Biokinetics and effects of barium sulfate nanoparticles

Metal and oxidative potential exposure through particle inhalation and oxidative stress biomarkers: a 2-week pilot prospective study among Parisian subway workers

OBJECTIVE

In this pilot study on subway workers, we explored the relationships between particle exposure and oxidative stress biomarkers in exhaled breath condensate (EBC) and urine to identify the most relevant biomarkers for a large-scale study in this field.

METHODS

We constructed a comprehensive occupational exposure assessment among subway workers in three distinct jobs over 10 working days, measuring daily concentrations of particulate matter (PM), their metal content and oxidative potential (OP). Individual pre- and post-shift EBC and urine samples were collected daily. Three oxidative stress biomarkers were measured in these matrices: malondialdehyde (MDA), 8-hydroxy-2'deoxyguanosine (8-OHdG) and 8-isoprostane. The association between each effect biomarker and exposure variables was estimated by multivariable multilevel mixed-effect models with and without lag times.

RESULTS

The OP was positively associated with Fe and Mn, but not associated with any effect biomarkers. Concentration changes of effect biomarkers in EBC and urine were associated with transition metals in PM (Cu and Zn) and furthermore with specific metals in EBC (Ba, Co, Cr and Mn) and in urine (Ba, Cu, Co, Mo, Ni, Ti and Zn). The direction of these associations was both metal- and time-dependent. Associations between Cu or Zn and MDAEBC generally reached statistical significance after a delayed time of 12 or 24 h after exposure. Changes in metal concentrations in EBC and urine were associated with MDA and 8-OHdG concentrations the same day.

CONCLUSION

Associations between MDA in both EBC and urine gave opposite response for subway particles containing Zn versus Cu. This diverting Zn and Cu pattern was also observed for 8-OHdG and urinary concentrations of these two metals. Overall, MDA and 8-OHdG responses were sensitive for same-day metal exposures in both matrices. We recommend MDA and 8-OHdG in large field studies to account for oxidative stress originating from metals in inhaled particulate matter.

Modular air-liquid interface aerosol exposure system (MALIES) to study toxicity of nanoparticle aerosols in 3D-cultured A549 cells in vitro

We present a novel lung aerosol exposure system named MALIES (modular air-liquid interface exposure system), which allows three-dimensional cultivation of lung epithelial cells in alveolar-like scaffolds (MatriGrids®) and exposure to nanoparticle aerosols. MALIES consists of multiple modular units for aerosol generation, and can be rapidly assembled and commissioned. The MALIES system was proven for its ability to reliably produce a dose-dependent toxicity in A549 cells using CuSO4 aerosol. Cytotoxic effects of BaSO4- and TiO2-nanoparticles were investigated using MALIES with the human lung tumor cell line A549 cultured at the air-liquid interface. Experiments with concentrations of up to 5.93 × 105 (BaSO4) and 1.49 × 106 (TiO2) particles/cm3, resulting in deposited masses of up to 26.6 and 74.0 µg/cm2 were performed using two identical aerosol exposure systems in two different laboratories. LDH, resazurin reduction and total glutathione were measured. A549 cells grown on MatriGrids® form a ZO-1- and E-Cadherin-positive epithelial barrier and produce mucin and surfactant protein. BaSO4-NP in a deposited mass of up to 26.6 µg/cm2 resulted in mild, reversible damage (~ 10% decrease in viability) to lung epithelium 24 h after exposure. TiO2-NP in a deposited mass of up to 74.0 µg/cm2 did not induce any cytotoxicity in A549 cells 24 h and 72 h after exposure, with the exception of a 1.7 fold increase in the low exposure group in laboratory 1. These results are consistent with previous studies showing no significant damage to lung epithelium by short-term treatment with low concentrations of nanoscale BaSO4 and TiO2 in in vitro experiments.

Radiopacity Enhancements in Polymeric Implant Biomaterials: A Comprehensive Literature Review

Polymers as biomaterials possess favorable properties, which include corrosion resistance, light weight, biocompatibility, ease of processing, low cost, and an ability to be easily tailored to meet specific applications. However, their inherent low X-ray attenuation, resulting from the low atomic numbers of their constituent elements, i.e., hydrogen (1), carbon (6), nitrogen (7), and oxygen (8), makes them difficult to visualize radiographically. Imparting radiopacity to radiolucent polymeric implants is necessary to enable noninvasive evaluation of implantable medical devices using conventional imaging methods. Numerous studies have undertaken this by blending various polymers with contrast agents consisting of heavy elements. The selection of an appropriate contrast agent is important, primarily to ensure that it does not cause detrimental effects to the relevant mechanical and physical properties of the polymer depending upon the intended application. Furthermore, its biocompatibility with adjacent tissues and its excretion from the body require thorough evaluation. We aimed to summarize the current knowledge on contrast agents incorporated into synthetic polymers in the context of implantable medical devices. While a single review was found that discussed radiopacity in polymeric biomaterials, the publication is outdated and does not address contemporary polymers employed in implant applications. Our review provides an up-to-date overview of contrast agents incorporated into synthetic medical polymers, encompassing both temporary and permanent implants. We expect that our results will significantly inform and guide the strategic selection of contrast agents, considering the specific requirements of implantable polymeric medical devices.

Regenerative and progressing lesions in lungs and lung-associated lymph nodes from fourteen 90-day inhalation studies with chemically different particulate materials

Rat lungs and lung-associated lymph nodes from 14 inhalation studies with chemically different particulate materials were histopathologically re-evaluated, and the bronchoalveolar lavage fluid (BALF) data and lung burden analyses were compared. All investigated substances caused similar lesions. For most substances, 1 mg/m3 of respirable particulate matter was established as the borderline for adverse morphological changes after the 90-day exposure period, confirmed by the increase in polymorphonuclear neutrophils in BALF. Possible reversibility was demonstrated when recovery groups are included in the study especially allowing the differentiation between regeneration or progressing of inflammatory changes during the recovery period. It was concluded, that the major driver of toxicity is not an intrinsic chemical property of the particle but a particle effect. Concerning classification for specific target organ toxicant (STOT) repeated exposure (RE), this paper highlights that merely comparing the lowest concentration, at which adverse effects were observed, with the Classification Labelling and Packaging (CLP) regulation (EC) no. 1272/2008 guidance values is inappropriate and might lead to a STOT classification under CLP for a large part of the substances discussed in this paper, on the basis of typically mild to moderate findings in rat lung and lung-associated lymph nodes on day 1 after exposure. An in-depth evaluation of the pathologic findings is required and an expert judgement has to be included in the decision on classification and labeling, evaluating the type and severity of effects and comparing these with the classification criteria.

The role of protein corona on nanodrugs for organ-targeting and its prospects of application

Nowadays, nanodrugs become a hotspot in the high-end medical field. They have the ability to deliver drugs to reach their destination more effectively due to their unique properties and flexible functionalization. However, the fate of nanodrugs in vivo is not the same as those presented in vitro, which indeed influenced their therapeutic efficacy in vivo. When entering the biological organism, nanodrugs will first come into contact with biological fluids and then be covered by some biomacromolecules, especially proteins. The proteins adsorbed on the surface of nanodrugs are known as protein corona (PC), which causes the loss of prospective organ-targeting abilities. Fortunately, the reasonable utilization of PC may determine the organ-targeting efficiency of systemically administered nanodrugs based on the diverse expression of receptors on cells in different organs. In addition, the nanodrugs for local administration targeting diverse lesion sites will also form unique PC, which plays an important role in the therapeutic effect of nanodrugs. This article introduced the formation of PC on the surface of nanodrugs and summarized the recent studies about the roles of diversified proteins adsorbed on nanodrugs and relevant protein for organ-targeting receptor through different administration pathways, which may deepen our understanding of the role that PC played on organ-targeting and improve the therapeutic efficacy of nanodrugs to promote their clinical translation.

Association between barium exposed, CYP19A1 and central obesity: A cross-sectional study in rural China

BACKGROUND

obesity is a major risk factor for many metabolic diseases such as diabetes and cardiometabolic diseases. This study aimed to evaluate the association of plasma and urinary barium concentrations, CYP19A1 gene polymorphisms, and their interaction with central obesity in a rural Chinese population.

METHODS

restricted cubic spline model was used to explore the dose-response relationship between barium and the risk of developing central obesity and waist circumference; logistic regression model was used to assess the association between barium, CYP19A1 gene polymorphisms and their interaction with central obesity.

RESULTS

the results of the restricted cubic spline model showed that plasma barium concentration was linearly associated with the risk of developing central obesity and non-linearly associated with waist circumference. Logistic regression analysis showed that participants with Q4 plasma barium concentration exhibited a higher risk of central obesity compared to participants with Q1 barium concentration; participants carrying the rs10046-AA gene exhibited a lower risk of central obesity than those carrying the rs10046-G(GG+GA) gene; participants carrying the rs10046-GA genotype showed 1.754 times higher risk of central obesity than those carrying rs10046-GG+AA genotype. There was a significant interaction between plasma barium and CYP19A1 gene polymorphism on central obesity.

CONCLUSION

the development of central obesity was associated with plasma barium and CYP19A1.

Barium sulphate microparticles are taken up by three different cell types: HeLa, THP-1, and hMSC

Cytotoxicity and cellular uptake of spherical barium sulphate microparticles (diameter 1 µm) were studied with three different cell lines, i.e. THP-1 cells (monocytes; model for a phagocytosing cell line), HeLa cells (epithelial cells; model for a non-phagocytosing cell line), and human mesenchymal stem cells (hMSCs; model for non-phagocytosing primary cells). Barium sulphate is a chemically and biologically inert solid which allows to distinguish two different processes, e.g. the particle uptake and potential adverse biological reactions. Barium sulphate microparticles were surface-coated by carboxymethylcellulose (CMC) which gave the particles a negative charge. Fluorescence was added by conjugating 6-aminofluorescein to CMC. The cytotoxicity of these microparticles was studied by the MTT test and a live/dead assay. The uptake was visualized by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The particle uptake mechanism was quantified by flow cytometry with different endocytosis inhibitors in THP-1 and HeLa cells. The microparticles were easily taken up by all cell types, mostly by phagocytosis and micropinocytosis, within a few hours. STATEMENT OF SIGNIFICANCE: The interaction of particles and cells is of primary importance in nanomedicine, drug delivery, and nanotoxicology. It is commonly assumed that cells take up only nanoparticles unless they are able to phagocytosis. Here, we demonstrate with chemically and biologically inert microparticles of barium sulphate that even non-phagocytosing cells like HeLa and hMSCs take up microparticles to a considerable degree. This has considerable implication in biomaterials science, e.g. in case of abrasive debris and particulate degradation products from implants like endoprostheses.

Long-Term In Vitro Assessment of Biodegradable Radiopaque Composites for Fiducial Marker Fabrication

Biodegradable polymer-based composite materials may be successfully utilised to fabricate fiducial markers (FMs), which are intended to precisely label tumour margins during image-guided surgery or radiotherapy. However, due to matrix degradability, the stability of the functional properties of FMs depends on the chosen polymer. Thus, this study aimed to investigate novel radiopaque composites which varied in the polymeric matrix-polycaprolactone (PCL), poly(L-lactide-co-caprolactone) (P[LAcoCL]) with two molar ratios (70:30 and 85:15), and poly(L-lactide-co-glycolide) (with molar ratio 82:18). The radiopaque component of the materials was a mixture of barium sulphate and hydroxyapatite. The changes in water contact angle, stiffness, and radiopacity occurring during the 24-week-long degradation experiment were examined for the first time. This study comprehensively analyses the microstructural causes of composites behaviour within degradation experiments using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), gel permitted chromatography (GPC), and scanning electron microscopy (SEM). The obtained results suggest that the utilized biodegradable matrix plays an essential role in radiopaque composite properties and stability thereof. This long-term in vitro assessment enabled a comparison of the materials and aided in choosing the most favourable composite for FMs' fabrication.

Implementation of an In Vitro Experimental Setup Simulating Pulmonary Dissolution Following the Inhalation of Radioactive Particulate Material

ABSTRACT

Given the need for criteria to control the radiation doses due to radionuclide inhalation, in 1994 the International Commission on Radiological Protection presented a classification for radioactive compounds based on their pulmonary absorption rates. The Commission classified the compounds into fast, moderate, and slow categories and assigned to each material a default absorption class. Nevertheless, the proposed categories do not always resemble the actual behavior of the classified materials in the pulmonary environment. Therefore, the Commission itself suggested the assessment of the inhalation risk of a particulate substance referring to an in vivo study using the same material. Since it is not possible to trace in literature in vivo studies analyzing the physiological behavior of the totality of inhalable radioactive materials, the Commission suggested adopting in vitro systems simulating the pulmonary mechanism. For this reason, in the last 50 y, many simulating setups have been implemented, but none of these seemed to reproduce the lung dissolution dynamics effectively as the results were not comparable with the ones obtained using in vivo techniques. This paper aims to describe an innovative experimental apparatus implemented as an attempt to add another step toward the realization of a gold standard. In particular, the system was validated with BaSO 4 particulate, and the resulting error with respect to the physiological expected value figured as less than 4%. The system was then employed for the lung dissolution tests of radioactive graphite extracted from Politecnico di Milano's nuclear reactor to assess the radiobiological risk due to a slow lung absorption process that workers might run into during the reactor decommissioning.

Dissolution Rate of Nanomaterials Determined by Ions and Particle Size under Lysosomal Conditions: Contributions to Standardization of Simulant Fluids and Analytical Methods

Dissolution of inhaled engineered nanomaterials (ENM) under physiological conditions is essential to predict the clearance of the ENM from the lungs and to assess their biodurability and the potential effects of released ions. Alveolar macrophage (AM) lysosomes contain a pH 4.5 saline brine with enzymes and other components. Different types of artificial phagolysosomal simulant fluids (PSFs) have been developed for dissolution testing, but the consequence of using different media is not known. In this study, we tested to which extent six fundamentally different PSFs affected the ENM dissolution kinetics and particle size as determined by a validated transmission electron microscopy (TEM) image analysis. Three lysosomal simulant media were consistent with each other and with in vivo clearance. These media predict the quick dissolution of ZnO, the partial dissolution of SiO2, and the very slow dissolution of TiO2. The valid media use either a mix of organic acids (with the total concentration below 0.5 g/L, thereof citric acid below 0.15 g/L) or another organic acid (KH phthalate). For several ENM, including ZnO, BaSO4, and CeO2, all these differences induce only minor modulation of the dissolution rates. Only for TiO2 and SiO2, the interaction with specific organic acids is highly sensitive, probably due to sequestration of the ions, and can lead to wrong predictions when compared to the in vivo behavior. The media that fail on TiO2 and SiO2 dissolution use citric acid at concentrations above 5 g/L (up to 28 g/L). In the present selection of ENM, fluids, and methods, the different lysosomal simulant fluids did not induce changes of particle morphology, except for small changes in SiO2 and BaSO4 particles most likely due to ion dissolution, reprecipitation, and coalescence between neighboring particles. Based on the current evidence, the particle size by TEM analysis is not a sufficiently sensitive analytical method to deduce the rate of ENM dissolution in physiological media. In summary, we recommend the standardization of ENM dissolution testing by one of the three valid lysosomal simulant fluids with determination of the dissolution rate and halftime by the quantification of ions. This recommendation was established for a continuous flow system but may be relevant as well for static (batch) solubility testing.

No inflammatory effects after acute inhalation of barium sulfate particles in human volunteers

Background

Most threshold limit values are based on animal experiments. Often, the question remains whether these data reflect the situation in humans. As part of a series of investigations in our exposure lab, this study investigates whether the results on the inflammatory effects of particles that have been demonstrated in animal models can be confirmed in acute inhalation studies in humans. Such studies have not been conducted so far for barium sulfate particles (BaSO₄), a substance with very low solubility and without known substance-specific toxicity. Previous inhalation studies with zinc oxide (ZnO), which has a substance-specific toxicity, have shown local and systemic inflammatory respones. The design of these human ZnO inhalation studies was adopted for BaSO₄ to compare the effects of particles with known inflammatory activity and supposedly inert particles. For further comparison, in vitro investigations on inflammatory processes were carried out.

Methods

Sixteen healthy volunteers were exposed to filtered air and BaSO₄ particles (4.0 mg/m³) for two hours including one hour of ergometric cycling at moderate workload. Effect parameters were clinical signs, body temperature, and inflammatory markers in blood and induced sputum. In addition, particle-induced in vitro-chemotaxis of BaSO₄ was investigated with regard to mode of action and differences between in vivo and in vitro effects.

Results

No local or systemic clinical signs were observed after acute BaSO₄ inhalation and, in contrast to our previous human exposure studies with ZnO, no elevated values of biomarkers of inflammation were measured after the challenge. The in vitro chemotaxis induced by BaSO₄ particles was minimal and 15-fold lower compared to ZnO.

Conclusion

The results of this study indicate that BaSO₄ as a representative of granular biopersistent particles without specific toxicity does not induce inflammatory effects in humans after acute inhalation. Moreover, the in vitro data fit in with these in vivo results. Despite the careful and complex investigations, limitations must be admitted because the number of local effect parameters were limited and chronic toxicity could not be studied.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-02021-y.

Recent Advances in the Preparation of Barium Sulfate Nanoparticles: A Mini-Review

The potential for barium sulphate nanoparticles to be used in a variety of important fields has sparked a lot of attention. Methods for obtaining this material by milling (top-down approach) are not very popular due to the difficulty of controlling the size and shape of particles, as well as changes in their physicochemical properties during milling. More promising is the bottom-up approach, which is the interaction of Ba2+ and SO42− ions in a liquid environment. Direct precipitation is the simplest method; however, it does not allow control of the particle size. Microemulsions, microreactors membrane dispersion, as well as spinning disc reactors are used to overcome drawbacks of direct precipitation and allow control of particle size and shape. This is ensured mainly by intensive controlled micromixing of the precursors with concentrations close to saturated ones. The present review focuses on recent advances in the production of barium sulfate nanoparticles using various approaches, as well as their advantages and limitations. The issues of scaling up the techniques are also considered, and promising methods for obtaining BaSO4 nanoparticles are also discussed.

Toxicity, uptake, and nuclear translocation of ingested micro-nanoplastics in an in vitro model of the small intestinal epithelium

Despite mounting evidence of increasing micro- and nanoplastics (MNPs) in natural environments, food, and drinking water, little is known of the potential health hazards of MNPs ingestion. We assessed toxicity and uptake of environmentally relevant MNPs in an in vitro small intestinal epithelium (SIE). Test MNPs included 25 and 1000 nm polystyrene (PS) microspheres (PS25 and PS1K); 25, 100, and 1000 nm carboxyl modified PS spheres (PS25C, PS100C, and PS1KC), and secondary MNPs from incinerated polyethylene (PEI). MNPs were subjected to 3-phase digestion to mimic transformations in the gastrointestinal tract (GIT) and digestas applied to the SIE. Carboxylated MNPs significantly reduced viability and increased permeability to 3 kD dextran. Uptake of carboxyl PS materials was size dependent, with significantly greater uptake of PS25C. Fluorescence confocal imaging showed some PS25C agglomerates entering cells independent of endosomes (suggesting diffusion), others within actin shells (suggesting phagocytosis), and many free within the epithelial cells, including agglomerates within nuclei. Pre-treatment with the dynamin inhibitor Dyngo partially reduced PS25 translocation, suggesting a potential role for endocytosis. These findings suggest that ingestion exposures to MNPs could have serious health consequences and underscore the urgent need for additional detailed studies of the potential hazards of ingested MNPs.

Creating sets of similar nanoforms with the ECETOC NanoApp: real-life case studies

The ECETOC NanoApp was developed to support industry in the registration of sets of nanoforms, as well as regulators in the evaluation of these registration dossiers. The ECETOC NanoApp uses a systematic approach to create and justify sets of similar nanoforms, following the ECHA guidance in a transparent and evidence-based manner. The rational and decision rules behind the ECETOC NanoApp are described in detail in "Janer, G., R. Landsiedel, and W. Wohlleben. 2021. [Rationale and Decision Rules Behind the ECETOC NanoApp to Support Registration of Sets of Similar Nanoforms within REACH. Nanotoxicology 15 (2): 145-122. https://doi.org/10.1080/17435390.2020.1842933]". The decision criteria apply to human health and environmental hazards and risks. Here, we focus mostly on human health hazards; the decision rules are applied to a series of case studies, each consisting of real nanoforms: two barium sulfate nanoforms, four colloidal silica nanoforms, eight ceria nanoforms, and four copper phthalocyanine nanoforms. For each of them, we show step by step how the ECETOC NanoApp rules are applied. The cases include nanoforms that are justified as members of the same set of similar nanoforms based on sufficient similarity of their intrinsic properties (Tier 1). They also include other nanoforms with a relatively high (but insufficient) similarity of intrinsic properties; their similarity could be justified by functional properties (Tier 2). The case studies also include nanoforms that are concluded not to belong to the same set of similar nanoforms. These outcomes of the NanoApp were overall consistent (sometimes conservative) with available in vivo data. We also noted that datasets for various nanoforms were limited and use of the NanoApp may require the generation of data relevant to the decision criteria.

Environmental barium: potential exposure and health-hazards

The relatively widespread presence of environmental barium is raising a growing public awareness as it can lead to different health conditions. Its presence in humans may produce several effects, especially among those chronically exposed from low to moderate doses. Barium accumulation can mainly occur by exposure in the workplace or from drinking contaminated water. However, this element is also assumed with the diet, mainly from plant foods. The average amount of barium intake worldwide and its geographical variation is little known due to the lack of research attention. Barium was never considered as an essential nutrient for humans, although it is undoubtedly naturally abundant enough and distinctive in its chemical properties that it might well have some biochemical function, e.g., for regulatory purposes, both in animals and plants. The information on the potential health effects of barium exposure is primarily based on animal studies and reported as comprising kidney diseases, neurological, cardiovascular, mental, and metabolic disorders. The present paper considers exposure and potential health concerns on environmental barium, giving evidence to information that can be used in future epidemiological and experimental studies.

The Use of Nanomaterial In Vivo Organ Burden Data for In Vitro Dose Setting

Effects of nanomaterials are usually observed at higher concentrations in vitro compared to animal studies. This is pointing to differences between in vivo situations and generally less complex in vitro models. These differences concern toxicodynamics and the internal exposure (at the target cells of the in vitro and in vivo test system). The latter can be minimized by appropriate in vivo to in vitro dose extrapolations (IVIVE). An IVIVE six-step procedure is proposed here: 1) determine in vivo exposure; 2) identify in vivo organ burden at lowest observed adverse effect concentration; 3) extrapolate in vivo organ burden to in vitro effective dose; 4) extrapolate in vitro effective dose to nominal concentration; 5) set dose ranges to establish dose-response relationships; and 6) consider uncertainties and specificities of in vitro test system. Assessing the results of in vitro studies needs careful consideration of discrepancies between in vitro and in vivo models: apart from different endpoints (usually cellular responses in vitro and adverse effects on organs or organisms in vivo), nanomaterials can also have a different potency in relatively simple in vitro models and the more complex corresponding organ in vivo. IVIVE can, nonetheless, reduce the differences in exposures.

Prenatal metal mixtures and sex-specific infant negative affectivity

Prenatal exposure to metals has been associated with a range of adverse neurocognitive outcomes; however, associations with early behavioral development are less well understood. We examined joint exposure to multiple co-occurring metals in relation to infant negative affect, a stable temperamental trait linked to psychopathology among children and adults.

METHODS

Analyses included 308 mother-infant pairs enrolled in the PRISM pregnancy cohort. We measured As, Ba, Cd, Cs, Cr, Pb, and Sb in urine, collected on average during late pregnancy, by ICP-MS. At age 6 months, we assessed negative affect using the Infant Behavior Questionnaire-Revised. We used Weighted Quantile Sum (WQS) regression with repeated holdout validation to estimate the joint association between the metals and global negative affectivity, as well as four subdomains (Fear, Sadness, Distress to Limitations, and Falling Reactivity). We also tested for a sex interaction with estimated stratified weights.

RESULTS

In adjusted models, urinary metals were associated with higher scores on the Fear scale (βWQS = 0.20, 95% confidence interval [CI]: 0.09, 0.30), which captures behavioral inhibition, characterized by startle or distress to sudden changes in the environment and inhibited approach to novelty. We observed a significant sex interaction (95% CI for the cross-product term: -0.19, -0.01), and stratified weights showed girls (61.6%) contributed substantially more to the mixture effect compared with boys (38.4%). Overall, Ba contributed the greatest mixture weight (22.5%), followed by Cs (14.9%) and As (14.6%).

CONCLUSIONS

Prenatal exposure to metals was associated with increased infant scores on the temperamental domain of fear, with girls showing particular sensitivity.Key words: Prenatal; Metals; Mixtures; Temperament; Infancy; Negative affect.

A review of hepatic nanotoxicology - summation of recent findings and considerations for the next generation of study designs

The liver is one of the most important multi-functional organs in the human body. Amongst various crucial functions, it is the main detoxification center and predominantly implicated in the clearance of xenobiotics potentially including particulates that reach this organ. It is now well established that a significant quantity of injected, ingested or inhaled nanomaterials (NMs) translocate from primary exposure sites and accumulate in liver. This review aimed to summarize and discuss the progress made in the field of hepatic nanotoxicology, and crucially highlight knowledge gaps that still exist.Key considerations include In vivo studies clearly demonstrate that low-solubility NMs predominantly accumulate in the liver macrophages the Kupffer cells (KC), rather than hepatocytes.KCs lining the liver sinusoids are the first cell type that comes in contact with NMs in vivo. Further, these macrophages govern overall inflammatory responses in a healthy liver. Therefore, interaction with of NM with KCs in vitro appears to be very important.Many acute in vivo studies demonstrated signs of toxicity induced by a variety of NMs. However, acute studies may not be that meaningful due to liver's unique and unparalleled ability to regenerate. In almost all investigations where a recovery period was included, the healthy liver was able to recover from NM challenge. This organ's ability to regenerate cannot be reproduced in vitro. However, recommendations and evidence is offered for the design of more physiologically relevant in vitro models.Models of hepatic disease enhance the NM-induced hepatotoxicity.The review offers a number of important suggestions for the future of hepatic nanotoxicology study design. This is of great significance as its findings are highly relevant due to the development of more advanced in vitro, and in silico models aiming to improve physiologically relevant toxicological testing strategies and bridging the gap between in vitro and in vivo experimentation.

Organ burden of inhaled nanoceria in a 2-year low-dose exposure study: dump or depot?

No detailed information on in vivo biokinetics of CeO₂ nanoparticles (NPs) following chronic low-dose inhalation is available. The CeO₂ burden for lung, lung-associated lymph nodes, and major non-pulmonary organs, blood, and feces, was determined in a chronic whole-body inhalation study in female Wistar rats undertaken according to OECD TG453 (6 h per day for 5 days per week for a 104 weeks with the following concentrations: 0, 0.1, 0.3, 1.0, and 3.0 mg/m³, animals were sacrificed after 3, 12, 24 months). Different spectroscopy methods (ICP-MS, ion-beam-microscopy) were used for the quantification of organ burden and for visualization of NP distribution patterns in tissues. After 24 months of exposure, the highest CeO₂ lung burden (4.41 mg per lung) was associated with the highest aerosol concentration and was proportionally lower for the other groups in a dose-dependent manner. Imaging techniques confirmed the presence of CeO₂ agglomerates of different size categories within lung tissue with a non-homogenous distribution. For the highest exposure group, after 24 months in total 1.2% of the dose retained in the lung was found in the organs and tissues analyzed in this study, excluding lymph nodes and skeleton. The CeO₂ burden per tissue decreased from lungs > lymph nodes > hard bone > liver > bone marrow. For two dosage groups, the liver organ burden showed a low accumulation rate. Here, the liver can be regarded as depot, whereas kidneys, the skeleton, and bone marrow seem to be dumps due to steadily increasing NP burden over time.

Appearance of Alveolar Macrophage Subpopulations in Correlation With Histopathological Effects in Short-Term Inhalation Studies With Biopersistent (Nano)Materials

Following inhalation and deposition in the alveolar region at sufficient dose, biopersistent (nano)materials generally provoke pulmonary inflammation. Alveolar macrophages (AMs) are mediators of pulmonary immune responses and were broadly categorized in pro-inflammatory M1 and anti-inflammatory M2 macrophages. This study aimed at identifying AM phenotype as M1 or M2 upon short-term inhalation exposure to different (nano)materials followed by a postexposure period. Phenotyping of AM was retrospectively performed using immunohistochemistry. M1 (CD68⁺iNOS⁺) and M2 (CD68⁺CD206⁺ and CD68⁺ArgI⁺) AMs were characterized in formalin-fixed, paraffin-embedded lung tissue of rats exposed for 6 hours/day for 5 days to air, 100 mg/m³ nano-TiO₂, 25 mg/m³ nano-CeO₂, 32 mg/m³ multiwalled carbon nanotubes, or 100 mg/m³ micron-sized quartz. During acute inflammation, relative numbers of M1 AMs were markedly increased, whereas relative numbers of M2 were generally decreased compared to control. Following an exposure-free period, changes in iNOS or CD206 expression correlated with persistence, regression, or progression of inflammation, suggesting a role of M1/M2 AMs in the pathogenesis of pulmonary inflammation. However, no clear correlation of AM subpopulations with qualitatively distinct histopathological findings caused by different (nano)materials was found. A more detailed understanding of the processes underlaying these morphological changes is needed to identify biomarkers for different histopathological outcomes.

Understanding Dissolution Rates via Continuous Flow Systems with Physiologically Relevant Metal Ion Saturation in Lysosome

Dissolution rates of nanomaterials can be decisive for acute in vivo toxicity (via the released ions) and for biopersistence (of the remaining particles). Continuous flow systems (CFSs) can screen for both aspects, but operational parameters need to be adjusted to the specific physiological compartment, including local metal ion saturation. CFSs have two adjustable parameters: the volume flow-rate and the initial particle loading. Here we explore the pulmonary lysosomal dissolution of nanomaterials containing the metals Al, Ba, Zn, Cu over a wide range of volume flow-rates in a single experiment. We identify the ratio of particle surface area (SA) per volume flow-rate (SA/V) as critical parameter that superimposes all dissolution rates of the same material. Three complementary benchmark materials—ZnO (quick dissolution), TiO₂ (very slow dissolution), and BaSO₄ (partial dissolution)—consistently identify the SA/V range of 0.01 to 0.03 h/cm as predictive for lysosomal pulmonary biodissolution. We then apply the identified method to compare against non-nanoforms of the same substances and test aluminosilicates. For BaSO₄ and TiO₂, we find high similarity of the dissolution rates of their respective nanoform and non-nanoform, governed by the local ion solubility limit at relevant SA/V ranges. For aluminosilicates, we find high similarity of the dissolution rates of two Kaolin nanoforms but significant dissimilarity against Bentonite despite the similar composition.

Predicting dissolution and transformation of inhaled nanoparticles in the lung using abiotic flow cells: The case of barium sulfate

Barium sulfate (BaSO₄) was considered to be poorly-soluble and of low toxicity, but BaSO₄ NM-220 showed a surprisingly short retention after intratracheal instillation in rat lungs, and incorporation of Ba within the bones. Here we show that static abiotic dissolution cannot rationalize this result, whereas two dynamic abiotic dissolution systems (one flow-through and one flow-by) indicated 50% dissolution after 5 to 6 days at non-saturating conditions regardless of flow orientation, which is close to the in vivo half-time of 9.6 days. Non-equilibrium conditions were thus essential to simulate in vivo biodissolution. Instead of shrinking from 32 nm to 23 nm (to match the mass loss to ions), TEM scans of particles retrieved from flow-cells showed an increase to 40 nm. Such transformation suggested either material transport through interfacial contact or Ostwald ripening at super-saturating conditions and was also observed in vivo inside macrophages by high-resolution TEM following 12 months inhalation exposure. The abiotic flow cells thus adequately predicted the overall pulmonary biopersistence of the particles that was mediated by non-equilibrium dissolution and recrystallization. The present methodology for dissolution and transformation fills a high priority gap in nanomaterial hazard assessment and is proposed for the implementation of grouping and read-across by dissolution rates.

Barium chloride dose-dependently induced heart and lung injury in Wistar rats

Barium (Ba) is one of the environmental pollutant metals that incite deleterious effects on human health. The present study investigated the effects of exposure to different doses of barium chloride (BaCl₂ ) on heart and lung of Wistar rats. Rats were exposed to BaCl₂ at 150, 300, and 600 mg/L for seven consecutive days. Results indicated that exposure to Ba caused heart and lung damage evidenced by significant increase in plasma lactate dehydrogenase and creatine kinase activities, total cholesterol, triglyceride, and low-density lipoprotein-cholesterol levels, while high-density lipoprotein-cholesterol level decreased when compared with control. Moreover, BaCl₂ significantly decreased superoxide dismutase, catalase, and acetylcholinesterase activities as well as glutathione level in heart and lung of the treated rats. Furthermore, the dose-dependent increase in cardiac and lung lipid peroxidation, advanced oxidative protein product and nitric oxide levels were accompanied by marked increase in metallothionein in the BaCl₂ -treated rats. Administration of BaCl₂ altered hematological parameters and significantly increased concentrations of interleukin-6 in the treated rats. Histology analysis showed significant alteration in the heart and lung tissues of Ba-treated rats. In conclusion, BaCl₂ -induced heart and lung damages via disruption of antioxidant defense systems, and activation of inflammatory mediators and alteration in hematological parameters in rats.

X-ray shielding structural and properties design for the porous transparent BaSO4/cellulose nanocomposite membranes

Since effective shielding of X-rays was required in medical, aviation and nuclear fields, a novel X-ray shielding BaSO₄/cellulose nanocomposite membrane (BSCM) material with porous transparent structure has been designed. The effects of carboxylated nano-BaSO₄ (BS) addition on the physical and morphological properties of the cellulose membrane (CM) were investigated. Meanwhile, the influence of X-ray shielding capacity was studied by different layers of composite membranes and the shielding mechanism of the X-ray was also discussed. Scanning electron microscopy (SEM) images displayed the aggregations of BS in the cellulose surface. Fourier transform infrared spectroscopy (FTIR) showed that the incorporation of BS into CM caused molecular interactions between CM and BS. Brunauer-Emmett-Teller (BET) indicated that the load of BS contributed little to the specific surface area and pore size. Meanwhile, the water vapor transmission rates (WVTR) also stayed at the same level before and after the binding of BS. The swelling ratios, weight loss ratios and mechanical property were decreased along with the addition of BS. The radiation shielding ability was enhanced. Therefore, this work was regarded as a possible example that the BSCM was designed as X-ray radiation shielding material or sandwich filler material in the implication of radiation shielding glass.

Airborne Particulate Matter: Human Exposure and Health Effects

OBJECTIVE

Exposure to airborne particulate matter (PM) is estimated to cause millions of premature deaths annually. This work conveys known routes of exposure to PM and resultant health effects.

METHODS

A review of available literature.

RESULTS

Estimates for daily PM exposure are provided. Known mechanisms by which insoluble particles are transported and removed from the body are discussed. Biological effects of PM, including immune response, cytotoxicity, and mutagenicity, are reported. Epidemiological studies that outline the systemic health effects of PM are presented.

CONCLUSION

While the integrated, per capita, exposure of PM for a large fraction of the first-world may be less than 1 mg per day, links between several syndromes, including attention deficit hyperactivity disorder (ADHD), autism, loss of cognitive function, anxiety, asthma, chronic obstructive pulmonary disease (COPD), hypertension, stroke, and PM exposure have been suggested. This article reviews and summarizes such links reported in the literature.

Fate of Barium Sulfate Nanoparticles Deposited in the Lungs of Rats

We have shown that barium [from BaSO4 nanoparticles (NPs)] was cleared from the lungs faster than other poorly soluble NPs and translocated mostly to bone. We now studied barium biokinetics in rats during Study 1: two-year inhalation exposure to 50 mg/m3 BaSO4 NP aerosols, and Study 2: single intratracheal (IT) instillation of increasing doses of BaSO4 NPs or BaCl2. Study 1 showed that lung barium content measured by inductively coupled plasma mass spectrometry increased during 360 days of BaSO4 NP aerosol exposures. An equilibrium was established from that time until 2 years. Barium concentrations in BaSO4-exposed animals were in the order (lungs > lymph nodes > hard bone > bone marrow > liver). In Study 2, there was an increase in lung barium post-IT instillation of BaSO4 NPs while barium from BaCl2 was mostly cleared by day 28. Transmission electron microscopy showed intact BaSO4 NPs in alveolar macrophages and type II epithelial cells, and in tracheobronchial lymph nodes. Using stimulated Raman scattering microscopy, specific BaSO4 Raman spectra were detected in BaSO4 NP-instilled lungs and not in other organs. Thus, we posit that barium from BaSO4 NPs translocates from the lungs mainly after dissolution. Barium ions are then incorporated mostly into the bone and other organs.

Water-Dispersible Bismuth-Organic Materials with Computed Tomography Contrast Properties

Two bismuth-organic network polymers were synthesized by means of a one-step polycondensation reaction between an aromatic dithiol/trithiol and triphenylbismuth. The materials were characterized by solid-state UV-vis spectroscopy, Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction, elemental microanalysis, and thermogravimetric analysis. Uniform dispersion of the hydrophobic and water-insoluble bismuth-containing polymers in aqueous media was achieved by the addition of 2 kDa poly(ethylene glycol) methyl ether thiol. This enabled quantitative phantom imaging experiments on a clinical computed tomography (CT) scanner, which showed that the coordination polymers possessed strong CT contrast properties. The observed X-ray attenuation properties of each coordination polymer were correlated with its bismuth payload. The X-ray opacity, thermal and chemical stabilities, and aqueous dispersibility of this novel class of bismuth-organic materials make them potentially useful as biomedical CT contrast agents and radiopaque materials.

Radiopaque Fully Degradable Nanocomposites for Coronary Stents

Bioresorbable scaffolds (BRS) were introduced to overcome limitations of current metallic drug-eluting stents and poly-L-lactide (PLLA) has been used in the fabrication of BRS due to its biodegradability and biocompatibility. However, such polymers have weaker mechanical properties as compared to metals, limiting their use in BRS. We hypothesized that nanofillers can be used to enhance the mechanical properties considerably in PLLA. To this end, polymer-matrix composites consisting of PLLA reinforced with 5-20 wt% barium sulfate (BaSO4) nanofillers as a potential BRS material was evaluated. Stearic-acid (SA) modified BaSO4 nanofillers were used to examine the effect of functionalization. Rigid nanofillers improved the tensile modulus and strength of PLLA (60% and 110% respectively), while the use of SA-BaSO4 caused a significant increase (~110%) in the elongation at break. Enhancement in mechanical properties is attributed to functionalization which decreased the agglomeration of the nanofillers and improved dispersion. The nanocomposites were also radiopaque. Finite element analysis (FEA) showed that scaffold fabricated from the novel nanocomposite material has improved scaffolding ability, specifically that the strut thickness could be decreased compared to the conventional PLLA scaffold. In conclusion, BaSO4/PLLA-based nanocomposites could potentially be used as materials for BRS with improved mechanical and radiopaque properties.

Contrast-enhanced computed tomography combined with Chitosan-Fe3O4 nanoparticles targeting fibroblast growth factor receptor and vascular endothelial growth factor receptor in the screening of early esophageal cancer

Esophageal cancer is a malignant tumor with a relatively high invasiveness, metastatic potential and worldwide incidence among human cancers. The majority of patients with esophageal cancer are diagnosed in a late tumor stage due to a lack of advanced and sensitive protocols for the diagnosis of patients with early-stage esophageal cancer. In the current study, contrast-enhanced computerized tomography (CECT) combined with Chitosan-Fe₃O₄ nanoparticles targeting fibroblast growth factor receptor (FGFR) and vascular endothelial growth factor receptor (VEGFR; CECT-CNFV) were used to diagnose patients with suspected esophageal cancer. A Chitosan-Fe₃O₄-parceled bispecific antibody targeting FGFR and VEGFR was produced and its affinity to esophageal cancer cells was determined both in vitro and in vivo. A total of 320 patients with suspected esophageal cancer were voluntarily recruited to evaluate the efficacy of CECT-CNFV in the diagnosis of early-stage esophageal cancer. All participants were subjected to CT and CECT-CNFV to detect whether tumors were present in the esophageal area. A Chitosan-Fe₃O₄ nanoparticles contrast agent was orally administered at 20 min prior to CT and CECT-CNFV. The results demonstrated that CECT-CNFV improved diagnostic sensitivity and provided a novel protocol for the diagnosis of tumors in patients with suspected gastric cancer at an early-stage. Furthermore, the resolution ratio of images was enhanced by CECT-CNFV, which enabled the visualization of tiny tumor nodules in esophageal tissue. Clinical data demonstrated that CECT-CNFV diagnosed 200 patients with suspected early-stage esophageal cancer and 120 patients as tumor free. In addition, CECT-CNFV exhibited higher signal enhancement of tumor nodules than CT, suggesting a higher accuracy and accumulation of nanoparticle contrast agent within the tumor nodules of esophageal tissue. Notably, the survival rate of patients with esophageal cancer diagnosed at an early-stage by CECT-CNFV was higher than the mean five-year survival rate (P<0.01). In conclusion, CECT-CNFV enhanced the sensitivity and accuracy of CT in the diagnosis of early-stage esophageal cancer. Thus, CECT-CNFV may improve the accuracy of CT in the diagnosis of mural enhancement in patients with esophageal cancer.

The impact of nanomaterial characteristics on inhalation toxicity

During the last few decades, nanotechnology has evolved into a success story, apparent from a steadily increasing number of scientific publications as well as a large number of applications based on engineered nanomaterials (ENMs). Its widespread uses suggest a high relevance for consumers, workers and the environment, hence justifying intensive investigations into ENM-related adverse effects as a prerequisite for nano-specific regulations. In particular, the inhalation of airborne ENMs, being assumed to represent the most hazardous type of human exposure to these kinds of particles, needs to be scrutinized. Due to an increased awareness of possible health effects, which have already been seen in the case of ultrafine particles (UFPs), research and regulatory measures have set in to identify and address toxic implications following their almost ubiquitous occurrence. Although ENM properties differ from those of the respective bulk materials, the available assessment protocols are often designed for the latter. Despite the large benefit ensuing from the application of nanotechnology, many issues related to ENM behavior and adverse effects are not fully understood or should be examined anew. The traditional hypothesis that ENMs exhibit different or additional hazards due to their "nano" size has been challenged in recent years and ENM categorization according to their properties and toxicity mechanisms has been proposed instead. This review summarizes the toxicological effects of inhaled ENMs identified to date, elucidating the modes of action which provoke different mechanisms in the respiratory tract and their resulting effects. By linking particular mechanisms and adverse effects to ENM properties, grouping of ENMs based on toxicity-related properties is supposed to facilitate toxicological risk assessment. As intensive studies are still required to identify these "ENM classes", the need for alternatives to animal studies is evident and advances in cell-based test systems for pulmonary research are presented here. We hope to encourage the ongoing discussion about ENM risks and to advocate the further development and practice of suitable testing and grouping methods.

Cerium oxide and barium sulfate nanoparticle inhalation affects gene expression in alveolar epithelial cells type II

BACKGROUND

Understanding the molecular mechanisms of nanomaterial interacting with cellular systems is important for appropriate risk assessment. The identification of early biomarkers for potential (sub-)chronic effects of nanoparticles provides a promising approach towards cost-intensive and animal consuming long-term studies. As part of a 90-day inhalation toxicity study with CeO₂ NM-212 and BaSO₄ NM-220 the present investigations on gene expression and immunohistochemistry should reveal details on underlying mechanisms of pulmonary effects. The role of alveolar epithelial cells type II (AEII cells) is focused since its contribution to defense against inhaled particles and potentially resulting adverse effects is assumed. Low dose levels should help to specify particle-related events, including inflammation and oxidative stress.

RESULTS

Rats were exposed to clean air, 0.1, 0.3, 1.0, and 3.0 mg/m³ CeO₂ NM-212 or 50.0 mg/m³ BaSO₄ NM-220 and the expression of 391 genes was analyzed in AEII cells after one, 28 and 90 days exposure. A total number of 34 genes was regulated, most of them related to inflammatory mediators. Marked changes in gene expression were measured for Ccl2, Ccl7, Ccl17, Ccl22, Ccl3, Ccl4, Il-1α, Il-1ß, and Il-1rn (inflammation), Lpo and Noxo1 (oxidative stress), and Mmp12 (inflammation/lung cancer). Genes related to genotoxicity and apoptosis did not display marked regulation. Although gene expression was less affected by BaSO₄ compared to CeO₂ the gene pattern showed great overlap. Gene expression was further analyzed in liver and kidney tissue showing inflammatory responses in both organs and marked downregulation of oxidative stress related genes in the kidney. Increases in the amount of Ce were measured in liver but not in kidney tissue. Investigation of selected genes on protein level revealed increased Ccl2 in bronchoalveolar lavage of exposed animals and increased Lpo and Mmp12 in the alveolar epithelia.

CONCLUSION

AEII cells contribute to CeO₂ nanoparticle caused inflammatory and oxidative stress reactions in the respiratory tract by the release of related mediators. Effects of BaSO₄ exposure are low. However, overlap between both substances were detected and support identification of potential early biomarkers for nanoparticle effects on the respiratory system. Signs for long-term effects need to be further evaluated by comparison to a respective exposure setting.

Analytical High-resolution Electron Microscopy Reveals Organ-specific Nanoceria Bioprocessing

This is the first utilization of advanced analytical electron microscopy methods, including high-resolution transmission electron microscopy, high-angle annular dark field scanning transmission electron microscopy, electron energy loss spectroscopy, and energy-dispersive X-ray spectroscopy mapping to characterize the organ-specific bioprocessing of a relatively inert nanomaterial (nanoceria). Liver and spleen samples from rats given a single intravenous infusion of nanoceria were obtained after prolonged (90 days) in vivo exposure. These advanced analytical electron microscopy methods were applied to elucidate the organ-specific cellular and subcellular fate of nanoceria after its uptake. Nanoceria is bioprocessed differently in the spleen than in the liver.

The roles of potassium channels in contractile response to urotensin-II in mercury chloride induced endothelial dysfunction in rat aorta

Urotensin-II (U-II), the most potent vasoconstrictor that has recently been recognized as a new candidate in cardiovascular dysfunction, might exert vasoconstriction through, at least partially, potassium channels that are predominant in both endothelial and vascular smooth muscle cells (VSMCs). The present study was designed to evaluate the roles of potassium channels in vascular responses to U-II in intact and mercury induced endothelial dysfunction in rat aorta. The study involved pre-incubation of rat aortic rings with potassium channels blockers: charybdotoxin (chtx), tetraethylammonium (TEA), barium chloride (BaCl₂), glibenclamide, 4-aminopyridine (4-AP) and clotrimazole. Then vascular responses to increased concentrations of human U-II (hU-II) were applied to each group in the presence and absence of mercury chloride (HgCl₂). Urotensin-II efficacy was significantly increased in chtx, TEA and BaCl₂ treated groups, while significantly decreased in glibenclamide and clotrimazole treated groups as compared with the control group. In the presence of mercury, hU-II efficacy was significantly changed in all groups except clotrimazole treated group. The novel findings were that potassium channels modulated the vascular contractile responses to hU-II in isolated rat aorta and mercury treatment increased hU-II efficacy and deteriorated potassium signaling.

Transmucosal Nanoparticles: Toxicological Overview

Nanoparticles have specific physicochemical properties different to bulk materials of the same composition and such properties make them very attractive for commercial and medical applications. Mucoadhesive nanoparticulate dosage forms are designed to enable prolonged retention of these nanoparticles at the site of application, providing a controlled drug release for improved therapeutic outcome. Moreover, drug delivery across the mucosa bypasses the first-pass hepatic metabolism and avoids the degradation by gastrointestinal enzymes. However, like most new technologies, there is a rising debate concerning the possible transmucosal side effects resulting from the use of particles at the nano level. In fact, these nanoparticles on entering the body, deposit in several organs and may cause adverse biological reactions by modifying the physiochemical properties of living matter. Several investigators have found nanoparticles responsible for toxicity in different organs. In addition, the toxicity of nanoparticles also depends on whether they are persistent or cleared from the different organs of entry and whether the host can raise an effective response to sequester or dispose of the particles. In contrast to many efforts aimed at exploiting desirable properties of nanoparticles for medicine, there are limited attempts to evaluate potentially undesirable effects of these particles when administered intentionally for medical purposes. This chapter focuses on the overview of the mucosal systems, fate of nanoparticles, mechanism of nanoparticle's toxicity and the various toxicity issues associated with nanoparticles through mucosal routes.

Biopersistence of NiO and TiO₂ Nanoparticles Following Intratracheal Instillation and Inhalation

The hazards of various types of nanoparticles with high functionality have not been fully assessed. We investigated the usefulness of biopersistence as a hazard indicator of nanoparticles by performing inhalation and intratracheal instillation studies and comparing the biopersistence of two nanoparticles with different toxicities: NiO and TiO₂ nanoparticles with high and low toxicity among nanoparticles, respectively. In the 4-week inhalation studies, the average exposure concentrations were 0.32 and 1.65 mg/m³ for NiO, and 0.50 and 1.84 mg/m³ for TiO₂. In the instillation studies, 0.2 and 1.0 mg of NiO nanoparticles and 0.2, 0.36, and 1.0 mg of TiO₂ were dispersed in 0.4 mL water and instilled to rats. After the exposure, the lung burden in each of five rats was determined by Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES) from 3 days to 3 months for inhalation studies and to 6 months for instillation studies. In both the inhalation and instillation studies, NiO nanoparticles persisted for longer in the lung compared with TiO₂ nanoparticles, and the calculated biological half times (BHTs) of the NiO nanoparticles was longer than that of the TiO₂ nanoparticles. Biopersistence also correlated with histopathological changes, inflammatory response, and other biomarkers in bronchoalveolar lavage fluid (BALF) after the exposure to nanoparticles. These results suggested that the biopersistence is a good indicator of the hazards of nanoparticles.

Biopersistence of NiO and TiO₂ Nanoparticles Following Intratracheal Instillation and Inhalation

The hazards of various types of nanoparticles with high functionality have not been fully assessed. We investigated the usefulness of biopersistence as a hazard indicator of nanoparticles by performing inhalation and intratracheal instillation studies and comparing the biopersistence of two nanoparticles with different toxicities: NiO and TiO₂ nanoparticles with high and low toxicity among nanoparticles, respectively. In the 4-week inhalation studies, the average exposure concentrations were 0.32 and 1.65 mg/m³ for NiO, and 0.50 and 1.84 mg/m³ for TiO₂. In the instillation studies, 0.2 and 1.0 mg of NiO nanoparticles and 0.2, 0.36, and 1.0 mg of TiO₂ were dispersed in 0.4 mL water and instilled to rats. After the exposure, the lung burden in each of five rats was determined by Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES) from 3 days to 3 months for inhalation studies and to 6 months for instillation studies. In both the inhalation and instillation studies, NiO nanoparticles persisted for longer in the lung compared with TiO₂ nanoparticles, and the calculated biological half times (BHTs) of the NiO nanoparticles was longer than that of the TiO₂ nanoparticles. Biopersistence also correlated with histopathological changes, inflammatory response, and other biomarkers in bronchoalveolar lavage fluid (BALF) after the exposure to nanoparticles. These results suggested that the biopersistence is a good indicator of the hazards of nanoparticles.

Protein corona: implications for nanoparticle interactions with pulmonary cells

Background

We previously showed that cerium oxide (CeO₂), barium sulfate (BaSO₄) and zinc oxide (ZnO) nanoparticles (NPs) exhibited different lung toxicity and pulmonary clearance in rats. We hypothesize that these NPs acquire coronas with different protein compositions that may influence their clearance from the lungs.

Methods

CeO₂, silica-coated CeO₂, BaSO₄, and ZnO NPs were incubated in rat lung lining fluid in vitro. Then, gel electrophoresis followed by quantitative mass spectrometry was used to characterize the adsorbed proteins stripped from these NPs. We also measured uptake of instilled NPs by alveolar macrophages (AMs) in rat lungs using electron microscopy. Finally, we tested whether coating of gold NPs with albumin would alter their lung clearance in rats.

Results

We found that the amounts of nine proteins in the coronas formed on the four NPs varied significantly. The amounts of albumin, transferrin and α-1 antitrypsin were greater in the coronas of BaSO₄ and ZnO than that of the two CeO₂ NPs. The uptake of BaSO₄ in AMs was less than CeO₂ and silica-coated CeO₂ NPs. No identifiable ZnO NPs were observed in AMs. Gold NPs coated with albumin or citrate instilled into the lungs of rats acquired the similar protein coronas and were cleared from the lungs to the same extent.

Conclusions

We show that different NPs variably adsorb proteins from the lung lining fluid. The amount of albumin in the NP corona varies as does NP uptake by AMs. However, albumin coating does not affect the translocation of gold NPs across the air-blood barrier. A more extensive database of corona composition of a diverse NP library will develop a platform to help predict the effects and biokinetics of inhaled NPs.

Application of novel targeting nanoparticles contrast agent combined with contrast-enhanced computed tomography during screening for early-phase gastric carcinoma

Gastric cancer is one of the most common human tumors worldwide. The biggest bottleneck is a lack of advanced and sensitive protocols for the diagnosis of patients with early-stage gastric cancer. Therefore, more sensitive methods of diagnosing gastric cancer are urgently required to improve survival rates. In this clinical study, contrast-enhanced computed tomography (CECT) with targeting nanoparticles contrast agent (CECT-TNCA) was used to diagnose early-stage gastric cancer. The specific-targeted tyrosine kinase inhibitors of gastric cancer, including platelet-derived growth factor receptor-β, Ret and Kit, were used as TNCAs. A total of 484 patients with suspected gastric cancer were voluntarily recruited to investigate the efficacy of CECT-TNCA in the diagnosis of patients with early-stage gastric cancer. Patients with suspected gastric cancer were subjected CT and CECT-TNCA to detect whether gastric tumors existed. TNCA was orally administered before CT and CECT-TNCA (20 min). Our diagnostic data revealed that CECT-TNCA improved sensitivity and provided a new protocol to diagnose tumors in patients with suspected gastric cancer at the early stage. In addition, imaging using CECT-TNCA enabled the visualization of tiny nodules in the gastric area. CECT-TNCA diagnosed 182 patients with suspected gastric cancer as tumor-free. CECT-TNCA confirmed gastric cancer in 302 patients. Our novel diagnosis indicated significantly (P<0.01) differential signal enhancement in the gastric nodules via CECT-TNCA compared with CT, suggesting higher accuracy and the accumulation of TNCA in tumor nodules in the stomach. Furthermore, survival rates of patients detected by early-diagnosis of CECT-TNCA were significantly higher than the mean five-year survival (P<0.01). In conclusion, our investigations demonstrate that the sensibility and accuracy of CT is improved through combination with liposome-encapsulated nanoparticle contrast agent for the diagnosis of early stage gastric cancer when compared with single CT detection. CECT-TNCA improves the accuracy of CT and diagnostic confidence in assessing mural enhancement in patients with suspected gastric cancer.

Effects from a 90-day inhalation toxicity study with cerium oxide and barium sulfate nanoparticles in rats

Background

Nanomaterials like cerium oxide and barium sulfate are frequently processed in industrial and consumer products and exposure of humans and other organisms is likely. Generally less information is given on health effects and toxicity, especially regarding long-term exposure to low nanoparticle doses. Since inhalation is still the major route of uptake the present study focused on pulmonary effects of CeO₂NM-212 (0.1, 0.3, 1.0, 3.0 mg/m³) and BaSO₄NM-220 nanoparticles (50.0 mg/m³) in a 90-day exposure setup. To define particle-related effects and potential mechanisms of action, observations in histopathology, bronchoalveolar lavage and immunohistochemistry were linked to pulmonary deposition and clearance rates. This further allows evaluation of potential overload related effects.

Results

Lung burden values increased with increasing nanoparticle dose levels and ongoing exposure. At higher doses, cerium clearance was impaired, suggesting lung overload. Barium elimination was extremely rapid and without any signs of overload. Bronchoalveolar lavage fluid analysis and histopathology revealed lung tissue inflammation with increasing severity and post-exposure persistency for CeO₂. Also, marker levels for genotoxicity and cell proliferation were significantly increased. BaSO₄ showed less inflammation or persistency of effects and particularly affected the nasal cavity.

Conclusion

CeO₂ nanoparticles penetrate the alveolar space and affect the respiratory tract after inhalation mainly in terms of inflammation. Effects at low dose levels and post-exposure persistency suggest potential long-term effects and a notable relevance for human health. The generated data might be useful to improve nanoparticle risk assessment and threshold value generation. Mechanistic investigations at conditions of non-overload and absent inflammation should be further investigated in future studies.

In vivo degeneration and the fate of inorganic nanoparticles

What happens to inorganic nanoparticles (NPs), such as plasmonic gold or silver, superparamagnetic iron oxide, or fluorescent quantum dot NPs after they have been administrated to a living being? This review discusses the integrity, biodistribution, and fate of NPs after in vivo administration. The hybrid nature of the NPs is described, conceptually divided into the inorganic core, the engineered surface coating comprising of the ligand shell and optionally also bio-conjugates, and the corona of adsorbed biological molecules. Empirical evidence shows that all of these three compounds may degrade individually in vivo and can drastically modify the life cycle and biodistribution of the whole heterostructure. Thus, the NPs may be decomposed into different parts, whose biodistribution and fate would need to be analyzed individually. Multiple labeling and quantification strategies for such a purpose will be discussed. All reviewed data indicate that NPs in vivo should no longer be considered as homogeneous entities, but should be seen as inorganic/organic/biological nano-hybrids with complex and intricately linked distribution and degradation pathways.

Biokinetics of Nanomaterials: the Role of Biopersistence

Nanotechnology risk management strategies and environmental regulations continue to rely on hazard and exposure assessment protocols developed for bulk materials, including larger size particles, while commercial application of nanomaterials (NMs) increases. In order to support and corroborate risk assessment of NMs for workers, consumers, and the environment it is crucial to establish the impact of biopersistence of NMs at realistic doses. In the future, such data will allow a more refined future categorization of NMs. Despite many experiments on NM characterization and numerous in vitro and in vivo studies, several questions remain unanswered including the influence of biopersistence on the toxicity of NMs. It is unclear which criteria to apply to characterize a NM as biopersistent. Detection and quantification of NMs, especially determination of their state, i.e., dissolution, aggregation, and agglomeration within biological matrices and other environments are still challenging tasks; moreover mechanisms of nanoparticle (NP) translocation and persistence remain critical gaps. This review summarizes the current understanding of NM biokinetics focusing on determinants of biopersistence. Thorough particle characterization in different exposure scenarios and biological matrices requires use of suitable analytical methods and is a prerequisite to understand biopersistence and for the development of appropriate dosimetry. Analytical tools that potentially can facilitate elucidation of key NM characteristics, such as ion beam microscopy (IBM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), are discussed in relation to their potential to advance the understanding of biopersistent NM kinetics. We conclude that a major requirement for future nanosafety research is the development and application of analytical tools to characterize NPs in different exposure scenarios and biological matrices.

Isotope Tracers To Study the Environmental Fate and Bioaccumulation of Metal-Containing Engineered Nanoparticles: Techniques and Applications

The rapidly growing applicability of metal-containing engineered nanoparticles (MENPs) has made their environmental fate, biouptake, and transformation important research topics. However, considering the relatively low concentration of MENPs and the high concentration of background metals in the environment and in organisms, tracking the fate of MENPs in environment-related scenarios remains a challenge. Intrinsic labeling of MENPs with radioactive or stable isotopes is a useful tool for the highly sensitive and selective detection of MENPs in the environment and organisms, thus enabling tracing of their transformation, uptake, distribution, and clearance. In this review, we focus on radioactive/stable isotope labeling of MENPs for their environmental and biological tracing. We summarize the advantages of intrinsic radioactive/stable isotopes for MENP labeling and discuss the considerations in labeling isotope selection and preparation of labeled MENPs, as well as exposure routes and detection of labeled MENPs. In addition, current practice in the use of radioactive/stable isotope labeling of MENPs to study their environmental fate and bioaccumulation is reviewed. Future perspectives and potential applications are also discussed, including imaging techniques for radioactive- and stable-isotope-labeled MENPs, hyphenated multistable isotope tracers with speciation analysis, and isotope fractionation as a MENP tracer. It is expected that this critical review could provide the necessary background information to further advance the applications of isotope tracers to study the environmental fate and bioaccumulation of MENPs.

Safety assessment of nanomaterials using an advanced decision-making framework, the DF4nanoGrouping

As presented at the 2016 TechConnect World Innovation Conference on 22-25 May 2016 in Washington DC, USA, the European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) 'Nano Task Force' proposes a Decision-making framework for the grouping and testing of nanomaterials (DF4nanoGrouping) consisting of three tiers to assign nanomaterials to four main groups with possible further subgrouping to refine specific information needs. The DF4nanoGrouping covers all relevant aspects of a nanomaterial's life cycle and biological pathways: intrinsic material properties and system-dependent properties (that depend upon the nanomaterial's respective surroundings), biopersistence, uptake and biodistribution, and cellular and apical toxic effects. Use, release, and exposure route may be applied as 'qualifiers' to determine if, e.g., nanomaterials cannot be released from products, which may justify waiving of testing. The four main groups encompass (1) soluble, (2) biopersistent high aspect ratio, (3) passive, and (4) active nanomaterials. The DF4nanoGrouping foresees a stepwise evaluation of nanomaterial properties and effects with increasing biological complexity. In case studies covering carbonaceous nanomaterials, metal oxide, and metal sulfate nanomaterials, amorphous silica and organic pigments (all nanomaterials having primary particle sizes below 100 nm), the usefulness of the DF4nanoGrouping for nanomaterial hazard assessment was confirmed. The DF4nanoGrouping facilitates grouping and targeted testing of nanomaterials. It ensures that sufficient data for the risk assessment of a nanomaterial are available, and it fosters the use of non-animal methods. No studies are performed that do not provide crucial data. Thereby, the DF4nanoGrouping serves to save both animals and resources.