Silver Mass Research Articles

An Integrated In Vitro\u2013In Silico Approach for Silver Nanoparticle Dosimetry in Cell Cultures

Potential human and environmental hazards resulting from the exposure of living organisms to silver nanoparticles (Ag NPs) have been the subject of intensive discussion in the last decade. Despite the growing use of Ag NPs in biomedical applications, a quantification of the toxic effects as a function of the total silver mass reaching cells (namely, target cell dose) is still needed. To provide a more accurate dose-response analysis, we propose a novel integrated approach combining well-established computational and experimental methodologies. We first used a particokinetic model (ISD3) for providing experimental validation of computed Ag NP sedimentation in static-cuvette experiments. After validation, ISD3 was employed to predict the total mass of silver reaching human endothelial cells and hepatocytes cultured in 96 well plates. Cell viability measured after 24 h of culture was then related to this target cell dose. Our results show that the dose perceived by the cell monolayer after 24 h of exposure is around 85% lower than the administered nominal media concentration. Therefore, accurate dosimetry considering particle characteristics and experimental conditions (e.g., time, size and shape of wells) should be employed for better interpreting effects induced by the amount of silver reaching cells.

Invasive silver carp may compete with unionid mussels for algae: First experimental evidence

Abstract Unionid mussels are imperilled throughout the US, where their global diversity is highest. Silver carp (Hypophthalmichthys molitrix Valenciennes in Cuvier & Valenciennes, 1844), an invasive planktivorous fish, has spread throughout Midwestern rivers and currently threatens the Great Lakes. Because silver carp remove plankton and other particles from the water column, they may compete with mussels for food resources. This would be among the first examples of a direct competitive interaction between fish and mussels. To examine the potential for competition, a 30 day tank experiment was performed with 2 year old fatmucket mussels (Lampsilis siliquoidea Barnes, 1823) and age‐1 silver carp in three treatments: fatmucket only, silver carp only and fatmucket + silver carp. All tanks were given a commercial algal‐based diet daily and dry mass of suspended particles (an estimate of available food) and NH4, NO3 and NO2 concentrations were quantified every 5 days to track food availability and changes in nutrients. Initial and final silver carp total length (mm) and mass (g), and fatmucket length (mm), height (mm) and surface area (cm2) were measured. Survival was 100% over the test duration for both species. Fatmucket grew less in the fatmucket + silver carp treatment, whereas silver carp growth was undetectable regardless of treatment. Fatmucket also exhibited increased movement in the presence of silver carp. Suspended particles did not differ among treatments. Dissolved nitrogen concentrations were higher in the silver carp treatments, suggesting that silver carp increase nutrient availability in aquatic systems. Overall, the slower growth rates observed in the fatmucket + silver carp treatment compared with the mussel‐only treatment suggest exploitative competition between invasive planktivorous silver carp and fatmucket, and this competition may contribute to additional stress on already imperilled mussels.

Synthesis and Application of Silver Nanoparticles (Ag NPs) for the Prevention of Infection in Healthcare Workers.

Silver is easily available and is known to have microbicidal effect; moreover, it does not impose any adverse effects on the human body. The microbicidal effect is mainly due to silver ions, which have a wide antibacterial spectrum. Furthermore, the development of multidrug-resistant bacteria, as in the case of antibiotics, is less likely. Silver ions bind to halide ions, such as chloride, and precipitate; therefore, when used directly, their microbicidal activity is shortened. To overcome this issue, silver nanoparticles (Ag NPs) have been recently synthesized and frequently used as microbicidal agents that release silver ions from particle surface. Depending on the specific surface area of the nanoparticles, silver ions are released with high efficiency. In addition to their bactericidal activity, small Ag NPs (<10 nm in diameter) affect viruses although the microbicidal effect of silver mass is weak. Because of their characteristics, Ag NPs are useful countermeasures against infectious diseases, which constitute a major issue in the medical field. Thus, medical tools coated with Ag NPs are being developed. This review outlines the synthesis and utilization of Ag NPs in the medical field, focusing on environment-friendly synthesis and the suppression of infections in healthcare workers (HCWs).

Extracellular ATP promotes breast cancer invasion and epithelial-mesenchymal transition via hypoxia-inducible factor 2α signaling.

Extracellular ATP has been shown to play an important role in invasion and the epithelial‐mesenchymal transition (EMT) process in breast cancer; however, the mechanism is unclear. Here, by using a cDNA microarray, we demonstrated that extracellular ATP could stimulate hypoxia‐inducible factor (HIF) signaling and upregulate hypoxia‐inducible factor 1/2α (HIF‐1/2α) expression. After knocking down HIF‐1/2α using siRNA, we found that ATP‐driven invasion and EMT were significantly attenuated via HIF2A‐siRNA in breast cancer cells. By using ChIP assays, we revealed that the biological function of extracellular ATP in invasion and EMT process depended on HIF‐2α direct targets, among which lysyl oxidase‐like 2 (LOXL2) and matrix metalloproteinase‐9 (MMP‐9) mediated ATP‐driven invasion, and E‐cadherin and Snail mediated ATP‐driven EMT, respectively. In addition, using silver staining and mass spectrometry, we found that phosphoglycerate kinase 1 (PGK1) could interact with HIF‐2α and mediate ATP‐driven HIF‐2α upregulation. Furthermore, we demonstrated that expressions of HIF‐2α and its target proteins could be regulated via ATP by AKT‐PGK1 pathway. Using a Balb/c mice model, we illustrated the function of HIF‐2α in promoting tumor growth and metastasis in vivo. Moreover, by exploring online databases, we found that molecules involved in ATP‐HIF‐2α signaling were highly expressed in human breast carcinoma tissues and were associated with poor prognosis. Altogether, these findings suggest that extracellular ATP could promote breast carcinoma invasion and EMT via HIF‐2α signaling, which may be a potential target for future anti–metastasis therapy.

PENGEMBANGAN METODE ELEKTRODEPOSISI UNTUK PENGAMBILAN KEMBALI PERAK DARI LIMBAH FOTORONTGEN

Silver in its ionic form is one of the heavy metals dangerous if it is discharged into the environment or into the body of humans or other living things. Silver metal pollution sources, one of which comes from waste fixer which is a waste from the photorontgen process. However, silver in its metal form has a high economic value. Therefore, the development of techniques or methods of recovering silver from the waste solution and turning it into a metal form is important to do so that the metal does not pollute the environment and can be reused economically. One method that can be done is by electrolytic deposition or electrodeposition in which silver in the form of a silver thiosulfate complex compound in the photorontgen waste is converted to Ag metal through a redox reaction. To obtain good quality and quantity of silver deposits in the electrodeposition process, it is necessary to optimize several factors that influence, among others, optimization of potential difference, time and pH of the solution. This study aims to determine the effect of potential difference, time and pH of the solution on the efficiency of the electrodeposition process. Electrodeposition efficiency was determined based on the percentage of reduced silver mass calculated from the decrease in Ag concentration in photorontgen waste solution before and after the electrodeposition process. Based on the results of the study obtained the optimum electrodeposition process at a potential difference of 8 V for 75 minutes and the pH of the waste is 3, where the mass percent of silver which is reduced from waste is 86.49%.

Determination of silver nanoparticle dose in vitro

An important issue for interpreting in vitro nanomaterial testing is quantifying the dose delivered to target cells. Considerations include the concentration added to the culture, the proportion of the applied dose that interacts with the target cells, and the amount that is eventually absorbed by the target cells. Rapid and efficient techniques are needed to determine delivered doses. Previously, we demonstrated that TiO2 and silver nanoparticles (AgNP) were absorbed by cells in a dose dependent manner between 1 μg/ml and 30 μg/ml and were detected in cells by light scatter using a flow cytometer. Here, we compare four potential indices of the dose of AgNP to cells, including: inductively coupled plasma - mass spectrometry (ICP-MS); flow cytometry side scatter (SSC); and amount of silver deposited to the cell layer as estimated with both an integrated Volumetric Centrifugation Method - In Vitro Sedimentation, Diffusion and Dosimetry Model (VCM-ISDD) and a Distorted Grid (DG) model. A retinal pigment epithelial cell line was exposed to 20 nm or 75 nm citrate-coated AgNP for 24 h. The relationships between particle sizes and internalized doses varied according to the dose metric. Twenty-four hours after exposure, the cell layer contained a greater mass of silver when treated with 75 nm AgNP than with 20 nm AgNP. When the dose was expressed as the number of particles or as the total surface area of absorbed particles, however, the reverse was true; the dose to the cells was higher after exposure to 20 than 75 nm AgNP. Flow cytometry SSC increased with dose for both sizes of AgNP, and was correlated with Ag in cells measured by ICP-MS. The rate of SSC increase was greater for 75 than for 20 nm AgNP, suggesting it could be used as an indicator of cellular dose after accounting for particle size and composition. Silver was detected by ICP-MS in re-suspended supernates of the isolated cell layer suggested that not all the silver deposited to the cell layer was absorbed by the cells. Both the VCM-ISDD and DG models estimated the proportion of Ag deposited to the cellular layer, which in both cases was greater than the amount of silver in the cells measured by ICP-MS. Modeled deposition more closely compared to the total Ag deposition by ICP-MS, i.e. mass of silver in the cells plus the resuspended, unabsorbed Ag from the cell layer. ICP-MS indicated the mass of silver in cells from AgNP treatment, but not whether the Ag was in the form of particles or dissolved ions. Deposition models predicted the amount of AgNP deposited to the cell layer, but not cellular uptake. Flow cytometry SSC was correlated to cellular uptake of particle-form AgNP and could be calibrated against ICP-MS to indicate mass of cellular uptake. Therefore, a combination of approaches may be required to accurately understand cellular dosimetry of in vitro nanotoxicology experiments. In summary, cellular dosimetry is an important consideration for nanotoxicology experiments, and not necessarily related to the applied dose.

Bardet-Biedl syndrome protein-8 is involved in flagellar membrane protein transport in Chlamydomonas reinhardtii

Cilia and flagella on eukaryotic cells are polarized organelles extending from the surfaces of cells, which participate not only in cell motility, but also in signal transduction and other processes. Structural or functional abnormalities of cilia can cause various human diseases, termed ciliopathies. Bardet-Biedl syndrome (BBS) is a ciliopathic human genetic disorder, and the pathogenesis is that mutated BBS genes result in abnormal cilia function. In order to study the pathogenic genes BBS8, we screened bbs8 mutant in Chlamydomonas reinhardtii and did a lot of physiology and biochemistry experiments. We affirmed that BBS8 protein was a cilia protein and had specific localization in the basal body by immunofluorescence (IF). The bbs8 mutant lost photokinesis, and it was defective in flagella shortening with drug induction. The results of silver staining and mass spectrometric analysis showed aberrant accumulation of flagellar proteins in the mutant flagella. We concluded that the BBS8 protein plays a significant role in flagellar membrane proteins transport, and the BBS8 protein might mediate retrograde transport to exert physiological function in the process.

Lobar evenness of deposition/retention in rat lungs of inhaled silver nanoparticles: an approach for reducing animal use while maximizing endpoints

BackgroundInformation on particle deposition, retention and clearance are important for the evaluation of the risk of inhaled nanomaterials to human health. Recent revised OECD inhalation toxicity test guidelines require to evaluate the lung burden of nanomaterials after rodent subacute and subchronic inhalation exposure (OECD 412, OECD 413). These revised test guidelines require additional post-exposure observation (PEO) periods that include lung burden measurements that can inform on lung clearance behavior and translocation. The latter being particularly relevant when the testing chemical is a solid poorly soluble nanomaterial. Therefore, in the spirit of 3 R’s, we investigated whether measurement of retained lung burden of inhaled nanoparticles (NPs) in individual lung lobes is sufficient to determine retained lung burden in the total lung. If it is possible to use only one lobe, it will reduce animal use and maximize the number of endpoints evaluated.ResultsTo achieve these goals, rats were exposed nose-only for 1 or 5 days (6 h/day) to an aerosol of 20 nm well-dispersed silver nanoparticles (AgNPs), which is the desired particle diameter resulting in maximum deposition in the pulmonary region when inhaled as singlets. After exposure, the five lung lobes were separated and silver concentration was measured using inductively coupled plasma-mass spectrophotometer (ICP-MS). The results showed that the retention of deposited silver nanoparticle in the different lung lobes did not show any statistically significant difference among lung lobes in terms of silver mass per gram lung lobe. This novel finding of evenness of retention/deposition of inhaled 20 nm NPs in rats for all five lobes in terms of mass per unit tissue weight contrasts with earlier studies reporting greater apical lobe deposition of inhaled micro-particles in rodents. The difference is most likely due to preferred and efficient deposition of inhaled NPs by diffusion vs. additional deposition by sedimentation and impaction for micron-sized particles.ConclusionAgNPs following acute inhalation by rats are evenly retained in each lung lobe in terms of mass per unit lung tissue weight. Accordingly, we suggest sampling any of the rat lung lobes for lung burden analysis can be used to determine deposited or retained total lung burden after short-term inhalation of NPs and using the other lobes for collecting and analyzing bronchoalveolar lavage fluid (BALF) and for histopathological analysis. Therefore, by combining lung burden measurement, histopathological tissue preparation, and BALF assay in the same rat will reduce the number of animals used and maximize the number of endpoints measured.

Single-step Purification of Macromolecular Complexes Using RNA Attached to Biotin and a Photo-cleavable Linker.

For many years, the exceptionally strong and rapidly formed interaction between biotin and streptavidin has been successfully utilized for partial purification of biologically important RNA/protein complexes. However, this strategy suffers from one major disadvantage that limits its broader utilization: the biotin/streptavidin interaction can be broken only under denaturing conditions that also disrupt the integrity of the eluted complexes, hence precluding their subsequent functional analysis and/or further purification by other methods. In addition, the eluted samples are frequently contaminated with the background proteins that nonspecifically associate with streptavidin beads, complicating the analysis of the purified complexes by silver staining and mass spectrometry. To overcome these limitations, we developed a variant of the biotin/streptavidin strategy in which biotin is attached to an RNA substrate via a photo-cleavable linker and the complexes immobilized on streptavidin beads are selectively eluted to solution in a native form by long wave UV, leaving the background proteins on the beads. Shorter RNA binding substrates can be synthesized chemically with biotin and the photo-cleavable linker covalently attached to the 5' end of the RNA, whereas longer RNA substrates can be provided with the two groups by a complementary oligonucleotide. These two variants of the UV-elution method were tested for purification of the U7 snRNP-dependent processing complexes that cleave histone pre-mRNAs at the 3' end and they both proved to compare favorably to other previously developed purification methods. The UV-eluted samples contained readily detectable amounts of the U7 snRNP that was free of major protein contaminants and suitable for direct analysis by mass spectrometry and functional assays. The described method can be readily adapted for purification of other RNA binding complexes and used in conjunction with single- and double-stranded DNA binding sites to purify DNA-specific proteins and macromolecular complexes.

Transformation of engineered nanomaterials through the prism of silver sulfidation.

Understanding the structure transformation of engineered nanomaterials (ENMs) is a grand measurement challenge, which impacts many aspects of ENMs applications, such as their efficacy, safety, and environmental consequence. To address the significant knowledge gap regarding the fundamental kinetic rate and extent of ENM transformation in the environment, we present a comprehensive and mechanistic structural investigation of the transformation, aggregation, and dissolution behavior of a polyvinylpyrrolidone-coated silver nanoparticle (AgNP) suspension upon sulfidation in moderately reduced hard water with fulvic acid and dissolved Na2S. This reaction is among the most prevalent and industrially and environmentally relevant ENMs transformation. Using ex situ transmission electron microscopy (TEM) and both in situ and ex situ synchrotron-based small angle X-ray scattering (SAXS) and X-ray diffraction (XRD), we find that sulfidation of faceted AgNPs strongly depends on the crystallographic orientation of the facets, with nanometer-scale passivation layers developed on {111} and {100} facets and continuous nucleation and growth on {110} facets. Nanobeam electron diffraction and atomic resolution imaging show Ag and Ag2S domains both possess a high degree of crystalline order, contradicting amorphous structures as previously reported. In situ SAXS/XRD allowed simultaneous determination of the morphological changes and extent of sulfidation of AgNPs. SAXS/XRD results strongly indicate sulfidation follows first-order reaction kinetics without any aggregation. Aided by their size monodispersity, for the first time, using direct, in situ morphology and atomic-structure probes whose results mutually corroborate, we unequivocally determined the sulfidation rate constant of AgNPs under an environmentally relevant condition (≈0.013 min−1 for 68 nm diameter AgNPs). A rigorous analysis of the long-term sulfidation product of the AgNPs under different S/Ag ratios using ex situ SAXS/XRD clearly demonstrates that the silver mass in the original AgNP and transformed Ag/Ag2S NP is preserved. This result has important environmental implications, strongly suggesting that Ag+ ions, a known highly effective antimicrobial agent, are not leached into the solution during sulfidation of AgNPs. The combined nondestructive methodology can be extended to unfold the structure transformation pathway and kinetics in a broad range of ENM systems.

In situ electron microscopy observation of the redox process in plasmonic heterogeneous-photo-sensitive nanoparticles.

Observation of relevant phenomena related with dynamical redox process in a plasmonic heterogeneous-photocatalyst system composed by silver nanoparticles (NPs) around and in contact with amorphous silver chloride NPs are reported by in situ transmission electron microscopy. During this process, nanobubbles are initially produced inside the silver chloride NPs, which immediately begin to move within the amorphous phase. Besides, silver atoms inside the silver chloride NPs start to migrate out the occupied volume leaving a space behind, which is filled by crystalline regions of silver chloride located between the pre-existing silver NPs. During the observation time, fast-nucleation, movement, growth, and fast-dissolution of silver NPs take place. Specific space correlation with silver mass loss (or gain) when a new NP is formed (or dissolved), was detected in different regions during the reaction. This mass loss (or gain) takes place on certain places of pre-existing silver NPs. All these phenomena were observed for a configuration comprising at least two silver NPs separated few nanometers apart by a silver chloride NP.

On the ore provenance of the Trojan silver artefacts

Lead isotopes are a well-established tool to trace the geographic origin of samples and artefacts in archaeology and geochemistry. In archaeology, lead isotopes are often applied to gain information on the provenance of the used ores especially in lead and silver artefacts. The assignment of a specific and unambiguous provenance in most cases is not possible or at least hindered due to several limitations such as ore deposits overlapping in their lead isotopic composition, a large spread within one ore deposit or a missing overlap with known mining sites. Such difficult cases can only be solved by using information from sources being independent of the isotope data. This information can be of chemical nature such as concentrations of key elements or they can be of archaeological nature such as cultural or trade route information. Within this study, we combined lead isotope data of ores and artefacts with silver mass fractions in the ore deposits, Au/Ag-ratios in ores and artefacts and finally archaeological information on the cultural context in the Mediterranean and Anatolian Region. This approach enabled us to significantly reduce the potential number of mining regions. Finally, the potential sources could be narrowed down to the three remaining locations the Central Taurus, Arap Dag and the Eastern Troad. Beneath these three locations, the Central Taurus shows the highest probability for the geographic origin of the galena which has been used to create the Trojan silver artefacts.

Characterisation of silver release from nanoparticle-treated baby products

ABSTRACTWe tested six kinds of commercially available baby products containing nano-silver and divided them into two categories: baby food containers and baby oral care products, according to usage. We measured the total mass of silver, particle size, particle number concentration and the mobility under different simulated conditions. The total mass of silver in baby products and migration solutions was quantified by ICP-MS analysis, and the size of the migrated particles was investigated by single particle ICP-MS and transmission electron microscopy-energy dispersive spectrometer. Nano-silver has different migration behaviour in different materials, and the total mass of silver released in 3% acetic acid was generally highest for plastic material, while highest in 10% ethanol for silicone material. For baby food containers and baby oral care products, the total amount of silver in the migration solutions varied from 2.98 to 126.46 ng/dm2 and from 2.01 to 2.83 ng/g, respectively. The research shows that the use of baby products containing silver may expose babies to silver nanoparticles.

The Structure of Silver Modified Flexible Graphene Electrodes for Actuators in Biomimetic Systems

We present a novel model for semiquantitative estimation of optimal concentrations of silver modifier necessary to increase the conductivity of graphene electrodes in actuators with electroactive polymers and to ensure long-term performance of the system. The model predicts approximately equal masses of silver and graphene in the electrodes after the reduction for the characteristic size of graphene flakes ∼10 nm. Also, the concentration is shown to depend strongly on the size of the flakes.

Four release tests exhibit variable silver stability from nanoparticle-modified reverse osmosis membranes

Modification of polyamide reverse osmosis (RO) membranes with silver nanoparticles (AgNP) may effectively control biofouling. While silver leaching tests are usually performed during membrane development, the lack of common testing protocols limits cross-comparison among different labs. We compare four release tests to quantify the release of dissolved and nanoparticulate silver from polyamide RO membranes prepared through in situ surface functionalization: (1) batch immersion, (2) dead-end filtration, (3) cross-flow filtration, and (4) low-pressure water jetting. For the first time, we demonstrated the possibility of AgNP release to membrane-treated water through direct AgNP detachment. When using Nanopure water as an extraction solution, water jetting resulted in the fastest silver mass release, while dead-end filtration caused the slowest release based on the initial release kinetic data. Dead-end filtration exhibited silver mass release an order of magnitude lower than the other three tests. Although cross-flow filtration may best represent the RO membrane operation, quantifying silver release suffers from poor mass balance due to the adsorption of dissolved silver by various reactor components and large volumes of water usage. A commonly applied batch immersion method was low cost and easily performed, but may not induce hydraulic shear sufficient for AgNP detachment from a RO membrane. The information on silver release behavior may depend on the specific test, which is important for assessing antimicrobial efficacy and service life of the nanoparticle-functionalized membranes.

Toxicological Assessment of a Lignin Core Nanoparticle Doped with Silver as an Alternative to Conventional Silver Core Nanoparticles.

Elevated levels of silver in the environment are anticipated with an increase in silver nanoparticle (AgNP) production and use in consumer products. To potentially reduce the burden of silver ion release from conventional solid core AgNPs, a lignin-core particle doped with silver ions and surface-stabilized with a polycationic electrolyte layer was engineered. Our objective was to determine whether any of the formulation components elicit toxicological responses using embryonic zebrafish. Ionic silver and free surface stabilizer were the most toxic constituents, although when associated separately or together with the lignin core particles, the toxicity of the formulations decreased significantly. The overall toxicity of lignin formulations containing silver was similar to other studies on a silver mass basis, and led to a significantly higher prevalence of uninflated swim bladder and yolk sac edema. Comparative analysis of dialyzed samples which had leached their loosely bound Ag+, showed a significant increase in mortality immediately after dialysis, in addition to eliciting significant increases in types of sublethal responses relative to the freshly prepared non-dialyzed samples. ICP-OES/MS analysis indicated that silver ion release from the particle into solution was continuous, and the rate of release differed when the surface stabilizer was not present. Overall, our study indicates that the lignin core is an effective alternative to conventional solid core AgNPs for potentially reducing the burden of silver released into the environment from a variety of consumer products.

Significance of Trace Element Quantities in Benign and Malignant Giant Cell Tumors of Bone

To clarify the role of trace elements in the etiology and the pathogenesis of benign and malignant giant cell tumor (GCT) of bone, a nondestructive neutron activation analysis with high resolution spectrometry of long-lived radionuclides were performed. The silver (Ag), cobalt (Co), chromium (Cr), iron (Fe), mercury (Hg), rubidium (Rb), antimony (Sb), selenium (Se), and zinc (Zn) mass fraction were measured in three groups of samples: normal bone samples from 27 patients with intact bone (12 females and 15 males), who had died from various non bone related causes, mainly unexpectedly from trauma, and also in samples, obtained from open biopsies or after operation of 10 patients with benign GCT (4 females and 6 males) and 10 patients with malignant GCT (4 females and 6 males). The difference in the results between trace element contents in the three groups was evaluated by the parametric Student’s t-test and non-parametric Wilcoxon-Mann-Whitney U-test. In the bone affected by benign GCT the mean mass fractions of Ag, Co, Fe, Se, and Zn were significantly higher while the mean mass fraction of Rb was lower than in normal bone tissues. In malignant GCT tissue the mean mass fractions of Co, Fe, Sb, and Se were higher while the mean mass fraction of Rb was lower than in normal bone tissue. In malignant GCT tissue only the mean mass fractions of Fe and Rb were higher and the mean mass fractions of Ag and Zn were lower than in benign GCT tissue. Moreover, many correlations between trace elements found in the control group were no longer evident in the neoplastic bone. Thus, considerable changes in trace element content and their relationships were found in benign and malignant GCT and possible causes and effects of these alterations are discussed.

Comparing ex vivo and in vitro translocation of silver nanoparticles and ions through human nasal epithelium

Silver nanomaterials are widely used in clinically approved devices, consumer goods, and over-the-counter nutraceutical products. Despite the increase in silver nanomaterial research, few investigations have specifically distinguished the biological effects resulting from silver nanoparticles (AgNPs) versus silver ions released from AgNPs. This is in part, due to the complex analytical methods required to characterize silver ion release from AgNPs in biological media. This study sought to analyze silver ion release from AgNPs in biological media, compare silver transport from soluble AgNO3 and AgNPs through ex vivo full thickness sinus human tissue explants and human nasal epithelium and determine fractional AgNP internalization by human nasal epithelial cells. Rapid silver ion release is observed from AgNPs in human nasal epithelial cell medium over 3 h (9.6% of total silver mass). Significantly lower translocation of AgNPs is observed through human nasal epithelial cell monolayers and ex vivo human sinus tissue explants compared to silver ion (AgNO3). AgNP internalization is directly observed in AgNP-exposed human nasal epithelial cell monolayers by live cell scanning transmission electron microscopy (STEM), providing one potential mechanism for AgNP transcytosis. However, in vitro AgNP dissolution experiments suggest that silver in human nasal epithelium is primarily silver ion. Ionic AgNO3 produces significantly higher silver translocation, supporting previous results claiming silver ion as primarily responsible for biological effects of AgNPs.

Simultaneous size characterization and mass quantification of the in vivo core-biocorona structure and dissolved species of silver nanoparticles

Size characterization of silver nanoparticles with biomolecule corona (AgNP@BCs) and mass quantification of various silver species in organisms are essential for understanding the in vivo transformation of AgNPs. Herein, we report a versatile method that allows simultaneous determination of the size of AgNP@BCs and mass concentration of various silver species in rat liver. Both particulate and ionic silver were extracted in their original forms from the organs by alkaline digestion, and analyzed by size exclusion chromatography combined with inductively coupled plasma mass spectrometry (SEC-ICP-MS). While the silver mass concentrations were quantified by ICP-MS with a detection limit of 0.1μg/g, the effective diameter of AgNP@BCs was determined based on the retention time in SEC separation with size discrimination of 0.6–3.3nm. More importantly, we found that the BC thickness of AgNP@BCs is core size independent, and a linear correlation was found between the effective diameter and core diameter of AgNP@BCs in extracted tissues, which was used to calibrate the core diameter with standard deviations in the range of 0.2–1.1nm. The utility of this strategy was demonstrated through application to rat livers in vivo. Our method is powerful for investigating the transformation mechanism of AgNPs in vivo.

More than Meets the Eye: Incongruity and Observation in Josephus’s Account of the Triumph of Vespasian and Titus

More than Meets the Eye: Incongruity and Observation in Josephus’s Account of the Triumph of Vespasian and Titus