Investigation of Environmental Pollutant-Induced Lung Inflammation and Injury in a 3D Coculture-Based Microfluidic Pulmonary Alveolus System

In vitro assessment of ferroptosis of cells exposed to cigarette smoke aerosol using a self-designed on-chip evaluation system based on gas-liquid dual-dimensional exposure

Aerosol pollutants significantly cause health concerns. Herein, we established an original real-time aerosol exposure system that used a self-designed bionic-lung microfluidic chip. The chip features a 4 × 4 intersecting array within gas and liquid layers, creating 16 distinct microenvironments. A membrane situated between the layers offers attachment for cells and establishes a gas-liquid interface. This design provides a reliable screening capacity for investigating the biological effects of aerosol exposure in vitro by manipulating the gas and/or liquid conditions. Using this system, we validated that cigarette smoke (CS) aerosol triggered a concentration- and time-dependent reduction in cell viability and intracellular glutathione levels, accompanied by an increase in intracellular reactive oxygen species and Fe2+. Furthermore, CS aerosol significantly downregulated the expression of GPX4, SLC7A11, and FTL mRNA while inducing a notable increase in that of ACSL4 mRNA. Additionally, CS aerosol markedly stimulated the release of proinflammatory cytokines. Crucially, the ferroptosis inhibitor deferoxamine mesylate reversed these biological indicators. These results demonstrate that our novel bionic-lung chip presents a suitably achievable approach to investigate the biological effects induced by aerosol exposure.

Analysis of the response to cigarette smoke exposure in cell coculture and monoculture based on bionic-lung microfluidic chips

BACKGROUND

In vitro toxicity assessment studies with various experimental models and exposure modalities frequently generate diverse outcomes. In the prevalent experimental, aerosol pollutants are dissolved in culture medium through capture for exposure to two-dimensional planar cellular models in multiwell plates via immersion. However, this approach can generate restricted and inconclusive experimental data, significantly constraining the applicability of risk assessment outcomes. Herein, the in vitro cocultivation of lung epithelial and/or vascular endothelial cells was performed using self-designed bionic-lung microfluidic chip housing a gas-concentration gradient generator (GCGG) unit. Exposure experiments involving a concentration gradient of cigarette smoke (CS) aerosol were then conducted through an original assembled real-time aerosol exposure system.

RESULTS

Transcriptomic analysis revealed a potential involvement of the cGMP-signaling pathway following online CS aerosol exposure on different cell culture models. Furthermore, distinct responses to different concentrations of CS aerosol exposure on different culture models were highlighted by detecting inflammation- and oxidative stress-related biomarkers (i.e., cell viability, reactive oxygen species, nitric oxide, IL-6, IL-8, TNF-α, GM-CSF, malondialdehyde, and superoxide dismutase).

SIGNIFICANT

The results underscore the importance of improving chip biomimicry while addressing multi-throughput demands, given the substantial influence of the coculture model on cellular responses triggered by CS. Furthermore, the coculture model exhibited a mutually beneficial protective effect on cells at low CS concentrations within the GCGG unit, yet revealed a mutually amplified damaging effect at higher CS concentrations in contrast to the monoculture model.

The application of a self-designed microfluidic lung chip in the assessment of different inhalable aerosols

Microfluidic-based assessment platforms have recently attracted considerable attention and have been widely used for evaluating in vitro toxic effects. In the present study, we developed an original real-time aerosol exposure system, which focused on a self-designed microfluidic chip, in order to evaluate the toxicological effects following exposure to inhalable aerosols. The three-layer structured microfluidic chip enables real-time aerosol exposure at the gas-liquid interface. The comprehensive detection of toxic effect biomarkers based on this assessment platform encompasses transcriptomics, in situ fluorescence detection, and the identification of extracellular secretagogues. Correspondingly, the effects of selected inhalable aerosols such as cigarette smoke (CS), heated tobacco product smoke (HS), and electronic cigarette smoke (ES) on gene expression profiles, cell viability, intracellular biomarkers (reactive oxygen species and nitric oxide), apoptosis (caspase-3/7 activity), and extracellular biomarkers (IL-8, IL-1β, TNF-α, and malondialdehyde) in the BEAS-2B cells present on the chip were investigated. Following exposure to aerosols derived from CS, HS, and ES, the transcriptome analysis revealed differential expression in these cells. In addition, the overlapping DEGs from the different treatment groups were found to be primarily associated with stimuli and inflammatory responses. Correspondingly, each of the three categories of selected inhalable aerosols was confirmed to induce significant changes in biomarkers that were associated with toxic effects. These results suggest that the original real-time aerosol exposure system centered around a self-designed chip can be applied to the toxic effect evaluation of inhalable aerosol exposure.

Biomimetic microfluidic chips for toxicity assessment of environmental pollutants

Various types of pollutants widely present in environmental media, including synthetic and natural chemicals, physical pollutants such as radioactive substances, ultraviolet rays, and noise, as well as biological organisms, pose a huge threat to public health. Therefore, it is crucial to accurately and effectively explore the human physiological responses and toxicity mechanisms of pollutants to prevent diseases caused by pollutants. The emerging toxicological testing method biomimetic microfluidic chips (BMCs) exhibit great potential in environmental pollutant toxicity assessment due to their superior biomimetic properties. The BMCs are divided into cell-on-chips and organ-on-chips based on the distinctions in bionic simulation levels. Herein, we first summarize the characteristics, emergence and development history, composition and structure, and application fields of BMCs. Then, with a focus on the toxicity mechanisms of pollutants, we review the applications and advances of the BMCs in the toxicity assessment of physical, chemical, and biological pollutants, respectively, highlighting its potential and development prospects in environmental toxicology testing. Finally, the opportunities and challenges for further use of BMCs are discussed.

Understanding PFAS toxicity through cell culture metabolomics: Current applications and future perspectives

Per- and polyfluoroalkyl substances (PFAS), ubiquitous environmental contaminants, pose significant challenges to ecosystems and human health. While cell cultures have emerged as new approach methodologies (NAMs) in ecotoxicity research, metabolomics is an emerging technique used to characterize the small-molecule metabolites present in cells and to understand their role in various biological processes. Integration of metabolomics with cell cultures, known as cell culture metabolomics, provides a novel and robust tool to unravel the complex molecular responses induced by PFAS exposure. In vitro testing also reduces reliance on animal testing, aligning with ethical and regulatory imperatives. The current review summarizes key findings from recent studies utilizing cell culture metabolomics to investigate PFAS toxicity, highlighting alterations in metabolic pathways, biomarker identification, and the potential linkages between metabolic perturbations. Additionally, the paper discusses different types of cell cultures and metabolomics methods used for studies of environmental contaminants and particularly PFAS. Future perspectives on the combination of metabolomics with other advanced technologies, such as single-cell metabolomics (SCM), imaging mass spectrometry (IMS), extracellular flux analysis (EFA), and multi-omics are also explored, which offers a holistic understanding of environmental contaminants. The synthesis of current knowledge and identification of research gaps provide a foundation for future investigations that aim to elucidate the complexities of PFAS-induced cellular responses and contribute to the development of effective strategies for mitigating their adverse effects on human health.

Dynamic tissue model in vitro and its application for assessment of microplastics-induced toxicity to air-blood barrier (ABB)

The replication of the hominine physiological environment was identified as an effectual strategy to develop the physiological model in vitro to perform the intuitionistic assessment of toxicity of contaminations. Herein, we proposed a dynamic interface strategy that accurately mimicked the blood flow and shear stress in human capillaries to subtly evaluate the physiological damages. To proof the concept, the dynamic air-blood barrier (ABB) model in vitro was developed by the dynamic interface strategy and was utilized to assess the toxicity of polyethylene terephthalate microplastics (PET-MPs). The developed dynamic ABB model was compared with the static ABB model developed by the conventional Transwell® system and the animal model, then the performance of the dynamic ABB model in evaluation of the PET-MPs induced pulmonary damage via replicating the hominine ABB. The experimental data revealed that the developed dynamic ABB model in vitro effectively mimicked the physiological structure and barrier functions of human ABB, in which more sophisticated physiological microenvironment enabled the distinguishment of the toxicities of PET-MPs in different sizes and different concentrations comparing with the static ABB model constructed on Transwell® systems. Furthermore, the consistent physiological and biochemical characters adopted dynamic ABB model could be achieved in a quick manner referring with that of the mouse model in the evaluation of the microplastics-induced pulmonary damage. The proposed dynamic interface strategy supplied a general approach to develop the hominine physiological environment in vitro and exhibited a potential to develop the ABB model in vitro to evaluate the hazards of inhaled airborne pollutants.

Combining a lung microfluidic chip exposure model with transcriptomic analysis to evaluate the inflammation in BEAS-2B cells exposed to cigarette smoke

BACKGROUND

Typically, in vitro studies on the exposure of complex gaseous substances are performed in multi-well plate experiments by trapping and redissolving them, which could introduce potential bias into the results due to the use of inadequate trapping methods. Therefore, a more effective method is to expose complex gaseous substances in gaseous form online, such as using microfluidic chips in experiments. To address these challenges, we introduce a methodology that integrates a self-designed bionic-lung chip with transcriptome analysis to assess the impact of cigarette smoke (CS) exposure on changes in BEAS-2B cells cultured on-chip.

RESULTS

After the microfluidic chip underwent online gas exposure, total RNA was extracted via in situ cell lysis, and RNA-Seq transcriptome analysis was conducted. And the RNA-Seq findings revealed the significant involvement of the MAPK signaling pathway associated with the inflammatory response in the cellular effects induced by CS exposure. Moreover, the validation of inflammatory response-related biomarkers through in situ fluorescence corroborated the outcomes of the transcriptome analysis. Besides, the experiment involving the inhibition of inflammation by DEX on the microfluidic chip provided additional confirmation of the previous experimental findings.

SIGNIFICANT

In this study, we present an analytical strategy that combines microfluidic-based CS in situ exposure method with RNA-Seq technology. This strategy offers an experimental scheme for in situ exposure to complex gases, transcriptome analysis, and in situ fluorescence detection. Through the integration of the comprehensiveness of transcriptome analysis with the chip's direct and intuitive in situ fluorescence detection with the stability and reliability of RT-PCR and Western blot experiments, we have successfully addressed the challenges associated with in vitro risk assessment for online exposure to complex gaseous substances.

Lung viral infection modelling in a bioengineered whole-organ

Lung infections are one of the leading causes of death worldwide, and this situation has been exacerbated by the emergence of COVID-19. Pre-clinical modelling of viral infections has relied on cell cultures that lack 3D structure and the context of lung extracellular matrices. Here, we propose a bioreactor-based, whole-organ lung model of viral infection. The bioreactor takes advantage of an automated system to achieve efficient decellularization of a whole rat lung, and recellularization of the scaffold using primary human bronchial cells. Automatization allowed for the dynamic culture of airway epithelial cells in a breathing-mimicking setup that led to an even distribution of lung epithelial cells throughout the distal regions. In the sealed bioreactor system, we demonstrate proof-of-concept for viral infection within the epithelialized lung by infecting primary human airway epithelial cells and subsequently injecting neutrophils. Moreover, to assess the possibility of drug screening in this model, we demonstrate the efficacy of the broad-spectrum antiviral remdesivir. This whole-organ scale lung infection model represents a step towards modelling viral infection of human cells in a 3D context, providing a powerful tool to investigate the mechanisms of the early stages of pathogenic infections and the development of effective treatment strategies for respiratory diseases.

Sentinel supervised lung-on-a-chip: A new environmental toxicology platform for nanoplastic-induced lung injury

Nanoplastics are prevalent in the air and can be easily inhaled, posing a threat to respiratory health. However, there have been few studies investigating the impact of nanoplastics on lung injury, especially chronic obstructive pulmonary disease (COPD). Furthermore, cell and animal models cannot deeply understand the pollutant-induced COPD. Existing lung-on-a-chip models also lack interactions among immune cells, which are crucial in monitoring complex responses. In the study, we built the lung-on-a-chip to accurately recapitulate the structural features and key functions of the alveolar-blood barrier while integrating multiple immune cells. The stability and reliability of the lung-on-a-chip model were demonstrated by toxicological application of various environmental pollutants. We Further focused on exploring the association between COPD and polystyrene nanoplastics (PS-NPs). As a result, the cell viability significantly decreased as the concentration of PS-NPs increased, while TEER levels decreased and permeability increased. Additionally, PS-NPs could induce oxidative stress and inflammatory responses at the organ level, and crossed the alveolar-blood barrier to enter the bloodstream. The expression of α1-antitrypsin (AAT) was significantly reduced, which could be served as early COPD checkpoint on the lung-chips. Overall, the lung-on-a-chip provides a new platform for investigating the pulmonary toxicity of nanoplastics, demonstrating that PS-NPs can harm the alveolar-blood barrier, cause oxidative damage and inflammation, and increase the risk of COPD.

Design of a microfluidic lung chip and its application in assessing the toxicity of formaldehyde

In this work, a microfluidic lung chip with membrane supporting cell growth that can produce multiple concentration gradients of gas and liquid is introduced. The chip is composed of a gas gradient layer in the upper part, a porous membrane supporting cell growth in the middle and a liquid gradient layer in the lower part. The gas-liquid interface environment of the cells on the membrane can expose the cells to the gas in the upper layer and the liquid in the lower layer at the same time. Then, the chip is applied to the toxicity testing of formaldehyde in A549 cells. The results showed that at 6 × 10-5 mol/L formaldehyde, the survival rate of the cells in four channels were 90, 87, 81, and 71%, which shows a dose-response trend under the influence of different concentrations of formaldehyde. ROS staining results also showed that formaldehyde exposure at 6 × 10-5 mol/L lead to the increase of ROS level in the cells. These results suggest that the chip based on cell growth on membrane could be used for toxicological evaluation of environmental polluting gases.

Vessel-on-a-Chip: A Powerful Tool for Investigating Endothelial COVID-19 Fingerprints

Coronavirus disease (COVID-19) causes various vascular and blood-related reactions, including exacerbated responses. The role of endothelial cells in this acute response is remarkable and may remain important beyond the acute phase. As we move into a post-COVID-19 era (where most people have been or will be infected by the SARS-CoV-2 virus), it is crucial to define the vascular consequences of COVID-19, including the long-term effects on the cardiovascular system. Research is needed to determine whether chronic endothelial dysfunction following COVID-19 could lead to an increased risk of cardiovascular and thrombotic events. Endothelial dysfunction could also serve as a diagnostic and therapeutic target for post-COVID-19. This review covers these topics and examines the potential of emerging vessel-on-a-chip technology to address these needs. Vessel-on-a-chip would allow for the study of COVID-19 pathophysiology in endothelial cells, including the analysis of SARS-CoV-2 interactions with endothelial function, leukocyte recruitment, and platelet activation. "Personalization" could be implemented in the models through induced pluripotent stem cells, patient-specific characteristics, or genetic modified cells. Adaptation for massive testing under standardized protocols is now possible, so the chips could be incorporated for the personalized follow-up of the disease or its sequalae (long COVID) and for the research of new drugs against COVID-19.

Advances of microfluidic lung chips for assessing atmospheric pollutants exposure

Atmospheric pollutants, including particulate matters, nanoparticles, bioaerosols, and some chemicals, have posed serious threats to the environment and the human's health. The lungs are the responsible organs for providing the interface betweenthecirculatory system and the external environment, where pollutant particles can deposit or penetrate into bloodstream circulation. Conventional studies to decipher the mechanismunderlying air pollution and human health are quite limited, due to the lack of reliable models that can reproduce in vivo features of lung tissues after pollutants exposure. In the past decade, advanced near-to-native lung chips, combining cell biology with bioengineered technology, present a new strategy for atmospheric pollutants assessment and narrow the gap between 2D cell culture and in vivo animal models. In this review, the key features of artificial lung chips and the cutting-edge technologies of the lung chip manufacture are introduced. The recent progresses of lung chip technologies for atmospheric pollutants exposure assessment are summarized and highlighted. We further discuss the current challenges and the future opportunities of the development of advanced lung chips and their potential utilities in atmospheric pollutants associated toxicity testing and drug screening.

Emerging trends in the methodology of environmental toxicology: 3D cell culture and its applications

Human diseases and health concerns caused by environmental pollutants are globally emerging. Therefore, rapid and efficient evaluation of the effects of environmental pollutants on human health is essential. Due to the significant differences between humans and animals and the lack of physiologically related environments, animal models and two-dimensional (2D) culture cannot accurately describe toxicological effects and predict actual in vivo responses. To make up for the limitations of traditional environmental toxicology screening, three-dimensional (3D) culture has been developed. The 3D culture could provide a good organizational structure comparable to the complex internal environment of humans and produce a more realistic response to environmental pollutants, which has been used in drug development, toxicity evaluation, personalized therapy and biological mechanism research. The goal of environmental toxicology is to provide clues and support for the risk assessment and management of environmental pollutants. With the development of 3D culture that can reproduce specific physiological aspects loaded with specific cells that reflect human biology, interactions between pollutants and target tissues and organs can be explored to assess the acute and chronic adverse health effects of exposure to various environmental toxins. The 3D culture with great potential shows broad prospects in toxicology research and is expected to bridge the gap between 2D culture and animal models eventually. In this sense, we strongly recommend that 3D culture be used to identify and understand environmental toxins, which will greatly facilitate the public's comprehensive understanding of environmental toxins.

Primary exploration of host-microorganism interaction and enteritis treatment with an embedded membrane microfluidic chip of the human intestinal-vascular microsystem

Intestinal flora plays a crucial role in the host's intestinal health. Imbalances in the intestinal flora, when accompanied by inflammation, affect the host's intestinal barrier function. Understanding it requires studying how living cells and tissues work in the context of living organs, but it is difficult to form the three-dimensional microstructure intestinal-vascular system by monolayer cell or co-culture cell models, and animal models are costly and slow. The use of microfluidic-based organ chips is a fast, simple, and high-throughput method that not only solves the affinity problem of animal models but the lack of microstructure problem of monolayer cells. In this study, we designed an embedded membrane chip to generate an in vitro gut-on-a-chip model. Human umbilical vein endothelial cells and Caco-2 were cultured in the upper and lower layers of the culture chambers in the microfluidic chip, respectively. The human peripheral blood mononuclear cells were infused into the capillary side at a constant rate using an external pump to simulate the in vitro immune system and the shear stress of blood in vivo. The model exhibited intestine morphology and function after only 5 days of culture, which is significantly less than the 21 days required for static culture in the Transwell^® chamber. Furthermore, it was observed that drug-resistant bacteria triggered barrier function impairment and inflammation, resulting in enteritis, whereas probiotics (Lactobacillus rhamnosus GG) improved only partially. The use of Amikacin for enteritis is effective, whereas other antibiotic therapies do not work, which are consistent with clinical test results. This model may be used to explore intestinal ecology, host and intestinal flora interactions, and medication assessment.

Nanostructured electrochemical sensor applied to the electrocoagulation of arsenite in WWTP effluent

A sensitive electroanalytical method for the determination of arsenite, based on a heterostructure of aminated multiwalled carbon nanotubes and gold nanoparticles, was applied in an electrocoagulation (EC) treatment for the elimination of arsenite. A sensitive quantitative response was obtained in the determination of As³⁺ in a secondary effluent from a wastewater treatment plant from Santiago (Chile). The preconcentration stage was optimized through a Central Composite Face design, and the most sensitive peak current was obtained at 200 s and -600 mV of time and accumulation potential, respectively, after a differential pulse voltammetry sweep. Electroanalytical determination was possible in an interval between 42.89 and 170.00 μg L^-1 with a detection limit of 0.39 μg L^-1, obtaining recoveries over 99.1%. The developed method was successfully applied in an electrocoagulation treatment to remove 250 μg L^-1 of arsenite from a polluted effluent in a batch system. Complete arsenite removal was achieved using a steel EC system with a current density of 6.0 mA cm^-2 in less than 3 min of treatment.

Organoids in lung cancer: A teenager with infinite growth potential

Despite the rapid advancement in lung cancer research, morbidity and mortality remain high in recent years. Therefore, deeper learning of the underlying molecular mechanisms of pathogenesis and discovery of novel effective therapeutic strategies of treatment in lung cancer research are around the corner. Among these, applying an efficient and reliable preclinical model would be a critical step that exists throughout the whole process. Traditional 2D models used in lung cancer research, including lung cancer cell lines and cell-derived xenograft models, cannot recapitulate the situations of patients due to the lack of a tumor microenvironment or tumor heterogeneity. Organoids, newly developed 3D in vitro structures, more comprehensively imitate the architecture, interaction and genetics of human organs. Cancer organoids, especially those derived from individual patients, can better resemble primary tumor tissues and thus have a greater potential for making breakthroughs in future cancer studies. Here, we mainly review recent advances in the methodologies and applications of lung cancer organoids, which are just developing but have huge potential.

Lung toxicity of particulates and gaseous pollutants using ex-vivo airway epithelial cell culture systems

Air pollution consists of a multi-faceted mix of gases and ambient particulate matter (PM) with diverse organic and non-organic chemical components that contribute to increasing morbidity and mortality worldwide. In particular, epidemiological and clinical studies indicate that respiratory health is adversely affected by exposure to air pollution by both causing and worsening (exacerbating) diseases such as chronic obstructive pulmonary disease (COPD), asthma, interstitial pulmonary fibrosis and lung cancer. The molecular mechanisms of air pollution-induced pulmonary toxicity have been evaluated with regards to different types of PM of various sizes and concentrations with single and multiple exposures over different time periods. These data provide a plausible interrelationship between cellular toxicity and the activation of multiple biological processes including proinflammatory responses, oxidative stress, mitochondrial oxidative damage, autophagy, apoptosis, cell genotoxicity, cellular senescence and epithelial-mesenchymal transition. However, these molecular changes have been studied predominantly in cell lines rather than in primary bronchial or nasal cells from healthy subjects or those isolated from patients with airways disease. In addition, they have been conducted under different cell culture conditions and generally in submerged culture rather than the more relevant air-liquid interface culture and with a variety of air pollutant exposure protocols. Cell types may respond differentially to pollution delivered as an aerosol rather than being bathed in media containing agglomerations of particles. As a result, the actual pathophysiological pathways activated by different PMs in primary cells from the airways of healthy and asthmatic subjects remains unclear. This review summarises the literature on the different methodologies utilised in studying the impact of submicron-sized pollutants on cells derived from the respiratory tract with an emphasis on data obtained from primary human cell. We highlight the critical underlying molecular mechanisms that may be important in driving disease processes in response to air pollution in vivo.

Construction and Application of in vitro Alveolar Models Based on 3D Printing Technology

Increasing lung diseases, mutating coronaviruses, and the development of new compounds urgently require biomimetic in vitro lung models for lung pathology, toxicology, and pharmacology. The current construction strategies for lung models mainly include animal models, 2D cell culture, lung-on-a-chip, and lung organoids. However, current models face difficulties in reproducing in vivo-like alveolar size and vesicle-like structures, and are unable to contain multiple cell types. In this study, a strategy for constructing alveolar models based on degradable hydrogel microspheres is proposed. Hydrogel microspheres, 200–250 µm in diameter, were prepared using a self-developed printing technique driven by alternating viscous and inertial forces. Microcapsules were further constructed using a coacervation-based layer-by-layer technique and core liquefaction. Three types of cells were inoculated and co-cultured on hydrogel capsules based on optimized microcapsule surface treatment strategies. Finally, an in vitro three-dimensional endothelial alveolar model with a multicellular composition and vesicle-like structure with a diameter of approximately 230 µm was successfully constructed. Cells in the constructed alveolar model maintained a high survival rate. The LD₅₀ values of glutaraldehyde based on the constructed models were in good agreement with the reference values, validating the potential of the model for future toxicant and drug detection.

Elastin in healthy and diseased lung

Elastic fibers are an essential part of the pulmonary extracellular matrix (ECM). Intact elastin is required for normal function and its damage contributes profoundly to the etiology and pathology of lung disease. This highlights the need for novel lung-specific imaging methodology that enables high-resolution 3D visualization of the ECM. We consider elastin's involvement in chronic respiratory disease and examine recent methods for imaging and modeling of the lung in the context of advances in lung tissue engineering for research and clinical application.

Physiological and Disease Models of Respiratory System Based on Organ-on-a-Chip Technology

The pathogenesis of respiratory diseases is complex, and its occurrence and development also involve a series of pathological processes. The present research methods are have difficulty simulating the natural developing state of the disease in the body, and the results cannot reflect the real growth state and function in vivo. The development of microfluidic chip technology provides a technical platform for better research on respiratory diseases. The size of its microchannel can be similar to the space for cell growth in vivo. In addition, organ-on-a-chip can achieve long-term co-cultivation of multiple cells and produce precisely controllable fluid shear force, periodically changing mechanical force, and perfusate with varying solute concentration gradient. To sum up, the chip can be used to analyze the specific pathophysiological changes of organs meticulously, and it is widely used in scientific research on respiratory diseases. The focus of this review is to describe and discuss current studies of artificial respiratory systems based on organ-on-a-chip technology and to summarize their applications in the real world.

A facile approach to synthesize CdS-attapulgite as a photocatalyst for reduction reactions in water

At room temperature, a facile approach has been utilized for preparing novel CdS–attapulgite (CdS–ATP) composites and the composites were applied in photocatalytic reduction of p-nitrophenol and Cr(vi). The effect of ATP on the photocatalytic activity of the CdS–ATP composites were studied by controlling the mass ratio of attapulgite. The results showed that the CdS–20%ATP composite has an excellent photocatalytic activity. In order to figure out the key to improve the photocatalytic efficiency, the prepared composites were characterized by Brunauer–Emmett–Teller (BET) specific surface area, UV-vis diffuse reflectance spectroscopy (DRS) and electrochemical impedance spectroscopy (EIS). The superior photocatalytic performance of the CdS–20%ATP composite can be ascribed to the existence of the ATP which can fix the CdS and prevent agglomeration. The interaction between ATP and CdS in the composites facilitates the electron transfer and also promoted their photocatalytic performance. This work provides us with some significant guidance in the development of CdS–ATP composite photocatalysts.

The application of CdS–attapulgite composites in photocatalytic reduction of p-nitrophenol and Cr(vi) demonstrated that the attapulgite could overcome the limitations of CdS.

In situ SERS detection of quinolone antibiotic residues in a water environment based on optofluidic in-fiber integrated Ag nanoparticles

In this paper, we present a microstructured optofluidic in-fiber Raman sensor for the detection of quinolone antibiotic residue in a water environment based on Ag surface-enhanced Raman scattering (SERS) substrate grown on the surface of the suspended core of micro-hollow optical fiber (MHF). Here, MHF has a special structure with a suspended core and a microchannel inside, which can become a natural in-fiber optofluidic device. Meanwhile, the self-assembled Ag SERS substrate can be grown on the suspended core's surface through chemical bonds, forming a microstructured optofluidic device with a Raman enhancement effect. Therefore, it can effectively detect the Raman signal of unlabeled trace quinolone antibiotic residue (ciprofloxacin and norfloxacin) inside the optical fiber. The results show that the ciprofloxacin and norfloxacin detection limits (LOD) are 10^-10M and 10^-11M, respectively. Compared with the maximum residue limit (3.01×10^-7mol/L) stipulated by the European Union, the results are much lower, and an ideal quantitative relationship can be obtained within the detection range. Significantly, this study provides an in-fiber microstructured optofluidic Raman sensor for the label-free detection of quinolone antibiotic residue, which will have good development prospects in the field of antibiotic water pollution environmental detection.

Environmental Toxicology Assays Using Organ-on-Chip

Adverse effects of environmental toxicants to human health have traditionally been assayed using in vitro assays. Organ-on-chip (OOC) is a new platform that can bridge the gaps between in vitro assays (or 3D cell culture) and animal tests. Microenvironments, physical and biochemical stimuli, and adequate sensing and biosensing systems can be integrated into OOC devices to better recapitulate the in vivo tissue and organ behavior and metabolism. While OOCs have extensively been studied for drug toxicity screening, their implementation in environmental toxicology assays is minimal and has limitations. In this review, recent attempts of environmental toxicology assays using OOCs, including multiple-organs-on-chip, are summarized and compared with OOC-based drug toxicity screening. Requirements for further improvements are identified and potential solutions are suggested.

Comprehensive Development in Organ-On-A-Chip Technology

The expeditious advancement in the organ on chip technology provided a phase change to the conventional in vitro tests used to evaluate absorption, distribution, metabolism, excretion (ADME) studies and toxicity assessments. The demand for an accurate predictive model for assessing toxicity and reducing the potential risk factors became the prime area of any drug delivery process. Researchers around the globe are welcoming the incorporation of organ-on-a-chips for ADME and toxicity evaluation. Organ-on-a-chip (OOC) is an interdisciplinary technology that evolved as a contemporary in vitro model for the pharmacokinetics and pharmacodynamics (PK-PD) studies of a proposed drug candidate in the pre-clinical phases of drug development. The OOC provides a platform that mimics the physiological functions occurring in the human body. The precise flow control systems and the rapid sample processing makes OOC more advanced than the conventional two-dimensional (2D) culture systems. The integration of various organs as in the multi organs-on-a-chip provides more significant ideas about the time and dose dependant effects occurring in the body when a new drug molecule is administered as part of the pre-clinical times. This review outlines the comprehensive development in the organ-on-a-chip technology, various OOC models and its drug development applications, toxicity evaluation and efficacy studies.

Advances in removing mass transport limitations for more physiologically relevant in vitro 3D cell constructs

Spheroids and organoids are promising models for biomedical applications ranging from human disease modeling to drug discovery. A main goal of these 3D cell-based platforms is to recapitulate important physiological parameters of their in vivo organ counterparts. One way to achieve improved biomimetic architectures and functions is to culture cells at higher density and larger total numbers. However, poor nutrient and waste transport lead to low stability, survival, and functionality over extended periods of time, presenting outstanding challenges in this field. Fortunately, important improvements in culture strategies have enhanced the survival and function of cells within engineered microtissues/organs. Here, we first discuss the challenges of growing large spheroids/organoids with a focus on mass transport limitations, then highlight recent tools and methodologies that are available for producing and sustaining functional 3D in vitro models. This information points toward the fact that there is a critical need for the continued development of novel cell culture strategies that address mass transport in a physiologically relevant human setting to generate long-lasting and large-sized spheroids/organoids.

Covalent organic frameworks as robust materials for mitigation of environmental pollutants

Today, one of the main leading global problems is the presence of different pollutants in the environment. These pollutants not only affect human health but also overshadow the life of other creatures. Thus, pollutant treatment has become a challenging issue among the researchers and the scientific community. Different adsorbents and catalysts have been applied to the removal of pollutants. However, the associated limitations like poor chemical and physical stability, low surface area and low binding capacity revived researchers' attention to exploring alternative materials. Covalent organic frameworks (COFs) are versatile materials created based on the strong covalent interactions between blocked monomers. Unique features, including high specific surface area, high chemical-physical stability and crystallinity render COFs an intriguing sorbent and catalyst in treating pollutants. This review spotlights the applications of COFs as distinguished adsorbents to remove hazardous pollutants from the environment. At first, COFs and their properties as alternative materials were introduced. Then, different synthesis approaches of COFs and their advantages and disadvantages were discussed. Furthermore, the applications of COFs outlined to remove a wide variety of pollutants based on adsorption and degradation. Finally, the prospects of COFs for the treatment of pollutants were evaluated.

Advances in Micro/Nanoporous Membranes for Biomedical Engineering

Porous membrane materials at the micro/nanoscale have exhibited practical and potential value for extensive biological and medical applications associated with filtration and isolation, cell separation and sorting, micro-arrangement, in-vitro tissue reconstruction, high-throughput manipulation and analysis, and real-time sensing. Herein, an overview of technological development of micro/nanoporous membranes (M/N-PMs) is provided. Various membrane types and the progress documented in membrane fabrication techniques, including the electrochemical-etching, laser-based technology, microcontact printing, electron beam lithography, imprinting, capillary force lithography, spin coating, and microfluidic molding are described. Their key features, achievements, and limitations associated with micro/nanoporous membrane (M/N-PM) preparation are discussed. The recently popularized applications of M/N-PMs in biomedical engineering involving the separation of cells and biomolecules, bioparticle operations, biomimicking, micropatterning, bioassay, and biosensing are explored too. Finally, the challenges that need to be overcome for M/N-PM fabrication and future applications are highlighted.

Biomimetic Human Disease Model of SARS-CoV-2-Induced Lung Injury and Immune Responses on Organ Chip System

Coronavirus disease 2019 (COVID-19) is a global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The models that can accurately resemble human-relevant responses to viral infection are lacking. Here, a biomimetic human disease model on chip that allows to recapitulate lung injury and immune responses induced by SARS-CoV-2 in vitro at organ level is created. This human alveolar chip reproduce the key features of alveolar-capillary barrier by coculture of human alveolar epithelium, microvascular endothelium, and circulating immune cells under fluidic flow in normal and disease. Upon SARS-CoV-2 infection, the epithelium exhibits higher susceptibility to virus than endothelium. Transcriptional analyses show activated innate immune responses in epithelium and cytokine-dependent pathways in endothelium at day 3 post-infection, revealing the distinctive responses in different cell types. Notably, viral infection causes the immune cell recruitment, endothelium detachment, and increased inflammatory cytokines release, suggesting the crucial role of immune cells involved in alveolar barrier injury and exacerbated inflammation. Treatment with remdesivir can inhibit viral replication and alleviate barrier disruption on chip. This organ chip model can closely mirror human-relevant responses to SARS-CoV-2 infection, which is difficult to be achieved by in vitro models, providing a unique platform for COVID-19 research and drug development.

Environmental toxicology wars: Organ-on-a-chip for assessing the toxicity of environmental pollutants

Environmental pollution is a widespread problem, which has seriously threatened human health and led to an increase of human diseases. Therefore, it is critical to evaluate environmental pollutants quickly and efficiently. Because of obvious inter-species differences between animals and humans, and lack of physiologically-relevant microenvironment, animal models and in vitro two-dimensional (2D) models can not accurately describe toxicological effects and predicting actual in vivo responses. To make up the limitations of conventional environmental toxicology screening, organ-on-a-chip (OOC) systems are increasingly developing. OOC systems can provide a well-organized architecture with comparable to the complex microenvironment in vivo and generate realistic responses to environmental pollutants. The feasibility, adjustability and reliability of OCC systems make it possible to offer new opportunities for environmental pollutants screening, which can study their metabolism, collective response, and fate in vivo. Further progress can address the challenges to make OCC systems better investigate and evaluate environmental pollutants with high predictive power.