Single-Particle Analysis for Structure and Iron Chemistry of Atmospheric Particulate Matter

Generation and persistency of combustion-derived environmentally persistent free radicals from phenolic compounds over a Fe2O3/SiO2 surface

Combustion of organic solid wastes releases phenolic compounds which can act as precursors in the formation of environmentally persistent free radicals (EPFRs) in the post-flame, cooling zone of waste combustion. The study investigated the generation mechanism of EPFRs from phenolic compounds catalyzed by transition metals in air atmosphere under simulated combustion conditions. Representative combustion-derived phenolic compounds were used, and SiO2 particulates containing different mass ratio of Fe2O3 were synthesized as carriers. EPFRs formed had g-factors between 1.9998 and 2.0066, indicating phenoxyl-, cyclopentadienyl-, and semiquinone-type radicals, along with paramagnetic F-centers. The promotion effect of phenolic compounds on EPFR formation during heating decreased as catechol > hydroquinone > phenol > p-cresol. This trend is related to hydroxyl groups and activation energy. In particular, catechol chemically adsorbed on Fe2O3 at 600 K led to the formation of EPFRs with relatively high spin concentrations (up to 1.28 × 1017 spin/g). Higher Fe2O3 concentrations promoted the transformation of phenoxyl-type radicals into cyclopentadienyl-type and paramagnetic F-centers. However, as the Fe2O3 loading increased from 1.25% to 5%, the density of EPFRs decreased. The findings related to the influence of various precursors and Fe2O3 concentration on EPFR formation provide valuable insights for estimating EPFR generation and associated risk during combustion processes.

Air pollution generated in an industrial region: Effect on the cardiovascular health of humans and damage caused to a plant species, Piper gaudichaudianum (Piperaceae), used for biomonitoring

Atmospheric pollution due to anthropogenic activities is a complex mixture of gasses and particulate matter (PM) that is currently one of the main causes of premature death in the world. Similarly, it is also capable of directly interfering with plant species by reducing their photosynthetic capacity and growth and killing cells. This work is about an observational study conducted in a region with two industries: a mine and an automobile parts manufacturer. Mining rocks is a source of PM in the air like that caused by other industrial activities. Twenty-five people that work or live in the industrial region cited (area A) and 25 people that live further away (area B) were selected to evaluate their vital signs and conduct a transthoracic echocardiogram. Leaves of Piper gaudichaudianum (Piperaceae), a native plant species, were also collected in both areas and evaluated in a laboratory. The PM accumulated on the leaves was evaluated using scanning electron microscopy (SEM) and inductively coupled plasma-optical emission spectrometry (ICP-OES). A statistical difference (P < 0.05) was verified for the levels of systolic blood pressure (SBP), diastolic blood pressure (DBP), and left ventricular mass index by echocardiography; the values were greater in people in area A. For the plant analysis, there was a statistical difference for all characters evaluated, chlorophyll levels, fresh mass, dry mass and leaf area were reduced, and thickness was greater in area A (P < 0.001). The PM analysis revealed a predominance of silicon, iron, and aluminum chemical elements. The present study suggests that particulate matter pollution is harmful to both humans and the flora.

Engineering bionanoreactor in bacteria for efficient hydrogen production

Hydrogen production through water splitting is a vital strategy for renewable and sustainable clean energy. In this study, we developed an approach integrating nanomaterial engineering and synthetic biology to establish a bionanoreactor system for efficient hydrogen production. The periplasmic space (20 to 30 nm) of an electroactive bacterium, Shewanella oneidensis MR-1, was engineered to serve as a bionanoreactor to enhance the interaction between electrons and protons, catalyzed by hydrogenases for hydrogen generation. To optimize electron transfer, we used the microbially reduced graphene oxide (rGO) to coat the electrode, which improved the electron transfer from the electrode to the cells. Native MtrCAB protein complex on S. oneidensis and self-assembled iron sulfide (FeS) nanoparticles acted in tandem to facilitate electron transfer from an electrode to the periplasm. To enhance proton transport, S. oneidensis MR-1 was engineered to express Gloeobacter rhodopsin (GR) and the light-harvesting antenna canthaxanthin. This led to efficient proton pumping when exposed to light, resulting in a 35.6% increase in the rate of hydrogen production. The overexpression of native [FeFe]-hydrogenase further improved the hydrogen production rate by 56.8%. The bionanoreactor engineered in S. oneidensis MR-1 achieved a hydrogen yield of 80.4 μmol/mg protein/day with a Faraday efficiency of 80% at a potential of -0.75 V. This periplasmic bionanoreactor combines the strengths of both nanomaterial and biological components, providing an efficient approach for microbial electrosynthesis.

Three-Dimensional Label-Free Observing of the Self-Assembled Nanoparticles inside a Single Cell at Nanoscale Resolution

Understanding the intracellular behavior of nanoparticles (NPs) plays a key role in optimizing the self-assembly performance of nanomedicine. However, conducting the 3D, label-free, quantitative observation of self-assembled NPs within intact single cells remains a substantial challenge in complicated intracellular environments. Here, we propose a deep learning combined synchrotron radiation hard X-ray nanotomography approach to visualize the self-assembled ultrasmall iron oxide (USIO) NPs in a single cell. The method allows us to explore comprehensive information on NPs, such as their distribution, morphology, location, and interaction with cell organelles, and provides quantitative analysis of the heterogeneous size and morphologies of USIO NPs under diverse conditions. This label-free, in situ method provides a tool for precise characterization of intracellular self-assembled NPs to improve the evaluation and design of a bioresponsive nanomedicine.

Microscopic and spectroscopic analysis of atmospheric iron-containing single particles in Lhasa, Tibet

The Tibetan Plateau, known as the "Third Pole", is currently in a state of perturbation caused by intensified human activity. In this study, 56 samples were obtained at the five sampling sites in typical area of Lhasa city and their physical and chemical properties were investigated by TEM/EDS, STXM, and NEXAFS spectroscopy. After careful examination of 3387 single particles, the results showed that Fe should be one of the most frequent metal elements. The Fe-containing single particles in irregular shape and micrometer size was about 7.8% and might be mainly from local sources. Meanwhile, the Fe was located on the subsurface of single particles and might be existed in the form of iron oxide. Interestingly, the core-shell structure of iron-containing particles were about 38.8% and might be present as single-, dual- or triple-core shell structure and multi-core shell structure with the Fe/Si ratios of 17.5, 10.5, 2.9 and 1.2, respectively. Meanwhile, iron and manganese were found to coexist with identical distributions in the single particles, which might induce a synergistic effect between iron and manganese in catalytic oxidation. Finally, the solid spherical structure of Fe-containing particles without an external layer were about 53.4%. The elements of Fe and Mn were co-existed, and might be presented as iron oxide-manganese oxide-silica composite. Moreover, the ferrous and ferric forms of iron might be co-existed. Such information can be valuable in expanding our understanding of Fe-containing particles in the Tibetan Plateau atmosphere.

In situ label-free X-ray imaging for visualizing the localization of nanomedicines and subcellular architecture in intact single cells

Understanding the intracellular behaviors of nanomedicines and morphology variation of subcellular architecture impacted by nanomaterial-biology (nano-bio) interactions could help guide the safe-by-design, manufacturing and evaluation of nanomedicines for clinical translation. The in situ and label-free analysis of nano-bio interactions in intact single cells at nanoscale remains challenging. We developed an approach based on X-ray microscopy to directly visualize the 2D or 3D intracellular distribution without labeling at nanometer resolution and analyze the chemical transformation of nanomedicines in situ. Here, we describe an optimized workflow for cell sample preparation, beamline selection, data acquisition and analysis. With several model bionanomaterials as examples, we analyze the localization of nanomedicines in various primary blood cells, macrophages, dendritic cells, monocytes and cancer cells, as well as the morphology of some organelles with soft and hard X-rays. Our protocol has been successfully implemented at three beamline facilities: 4W1A of Beijing Synchrotron Radiation Facility, BL08U1A of Shanghai Synchrotron Radiation Facility and BL07W of the National Synchrotron Radiation Laboratory. This protocol can be completed in ~2-5 d, depending on the cell types, their incubation times with nanomaterials and the selected X-ray beamline. The protocol enables the in situ analysis of the varieties of metal-containing nanomaterials, visualization of intracellular endocytosis, distribution and excretion and corresponding subcellular morphological variation influenced by nanomedicines in cell lines or primary cells by using this universal and robust platform. The results facilitate the understanding of the true principle and mechanism underlying the nano-bio interaction.

Designing Smart Iron Oxide Nanoparticles for MR Imaging of Tumors

Iron oxide nanoparticles (IONPs) possess unique magnetism and good biocompatibility, and they have been widely applied as contrast agents (CAs) for magnetic resonance imaging (MRI). Traditional CAs typically show a fixed enhanced signal, thus exhibiting the limitations of low sensitivity and a lack of specificity. Nowadays, the progress of stimulus-responsive IONPs allows alteration of the relaxation signal in response to internal stimuli of the tumor, or external stimuli, thus providing an opportunity to overcome those limitations. This review summarizes the current status of smart IONPs as tumor imaging MRI CAs that exhibit responsiveness to endogenous stimuli, such as pH, hypoxia, glutathione, and enzymes, or exogenous stimuli, such as magnets, light, and so on. We discuss the challenges and future opportunities for IONPs as MRI CAs and comprehensively illustrate the applications of these stimuli-responsive IONPs. This review will help provide guidance for designing IONPs as MRI CAs and further promote the reasonable design of magnetic nanoparticles and achieve early and accurate tumor detection.

Three-dimensional label-free visualization of the interactions of PM2.5 with macrophages and epithelial cells using optical diffraction tomography

Particulate matter ≤ 2.5 µm (PM2.5) poses health risks related to various diseases and infections. However, the interactions between PM2.5 and cells such as uptake and cell responses have not been fully investigated despite advances in bioimaging techniques, because the heterogeneous morphology and composition of PM2.5 make it challenging to employ labeling techniques, such as fluorescence. In this work, we visualized the interaction between PM2.5 and cells using optical diffraction tomography (ODT), which provides quantitative phase images by refractive index distribution. Through ODT analysis, the interactions of PM2.5 with macrophages and epithelial cells, such as intracellular dynamics, uptake, and cellular behavior, were successfully visualized without labeling techniques. ODT analysis clearly shows the behavior of phagocytic macrophages and nonphagocytic epithelial cells for PM2.5. Moreover, ODT analysis could quantitatively compare the accumulation of PM2.5 inside the cells. PM2.5 uptake by macrophages increased substantially over time, but uptake by epithelial cells increased only marginally. Our findings indicate that ODT analysis is a promising alternative approach to visually and quantitatively understanding the interaction of PM2.5 with cells. Therefore, we expect ODT analysis to be employed to investigate the interactions of materials and cells that are difficult to label.

Spatial Metallomics Reveals Preferable Accumulation of Methylated Selenium in a Single Seed of the Hyperaccumulator Cardamine violifolia†

Cardamine violifolia is a Se hyperaccumulator found in Enshi, China. In this study, spatial metallomics was applied to visualize the distribution and speciation of Se in a single seed of C. violifolia. It was found that Se reached 1729.89 ± 28.14 mg/kg and the main Se species were SeCys and SeMet in bulk seeds. Further in situ study on a single seed found that the methylated Se species located mostly in the episperm. This is the first visualized evidence of the in situ distribution of methylated Se species in the seeds of C. violifolia. In all, spatial metallomics finds a preferable accumulation of methylated Se species in the seed coat, which deepens the understanding of the tolerance of Se by C. violifolia. The protocol applied in this study may also be used for the understanding of the tolerance of heavy metals/metalloids in other hyperaccumulators.

Ferroptosis: challenges and opportunities for nanomaterials in cancer therapy

Ferroptosis, a completely new form of regulated cell death, is mainly caused by an imbalance between oxidative damage and reductive protection and has shown great anti-cancer potential. However, existing small-molecule ferroptosis inducers have various limitations, such as poor water solubility, drug resistance and low targeting ability, hindering their clinical applications. Nanotechnology provides new opportunities for ferroptosis-driven tumor therapy. Especially, stimuli-responsive nanomaterials stand out among others and have been widely researched because of their unique spatiotemporal control advantages. Therefore, it's necessary to summarize the application of those stimuli-responsive nanomaterials in ferroptosis. Here, we describe the physiological feature of ferroptosis and illustrate the current challenges to induce ferroptosis for cancer therapy. Then, nanomaterials that induce ferroptosis are classified and elaborated according to the external and internal stimuli. Finally, the future perspectives in the field are proposed. We hope this review facilitates paving the way for the design of intelligent nano-ferroptosis inducers.

Advanced Light Source Analytical Techniques for Exploring the Biological Behavior and Fate of Nanomedicines

Exploration of the biological behavior and fate of nanoparticles, as affected by the nanomaterial-biology (nano-bio) interaction, has become progressively critical for guiding the rational design and optimization of nanomedicines to minimize adverse effects, support clinical translation, and aid in evaluation by regulatory agencies. Because of the complexity of the biological environment and the dynamic variations in the bioactivity of nanomedicines, in-situ, label-free analysis of the transport and transformation of nanomedicines has remained a challenge. Recent improvements in optics, detectors, and light sources have allowed the expansion of advanced light source (ALS) analytical technologies to dig into the underexplored behavior and fate of nanomedicines in vivo. It is increasingly important to further develop ALS-based analytical technologies with higher spatial and temporal resolution, multimodal data fusion, and intelligent prediction abilities to fully unlock the potential of nanomedicines. In this Outlook, we focus on several selected ALS analytical technologies, including imaging and spectroscopy, and provide an overview of the emerging opportunities for their applications in the exploration of the biological behavior and fate of nanomedicines. We also discuss the challenges and limitations faced by current approaches and tools and the expectations for the future development of advanced light sources and technologies. Improved ALS imaging and spectroscopy techniques will accelerate a profound understanding of the biological behavior of new nanomedicines. Such advancements are expected to inspire new insights into nanomedicine research and promote the development of ALS capabilities and methods more suitable for nanomedicine evaluation with the goal of clinical translation.

Long-term respiratory exposure to amorphous silica nanoparticles promoted systemic inflammation and progression of fibrosis in a susceptible mouse model

Exposure to amorphous silica nanoparticles (SiNPs) has increased dramatically, and concerns are growing about their potential health effects. However, their long-term systemic toxicity profile and underlying mechanisms following respiratory exposure still remains unexplored. It is well documented that the inhalation of ultrafine particles is firmly associated with adverse effects in humans. Environmental pollutants may contribute to diverse adverse effect or comorbidity in susceptible individuals. Thereby, we examined the long-term systemic effects of inhaled SiNPs using a sensitive mouse model (ApoE^-/-) fed by a western diet. Male ApoE^-/- mice were intratracheally instilled with SiNPs suspension at a dose of 1.5, 3.0 and 6.0 mg/kg·bw, respectively, once per week, 12 times in total. The histological analysis was conducted. The serum cytokine levels were quantified by RayBiotech antibody array. As a result, systemic histopathological alterations were noticed, mainly characterized by inflammation and fibrosis. More importantly, cytokine array analysis indicated the key role of mast cells accumulation in systemic inflammation and fibrosis progression induced by inhaled SiNPs. Collectively, our study firstly demonstrated that long-term exposure to inhaled SiNPs promoted the mast cell-dominated activation of inflammatory response, not only in the lung but also in heart, liver and kidney, etc., eventually leading to the progression of tissue fibrosis in ApoE^-/- mice.

Air pollution: A culprit of lung cancer

Air pollution is a global health problem, especially in the context of rapid economic development and the expansion of urbanization. Herein, we discuss the harmful effects of outdoor and indoor pollution on the lungs. Ambient particulate matters (PMs) from industrial and vehicle exhausts is associated with lung cancer. Workers exposed to asbestos, polycyclic aromatic hydrocarbons (PAHs), and toxic metals are also likely to develop lung cancer. Indoors, cooking fumes, second-hand smoke, and radioactive products from house decoration materials play roles in the development of lung cancer. Bacteria and viruses can also be detrimental to health and are important risk factors in lung inflammation and cancer. Specific effects of lung cancer caused by air pollution are discussed in detail, including inflammation, DNA damage, and epigenetic regulation. In addition, advanced materials for personal protection, as well as the current government policies to prevent air pollution, are summarized. This review provides a basis for future research on the relationship between lung cancer and air pollution.

Regulating the synthesis rate and yield of bio-assembled FeS nanoparticles for efficient cancer therapy

Biosynthesis has gained growing interest due to its energy efficiency and environmentally benign nature. Recently, biogenic iron sulfide nanoparticles (FeS NPs) have exhibited excellent performance in environmental remediation and energy recovery applications. However, their biosynthesis regulation strategy and application prospects in the biomedical field remain to be explored. Herein, biogenic FeS NPs are controllably synthesized by Shewanella oneidensis MR-1 and applied for cancer therapy. Tuning the synthesis rate and yield of biogenic FeS NPs is realized by altering the initial iron precursor dosage. Notably, increasing the precursor concentration decreases and delays FeS NP biosynthesis. The biogenic FeS NPs (30 nm) are homogeneously anchored on the cell surface of S. oneidensis MR-1. Moreover, the good hydrophilic nature and outstanding Fenton properties of the as-prepared FeS NPs endow them with good cancer therapy performance. The intracellular location of the FeS NPs taken up is visualized with a soft X-ray microscope (SXM). Highly efficient cancer cell killing can be achieved at extremely low concentrations (<12 μg mL^-1), lower than those in reported works. Such good performance is attributed to the Fe²⁺ release, elevated ROS, reduced glutathione (GSH) consumption, and lipid hydroperoxide (LPO) generation. The resulting FeS NPs show excellent in vivo therapeutic performance. This work provides a facile, eco-friendly, and scalable approach to produce nanomedicine, demonstrating the potential of biogenic nanoparticles for use in cancer therapy.

Role of Ferryl Ion Intermediates in Fast Fenton Chemistry on Aqueous Microdroplets

In the aqueous environment, Fe^II ions enhance the oxidative potential of ozone and hydrogen peroxide by generating the reactive oxoiron species (ferryl ion, Fe^IVO²⁺) and hydroxyl radical (·OH) via Fenton chemistry. Herein, we investigate factors that control the pathways of these reactive intermediates in the oxidation of dimethyl sulfoxide (Me₂SO) in Fe^II solutions reacting with O₃ in both bulk-phase water and on the surfaces of aqueous microdroplets. Electrospray ionization mass spectrometry is used to quantify the formation of dimethyl sulfone (Me₂SO₂, from Fe^IVO²⁺ + Me₂SO) and methanesulfonate (MeSO₃^-, from ·OH + Me₂SO) over a wide range of Fe^II and O₃ concentrations and pH. In addition, the role of environmentally relevant organic ligands on the reaction kinetics was also explored. The experimental results show that Fenton chemistry proceeds at a rate ∼10⁴ times faster on microdroplets than that in bulk-phase water. Since the production of MeSO₃^- is initiated by ·OH radicals at diffusion-controlled rates, experimental ratios of Me₂SO₂/MeSO₃^- > 10² suggest that Fe^IVO²⁺ is the dominant intermediate under all conditions. Me₂SO₂ yields in the presence of ligands, L, vary as volcano-plot functions of E⁰(LFe^IVO²⁺+ O₂/LFe²⁺ + O₃) reduction potentials calculated by DFT with a maximum achieved in the case of L≡oxalate. Our findings underscore the key role of ferryl Fe^IVO²⁺ intermediates in Fenton chemistry taking place on aqueous microdroplets.

A new sample preparation protocol for SEM and TEM particulate matter analysis

A new methodology has been developed to prepare electron microscopy, both SEM and TEM, specimens starting from particulate matter collected using environmental sampling systems. The approach is based on the extraction of the particles to be analyzed from the harvesting substrates. The extracted particles can be directly observed in an SEM, possibly in low-vacuum mode to prevent electrical charging. In order to prepare electron transparent samples, TEM observations require a further step, consisting in embedding the particles in an electron transparent carbon film deposited before dissolving the acetate extracting substrate. The protocol has been tested by analyzing particles collected during bench tests on brake pads and discs, carried out on a dynamometer equipped with a particulate matter sampling apparatus. The main advantages of the approach are: the complete extraction of the particulate matter specimens from the original substrates, that in this way do not interfere with the analyses; the extracted samples retain the topological information of the collection in the specimens prepared for SEM; possibility to be applied to any kind of particulate matter harvesting substrates.

Design and application of nanoparticles as vaccine adjuvants against human corona virus infection

In recent years, some viruses have caused a grave crisis to global public health, especially the human coronavirus. A truly effective vaccine is therefore urgently needed. Vaccines should generally have two features: delivering antigens and modulating immunity. Adjuvants have an unshakable position in the battle against the virus. In addition to the perennial use of aluminium adjuvant, nanoparticles have become the developing adjuvant candidates due to their unique properties. Here we introduce several typical nanoparticles and their antivirus vaccine adjuvant applications. Finally, for the combating of the coronavirus, we propose several design points, hoping to provide ideas for the development of personalized vaccines and adjuvants and accelerate the clinical application of adjuvants.

X-ray-Based Techniques to Study the Nano-Bio Interface

X-ray-based analytics are routinely applied in many fields, including physics, chemistry, materials science, and engineering. The full potential of such techniques in the life sciences and medicine, however, has not yet been fully exploited. We highlight current and upcoming advances in this direction. We describe different X-ray-based methodologies (including those performed at synchrotron light sources and X-ray free-electron lasers) and their potentials for application to investigate the nano-bio interface. The discussion is predominantly guided by asking how such methods could better help to understand and to improve nanoparticle-based drug delivery, though the concepts also apply to nano-bio interactions in general. We discuss current limitations and how they might be overcome, particularly for future use in vivo.

The recovery of nano-sized carbon black filler structure and its contribution to stress recovery in rubber nanocomposites

The hierarchical structural evolution of natural rubber (NR) filled with different contents of nanoscale carbon black (CB) (10 phr-CB10 and 50 phr-CB50) after first loading and recovering for different times was investigated by X-ray nano-CT, wide-angle X-ray scattering (WAXS) and solid state NMR techniques. The CB filler structures as captured by X-ray nano-CT recover gradually with increasing recovering time, but the filler network with different CB contents shows dramatically different structure evolution. For CB10, limited by the filling content, CB particles mainly induces a hydrodynamic effect in spite of deformation or recovering. For CB50, the CB filler forms a 3D connected network, partially destructed during deformation, and the destructed part can be partially recovered during recovery. This suggests that the connected CB filler structure mainly acts as a network reinforcement, whereas the destructed part can induce a hydrodynamic effect. The different effects induced by different CB filling contents are also reflected by the NR matrix, which is reflected by the onset strains εc of strain-induced crystallization (SIC) of NR as captured by WAXS. For CB10, εc remains almost constant, i.e. εc = ca. 1.49, while that of NR with CB50 slightly decreases from initial ca. 1.12 to 0.96 with increasing recovering time up to 50 h. Also, the bound rubber fraction and entangled rubber network remain unchanged after deformation and under different recovery time as detected by the magic sandwich echo (MSE) FID and proton multiple quantum (MQ) NMR. These results demonstrate the key role of the CB filler network in determining the stress-softening behavior of reinforced rubber.

Nanostructured Cobalt-Based Electrocatalysts for CO2 Reduction: Recent Progress, Challenges, and Perspectives

CO₂ reduction reaction (CO₂ RR) provides a promising strategy for sustainable carbon fixation by converting CO₂ into value-added fuels and chemicals. In recent years, considerable efforts are focused on the development of transition-metal (TM)-based catalysts for the selectively electrochemical CO₂ reduction reaction (ECO₂ RR). Co-based catalysts emerge as one of the most promising electrocatalysts with high Faradaic efficiency, current density, and low overpotential, exhibiting excellent catalytic performance toward ECO₂ RR for CO and HCOOH productions that are economically viable. The intrinsic contribution of Co and the synergistic effects in Co-hybrid catalysts play essential roles for future commercial productions by ECO₂ RR. This review summarizes the rational design of Co-based catalysts for ECO₂ RR, including molecular, single-metal-site, and oxide-derived catalysts, along with the nanostructure engineering techniques to highlight the distribution of the ECO₂ RR products by Co-based catalysts. The density functional theory (DFT) simulations and advanced in situ characterizations contribute to interpreting the synergies between Co and other materials for the enhanced product selectivity and catalytic activity. Challenges and outlook concerning the catalyst design and reaction mechanism, including the upgrading of reaction systems of Co-based catalysts for ECO₂ RR, are also discussed.

PM2.5 triggered apoptosis in lung epithelial cells through the mitochondrial apoptotic way mediated by a ROS-DRP1-mitochondrial fission axis

Epidemiological studies revealed a sharp increase in respiratory diseases attributed to PM_2.5. However, the underlying mechanisms remain unclear. Evidence suggested mitochondrion as a sensitive target upon the stimulus of PM_2.5, and the centrality in the pathological processes and clinical characterization of lung diseases. To investigate cell fate and related mechanisms caused by PM_2.5, we exposed human lung epithelial cells (BEAS-2B) to PM_2.5 (0-100 μg/mL). Consequently, PM_2.5 components were found in cytoplasm, and morphological and functional alterations in mitochondria occurred, as evidenced by loss of cristae, vacuolization and even the outer mitochondrial membrane rupture, mitochondrial membrane potential collapse, enhanced reactive oxygen species (ROS)/mtROS level, calcium overload, suppressed cellular respiration and ATP production in PM_2.5-treated cells. Further, disturbed dynamics toward fission was clearly observed in PM_2.5-treated mitochondria, associated with DRP1 mitochondrial translocation and phosphorylation. Besides, PM_2.5 induced mitochondria-mediated apoptosis. More importantly, mechanistic results revealed ROS- and DRP1-mediated mitochondrial fission in a reciprocal way, and DRP1 inhibitor (Mdivi-1) significantly alleviated the pro-apoptotic effect of PM_2.5 through reversing the activated mitochondrial apoptotic pathway. In summary, our results firstly revealed PM_2.5 induced apoptosis in lung epithelial cells through a ROS-DRP1-mitochodrial fission axis-mediated mitochondrial apoptotic pathway, ultimately contributing to the onset and development of pulmonary diseases.

Farnesoid X receptor mediates hepatic steatosis induced by PM2.5

Ambient particulate matter (PM) newly has been regarded as a conceivable hazard for public health. A large number of studies have described that PM, exceptionally PM2.5, is correlated with respiratory, cardiovascular, and metabolic diseases, etc. PM2.5-induced hepatocyte steatosis previously has been uncovered both in cellular and murine models. Nevertheless, less is known about the underlying mechanism. Here, we found that PM2.5 could cause the downregulation of farnesoid X receptor (FXR), a key transcription factor for lipid metabolism. FXR could regulate the accumulation of lipid droplets induced by PM2.5 in vitro. Moreover, FXR-/- mice were exposed to PM2.5 for 2 months to investigate the role of FXR in pathogenesis of PM2.5-induced hepatic steatosis in vivo. The results showed that exposure of wild-type (WT) mice to PM2.5 caused mild liver steatosis compared with the mice exposure to filtered air (FA). Furthermore, the content of triglyceride (TG) and total cholesterol (TC) was elevated in WT mice liver triggered by the inhalation of PM2.5. However, there was no statistical difference in TG and TC content between FXR-/- mice with and without PM2.5 exposure. Overall, our finding suggested FXR mediated PM2.5-induced hepatic steatosis.

Nano-bio interactions: the implication of size-dependent biological effects of nanomaterials

Due to their many advantageous properties, nanomaterials (NMs) have been utilized in diverse consumer goods, industrial products, and for therapeutic purposes. This situation leads to a constant risk of exposure and uptake by the human body, which are highly dependent on nanomaterial size. Consequently, an improved understanding of the interactions between different sizes of nanomaterials and biological systems is needed to design safer and more clinically relevant nano systems. We discuss the sizedependent effects of nanomaterials in living organisms. Upon entry into biological systems, nanomaterials can translocate biological barriers, distribute to various tissues and elicit different toxic effects on organs, based on their size and location. The association of nanomaterial size with physiological structures within organs determines the site of accumulation of nanoparticles. In general, nanomaterials smaller than 20 nm tend to accumulate in the kidney while nanomaterials between 20 and 100 nm preferentially deposit in the liver. After accumulating in organs, nanomaterials can induce inflammation, damage structural integrity and ultimately result in organ dysfunction, which helps better understand the size-dependent dynamic processes and toxicity of nanomaterials in organisms. The enhanced permeability and retention effect of nanomaterials and the utility of this phenomenon in tumor therapy are also highlighted.