Nanosilver-based materials as feed additives: Evaluation of their transformations along in vitro gastrointestinal digestion in pigs and chickens by using an ICP-MS based analytical platform

The use of a new nanomaterial in the feed chain requires a risk assessment that involves in vitro gastrointestinal digestions to predict its degradation and oral exposure to nanoparticles. In this study, a nanosilver-based material was incorporated into pig and chicken feed as a growth-promoting additive and subjected to the corresponding in vitro gastrointestinal digestions. An inductively coupled plasma mass spectroscopy (ICP-MS) analytical platform was used to obtain information about the silver released in the different digestion phases. It included conventional ICP-MS for total silver determination, but also single particle ICP-MS and coupling to hydrodynamic chromatography for detection of dissolved and particulate silver. The bioaccessible fraction in the intestinal phase accounted for 8-13% of the total silver, mainly in the form of dissolved Ag(I) species, with less than 0.1% as silver-containing particles. Despite the additive behaving differently in pig and chicken digestions, the feed matrix played a relevant role in the fate of the silver.

Identification and quantification of trace metal(loid)s in water-extractable road dust nanoparticles using SP-ICP-MS

Resuspension of road dust is a major source of airborne particulate matter (PM) in urban environments. Inhalation of ultrafine particles (UFP; < 0.1 μm) represents a health concern due to their ability to reach the alveoli and be translocated into the blood stream. It is therefore important to characterize chemical properties of UFPs associated with vehicle emissions. We investigated the capability of Single-Particle ICP-MS (SP-ICP-MS) to quantify key metal(loid)s in nanoparticles (NPs; < 0.1 μm) isolated from road dust collected in Toronto, Canada. Water extraction was performed to separate the <1-μm fraction from two different road dust samples (local road vs. arterial road) and a multi-element SP-ICP-MS analysis was then conducted on the samples' supernatants. Based on the particle number concentrations obtained for both supernatants, the metal(loid)-containing NPs could be grouped in the following categories: high (Cu and Zn, > 1.3 × 1011 particles/L), medium (V, Cr, Ba, Pb, Sb, Ce, La), low (As, Co, Ni, < 4.6 × 109 particles/L). The limit of detection for particle number concentration was below 5.5 × 106 particles/L for most elements, except for Cu, Co, Ni, Cr, and V (between 0.9 and 7.7 × 107 particles/L). The results demonstrate that road dust contains a wide range of readily mobilizable metal(loid)-bearing NPs and that NP numbers may vary as a function of road type. These findings have important implications for human health risk assessments in urban areas. Further research is needed, however, to comprehensively assess the NP content of road dust as influenced by various factors, including traffic volume and speed, fleet composition, and street sweeping frequency. The described method can quickly characterize multiple isotopes per sample in complex matrices, and offers the advantage of rapid sample scanning for the identification of NPs containing potentially toxic transition metal(loid)s at a low detection limit.

Validation of a Method for Surveillance of Nanoparticles in Mussels Using Single Particle Inductively Coupled Plasma Mass Spectrometry

BACKGROUND

Determining the concentration of nanoparticles in marine organisms is important for evaluating their environmental impact and to assess potential food safety risks to human health.

OBJECTIVE

The current work aimed at developing an in-house method based on single particle inductively coupled plasma mass spectrometry suitable for surveillance of nanoparticles in mussels.

METHOD

A new low-cost and simple protease mixture was utilized for sample digestion, and a novel open-source data processing was used, establishing detection limits on a statistical basis using false positive and false negative probabilities. The method was validated for 30 and 60 nm gold nanoparticles spiked to mussels as a proxy for seafood.

RESULTS

Recoveries were 76-77% for particle mass concentration and 94-101% for particle number concentration. Intermediate precision was 8-9% for particle mass concentration and 7-8% for particle number concentration. Detection limits for size was 18 nm and for concentration 1.7 ng/g and 4.2 x 105 particles/g mussel tissue.

CONCLUSION

The performance characteristics of the method were satisfying compared with numeric Codex criteria. Further, the method was applied to titanium-, chromium- and copper-based particles in mussels.

HIGHLIGHTS

The method demonstrates a new practical and cost-effective sample treatment and streamlined, transparent and reproducible data treatment for the routine surveillance of NPs in mussels.

Fate and distribution of orally-ingested CeO2-nanoparticles based on a mouse model: Implication for human health

The use of nanoparticles in agrichemical formula and food products as additives has increased their chances of accumulation in humans via oral intake. Due to their potential toxicity, it is critical to understand their fate and distribution following oral intake. Cerium oxide nanoparticle (CeO2NP) is commonly used in agriculture and is highly stable in the environment. As such, it has been used as a model chemical to investigate nanoparticle's distribution and clearance. Based on their estimated human exposure levels, 0.15-0.75 mg/kg body weight/day of CeO2NPs with different sizes and surface charges (30-50 nm with negative charge and <25 nm with positive charge) were gavaged into C57BL/6 female mice daily. After 10-d, 50% of mice in each treatment were terminated, with the remaining being gavaged with 0.2 mL of deionized water daily for 7-d. Mouse organ tissues, blood, feces, and urine were collected at termination. At the tested levels, CeO2NPs displayed minimal overt toxicity to the mice, with their accumulation in various organs being negligible. Fecal discharge as the predominant clearance pathway took less than 7-d regardless of charges. Single particle inductively coupled plasma mass spectrometry analysis demonstrated minimal aggregation of CeO2NPs in the gastrointestinal tract. These findings suggest that nanoparticle additives >25 nm are unlikely to accumulate in mouse organ after oral intake, indicating limited impacts on human health.

Tracking soluble and nanoparticulated titanium released in vivo from metal dental implant debris using (single-particle)-ICP-MS

BACKGROUND

This work studies the presence of the Ti, Al and V metal ions and Ti nanoparticles released from the debris produced by the implantoplasty, a surgical procedure used in the clinic, in rat organs.

METHODS

The sample preparation for total Ti determination was carefully optimized using microsampling inserts to minimize the dilution during the acid attack of the lyophilized tissues by a microwave-assisted acid digestion method. An enzymatic digestion method was optimized and applied to the different tissue samples in order to extract the titanium nanoparticles for the single-particle ICP-MS analysis.

RESULTS

A statistically significant increase was found for Ti concentrations from control to experimental groups for several of the studied tissues, being and particularly significant in the case of brain and spleen. Al and V concentrations were detected in all tissues but they were not different when comparing control and experimental animals, except for V in brain. The possible presence of Ti-containing nanoparticles mobilized from the implantoplasty debris was tested using enzymatic digestions and SP-ICP-MS. The presence of Ti-containing nanoparticles was observed in all the analyzed tissues, however, differences on the Ti mass per particle were found between the blanks and the digested tissue and between control and experimental animals in some organs.

CONCLUSION

The developed methodologies, both for ionic and nanoparticulated metal contents in rat organs, have shown the possible increase in the levels of Ti both as ions and nanoparticles in rats subjected to implantoplasty.

Single particle ICP-MS combined with filtration membrane for accurate determination of silver nanoparticles in the real aqueous environment

This work presents the role of commercial microfiltration membranes combined with single particle inductively coupled plasma-mass spectrometry (SP-ICP-MS) in removing environmental matrix interference for model silver nanoparticles (AgNPs) determination. The filters with different pore sizes (0.22 μm, 0.45 μm, 0.8 μm) and materials (mixed cellulose ester, polyether sulfone, and nylon) were investigated to acquire the recovery of particle concentration and size of AgNPs spiked into different real aqueous solutions, including ultrapure water, tap water, surface water, and sewage effluent. The maximum recovery of nanoparticle concentration was 70.2% through the 0.8 μm polyether sulfone membrane. The heated filters were able to improve the recovery of AgNPs particle concentration in the real aqueous environment. Hence, the pretreatment method by SP-ICP-MS combined with filtration membrane was simple, fast, and low-cost to quantify AgNPs in natural water environments.

Vertical distribution of inorganic nanoparticles in a Norwegian fjord

Due to the analytical challenges of detecting and quantifying nanoparticles in seawater, the data on distributions of NPs in the marine environment is limited to qualitative studies or by ensemble measurements subject to various analytical artifacts. Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) allows determination of individual inorganic NPs at environmentally relevant concentrations, yet only few studies have been conducted on selected elements in surface sea water. Here, a sequential multi-element screening method was developed and implemented to provide a first survey of the horizontal and vertical distributions of inorganic nanoparticles and trace elements in a pristine Norwegian fjord prospect for submarine tailings deposition. Statistical control of false-positive detections while minimizing the size detection limit was ensured using a novel raw signal processing. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) gave confirmative and qualitative information regarding particle morphology and composition. Following SP-ICP-MS screening for particles of 16 elements, particulate Al, Fe, Mn, Pb, Si and Ti were found and determined to mass concentrations in ng/L of 1-399, 1-412, below limit of detection (<LOD) - 269, <LOD - 1, <LOD - 1981 and <LOD - 127 ng/L with particle number concentrations up to 10⁸ particles per liter. Total metals concentrations were at least an order of magnitude higher, at concentrations in μg/L of 1-12 for Al, 2-13 for Fe, 0.3-11 Mn, 0.02-0.5 for Pb, 46 to 318 Si and 0.04-0.4 for Ti. A strong depth dependence was observed for both trace elements and particles with concentrations increasing with depth. Our results provide a baseline for the fjord and new data on environmental levels of both total metals and metal containing nanoparticles including the vertical and horizontal distribution of natural nanoparticles.

Towards Automated and High-Throughput Quantitative Sizing and Isotopic Analysis of Nanoparticles via Single Particle-ICP-TOF-MS

The work described herein assesses the ability to characterize gold nanoparticles (Au NPs) of 50 and 100 nm, as well as 60 nm silver shelled gold core nanospheres (Au/Ag NPs), for their mass, respective size, and isotopic composition in an automated and unattended fashion. Here, an innovative autosampler was employed to mix and transport the blanks, standards, and samples into a high-efficiency single particle (SP) introduction system for subsequent analysis by inductively coupled plasma-time of flight-mass spectrometry (ICP-TOF-MS). Optimized NP transport efficiency into the ICP-TOF-MS was determined to be >80%. This combination, SP-ICP-TOF-MS, allowed for high-throughput sample analysis. Specifically, 50 total samples (including blanks/standards) were analyzed over 8 h, to provide an accurate characterization of the NPs. This methodology was implemented over the course of 5 days to assess its long-term reproducibility. Impressively, the in-run and day-to-day variation of sample transport is assessed to be 3.54 and 9.52% relative standard deviation (%RSD), respectively. The determination of Au NP size and concentration was of <5% relative difference from the certified values over these time periods. Isotopic characterization of the ¹⁰⁷Ag/¹⁰⁹Ag particles (n = 132,630) over the course of the measurements was determined to be 1.0788 ± 0.0030 with high accuracy (0.23% relative difference) when compared to the multi-collector-ICP-MS determination.

Extraction and quantification of polystyrene nanoplastics from biological samples

Accurate quantification of nanoplastics (NPs) in complex matrices remains a challenge, especially for biological samples containing high content of organic matters. Herein, a new method extracting and quantifying polystyrene (PS) NPs from biological samples was developed. The extraction included alkaline digestion, centrifugation, and cloud point extraction (CPE), and the quantification included gold nanoparticles formation and labeling on surfaces of the extracted NPs and thereafter measurement with single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). Results show that 25% tetramethylammonium hydroxide solution was an effective alkaline digestion solution for biological matrices, and CPE after centrifugation (3000 rpm, 10 min) was applicable to purify and enrich PS NPs with different sizes (100 and 500 nm) and surface functionalities (-COOH and -NH₂ modifications) from the digestion solution. The efficiency of Au labeling on PS NPs surface was improved by about 70% in the presence of 100 μM cetyltrimethylammonium bromide. The performance of the quantification method was examined by extraction and measurement of PS NPs spiked in four representative organism samples including bacteria, algae, nematode, and earthworm, and was further validated by analyzing the accumulated PS NPs in exposed nematodes. Good recovery rates (65 ± 10%-122 ± 22%) were achieved for spiking levels of 5-50 μg g^-1; the limit of detection was 3.7 × 10⁷ particles g^-1, corresponding to the mass concentration of about 0.02 and 2.5 μg g^-1 for the 100 nm and 500 nm PS NPs, respectively. The established extraction and quantification methods are efficient and sensitive, providing a useful approach for further exploring the environmental behavior and toxicity of NPs.

How to trust size distributions obtained by single particle inductively coupled plasma mass spectrometry analysis

Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) is a technique widely used to obtain direct information about the number concentration and the size distribution of nanoparticles in liquid suspensions. However, its methods still lack clear quality control strategies to confirm the validity of the information derived from them. Only the detection of the complete size distribution of the nanoparticles in a sample over the size critical value ensures obtaining unbiased quantitative information, otherwise information should be restricted to report the presence of nanoparticles over a certain size and number concentration since their actual total number concentration is underestimated and the size overestimated. Under the latter conditions, data processing produces histograms showing the tails of the incomplete size distributions, although apparently, complete distributions can also be obtained when particle events are recorded as peaks, as reported here for the first time. The occurrence of these misleading situations must be critically evaluated for each SP-ICP-MS analysis. An approach, based on estimation of size critical values and successive dilutions, is proposed for the assessment of the validity of the quantitative information obtained, together with specific criteria for reconsidering the information that can be derived from those measurements. The approach was verified with different case studies and applied to the analysis of complex nanomaterials, confirming the validity of the reported information by comparison with other techniques. A calculation tool is also included to facilitate the estimation of size critical values under experimental conditions.

Evaluation of collision/reaction gases in single-particle ICP-MS for sizing selenium nanoparticles and assessment of their antibacterial activity

Selenium nanoparticles (SeNPs) have recently attracted attention because they combine the benefits of Se and lower toxicity compared to other chemical forms of this element. In this study, SeNPs were synthesized by a green method using ascorbic acid as the reducing agent and polyvinyl alcohol as stabilizer. The nanoparticles were widely characterized. To determine the total concentration of Se by ICP-MS, several isotopes and the use of He as collision gas were evaluated, which was effective in minimizing interferences. A method for sizing SeNPs by single particle ICP-MS (SP-ICP-MS) was developed. For this purpose, He and H₂were evaluated as collision/reaction gases, and the second one showed promising results, providing an average diameter of 48 nm for the SeNPs. These results agree with those obtained by TEM (50.1 nm). Therefore, the SP-ICP-MS can be implemented for characterizing SeNPs in terms of size and size distribution, being an important analytical tool for Se and other widely studied nanoparticles (e.g. Ag, Au, Ce, Cu, Fe, Zn). Finally, the antibacterial activity of SeNPs was assessed. The SeNPs showed bacteriostatic activity against three strains of Gram-positive bacteria and were particularly efficient in inhibiting the growthE. faecaliseven at very low concentrations (MIC < 1.4 mg l^-1). In addition, a bactericidal activity of SeNPs againstS. aureuswas observed. These nanoparticles may have potential application in pharmaceutical industry, biomedicine and agriculture.

Detection, Identification and Size Distribution of Silver Nanoparticles (AgNPs) in Milk and Migration Study for Breast Milk Storage Bags

The engineered silver nanoparticles (AgNPs) have been widely used in various food contact materials (FCMs) based on their antibacterial properties. This widespread use of nanosilver has, however, increased the risk of exposure of AgNPs to human due to their migration from FCMs causing a potential hazard present in foods. Therefore, it is important to establish a reliable and practical method for the detection of AgNPs in food matrices to support risk assessment on AgNPs exposure. Taking the examples of milk and AgNPs-containing breast milk storage bags, this study established an approach for size characterization and quantification of AgNPs in milk and evaluated the relevant silver migration, based on enzymatic digestion and the analysis by asymmetric flow field–flow fractionation (AF4) hyphenated with inductively coupled plasma mass spectrometry (ICP-MS) and single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). No migration of AgNPs was found from breast milk storage bags under various simulated storage conditions as well as extreme scenarios. The suitability and reliability of this method were also validated by the determination of multiple parameters, including accuracy, repeatability, limit of detection (LOD), limit of quantification (LOQ), and recovery, for AF4-ICP-MS and SP-ICP-MS, respectively, with good and overall acceptable evaluation results obtained for all. The established and validated approach was demonstrated to be suitable for the characterization and quantitation of AgNPs in milk as well as the analysis of their migration from breast milk storage bags.

Preliminary studies of the impact of food components on nutritional properties of nanoparticles

Nowadays consumers have constantly exposed to nanoparticles (NPs) ingestion. Although the impact of NPs on the human has been studied by many authors, they did not consider the influence of food matrix components on bioaccessibility of NPs. This fact has encouraged us to investigate the influence of different food components on NPs. The investigation has been carried out to assess the influence of main food components on the MNPs (metallic nanoparticles) fate during the in vitro gastrointestinal simulation. The experiments have been carried out with the single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) as a tool for quantitative and qualitative analysis and the scanning transmission electron microscopy (STEM) as a means of qualitative analysis. The influence of various food components on NPs has been confirmed and it may be concluded that the matrix has an impact on the size and form of NPs. The presence of food components significantly changes the behaviour of NPs during simulated gastrointestinal digestion. Possible explanations of the influence of main nutrient groups, i.e. lipids, protein, salts, saccharides and vitamins on NPs have been proposed.

Use of single particle inductively coupled plasma mass spectrometry for understanding the formation of bimetallic nanoparticles

Bimetallic nanoparticles (NPs), including core-shell structure and bimetallic alloy nanoparticles, were synthesized and characterized using flow field-flow fractionation (FlFFF), single particle inductively coupled plasma mass spectrometry (SP-ICP-MS), and transmission electron microscope (TEM) with energy-dispersive x-ray spectroscopy (EDS). For the core-shell particles, a nominal 80 nm commercial core-shell AuAg bimetallic nanoparticle was used to examine the applicability of SP-ICP-MS to determine the core size of Au and shell thickness of Ag. Then, the method was applied to estimate the core size of Au and shell thickness of Ag for the laboratory synthesized particles. The results were compared with those obtained from TEM-EDS. For the alloy nanoparticles, two synthesis protocols, based on the galvanic replacement of Ag seed particles with Au, were used. One was to prepare a hollow AgAu particle by varying the volume of dissolved Au in basic solution (K-gold) to etch some parts of AgNPs to dissolved ionic silver with the formation of AuNPs covering the remaining AgNPs, producing a hole inside the core nanoparticles. Another protocol was to prepare AgAu alloy nanoparticles. SP-ICP-MS was used in combination with FlFFF to provide information on the changes of particle size with varying volume of K-gold reagent. Hydrodynamic diameter increased with increasing K-gold, as observed by FlFFF. With SP-ICP-MS without prior FlFFF, bimodal distributions were observed in the size distribution of Au and Ag. With prior FlFFF, monomodal distributions were observed by SP-ICP-MS, which allow the use of particle concentration and size to estimate the mass concentration of elements on the fractionated bimetallic nanoparticles. This study illustrates the potential use of SP-ICP-MS for gaining information about particle transformation during the synthesis of bimetallic nanoparticles.

A homogeneous nucleic acid assay for simultaneous detection of SARS-CoV-2 and influenza A (H3N2) by single-particle inductively coupled plasma mass spectrometry

In recent years, single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) has become a powerful tool for biological quantitative analysis. Homogeneous analysis method requires no separation and washing steps, which is suited for the analysis of highly infectious pathogens, so as to reduce the risk of infection during the operation. SARS-CoV-2 spreads all over the world, and its early infection symptoms are similar to influenza, which brings inconvenience to triage. Therefore, developing novel analytical method for simultaneous detection of multiple viral nucleic acids is essential. Taking the advantages of SP-ICP-MS and homogeneous analysis strategy, a SP-ICP-MS homogeneous nucleic acid assay by using gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs) probes was established for simultaneous sensitive analysis of SARS-CoV-2 and influenza A (H3N2). In the present of target SARS-CoV-2 or H3N2 nucleic acids, corresponding Au NPs or Ag NPs probes form larger aggregates, resulting in increased pulse signal intensity and reduced pulse signal frequency of the corresponding NPs in SP-ICP-MS measurement. In this assay, the reaction system of Au NPs and Ag NPs probes does not interfere with each other, and there was no separation and washing procedure, which facilitates operation, saves the analysis time, and improves the analysis efficiency. The linear range of this method is 5-1000 pmol L^-1, with low-level limits of quantification of target nucleic acid. The developed SP-ICP-MS simultaneous homogeneous detection method has a good potential for detecting nucleic acid, protein, cell and other biological samples by changing different modification sequences on the NPs probes.

Use of single particle ICP-MS to estimate silver nanoparticle penetration through baby porcine mucosa

Children are potentially exposed to products that contain nanoparticles (NPs). In particular, silver NPs are commonly present both in products used by and around children, primarily due to their antibacterial properties. However, very few data are available regarding the ability of silver NPs to penetrate through the oral mucosa in children. In the present work, we used baby porcine buccal mucosa mounted on vertical Franz diffusion cells, as an in vitro model to investigate penetration of silver NPs (19 ± 5 nm). Permeability experiments were performed using pristine physiologically-relevant saline solution in the receiver chamber and known concentrations of NPs or ions in the donor chamber; conditions mimicked the in vivo physiological pH conditions. After physicochemical characterization of silver nanoparticles dispersed in physiological solution, we evaluated the passage of ions and NPs through the mucosa, using single particle inductively coupled plasma mass spectrometry. A flux of 4.1 ± 1.7 ng cm^-2min^-1 and a lag time of 159 ± 17 min were observed through mucosa exposed to silver nanoparticles. The latter suggests nanoparticle penetration through the baby porcine mucosa and release Ag⁺ ions in the receptor fluid, as confirmed by computational model. Due to physiological similarity between human and pig membranes it is reasonable to assume that a trans-oral mucosa penetration could occur in children upon contact with silver nanoparticles.

Simple Method for the Extraction and Determination of Ti-, Zn-, Ag-, and Au-Containing Nanoparticles in Sediments Using Single-Particle Inductively Coupled Plasma Mass Spectrometry

The quantitative analysis of nanoparticles (NPs) in the environment is significantly important for the exploration of the occurrence, fate, and toxicological behaviors of NPs and their subsequent environmental risks. Some protocols have been recommended for the separation and extraction of NPs that are potentially dispersed in complex environmental matrixes, e.g. sediments and soils, but they remain limited. However, certain factors that may significantly affect extraction efficiency have not been comprehensively explored. In this study, on the basis of the single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) technique, a simple standardized protocol for separating and analyzing metal-containing NPs in sediment samples was developed. On consideration of the extraction efficiencies of indigenous NPs (Ti- and Zn-NPs) and spiked NPs (Ag- and Au-NPs) in sediments, sedimentation with a settling time of 6 h is recommended for the separation of NPs and large particles, and the optimal sediment to water ratio, ultrasonication power, time, and temperature are 0.4 mg/mL, 285 W, 20 min, and 15-25 °C, respectively. On the basis of the optimized method, the recoveries of spiked Ag and Au-NPs were 71.4% and 81.1%, respectively. The applicability of the optimal protocols was verified, and TOC was proved to be an important factor controlling the separation and extraction of NPs in environmental samples. The separation and extraction of NPs in elevated TOC samples can be improved by increasing the ultrasonication power, time, and temperature.

Metal-Containing Nanoparticles in Low-Rank Coal-Derived Fly Ash from China: Characterization and Implications toward Human Lung Toxicity

Characterization of nanoparticles (NPs) in coal fly ashes (CFAs) is critical for better understanding the potential health-related risks resulting from coal combustion. Based on single-particle (SP)-inductively coupled plasma mass spectrometry (ICP-MS) coupled with transmission electron microscopy techniques, this study is the first to determine the concentrations and sizes of metal-containing NPs in low-rank coal-derived fly ashes. Despite only comprising a minor component of the studied CFAs by mass, NPs were the dominant fraction by particle number. Fe- and Ti-containing NPs were identified as the dominant NPs with their particle number concentration ranging from 2.5 × 10⁷ to 2.5 × 10⁸ particles/mg. In addition, the differences of Fe-/Ti-containing NPs in various CFAs were regulated by the coalification degree of feed coals and combustion conditions of all of the low-rank CFAs tested. In the cases where these NPs in CFAs become airborne and are inhaled, they can be taken up in pulmonary interstitial fluids. This study shows that in Gamble's solution (a lung fluid simulant), 51-87% of Fe and 63-89% of Ti (ratio of the mass of Fe-/Ti-containing NPs to the total mass of Fe/Ti) exist in the NP form and remain suspended in pulmonary fluid simulants. These NPs are bioavailable and may induce lung tissue damage.

Analysis of cerium oxide and copper oxide nanoparticles bioaccessibility from radish using SP-ICP-MS

BACKGROUND

The transformation of nanoparticles (NPs) internalized in plant tissues is the human digestive system that can provide a better understanding of the impact of NPs on the human system. The presented methodology was developed to study the bioaccessibility of cerium oxide (CeO₂ ) and copper oxide (CuO) NPs from radish after the in vitro simulation of gastrointestinal digestion using single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS).

RESULTS

Radish plants were cultivated hydroponically in a growth medium containing: (i) CeO₂ NPs and (ii) CuO NPs. Both cerium (Ce) and copper (Cu) were found in all organs of the radish plants after analysis by standalone ICP-MS. This confirms the bioaccumulation of CeO₂ and CuO NPs and the translocation of their Ce and Cu to the aerial parts of the plant. Less Ce (4.095 μg g^-1 ) has been detected in leaves than in roots (1.156 mg g^-1 ) while Cu content in leaves was 5.245 μg g^-1 and in roots was 10.41 μg g^-1 . Analysis of the digestive extracts obtained after the in vitro simulation of gastro (pepsin) and gastrointestinal (pancreatin) digestion showed that Ce has easy access to human system at least by 73%.

CONCLUSION

The size of CeO₂ NPs in digestive extracts showed no significant changes. However, the results obtained for CuO NPs digestion were variable and suggested that CuO NPs dissolved during the digestion process. The CuO NPs were observed in roots after the gastrointestinal digestion concluding that CuO NPs recovered after the initial dissolution. © 2020 Society of Chemical Industry.

Effects of environmentally relevant concentrations of mixtures of TiO2, ZnO and Ag ENPs on a river bacterial community

Effluent from wastewater treatment plants contains a wide variety of engineered nanoparticles (ENPs) released from different sources. Although single type ENPs have been studied extensively with respect to their environmental impact, ENPs in mixed forms have not been investigated much at environmentally relevant concentrations. This study was designed to test the effect of mixed ENPs at three combinations and concentrations on an aquatic bacterial community. After mixing artificial treated wastewater with river water and exposing the microbial community to ENPs for three days, the ENPs were characterized by SP-ICP-MS. Results from this study showed that: 1) the size distribution of Ti and Zn at the beginning and end of the experiment did not vary much among all tested conditions. For Ag, the most frequent size increased more than 2-fold when the highest Ag ENPs were added; 2) particle concentrations of ENPs generally correlated positively with added concentrations; 3) dissolved Zn and Ag increased significantly as a result of spike; and 4) the bacterial community structure was shifted significantly as a consequence of ENPs' addition. With the dominant population being suppressed, the community exposed to ENPs became more diverse and even. Surprisingly, further increase of the doses of the three ENPs did not bring significant change to the microbial community. These results revealed that ENPs could bring significant impacts to prokaryotes even at low concentrations. But these impacts do not necessarily correlate positively with doses.

Human primary macrophages scavenge AuNPs and eliminate it through exosomes. A natural shuttling for nanomaterials

The use of nanomaterials is increasing but the real risk associated with their use in humans has to be defined. In fact, nanomaterials tend to accumulate in organs over a long period of time and are slowly degraded or eliminated by the body. Exosomes are nanovesicles actively shuttle molecules, including chemical products and metals, through the body. Macrophages scavenge the body from both organic and inorganic substances, and they use to release high amounts of exosomes. We hypothesized that macrophages may have a role in eliminating nanomaterials through their exosomes. We treated human primary macrophages with 20 nm gold nanoparticles (AuNPs), analyzing the presence of AuNPs in both cells and the released exosomes by the implementation of different techniques, including SP-ICP-MS and NTA. We showed that macrophages endocytosed AuNPs and released them through exosomes. Our study on one hand provide the evidence for a new methodology in the early identification of the nanomaterials levels in exposed subjects. On the other hand we depict a way our body shuttle virtually intact nanoparticles through macrophage-released exosomes.

Study of the presence of micro- and nanoparticles in drinks and foods by multiple analytical techniques

A variety of food and drink samples (n = 21) were analyzed to evaluate the presence of (nano-) particles in their composition. After assessment of the sample pre-treatment step, a fast screening analysis was performed for drinks by Dynamic Light Scattering showing particles from 10 to 300 nm that could correspond to organic or metallic NPs. Metallic NPs were identified in foods by Single-Particle mode Inductively Coupled Plasma Mass Spectrometry and Asymmetrical Flow Field-Flow Fractionation coupled to Multiangle Laser Light Scattering and Inductively-Coupled Plasma Mass Spectrometry. The determination of Ti, Si and Ag concentration in the initial food suspensions, after filtration and centrifugal ultrafiltration enabled to estimate the ionic and nanoparticles content. Si-containing particles can be present in cappuccino powder as large aggregates and Si- and Al-containing particles in hot chocolate. Ti-containing NPs (80-200 nm) were found in chewing gum and Ag NPs in silver pearls (50-150 nm) used for decoration pastry.

Cellular imaging and bactericidal mechanism of green-synthesized silver nanoparticles against human pathogenic bacteria

In recent years, silver nanoparticles (AgNPs) have attracted significant attention in medicinal, biomedical, and pharmaceutical research owing to their valuable physicochemical and antibacterial properties. Leaf sap extract (LSE) from Aloe arborescens can be used as an active ingredient for different biological applications, including wound healing. In this study, we have investigated the use of LSE from A. arborescens as a reducing, stabilizing and capping agent to produce AgNPs during the so called "green synthesis" (G-AgNPs). The objective of this study was to prepare, characterize and evaluate the potential of G-AgNPs against human pathogenic bacteria for the intended use as treatment of infected wounds. When the mixture of silver nitrate solution and LSE was exposed to direct sunlight it yielded a rapid color change from colorless to reddish-brown, indicating the formation of G-AgNPs. Physicochemical characterization such as Single particle inductively coupled plasma mass spectrometry, High resolution transmission electron microscopy and surface chemistry studies (Fourier transform infrared spectroscopy and X-Ray diffraction) revealed a small size in the range of 38±2nm, smooth surface and existence of LSE on the G-AgNPs. G-AgNPs possessed good antibacterial activity against both Pseudomonas aeruginosa and Staphylococcus aureus. The flow cytometry study revealed the increased percentage of dead cells treated by G-AgNPs through cell membrane damage, and it was further confirmed by confocal laser scanning microscopy. Thus, the present study reveals that the novel G-AgNPs demonstrated effective antibacterial properties against both Gram-negative and Gram-positive bacterial strains and shows great potential for its use in the treatment of pathogen infected wounds.

Evaluation of number concentration quantification by single-particle inductively coupled plasma mass spectrometry: microsecond vs. millisecond dwell times

The quality of the quantitative information in single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) depends directly on the number concentration of the nanoparticles in the sample analyzed, which is proportional to the flux of nanoparticles through the plasma. Particle number concentrations must be selected in accordance with the data acquisition frequency, to control the precision from counting statistics and the bias, which is produced by the occurrence of multiple-particle events recorded as single-particle events. With quadrupole mass spectrometers, the frequency of data acquisition is directly controlled by the dwell time. The effect of dwell times from milli- to microseconds (10 ms, 5 ms, 100 μs, and 50 μs) on the quality of the quantitative data has been studied. Working with dwell times in the millisecond range, precision figures about 5 % were achieved, whereas using microsecond dwell times, the suitable fluxes of nanoparticles are higher and precision was reduced down to 1 %; this was independent of the dwell time selected. Moreover, due to the lower occurrence of multiple-nanoparticle events, linear ranges are wider when dwell times equal to or shorter than 100 μs are used. A calculation tool is provided to determine the optimal concentration for any instrument or experimental conditions selected. On the other hand, the use of dwell times in the microsecond range reduces significantly the contribution of the background and/or the presence of dissolved species, in comparison with the use of millisecond dwell times. Although the use of dwell times equal to or shorter than 100 μs offers improved performance working in single-particle mode, the use of conventional dwell times (3-10 ms) should not be discarded, once their limitations are known.

Characterization of Silver Nanoparticles Internalized by Arabidopsis Plants Using Single Particle ICP-MS Analysis

Plants act as a crucial interface between humans and their environment. The wide use of nanoparticles (NPs) has raised great concerns about their potential impacts on crop health and food safety, leading to an emerging research theme about the interaction between plants and NPs. However, up to this day even the basic issues concerning the eventual fate and characteristics of NPs after internalization are not clearly delineated due to the lack of a well-established technique for the quantitative analysis of NPs in plant tissues. We endeavored to combine a quantitative approach for NP analysis in plant tissues with TEM to localize the NPs. After using an enzymatic digestion to release the NPs from plant matrices, single particle-inductively coupled plasma-mass spectrometry (SP-ICP-MS) is employed to determine the size distribution of silver nanoparticles (Ag NPs) in tissues of the model plant Arabidopsis thaliana after exposure to 10 nm Ag NPs. Our results show that Macerozyme R-10 treatment can release Ag NPs from Arabidopsis plants without changing the size of Ag NPs. The characteristics of Ag NPs obtained by SP-ICP-MS in both roots and shoots are in agreement with our transmission electron micrographs, demonstrating that the combination of an enzymatic digestion procedure with SP-ICP-MS is a powerful technique for quantitative determination of NPs in plant tissues. Our data reveal that Ag NPs tend to accumulate predominantly in the apoplast of root tissues whereby a minor portion is transported to shoot tissues. Furthermore, the fact that the measured size distribution of Ag NPs in plant tissue is centered at around 20.70 nm, which is larger than the initial 12.84 nm NP diameter, strongly implies that many internalized Ag NPs do not exist as intact individual particles anymore but are aggregated and/or biotransformed in the plant instead.