Measurement techniques for respiratory tract deposition of airborne nanoparticles: a critical review

Design, development, and technical considerations for dry powder inhaler devices

The dry powder inhaler (DPI) stands out as a highly patient-friendly and effective pulmonary formulation, surpassing traditional and other pulmonary dosage forms in certain disease conditions. The development of DPI products, however, presents more complexities than that of other dosage forms, particularly in device design and the integration of the drug formulation. This review focuses on the capabilities of DPI devices in pulmonary drug delivery, with a special emphasis on device design and formulation development. It also discusses into the principles of deep lung particle deposition and device engineering, and provides a current overview of the market for DPI devices. Furthermore, the review highlights the use of computational fluid dynamics (CFD) in DPI product design and discusses the regulatory environment surrounding these devices.

Applications and advancements of nanoparticle-based drug delivery in alleviating lung cancer and chronic obstructive pulmonary disease

Lung cancer (LC) and chronic obstructive pulmonary disease (COPD) are among the leading causes of mortality worldwide. Cigarette smoking is among the main aetiologic factors for both ailments. These diseases share common pathogenetic mechanisms including inflammation, oxidative stress, and tissue remodelling. Current therapeutic approaches are limited by low efficacy and adverse effects. Consequentially, LC has a 5-year survival of < 20%, while COPD is incurable, underlining the necessity for innovative treatment strategies. Two promising emerging classes of therapy against these diseases include plant-derived molecules (phytoceuticals) and nucleic acid-based therapies. The clinical application of both is limited by issues including poor solubility, poor permeability, and, in the case of nucleic acids, susceptibility to enzymatic degradation, large size, and electrostatic charge density. Nanoparticle-based advanced drug delivery systems are currently being explored as flexible systems allowing to overcome these limitations. In this review, an updated summary of the most recent studies using nanoparticle-based advanced drug delivery systems to improve the delivery of nucleic acids and phytoceuticals for the treatment of LC and COPD is provided. This review highlights the enormous relevance of these delivery systems as tools that are set to facilitate the clinical application of novel categories of therapeutics with poor pharmacokinetic properties.

Emerging applications and prospects of NFκB decoy oligodeoxynucleotides in managing respiratory diseases

Chronic respiratory diseases like asthma and Chronic Obstructive Pulmonary Disease (COPD) have been a burden to society for an extended period. Currently, there are only preventative treatments in the form of mono- or multiple-drug therapy available to patients who need to utilize it daily. Hence, throughout the years there has been a substantial amount of research in understanding what causes inflammation in the context of these diseases. For example, the transcription factor NFκB has a pivotal role in causing chronic inflammation. Subsequent research has been exploring ways to block the activation of NFκB as a potential therapeutic strategy for many inflammatory diseases. One of the possible ways through which this is probable is the utilisation of decoy oligodeoxynucleotides, which are synthetic, short, single-stranded DNA fragments that mimic the consensus binding site of a targeted transcription factor, thereby functionally inactivating it. However, limitations to the implementation of decoy oligodeoxynucleotides include their rapid degradation by intracellular nucleases and the lack of targeted tissue specificity. An advantageous approach to overcome these limitations involves using nanoparticles as a vessel for drug delivery. In this review, all of those key elements will be explored as to how they come together as an application to treat chronic inflammation in respiratory diseases.

Health risks for children exercising in an air-polluted environment can be reduced by monitoring air quality with low-cost particle sensors

A child's body is highly sensitive to air quality, especially regarding the concentration of particulate matter (PM). Nevertheless, due to the high cost of precision instruments, measurements of PM concentrations are rarely carried out in school areas where children spend most of their daily time. This paper presents the results of PM measurements made by a validated, low-cost university air pollution measurement system operating in a rural area near schools. An assessment of children's exposure to PM during school hours (8 a.m.-6 p.m.) at different times of the year was carried out. We show that PM10 concentrations in the air, particularly in winter, often exceeded the alert values of 50 µg m-3, posing a health risk to children, especially when children exercise outside the school building. We also calculated the rate and total PM10 deposition in the respiratory tract during various physical activities performed in clean and polluted air. Monitoring actual PM10 concentrations as presented in this paper, using a low cost sensors, offer school authorities and teachers an opportunity to reduce health risks for children. This can be achieved by adjusting the duration and exercise intensity of children's outdoor physical activities according to the measured air quality.

An experimental study on lung deposition of inhaled 2 μm particles in relation to lung characteristics and deposition models

BACKGROUND

The understanding of inhaled particle respiratory tract deposition is a key link to understand the health effects of particles or the efficiency for medical drug delivery via the lung. However, there are few experimental data on particle respiratory tract deposition, and the existing data deviates considerably when comparing results for particles > 1 μm.

METHODS

We designed an experimental set-up to measure deposition in the respiratory tract for particles > 1 μm, more specifically 2.3 μm, with careful consideration to minimise foreseen errors. We measured the deposition in seventeen healthy adults (21-68 years). The measurements were performed at tidal breathing, during three consecutive 5-minute periods while logging breathing patterns. Pulmonary function tests were performed, including the new airspace dimension assessment (AiDA) method measuring distal lung airspace radius (rAiDA). The lung characteristics and breathing variables were used in statistical models to investigate to what extent they can explain individual variations in measured deposited particle fraction. The measured particle deposition was compared to values predicted with whole lung models. Model calculations were made for each subject using measured variables as input (e.g., breathing pattern and functional residual capacity).

RESULTS

The measured fractional deposition for 2.3 μm particles was 0.60 ± 0.14, which is significantly higher than predicted by any of the models tested, ranging from 0.37 ± 0.08 to 0.53 ± 0.09. The multiple-path particle dosimetry (MPPD) model most closely predicted the measured deposition when using the new PNNL lung model. The individual variability in measured particle deposition was best explained by breathing pattern and distal airspace radius (rAiDA) at half inflation from AiDA. All models underestimated inter-subject variability even though the individual breathing pattern and functional residual capacity for each participant was used in the model.

CONCLUSIONS

Whole lung models need to be tuned and improved to predict the respiratory tract particle deposition of micron-sized particles, and to capture individual variations - a variation that is known to be higher for aged and diseased lungs. Further, the results support the hypothesis that the AiDA method measures dimensions in the peripheral lung and that rAiDA, as measured by the AiDA, can be used to better understand the individual variation in the dose to healthy and diseased lungs.

Label-Free Identification of Carbonaceous Particles Using Nonlinear Optical Microscopy

The adverse health effects of ambient carbonaceous particles (CPs) such as carbon black (CB), black carbon (BC), and brown carbon (BrC) are becoming more evident and depend on their composition and emission source. Therefore, identifying and quantifying these particles in biological samples are important to better understand their toxicity. Here, we report the development of a nonlinear optical approach for the identification of CPs such as CB and BrC using imaging conditions compatible with biomedical samples. The unique visible light fingerprint of CB and BrC nanoparticles (NPs) upon illumination with a femtosecond (fs) pulsed laser at 1300 nm excitation wavelength is an effective approach for their identification in their biological context. The emission from spectral features of these CPs was investigated with time-domain fluorescence lifetime imaging (FLIM) to further support their identification. This study is performed for different types of CPs embedded in agarose gel as well as in in vitro mammalian cells. The unique nonlinear emissive behavior of CP NPs used for their label-free identification is further complementary with fluorophores typically used for specific staining of biological samples thus providing the relevant bio-context.

Application of Inorganic Nanomaterials in Cultural Heritage Conservation, Risk of Toxicity, and Preventive Measures

Nanotechnology has allowed for significant progress in architectural, artistic, archaeological, or museum heritage conservation for repairing and preventing damages produced by deterioration agents (weathering, contaminants, or biological actions). This review analyzes the current treatments using nanomaterials, including consolidants, biocides, hydrophobic protectives, mechanical resistance improvers, flame-retardants, and multifunctional nanocomposites. Unfortunately, nanomaterials can affect human and animal health, altering the environment. Right now, it is a priority to stop to analyze its advantages and disadvantages. Therefore, the aims are to raise awareness about the nanotoxicity risks during handling and the subsequent environmental exposure to all those directly or indirectly involved in conservation processes. It reports the human-body interaction mechanisms and provides guidelines for preventing or controlling its toxicity, mentioning the current toxicity research of main compounds and emphasizing the need to provide more information about morphological, structural, and specific features that ultimately contribute to understanding their toxicity. It provides information about the current documents of international organizations (European Commission, NIOSH, OECD, Countries Normative) about worker protection, isolation, laboratory ventilation control, and debris management. Furthermore, it reports the qualitative risk assessment methods, management strategies, dose control, and focus/receptor relationship, besides the latest trends of using nanomaterials in masks and gas emissions control devices, discussing their risk of toxicity.

Assessing the in vitro toxicity of airborne (nano)particles to the human respiratory system: from basic to advanced models

Several studies have been conducted to address the potential adverse health risks attributed to exposure to nanoscale materials. While in vivo studies are fundamental for identifying the relationship between dose and occurrence of adverse effects, in vitro model systems provide important information regarding the mechanism(s) of action at the molecular level. With a special focus on exposure to inhaled (nano)particulate material toxicity assessment, this review provides an overview of the available human respiratory models and exposure systems for in vitro testing, advantages, limitations, and existing investigations using models of different complexity. A brief overview of the human respiratory system, pathway and fate of inhaled (nano)particles is also presented.

Characteristics of fine and ultrafine aerosols in the London underground

Underground railway systems are recognised spaces of increased personal pollution exposure. We studied the number-size distribution and physico-chemical characteristics of ultrafine (PM_0.1), fine (PM_0.1-2.5) and coarse (PM_2.5-10) particles collected on a London underground platform. Particle number concentrations gradually increased throughout the day, with a maximum concentration between 18:00 h and 21:00 h (local time). There was a maximum decrease in mass for the PM_2.5, PM_2.5-10 and black carbon of 3.9, 4.5 and ~ 21-times, respectively, between operable (OpHrs) and non-operable (N-OpHrs) hours. Average PM₁₀ (52 μg m^-3) and PM_2.5 (34 μg m^-3) concentrations over the full data showed levels above the World Health Organization Air Quality Guidelines. Respiratory deposition doses of particle number and mass concentrations were calculated and found to be two- and four-times higher during OpHrs compared with N-OpHrs, reflecting events such as train arrival/departure during OpHrs. Organic compounds were composed of aromatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) which are known to be harmful to health. Specific ratios of PAHs were identified for underground transport that may reflect an interaction between PAHs and fine particles. Scanning transmission electron microscopy (STEM) chemical maps of fine and ultrafine fractions show they are composed of Fe and O in the form of magnetite and nanosized mixtures of metals including Cr, Al, Ni and Mn. These findings, and the low air change rate (0.17 to 0.46 h^-1), highlight the need to improve the ventilation conditions.

Black carbon toxicity dependence on particle coating: Measurements with a novel cell exposure method

Black carbon (BC) is a component of ambient particulate matter which originates from incomplete combustion emissions. BC is regarded as an important short-lived climate forcer, and a significant public health hazard. These two concerns have made BC a focus in aerosol science. Even though, the toxicity of BC particles is well recognized, the mechanism of toxicity for BC as a part of the total gas and particle emission mixture from combustion is still largely unknown and studies concerning it are scarce. In the present study, using a novel thermophoresis-based air-liquid interface (ALI) in vitro exposure system, we studied the toxicity of combustion-generated aerosols containing high levels of BC, diluted to atmospheric levels (1 to 10 μg/m³). Applying multiple different aerosol treatments, we simulated different sources and atmospheric aging processes, and utilizing several toxicological endpoints, we thoroughly examined emission toxicity. Our results revealed that an organic coating on the BC particles increased the toxicity, which was seen as larger genotoxicity and immunosuppression. Furthermore, aging of the aerosol also increased its toxicity. A deeper statistical analysis of the results supported our initial conclusions and additionally revealed that toxicity increased with decreasing particle size. These findings regarding BC toxicity can be applied to support policies and technologies to reduce the most hazardous compositions of BC emissions. Additionally, our study showed that the thermophoretic ALI system is both a suitable and useful tool for toxicological studies of emission aerosols.

The physics of respiratory particle generation, fate in the air, and inhalation

Given that breathing is one of the most fundamental physiological functions, there is an urgent need to broaden our understanding of the fluid dynamics that governs it. There would be many benefits from doing so, including a better assessment of respiratory health, a basis for more precise delivery of pharmaceutical drugs for treatment, and the understanding and potential minimization of respiratory infection transmission. We review the physics of particle generation in the respiratory tract, the fate of these particles in the air on exhalation and the physics of particle inhalation. The main focus is on evidence from experimental studies. We conclude that although there is qualitative understanding of the generation of particles in the respiratory tract, a basic quantitative knowledge of the characteristics of the particles emitted during respiratory activities and their fate after emission, and a theoretical understanding of particle deposition during inhalation, nevertheless the general understanding of the entire process is rudimentary, and many open questions remain.

Evaluation of Work-Related Personal Exposure to Aerosol Particles

The effects of air pollution on the general public received much attention recently. Personal exposure and deposition fraction of aerosol particles were studied in Vilnius, Lithuania, focusing on individuals working in an office and driving to work. Aerosol monitoring in the urban background was found to give an indication of the minimum concentrations of particulate matter (PM) expected at urban roads, as these correspond to the lowest PM concentrations measured there. In March 2021, PM_2.5 concentrations at the urban background monitoring station reached values above the annual limit of 5 μg/m³ the World Health Organization in 50% of cases. Our study shows significant differences in exposure to air pollution in a car cabin and in a modern office. According to the multiple-path particle dosimetry model, the exposure of the person in the office is about 14 times lower than driving a car, where the minute deposition dose for PM₁ is 0.072 µg/min for the period when the PM_2.5 concentration in the urban background reaches 10 µg/m³. Compared to the PM_2.5 mass concentration at the urban background station, the mean PM_2.5 concentration in the vehicle reaches values that are 2–3 times higher. During the working day, when driving takes less than 10% of the time considered (commuting plus working), PM exposure during driving accounts for about 80% of the PM exposure caused by PM concentration in the office.

Airspace Dimension Assessment with Nanoparticles (AiDA) in Comparison to Established Pulmonary Function Tests

Background

Airspace Dimensions Assessment with nanoparticles (AiDA) is a new method for non-invasive measurement of pulmonary distal airspaces. The aim of this study was to compare AiDA measurements with other pulmonary function variables to better understand the potential of AiDA in a clinical context.

Methods

AiDA measurements and pulmonary function tests were performed in 695 subjects as part of the Swedish CArdioPulmonary bioImage Study. The measurement protocol included spirometry, measurement of diffusing capacity of carbon monoxide, oscillometry and pulmonary computed tomography. AiDA indices were compared to all other pulmonary examination measurements using multivariate statistical analysis.

Results

Our results show that AiDA measurements were significantly correlated with other pulmonary function examination indices, although covariance was low. We found that AiDA variables explained variance in the data that other lung function variables only influenced to a minor extent.

Conclusion

We conclude that the AiDA method provides information about the lung that is inaccessible with more conventional lung function techniques.

Cytotoxicity of 2D engineered nanomaterials in pulmonary and corneal epithelium

Two-dimensional (2D) engineered nanomaterials are widely used in consumer and industrial goods due to their unique chemical and physical characteristics. Engineered nanomaterials are incredibly small and capable of being aerosolized during manufacturing, with the potential for biological interaction at first-contact sites such as the eye and lung. The unique properties of 2D nanomaterials that make them of interest to many industries may also cause toxicity towards epithelial cells. Using murine and human respiratory epithelial cell culture models, we tested the cytotoxicity of eight 2D engineered nanomaterials: graphene (110 nm), graphene oxide (2 um), graphene oxide (400 nm), reduced graphene oxide (2 um), reduced graphene oxide (400 nm), partially reduced graphene oxide (400 nm), molybdenum disulfide (400 nm), and hexagonal boron nitride (150 nm). Non-graphene nanomaterials were also tested in human corneal epithelial cells for ocular epithelial cytotoxicity. Hexagonal boron nitride was found to be cytotoxic in mouse tracheal, human alveolar, and human corneal epithelial cells. Hexagonal boron nitride was also tested for inhibition of wound healing in alveolar epithelial cells; no inhibition was seen at sub-cytotoxic doses. Nanomaterials should be considered with care before use, due to specific regional cytotoxicity that also varies by cell type. Supported by U01ES027288 and T32HL007013 and T32ES007059.

Nanoparticle Delivery Platforms for RNAi Therapeutics Targeting COVID-19 Disease in the Respiratory Tract

Since December 2019, a pandemic of COVID-19 disease, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has rapidly spread across the globe. At present, the Food and Drug Administration (FDA) has issued emergency approval for the use of some antiviral drugs. However, these drugs still have limitations in the specific treatment of COVID-19, and as such, new treatment strategies urgently need to be developed. RNA-interference-based gene therapy provides a tractable target for antiviral treatment. Ensuring cell-specific targeted delivery is important to the success of gene therapy. The use of nanoparticles (NPs) as carriers for the delivery of small interfering RNA (siRNAs) to specific tissues or organs of the human body could play a crucial role in the specific therapy of severe respiratory infections, such as COVID-19. In this review, we describe a variety of novel nanocarriers, such as lipid NPs, star polymer NPs, and glycogen NPs, and summarize the pre-clinical/clinical progress of these nanoparticle platforms in siRNA delivery. We also discuss the application of various NP-capsulated siRNA as therapeutics for SARS-CoV-2 infection, the challenges with targeting these therapeutics to local delivery in the lung, and various inhalation devices used for therapeutic administration. We also discuss currently available animal models that are used for preclinical assessment of RNA-interference-based gene therapy. Advances in this field have the potential for antiviral treatments of COVID-19 disease and could be adapted to treat a range of respiratory diseases.

Electric charge of atmospheric nanoparticles and its potential implications with human health

This research presents a pilot project developed within the framework of the COST Action 15,211 in which atmospheric nanoparticles were measured in July 2018, in a maritime environment in the city of Santander in Northern Spain. ELPI® + (Electrical Low-Pressure Impactor) was used to measure nanoparticle properties (electric charge, number, size distribution and surface area) from 6 nm to 10,000 nm with 14 size channels. This study focused on the range between 6 and 380 nm. It considered atmospheric nanoparticle electric charge with surface area, deposited and number by size distribution at human respiratory tract regions in a standard person in Santander according to the human respiratory tract model of ICRP 94. An empirical distribution of nanoparticles deposited in the human respiratory tract model and its electric charge is presented for the city of Santander as the main output. Percentages of total and regional deposition in human respiratory tract model were calculated for the Atlantic climate. Nanoparticles have shown an alveolar surface area deposition plateau with a size distribution range between 6 nm to 150 nm. Negative charge of nanoparticles was clearly associated with primary atmospheric nanoparticles being mainly deposited in the alveolar region where a Brownian mechanism of deposition is predominant. We can demonstrate that electric charge may be a key element in explaining Brownian deposition of the smallest particles in the human respiratory tract and that it can be linked to theoretical positive and negative impacts on human health according to several biometeorological studies. To support our analysis, aerosol samples were characterized with transmission electron microscopy and Confocal Raman spectrometer to determinate morphology, size, chemical composition, and structure. The toxicological effects of the samples with the alveolar surface area had a greater deposition, remain to be studied.

Effect of Atmospheric Aging on Soot Particle Toxicity in Lung Cell Models at the Air–Liquid Interface: Differential Toxicological Impacts of Biogenic and Anthropogenic Secondary Organic Aerosols (SOAs)

Background:

Secondary organic aerosols (SOAs) formed from anthropogenic or biogenic gaseous precursors in the atmosphere substantially contribute to the ambient fine particulate matter [PM ≤2.5μm in aerodynamic diameter (PM2.5)] burden, which has been associated with adverse human health effects. However, there is only limited evidence on their differential toxicological impact.

Objectives:

We aimed to discriminate toxicological effects of aerosols generated by atmospheric aging on combustion soot particles (SPs) of gaseous biogenic (β-pinene) or anthropogenic (naphthalene) precursors in two different lung cell models exposed at the air–liquid interface (ALI).

Methods:

Mono- or cocultures of lung epithelial cells (A549) and endothelial cells (EA.hy926) were exposed at the ALI for 4 h to different aerosol concentrations of a photochemically aged mixture of primary combustion SP and β-pinene (SOAβPIN-SP) or naphthalene (SOANAP-SP). The internally mixed soot/SOA particles were comprehensively characterized in terms of their physical and chemical properties. We conducted toxicity tests to determine cytotoxicity, intracellular oxidative stress, primary and secondary genotoxicity, as well as inflammatory and angiogenic effects.

Results:

We observed considerable toxicity-related outcomes in cells treated with either SOA type. Greater adverse effects were measured for SOANAP-SP compared with SOAβPIN-SP in both cell models, whereas the nano-sized soot cores alone showed only minor effects. At the functional level, we found that SOANAP-SP augmented the secretion of malondialdehyde and interleukin-8 and may have induced the activation of endothelial cells in the coculture system. This activation was confirmed by comet assay, suggesting secondary genotoxicity and greater angiogenic potential. Chemical characterization of PM revealed distinct qualitative differences in the composition of the two secondary aerosol types.

Discussion:

In this study using A549 and EA.hy926 cells exposed at ALI, SOA compounds had greater toxicity than primary SPs. Photochemical aging of naphthalene was associated with the formation of more oxidized, more aromatic SOAs with a higher oxidative potential and toxicity compared with β-pinene. Thus, we conclude that the influence of atmospheric chemistry on the chemical PM composition plays a crucial role for the adverse health outcome of emissions. https://doi.org/10.1289/EHP9413

Effects of hygroscopic growth of ambient urban aerosol particles on their modelled regional and local deposition in healthy and COPD-compromised human respiratory system

Total, regional and local deposition fractions of urban-type aerosol particles with diameters of 50, 75, 110 and 145 nm were modelled and studied in their dry state and after their hygroscopic growth using a Stochastic Lung Model and a Computational Fluid and Particle Dynamics method. Healthy subjects and patients with severe chronic obstructive pulmonary disease (COPD) were considered. The hygroscopic growth factors (HGFs) adopted were determined experimentally and represent a real urban-type environment. The hygroscopic growth of particles resulted in decrease of the deposition fractions in all major parts of the healthy respiratory system and the extent of the deposited fractions was rising monotonically with particle size. In the extrathoracic (ET) region, the relative decrease was between 7% and 13%. In the lungs the deposition decreased by 11-16%. The decrease of deposition fraction due to hygroscopic growth was more accentuated in the conductive airways (up to 25%) and less pronounced towards the terminal airways. The spatial distribution of the deposited particles remained highly inhomogeneous with some areas containing thousands times more particles than the average number of particles per unit surface area. For COPD patients, the hygroscopic growth produced similar deposition alterations in the ET region than for healthy subjects. In the conductive airways, however, the particle growth caused a substantial relative decrease in the deposition fractions. In contrast, the relative depositions of hygroscopic particles increased in the acinar region.

Air Quality Outside Schools in Newcastle upon Tyne, UK: An Investigation into NO2 and PM Concentrations and PM Respiratory Deposition

Air pollution is the principal environmental threat to public health in the UK. Ever-increasing evidence links ambient air pollutants, preventable diseases, and health inequalities. Children are particularly vulnerable to harmful effects due to their short height, developing lungs, and higher rate of respiration. Using data from air quality monitors around schools, we investigated 2018–2019 ambient NO2, PM10, PM2.5, and PM1 concentrations at 12 schools in Newcastle upon Tyne, UK. We compared findings with EU/UK air quality regulations and guidelines, identified patterns, and calculated PM respiratory deposition doses (RDDs). The range of annual average (AA) concentrations across the schools for the two-year period was 23.7–39.2 µg/m3 for NO2, 7.4–22.2 µg/m3 for PM10, 3.5–11.6 µg/m3 for PM2.5, and 1.7–9.0 µg/m3 for PM1. The highest PM RDD children were exposed to at school was 30 µg/h. One school’s AA NO2, two schools’ hourly PM2.5 averages, and one school’s 24-h PM10 averages exceeded EU/UK regulations. All schools exceeded WHO2005 24-h PM10 and PM2.5 guidelines in 2018, less in 2019. All 12 schools would have exceeded WHO2021 NO2 AA guidelines (10 µg/m3), 2 the WHO2021 PM10 AA (15 µg/m3), and 10 the WHO2021 PM2.5 AA (5 µg/m3). Evidence-based policy is required to improve school ambient air quality and reduce children’s exposure.

Revisiting Airflow and Aerosol Transport Phenomena in the Deep Lungs with Microfluidics

The dynamics of respiratory airflows and the associated transport mechanisms of inhaled aerosols characteristic of the deep regions of the lungs are of broad interest in assessing both respiratory health risks and inhalation therapy outcomes. In the present review, we present a comprehensive discussion of our current understanding of airflow and aerosol transport phenomena that take place within the unique and complex anatomical environment of the deep lungs, characterized by submillimeter 3D alveolated airspaces and nominally slow resident airflows, known as low-Reynolds-number flows. We exemplify the advances brought forward by experimental efforts, in conjunction with numerical simulations, to revisit past mechanistic theories of respiratory airflow and particle transport in the distal acinar regions. Most significantly, we highlight how microfluidic-based platforms spanning the past decade have accelerated opportunities to deliver anatomically inspired in vitro solutions that capture with sufficient realism and accuracy the leading mechanisms governing both respiratory airflow and aerosol transport at true scale. Despite ongoing challenges and limitations with microfabrication techniques, the efforts witnessed in recent years have provided previously unattainable in vitro quantifications on the local transport properties in the deep pulmonary acinar airways. These may ultimately provide new opportunities to explore improved strategies of inhaled drug delivery to the deep acinar regions by investigating further the mechanistic interactions between airborne particulate carriers and respiratory airflows at the pulmonary microscales.

Lung-deposited dose of particulate matter from residential exposure to smoke from wood burning

Residential settings are of utmost importance for human exposure, as it is where people spend most of their time. Residential wood combustion is a widespread practice known as a source of indoor particulate matter (PM). Nevertheless, research on the risks of exposure associated with this source is scarce, and a better understanding of respiratory deposition of smoke particles is needed. The dosimetry model ExDoM2 was applied to determine the deposited dose of inhalable particulate matter (PM₁₀) from residential biomass combustion in the human respiratory tract (HRT) of adults and children. The dose was estimated using PM₁₀ exposure concentrations obtained from a field campaign carried out in two households during the operation of an open fireplace and a woodstove. Simultaneously, PM₁₀ levels were monitored outside to investigate the outdoor dose in a rural area strongly impacted by biomass burning emissions. Indoors, the 8-h average PM₁₀ concentrations ranged from 88.3 to 489 μg m^-3 and from 69.4 to 122 μg m^-3 for the operation of the fireplace and the woodstove, respectively, while outdoor average PM₁₀ concentrations ranged from 17.3 to 94.2 μg m^-3. The highest amount of the deposited particles was recorded in the extrathoracic region (68-79%), whereas the deposition was much lower in the tracheobronchial tree (5-6%) and alveolar-interstitial region (16-21%). The total dose received while using the fireplace was more than twofold the one received in the room with a woodstove and more than 10 times higher than in the absence of the source. Overall, indoor doses were higher than the ones received by a subject exposed outdoors, especially at the alveolar-interstitial region. After 24 h of exposure, it was estimated that approximately 35 to 37% of the particles deposited in the HRT were transferred to the gastrointestinal tract, while approximately 2.0-2.5% were absorbed into the blood. The results from exposure and dose of indoor particles gathered in this work suggest that homeowners should be encouraged to upgrade the wood burning technology to reduce the PM levels inside their residences. This study also provides biologically relevant results on the lung deposition of particles from residential biomass burning that can be used as a reference for future research.

On the spread of ultrafine particulate matter: A mathematical model for motor vehicle emissions and their effects as an asthma trigger

Asthma is a respiratory disease that affects the lungs, with a prevalence of 339.4 million people worldwide [G. Marks, N. Pearce, D. Strachan, I. Asher and P. Ellwood, The Global Asthma Report 2018, globalasthmareport.org (2018)]. Many factors contribute to the high prevalence of asthma, but with the rise of the industrial age, air pollutants have become one of the main Ultrafine particles (UFPs), which are a type of air pollutant that can affect asthmatics the most. These UFPs originate primarily from the combustion of motor vehicles [P. Solomon, Ultrafine particles in ambient air. EM: Air and Waste Management Association’s Magazine for Environmental Managers (2012)] and although in certain places some regulations to control their emission have been implemented they might not be enough. In this work, a mathematical model of reaction–diffusion type is constructed to study how UFPs grow and disperse in the environment and in turn how they affect an asthmatic population. Part of our focus is on the existence of traveling wave solutions and their minimum asymptotic speed of pollutant propagation [Formula: see text]. Through the analysis of the model it was possible to identify the necessary threshold conditions to control the pollutant emissions and consequently reduce the asthma episodes in the population. Analytical and numerical results from this work prove how harmful the UFEs are for the asthmatic population and how they can exacerbate their asthma episodes.

Bioinspired particle engineering for non-invasive inhaled drug delivery to the lungs

Pulmonary drug delivery is governed by several biophysical parameters of delivery carriers, such as particle size, shape, density, charge, and surface modifications. Although much attention has been given to other parameters, particle shape effects have rarely been explored. In this work, we assess the influence of particle shape of inhaled delivery carriers on their aerodynamic properties and macrophage uptake by using polymeric microparticles of different geometries ranging in various sizes. Doxorubicin was conjugated to the polymer particles and the bioconjugates were characterized. Interestingly, the results of in-vitro lung deposition, performed using a next generation impactor, demonstrated a significant improvement in the aerodynamic properties of the rod-shaped particles with a high aspect ratio as compared to spherical particles with the same equivalent volume. The results of a macrophage uptake experiment demonstrate that the high aspect ratio particles were phagocytosed less than spherical particles. Furthermore, the cytotoxicity of these doxorubicin-conjugated particles was determined against murine macrophages, resulting in reduced toxicity when treated with high aspect ratio particles as compared to spherical particles. This project provides valuable insights into the influence of particle shape on aerodynamic properties and primary defense mechanisms in the peripheral lungs, while using polymeric microparticles of various sizes and geometries. Further systematic development can help translate these findings to preclinical and clinical studies for designing efficient inhalable delivery carriers.

Inhaled antibiotic-loaded polymeric nanoparticles for the management of lower respiratory tract infections

Lower respiratory tract infections (LRTIs) are one of the leading causes of deaths in the world. Currently available treatment for this disease is with high doses of antibiotics which need to be administered frequently. Instead, pulmonary delivery of drugs has been considered as one of the most efficient routes of drug delivery to the targeted areas as it provides rapid onset of action, direct deposition of drugs into the lungs, and better therapeutic effects at low doses and is self-administrable by the patients. Thus, there is a need for scientists to design more convenient pulmonary drug delivery systems towards the innovation of a novel treatment system for LRTIs. Drug-encapsulating polymer nanoparticles have been investigated for lung delivery which could significantly reduce the limitations of the currently available treatment system for LRTIs. However, the selection of an appropriate polymer carrier for the drugs is a critical issue for the successful formulations of inhalable nanoparticles. In this review, the current understanding of LRTIs, management systems for this disease and their limitations, pulmonary drug delivery systems and the challenges of drug delivery through the pulmonary route are discussed. Drug-encapsulating polymer nanoparticles for lung delivery, antibiotics used in pulmonary delivery and drug encapsulation techniques have also been reviewed. A strong emphasis is placed on the impact of drug delivery into the infected lungs.

Air Pollution Neurotoxicity in the Adult Brain: Emerging Concepts from Experimental Findings

Epidemiological studies are associating elevated exposure to air pollution with increased risk of Alzheimer's disease and other neurodegenerative disorders. In effect, air pollution accelerates many aging conditions that promote cognitive declines of aging. The underlying mechanisms and scale of effects remain largely unknown due to its chemical and physical complexity. Moreover, individual responses to air pollution are shaped by an intricate interface of pollutant mixture with the biological features of the exposed individual such as age, sex, genetic background, underlying diseases, and nutrition, but also other environmental factors including exposure to cigarette smoke. Resolving this complex manifold requires more detailed environmental and lifestyle data on diverse populations, and a systematic experimental approach. Our review aims to summarize the modest existing literature on experimental studies on air pollution neurotoxicity for adult rodents and identify key gaps and emerging challenges as we go forward. It is timely for experimental biologists to critically understand prior findings and develop innovative approaches to this urgent global problem. We hope to increase recognition of the importance of air pollution on brain aging by our colleagues in the neurosciences and in biomedical gerontology, and to support the immediate translation of the findings into public health guidelines for the regulation of remedial environmental factors that accelerate aging processes.

Ecotoxicology of Heavy Metal(loid)-Enriched Particulate Matter: Foliar Accumulation by Plants and Health Impacts

Atmospheric contamination by heavy metal-enriched particulate matter (metal-PM) is highly topical nowadays because of its high persistence and toxic nature. Metal-PMs are emitted to the atmosphere by various natural and anthropogenic activities, the latter being the major source. After being released into the atmosphere, metal-PM can travel over a long distance and can deposit on the buildings, water, soil, and plant canopy. In this way, these metal-PMs can contaminate different parts of the ecosystem. In addition, metal-PMs can be directly inhaled by humans and induce several health effects. Therefore, it is of great importance to understand the fate and behavior of these metal-PMs in the environment. In this review, we highlighted the atmospheric contamination by metal-PMs, possible sources, speciation, transport over a long distance, and deposition on soil, plants, and buildings. This review also describes the foliar deposition and uptake of metal-PMs by plants. Moreover, the inhalation of these metal-PMs by humans and the associated health risks have been critically discussed. Finally, the article proposed some key management strategies and future perspectives along with the summary of the entire review. The abovementioned facts about the biogeochemical behavior of metal-PMs in the ecosystem have been supported with well-summarized tables (total 14) and figures (4), which make this review article highly informative and useful for researchers, scientists, students, policymakers, and the organizations involved in development and management. It is proposed that management strategies should be developed and adapted to cope with atmospheric release and contamination of metal-PM.

Current understanding of nanoparticle toxicity mechanisms and interactions with biological systems

Nanotechnology is an emerging science involving the manipulation of matter on the nanometer scale.

A review on chitosan and its development as pulmonary particulate anti-infective and anti-cancer drug carriers

Chitosan, as a biodegradable and biocompatible polymer, is characterized by anti-microbial and anti-cancer properties. It lately has received a widespread interest for use as the pulmonary particulate backbone materials of drug carrier for the treatment of infectious disease and cancer. The success of chitosan as pulmonary particulate drug carrier is a critical interplay of their mucoadhesive, permeation enhancement and site/cell-specific attributes. In the case of nanocarriers, various microencapsulation and micro-nano blending systems have been devised to equip them with an appropriate aerodynamic character to enable efficient pulmonary aerosolization and inhalation. The late COVID-19 infection is met with acute respiratory distress syndrome and cancer. Chitosan and its derivatives are found useful in combating HCoV and cancer as a function of their molecular weight, substituent type and its degree of substitution. The interest in chitosan is expected to rise in the next decade from the perspectives of drug delivery in combination with its therapeutic performance.

Experimentally determined deposition of ambient urban ultrafine particles in the respiratory tract of children

A critical element of the risk assessment of exposure to airborne ambient ultrafine particles (UFP) is the quantification of respiratory tract deposition (RTD) of the particles, which is intrinsically challenging, particularly at the population scale. In this study, we used a recently proposed method to experimentally determine the RTD of urban UFP in a large group of children exposed to these particles in a school setting in Brisbane, Australia. Children are one of the most susceptible population groups; However, little is known about the deposition of UFP from urban traffic in their airways. In order to advance the knowledge in this field, the objectives of this study were: to determine the deposition of ambient urbane UFP in large number children, to catergorize the source of inhaled UFPs and hence to assess the contribution of air pollution sources to the deposition. RTD was measured in children aged 8-11 at primary schools using a flow-through chamber bag system. First, the inhaled and exhaled air was separated; then the particle number size distribution and particle number concentration were measured. The sources of inhaled UFP were categorized according to their particle number size distribution by a K means cluster technique. A total of 128 children from five schools performed the RTD measurement. The mean total deposition fraction of urban UFP in all children was 0.59 ± 0.10. Inhaled UFP were categorized into two groups: traffic and urban background, with the GMD of corresponding particle number size distribution of 20 nm and 40 nm, respectively. The total deposition fraction (mean ± SD) of UFP from these two groups was 0.68 ± 0.09 for traffic and 0.55 ± 0.08 for urban background respectively. This is the first study in which RTD was measured in a large group of children inhaling real urban UFP. First, we proved that this novel method can indeed be applied easily and quickly to a large group of people. Second, we quantified the RTD of children, thus providing an important input to the risk assessment for exposure to UFP.

Experimentally determined deposition of ambient urban ultrafine particles in the respiratory tract of children

A critical element of the risk assessment of exposure to airborne ambient ultrafine particles (UFP) is the quantification of respiratory tract deposition (RTD) of the particles, which is intrinsically challenging, particularly at the population scale. In this study, we used a recently proposed method to experimentally determine the RTD of urban UFP in a large group of children exposed to these particles in a school setting in Brisbane, Australia. Children are one of the most susceptible population groups; However, little is known about the deposition of UFP from urban traffic in their airways. In order to advance the knowledge in this field, the objectives of this study were: to determine the deposition of ambient urbane UFP in large number children, to catergorize the source of inhaled UFPs and hence to assess the contribution of air pollution sources to the deposition. RTD was measured in children aged 8-11 at primary schools using a flow-through chamber bag system. First, the inhaled and exhaled air was separated; then the particle number size distribution and particle number concentration were measured. The sources of inhaled UFP were categorized according to their particle number size distribution by a K means cluster technique. A total of 128 children from five schools performed the RTD measurement. The mean total deposition fraction of urban UFP in all children was 0.59 ± 0.10. Inhaled UFP were categorized into two groups: traffic and urban background, with the GMD of corresponding particle number size distribution of 20 nm and 40 nm, respectively. The total deposition fraction (mean ± SD) of UFP from these two groups was 0.68 ± 0.09 for traffic and 0.55 ± 0.08 for urban background respectively. This is the first study in which RTD was measured in a large group of children inhaling real urban UFP. First, we proved that this novel method can indeed be applied easily and quickly to a large group of people. Second, we quantified the RTD of children, thus providing an important input to the risk assessment for exposure to UFP.

Targeting neutrophils using novel drug delivery systems in chronic respiratory diseases

Neutrophils are essential effector cells of immune system for clearing the extracellular pathogens during inflammation and immune reactions. Neutrophils play a major role in chronic respiratory diseases. In respiratory diseases such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, lung cancer and others, there occurs extreme infiltration and activation of neutrophils followed by a cascade of events like oxidative stress and dysregulated cellular proteins that eventually result in apoptosis and tissue damage. Dysregulation of neutrophil effector functions including delayed neutropil apoptosis, increased neutrophil extracellular traps in the pathogenesis of asthma, and chronic obstructive pulmonary disease enable neutrophils as a potential therapeutic target. Accounting to their role in pathogenesis, neutrophils present as an excellent therapeutic target for the treatment of chronic respiratory diseases. This review highlights the current status and the emerging trends in novel drug delivery systems such as nanoparticles, liposomes, microspheres, and other newer nanosystems that can target neutrophils and their molecular pathways, in the airways against infections, inflammation, and cancer. These drug delivery systems are promising in providing sustained drug delivery, reduced therapeutic dose, improved patient compliance, and reduced drug toxicity. In addition, the review also discusses emerging strategies and the future perspectives in neutrophil-based therapy.

Investigations of the Influences of Processing Conditions on the Properties of Spray Dried Chitosan-Tripolyphosphate Particles loaded with Theophylline

The preparation of chitosan-tripolyphosphate (chitosan-TPP) particles by the spray drying had been reported word widely for a sustained release of drugs to prevent rapid drug metabolism. Although the spray drying is a straightforward procedure turning a liquid feed into a well-defined dry powder, seldom research works were focusing on how the processing parameters and liquid feeding constitutions of spray drying system might affect the properties of spray-dried chitosan particles loaded with drugs, such as the particle size and morphologies, which would be very important to drug encapsulation and dissolution of the drug delivery design. This study thus prepared the chitosan particles with theophylline (TH) loaded as a model drug and TPP as cross-linker at various spray drying conditions. Our results indicate the diameter of the TH/chitosan-TPP particles made by customized spray drying apparatus spans from 424 to 497 nm with a geometric standard deviation of less than 2. The corresponding release of TH was tunable by the chitosan-TPP matrix density under the selected spray drying temperature and the carrying air flow rate. These results suggest an indeed need for optimized spray drying processing conditions to make the ideal spray-dried TH/chitosan-TPP particles for the desired drug delivery.

Quality control and testing evaluation of pharmaceutical aerosols

Drug delivery to the respiratory tract locally has become an increasingly effective and important therapeutic method for treating a variety of pulmonary disorders, including chronic abstractive disease, asthma, bronchitis, pneumonia, and cystic fibrosis. Increase in prevalence respiratory disorders is a major factor driving the growth of global respiratory inhaler devices market. The effectiveness of pharmaceutical aerosols therapeutic performance is affected by various factors such as type and characteristics of propellants, whose properties are vapor pressure of propellants, viscosity and density flash point and also other factors such as type and characteristics of active ingredients, containers, valves, and actuators, along with percentage of moisture content and mechanism of emitted dose deposition, spray pattern, efficiency of valve crimping, and measurement of particle size aerosols. The purpose of this book chapter is to discuss the in-process and finished product quality control tests for pharmaceutical aerosols based on pharmacopeia standards and specifications.

The role of SP-B1–25 peptides in lung surfactant monolayers exposed to gold nanoparticles

Lung surfactant monolayer’s (acts as the first line barrier for inhaled nanoparticles) components (lipids and peptides) rearrange themselves by the influence of exposed gold nanoparticles at various stages of the breathing cycle.

Ultrafine particles and children's health: Literature review

The aim of this study was to review and synthesize the existing knowledge of the effects of ultrafine particles [UFPs] with a specific focus on children's health. An extensive literature search identified 16 studies fulfilling the criteria set for the review. One of the most important findings of the review was that, in general, there is an association between children's health and exposure to UFPs, especially among children with respiratory diseases, who commonly experience alterations in inflammatory biomarkers and deterioration in lung function as a result of UFP exposure. Notably, the health effects of UFPs are related to their ability to penetrate through different systems of the body due to their small size.

Characteristics of school children's personal exposure to ultrafine particles in Heshan, Pearl River Delta, China - A pilot study

BACKGROUND

There is a significant lack of scientific knowledge on population exposure to ultrafine particles (UFP) in China to date. This paper quantifies and characterises school children's personal UFP exposure and exposure intensity against their indoor and outdoor activities during a school day (home, school and commuting) in the city of Heshan within the Pearl River Delta (PRD) region, southern China.

METHODS

Time-series of UFP number concentrations and average size were measured over 24 h for 24 children (9-13 years old), using personal monitors over two weeks in April 2016. Time-activity diaries and a questionnaire on the general home environment and potential sources of particles at home were also collected for each participating child. The analysis included concurrently measured size distributions of ambient UFP at a nearby fixed reference site (Heshan Supersite).

RESULTS

Hourly average UFP concentrations exhibited three peaks in the morning, midday and evening. Time spent indoors at home was found to have the highest average exposure (1.26 × 10⁴ cm^-3 during sleeping) and exposure intensity (2.41). While there is always infiltration of outdoor particles indoors (from nearby traffic and general urban background sources), indoor exposure at home was significantly higher than outdoor exposure. Based on the collected questionnaire data, this was considered to be driven predominantly by adults smoking and the use of mosquito repellent incense during the night. Outdoor activities at school were associated with the lowest average exposure (6.87 × 10² cm^-3) and exposure intensity (0.52).

CONCLUSION

Despite the small sample size, this study characterised, for the first time, children's personal UFP exposure in a city downwind of major pollution sources of the PRD region in China. Particularly, the results highlighted the impact of smoking at home on children's exposure. While the study could not apportion the specific contributions of second hand-smoking and mosquito coil burning, considering the prevalence of smokers among the parents who smoke at home, smoking is a very significant factor. Exposure to second-hand smoke is avoidable, and these findings point out to the crucial role of government authorities and public health educators in engaging with the community on the role of air quality on health, and the severity of the impact of second-hand smoke on children's health.

The thermostated medical jet nebulizer: Aerosol characteristics

The sudden expansion of gas at the outlet of the jet (pneumatic) nebulizer significantly reduces the temperature of the solution, which may provoke bronchospasm, therefore it is recommended to use modern pneumatic inhalers equipped with a thermostat or a universal thermal attachment that allow to obtain a higher temperature aerosol, i.e. thermo-aerosol. The research was carried out for model Newtonian fluids. The droplet diameters of the aerosol spray were investigated using a Spraytec aerosol particle size measurement system. Analysis of the obtained results showed that the increase in solution viscosity caused a decrease in mean droplet diameters and prolonged nebulization time. The analysis of experimental data made it possible to propose a correlation equation describing the mean diameter of the droplets depending on the properties of the liquid and the flow conditions in the thermostated medical nebulizer. The obtained data contributes to a better understanding of the complex liquid atomisation process and can be helpful in the design of medical nebulizers and pharmaceutical preparations.

Inhalation Exposure Analysis of Lung-Inhalable Particles in an Approximate Rat Central Airway

Rats have been widely used as surrogates for evaluating the adverse health effects of inhaled airborne particulate matter. This paper presents a computational fluid and particle dynamics (CFPD) study of particle transport and deposition in an approximate rat central airway model. The geometric model was constructed based on magnetic resonance (MR) imaging data sourced from previous study. Lung-inhalable particles covering a diameter range from 20 nm to 1.0 µm were passively released into the trachea, and the Lagrangian particle tracking approach was used to predict individual particle trajectories. Overall, regional and local deposition patterns in the central airway were analyzed in detail. A preliminary interspecies data comparison was made between present rat models and previously published human data. Results showed deposition “hot spots” were mainly concentrated at airway bifurcation apexes, and a gravitational effect should also be considered for inertia particles when using a rat as a laboratory animal. While for humans, this may not happen as the standing posture is completely different. Lastly, the preliminary interspecies data comparison confirms the deposition similarity in terms of deposition enhancement factors, which is a weighted deposition concentration parameter. This interspecies comparison confirms feasibility of extrapolating surrogate rat deposition data to humans using existing data extrapolation approach, which mostly relies on bulk anatomical differences as dose adjustment factors.

Ultrafine particle deposition in a realistic human airway at multiple inhalation scenarios

The scarcity of regional deposition data in distal respiratory airways represents an important challenge for current toxicology and pharmacology research. To bridge this gap, a realistic airway model extending from nasal and oral openings to distal bronchial airways with varying pathway length was built in this study. Transport and deposition characteristics of naturally inhaled ultrafine particles (UFPs) ranging from 1 to 100 nm were numerically investigated, and effects of different inhalation scenarios were considered. To enable intercase particle deposition comparison, an adjusted parameter, unified deposition enhancement factor (UDEF), was proposed for quantifying the localised deposition concentration. Results show that compartment particle deposition peaked around the ultrafine end of the considered size range, and it dropped rapidly with the increase of particle size. Different inhalation modes caused notable deposition changes in the extrathoracic region, while its effects in the TB airway are much less. For UFPs larger than 10 nm, predicted deposition efficiencies in all compartments are all at lowest levels among considered particle size range, implying UFPs ranging from 10 to 100 nm can travel through the whole respiratory airway model and escape to the alveolar region. Furthermore, high enhancement factors were observed at the vicinity of most bifurcation apexes, and more even UDEF distribution was observed from 1-nm particle cases. While for 100-nm cases, the deposited particles tend to concentrate at few "hot spots" (areas of high deposition concentration in relation to surrounding surfaces) with greater UDEF in the tracheobronchial airway.

Changes of particle deposition caused by different breathing patterns during active lung simulation

Aerosols are an integral part of everyday life and as such are inhaled under various conditions and circumstances. These may vary based on the health and activity status of an individual. The aim of this work is to analyse the particle deposition mechanisms during the simulation of three different breathing patterns using an aerosol representing the PM1 fraction of fine particles. The active electro-mechanical lung simulator xPULM is utilized as a driving force and is combined with a non-invasive direct reading optical aerosol measurement system. Results show differences between the number of deposited particles for the three breathing patterns and for the three typical size ranges of airborne particles. Overall, the presented approach demonstrates the possibility of determining the changes of aerosol uptake based on different breathing patterns using the electro-mechanical lung simulator and laboratory produced aerosols. Further measurement cycles must be performed in order to validate the found interactions and to characterize the major influencing parameters.

A new method to measure real-world respiratory tract deposition of inhaled ambient black carbon

In this study, we present the development of a mobile system to measure real-world total respiratory tract deposition of inhaled ambient black carbon (BC). Such information can be used to supplement the existing knowledge on air pollution-related health effects, especially in the regions where the use of standard methods and intricate instrumentation is limited. The study is divided in two parts. Firstly, we present the design of portable system and methodology to evaluate the exhaled air BC content. We demonstrate that under real-world conditions, the proposed system exhibit negligible particle losses, and can additionally be used to determine the minute ventilation. Secondly, exemplary experimental data from the system is presented. A feasibility study was conducted in the city of La Paz, Bolivia. In a pilot experiment, we found that the cumulative total respiratory tract deposition dose over 1-h commuting trip would result in approximately 2.6 μg of BC. This is up to 5 times lower than the values obtained from conjectural approach (e.g. using physical parameters from previously reported worksheets). Measured total respiratory tract deposited BC fraction varied from 39% to 48% during walking and commuting inside a micro-bus, respectively. To the best of our knowledge, no studies focusing on experimental determination of real-world deposition dose of BC have been performed in developing regions. This can be especially important because the BC mass concentration is significant and determines a large fraction of particle mass concentration. In this work, we propose a potential method, recommendations, as well as the limitations in establishing an easy and relatively cheap way to estimate the respiratory tract deposition of BC.

Charting the human respiratory tract with airborne nanoparticles: evaluation of the Airspace Dimension Assessment technique

Airspace Dimension Assessment (AiDA) is a technique to assess lung morphology by measuring lung deposition of inhaled nanoparticles. Nanoparticles deposit in the lungs predominately by diffusion, and average diffusion distances, corresponding to effective airspace radii ( rAiDA), can be inferred from measurements of particle recovery after varied breath holds. Also, particle recovery after a 0-s breath hold ( R0) may hold information about the small conducting airways. This study investigates rAiDA at different volumetric sample depths in the lungs of healthy subjects. Measurements were performed with 50-nm polystyrene nanospheres on 19 healthy subjects aged 17–67 yr. Volumetric sample depths ranged from 200 to 5,000 ml and breath-hold times from 5 to 20 s. At the examined volumetric sample depths, rAiDA values ranged from ~200–600 μm, which correspond to dimensions of the bronchiolar and the gas-exchanging regions of the lungs. R0 decreased with volumetric sample depth and showed more intersubject variation than rAiDA. Correlations were found between the AiDA parameters, anthropometry, and lung function tests, but not between rAiDA and R0. For repeated measurements on 3 subjects over an 18-mo period, rAiDA varied on average within ± 7 μm (± 2.4%). The results indicate that AiDA has potential as an efficient new in vivo technique to assess individual lung properties. The information obtained by such measurements may be of value for lung diagnostics, especially for the distal lungs, which are challenging to examine directly by other means.

NEW & NOTEWORTHY This is the first study to measure effective airspace radii ( rAiDA) at volumetric sample depths 200–5,000 ml in healthy subjects by Airspace Dimension Assessment (AiDA). Observed rAiDA were 200–600 μm, which corresponds to airspaces for the bronchiolar and the gas-exchanging regions around airway generation 14–17. rAiDA correlated with lung function tests and anthropometry. Measurements of rAiDA on 3 subjects over 11–18 mo were within ± 7 μm.

Nanoparticles in Daily Life: Applications, Toxicity and Regulations

At nanoscale, man-made materials may show unique properties that differ from bulk and dissolved counterparts. The unique properties of engineered nanomaterials not only impart critical advantages but also confer toxicity because of their unwanted interactions with different biological compartments and cellular processes. In this review, we discuss various entry routes of nanomaterials in the human body, their applications in daily life, and the mechanisms underlying their toxicity. We further explore the passage of nanomaterials into air, water, and soil ecosystems, resulting in diverse environmental impacts. Briefly, we probe the available strategies for risk assessment and risk management to assist in reducing the occupational risks of potentially hazardous engineered nanomaterials including the control banding (CB) approach. Moreover, we substantiate the need for uniform guidelines for systematic analysis of nanomaterial toxicity, in silico toxicological investigations, and obligation to ensure the safe disposal of nanowaste to reduce or eliminate untoward environmental and health impacts. At the end, we scrutinize global regulatory trends, hurdles, and efforts to develop better regulatory sciences in the field of nanomedicines.

Altered deposition of inhaled nanoparticles in subjects with chronic obstructive pulmonary disease

Background

Respiratory tract deposition of airborne particles is a key link to understand their health impact. Experimental data are limited for vulnerable groups such as individuals with respiratory diseases. The aim of this study is to investigate the differences in lung deposition of nanoparticles in the distal lung for healthy subjects and subjects with respiratory disease.

Methods

Lung deposition of nanoparticles (50 and 100 nm) was measured after a 10 s breath-hold for three groups: healthy never-smoking subjects (n = 17), asymptomatic (active and former) smokers (n = 15) and subjects with chronic obstructive pulmonary disease (n = 16). Measurements were made at 1300 mL and 1800 mL volumetric lung depth. Each subject also underwent conventional lung function tests, including post bronchodilator FEV₁, VC, and diffusing capacity for carbon monoxide, D_L,CO. Patients with previously diagnosed respiratory disease underwent a CT-scan of the lungs. Particle lung deposition fraction, was compared between the groups and with conventional lung function tests.

Results

We found that the deposition fraction was significantly lower for subjects with emphysema compared to the other subjects (p = 0.001–0.01), but no significant differences were found between healthy never-smokers and smokers. Furthermore, the particle deposition correlated with pulmonary function tests, FEV_1%Pred (p < 0.05), FEV₁/VC_%Pred (p < 0.01) and D_L,CO (p < 0.0005) when all subjects were included. Furthermore, for subjects with emphysema, deposition fraction correlated strongly with D_L,CO (Pearson’s r = 0.80–0.85, p < 0.002) while this correlation was not found within the other groups.

Conclusions

Lower deposition fraction was observed for emphysematous subjects and this can be explained by enlarged distal airspaces in the lungs. As expected, deposition increases for smaller particles and deeper inhalation. The observed results have implications for exposure assessment of air pollution and dosimetry of aerosol-based drug delivery of nanoparticles.

Deposition of inhaled nanoparticles is reduced in subjects with COPD and correlates with the extent of emphysema: proof of concept for a novel diagnostic technique

BACKGROUND

The diagnosis of chronic obstructive pulmonary disease (COPD) is often based on spirometry, which is not sensitive to early emphysema. We have recently described a method for assessing distal airspace dimensions by measuring recovery of nanoparticles in exhaled air after a single-breath inhalation followed by breath-hold. Recovery refers to the non-deposited particle fraction. The aim of this study was to explore differences in the recovery of exhaled nanoparticles in subjects with COPD and never-smoking controls. A secondary aim was to determine whether recovery correlates with the extent of emphysema.

METHOD

A total of 19 patients with COPD and 19 controls underwent three repeats of single-breath nanoparticle inhalation followed by breath-hold. Particle concentrations in the inhaled aerosol, and in an alveolar sample exhaled after breath-hold, were measured to obtain recovery.

FINDINGS

The patients with COPD had a significantly higher mean recovery than controls, 0·128 ± 0·063 versus 0·074 ± 0·058; P = 0·010. Also, recovery correlated significantly with computed tomography (CT) densitometry variables (P<0·01) and diffusing capacity for carbon monoxide (DL,CO ; P = 0·002).

INTERPRETATION

Higher recovery for emphysema patients, relative to controls, is explained by larger diffusion distances in enlarged distal airspaces. The nanoparticle inhalation method shows potential to be developed towards a tool to diagnose emphysema.

Carbon Nanotubes and Other Engineered Nanoparticles Induced Pathophysiology on Mesothelial Cells and Mesothelial Membranes

Nanoparticles have great potential for numerous applications due to their unique physicochemical properties. However, concerns have been raised that they may induce deleterious effects on biological systems. There is accumulating evidence that, like asbestos, inhaled nanomaterials of >5 μm and high aspect ratio (3:1), particularly rod-like carbon nanotubes, may inflict pleural disease including mesothelioma. Additionally, a recent set of case reports suggests that inhalation of polyacrylate/nanosilica could in part be associated with inflammation and fibrosis of the pleura of factory workers. However, the adverse outcomes of nanoparticle exposure to mesothelial tissues are still largely unexplored. In that context, the present review aims to provide an overview of the relevant pathophysiological implications involving toxicological studies describing effects of engineered nanoparticles on mesothelial cells and membranes. In vitro studies primarily emphasize on simulating cellular uptake and toxicity of nanotubes on benign or malignant cell lines. On the other hand, in vivo studies focus on illustrating endpoints of serosal pathology in rodent animal models. From a molecular aspect, some nanoparticle categories are shown to be cytotoxic and genotoxic after acute treatment, whereas chronic incubation may lead to malignant-like transformation. At an organism level, a number of fibrous shaped nanotubes are related with features of chronic inflammation and MWCNT-7 is the only type to consistently inflict mesothelioma.

Novel techniques for detection and characterization of nanomaterials based on aerosol science supporting environmental applications

The number of people exposed to nanoparticles is growing accordingly to the production and development of new nanomaterials. Moreover, this increase is expected to continue in the future. However, there is a lack of standardized sampling and metric methods to measure the level of exposure to nanoparticles, and the information related to possible adverse health effects is scarce. Aerosol technology has been detecting and characterizing nanoparticles for decades and some of their developments can be of use in nanotechnology characterization. We present here two current developments based on used principles in aerosol science, which can widen its application to the characterization of nanomaterials. On the one hand, a sample preparation technique for nanoparticle analysis by electron microscopy based on electrospray atomization technology. Several samples prepared in this way have been analysed and compared to more traditional sample preparation strategies like the "drop on grid" method. It was found that the particles deposited by electrospray generally show a much more homogeneous spatial distribution on the substrate and the number of single particles increases substantially. On the other hand, it is presented an electrical mobility classification system, DMA, with enormous possibilities for the quick and economic size characterization of suspensions of nanoparticles, thanks to its injection system by electrospray and to its high resolution in the lower range of the nanoscale. The first assessment of the abovementioned devices highlights its potential applications in exposure assessment and nanotechnological contexts.