortex was significant, and its trend was similar to that in the whole brain.

Silver Nanoparticles Biosynthesis, Characterization, Antimicrobial Activities, Applications, Cytotoxicity and Safety Issues: An Updated Review

Rapid advances in nanotechnology have led to its emergence as a tool for the development of green synthesized noble metal nanoparticles, especially silver nanoparticles (AgNPs), for applications in diverse fields such as human health, the environment and industry. The importance of AgNPs is because of their unique physicochemical and antimicrobial properties, with a myriad of activities that are applicable in various fields, including the pharmaceutical industry. Countries with high biodiversity require the collection and transformation of information about biological assets into processes, associations, methods and tools that must be combined with the sustainable utilization of biological diversity. Therefore, this review paper discusses the applicable studies of the biosynthesis of AgNPs and their antimicrobial activities towards microorganisms in different areas viz. medicine and agriculture. The confirmed antiviral properties of AgNPs promote their applicability for SARS-CoV-2 treatment, based on assimilating the virus’ activities with those of similar viruses via in vivo studies. In this review, an insight into the cytotoxicity and safety issues of AgNPs, along with their future prospects, is also provided.

Silver nanoparticles as a potential treatment against SARS-CoV-2: A review

Several human coronaviruses (HCoVs) are distinguished by the ability to generate epidemics or pandemics, with their corresponding diseases characterized by severe respiratory illness, such as that which occurs in severe acute respiratory syndrome (SARS-CoV), Middle East respiratory syndrome (MERS-CoV), and, today, in SARS-CoV-2, an outbreak that has struck explosively and uncontrollably beginning in December 2019 and has claimed the lives of more than 1.9 M people worldwide as of January 2021. The development of vaccines has taken one year, which is why it is necessary to investigate whether some already-existing alternatives that have been successfully developed in recent years can mitigate the pandemic's advance. Silver nanoparticles (AgNPs) have proved effective in antiviral action. Thus, in this review, several in vitro and in vivo studies of the effect of AgNPs on viruses that cause respiratory diseases are analyzed and discussed to promote an understanding of the possible interaction of AgNPs with SARS-CoV-2. The study focuses on several in vivo toxicological studies of AgNPs and a dose extrapolation to humans to determine the chief avenue of exposure. It can be concluded that the use of AgNPs as a possible treatment for SARS-CoV-2 could be viable, based on comparing the virus' behavior to that of similar viruses in in vivo studies, and that the suggested route of administration in terms of least degree of adverse effects is inhalation. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Respiratory Disease Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

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.

Quantitative biokinetics over a 28 day period of freshly generated, pristine, 20 nm silver nanoparticle aerosols in healthy adult rats after a single 1½-hour inhalation exposure

Background

There is a steadily increasing quantity of silver nanoparticles (AgNP) produced for numerous industrial, medicinal and private purposes, leading to an increased risk of inhalation exposure for both professionals and consumers. Particle inhalation can result in inflammatory and allergic responses, and there are concerns about other negative health effects from either acute or chronic low-dose exposure.

Results

To study the fate of inhaled AgNP, healthy adult rats were exposed to 1½-hour intra-tracheal inhalations of pristine ¹⁰⁵Ag-radiolabeled, 20 nm AgNP aerosols (with mean doses across all rats of each exposure group of deposited NP-mass and NP-number being 13.5 ± 3.6 μg, 7.9 ± 3.2•10¹¹, respectively). At five time-points (0.75 h, 4 h, 24 h, 7d, 28d) post-exposure (p.e.), a complete balance of the [¹⁰⁵Ag]AgNP fate and its degradation products were quantified in organs, tissues, carcass, lavage and body fluids, including excretions.

Rapid dissolution of [¹⁰⁵Ag]Ag-ions from the [¹⁰⁵Ag]AgNP surface was apparent together with both fast particulate airway clearance and long-term particulate clearance from the alveolar region to the larynx. The results are compatible with evidence from the literature that the released [¹⁰⁵Ag]Ag-ions precipitate rapidly to low-solubility [¹⁰⁵Ag]Ag-salts in the ion-rich epithelial lining lung fluid (ELF) and blood. Based on the existing literature, the degradation products rapidly translocate across the air-blood-barrier (ABB) into the blood and are eliminated via the liver and gall-bladder into the small intestine for fecal excretion. The pathway of [¹⁰⁵Ag]Ag-salt precipitates was compatible with auxiliary biokinetics studies at 24 h and 7 days after either intravenous injection or intratracheal or oral instillation of [^110mAg]AgNO₃ solutions in sentinel groups of rats. However, dissolution of [¹⁰⁵Ag]Ag-ions appeared not to be complete after a few hours or days but continued over two weeks p.e. This was due to the additional formation of salt layers on the [¹⁰⁵Ag]AgNP surface that mediate and prolonge the dissolution process. The concurrent clearance of persistent cores of [¹⁰⁵Ag]AgNP and [¹⁰⁵Ag]Ag-salt precipitates results in the elimination of a fraction > 0.8 (per ILD) after one week, each particulate Ag-species accounting for about half of this. After 28 days p.e. the cleared fraction rises marginally to 0.94 while 2/3 of the remaining [¹⁰⁵Ag]AgNP are retained in the lungs and 1/3 in secondary organs and tissues with an unknown partition of the Ag species involved. However, making use of our previous biokinetics studies of poorly soluble [¹⁹⁵Au]AuNP of the same size and under identical experimental and exposure conditions (Kreyling et al., ACS Nano 2018), the kinetics of the ABB-translocation of [¹⁰⁵Ag]Ag-salt precipitates was estimated to reach a fractional maximum of 0.12 at day 3 p.e. and became undetectable 16 days p.e. Hence, persistent cores of [¹⁰⁵Ag]AgNP were cleared throughout the study period. Urinary [¹⁰⁵Ag]Ag excretion is minimal, finally accumulating to 0.016.

Conclusion

The biokinetics of inhaled [¹⁰⁵Ag]AgNP is relatively complex since the dissolving [¹⁰⁵Ag]Ag-ions (a) form salt layers on the [¹⁰⁵Ag]AgNP surface which retard dissolution and (b) the [¹⁰⁵Ag]Ag-ions released from the [¹⁰⁵Ag]AgNP surface form poorly-soluble precipitates of [¹⁰⁵Ag]Ag-salts in ELF. Therefore, hardly any [¹⁰⁵Ag]Ag-ion clearance occurs from the lungs but instead [¹⁰⁵Ag]AgNP and nano-sized precipitated [¹⁰⁵Ag]Ag-salt are cleared via the larynx into GIT and, in addition, via blood, liver, gall bladder into GIT with one common excretional pathway via feces out of the body.

Pulmonary toxicity of silver vapours, nanoparticles and fine dusts: A review

Silver is used in a wide range of products, and during their production and use, humans may be exposed through inhalation. Therefore, it is critical to know the concentration levels at which adverse effects may occur. In rodents, inhalation of silver nanoparticles has resulted in increased silver in the lungs, lymph nodes, liver, kidney, spleen, ovaries, and testes. Reported excretion pathways of pulmonary silver are urinary and faecal excretion. Acute effects in humans of the inhalation of silver include lung failure that involved increased heart rate and decreased arterial blood oxygen pressure. Argyria-a blue-grey discoloration of skin due to deposited silver-was observed after pulmonary exposure in 3 individuals; however, the presence of silver in the discolorations was not tested. Argyria after inhalation seems to be less likely than after oral or dermal exposure. Repeated inhalation findings in rodents have shown effects on lung function, pulmonary inflammation, bile duct hyperplasia, and genotoxicity. In our evaluation, the range of NOAEC values was 0.11-0.75 mg/m³. Silver in the ionic form is likely more toxic than in the nanoparticle form but that difference could reflect their different biokinetics. However, silver nanoparticles and ions have a similar pattern of toxicity, probably reflecting that the effect of silver nanoparticles is primarily mediated by released ions. Concerning genotoxicity studies, we evaluated silver to be positive based on studies in mammalian cells in vitro and in vivo when considering various exposure routes. Carcinogenicity data are absent; therefore, no conclusion can be provided on this endpoint.

Assessing human exposure risk and lung disease burden posed by airborne silver nanoparticles emitted by consumer spray products

Background

No systematic investigations have been conducted to assess the lung burden imposed by the chronic inhalation of silver nanoparticles (AgNPs) emitted by spray products.

Objective

The objective of this study was to formulate a study framework that integrates a probabilistic risk assessment scheme with a mechanistic lung burden model for the estimation of health risks associated with the long-term inhalation of AgNP-containing spray products.

Materials and methods

A compartmentalized physiologically based alveolar deposition (PBAD) model was used to estimate AgNP lung burden. Dose–response relationships were established using nanotoxicity data sets obtained from rats (as a model organism). Weibull model-based thresholds of AgNP lung burden based on neutrophil-elevated inflammation bio-markers were estimated from Hill-based exposure–response relationships. Finally, the risks of lung disease posed by various AgNP-containing spray products were assessed.

Results

Conservative thresholds for the prevention of pulmonary disease were estimated as follows (mean ± SE): 34 nm AgNPs (0.32±0.22 mg) and 60 nm AgNPs (1.08±0.64 mg). Our results indicate that the risk probability was ~0.5 that the hazard quotient (HQ) estimates of deodorant with a count median diameter (CMD) ≈30 nm exceeded 1. The primary risk posed by AgNPs is transferred from the interstitial region to lymph nodes. Under the condition of 50% risk probability, the 97.5 percentile of HQ for the spray products were as follows: CMD ≈30 nm (~3.4) and CMD ≈60 nm (~1.1).

Conclusion

Our application of the proposed risk assessment scheme to the results obtained in an in vivo animal model proved highly effective in elucidating the relationship between the characteristics of metallic NP-containing spray products and their corresponding toxicity. The integration of the proposed PBAD model with a risk assessment framework enables the rapid assessment of risk posed by spray products containing metallic NPs over various time scales.

Evaluation of Some Biochemical Parameters and Brain Oxidative Stress in Experimental Rats Exposed Chronically to Silver Nitrate and the Protective Role of Vitamin E and Selenium

Due to undesirable hazardous interactions with biological systems, this investigation was undertaken to evaluate the effect of chronic exposure to silver on certain biochemical and some oxidative stress parameters with histopathological examination of brain, as well as the possible protective role of selenium and/or vitamin E as nutritional supplements. Thirty six male rats were divided into six groups of six each: the first group used as a control group. Group II given both vitamin E (400 mg/kg) of diet and selenium (Se) (1 mg/L) in their drinking water. Group III given silver as silver nitrate (AgNO₃) (20 mg/L). Group IV given vitamin E and AgNO₃. Group V given both AgNO₃ and selenium. Group VI given AgNO₃, vitamin E and Se. The animals were in the same exposure conditions for 3 months. According to the results which have been obtained; there was an increase in serum lactate dehydrogenase (LDH), lipase activities and cholesterol level, a decrease in serum total protein, calcium and alkaline phosphatase (ALP) activity in Ag-intoxicated rats. Moreover, the findings showed that Ag⁺ ions affected antioxidant defense system by decreasing superoxide dismutase (SOD) activity and increasing vitamin E concentration with a high level of malondialdehyde (MDA) in brain tissue. The histological examination also exhibited some nervous tissue alterations including hemorrhage and cytoplasm vacuolization. However, the co-administration of selenium and/or vitamin E ameliorated the biochemical parameters and restored the histological alterations. In conclusion, this study indicated that silver could cause harmful effects in animal body and these effects can be more toxic in high concentrations or prolonged time exposure to this metal. However, selenium and vitamin E act as powerful antioxidants which may exercise adverse effect against the toxicity of this metal.

Impact of pulmonary exposure to gold core silver nanoparticles of different size and capping agents on cardiovascular injury

BACKGROUND

The uses of engineered nanomaterials have expanded in biomedical technology and consumer manufacturing. Furthermore, pulmonary exposure to various engineered nanomaterials has, likewise, demonstrated the ability to exacerbate cardiac ischemia reperfusion (I/R) injury. However, the influence of particle size or capping agent remains unclear. In an effort to address these influences we explored response to 2 different size gold core nanosilver particles (AgNP) with two different capping agents at 2 different time points. We hypothesized that a pulmonary exposure to AgNP induces cardiovascular toxicity influenced by inflammation and vascular dysfunction resulting in expansion of cardiac I/R Injury that is sensitive to particle size and the capping agent.

METHODS

Male Sprague-Dawley rats were exposed to 200 μg of 20 or 110 nm polyvinylprryolidone (PVP) or citrate capped AgNP. One and 7 days following intratracheal instillation serum was analyzed for concentrations of selected cytokines; cardiac I/R injury and isolated coronary artery and aorta segment were assessed for constrictor responses and endothelial dependent relaxation and endothelial independent nitric oxide dependent relaxation.

RESULTS

AgNP instillation resulted in modest increase in selected serum cytokines with elevations in IL-2, IL-18, and IL-6. Instillation resulted in a derangement of vascular responses to constrictors serotonin or phenylephrine, as well as endothelial dependent relaxations with acetylcholine or endothelial independent relaxations by sodium nitroprusside in a capping and size dependent manner. Exposure to both 20 and 110 nm AgNP resulted in exacerbation cardiac I/R injury 1 day following IT instillation independent of capping agent with 20 nm AgNP inducing marginally greater injury. Seven days following IT instillation the expansion of I/R injury persisted but the greatest injury was associated with exposure to 110 nm PVP capped AgNP resulted in nearly a two-fold larger infarct size compared to naïve.

CONCLUSIONS

Exposure to AgNP may result in vascular dysfunction, a potentially maladaptive sensitization of the immune system to respond to a secondary insult (e.g., cardiac I/R) which may drive expansion of I/R injury at 1 and 7 days following IT instillation where the extent of injury could be correlated with capping agents and AgNP size.

Pulmonary effects of inhalation of spark-generated silver nanoparticles in Brown-Norway and Sprague-Dawley rats

Background

The increasing use of silver nanoparticles (AgNPs) in consumer products is concerning. We examined the potential toxic effects when inhaled in Brown-Norway (BN) rats with a pre-inflammatory state compared to Sprague–Dawley (SD) rats.

Methods

We determined the effect of AgNPs generated from a spark generator (mass concentration: 600–800 μg/mm³; mean diameter: 13–16 nm; total lung doses: 8 [Low] and 26–28 [High] μg) inhaled by the nasal route in both rat strains. Rats were sacrificed at day 1 and day 7 after exposure and measurement of lung function.

Results

In both strains, there was an increase in neutrophils in bronchoalveolar lavage (BAL) fluid at 24 h at the high dose, with concomitant eosinophilia in BN rats. While BAL inflammatory cells were mostly normalised by Day 7, lung inflammation scores remained increased although not the tissue eosinophil scores. Total protein levels were elevated at both lung doses in both strains. There was an increase in BAL IL-1β, KC, IL-17, CCL2 and CCL3 levels in both strains at Day 1, mostly at high dose. Phospholipid levels were increased at the high dose in SD rats at Day 1 and 7, while in BN rats, this was only seen at Day 1; surfactant protein D levels decreased at day 7 at the high dose in SD rats, but was increased at Day 1 at the low dose in BN rats. There was a transient increase in central airway resistance and in tissue elastance in BN rats at Day 1 but not in SD rats. Positive silver-staining was seen particularly in lung tissue macrophages in a dose and time-dependent response in both strains, maximal by day 7. Lung silver levels were relatively higher in BN rat and present at day 7 in both strains.

Conclusions

Presence of cellular inflammation and increasing silver-positive macrophages in lungs at day 7, associated with significant levels of lung silver indicate that lung toxicity is persistent even with the absence of airway luminal inflammation at that time-point. The higher levels and persistence of lung silver in BN rats may be due to the pre-existing inflammatory state of the lungs.

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

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

Aerosolized Silver Nanoparticles in the Rat Lung and Pulmonary Responses over Time

Silver nanoparticle (Ag NP) production methods are being developed and refined to produce more uniform Ag NPs through chemical reactions involving silver salt solutions, solvents, and capping agents to control particle formation. These chemical reactants are often present as contaminants and/or coatings on the Ag NPs, which could alter their interactions in vivo. To determine pulmonary effects of citrate-coated Ag NPs, Sprague-Dawley rats were exposed once nose-only to aerosolized Ag NPs (20 nm [C20] or 110 nm [C110] Ag NPs) for 6 hr. Bronchoalveolar lavage fluid (BALF) and lung tissues were obtained at 1, 7, 21, and 56 days postexposure for analyses. Inhalation of Ag NPs, versus citrate buffer control, produced significant inflammatory and cytotoxic responses that were measured in BALF cells and supernatant. At day 7, total cells, protein, and lactate dehydrogenase were significantly elevated in BALF, and peak histopathology was noted after C20 or C110 exposure versus control. At day 21, BALF polymorphonuclear cells and tissue inflammation were significantly greater after C20 versus C110 exposure. By day 56, inflammation was resolved in Ag NP-exposed animals. Overall, results suggest delayed, short-lived inflammatory and cytotoxic effects following C20 or C110 inhalation and potential for greater responses following C20 exposure.

Tissue distribution and acute toxicity of silver after single intravenous administration in mice: nano-specific and size-dependent effects

BACKGROUND

Silver nanoparticles (AgNPs) are an important class of nanomaterials used as antimicrobial agents for a wide range of medical and industrial applications. However toxicity of AgNPs and impact of their physicochemical characteristics in in vivo models still need to be comprehensively characterized. The aim of this study was to investigate the effect of size and coating on tissue distribution and toxicity of AgNPs after intravenous administration in mice, and compare the results with those obtained after silver acetate administration.

METHODS

Male CD-1(ICR) mice were intravenously injected with AgNPs of different sizes (10 nm, 40 nm, 100 nm), citrate-or polyvinylpyrrolidone-coated, at a single dose of 10 mg/kg bw. An equivalent dose of silver ions was administered as silver acetate. Mice were euthanized 24 h after the treatment, and silver quantification by ICP-MS and histopathology were performed on spleen, liver, lungs, kidneys, brain, and blood.

RESULTS

For all particle sizes, regardless of their coating, the highest silver concentrations were found in the spleen and liver, followed by lung, kidney, and brain. Silver concentrations were significantly higher in the spleen, lung, kidney, brain, and blood of mice treated with 10 nm AgNPs than those treated with larger particles. Relevant toxic effects (midzonal hepatocellular necrosis, gall bladder hemorrhage) were found in mice treated with 10 nm AgNPs, while in mice treated with 40 nm and 100 nm AgNPs lesions were milder or negligible, respectively. In mice treated with silver acetate, silver concentrations were significantly lower in the spleen and lung, and higher in the kidney than in mice treated with 10 nm AgNPs, and a different target organ of toxicity was identified (kidney).

CONCLUSIONS

Administration of the smallest (10 nm) nanoparticles resulted in enhanced silver tissue distribution and overt hepatobiliary toxicity compared to larger ones (40 and 100 nm), while coating had no relevant impact. Distinct patterns of tissue distribution and toxicity were observed after silver acetate administration. It is concluded that if AgNPs become systemically available, they behave differently from ionic silver, exerting distinct and size-dependent effects, strictly related to the nanoparticulate form.

Cardiac Ischemia Reperfusion Injury Following Instillation of 20 nm Citrate-capped Nanosilver

BACKGROUND

Silver nanoparticles (AgNP) have garnered much interest due to their antimicrobial properties, becoming one of the most utilized nano-scale materials. However, any potential evocable cardiovascular injury associated with exposure has not been reported to date. We have previously demonstrated expansion of myocardial infarction after intratracheal (IT) instillation of carbon-based nanomaterials. We hypothesized pulmonary exposure to Ag core AgNP induces a measureable increase in circulating cytokines, expansion of cardiac ischemia-reperfusion (I/R) injury and is associated with depressed coronary constrictor and relaxation responses. Secondarily, we addressed the potential contribution of silver ion release on AgNP toxicity.

METHODS

Male Sprague-Dawley rats were exposed to 200 μl of 1 mg/ml of 20 nm citrate-capped Ag core AgNP, 0.01, 0.1, 1 mg/ml Silver Acetate (AgAc), or a citrate vehicle by intratracheal (IT) instillation. One and 7 days following IT instillation the lungs were evaluated for inflammation and the presence of silver; serum was analyzed for concentrations of selected cytokines; cardiac I/R injury and coronary artery reactivity were assessed.

RESULTS

AgNP instillation resulted in modest pulmonary inflammation with detection of silver in lung tissue and alveolar macrophages, elevation of serum cytokines: G-CSF, MIP-1α, IL-1β, IL-2, IL-6, IL-13, IL-10, IL-18, IL-17α, TNFα, and RANTES, expansion of I/R injury and depression of the coronary vessel reactivity at 1 day post IT compared to vehicle treated rats. Silver within lung tissue was persistent at 7 days post IT instillation and was associated with an elevation in cytokines: IL-2, IL-13, and TNFα and expansion of I/R injury. AgAc resulted in a concentration dependent infarct expansion and depressed vascular reactivity without marked pulmonary inflammation or serum cytokine response.

CONCLUSIONS

Based on these data, IT instillation of AgNP increases circulating levels of several key cytokines, which may contribute to persistent expansion of I/R injury possibly through an impaired vascular responsiveness.

Influence of particle size on persistence and clearance of aerosolized silver nanoparticles in the rat lung

The growing use of silver nanoparticles (AgNPs) in consumer products raises concerns about potential health effects. This study investigated the persistence and clearance of 2 different size AgNPs (20 and 110 nm) delivered to rats by single nose-only aerosol exposures (6 h) of 7.2 and 5.4 mg/m(3), respectively. Rat lung tissue was assessed for silver accumulations using inductively-coupled plasma mass spectrometry (ICP-MS), autometallography, and enhanced dark field microscopy. Involvement of tissue macrophages was assessed by scoring of silver staining in bronchoalveolar lavage fluid (BALF). Silver was abundant in most macrophages at 1 day post-exposure. The group exposed to 20 nm AgNP had the greatest number of silver positive BALF macrophages at 56 days post-exposure. While there was a significant decrease in the amount of silver in lung tissue at 56 days post-exposure compared with 1 day following exposure, at least 33% of the initial delivered dose was still present for both AgNPs. Regardless of particle size, silver was predominantly localized within the terminal bronchial/alveolar duct junction region of the lung associated with extracellular matrix and within epithelial cells. Inhalation of both 20 and 110 nm AgNPs resulted in a persistence of silver in the lung at 56 days post-exposure and local deposition as well as accumulation of silver at the terminal bronchiole alveolar duct junction. Further the smaller particles, 20 nm AgNP, produced a greater silver burden in BALF macrophages as well as greater persistence of silver positive macrophages at later timepoints (21 and 56 days).

Aluminum Nanoparticles Induce ERK and p38MAPK Activation in Rat Brain

Aluminum nanoparticles (Al-NPs) are one of the most widely used nanomaterial in cosmetics and medical materials. For this reason, Al-NP exposure is very likely to occur via inhalation in the environment and the workplace. Nevertheless, little is known about the mechanism of Al-NP neurotoxicity via inhalation exposure. In this study, we investigated the effect AL-NPs on the brain. Rats were exposed to Al-NPs by nasal instillation at 1 mg/kg body weight (low exposure group), 20 mg/kg body weight (moderate exposure group), and 40 mg/kg body weight (high exposure group), for a total of 3 times, with a 24-hr interval after each exposure. Inductively coupled plasma mass spectrometry (ICP-MS) analysis indicated that the presence of aluminum was increased in a dose-dependent manner in the olfactory bulb (OFB) and the brain. In microarray analysis, the regulation of mitogen-activated protein kinases (MAPK) activity (GO: 0043405), including Ptprc, P2rx7, Map2k4, Trib3, Trib1, and Fgd4 was significantly over-expressed in the treated mice than in the controls (p = 0.0027). Moreover, Al-NPs induced the activation of ERK1 and p38 MAPK protein expression in the brain, but did not alter the protein expression of JNK, when compared to the control. These data demonstrate that the nasal exposure of Al-NPs can permeate the brain via the olfactory bulb and modulate the gene and protein expression of MAPK and its activity.