Deriving a provisional tolerable intake for intravenous exposure to silver nanoparticles released from medical devices

In Vivo Pro-Inflammatory Effects of Silver Nanoparticles on the Colon Depend on Time and Route of Exposure

Nanosilver is a popular nanomaterial, the potential influence of which on humans is of serious concern. Herein, we exposed male Wistar rats to two regimens: a repeated oral dose of 30 mg/kg bw silver nanoparticles (AgNPs) over 28 days and a single-dose injection of 5 mg/kg bw of AgNPs. At three different time points, we assessed antioxidant defense, oxidative stress and inflammatory parameters in the colon, as well as toxicity markers in the liver and plasma. Both experimental scenarios showed increased oxidative stress and inflammation in the colon. Oral administration seemed to be linked to increased reactive oxygen species generation and lipid peroxidation, while the effects induced by the intravenous exposure were probably mediated by silver ions released from the AgNPs. Repeated oral exposure had a more detrimental effect than the single-dose injection. In conclusion, both administration routes had a similar impact on the colon, although the underlying mechanisms are likely different.

Case study: risk associated to wearing silver or graphene nanoparticle-coated facemasks for protection against COVID-19

The world is living a pandemic situation derived from the worldwide spreading of SARS-CoV-2 virus causing COVID-19. Facemasks have proven to be one of the most effective prophylactic measures to avoid the infection that has made that wearing of facemasks has become mandatory in most of the developed countries. Silver and graphene nanoparticles have proven to have antimicrobial properties and are used as coating of these facemasks to increase the effectivity of the textile fibres. In the case of silver nanoparticles, we have estimated that in a real scenario the systemic (internal) exposure derived from wearing these silver nanoparticle facemasks would be between 7.0 × 10^–5 and 2.8 × 10^–4 mg/kg bw/day. In addition, we estimated conservative systemic no effect levels between 0.075 and 0.01 mg/kg bw/day. Therefore, we estimate that the chronic exposure to silver nanoparticles derived form facemasks wearing is safe. In the case of graphene, we detected important gaps in the database, especially regarding toxicokinetics, which prevents the derivation of a systemic no effect level. Nevertheless, the qualitative approach suggests that the risk of dermal repeated exposure to graphene is very low, or even negligible. We estimated that for both nanomaterials, the risk of skin sensitisation and genotoxicity is also negligible.

Serum ceruloplasmin monitoring in a case of silver intoxication due to intravenous silver infusion

INTRODUCTION

Colloidal silver packaged as a dietary supplement is readily available online and is thought to be safe. Literature describing its toxicity in humans is scarce.

CASE REPORT

A 47-year-old man presented to us for sensory and gait problems. He had unremarkable past health except dystrophic nails. He further volunteered a history of receiving chronic oral and intravenous administration of colloidal silver. We confirmed his plasma silver was 1200-fold elevated, measuring 11990 nmol/L (normal < 10 nmol/L). He had deranged liver function tests, and liver biopsy showed distorted acinar architecture, bridging fibrosis and lymphocytic infiltrate with silver particles clustering along the vascular endothelium and portal venules. Brain magnetic resonance imagining showed features of mineralization over bilateral globus pallidi. There was biochemical evidence of central adrenal insufficiency, intracellular iron overload and hypoceruloplasminemia (<0.05 g/L). Gradual clinical and biochemical improvement was noted after silver cessation: his plasma silver dropped to 4800 nmol/L (3 months) and 1650 nmol/L (12 months), and serum ceruloplasmin reverted to 0.13 g/L (10 months) and 0.29 g/L (20 months).

CONCLUSIONS

The potential effects of silver to liver and copper metabolism were shown in this case. Serum ceruloplasmin also serves as a surrogate marker in monitoring silver intoxication.

The emerging risk of exposure to nano(micro)plastics on endocrine disturbance and reproductive toxicity: From a hypothetical scenario to a global public health challenge

Humans are potentially exposed to nano(micro)plastics, however their interaction with tissues and cells in humans remains largely unknown. This premise is particularly notable with nano-sized plastic particulates, a potentially most pernicious form of plastic pollution. In this study, even in a hypothetical scenario in terms of dose (1, 3, 6 and 10 mg/kg-day) and exposure time (five weeks), the potential endocrine disturbances with particular reference to reproductive toxicity of polystyrene nanoplastics (PS NPs, average size = 38.92 nm) was studied in male rats considering biomarkers of semen quality, changes in hormonal milieu and molecular signatures of endocrine disruption. Sperm DNA integrity and its chromatin structure were also analyzed. There observed significant inverse associations between exposure to PS NPs and serum concentrations of testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Tissue and cell impairments were also noticed even at the lowest tested dosage, though the severity of lesions followed a clear dose-response pattern. DNA damage as well as alterations in sperm morphology and viability were evident, again proportionally with the amount of exposure dosage. RT-qPCR data were in accordance with the results of physio-histological alterations and fluorescence imaging, as significant down-regulation of PLZF, DAZL, FSH and LH gene expressions were noticed in the testis of exposed animals, suggesting that exposure interferes with spermatogenesis and also with HPT-axis. However, among those with highest exposure dosage, expressions of FSH and LH were significantly increased. ABP modulation further revealed evidence of a nonlinear dose response. The association between PS NPs exposure and GnRH was indeed in an unexpected positive direction, though these end-points were less sensitive at higher doses. Although additional evidence is warranted, the present work provides new insights into the possible risks of plastic nanoparticles exposure in humans, especially since the problem is growing and will persist for a long time.

Eco-friendly synthesis of silver nanoparticles using Senna alata bark extract and its antimicrobial mechanism through enhancement of bacterial membrane degradation

Biological synthesis of nanomaterials has been increasingly gaining popularity due to its eco-friendly nature and cost-effectiveness. This study aimed to synthesize silver nanoparticles (AgNPs) using Senna alata bark extract as reducing and capping agents, and to evaluate their antimicrobial activities. AgNPs was characterized using UV-vis spectrophotometry, transmission electron microscopy, and Fourier transform infrared spectroscopy (FTIR). The formation of AgNPs was monitored by recording the surface plasmon resonance peak observed at 425 nm. High-resolution TEM images elucidated the formation of spherical AgNPs with an average diameter of 10-30 nm. Energy dispersive spectroscopy (EDS) revealed the presence of silver. The functional groups of biomolecules present in the extract and their interaction with AgNPs were identified through FTIR analysis. Biosynthesized AgNPs displayed antimicrobial activity against different microorganisms, including Gram-positive and Gram-negative bacteria as well as fungi, as indicated by the diameter of inhibition zones between 11.37 and 14.87 mm. Minimum inhibitory concentration of AgNPs for the tested microorganisms was in the range from 31.25 to 125 μg/mL. Potassium leakage is a primary indicator of membrane damage which is a significant mode of action of AgNPs against the tested microorganisms. The amount of potassium ions leaked from the microbial cells after 4 h contact time ranged between 0.97 and 3.05 ppm. Morphological changes were observed in all AgNPs-treated microorganisms. The green synthesized AgNPs with high antimicrobial activity has potential to be used in food packaging and biomedical research areas.

Characterization of Airborne Particle Release from Nanotechnology-enabled Clothing Products

This study investigated airborne particle release from seventeen nanotechnology-enabled clothing items, including eleven items that were advertised as containing silver nanoparticles. Clothing wear was simulated using an abrader, where the rotating clothing samples came in contact with felt abrader wheels, and size distribution and concentration of the released particles were measured using a Scanning Mobility Particle Sizer and Aerodynamic Particle Sizer. Through the use of inductively coupled plasma mass spectrometry, silver was detected in all eleven products advertised as containing silver, and its concentration varied from approximately 1 ppm to ~1.5×10⁵ ppm depending on the product. Nano-sized particles, as well as larger agglomerates, were released from all investigated products with concentrations as high as ~2×10⁴ particles/cm³; the concentration and size distribution varied substantially from product to product, and silver-based clothing tended to release smaller and higher number concentrations of particles than products where fibers were formulated using nanotechnology. Examination of the released particles using TEM confirmed the presence of manufactured nanoparticles; airborne sample analysis using SEM/EDS showed that the released particles contained Ag as well as other metals. This study can be valuable for the risk assessment of nanotechnology-based consumer goods, especially clothing containing silver.

N-Acetylcysteine reverses silver nanoparticle intoxication in rats

The increasing use of silver nanoparticles (AgNPs) in consumer products raises the risk of human toxicity. Currently, there are no therapeutic options or established treatment protocols in cases of AgNPs intoxication. We demonstrated previously that thiol antioxidants compounds can reverse the cytotoxicity induced by AgNPs in Huh-7 hepatocarcinoma cells. Here, we investigated the use of N-acetylcysteine (NAC) against the systemic toxic effects of AgNPs (79.3 nm) in rats. Biochemical, histopathological, hematological, and oxidative parameters showed that a single intravenous injection of AgNPs (5 mg/kg b.w.) induced deleterious effects such as hepatotoxicity, potentially as a result of AgNPs accumulation in the liver. Treatment with a single intraperitoneal injection of NAC (1 g/kg b.w.) one hour after AgNPs exposure significantly attenuated all toxic effects evaluated and altered the bioaccumulation and release patterns of AgNPs in rats. The findings show that NAC may be a promising candidate for clinical management of AgNPs intoxication.