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Recently, interest for the potential impact of consumer-relevant engineered nanoparticles on pregnancy has dramatically increased. This study investigates whether inhaled silver nanoparticles (AgNPs) reach and cross mouse placental barrier and induce adverse effects. Apart from their relevance for the growing use in consumer products and biomedical applications, AgNPs are selected since they can be unequivocally identified in tissues. Pregnant mouse females are exposed during the first 15 days of gestation by nose-only inhalation to a freshly produced aerosol of 18–20 nm AgNPs for either 1 or 4 h, at a particle number concentration of 3.80 × 107 part./cm−3and at a mass concentration of 640 μg/m³. AgNPs are identified and quantitated in maternal tissues, placentas and foetuses by transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy and single-particle inductively coupled plasma mass spectrometry. Inhalation of AgNPs results in increased number of resorbed foetuses associated with reduced oestrogen plasma levels, in the 4 h/day exposed mothers. Increased expression of pregnancy-relevant inflammatory cytokines is also detected in the placentas of both groups. These results prove that NPs are able to reach and cross the mouse placenta and suggest that precaution should be taken with respect to acute exposure to nanoparticles during pregnancy. [ABSTRACT FROM AUTHOR]

Successful gene therapy requires stability and sufficient bioavailability of the applied drug at the site of action. In the case of RNA interference (RNAi), non-viral vectors play a promising role for delivering intact siRNA molecules. We selected a low molecular weight polyethyleneimine (PEI F25-LMW) and investigated the biokinetics of PEI F25-LMW/siRNA polyplexes in comparison to non-complexed siRNA molecules upon intratracheal application into mice. Additionally, a bronchoalveolar lavage was performed to locate the siRNA within the different lung compartments and to analyse possible inflammatory reactions. Liquid scintillation counting of a 32P-label was used to follow the siRNA within the whole body. During the complete observation time more than 75% of the applied dose was found at the target site. The complexation with PEI F25- LMW prevented the siRNA from being degraded and cleared and prolonged its retention time. A low inflammatory reaction was observed on the basis of cell differentiation. Taken together, PEI F25-LMW meets fundamental requirements on non-viral vectors for local pulmonary siRNA delivery. [ABSTRACT FROM AUTHOR]

ENPRA was one of the earlier multidisciplinary European Commission FP7-funded projects aiming to evaluate the risks associated with nanomaterial (NM) exposure on human health across pulmonary, cardiovascular, hepatic, renal, and developmental systems. The outputs from this project have formed the basis of this review. A retrospective interpretation of the findings across a wide range of in vitro and in vivo studies was performed to identify the main highlights from the project. In particular, focus was placed on informing what advances were made in the hazard assessment of NM, as well as offering some suggestions on the future of “nanotoxicology research” based on these observations, shortcomings, and lessons learned from the project. A number of issues related to the hazard assessment of NM are discussed in detail and include use of appropriate NM for nanotoxicology investigations; characterization and dispersion of NM; use of appropriate doses for all related investigations; need for the correct choice of experimental models for risk assessment purposes; and full understanding of the test systems and correct interpretation of data generated from in vitro and in vivo systems. It is hoped that this review may assist in providing information in the implementation of guidelines, model systems, validation of assessment methodology, and integrated testing approaches for risk assessment of NM. It is vital to learn from ongoing and/or completed studies to avoid unnecessary duplication and offer suggestions that might improve different aspects of experimental design. [ABSTRACT FROM PUBLISHER]

Abstract: Nanoparticles (NP) and nanoparticulated drug delivery promise to be the breakthrough for therapy in medicine but raise concerns in terms of nanotoxicity. We present quantitative murine biokinetics assays using polyelectrolyte-multilayer-coated gold NP (AuNP, core diameter 15 and 80 nm; 198Au radio-labeled). Those were stably conjugated either with human serum albumin (alb-AuNP) or apolipoprotein E (apoE-AuNP), prior to intravenous injection. We compare the biokinetics of protein-AuNP-conjugates with citrate-stabilized AuNP (cit-AuNP). Biokinetics was complemented with histology in organs with high AuNP content using 15 nm double fluorescently-labeled alb-AuNP-conjugates. Protein conjugation massively reduced liver retention (alb-AuNP: 52%, apoE-AuNP: 72%, cit-AuNP: >95%, at 19 h and 48 h) when compared to cit-AuNP. The protein conjugates were retained in lungs (alb-AuNP (18%) and spleen (alb-AuNP (16%), apoE-AuNP (21%) at 19 h. Alb-AuNP show significantly increased fractions in lungs (factors: 60 (30 min); 111 (19 h); 235 (48 h) and brain (factors: 70 (30 min); 90 (19 h); >200 (48 h) compared to cit-AuNP (control) - or even to apoE-AuNP. The influence of protein conjugation on the biodistribution disappears for 80 nm AuNP comparing to control. Histologically, the 15 nm alb-AuNP are mainly located in the endothelium of brain, lungs, liver and kidneys after 30 min, while at 19 h they moved deeper into the parenchyma e.g. in hippocampus. Our study clearly suggests that stable conjugation of AuNP with albumin and apoE prior to intravenous administration increases specificity and efficiency of NP in diseased target-organs thus suggesting a potential role in nanomedicine and nanopharmacology. [Copyright &y& Elsevier]

Abstract: Airborne engineered nanoparticles undergo agglomeration, and careful distinction must be made between primary and agglomerate size of particles, when assessing their health effects. This study compares the effects on rats undergoing 15-day inhalation exposure to airborne agglomerates of gold nanoparticles (AuNPs) of similar size distribution and number concentration (1 × 106 particles/cm3), but two different primary diameters of 7 nm or 20 nm. Inhalation of agglomerates containing 7-nm AuNPs resulted in highest deposition by mass concentration in the lungs, followed by brain regions including the olfactory bulb, hippocampus, striatum, frontal cortex, entorhinal cortex, septum, cerebellum; aorta, esophagus, and kidney. Eight organs/tissues especially the brain retained greater mass concentration of Au after inhalation exposure to agglomerates of 7-nm than 20-nm AuNPs. Macrophage mediated escalation followed by fecal excretion is the major pathway of clearing inhaled AuNPs in the lungs. Microarray analyses of the hippocampus showed mostly downregulated genes, related to the cytoskeleton and neurite outgrowth. Together, results in this study indicate disintegration of nanosized agglomerates after inhalation and show impact of primary size of particles on subsequent biodistribution. [Copyright &y& Elsevier]

Abstract: Carbon nanotubes (CNTs) represent promising vectors to facilitate cellular drug delivery and to overcome biological barriers, but some types may also elicit persistent pulmonary inflammation based on their fibre characteristics. Here, we show the pulmonary response to aqueous suspensions of block copolymer dispersed, double-walled carbon nanotubes (DWCNT, length 1–10μm) in mice by bronchoalveolar lavage (BAL) analysis, and BAL and blood cytokine and lung antioxidant profiling. The intratracheally instilled dose of 50μg DWCNT caused significant pulmonary inflammation that was not resolved during a 7-day observation period. Light microscopy investigation of the uptake of DWCNT agglomerates revealed no particle ingestion for granulocytes, but only for macrophages. Accumulating macrophage, multinucleated macrophage and lymphocyte numbers in the alveolar region further indicated ineffective resolution with chronification of the inflammation. The local inflammatory impairment of the lung was accompanied by pulmonary antioxidant depletion and haematological signs of systemic inflammation. While the observed inflammation during its acute phase was dominated by neutrophils and neutrophil recruiting cytokines, the contribution of macrophages and lymphocytes with related cytokines became more significant after day 3 of exposure. This study confirms that acute pulmonary toxicity can occur on exposure of high doses of DWCNT agglomerates and offers further insight for improved nanotube design parameters to avoid potential long-term toxicity. [Copyright &y& Elsevier]

The intensive use of nano-sized particles in many different applications necessitates studies on their risk assessment as there are still open questions on their safe handling and utilization. For reliable risk assessment, the interaction of nanoparticles (NP) with biological systems after various routes of exposure needs to be investigated using well-characterized NP. We report here on the generation of gold-NP (Au-NP) aerosols for inhalation studies with the spark ignition technique, and their characterization in terms of chemical composition, physical structure, morphology, and specific surface area, and on interaction with lung tissues and lung cells after 1 h inhalation by mice. The originally generated agglomerated Au-NP were converted into compact spherical Au-NP by thermal annealing at 600 °C, providing particles of similar mass, but different size and specific surface area. Since there are currently no translocation data available on inhaled Au-NP in the 10-50 nm diameter range, the emphasis was to generate NP as small as 20 nm for inhalation in rodents. For anticipated in vivo systemic translocation and dosimetry analyses, radiolabeled Au-NP were created by proton irradiating the gold electrodes of the spark generator, thus forming gamma ray emitting Au with 186 days half-life, allowing long-term biokinetic studies. The dissolution rate of Au from the NP was below detection limits. The highly concentrated, polydisperse Au-NP aerosol (1-2 × 10 NP/cm) proved to be constant over several hours in terms of its count median mobility diameter, its geometric standard deviation and number concentration. After collection on filters particles can be re-suspended and used for instillation or ingestion studies. [ABSTRACT FROM AUTHOR]

Abstract: We studied the transport and deposition of quasi-monodisperse nanoparticles (with mobility diameter d m ranging from 1nm to 52nm) inside an extrathoracic airway model (which showed all relevant features of a computed tomography based model) by numerical simulation and, for part of the size range , by experimental measurement. For each particle size, three physiologically relevant steady inspiratory flow rates (Q=10, 20 and ) were considered. The validation of the numerical results consisted of (i) a comparison of numerical flow results to available Particle Image Velocimetry and Large-Eddy Simulation data and (ii) a comparison of numerical particle deposition simulations to new nanoparticle deposition measurements as well as previously published experimental and numerical deposition data. Computations of the laminar-turbulent flow were carried out using an open-source steady-state solver in conjunction with the SST turbulence model. The particle motion and their subsequent deposition was computed by the so-called Eulerian mass transport model. Quasi-monodisperse carbon nanoparticles were generated by spark ignition and their deposition was measured in a cast of the extrathoracic airway model. Both simulations and experiments showed that particle deposition increases with decreasing flow rate and decreasing particle size. A direct comparison between our numerical and all available experimental deposition results in fact showed a good overall agreement in the entire flow and size range. In the particle size range that could be studied experimentally in the same extrathoracic airway model geometry , absolute differences were of the order of a few percent, in the face of very low deposition fractions in this nanoparticle size range (with all experimental deposition fractions less than 5%). However, when normalizing to the largest deposition for the smallest flow rate , the dependency on flow rate was very similar between experiments and simulations. An adjustment of the turbulent Schmidt number (0.9–0.5) led to a slightly better agreement with experimental values. Finally, the simulations also showed that within the extrathoracic model, particular deposition patterns appeared that were similar for different particle sizes, however with more marked deposition hot-spots for the smallest particle size. [Copyright &y& Elsevier]

With the increasing use and incorporation of nanoparticles (NPs) into consumer products, screening for potential toxicity is necessary to ensure customer safety. NPs have been shown to translocate to the bloodstream following inhalation and ingestion, and such studies demonstrate that the liver is an important organ for accumulation. Silver (Ag) NPs are highly relevant for human exposure due to their use in food contact materials, dietary supplements, and antibacterial wound treatments. Due to the large number of different NPs already used in various products and being developed for new applications, it is essential that relevant, quick, and cheap methods of in vitro risk assessment suitable for these new materials are established. Therefore, this study used a simple hepatocytes model combined with an in vivo injection model to simulate the passage of a small amount of NPs into the bloodstream following exposure, e.g., via ingestion or inhalation, and examined the potential of Ag NPs of 20nm diameter to cause toxicity, inflammation, and oxidative stress in the liver following in vivo exposures of female Wistar rats via iv injection to 50 μg of NPs and in vitro exposures using the human hepatocyte cell line C3A. We found that Ag NPs were highly cytotoxic to hepatocytes (LC50 lactate dehydrogenase: 2.5 μg/cm2) and affected hepatocyte homeostasis by reducing albumin release. At sublethal concentrations with normal cell or tissue morphology, Ag NPs were detected in cytoplasm and nuclei of hepatocytes. We observed similar effects of Ag NPs on inflammatory mediator expression in vitro and in vivo with increase of interleukin-8 (IL-8)/macrophage inflammatory protein 2, IL-1RI, and tumor necrosis factor-α expression in both models and increased IL-8 protein release in vitro. This article presents evidence of the potential toxicity and inflammogenic potential of Ag NPs in the liver following ingestion. In addition, the similarities between in vitro and in vivo responses are striking and encouraging for future reduction, refinement, and replacement of animal studies by the use of hepatocyte cell lines in particle risk assessment. [ABSTRACT FROM PUBLISHER]

Abstract: The introduction of engineered nanostructured materials into a rapidly increasing number of industrial and consumer products will result in enhanced exposure to engineered nanoparticles. Workplace exposure has been identified as the most likely source of uncontrolled inhalation of engineered aerosolized nanoparticles, but release of engineered nanoparticles may occur at any stage of the lifecycle of (consumer) products. The dynamic development of nanomaterials with possibly unknown toxicological effects poses a challenge for the assessment of nanoparticle induced toxicity and safety. In this consensus document from a workshop on in-vitro cell systems for nanoparticle toxicity testing 1 [1] Workshop on ‘In-Vitro Exposure Studies for Toxicity Testing of Engineered Nanoparticles’ sponsored by the Association for Aerosol Research (GAeF), 5–6 September 2009, Karlsruhe, Germany. an overview is given of the main issues concerning exposure to airborne nanoparticles, lung physiology, biological mechanisms of (adverse) action, in-vitro cell exposure systems, realistic tissue doses, risk assessment and social aspects of nanotechnology. The workshop participants recognized the large potential of in-vitro cell exposure systems for reliable, high-throughput screening of nanoparticle toxicity. For the investigation of lung toxicity, a strong preference was expressed for air–liquid interface (ALI) cell exposure systems (rather than submerged cell exposure systems) as they more closely resemble in-vivo conditions in the lungs and they allow for unaltered and dosimetrically accurate delivery of aerosolized nanoparticles to the cells. An important aspect, which is frequently overlooked, is the comparison of typically used in-vitro dose levels with realistic in-vivo nanoparticle doses in the lung. If we consider average ambient urban exposure and occupational exposure at 5mg/m3 (maximum level allowed by Occupational Safety and Health Administration (OSHA)) as the boundaries of human exposure, the corresponding upper-limit range of nanoparticle flux delivered to the lung tissue is 3×10−5–5×10-3 μg/h/cm2 of lung tissue and 2–300particles/h/(epithelial) cell. This range can be easily matched and even exceeded by almost all currently available cell exposure systems. The consensus statement includes a set of recommendations for conducting in-vitro cell exposure studies with pulmonary cell systems and identifies urgent needs for future development. As these issues are crucial for the introduction of safe nanomaterials into the marketplace and the living environment, they deserve more attention and more interaction between biologists and aerosol scientists. The members of the workshop believe that further advances in in-vitro cell exposure studies would be greatly facilitated by a more active role of the aerosol scientists. The technical know-how for developing and running ALI in-vitro exposure systems is available in the aerosol community and at the same time biologists/toxicologists are required for proper assessment of the biological impact of nanoparticles. [Copyright &y& Elsevier]

Abstract: Gold nanoparticles (GNP) provide many opportunities in imaging, diagnostics, and therapies of nanomedicine. Hence, their biokinetics in the body are prerequisites for specific tailoring of nanomedicinal applications and for a comprehensive risk assessment. We administered 198Au-radio-labelled monodisperse, negatively chargedGNP of five different sizes (1.4, 5, 18, 80, and 200nm) and 2.8nm GNP with opposite surface charges by intravenous injection into rats. After 24h, the biodistribution of the GNP was quantitatively measuredby gamma-spectrometry. The size and surface charge of GNP strongly determine the biodistribution. Most GNP accumulated in the liver increased from 50% of 1.4nm GNP to >99% of 200nm GNP. In contrast, there was little size-dependent accumulation of 18–200nm GNP in most other organs. However, for GNP between 1.4nm and 5nm, the accumulation increased sharply with decreasing size; i.e. a linear increase with the volumetric specific surface area. The differently charged 2.8nm GNP led to significantly different accumulations in several organs. We conclude that the alterations of accumulation in the various organs and tissues, depending on GNP size and surface charge, are mediated by dynamic protein binding and exchange. A better understanding of these mechanisms will improve drug delivery and dose estimates used in risk assessment. [Copyright &y& Elsevier]

Abstract: RNA interference (RNAi) is a promising strategy to inhibit the expression of pathologically relevant genes, which show aberrant (over-)expression, e.g. in tumors or other pathologies. The induction of RNAi relies on small interfering RNAs (siRNAs), which trigger the specific mRNA degradation. Their instability and poor delivery into target tissues including the lung, however, so far severely limits the therapeutic use of siRNAs and requires the development of nanoscale delivery systems. Polyethylenimines (PEIs) are synthetic polymers, which are able to form non-covalent complexes with siRNAs. These nanoscale complexes (’nanoplexes’) allow the protection of siRNAs from nucleolytic degradation, their efficient cellular uptake through endocytosis and intracellular release through the ’proton sponge effect’. Chemical modifications of PEIs as well as the coupling of cell/tissue-specific ligands are promising approaches to increase the biocompatibility, specificity and efficacy of PEI-based nanoparticles. This review article gives a comprehensive overview of pre-clinical in vivo studies on the PEI-mediated delivery of therapeutic siRNAs in various animal models. It discusses the chemical properties of PEIs and PEI modifications, and their influences on siRNA knockdown efficacy, on adverse effects of the polymer or the nanoplex and on siRNA biodistribution in vivo. Beyond systemic application, PEI-based complexation allows the local siRNA application to the lung. Biodistribution studies demonstrate cellular uptake of PEI-complexed, but not of naked siRNAs in the lung with little systemic availability of the siRNAs, indicating the usefulness of this approach for the targeting of genes, which are pathologically relevant in lung tumors or lung metastases. Taken together, (i) PEI and PEI derivatives may represent an efficient delivery platform for siRNAs, (ii) siRNA-mediated induction of RNAi is a promising approach for the knockdown of pathologically relevant genes, and (iii) when sufficiently addressing biocompatibility issues, the locoregional delivery of PEI/siRNA complexes may become an attractive therapeutic strategy for the treatment of lung diseases with little systemic side effects. [Copyright &y& Elsevier]

Industrially manufactured titanium dioxide nanoparticles have been successfully radiolabelled with V by irradiation with a cyclotron-generated proton beam. Centrifugation tests showed that the V radiolabels were stably bound within the nanoparticle structure in an aqueous medium, while X-ray diffraction indicated that no major structural modifications to the nanoparticles resulted from the proton irradiation. In vitro tests of the uptake of cold and radiolabelled nanoparticles using the human cell line Calu-3 showed no significant difference in the uptake between both batches of nanoparticles. The uptake was quantified by Inductively Coupled Plasma Mass Spectrometry and high resolution γ-ray spectrometry for cold and radiolabelled nanoparticles, respectively. These preliminary results indicate that alterations to the nanoparticles’ properties introduced by proton bombardment can be controlled to a sufficient extent that their further use as radiotracers for biological investigations can be envisaged and elaborated. [ABSTRACT FROM AUTHOR]

Abstract: Besides toxicity tests, biokinetic studies are a fundamental part of investigations to evaluate a safe and sustainable use of nanoparticles. Today, gold nanoparticles (Au NPs) are known to be a versatile tool in different areas such as science, engineering or medicine. In this study, we investigated the biokinetics after intravenous and intratracheal applications of poly(ethylene glycol) (PEG) modified Au NPs compared to plain Au NPs. Radioactive-labeled Au NPs of 5 nm inorganic core diameter were applied to rats and the NP content in tissues, organs and excretion were quantified after 1-hour and 24-hours. After intravenous injection, a prolonged blood circulation time was determined for Au NPs with 10 kDa PEG chains. Non-PEGylated Au NPs and 750 Da PEG Au NPs accumulated mostly in liver and spleen. After intratracheal application the majority of all three types of applied NPs stayed in the lungs: the total translocation towards the circulation did not differ considerably after PEGylation of the Au NPs. However, a prolonged retention time in the circulation was detected for the small fraction of translocated 10 kDa PEG Au NPs, too. [Copyright &y& Elsevier]

Abstract: Nanoparticles (NPs) are being used within diverse applications such as medicines, clothing, cosmetics and food. In order to promote the safe development of such nanotechnologies it is essential to assess the potential adverse health consequences associated with human exposure. The liver is recognised as a target site for NP toxicity, due to NP accumulation within this organ subsequent to injection, inhalation or instillation. The uptake of fluorescent polystyrene carboxylated particles (20 nm or 200 nm diameter) by hepatocytes was determined using confocal microscopy; with cells imaged “live” during particle exposure or after exposure within fixed cells. Comparisons between the uptake of polystyrene particles by primary rat hepatocytes, and human hepatocyte cell lines (C3A and HepG2) were made. Uptake of particles by hepatocytes was size, time, and serum dependent. Specifically, the uptake of 200 nm particles was limited, but 20 nm NPs were internalised by all cell types from 10 min onwards. At 10 min, 20 nm NP fluorescence co-localised with the tubulin cytoskeleton staining; after 30 min NP fluorescence compartmentalised into structures located within and/or between cells. The fate of internalised NPs was considered and they were not contained within early endosomes or lysosomes, but within mitochondria of cell lines. NPs accumulated within bile canaliculi to a limited extent, which suggests that NPs can be eliminated within bile. This is in keeping with the finding that gold NPs were eliminated in bile following intravenous injection into rats. The findings were, in the main, comparable between primary rat hepatocytes and the different human hepatocyte cell lines. [Copyright &y& Elsevier]

BACKGROUND: Numerous studies have shown associations between ambient air pollution and daily mortality. OBJECTIVES: Our goal was to investigate the association of ambient air pollution and daily mortality in Erfurt, Germany, over a 10.5-year period after the German unification, when air quality improved. METHODS: We obtained daily mortality counts and data on mass concentrations of particulate matter (PM) <10 µm in aerodynamic diameter (PM10), gaseous pollutants, and meteorology in Erfurt between October 1991 and March 2002. We obtained ultrafine particle number concentrations (UFP) and mass concentrations of PM <2.5 µm in aerodynamic diameter (PM2.5) from September 1995 to March 2002. We analyzed the data using semiparametric Poisson regression models adjusting for trend, seasonality, influenza epidemics, day of the week, and meteorology. We evaluated cumulative associations between air pollution and mortality using polynomial distributed lag (PDL) models and multiday moving averages of air pollutants. We evaluated changes in the associations over time in time-varying coefficient models. RESULTS: Air pollution concentrations decreased over the study period. Cumulative exposure to UFP was associated with increased mortality. An interquartile range (IQR) increase in the 15-day cumulative mean UFP of 7,649 cm--3 was associated with a relative risk (RR) of 1.060 [95% confidence interval (CI), 1.008--1.114] for PDL models and an RR/IQR of 1.055 (95% CI, 1.011--1.101) for moving averages. RRs decreased from the mid-1990s to the late 1990s. CONCLUSION: Results indicate an elevated mortality risk from short-term exposure to UFP. They further suggest that RRs for short-term associations of air pollution decreased as pollution control measures were implemented in Eastern Germany. [ABSTRACT FROM AUTHOR]

The link between elevated concentrations of ambient particulate matter (PM) and increased mortality has been investigated in numerous studies. Here we analyzed the role of different particle size fractions with respect to total and cardio-respiratory mortality in Erfurt, Germany, between 1995 and 2001.Number concentrations (NC) of PM were measured using an aerosol spectrometer consisting of a Differential Mobility Particle Sizer and a Laser Aerosol Spectrometer to characterize particles between 0.01 and 0.5 and between 0.1 and 2.5 μm, respectively. We derived daily means of particle NC for ultrafine (0.01–0.1 μm) and for fine particles (0.01–2.5 μm). Assuming spherical particles of a constant density, we estimated the mass concentrations (MC) of particles in these size ranges. Concurrently, data on daily total and cardio-respiratory death counts were obtained from local health authorities. The data were analyzed using Poisson Generalized Additive Models adjusting for trend, seasonality, influenza epidemics, day of the week, and meteorology using smooth functions or indicator variables. We found statistically significant associations between elevated ultrafine particle (UFP; diameter: 0.01–0.1 μm) NC and total as well as cardio-respiratory mortality, each with a 4 days lag. The relative mortality risk (RR) for a 9748 cm−3 increase in UFP NC was RR=1.029 and its 95% confidence interval (CI)=1.003–1.055 for total mortality. For cardio-respiratory mortality we found: RR=1.031, 95% CI: 1.003–1.060. No association between fine particle MC and mortality was found.This study shows that UFP, representing fresh combustion particles, may be an important component of urban air pollution associated with health effects.Journal of Exposure Science and Environmental Epidemiology (2007) 17, 458–467; doi:10.1038/sj.jes.7500538; published online 15 November 2006 [ABSTRACT FROM AUTHOR]

BACKGROUND: There is ongoing discussion that inhaled nanoparticles (NPs, < 100 nm) may translocate from epithelial deposition sites of the lungs to systemic circulation. OBJECTIVES AND METHODS: We studied the disappearance of NPs from the epithelium by sequential lung retention and clearance and bronchoalveolar lavage (BAL) measurements in healthy adult Wistar Kyoto (WKY) rats at various times over 6 months after administration of a single 60- to 100-min intratracheal inhalation of iridium-192 (192Ir)--radiolabeled NPs. A complete 192Ir balance of all organs, tissues, excretion, remaining carcass, and BAL was performed at each time point. RESULTS: Directly after inhalation we found free NPs in the BAL; later, NPs were predominantly associated with alveolar macropages (AMs). After 3 weeks, lavageable NP fractions decreased to 0.06 of the actual NP lung burden. This is in stark contrast to the AM-associated fraction of micron-sized particles reported in the literature. These particles remained constant at about 0.8 throughout a 6-month period. Three weeks after inhalation, 80% of the retained Ir NPs was translocated into epithelium and interstitium. CONCLUSION: There is a strong size-selective difference in particle immobilization. Furthermore, AM-mediated NP transport to the larynx originates not only from the NP fraction retained on the epithelium but also from NPs being reentrained from the interstitium to the luminal side of epithelium. We conclude that NPs are much less phagocytized by AMs than large particles but are effectively removed from the lung surface into the interstitium. Even from these interstitial sites, they undergo AM-mediated long-term NP clearance to the larynx. [ABSTRACT FROM AUTHOR]

Abstract: Ferrimagnetic iron oxide particles were inhaled by 17 healthy volunteers (9 non-smokers, 8 smokers), and the retained particles were magnetized and detected by a SQUID. Stochastic particle transport due to cytoskeletal reorganizations within macrophages (relaxation) and directed particle motion in a weak magnetic twisting field were investigated with respect to viscous and elastic properties of the cytoskeleton. Relaxation and cytoskeletal stiffness were not influenced by cigarette smoking. Relaxation and particle twisting revealed a non-Newtonian viscosity with a pure viscous and a viscoelastic compartment. Viscous and elastic data obtained from relaxation correlated with particle twisting, indicating that the proposed simple model is a reasonable approximation of cytoskeletal mechanical properties. [Copyright &y& Elsevier]

Previous studies have shown an association between elevated concentrations of particulate air pollution and cardiovascular morbidity and mortality. Therefore, the association between daily variation of ultrafine and fine particulate air pollution and cardiac autonomic control measured as heart rate variability (HRV) was studied in a large multicenter study in Amsterdam, the Netherlands, Erfurt, Germany, and Helsinki, Finland. Elderly subjects (n=37 in Amsterdam, n=47 in both Erfurt and Helsinki) with stable coronary artery disease were followed for 6 months with biweekly clinical visits. During the visits, ambulatory electrocardiogram was recorded during a standardized protocol including a 5-min period of paced breathing. Time and frequency domain analyses of HRV were performed. A statistical model was built for each center separately. The mean 24-h particle number concentration (NC) (1000/cm3) of ultrafine particles (diameter 0.01–0.1 μm) was 17.3 in Amsterdam, 21.1 in Erfurt, and 17.0 in Helsinki. The corresponding values for PM2.5 were 20.0, 23.1, and 12.7 μg/m3. During paced breathing, ultrafine particles, NO2, and CO were at lags of 0–2 days consistently and significantly associated with decreased low-to-high frequency ratio (LF/HF), a measure of sympathovagal balance. In a pooled analysis across the centers, LF/HF decreased by 13.5% (95% confidence interval: −20.1%, −7.0%) for each 10,000/cm3 increase in the NC of ultrafine particles (2-day lag). PM2.5 was associated with reduced HF and increased LF/HF in Helsinki, whereas the opposite was true in Erfurt, and in Amsterdam, there were no clear associations between PM2.5 and HRV. The results suggest that the cardiovascular effects of ambient ultrafine and PM2.5 can differ from each other and that their effect may be modified by the characteristics of the exposed subjects and the sources of PM2.5.Journal of Exposure Science and Environmental Epidemiology (2006) 16, 332–341. doi:10.1038/sj.jea.7500460; published online 5 October 2005 [ABSTRACT FROM AUTHOR]

Abstract: A generator for the production of radiolabelled ultrafine carbonaceous particles for inhalation and clearance studies is described. A Technegas generator in combination with Tc labelling is a device used in clinical routine to investigate the ventilation of the human lung. However, under standard operating conditions the Technegas generator does not provide ultrafine particles with a stable radiolabel. The removal of saline from the Tc-eluate by an ion exchange column yielded low leaching rates of the radiolabel from the particles of below 4% within 24h (12% under standard conditions) and guaranteed non-hygroscopic aerosol properties. Short burning times (2s; standard 15s) and immediate dilution of the generated aerosol into a conductive bag yielded stable ultrafine particles in the size range between 40 and 100nm count median diameter (standard 200nm), with a geometric standard deviation of 1.6. We adapted the generator to a bolus inhalation system, allowing regional aerosol deposition into different lung regions and appropriate clearance studies. In addition the particles can be labelled by In instead of Tc, extending the investigation time of clearance studies from 1day to some weeks. [Copyright &y& Elsevier]

High concentrations of airborne particles have been associated with increased pulmonary and cardiovascular mortality, with indications of a specific toxicologic role for ultrafine particles (UFPs; particles < 0.1 µm). Within hours after the respiratory system is exposed to UFPs, the UFPs may appear in many compartments of the body, including the liver, heart, and nervous system. To date, the mechanisms by which UFPs penetrate boundary membranes and the distribution of UFPs within tissue compartments of their primary and secondary target organs are largely unknown. We combined different experimental approaches to study the distribution of UFPs in lungs and their uptake by cells. In the in vivo experiments, rats inhaled an ultrafine titanium dioxide aerosol of 22 nm count median diameter. The intrapulmonary distribution of particles was analyzed 1 hr or 24 hr after the end of exposure, using energy-filtering transmission electron microscopy for elemental microanalysis of individual particles. In an in vitro study, we exposed pulmonary macrophages and red blood cells to fluorescent polystyrene microspheres (1, 0.2, and 0.078 µm) and assessed particle uptake by confocal laser scanning microscopy. Inhaled ultrafine titanium dioxide particles were found on the luminal side of airways and alveoli, in all major lung tissue compartments and cells, and within capillaries. Particle uptake in vitro into cells did not occur by any of the expected endocytic processes, but rather by diffusion or adhesive interactions. Particles within cells are not membrane bound and hence have direct access to intracellular proteins, organelles, and DNA, which may greatly enhance their toxic potential. [ABSTRACT FROM AUTHOR]

Summary: A summary of a critical review by a working group of the German commission on Air Pollution Prevention of VDI and DIN of the actual data on exposure and health effects (excluding cancer) of fine particulate air pollution is presented. Exposure: Typical ambient particle concentrations for PM10 (PM2.5) in Germany are in the range of 10 – 45 (10 – 30) μg/m3 as annual mean and 50 – 200 (40 – 150) μg/m3 as maximum daily mean. The ratio of PM2.5/PM10 generally amounts between 0.7 and 0.9. Health effects: During the past 10 years many new epidemiological and toxicological studies on health effects of particulate matter (PM) have been published. In summary, long-term exposure against PM for years or decades is associated with elevated total, cardiovascular, and infant mortality. With respect to morbidity, respiratory symptoms, lung growth, and function of the immune system are affected. Short-term studies show consistant associations of exposure to daily concentrations of PM with mortality and morbidity on the same day or the subsequent days. Patients with asthma, COPD, pneumonia, and other respiratory diseases as well as patients with cardio-vascular diseases and diabetes are especially affected. The strongest associations are found for PM2.5 followed by PM10, with no indication of a threshold value for the health effects. The data base for ultra fine particles is too small for final conclusions. The available toxicological data support the epidemiological findings and give hints as to the mechanisms of the effects. Conclusion: The working group concludes that a further reduction of the limit values proposed for 2005 will substantially reduce health risks due to particulate air pollution. Because of the strong correlation of PM10 with PM2.5 at most German sites there is no specific need for limit values of PM2.5 for Germany in addition to those of PM10. [Copyright &y& Elsevier]

Given the hypothesis that air pollution is associated with elevated blood pressure and heart rate, the effect of daily concentrations of air pollution on blood pressure and heart rate was assessed in 131 adults with coronary heart disease in Helsinki, Finland; Erfurt, Germany; and Amsterdam, the Netherlands. Blood pressure was measured by a digital monitor, and heart rate was calculated as beats per minute from an electrocardiogram recording with the patient in supine position. Particle concentrations were measured at central measuring sites. Linear regression was used to model the association between 24-hr mean concentrations of particles and blood pressure and heart rate. Estimates were adjusted for trend, day of week, temperature, barometric pressure, relative humidity, and medication use. Pooled effect estimates showed a small significant decrease in diastolic and systolic blood pressure in association with particulate air pollution; a slight decrease in heart rate was found. Of the three centers, Erfurt revealed the most consistent particle effects. The results do not support findings from previous studies that had shown an increase in blood pressure and heart rate in healthy individuals in association with particles. However, particle effects might differ in cardiac patients because of medication intake and disease status, both affecting the autonomic control of the heart. [ABSTRACT FROM AUTHOR]

Background: Physiologically based pharmacokinetic (PBPK) modeling is an important tool in predicting target organ dosimetry and risk assessment of nanoparticles (NPs). The methodology of building a multi-route PBPK model for NPs has not been established, nor systematically evaluated. In this study, we hypothesized that the traditional route-to-route extrapolation approach of PBPK modeling that is typically used for small molecules may not be appropriate for NPs. To test this hypothesis, the objective of this study was to develop a multi-route PBPK model for different sizes (1.4-200 nm) of gold nanoparticles (AuNPs) in adult rats following different routes of administration (i.e., intravenous (IV), oral gavage, intratracheal instillation, and endotracheal inhalation) using two approaches: a traditional route-to-route extrapolation approach for small molecules and a new approach that is based on route-specific data that we propose to be applied generally to NPs., Results: We found that the PBPK model using this new approach had superior performance than the traditional approach. The final PBPK model was optimized rigorously using a Bayesian hierarchical approach with Markov chain Monte Carlo simulations, and then converted to a web-based interface using R Shiny. In addition, quantitative structure-activity relationships (QSAR) based multivariate linear regressions were established to predict the route-specific key biodistribution parameters (e.g., maximum uptake rate) based on the physicochemical properties of AuNPs (e.g., size, surface area, dose, Zeta potential, and NP numbers). These results showed the size and surface area of AuNPs were the main determinants for endocytic/phagocytic uptake rates regardless of the route of administration, while Zeta potential was an important parameter for the estimation of the exocytic release rates following IV administration., Conclusions: This study suggests that traditional route-to-route extrapolation approaches for PBPK modeling of small molecules are not applicable to NPs. Therefore, multi-route PBPK models for NPs should be developed using route-specific data. This novel PBPK-based web interface serves as a foundation for extrapolating to other NPs and to humans to facilitate biodistribution estimation, safety, and risk assessment of NPs., (© 2022. The Author(s).)

Background: There is a steadily increasing quantity of silver nanoparticles (AgNP) produced for numerous industrial, medicinal and private purposes, leading to an increased risk of inhalation exposure for both professionals and consumers. Particle inhalation can result in inflammatory and allergic responses, and there are concerns about other negative health effects from either acute or chronic low-dose exposure., Results: To study the fate of inhaled AgNP, healthy adult rats were exposed to 1½-hour intra-tracheal inhalations of pristine 105 Ag-radiolabeled, 20 nm AgNP aerosols (with mean doses across all rats of each exposure group of deposited NP-mass and NP-number being 13.5 ± 3.6 μg, 7.9 ± 3.2•10 11 , respectively). At five time-points (0.75 h, 4 h, 24 h, 7d, 28d) post-exposure (p.e.), a complete balance of the [ 105 Ag]AgNP fate and its degradation products were quantified in organs, tissues, carcass, lavage and body fluids, including excretions. Rapid dissolution of [ 105 Ag]Ag-ions from the [ 105 Ag]AgNP surface was apparent together with both fast particulate airway clearance and long-term particulate clearance from the alveolar region to the larynx. The results are compatible with evidence from the literature that the released [ 105 Ag]Ag-ions precipitate rapidly to low-solubility [ 105 Ag]Ag-salts in the ion-rich epithelial lining lung fluid (ELF) and blood. Based on the existing literature, the degradation products rapidly translocate across the air-blood-barrier (ABB) into the blood and are eliminated via the liver and gall-bladder into the small intestine for fecal excretion. The pathway of [ 105 Ag]Ag-salt precipitates was compatible with auxiliary biokinetics studies at 24 h and 7 days after either intravenous injection or intratracheal or oral instillation of [ 110m Ag]AgNO 3 solutions in sentinel groups of rats. However, dissolution of [ 105 Ag]Ag-ions appeared not to be complete after a few hours or days but continued over two weeks p.e. This was due to the additional formation of salt layers on the [ 105 Ag]AgNP surface that mediate and prolonge the dissolution process. The concurrent clearance of persistent cores of [ 105 Ag]AgNP and [ 105 Ag]Ag-salt precipitates results in the elimination of a fraction > 0.8 (per ILD) after one week, each particulate Ag-species accounting for about half of this. After 28 days p.e. the cleared fraction rises marginally to 0.94 while 2/3 of the remaining [ 105 Ag]AgNP are retained in the lungs and 1/3 in secondary organs and tissues with an unknown partition of the Ag species involved. However, making use of our previous biokinetics studies of poorly soluble [ 195 Au]AuNP of the same size and under identical experimental and exposure conditions (Kreyling et al., ACS Nano 2018), the kinetics of the ABB-translocation of [ 105 Ag]Ag-salt precipitates was estimated to reach a fractional maximum of 0.12 at day 3 p.e. and became undetectable 16 days p.e. Hence, persistent cores of [ 105 Ag]AgNP were cleared throughout the study period. Urinary [ 105 Ag]Ag excretion is minimal, finally accumulating to 0.016., Conclusion: The biokinetics of inhaled [ 105 Ag]AgNP is relatively complex since the dissolving [ 105 Ag]Ag-ions (a) form salt layers on the [ 105 Ag]AgNP surface which retard dissolution and (b) the [ 105 Ag]Ag-ions released from the [ 105 Ag]AgNP surface form poorly-soluble precipitates of [ 105 Ag]Ag-salts in ELF. Therefore, hardly any [ 105 Ag]Ag-ion clearance occurs from the lungs but instead [ 105 Ag]AgNP and nano-sized precipitated [ 105 Ag]Ag-salt are cleared via the larynx into GIT and, in addition, via blood, liver, gall bladder into GIT with one common excretional pathway via feces out of the body.

In recent animal experiments with suspensions of radiolabeled TiO 2 nanoparticles large and highly variable radioactivity fractions were retained in disposable plastic syringes. After unloading between 10% and up to 70% of the loaded dose were still present in the syringes. As a consequence the effectively delivered nanoparticle dose to the animals was frequently much smaller than the nominal dose of the nanoparticles loaded into the syringe. The high variability of this nanoparticle retention challenges the application of a precise, predefined dose and creates a major error source when normalizing organ and tissue contents to the dose loaded into the syringe, which is usually set as the applied dose. A control study was performed employing six commonly used syringe types with seven types of radiolabeled oxide and metallic nanoparticles. For this purpose the syringes were loaded with a given volume of nanoparticle suspension, the radioactivity was measured, the syringe was unloaded and the activity measurement was repeated with the empty syringe. The highest retention values were found when using TiO 2 nanoparticle suspensions with Tuberkulin type syringes. In the worst case between 6.6% and 79.1% of the nanoparticles were retained in the syringe. When using the same nanoparticle suspension with an insulin-type syringe the retention was reduced to 1.4% to 20.6%. For amorphous silica nanoparticles the maximum observed retention was 8% and for Au nanoparticles it was 5.1%. Further data gathered from in vivo animal imaging studies show that nanoparticle retention in syringes also affects experiments with nanoparticles such as exosomes, polymersomes, and protein-based nanoparticles investigated for possible applications in nanomedicine. Since the retention is highly variable the effectively applied dose cannot be determined by applying a simple syringe retention factor. The present work shall alert to the problem and illustrate its possible magnitude and unpredictable variability. As mitigation strategy adequate checks with different syringe types are proposed in order to find out whether a given combination of syringe type and nanoparticle suspension is affected by nanoparticle retention and, if necessary, to select a different syringe type that minimizes retention., (Copyright © 2019 Holzwarth, Cossío, Llop and Kreyling.)

The increasing use of gold nanoparticles leads to a possible increase of exposure by inhalation. Therefore, we have studied the deposition patterns of inhaled 20 nm gold nanoparticles (AuNP) in 7-90 day old rats and their biokinetics in 60 day old ones. Wistar-Kyoto rats inhaled intratracheally 20 nm 195 Au-radiolabeled AuNP by negative pressure ventilation over 2 h. Immediately afterward lungs were excised, inflated and microwave dried. AuNP deposition was analyzed by single-photon emission computed tomography, computed-tomography and autoradiography. Completely balanced, quantitative biodistributions in major organs and all body tissues and total excretion were analyzed from 1 h to 28 d after inhalation. Intratracheal inhalation caused AuNP deposition predominately in the caudal lungs, independent of age. About 30% AuNP were deposited on airway epithelia and rapidly cleared by mucociliary clearance. About 80% of AuNP deposited in alveoli was relocated from the epithelium into the interstitium within 24 h and was inaccessible to broncho-alveolar lavage. During interstitial long-term retention, re-entrainment within macrophages back onto the lung epithelium and to the larynx and gastrointestinal tract (GIT) dominated AuNP clearance (rate 0.03 d -1 ) In contrast, AuNP-translocation across the air-blood barrier was much smaller leading to persistent retention in secondary organs and tissues in the ranking order liver > soft issue > spleen > kidneys > skeleton > blood > uterus > heart > brain. The age-independent, inhomogeneous AuNP deposition was probably caused by the negative pressure ventilation. Long-term AuNP clearance was dominated by macrophage-mediated transport from the interstitium to the larynx and GIT. Translocation across the rat air-blood barrier appeared to be similar to that of humans for similar sized AuNP.

Background: We previously showed that cerium oxide (CeO 2 ), barium sulfate (BaSO 4 ) 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: CeO 2 , silica-coated CeO 2 , BaSO 4 , 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 BaSO 4 and ZnO than that of the two CeO 2 NPs. The uptake of BaSO 4 in AMs was less than CeO 2 and silica-coated CeO 2 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.

Gold nanoparticles (AuNPs) have been extensively explored in biomedical applications, for example as drug carriers, contrast agents, or therapeutics. However, AuNP can exhibit cytotoxic profile, when the size is below 2 nm (ultrasmall AuNP; usAuNP) and when the stabilizing ligands allow for access to the gold surface either for the direct interaction with biomolecules or for catalytic activity of the unshielded gold surface. Furthermore, usAuNP exhibits significantly different biodistribution and enhanced circulation times compared to larger AuNP. This review gives an overview about the synthesis and the physico-chemical properties of usAuNP and, thereby, focusses on 1.4 nm sized AuNP, which are derived from the compound Au 55 (PPh 3 ) 12 Cl 6 and which are the most intensively studied usAuNP in the field. This part is followed by a summary of the toxic properties of usAuNP, which include in vitro cytotoxicity tests on different cell lines, electrophysiological tests following FDA guidelines as well as studies on antibacterial effects. Finally, the biodistribution and pharmacokinetics of ultrasmall AuNP are discussed and compared to the properties of more biocompatible, larger AuNP.

The biokinetics of inhaled nanoparticles (NP) is more complex than that of larger particles since NP may NP deposited on the nasal mucosa of the upper respiratory tract (URT) may translocate to the olfactory bulb of the brain and also via the trigeminus (URT neuronal route); and (b) NP deposited in the lower respiratory tract (LRT) may cross the ABB into blood and enter the brain across the blood-brain-barrier (BBB) or take a neuronal route from enervated tracheo-bronchial epithelia via the vagus nerve. Translocation from both - the URT and the LRT - are quantified during the first 24h after a 1-hour aerosol inhalation of 20nm-sized, (192)Ir radiolabeled iridium NP by healthy adult rats using differential exposures: (I) nose-only exposure of the entire respiratory tract or (II) intratracheal (IT) inhalation of intubated and ventilated rats, thereby bypassing the URT and extrathoracic nasal passages. After nose-only exposure brain accumulation (BrAcc) is significantly nine-fold higher than after IT inhalation since the former results from both pathways (a+b) while the latter exposure comes only from pathway (b). Interestingly, there are significantly more circulating NP in blood 24h after nose-only inhalation than after IT inhalation. Distinguishing translocation from URT versus LRT estimated from the differential inhalation exposures, the former is significantly higher (8-fold) than from the LRT. Although the BrAcc fraction is rather low compared to total NP deposition after this short-term exposure, this study proofs that inhaled insoluble NP can accumulate in the brain from both - URT and LRT which may trigger and/or modulate adverse health effects in the central nervous system (CNS) during chronic exposure., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Biokinetics data of lung-administered PEI F25-LMW/siRNA polyplexes within different lung compartments are presented. Thereby, at three different timepoints (1 h, 3 h, 8 h), the data was determined by calculations to the 32 P-radioactivity in the whole mouse body. Additionally, data was optimized to the available PEI F25-LMW/siRNA polyplexes in the target organ and therefore normalized to the sum of all lung compartments. Methods, other biokinetics data and the discussion of the results are published in " Biokinetic studies of non-complexed siRNA versus nano-sized PEI F25-LMW/siRNA polyplexes following intratracheal instillation into mice " (Lipka et al., 2016 [1]).

Researchers need to study the biokinetics of inhaled biopersistent nano- and micrometer-sized particles (NPs and μPs) to assess their toxicity and to develop an understanding of their potential risks. When particles are inhaled, they do not necessarily remain at their sites of deposition in the respiratory tract. Instead they can undergo numerous transport processes within the various tissues of the lungs, including clearance from the lungs. In this context, we would like to understand how the biokinetic studies performed in animals can be extrapolated to humans. Interestingly, the particle retention is much shorter in rodent lungs and declines much faster than it does in human, simian, and canine lungs. The predominant long-term clearance pathway for both NPs and μPs in humans and other animal species is macrophage-mediated particle transport from the peripheral lungs toward ciliated airways and the larynx. However, the transport rate is 10 times higher in rodents than in other species. In addition to particle clearance out of the lung, we also observe particle redistribution from the epithelium toward and within the interstitium and lymph nodes of the lung and particle translocation to blood circulation leading to subsequent accumulation in secondary organs. While μPs have limited access to interstitial spaces in the rodent lungs, NPs rapidly relocate in the epithelium and the underlying interstitium. By contrast, indirect evidence shows that both NPs and μPs are relocated into the epithelium and interstitial spaces of the human, simian, and canine lungs. Only NPs translocate into the circulatory system and subsequently accumulate in the secondary organs and tissues of the body. Translocated NP fractions are rather low, but they depend strongly on the physicochemical properties of the NP and their surface properties. Growing evidence indicates that the binding and conjugation of proteins to NPs play an essential role in translocation across cellular membranes and organ barriers. In summary, particle biokinetics result from a multitude of highly dynamic processes, which depend not only on physicochemical properties of the particles but also on a multitude of cellular and molecular responses and interactions. Given the rather small accumulation in secondary organs after acute inhalation exposures, it appears likely that adverse effects caused by NPs accumulated in secondary organs may only occur after chronic exposure over extended time periods. Therefore adverse health effects in secondary organs such as the cardiovascular system that are associated with chronic exposure of ambient urban air pollution are less likely to result from particle translocation. Instead, chronic particle inhalation could trigger or modulate the autonomous nervous system or the release of soluble mediators into circulation leading to adverse health effects.

Aim: To investigate the relationship of alveolar macrophages and inhaled nanoparticles (NPs) in the lung., Materials & Methods: Rats were exposed by inhalation to 16-nm gold NPs for 6 h, and ultramicroscopic observation on the frequency and localization of gold NPs within lavaged macrophages was performed for 7 days., Results & Discussion: The majority of macrophages examined on day 0 (94%) contained internalized gold NPs, and the percentage decreased to 59% on day 7. Gold NPs were exclusively found within cytoplasmic vesicles. On day 0, most gold NPs appeared to be individual or slightly agglomerated, while they were frequently agglomerated on day 7., Conclusion: Alveolar macrophages efficiently internalized NPs by endocytosis, and rearrangements of vesicles and of NPs in the vesicles of macrophages occurred.

The lung surface is an ideal pathway to the bloodstream for nanoparticle-based drug delivery. Thus far, research has focused on the lungs of adults, and little is known about nanoparticle behavior in the immature lungs of infants. Here, using nonlinear dynamical systems analysis and in vivo experimentation in developing animals, we show that nanoparticle deposition in postnatally developing lungs peaks at the end of bulk alveolation. This finding suggests a unique paradigm, consistent with the emerging theory that as alveoli form through secondary septation, alveolar flow becomes chaotic and chaotic mixing kicks in, significantly enhancing particle deposition. This finding has significant implications for the application of nanoparticle-based inhalation therapeutics in young children with immature lungs from birth to 2 y of age.

Background: The fate of gold nanoparticles, 2, 40 and 100 nm, administered intratracheally to adult female mice was examined. The nanoparticles were traced by autometallography (AMG) at both ultrastructural and light microscopic levels. Also, the gold content was quantified by inductively coupled plasma mass spectrometry (ICP-MS) and neutron activation analysis (NAA). The liver is the major site of deposition of circulating gold nanoparticles. Therefore the degree of translocation was determined by the hepatic deposition of gold. Mice were instilled with 5 intratracheal doses of gold nanoparticles distributed over a period of 3 weeks and were killed 24 h after the last dose. One group of mice were given a single intratracheal dose and were killed after 1 h., Results: The instilled nanoparticles were found in lung macrophages already 1 h after a single instillation. In mice instilled treated repeatedly during 3 weeks, the load was substantial. Ultrastructurally, AMG silver enhanced gold nanoparticles were found in lysosome-/endosome-like organelles of the macrophages and analysis with AMG, ICP-MS and NAA of the liver revealed an almost total lack of translocation of nanoparticles. In mice given repeated instillations of 2 nm gold nanoparticles, 1.4 per thousand (by ICP-MS) to 1.9 per thousand (by NAA) of the instilled gold was detected in the liver. With the 40 nm gold, no gold was detected in the liver (detection level 2 ng, 0.1 per thousand) except for one mouse in which 3 per thousand of the instilled gold was found in the liver. No gold was detected in any liver of mice instilled with 100 nm gold (detection level 2 ng, 0.1 per thousand) except in a single animal with 0.39 per thousand of the dose in the liver., Conclusion: We found that that: (1) inert gold nanoparticles, administered intratracheally are phagocytosed by lung macrophages; (2) only a tiny fraction of the gold particles is translocated into systemic circulation. (3) The translocation rate was greatest with the 2 nm gold particles.

The dose of inhaled radiolabeled aerosols is usually assessed using gamma (GC) camera imaging. Because of the complex and inhomogeneous structure of the lung, consisting of soft tissue, the thoracic skeleton, blood vessels, and air spaces, proper attenuation correction coefficients are difficult to evaluate and the estimated doses bear high uncertainty. One hundred milliliters of aerosol boli composed of 100 nm diameter (99m)Tc radiolabeled carbon particles (Technegas) were targeted either to the airways (AW) or to 800-mL volumetric lung depth (alveoli, AL) in 11 healthy volunteers. In addition, 750-mL full breaths (FB) of aerosol were inhaled to a 800-mL lung depth. The deposited dose was measured by collecting aerosol from inhaled and exhaled air stream on filters, which were analyzed for radioactivity. Lung imaging was performed using a planar GC (posterior). Ratios of GC counts to deposited dose (GC/DD) were similar after FB and AL administration, but twofold lower after AW administration (p < 0.01). Associated attenuation correction factors (ACF) were 2.5 +/- 0.5 (FB), 2.2 +/- 0.4 (AL), and 5.5 +/- 1.6 (AW, p < 0.01). Both GC/DD and ACF were highly correlated to the aerosol distribution index (central to peripheral ratio, C/P). After shallow bolus administration there was a negative correlation between body mass index and GC/DD. Inhalation of radioaerosols used in medical diagnosis and therapy in combination with high central airway deposition results in an underestimation of the deposited dose based on planar GC imaging. The aerosol distribution index C/P may provide one suitable indicator for corrections, which should be confirmed in future studies by individual attenuation analysis based on radiotracer transmission measurements.

Around the world, daily variations in ambient air pollution have been consistently associated with variations in daily mortality. The aim of the study presented here was to assess the effects of ambient air pollution on daily mortality during a period of tremendous changes in air quality in the city of Erfurt, in eastern Germany, from October 1991 to March 2002. Data on particle size distributions were obtained from September 1995 to March 2002 at a research monitoring station. For particles from 0.01 microm to 2.5 microm in diameter, number concentrations (NCs)* and mass concentrations (MCs) were calculated. Particles with diameters less than or equal to 0.10 microm are defined as ultrafine particles (UFP). Data on the gaseous pollutants NO2, CO, SO2, and O3 and on PM10 (particulate matter [PM] with aerodynamic diameter less than or equal to 10 microm) were obtained from a government air-monitoring station. Data on changes in energy consumption, car fleet composition, and population were collected from local authorities. Death certificates of persons living in and dying in Erfurt were abstracted, and daily mortality counts were calculated. Poisson regression models were used to analyze the data, applying penalized splines (also known as P-splines) to model nonlinear relationships in the confounders. Model selection was done without air pollutants in the models, based on a combination of goodness-of-fit criteria and avoidance of autocorrelation in error terms. Final models included P-splines of time trend, meteorologic data, and influenza epidemics as well as day of the week with an indicator variable. Results are presented as change per interquartile range (IQR), i.e., change in the relative risk of mortality associated with a change in the concentration from the 25th to the 75th percentile of a given pollutant. Air pollutants were considered both as linear terms and as P-splines to assess the exposure-response functions. Changes in effect estimates over time were calculated using fully Bayesian time-varying coefficient models. This method was selected over four other approaches tested in simulation studies. Air-pollution concentrations decreased substantially in Erfurt during the decade under observation. The strongest changes were observed for SO2, for which annual concentrations decreased from 64 microg/m3 in 1992 to 4 microg/m3 in 2001. Concentrations of PM10, PM2.5 (particulate matter with aerodynamic diameter less than or equal to 2.5 microm), and CO decreased by more than 50%. NO2, O3, and ultrafine particles also decreased, though to a lesser extent. Based on visual inspection of the data on the changes in ambient air-pollution concentrations during the study period, we defined three study subperiods: A first subperiod from 1991 to 1995; a second, transitional subperiod from 1995 to 1998; and a third subperiod from 1998 to 2002. Generally, air-pollution concentrations decreased substantially from the first subperiod to the second, and some additional decreases occurred from the second subperiod to the third. During the second, transitional subperiod, natural gas replaced coal as the main energy source in Erfurt. In addition, the number of cars with catalytic converters increased over time, as did the number of cars in general. To facilitate the interpretation of the results, we organized the air pollutants into four groups: (1) NO2, CO, and ultrafine particles, (2) PM10 and PM2.5, (3) SO2, and (4) O3. We observed a 1.6% increased risk for daily mortality (CI, -0.4% to 3.5%) for an increase of 19.7 microg/m3 in NO2 (lag day 3), a 1.9% increased risk (CI, 0.2%-3.6%) for an increase of 0.48 mg/m3 in CO (lag day 4), and a 2.9% increased risk (CI, 0.3%-5.5%) for an increase of 9743/cm3 in ultrafine particles (lag day 4). No consistent associations were observed for PM10, PM2.5, or SO2. For O3, a 4.6% increased risk for daily mortality (CI, 1.1%-8.3%) was associated with a 43.8 microg/m3 maximum 8-hr concentration of O3 per day (lag day 2). For all four pollutants, exposure-response functions suggested no deviation from linearity. However, in time-varying models the strongest associations were observed for NO2, CO, and ultrafine particles during the transition subperiod, from 1995 to 1998, when O3 concentrations were lowest. Changes in source characteristics or ambient air-pollution concentrations were not able to explain these observations in a straightforward manner. However, the observations suggested that changes such as the introduction of three-way catalytic converters in cars and the substitution natural gas for coal might have been beneficial. Overall we concluded that: 1. Economic and political changes and the adoption of new technologies in eastern Germany resulted in distinct improvements in ambient air quality; 2. Urban air pollution in Erfurt changed within one decade from the eastern mixture toward that of western Europe ("western mixture"), which is dominated by concentrations of NOx, O3, fine particles, and ultrafine particles with low concentrations of SO2; 3. There was an association between daily mortality and ultrafine particles and combustion-related gases (lag days 3 or 4); 4. Ultrafine particles seemed to be the best pollution indicator and to point to the role of local combustion in the pollution mixture; 5. Regression coefficients showed variation over time for NO2, CO, ultrafine particles, and O3 that could not be explained by nonlinearity in the exposure-response functions; 6. Mortality associated with pollution was lower at the end of the 1990s than during the 1990s, except for mortality associated with O3; and 7. Mortality associated with pollution was strongest in the second, transitional subperiod, from 1995 to 1998, when changes in source characteristics had taken place but the benefits of improved ambient air quality had not yet been completely achieved.

The role of macrophages in the clearance of particles with diameters less than 100 nm (ultrafine or nanoparticles) is not well established, although these particles deposit highly efficiently in peripheral lungs, where particle phagocytosis by macrophages is the primary clearance mechanism. To investigate the uptake of nanoparticles by lung phagocytes, we analyzed the distribution of titanium dioxide particles of 20 nm count median diameter in macrophages obtained by bronchoalveolar lavage at 1 hour and 24 hours after a 1-hour aerosol inhalation. Differential cell counts revealing greater than 96% macrophages and less than 1% neutrophils and lymphocytes excluded inflammatory cell responses. Employing energy-filtering transmission electron microscopy (EFTEM) for elemental microanalysis, we examined 1,594 macrophage profiles in the 1-hour group (n = 6) and 1,609 in the 24-hour group (n = 6). We found 4 particles in 3 macrophage profiles at 1 hour and 47 particles in 27 macrophage profiles at 24 hours. Model-based data analysis revealed an uptake of 0.06 to 0.12% ultrafine titanium-dioxide particles by lung-surface macrophages within 24 hours. Mean (SD) particle diameters were 31 (8) nm at 1 hour and 34 (10) nm at 24 hours. Particles were localized adjacent (within 13-83 nm) to the membrane in vesicles with mean (SD) diameters of 592 (375) nm at 1 hour and 414 (309) nm at 24 hours, containing other material like surfactant. Additional screening of macrophage profiles by conventional TEM revealed no evidence for agglomerated nanoparticles. These results give evidence for a sporadic and rather unspecific uptake of TiO(2)-nanoparticles by lung-surface macrophages within 24 hours after their deposition, and hence for an insufficient role of the key clearance mechanism in peripheral lungs.

Rationale: Little is known about clearance of ultrafine carbon particles from the different regions of the human lung. These particles may accumulate and present a health hazard because of their high surface area., Objectives: Technetium Tc 99m ((99m)Tc)-radiolabeled 100-nm-diameter carbon particles were inhaled by healthy nonsmokers, asymptomatic smokers, and by patients with chronic obstructive pulmonary disease (COPD)., Methods: Using a bolus inhalation technique, particle deposition was targeted either to the airways or to the lung periphery, and retention, clearance, and translocation were measured using retained radiotracer imaging., Measurements and Main Results: In vitro studies revealed that mean leaching of soluble (99m)Tc-radiotracer from the carbon particles was 4.1 (2.6 [SD]) % after 24 hours. Cumulative (99m)Tc activity in urine at 24 hours was 1.1 (1.3) % of activity deposited in the lungs. In the lung periphery, particle retention was not affected by smoking or pulmonary disease; retention was 96 (3) % after 24 hours. The small amount of clearance could be attributed to leaching of the (99m)Tc label, suggesting negligible particle clearance. In healthy nonsmokers, retention of particles targeted to the airways was 89 (6) and 75 (10) % after 1.5 and 24 hours, respectively. Radiolabel activity did not accumulate in the liver., Conclusions: Within the limits of detection of our experimental system, most inhaled ultrafine carbon particles are retained in the lung periphery and in the conducting airways without substantial systemic translocation or accumulation in the liver at 48 hours. Repeated exposure may result in significant pulmonary accumulation of ultrafine particles.

During the last few years, research on toxicologically relevant properties of engineered nanoparticles has increased tremendously. A number of international research projects and additional activities are ongoing in the EU and the US, nourishing the expectation that more relevant technical and toxicological data will be published. Their widespread use allows for potential exposure to engineered nanoparticles during the whole lifecycle of a variety of products. When looking at possible exposure routes for manufactured Nanoparticles, inhalation, dermal and oral exposure are the most obvious, depending on the type of product in which Nanoparticles are used. This review shows that (1) Nanoparticles can deposit in the respiratory tract after inhalation. For a number of nanoparticles, oxidative stress-related inflammatory reactions have been observed. Tumour-related effects have only been observed in rats, and might be related to overload conditions. There are also a few reports that indicate uptake of nanoparticles in the brain via the olfactory epithelium. Nanoparticle translocation into the systemic circulation may occur after inhalation but conflicting evidence is present on the extent of translocation. These findings urge the need for additional studies to further elucidate these findings and to characterize the physiological impact. (2) There is currently little evidence from skin penetration studies that dermal applications of metal oxide nanoparticles used in sunscreens lead to systemic exposure. However, the question has been raised whether the usual testing with healthy, intact skin will be sufficient. (3) Uptake of nanoparticles in the gastrointestinal tract after oral uptake is a known phenomenon, of which use is intentionally made in the design of food and pharmacological components. Finally, this review indicates that only few specific nanoparticles have been investigated in a limited number of test systems and extrapolation of this data to other materials is not possible. Air pollution studies have generated indirect evidence for the role of combustion derived nanoparticles (CDNP) in driving adverse health effects in susceptible groups. Experimental studies with some bulk nanoparticles (carbon black, titanium dioxide, iron oxides) that have been used for decades suggest various adverse effects. However, engineered nanomaterials with new chemical and physical properties are being produced constantly and the toxicity of these is unknown. Therefore, despite the existing database on nanoparticles, no blanket statements about human toxicity can be given at this time. In addition, limited ecotoxicological data for nanomaterials precludes a systematic assessment of the impact of Nanoparticles on ecosystems.