Advances of microfluidic lung chips for assessing atmospheric pollutants exposure

In vitro models to study viral-induced asthma exacerbation: a short review for a key issue

Asthma is a heterogenous inflammatory bronchial disease involving complex mechanisms, several inflammatory pathways, and multiples cell-type networks. Bronchial inflammation associated to asthma is consecutive to multiple aggressions on epithelium, such as microbiologic, pollutant, and antigenic agents, which are responsible for both T2 and non-T2 inflammatory responses and further airway remodeling. Because asthma physiopathology involves multiple crosstalk between several cell types from different origins (epithelial, mesenchymal, and immune cells) and numerous cellular effectors, no single and/or representative in vitro model is suitable to study the overall of this disease. In this short review, we present and discuss the advantages and limitations of different in vitro models to decipher different aspects of virus-related asthma physiopathology and exacerbation.

Revealing transport, uptake and damage of polystyrene microplastics using a gut-liver-on-a-chip

Microplastics (MPs) are pervasive pollutants present in various environments. They have the capability to infiltrate the human gastrointestinal tract through avenues like water and food, and ultimately accumulating within the liver. However, due to the absence of reliable platforms, the transportation, uptake, and damage of microplastics in the gut-liver axis remain unclear. Here, we present the development of a gut-liver-on-a-chip (GLOC) featuring biomimetic intestinal peristalsis and a dynamic hepatic flow environment, exploring the translocation in the intestines and accumulation in the liver of MPs following oral ingestion. In comparison to conventional co-culture platforms, this chip has the capability to mimic essential physical microenvironments found within the intestines and liver (e.g., intestinal peristalsis and liver blood flow). It effectively reproduces the physiological characteristics of the intestine and liver (e.g., intestinal barrier and liver metabolism). Moreover, we infused polyethylene MPs with a diameter of 100 nm into the intestinal and hepatic chambers (concentrations ranging from 0 to 1 mg mL-1). We observed that as intestinal peristalsis increased (0%, 1%, 3%, 5%), the transport rate of MPs decreased, while the levels of oxidative stress and damage in hepatic cells decreased correspondingly. Our GLOC elucidates the process of MP transport in the intestine and uptake in the liver following oral ingestion. It underscores the critical role of intestinal peristalsis in protecting the liver from damage, and provides a novel research platform for assessing the organ-specific effects of MPs.

Lung-on-a-chip: From design principles to disease applications

To address the growing need for accurate lung models, particularly in light of respiratory diseases, lung cancer, and the COVID-19 pandemic, lung-on-a-chip technology is emerging as a powerful alternative. Lung-on-a-chip devices utilize microfluidics to create three-dimensional models that closely mimic key physiological features of the human lung, such as the air-liquid interface, mechanical forces associated with respiration, and fluid dynamics. This review provides a comprehensive overview of the fundamental components of lung-on-a-chip systems, the diverse fabrication methods used to construct these complex models, and a summary of their wide range of applications in disease modeling and aerosol deposition studies. Despite existing challenges, lung-on-a-chip models hold immense potential for advancing personalized medicine, drug development, and disease prevention, offering a transformative approach to respiratory health research.

Engineering organoids-on-chips for drug testing and evaluation

Organoids-on-chips is an emerging innovative integration of stem cell-derived organoids with advanced organ-on-chip technology, providing a novel platform for the in vitro construction of biomimetic micro-physiological systems. The synergistic merger transcends the limitations of traditional drug screening and safety assessment methodologies, such as 2D cell cultures and animal models. In this review, we examine the prevailing challenges and prerequisites of preclinical models utilized for drug screening and safety evaluations. We highlighted the salient features and merits of organoids-on-chip, elucidating their capability to authentically replicate human physiology, thereby addressing contemporary impediments. We comprehensively overviewed the recent endeavors where organoids-on-chips have been harnessed for drug screening and safety assessment and delved into potential opportunities and challenges for evolving sophisticated, near-physiological organoids-on-chips. Based on current achievements, we further discuss how to enhance the practicality of organoids-on-chips and accelerate the translation from preclinical to clinical stages in healthcare and industry by utilizing multidisciplinary convergent innovation.

“Lung-on-a-chip” as an instrument for studying the pathophysiology of human respiration

“Lung-on-a-chip” (LoC) is a microfluidic device, imitating the gas-fluid interface of the pulmonary alveole in the human lung and intended for pathophysiological, pharmacological and molecular-biological studies of the air-blood barrier in vitro. The LoC device itself contains a system of fluid and gas microchannels, separated with a semipermeable elastic membrane, containing a polymer base and the alveolar cell elements. Depending on the type of LoC (single-, double- and three-channel), the membrane may contain only alveolocytes or alveolocytes combined with other cells — endotheliocytes, fibroblasts, alveolar macrophages or tumor cells. Some LoC models also include proteinic or hydrogel stroma, imitating the pulmonary interstitium. The first double-channel LoC variant, in which one side of the membrane contained an alveolocytic monolayer and the other side — a monolayer of endotheliocytes, was developed in 2010 by a group of scientists from the Harvard University for maximally precise in vitro reproduction of the micro-environment and biomechanics operations of the alveoli. Modern LoC modifications include the same elements and differ only by the construction of the microfluidic system, by the biomaterial of semipermeable membrane, by the composition of cellular and stromal elements and by specific tasks to be solved. Besides the LoC imitating the hematoalveolar barrier, there are modifications for studying the specific pathophysiological processes, for the screening of medicinal products, for modeling specific diseases, for example, lung cancer, chronic obstructive pulmonary disease or asthma. In the present review, we have analyzed the existing types of LoC, the biomaterials used, the methods of detecting molecular processes within the microfluidic devices and the main directions of research to be conducted using the “lung-on-a-chip”.

Comprehensive analysis of resilience of human airway epithelial barrier against short-term PM2.5 inorganic dust exposure using in vitro microfluidic chip and ex vivo human airway models

BACKGROUND AND OBJECTIVE

The updated World Health Organization (WHO) air quality guideline recommends an annual mean concentration of fine particulate matter (PM2.5) not exceeding 5 or 15 μg/m3 in the short-term (24 h) for no more than 3-4 days annually. However, more than 90% of the global population is currently exposed to daily concentrations surpassing these limits, especially during extreme weather conditions and due to transboundary dust transport influenced by climate change. Herein, the effect of respirable

METHODS

Silica particles at an average size of 1 μm, referred to as

RESULTS

In the AEB-on-a-chip platform, short-term exposure to 800 μg/mL PM2.5 disrupted AEB integrity via increasing barrier permeability, decreasing cell adhesion-barrier markers such as ZO-1, Vinculin, ACE2, and CD31, impaired cell viability and increased the expression levels of proinflammatory markers; IFNs, IL-6, IL-1s, TNF-α, CD68, CD80, and Inos, mostly under dynamic conditions. Besides, decreased tissue viability, impaired tissue integrity via decreasing of Vinculin, ACE2, β-catenin, and E-cadherin, and also proinflammatory response with elevated CD68, IL-1α, IL-6, IFN-Ɣ, Inos, and CD80 markers, were observed after PM2.5 exposure in ex vivo tissue.

CONCLUSION

The duration and concentration of PM2.5 that can be exposed during extreme weather conditions and natural events aligns with our exposure model (0-800 μg/mL 72 h). At this level of exposure, the resilience of the epithelial barrier is demonstrated by both AEB-on-a-chip platform emulating dynamic forces in the body and ex vivo bronchial biopsy slices. Lung-on-a-chip models will serve as reliable exposure models in this context.

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Key Words

• PM2.5
• airway epithelial barrier
• microfluidic systems
• particulate matter
• silica particles

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MESH Headings

• Humans
• Particulate Matter/analysis
• Epithelial Cells/metabolism
• Dust
• Respiratory Mucosa/metabolism
• Lab-On-A-Chip Devices
• Cell Line

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Grants

• 2019K12-149080 Presidency of the Republic of Turkey Strategy and Budget Department
• 1139B412102522 Scientific and Technological Research Council of Turkey (TUBITAK)

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Affiliation(s)

Ozlem Goksel Department of Pulmonary Medicine, Division of Immunology and Allergy, Laboratory of Occupational & Environmental Respiratory Diseases and Asthma, Faculty of Medicine, Ege University, Izmir, Turkey Translational Pulmonary Research Center (EgeSAM), Ege University, Izmir, Turkey
Meryem Irem Sipahi Department of Biotechnology and Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark
Sena Yanasik Department of Bioengineering, Faculty of Engineering, Ege University, Izmir, Turkey
Pelin Saglam-Metiner Translational Pulmonary Research Center (EgeSAM), Ege University, Izmir, Turkey Department of Bioengineering, Faculty of Engineering, Ege University, Izmir, Turkey
Sema Benzer Department of Bioengineering, Faculty of Engineering, Ege University, Izmir, Turkey
Leila Sabour-Takanlou Department of Medical Biology, Faculty of Medicine, Ege University, Izmir, Turkey
Maryam Sabour-Takanlou Department of Medical Biology, Faculty of Medicine, Ege University, Izmir, Turkey
Cigir Biray-Avci Department of Medical Biology, Faculty of Medicine, Ege University, Izmir, Turkey
Ozlem Yesil-Celiktas Translational Pulmonary Research Center (EgeSAM), Ege University, Izmir, Turkey Department of Bioengineering, Faculty of Engineering, Ege University, Izmir, Turkey METU MEMS Center, Ankara, Turkey

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Establishment and evaluation of on-chip intestinal barrier biosystems based on microfluidic techniques

As a booming engineering technology, the microfluidic chip has been widely applied for replicating the complexity of human intestinal micro-physiological ecosystems in vitro. Biosensors, 3D imaging, and multi-omics have been applied to engineer more sophisticated intestinal barrier-on-chip platforms, allowing the improved monitoring of physiological processes and enhancing chip performance. In this review, we report cutting-edge advances in the microfluidic techniques applied for the establishment and evaluation of intestinal barrier platforms. We discuss different design principles and microfabrication strategies for the establishment of microfluidic gut barrier models in vitro. Further, we comprehensively cover the complex cell types (e.g., epithelium, intestinal organoids, endothelium, microbes, and immune cells) and controllable extracellular microenvironment parameters (e.g., oxygen gradient, peristalsis, bioflow, and gut-organ axis) used to recapitulate the main structural and functional complexity of gut barriers. We also present the current multidisciplinary technologies and indicators used for evaluating the morphological structure and barrier integrity of established gut barrier models in vitro. Finally, we highlight the challenges and future perspectives for accelerating the broader applications of these platforms in disease simulation, drug development, and personalized medicine. Hence, this review provides a comprehensive guide for the development and evaluation of microfluidic-based gut barrier platforms.

A miniaturized multicellular platform to mimic the 3D structure of the alveolar-capillary barrier

Several diseases affect the alveoli, and the efficacy of medical treatments and pharmaceutical therapies is hampered by the lack of pre-clinical models able to recreate in vitro the diseases. Microfluidic devices, mimicking the key structural and compositional features of the alveoli, offer several advantages to medium and high-throughput analysis of new candidate therapies. Here, we developed an alveolus-on-a-chip recapitulating the microanatomy of the physiological tissue by including the epithelium, the fibrous interstitial layer and the capillary endothelium. A PDMS device was obtained assembling a top layer and a bottom layer obtained by replica molding. A polycaprolactone/gelatin (PCL-Gel) electrospun membrane was included within the two layers supporting the seeding of 3 cell phenotypes. Epithelial cells were grown on a fibroblast-laden collagen hydrogel located on the top side of the PCL-Gel mats while endothelial cells were seeded on the basolateral side of the membrane. The innovative design of the microfluidic device allows to replicate both cell-cell and cell-extracellular matrix interactions according to the in vivo cell arrangement along with the establishment of physiologically relevant air-liquid interface conditions. Indeed, high cell viability was confirmed for up to 10 days and the formation of a tight endothelial and epithelial barrier was assessed by immunofluorescence assays.

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.

How to use an in vitro approach to characterize the toxicity of airborne compounds

As part of the development of new approach methodologies (NAMs), numerous in vitro methods are being developed to characterize the potential toxicity of inhalable xenobiotics (gases, volatile organic compounds, polycyclic aromatic hydrocarbons, particulate matter, nanoparticles). However, the materials and methods employed are extremely diverse, and no single method is currently in use. Method standardization and validation would raise trust in the results and enable them to be compared. This four-part review lists and compares biological models and exposure methodologies before describing measurable biomarkers of exposure or effect. The first section emphasizes the importance of developing alternative methods to reduce, if not replace, animal testing (3R principle). The biological models presented are mostly to cultures of epithelial cells from the respiratory system, as the lungs are the first organ to come into contact with air pollutants. Monocultures or cocultures of primary cells or cell lines, as well as 3D organotypic cultures such as organoids, spheroids and reconstituted tissues, but also the organ(s) model on a chip are examples. The exposure methods for these biological models applicable to airborne compounds are submerged, intermittent, continuous either static or dynamic. Finally, within the restrictions of these models (i.e. relative tiny quantities, adhering cells), the mechanisms of toxicity and the phenotypic markers most commonly examined in models exposed at the air-liquid interface (ALI) are outlined.

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.

Recent Progress in Micro- and Nanotechnology-Enabled Sensors for Biomedical and Environmental Challenges

Micro- and nanotechnology-enabled sensors have made remarkable advancements in the fields of biomedicine and the environment, enabling the sensitive and selective detection and quantification of diverse analytes. In biomedicine, these sensors have facilitated disease diagnosis, drug discovery, and point-of-care devices. In environmental monitoring, they have played a crucial role in assessing air, water, and soil quality, as well as ensured food safety. Despite notable progress, numerous challenges persist. This review article addresses recent developments in micro- and nanotechnology-enabled sensors for biomedical and environmental challenges, focusing on enhancing basic sensing techniques through micro/nanotechnology. Additionally, it explores the applications of these sensors in addressing current challenges in both biomedical and environmental domains. The article concludes by emphasizing the need for further research to expand the detection capabilities of sensors/devices, enhance sensitivity and selectivity, integrate wireless communication and energy-harvesting technologies, and optimize sample preparation, material selection, and automated components for sensor design, fabrication, and characterization.

Flow Characteristics and Switching Mechanism of Bistable Slit Flow Actuated by Temperature

The bistable flow is attractive as it can be analogous to a switch to realize flow control. Based on the previous studies on actuation technique, the present study first proposed temperature-driven switching of bistable slit flow. A two-dimensional numerical simulation was conducted to investigate the flow deflection characteristics and switching mechanism. It was concluded that the temperature gradient not only biases the slit flow but also locks it to the high-temperature side. The flow deflection angle became larger with the increase in temperature gradient. Being driven by the temperature, the flow can be switched from one side to the other. Furthermore, the fluid viscosity, which varies with temperature, determines the degree of flow deflection and the entire switching time. This research can enrich the active regulation of flow and has significant potential applications in thermal sensors, thermal detectors, microelectromechanical systems, biomedicine, and other equivalent fields.