Airborne Nanoparticles Research Articles

Study of the neurotoxicity of indoor airborne nanoparticles based on a 3D human blood-brain barrier chip

BackgroundThere is growing public awareness regarding the health effects of indoor nanoscale particulate matter (INPM) since people spend the majority of their time indoors. INPM could have a direct entry route into the brain via the axons of the olfactory nerve and migrating across the blood-brain barrier (BBB). Using animals to explore this possibility is not a reliable method to fully demonstrate human physiological responses. We, therefore, set out to develop a human 3D functional blood-brain barrier model to examine the potential effects of INPM on the cerebral nervous system. MethodsHuman astrocytes were co-cultured and human umbilical vein endothelial cells in 3D within a microfluidic chip to simulate the micro-complex physiological structure of the human BBB. This 3D human organotypic model has then been made to investigate any INPM-induced BBB dysfunction linked to potential cellular responses. ResultsA 3D human functional blood-brain barrier was constructed in this study. We observed the translocation of INPM across the blood-brain barrier. The 3D human organotypic chip initially reflected damage to the nervous system with abnormal astrocyte proliferation and a decline in cell viability. We also looked at the behavior of oxidative stress-related biomarkers (ROS, GSH-Px, and MDA). INPM was implicated in aggravating inflammation via reactive oxygen species (ROS). The Keap1-Nrf2-ARE pathway is a key mechanism in cellular resistance to oxidative stress by mediating and activating a variety of antioxidant and detoxification enzymes. Following ROS accumulation, INPM induced abnormal expression of nuclear transcription factor Nrf2. This behavior disturbed the expression of, γ-glutamate synthase (γ-GCS) and heme oxygenase (HO-1), which further exacerbated the imbalance of the antioxidant system. ConclusionsThis functional 3D human organotypic chip effectively mimics the physiological response of the human BBB. The chip provides a micro-complex structure to simulate the internal environment of the human blood-brain barrier, and partially simulates the physiological responses of the BBB to INPM exposure. Based on this model, INPM was shown to affect the blood-brain barrier biofunction by disrupting the Keap1-Nrf2-ARE pathways.

Simulation of nanoparticle transport and adsorption in a microfluidic lung-on-a-chip device.

The effect of air-borne nanoparticles (NPs) on human health is an active area of research, with clinical relevance evidenced by the current COVID-19 pandemic. As in vitro models for such studies, lung-on-a-chip (LOAC) devices can represent key physical and physiological aspects of alveolar tissues. However, widespread adoption of the LOAC device for NP testing has been hampered by low intra-laboratory and inter-laboratory reproducibility. To complement ongoing experimental work, we carried out finite-element simulations of the deposition of NPs on the epithelial layer of a well-established LOAC design. We solved the Navier-Stokes equations for the fluid flow in a three-dimensional domain and studied the particle transport using Eulerian advection-diffusion for fine NPs and Lagrangian particle tracking for coarse NPs. Using Langmuir and Frumkin kinetics for surface adsorption and desorption, we investigated NP adsorption under different exercise and breath-holding patterns. Conditions mimicking physical exercise, through changes in air-flow volume and breathing frequency, enhance particle deposition. Puff profiles typical of smoking, with breath-holding between inhalation and exhalation, also increase particle deposition per breathing cycle. Lagrangian particle tracking shows Brownian motion and gravitational settling to be two key factors, which may cooperate or compete with each other for different particle sizes. Comparisons are made with experimental data where possible and they show qualitative and semi-quantitative agreement. These results suggest that computer simulations can potentially inform and accelerate the design and application of LOAC devices for analyzing particulate- and microbe-alveolar interactions.

Pilot deep RNA sequencing of worker blood samples from Singapore printing industry for occupational risk assessment

Several engineered nanomaterials (ENMs) are used in toner-based printing equipment (TPE) including laser printers and photocopiers to improve toner performance. High concentration of airborne nanoparticles due to TPE emissions has been documented in copy centers and chamber studies. Recent animal inhalation studies by our group suggested exposure to laser printer-emitted nanoparticles (PEPs) increased cardiovascular risk by impairing ventricular performance and inducing hypertension and arrhythmia, consistent with global transcriptomic and metabolomic profiling results. There has been no genome-wide transcriptomic analysis of workers exposed to TPE emissions to systematically assess the occupational exposure health risks. In this pilot study, deep RNA sequencing of blood samples of workers in two printing companies in Singapore was performed. The genome-scale analysis of the blood samples from TPE exposed workers revealed perturbed transcriptional activities related to inflammatory and immune responses, metabolism, cardiovascular impairment, neurological diseases, oxidative stress, physical morphogenesis/deformation, and cancer, when compared with the control peers (office workers). Many of these disease risks associated with particle inhalation exposures in such work environments were consistent with the observation from the PEPs rat inhalation studies. In particular, the cell adhesion molecules (CAMs) was a top significantly perturbed pathway in blood samples from exposed workers compared with the office workers in both companies. The protein expression of sICAM was verified in plasma of exposed workers, showing a positive correlation with daily average nanoparticle concentration in indoor air measured in these two companies. Larger scale genomic and molecular epidemiology studies in copier operators are warranted in order to assess potential risks from such particulate matter exposures.

PPDA-PMDA polyimide aerogels with tailored nanostructure assembly for air filtering applications

Due to their high porosity and nanoporous morphology, aerogels have presented unique properties and thus offered a very high potential capability to be used in leading applications such as super thermal insulation and nanoparticle filtering. However, controlling the aerogels’ morphology and as a result, tailoring their properties is still a challenge. In this study, polyimide aerogels are developed through imidization of highly reactive pyromellitic dianhydride (PMDA) and p-phenylene diamine (PPDA) monomers. Unlike other monomers, the fabricated PPDA-PMDA aerogels can maintain their solid structure without any crosslinking agent content. A combination of the distinct bonding nature of the two selected monomers and the role of the 1,3,5-benzenetricarbonyl tri-chloride (BTC) chemical crosslinker provide the possibility of tailoring the aerogel morphology and cell structure. The morphology of fabricated aerogels is precisely controlled from clusters of particles to fine fibrous by altering the crosslinking agent molar fraction. Tailoring aerogels morphology results in higher filtration performance, by reduced pore size to 3.5 nm and a more than 200% increase in air permeability over the other studied polyimide aerogels. Moreover, it results in 20% reduced thermal conductivity and more than 5 times improved compression modulus over the fabricated PPDA-PMDA aerogels with similar monomers composition, but different morphology. The fabricated PPDA-PMDA aerogels present relatively lower shrinkage, as low as 5.6%, over the previously studied PPDA diamine polyimide aerogels. Due to the tailored nanostructure assembly and improved performance, this study shows the capability of PPDA-PMDA aerogels to be utilized in airborne nanoparticle filtering applications.

Risk Assessment of Nanoparticle Exposure in a Calcium Carbonate Manufacturing Workshop with Six Control Banding Tools.

With wide production and use, nanometer calcium carbonate (nano-CaCO₃) has attracted much more concerns due to its potential inhalation toxicity in the occupational setting. It is of great significance to protect exposure workers by scientifically measuring the concentration of aerosol nano-CaCO₃ particles, evaluating the risk levels at the production sites and accordingly providing suggestions of improvement. In this study, the aerosol particle concentrations of six operating procedures in a nano-CaCO₃ production workshop were determined, including digesting, carbonization, modification, pressure filtration, drying and packaging. The relevant occupational exposure risk was assessed by six control banding (CB) tools, CB Nanotool, Stoffenmanager Nano, Nanosafer, the Guidance on Working Safely with Nanomaterials and Nanoproducts (GWSNN), French Agency for Food, Environmental and Occupational Health and Safety method (ANSES) and Precautionary Matrix for Synthetic Nanomaterials (Precautionary Matrix). It was found that there are quite high concentrations of airborne nanoparticles released from the nano-CaCO₃ production procedures in this workshop. Most aerosol particles were agglomerated with the sizes of primary particles about 100 nm. The number concentration of aerosol particles at packaging site is 407000 particles/cm³ in size range of 0.02-1.0 μm, which is 10 times higher than the aerosol particle concentration at the digestion site. Furthermore, there is a significant correlation between the metrics of number and surface area concentrations detected in this workshop. The risk assessment results indicate that this workshop has medium or high exposure risks of the occupational nanoparticle exposure. Detailed engineering control or personal occupational protection should be implemented to protect the occupational health in this workshop. Similar and comparable judgment results were obtained, although the input parameters for six risk assessment CB tools are different. It was found that Stoffenmanager nano and Nanosafer are more suitable for the risk assessment of this workshop comparing to the other four tools. It is recommended a wide applications of risk assessment tools to various nanotechnology related occupational settings for controlling the occupational health risks.

From nano to micrometer size particles – A characterization of airborne cement particles during construction activities

Although, photocatalytic cement contains nanosized TiO2, a possibly carcinogen, no exposure assessments exist for construction workers. We characterized airborne nanoparticle exposures during construction activities simulated in an exposure chamber. We collected some construction site samples for regular cement in Switzerland and Thailand for comparison. Airborne nanoparticles were characterized using scanning mobility particle sizer (SMPS), portable aerosol spectrometer (PAS), diffusion size classifier (DiSCmini), transmission electron microscopy (TEM), scanning electron microscope energy dispersive X-ray spectroscopy (SEM-EDX), and X-ray diffraction. Bagged photocatalytic cement had 2.0 wt% (GSD ± 0.55) TiO2, while TiO2 in aerosols reached 16.5 wt% (GSD ± 1.72) during bag emptying and 9.7 wt% (GSD ± 1.36) after sweeping. The airborne photocatalytic cement particles were far smaller (approximately 50 nm) compared to regular cement. Cutting blocks made from photocatalytic cement or concrete, resulted in similar amounts of airborne nano TiO2 (2.0 wt% GSD ± 0.57) particles as in bagged material. Both photocatalytic and regular cement had a geometric mean diameter (GMD) < 3.5 μm. Main exposures for Thai workers were during sweeping and Swiss workers during drilling and polishing cement blocks. Targeted nanoparticle exposure assessments are needed as a significantly greater exposure to nano TiO2 were observed than what would have been predicted from the material's nano- TiO2 contents.

Nanoparticle exposure and hazard in the ceramic industry: an overview of potential sources, toxicity and health effects

The ceramic industry is an industrial sector of great impact in the global economy that has been benefiting from advances in materials and processing technologies. Ceramic manufacturing has a strong potential for airborne particle formation and emission, namely of ultrafine particles (UFP) and nanoparticles (NP), meaning that workers of those industries are at risk of potential exposure to these particles. At present, little is known on the impact of engineered nanoparticles (ENP) on the environment and human health and no established Occupational Exposure Limits (OEL) or specific regulations to airborne nanoparticles (ANP) exposure exist raising concerns about the possible consequences of such exposure.In this paper, we provide an overview of the current knowledge on occupational exposure to NP in the ceramic industry and their impact on human health. Possible sources and exposure scenarios, a summary of the existing methods for evaluation and monitoring of ANP in the workplace environment and proposed Nano Reference Values (NRV) for different classes of NP are presented. Case studies on occupational exposure to ANP generated at different stages of the ceramic manufacturing process are described. Finally, the toxicological potential of intentional and unintentional ANP that have been identified in the ceramic industry workplace environment is discussed based on the existing evidence from in vitro and in vivo inhalation toxicity studies.

A Simple Method for Measuring Fine-to-Ultrafine Aerosols Using Bipolar Charge Equilibrium.

Low-cost methods for measuring airborne microparticles and nanoparticles (aerosols) have remained elusive despite the increasing concern of health impacts from ambient, urban, and indoor sources. While bipolar ion sources are common in smoke alarms, this work is the first to exploit the mean charge on an aerosol resulting from a bipolar charge equilibrium and establish experimentally its correlation to properties of the aerosol particle size distribution. The net current produced from this mean particle charge is demonstrated to be linearly proportional to the product of the mean particle diameter and total number concentration (i ∼ Nd̅) for two bipolar ion sources (85Kr and 241Am). This conclusion is supported by simple equations derived from well-established bipolar charging theory. The theory predicts that the mean charge on the aerosol particles reaches an equilibrium, which, importantly, is independent of the concentration of charging ions. Furthermore, in situ measurements of a roadside aerosol demonstrate that the sensing method yields results in good agreement (R2 = 0.979) with existing portable and laboratory-grade aerosol instruments. The simplicity, stability, and cost of the bipolar ion source overcome challenges of other portable sensors, increasing the feasibility of widespread sensor deployment to monitor ultrafine particle characteristics, which are relevant to lung deposition and by extension, human health.

Polyimide aerogels with novel bimodal micro and nano porous structure assembly for airborne nano filtering applications.

Aerogels have presented a very high potential to be utilized as airborne nanoparticles' filtration media due to their nanoscale pore size and extremely high porosity. The filtering performance of aerogels, such as air permeability and filtration efficiency, is highly related to the configuration of aerogels' nanostructure assembly. However, as aerogel morphology is formed with respect to the intermolecular forces during the gelation stage, tailoring the aerogel nanostructure assembly is still a challenge. In this work, a novel strategy for tailoring polyimide aerogel nanostructure assembly is proposed by controlled disturbing of the intermolecular forces. From the results, the nanostructure assembly of the 4,4′-oxydianiline (ODA)–biphenyl-tetracarboxylic acid dianhydride (BPDA) polyimide aerogel is tailored to a uniform bimodal micro and nano porous structure. This was achieved by introducing the proper fraction of thermoplastic polyurethane (TPU) chains to the polyimide chains in the solution state and through a controlled process. The fabricated polyimide/TPU aerogels with bimodal morphology presented enhanced filtration performance, with 30% improved air permeability and reduced cell size of 3.51 nm over the conventional ODA–BPDA polyimide aerogels. Moreover, the fabricated bimodal aerogels present the reduced shrinkage, density, and effective thermal conductivity of 6.3% and 0.063 g cm−3, 28.7 mW m−1 K−1, respectively. Furthermore, the bimodal polyimide/TPU aerogels show the higher porosity of 96.5 vol% along with increased mechanical flexibility over the conventional polyimide aerogel with comparable backbone chemistry.

Getting insight into the influence of coexisting airborne nanoparticles on gas adsorption performance over porous materials

Adsorption as one of the most important air cleaning methods has been extensively applied during which the coexisting airborne nanoparticles (NPs) with sizes close to adsorbent pore sizes could inevitably influence gas adsorption processes. In this work, the influence of sub-20 nm NPs on toluene adsorption on ZSM-5 zeolites exchanged with different cations (Li+, Na+ and K+) were studied based on gas-and-particle coexisting adsorption/filtration tests. Affinities for both toluene and NPs on adsorbents follow Li-ZSM-5 > Na-ZSM-5 > K-ZSM-5 regarding the orders of charge density, pore size, and internal and external specific surface areas. The toluene adsorption was shown to be impaired by coexisting NPs from perspectives of thermodynamics and kinetics. For Li-ZSM-5, Na-ZSM-5 and K-ZSM-5, significant relative reductions of 10.4 %, 10.5 % and 16.0 % in toluene adsorption capacity at the lower feed concentration, and of 20.3 %, 15.2 % and 2.3 % in mass transfer coefficient at the higher feed concentration were observed, respectively. The influential mechanisms regarding competitiveness between toluene and NPs in interaction with cationic and porous surfaces were accordingly proposed, which are of practical significance for selecting robust adsorbents under realistic harsh air conditions.

Development of methodology to generate, measure, and characterize the chemical composition of oxidized mercury nanoparticles.

The phase of oxidized mercury is critical in the fate, transformation, and bioavailability of mercury species in Earth's ecosystem. There is now evidence that what is measured as gaseous oxidized mercury (GOM) is not only gaseous but also consists of airborne nanoparticles with distinct physicochemical properties. Herein, we present the development of the first method for the consistent and reproducible generation of oxidized mercury nano- and sub-micron particles (~ 5 to 400nm). Oxidized mercury nanoparticles are generated using two methods, vapor-phase condensation and aqueous nebulization, for three proxies: mercury(II) bromide (HgBr2), mercury(II) chloride (HgCl2), and mercury(II) oxide (HgO). These aerosols are characterized using scanning mobility and optical sizing, high-resolution scanning transmission electron microscopy (STEM), and nano/microparticle interface coupled to soft ionization mercury mass spectrometric techniques. Synthetic nanoparticle stability was studied in aqueous media, and using a microcosm at ambient troposphericconditions of ~ 740Torr pressure, room temperature, and at relative humidity of approximately 20%. Analysis of microcosm airborne nanoparticles confirmed that generated synthetic mercury nanoparticles retain their physical properties once in air. KCl-coated denuders, which are currently used globally to measure gaseous mercurycompounds,were exposed to generated oxidized mercury nanoparticles. The degree of synthetic mercury nanoparticlecapture by KCl-coated denuders and particulate filterswas assessed. A significant portion of nanoparticulate and sub-micron particulate mercury was trapped on the KCl-coated denuder and measured as GOM. Finally, we demonstrate the applicability of soft ionization mercury mass spectrometry to the measurement of mercury species present in the gaseous and solid phase. We recommend couplingof this techniquewith existing methodology for a more accurate representation of mercury biogeochemistry cycling. Graphical Abstract.

Variability of aerosol mass and number concentrations during taconite mining operations

This study characterized concentration metrics of airborne nanoparticles and their time series across major operations of a taconite mine through monitoring respirable and ultrafine particle concentrations at four major processing departments of the mine: crushing, dry milling, wet milling, and pelletizing (United Taconite Mine, Iron Junction, MN, USA). We used three area stations of direct-reading instruments to estimate concentration metrics including PM1 (particles with an aerodynamic diameter <1 µm), respirable dust (particles sampled according to the respirable convention with a 50% sampling efficiency at an aerodynamic diameter of 4 µm), PN (total number concentration of particles), and lung-deposited surface area concentrations (LDSA) of particles smaller than 300 nm, on two different days. Results for each station were compared using bivariate correlation analysis to obtain insight into the spatial distribution, and intra-class correlation coefficients (ICCs) to evaluate the between-day repeatability between the measurements. Comparability of the LDSA concentrations measured by two different devices was also investigated using linear regression. Results revealed that the pelletizing operation produced the highest average LDSA concentration on both days (with a maximum concentration of 199 ± 48 µm2/cm3 in pelletizing, 141 ± 52 µm2/cm3 in crushing, 91 ± 9 µm2/cm3 in dry milling, and 85 ± 7 µm2/cm3 in wet milling). Concentrations in all operations showed a fair to excellent between-day repeatability but they were significantly different within stations of each operation. Measured LDSA concentrations did not show a linear correlation between different instruments, except for crushing.

Airborne nanoparticle (Nanoaerosol) sampling efficiency analysis based on filtration on TEM grid

The scientific and technological issues associated with the characterization of the exposure of nano-aerosols is a huge technological challenge. Nano-aerosol measurement is a key point to characterize nanoparticle exposure. Transmission electron microscopy (TEM) coupled with energy-dispersive X-ray (EDX) is a comprehensive tool for determining size distributions and elemental compositions. Individual particle analysis allows the determination of size, morphology, specific surface, and elemental composition. Techniques allowing sampling on adapted analysis support TEM grids are of great interest to aerosol analysis: by using MPS and TEM analysis, sampling is directly and easily performed. The current paper explores the available theoretical models which assess sampling efficiency according to the chosen empirical approach. The recent studies which use this method are also briefly introduced.

Intercomparison in the laboratory of various Condensation Particle Counters challenged by nanoaerosols in the range 6 – 460 nm

This study aim is to compare the number concentration of airborne nanoparticles reported by 13 different Condensation Particle Counters (CPC) with regards to a reference CPC, for a set of aerosols of interest. Among the models investigated, 5 are handheld CPC, while the 8 others are stationary CPC. The latter include butanol-based CPC as well as water-based CPC. Polydisperse test aerosols with modal diameters between 6 and 460 nm were produced in the CAIMAN experimental facility. Non-hydrophobic aerosols consisted of metal-based particles (Ti, C, Al, Cu, Ag), as well as nebulized suspensions (SiO2). Hydrophobic particles consisted of DEHS as well as alkanes (n-C13 to n-C20). Overall, about 400 different conditions were investigated to represent a wide range of aerosols potentially encountered in workplaces. The range of number concentrations provided by the reference CPC was 500 – 400 000 cm−3. To highlight the possible effect of particle counting efficiency on the total concentration reported by the different CPCs, 40% of the test aerosols presented a modal diameter below 40 nm. The influence of particle material for water-based CPCs was investigated through the generation of about 100 hydrophobic test aerosols. CPC response was found to be sensitive to the mode of the aerosols measured, depending on the counting efficiency curve of the CPC investigated. An effect of particle hydrophobicity on the response of some water-based CPC models was demonstrated, while one water-based CPC did not show any material dependence.

Condensational particle growth device for reliable cell exposure at the air-liquid interface to nanoparticles.

A first-of-its-kind aerosol exposure device for toxicity testing, referred to as the Dosimetric Aerosol in Vitro Inhalation Device (DAVID), was evaluated for its ability to deliver airborne nanoparticles to lung cells grown as air-liquid interface (ALI) cultures. For inhalation studies, ALI lung cell cultures exposed to airborne nanoparticles have more relevancy than the same cells exposed in submerged culture because ALI culture better represents the respiratory physiology and consequently more closely reflect cellular response to aerosol exposure. In DAVID, water condensation grows particles as small as 5 nm to droplets sized > 5 μm for inertial deposition at low flow rates. The application of DAVID for nanotoxicity analysis was evaluated by measuring the amount and variability in the deposition of uranine nanoparticles and then assessing the viability of ALI cell cultures exposed to clean-air under the same operational conditions. The results showed a low coefficient of variation, < 0.25, at most conditions, and low variability in deposition between the exposure wells, trials, and operational flow rates. At an operational flow rate of 4 LPM, no significant changes in cell viability were observed, and minimal effects observed at 6 LPM. The reliable and gentle deposition mechanism of DAVID makes it advantageous for nanoparticle exposure.

Self-reading femtogram microbalance for highly sensitive airborne nanoparticle detection

In this paper, a self-reading miniaturized cantilever design for highly sensitive airborne nanoparticle (NP) detection is presented. The cantilever, which is operated in the fundamental in-plane resonance mode, is used as a microbalance with femtogram resolution. For maximum sensitivity and read-out signal amplitude, the geometric parameters of the sensor design were optimized by finite-element modelling (FEM). Piezo-resistive struts at both sides of the cantilever are employed for a Wheatstone half-bridge. This allows the electrical read-out of the phase information of a resonant cantilever of minimum mass. For electrostatic NP collection, the cantilever has a negative-biased electrode located at its free end. Moreover, μ-channels for guiding a particle-laden air flow and a counter-electrode around the cantilever tip are integrated. The presented airborne NP sensor is expected to demonstrate significant improvements in the field of handheld, MEMS-based NP monitoring devices.

Effectiveness of nanoparticle exposure mitigation measures in industrial settings.

Inhalation of airborne nanoparticles is a well-known source of potentially health-hazardous occupational exposures. Effective mitigation measures are necessary to reduce exposure, but also challenging to implement due to the different characteristics of each individual emission source and industrial scenario. The present paper describes four different exposure case studies in the ceramic industry and quantifies the effectiveness of mitigation strategies implemented during: ceramic tile processing by thermal spraying, laser ablation, the use of diesel engines, and tile firing. The mitigation measures for exposure reduction were tailored to each industrial scenario. The NP removal efficiency of source enclosure (partial/full) combined with local exhaust ventilation (LEV) were quantified to range between 65 and 85% when the enclosure was partial. The efficiency reached 99% with full enclosure and vigorous ventilation (Air Change per Hour; ACH = 132 h-1). The elimination of the source was the optimal strategy to minimize exposure in the case of diesel forklifts use. The conventional ceramic kilns used intensively (>10 years) generated high NP exposure concentrations (>106/cm3). Appropriate maintenance and enhanced sealing enabled the reduction of exposure down to 52% of the initial value. It must be added that technologically advanced kilns, enabled even greater NP reductions (down to 84%), compared to the conventional ones. This proves technological improvements can lead to significant reduction of work exposures. This work evidences the need for tailored mitigation measures due to the broad variety of potential sources and activities in industrial scenarios. The quantitative efficiency rates reported here may be valuable for the adequate parametrization of exposure prediction and risk assessment models.

Molecular insights on the interference of simplified lung surfactant models by gold nanoparticle pollutants

Inhaled nanoparticles (NPs) are experienced by the first biological barrier inside the alveolus known as lung surfactant (LS), a surface tension reducing agent, consisting of phospholipids and proteins in the form of the monolayer at the air-water interface. The monolayer surface tension is continuously regulated by the alveolus compression and expansion and protects the alveoli from collapsing. Inhaled NPs can reach deep into the lungs and interfere with the biophysical properties of the lung components. The interaction mechanisms of bare gold nanoparticles (AuNPs) with the LS monolayer and the consequences of the interactions on lung function are not well understood. Coarse-grained molecular dynamics simulations were carried out to elucidate the interactions of AuNPs with simplified LS monolayers at the nanoscale. It was observed that the interactions of AuNPs and LS components deform the monolayer structure, change the biophysical properties of LS and create pores in the monolayer, which all interfere with the normal lungs function. The results also indicate that AuNP concentrations >0.1 mol% (of AuNPs/lipids) hinder the lowering of the LS surface tension, a prerequisite of the normal breathing process. Overall, these findings could help to identify the possible consequences of airborne NPs inhalation and their contribution to the potential development of various lung diseases.

Nanoparticle Emissions From Metal-Assisted Chemical Etching of Silicon Nanowires for Lithium Ion Batteries

As one of the most promising anode materials for high-capacity lithium ion batteries (LIBs), silicon nanowires (SiNWs) have been studied extensively. The metal-assisted chemical etching (MACE) is a low-cost and scalable method for SiNW synthesis. Nanoparticle emissions from the MACE process, however, are of grave concerns due to their hazardous effects on both occupational and public health. In this study, both airborne and aqueous nanoparticle emissions from the MACE process for SiNWs with three sizes of 90 nm, 120 nm, and 140 nm are experimentally investigated. The prepared SiNWs are used as anodes of LIB coin cells, and the experimental results reveal that the initial discharge and charge capacities of LIB electrodes are 3636 and 2721 mAh g−1 with 90 nm SiNWs, 3779 and 2712 mAh g−1 with 120 nm SiNWs, and 3611 and 2539 mAh g−1 with 140 nm SiNWs. It is found that for 1 kW h of LIB electrodes, the MACE process for 140 nm SiNWs produces a high concentration of airborne nanoparticle emissions of 2.48 × 109 particles/cm3; the process for 120 nm SiNWs produces a high mass concentration of aqueous particle emissions, with a value of 9.95 × 105 mg/L. The findings in this study can provide experimental data of nanoparticle emissions from the MACE process for SiNWs for LIB applications and can help the environmental impact assessment and life cycle assessment of the technology in the future.

Strategy toward Miniaturized, Self-out-Readable Resonant Cantilever and Integrated Electrostatic Microchannel Separator for Highly Sensitive Airborne Nanoparticle Detection.

In this paper, a self-out-readable, miniaturized cantilever resonator for highly sensitive airborne nanoparticle (NP) detection is presented. The cantilever, which is operated in the fundamental in-plane resonance mode, is used as a microbalance with femtogram resolution. To maximize sensitivity and read-out signal amplitude of the piezo-resistive Wheatstone half bridge, the geometric parameters of the sensor design are optimized by finite element modelling (FEM). The electrical read-out of the cantilever movement is realized by piezo-resistive struts at the sides of the cantilever resonator that enable real-time tracking using a phase-locked loop (PLL) circuit. Cantilevers with minimum resonator mass of 1.72 ng and resonance frequency of ~440 kHz were fabricated, providing a theoretical sensitivity of 7.8 fg/Hz. In addition, for electrostatic NP collection, the cantilever has a negative-biased electrode located at its free end. Moreover, the counter-electrode surrounding the cantilever and a µ-channel, guiding the particle-laden air flow towards the cantilever, are integrated with the sensor chip. µ-channels and varying sampling voltages will also be used to accomplish particle separation for size-selective NP detection. To sum up, the presented airborne NP sensor is expected to demonstrate significant improvements in the field of handheld, micro-/nanoelectromechanical systems (M/NEMS)-based NP monitoring devices.