Human gut-on-a-chip inhabited by microbial flora that experiences intestinal peristalsis-like motions and flow

Interfacial engineering for biomolecule immobilisation in microfluidic devices

Microfluidic devices are used for various applications in biology and medicine. From on-chip modelling of human organs for drug screening and fast and straightforward point-of-care (POC) detection of diseases to sensitive biochemical analysis, these devices can be custom-engineered using low-cost techniques. The microchannel interface is essential for these applications, as it is the interface of immobilised biomolecules that promote cell capture, attachment and proliferation, sense analytes and metabolites or provide enzymatic reaction readouts. However, common microfluidic materials do not facilitate the stable immobilisation of biomolecules required for relevant applications, making interfacial engineering necessary to attach biomolecules to the microfluidic surfaces. Interfacial engineering is performed through various immobilisation mechanisms and surface treatment techniques, which suitably modify the surface properties like chemistry and energy to obtain robust biomolecule immobilisation and long-term storage stability suitable for the final application. In this review, we provide an overview of the status of interfacial engineering in microfluidic devices, covering applications, the role of biomolecules, their immobilisation pathways and the influence of microfluidic materials. We then propose treatment techniques to optimise performance for various biological and medical applications and highlight future areas of development.

StretchView - A Multi-Axial Cell-Stretching Device for Long-Term Automated Videomicroscopy of Living Cells

Incorporating mechanical stretching of cells in tissue culture is crucial for mimicking (patho)-physiological conditions and understanding the mechanobiological responses of cells, which can have significant implications in areas like tissue engineering and regenerative medicine. Despite the growing interest, most available cell-stretching devices are not compatible with automated live-cell imaging, indispensable for characterizing alterations in the dynamics of various important cellular processes. In this work, StretchView is presented, a multi-axial cell-stretching platform compatible with automated, time-resolved live-cell imaging. Using StretchView, long-term image acquisition of cells in the relaxed and stretched states is shown for the first time (experimental time of 12 h) without the need for human intervention. Homogeneous and stable strain fields are demonstrated for 18 h of cyclic stretching, highlighting the platform's versatility and robustness. As proof-of-principle, the effect of stretching on cell kinematics and spatiotemporal localization of the cell-cell adhesion protein E-cadherin is examined for MDCK cells in monolayer. First evidence of a monotonic increase in junctional E-cadherin localization upon exposure to stretch is presented using live-cell imaging data acquired during cyclic stretching, suggestive of an increase in barrier integrity of the monolayer. These findings highlight the potential of StretchView in providing insights into cell mechanobiology and beyond.

Microfluidic organ-on-a-chip models for the gut-liver axis: from structural mimicry to functional insights

The gut-liver axis plays a crucial role in maintaining metabolic balance and overall human health. It orchestrates various processes, such as blood flow, nutrient transfer, metabolite processing, and immune cell communication between the two organs. Traditional methods, such as animal models and two-dimensional (2D) cell cultures, are insufficient in fully replicating the intricate functions of the gut-liver axis. The emergence of microfluidic technology has revolutionized this field, facilitating the development of organ-on-a-chip (OOC) systems. These systems are capable of mimicking the complex structures and dynamic environments of the gut and liver in vitro and incorporating sensors for real-time monitoring. In this article, we review the latest progress in gut-on-a-chip (GOC) and liver-on-a-chip (LOC) systems, as well as the integrated gut-liver-on-a-chip (GLOC) models. Our focus lies in the simulation of physiological parameters, three-dimensional (3D) structural mimicry, microbiome integration, and multicellular co-culture. All these aspects are essential for constructing accurate in vitro models of the gut and liver. Furthermore, we explore the current applications of OOC technology in the study of the gut and liver, including its use in disease modeling, toxicity testing, and drug screening. Finally, we discuss the challenges that remain and outline potential future directions for advancing GOC and LOC development in vitro.

Sensor-integrated gut-on-a-chip for monitoring senescence-mediated changes in the intestinal barrier

The incidence of inflammatory bowel disease among the elderly has significantly risen in recent years, posing a growing socioeconomic burden to aging societies. Moreover, non-gastrointestinal diseases, also prevalent in this demographic, have been linked to intestinal barrier dysfunction, thus highlighting the importance of investigating aged-mediated changes within the human gut. While gastrointestinal pathology often involves an impaired gut barrier, the impact of aging on the human gastrointestinal barrier function remains unclear. To explore the effect of senescence, a key hallmark of aging, on gut barrier integrity, we established and evaluated an in vitro gut-on-a-chip model tailored to investigate barrier changes by the integration of an impedance sensor. Here, a microfluidic gut-on-a-chip system containing integrated membrane-based electrode microarrays is used to non-invasively monitor epithelial barrier formation and senescence-mediated changes in barrier integrity upon treating Caco-2 cells with 0.8 μg mL-1 doxorubicin (DXR), a chemotherapeutic which induces cell cycle arrest. Results of our microfluidic human gut model reveal a DXR-mediated increase in impedance and cell hypertrophy as well as overexpression of p21, and CCL2, indicative of a senescent phenotype. Combined with the integrated electrodes, monitoring ∼57% of the cultivation area in situ and non-invasively, the developed chip-based senescent-gut model is ideally suited to study age-related malfunctions in barrier integrity.

Advances in modeling periodontal host-microbe interactions: insights from organotypic and organ-on-chip systems

Periodontal disease, a chronic inflammatory condition affecting the supporting structures of teeth, is driven by an imbalanced interaction between the periodontal microbiota and the host inflammatory response. Beyond its local impact, periodontal disease is associated with systemic conditions such as diabetes mellitus, cardiovascular disease, and inflammatory bowel disease, emphasizing the importance of understanding its mechanisms. Traditional pre-clinical models, such as monolayer cultures and animal studies, have provided foundational insights but are limited by their physiological relevance and ethical concerns. Recent advancements in tissue engineering and microfluidic technologies have led to the development of three-dimensional (3D) organotypic culture models and organ-on-chip systems that more closely mimic native tissue microenvironments. This review provides an overview of the evolution of methods to study periodontal host-microbe interactions, from simple 2D monolayer cultures to complex 3D organotypic and microfluidic organ-on-chip (OoC) models. We discuss various fabrication strategies, host-microbe co-culture techniques, and methods for evaluating outcomes in these advanced models. Additionally, we highlight insights gained from gut-on-chip platforms and their potential applications in periodontal research and understanding oral-systemic links of periodontal disease. Through a comprehensive overview of current advancements and future directions, this review provides insights on the transformative potential of OoC technology in periodontal research, offering new avenues for studying disease mechanisms and developing therapeutic strategies.

Coculture systems to study interactions between anaerobic bacteria and intestinal epithelium

Coculture systems (CCSs) are experimental tools used to study the interactions of anaerobic bacteria among themselves and the gut epithelial cells under conditions simulating the human gut, unlike those in animal models. Although the studies on animal models are useful in determining the relationship between the causative agents of infections and human infections, they have disadvantages, such as ethical issues, in addition to the differences in the microbiota of the animal and humans. Therefore, the results obtained using animal models cannot be directly extrapolated to humans. CCSs can more completely reflect in vivo gut homeostasis and contribute to better understanding of the interplay between the intestinal cells and anaerobes, prevalent among the gut bacteria. Moreover, they provide new insights on the pathogenesis of infections and aid in assessing the usefulness of new probiotics and antibacterials. Therefore, CCSs, including the gut-on-a-chip models, can significantly improve microbiota-based therapy. Moreover, they can also be used to detect microbiota-derived metabolites such as those with mutagenic properties. The aim of this review was to explore selected CCS models of anaerobes with intestinal epithelium and their application in investigating intestinal homeostasis. The focus was to highlight the application of different CCSs and important data obtained from their implementation.

Advances of dual-organ and multi-organ systems for gut, lung, skin and liver models in absorption and metabolism studies

Drug development is a costly and timely process with high risks of failure during clinical trials. Although in vitro tissue models have significantly advanced over the years, thus fostering a transition from animal-derived models towards human-derived models, failure rates still remain high. Current cell-based assays are still not able to provide an accurate prediction of the clinical success or failure of a drug candidate. To overcome the limitations of current methods, a variety of microfluidic systems have been developed as powerful tools that are capable of mimicking (micro)physiological conditions more closely by integrating physiological fluid flow conditions, mechanobiological cues and concentration gradients, to name only a few. One major advantage of these biochip-based tissue cultures, however, is their ability to seamlessly connect different organ models, thereby allowing the study of organ-crosstalk and metabolic byproduct effects. This is especially important when assessing absorption, distribution, metabolism, and excretion (ADME) processes of drug candidates, where an interplay between various organs is a prerequisite. In the current review, a number of in vitro models as well as microfluidic dual- and multi-organ systems are summarized with a focus on absorption (skin, lung, gut) and metabolism (liver). Additionally, the advantage of multi-organ chips in identifying a drug's on and off-target toxicity is discussed. Finally, the potential high-throughput implementation and modular chip design of multi-organ-on-a-chip systems within the pharmaceutical industry is highlighted, outlining the necessity of reducing handling complexity.

Applying 3D cultures and high-throughput technologies to study host-pathogen interactions

Recent advances in cell culturing and DNA sequencing have dramatically altered the field of human microbiome research. Three-dimensional (3D) cell culture is an important tool in cell biology, in cancer research, and for studying host-microbe interactions, as it mimics the in vivo characteristics of the host environment in an in vitro system, providing reliable and reproducible models. This work provides an overview of the main 3D culture techniques applied to study interactions between host cells and pathogenic microorganisms, how these systems can be integrated with high-throughput molecular methods, and how multi-species model systems may pave the way forward to pinpoint interactions among host, beneficial microbes and pathogens.

A gut-on-a-chip incorporating human faecal samples and peristalsis predicts responses to immune checkpoint inhibitors for melanoma

Patient responses to immune checkpoint inhibitors can be influenced by the gastrointestinal microbiome. Mouse models can be used to study microbiome-host crosstalk, yet their utility is constrained by substantial anatomical, functional, immunological and microbial differences between mice and humans. Here we show that a gut-on-a-chip system mimicking the architecture and functionality of the human intestine by including faecal microbiome and peristaltic-like movements recapitulates microbiome-host interactions and predicts responses to immune checkpoint inhibitors in patients with melanoma. The system is composed of a vascular channel seeded with human microvascular endothelial cells and an intestinal channel with intestinal organoids derived from human induced pluripotent stem cells, with the two channels separated by a collagen matrix. By incorporating faecal samples from patients with melanoma into the intestinal channel and by performing multiomic analyses, we uncovered epithelium-specific biomarkers and microbial factors that correlate with clinical outcomes in patients with melanoma and that the microbiome of non-responders has a reduced ability to buffer cellular stress and self-renew. The gut-on-a-chip model may help identify prognostic biomarkers and therapeutic targets.

Organ-on-a-Chip Applications in Microfluidic Platforms

Microfluidic technology plays a crucial role in organ-on-a-chip (OoC) systems by replicating human physiological processes and disease states, significantly advancing biomedical research and drug discovery. This article reviews the design and fabrication processes of microfluidic devices. It also explores how these technologies are integrated into OoC platforms to simulate human physiological environments, highlighting key principles, technological advances, and diverse applications. Through case studies involving the simulation of multiple organs such as the heart, liver, and lungs, the article evaluates the impact of OoC systems' integrated microfluidic technology on drug screening, toxicity assessment, and personalized medicine. In addition, this article considers technical challenges, ethical issues, and future directions, and looks ahead to further optimizing the functionality and biomimetic precision of OoCs through innovation, emphasizing its critical role in promoting personalized medicine and precision treatment strategies.

A pumpless microfluidic co-culture system to model the effects of shear flow on biological barriers

Biological barriers formed by the endothelium and epithelium regulate nutrient exchange, disease development, and drug delivery. Organ-on-chip (OOC) systems effectively model these barriers by incorporating key biophysical cues like microscale dimensions, co-culture, and fluid flow-induced shear stress. The majority of microfluidic OOC platforms, however, require syringe and pump systems which are hindered by several limitations, including large footprints, elaborate designs, long setup times, and a high rate of failure (contamination, leakage, etc.). Here we describe VitroFlo, a pump-free microfluidic device designed for in vitro biological barrier modeling with 12 independent co-culture modules that can be simultaneously subjected to tunable, unidirectional flow with physiological shear stresses ranging from 0.01-10 dyn/cm2. We demonstrate application of the device to model vascular endothelial, blood-brain, and intestinal epithelial barriers, and confirm shear stress-dependent cell alignment, tight junction protein expression, barrier maturation, permeability, and paracrine signaling between co-cultured cells. The VitroFlo platform enables scalable and cost-effective modeling of physiological barriers to facilitate the translation of findings from in vitro systems to preclinical models.

Human organoids and organ-on-chips in coeliac disease research

Coeliac disease (CeD) is an immune-mediated disorder characterised by gluten-triggered inflammation and damage in the small intestine, with lifelong gluten-free diet (GFD) as the only treatment. It is a multifactorial disease, involving genetic and environmental susceptibility factors, and its complexity and lack of comprehensive human model systems have hindered understanding of its pathogenesis and development of new treatments. Therefore, it is crucial to establish systems that recapitulate patient genetic background and the interactions between the small intestinal epithelial barrier, immune cells, and environment that contribute to CeD. In this review, we discuss disease complexity, recent advances in stem cell biology, organoids, tissue co-cultures, and organ-on-chip (OoC) systems that facilitate the development of comprehensive human model systems, and model applications in preclinical studies of potential treatments.

Biomaterial-assisted organoid technology for disease modeling and drug screening

Developing disease models and screening for effective drugs are key areas of modern medical research. Traditional methodologies frequently fall short in precisely replicating the intricate architecture of bodily tissues and organs. Nevertheless, recent advancements in biomaterial-assisted organoid technology have ushered in a paradigm shift in biomedical research. This innovative approach enables the cultivation of three-dimensional cellular structures in vitro that closely emulate the structural and functional attributes of organs, offering physiologically superior models compared to conventional techniques. The evolution of biomaterials plays a pivotal role in supporting the culture and development of organ tissues, thereby facilitating more accurate disease state modeling and the rigorous evaluation of drug efficacy and safety profiles. In this review, we will explore the roles that various biomaterials play in organoid development, examine the fundamental principles and advantages of utilizing these technologies in constructing disease models, and highlight recent advances and practical applications in drug screening using disease-specific organoid models. Additionally, the challenges and future directions of organoid technology are discussed. Through continued research and innovation, we aim to make remarkable strides in disease treatment and drug development, ultimately enhancing patient quality of life.

Recent Advances in Integrated Organ-Chip Sensing Toward Robust and User-Friendly Systems

Organs-on-a-chip (OOC) are an emergent technology that bridge the gap between current in vitro and in vivo models used to inform drug discovery and investigate disease pathophysiology. These systems offer improved bio-relevance and controlled complexity through the integration of physical and/or chemical stimuli matched to physiologically relevant conditions. Although significant advancements have been made toward recreating organ-specific physiology on chip, the methods available to study structure and function of the cell microenvironment are still limited. Established analysis approaches, including fluorescence microscopy, rely on laborious offline workflows that yield limited time-point data. As the OOC field continues to evolve, there is a unique opportunity to engineer improved characterization methods into organ-chip devices. This review provides an overview of current integrated sensing approaches that address current limitations and enable real-time readout of relevant physiological parameters in OOC.

A review on gut microbiota and miRNA crosstalk: implications for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive decline and progressive neuronal damage. Recent research has highlighted the significant roles of the gut microbiota and microRNAs (miRNAs) in the pathogenesis of AD. This review explores the intricate interaction between gut microbiota and miRNAs, emphasizing their combined impact on Alzheimer's progression. First, we discuss the bidirectional communication within the gut-brain axis and how gut dysbiosis contributes to neuroinflammation and neurodegeneration in AD. Changes in gut microbiota composition in Alzheimer's patients have been linked to inflammation, which exacerbates disease progression. Next, we delve into the biology of miRNAs, focusing on their roles in gene regulation, neurodevelopment, and neurodegeneration. Dysregulated miRNAs are implicated in AD pathogenesis, influencing key processes like inflammation, tau pathology, and amyloid deposition. We then examine how the gut microbiota modulates miRNA expression, particularly in the brain, potentially altering neuroinflammatory responses and synaptic plasticity. The interplay between gut microbiota and miRNAs also affects blood-brain barrier integrity, further contributing to Alzheimer's pathology. Lastly, we explore therapeutic strategies targeting this gut microbiota-miRNA axis, including probiotics, prebiotics, and dietary interventions, aiming to modulate miRNA expression and improve AD outcomes. While promising, challenges remain in fully elucidating these interactions and translating them into effective therapies. This review highlights the importance of understanding the gut microbiota-miRNA relationship in AD, offering potential pathways for novel therapeutic approaches aimed at mitigating the disease's progression.

Evaluation of Drug Permeation Enhancement by Using In Vitro and Ex Vivo Models

Drugs administered by means of extravascular routes of drug administration must be absorbed into the systemic circulation, which involves the movement of the drug molecules across biological barriers such as epithelial cells that cover mucosal surfaces or the stratum corneum that covers the skin. Some drugs exhibit poor permeation across biological membranes or may experience excessive degradation during first-pass metabolism, which tends to limit their bioavailability. Various strategies have been used to improve drug bioavailability. Absorption enhancement strategies include the co-administration of chemical permeation enhancers, enzymes, and/or efflux transporter inhibitors, chemical changes, and specialized dosage form designs. Models with physiological relevance are needed to evaluate the efficacy of drug absorption enhancement techniques. Various in vitro cell culture models and ex vivo tissue models have been explored to evaluate and quantify the effectiveness of drug permeation enhancement strategies. This review deliberates on the use of in vitro and ex vivo models for the evaluation of drug permeation enhancement strategies for selected extravascular drug administration routes including the nasal, oromucosal, pulmonary, oral, rectal, and transdermal routes of drug administration.

Recent Progress in PDMS-Based Microfluidics Toward Integrated Organ-on-a-Chip Biosensors and Personalized Medicine

The organ-on-a-chip (OoC) technology holds significant promise for biosensors and personalized medicine by enabling the creation of miniature, patient-specific models of human organs. This review studies the recent advancements in the application of polydimethylsiloxane (PDMS) microfluidics for OoC purposes. It underscores the main fabrication technologies of PDMS microfluidic systems, such as photolithography, injection molding, hot embossing, and 3D printing. The review also highlights the crucial role of integrated biosensors within OoC platforms. These electrochemical, electrical, and optical sensors, integrated within the microfluidic environment, provide valuable insights into cellular behavior and drug response. Furthermore, the review explores the exciting potential of PDMS-based OoC technology for personalized medicine. OoC devices can forecast drug effectiveness and tailor therapeutic strategies for patients by incorporating patient-derived cells and replicating individual physiological variations, helping the healing process and accelerating recovery. This personalized approach can revolutionize healthcare by offering more precise and efficient treatment options. Understanding OoC fabrication and its applications in biosensors and personalized medicine can play a pivotal role in future implementations of multifunctional OoC biosensors.

Enhanced small intestinal organoid-derived epithelial cell adhesion and growth in organ-on-a-chip devices

Organ-on-a-chip devices are predominately made of the polymer polymethylsiloxane (PDMS), exhibiting several attractive properties e.g., transparency, gas permeability, and biocompatibility. However, the attachment of cells to this polymer has proven challenging, especially for delicate primary cells e.g., small intestinal organoid-derived epithelial cells. Hence, a need to functionalize and coat the surface has arisen to render it more hydrophilic and improve its ability to support cell adhesion and growth. While previous research has demonstrated some successful results in culturing primary cells, no comprehensive and comparative protocol has been proposed. Here, we provide a protocol for enhanced small intestinal organoid-derived epithelial cell adhesion and growth on PDMS and plastics, assessing both PDMS surface functionalization, adhesion protein coating as well as medium selection. We assess PDMS functionalization using (3-aminopropyl)trimethoxysilane (APTMS) or polyethyleneimine-glutaraldehyde (PEIGA), and adhesion protein coating using various Laminins, Collagen I, Matrigel, or mixtures thereof. Finally, we assess the use of two different medium compositions including growth factors EGF, Noggin and R-spondin1 (ENR medium) alone or combined with the two small molecules CHIR99021 and valproic acid (CV medium). We envision that our results will be useful for further attempts in emulating the small intestine using plastic- or PDMS-based devices for organs-on-a-chip development.

Advanced polymeric systems for colon drug delivery: from experimental models to market applications

In recent years, nano and micro drug delivery systems targeting the colon have gained more attention due to increasing interest in treating colon diseases such as colorectal cancer and inflammatory bowel disease, i.e., Crohn's disease and ulcerative colitis. Usually, nanocarriers are exploited for their enhanced permeability properties, allowing higher penetration effects and bioavailability, while microcarriers are primarily used for localized and sustained release. In bowel diseases, carriers must go into a delicate environment with a strict balance of gut bacteria (e.g., colon), and natural or biodegradable polymers capable of ensuring lower toxicity are preferred. However, these systems are primarily delivered orally, so the carrier must go through the whole gastrointestinal tract, where it encounters significant pH fluctuations, different mucus layers, several enzymes, and a long transit time. For this reason, various approaches have been explored and evaluated, especially using pH-responsive and time-dependent systems. This review provides an overview of the contemporary methodologies employed in orally administered nano- and microparticles for colon delivery, encompassing both in vivo and in vitro investigations. It evaluates their strengths, weaknesses, constraints, and potential enhancements, leveraging mathematical and microfluidic models. Furthermore, it focuses explicitly on systems that have already reached the market and are presently employed in treating severe colon diseases.

In silico modelling of organ-on-a-chip devices: an overview

An organ-on-a-chip (OOAC) is a microscale device designed to mimic the functions and complexity of in vivo human physiology. Different from traditional culture systems, OOACs are capable of replicating the biochemical microenvironment, tissue-tissue interactions, and mechanical dynamics of organs thanks to the precise control offered by microfluidic technology. Diverse OOAC devices specific to different organs have been proposed for experimental research and applications such as disease modelling, personalized medicine and drug screening. Previous studies have demonstrated that the mathematical modelling of OOAC can facilitate the optimization of chips' microenvironments, serving as an essential tool to design and improve microdevices which allow reproducible growth of cell culture, reducing the time and cost of experimental testing. Here, we review recent modelling approaches for various OOAC devices, categorized according to the type of organs. We discuss the opportunities for integrating multiphysics with multicellular computational models to better characterize and predict cell culture dynamics. Additionally, we explore how developing more detailed OOAC models would support a more rapid and effective development of microdevices, and the design of robust protocols to grow and control cell cultures.

Mechanobiological Approach for Intestinal Mucosal Immunology

The intestinal area is composed of diverse cell types that harmonize gut homeostasis, which is influenced by both endogenous and exogenous factors. Notably, the environment of the intestine is exposed to several types of mechanical forces, including shear stress generated by fluid flow, compression and stretch generated by luminal contents and peristaltic waves of the intestine, and stiffness attributed to the extracellular matrix. These forces play critical roles in the regulation of cell proliferation, differentiation, and migration. Many efforts have been made to simulate the actual intestinal environment in vitro. The three-dimensional organoid culture system has emerged as a powerful tool for studying the mechanism of the intestinal epithelial barrier, mimicking rapidly renewing epithelium from intestinal stem cells (ISCs) in vivo. However, many aspects of how mechanical forces, such as shear stress, stiffness, compression, and stretch forces, influence the intestinal area remain unresolved. Here, we review the recent studies elucidating the impact of mechanical forces on intestinal immunity, interaction with the gut microbiome, and intestinal diseases.

Bridging the gap: From petri dish to patient - Advancements in translational drug discovery

Translational research serves as the bridge between basic research and practical applications in clinical settings. The journey from "bench to bedside" is fraught with challenges and complexities such as the often-observed disparity between how compounds behave in a laboratory setting versus in the complex systems of living organisms. The challenge is further compounded by the limited ability of in vitro models to mimic the specific biochemical environment of human tissues. This article explores and details the recent advancements and innovative approaches that are increasingly successful in bridging the gap between laboratory research and patient care. These advancements include, but are not limited to, sophisticated in vitro models such as organ-on-a-chip and computational models that utilize artificial intelligence to predict drug efficacy and safety. The article aims to showcase how these technologies improve the predictability of drug performance in human bodies and significantly speed up the drug development process. Furthermore, it discusses the role of biomarker discovery in preparation of more targeted and personalized therapy approaches and covers the impact of regulatory changes designed to facilitate drug approvals. Additionally, by providing detailed case studies of successful applications, we illustrate the practical impacts of these innovations on drug discovery and patient care.

Innovations in intestinal organoid technology featuring an open apical surface

Since the development of the three-dimensional (3D) "mini-gut" culture system, adult stem cell-derived organoid technology has rapidly advanced, providing in vitro models that replicate key cellular, molecular, and physiological properties of multiple organs. The 3D intestinal organoid system has resolved many long-standing challenges associated with immortalized or cancer cell cultures, offering unparalleled capabilities for modeling gastrointestinal development and diseases. However, significant limitations remain, including restricted accessibility to the epithelial apical surface for studying host-microbe interactions, interruptions in modeling chronic gastrointestinal diseases due to frequent passaging and dissociation, and the absence of mechanical cues such as peristalsis and luminal flow, which are critical for organ development and function. To address these challenges, recent advancements have introduced Transwell-based monolayer cultures and microfluidic device-based technologies including "organ-on-a-chip" and scaffold-guided 'mini-gut' system. This review highlights these innovations, with a focus on adult stem cell-derived intestinal organoid models that feature an open apical surface and discusses their prospects and challenges for advancing basic research and clinical applications.

A Microfluidic-Based Cell-Stretching Culture Device That Allows for Easy Preparation of Slides for Observation with High-Magnification Objective Lenses

Microfluidic-based cell-stretching devices are vital for studying the molecular pathways involved in cellular responses to mechanobiological processes. Accurate evaluation of these responses requires detailed observation of cells cultured in this cell-stretching device. This study aimed to develop a method for preparing microscope slides to enable high-magnification imaging of cells in these devices. The key innovation is creating a peelable bond between the cell culture membrane and the upper channel, allowing for easy removal of the upper layer and precise cutting of the membrane for high-magnification microscopy. Using the fabricated device, OP9 cells (15,000 cells/channel) were stretched, and the effects of focal adhesion proteins and the intracellular distribution of YAP1 were examined under a fluorescence microscope with 100× and 60× objectives. Stretch stimulation increased integrinβ1 expression and promoted integrin-vinculin complex formation by approximately 1.4-fold in OP9 cells. Furthermore, YAP1 nuclear localization was significantly enhanced (approximately 1.3-fold) during stretching. This method offers a valuable tool for researchers using microfluidic-based cell-stretching devices. The advancement of imaging techniques in microdevice research is expected to further drive progress in mechanobiology research.

Microfluidic organ-on-chip systems for periodontal research: advances and future directions

Advances in tissue engineering and microfluidic technologies have enabled the development of sophisticated in vitro models known as organ-on-a-chip (OoC) or microphysiological systems. These systems enable to potential to simulate the dynamic interactions between host tissues and their microenvironment including microbes, biomaterials, mechanical forces, pharmaceutical, and consumer-care products. These fluidic technologies are increasingly being utilized to investigate host-microbe and host-material interactions in oral health and disease. Of interest is their application in understanding periodontal disease, a chronic inflammatory condition marked by the progressive destruction of periodontal tissues, including gingiva, periodontal ligament, and alveolar bone. The pathogenesis of periodontal disease involves a complex interplay between microbial dysbiosis and host immune responses, which can lead to a loss of dental support structures and contribute to systemic conditions such as cardiovascular disease, diabetes, and inflammatory bowel disease. This provides a comprehensive overview of the latest developments in millifluidic and microfluidic systems designed to emulate periodontal host-microbe and host-material interactions. We discuss the critical engineering and biological considerations in designing these platforms, their applications in studying oral biofilms, periodontal tissue responses, and their potential to unravel disease mechanisms and therapeutic targets in periodontal disease.

Next-Generation Approaches for Biomedical Materials Evaluation: Microfluidics and Organ-on-a-Chip Technologies

Biological evaluation of biomedical materials faces constraints imposed by the limitations of traditional in vitro and animal experiments. Currently, miniaturized and biomimetic microfluidic technologies and organ-on-chip systems have garnered widespread attention in the field of drug development. However, their exploration in the context of biomedical material evaluation and medical device development remains relatively limited. In this review, a summary of existing biological evaluation methods, highlighting their respective advantages and drawbacks is provided. The application of microfluidic technologies in the evaluation of biomedical materials, emphasizing the potential of organ-on-chip systems as highly biomimetic in vitro models in material evaluation is then focused. Finally, the challenges and opportunities associated with utilizing organ-on-chip systems to evaluate biomedical materials in the field of material evaluation are discussed. In conclusion, the integration of advanced microfluidic technologies and organ-on-chip systems presents a potential paradigm shift in the biological assessment of biomedical materials, offering the prospective of more accurate and predictive in vitro models in the development of medical devices.

Gut-on-a-Chip Reveals Enhanced Peristalsis Reduces Nanoplastic-Induced Inflammation

Nanoplastics (NPs) pollution is a global issue posing potential threats to human health, particularly the digestive system. NPs may exacerbate intestinal inflammation, increasing the risk of inflammatory bowel disease. However, the impact of intestinal peristalsis on NP-induced inflammation remains unknown. Here, a biomimetic gut-on-a-chip (GOC) with integrated online sensing is presented to investigate NPs' impact on intestinal inflammation and propose enhanced peristalsis as a potential intervention. The GOC simulates intestinal peristalsis through periodic stretching and the optimized sensors dynamically detect inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) over 12 d with low detection limits (0.0095 and 0.0020 pg mL-1). Exposure to NPs led to vacuolization, apoptosis, and loss of tight junction proteins in intestinal cells, with IL-6 and TNF-α secretion peaking at 24 h (1341.55 ± 64.91 and 862.03 ± 66.45 pg mL-1). Notably, increasing periodic strain alleviates inflammatory cytokines secretion induced by NPs. With strain increased from 5% to 6.5%, IL-6 and TNF-α secretion decrease by 2.73-fold and 3.34-fold, respectively. This highlights the protective role of intestinal peristalsis in reducing NP-induced inflammation.

Functional Assessment of a Bioprinted Immuno-Mimetic Peyer's Patch Recapitulating Gut-Associated Lymphoid Tissue

Gut immune models have attracted much interest in better understanding the microbiome in the human gastrointestinal tract. The gut-associated lymphoid tissue (GALT) has complex structures that interact with microorganisms, including the intestinal monolayer as a physiological barrier and the Peyer's patch (PP) involved in the immune system. Although essential for studying GALT and microbiome interactions, current research often uses simplified models that only recapitulate some components. In this study, GALT is recapitulated to consider the morphology and function of lymphocyte-containing PP beneath the intestinal monolayer and to analyze microbiome interaction. Using the bioprinting technique, a dome-shaped structure array for the PP is fabricated, and epithelial cells are cocultured to form the intestinal monolayer. The developed GALT model shows stable cell differentiation on the hydrogel while exhibiting durability against lipopolysaccharides. It also exhibits increased responsiveness to Escherichia coli, as indicated by elevated nitric oxide levels. In addition, the model underscores the critical role of GALT in maintaining bacterial coexistence and in facilitating immune defense against foreign antigens through the secretion of immunoglobulin A by lymphocyte spheroids. The proposed GALT model is expected to provide significant insights into studying the gut-immune system complexity and microbiome.

Harnessing 3D models to uncover the mechanisms driving infectious and inflammatory disease in the intestine

Representative models of intestinal diseases are transforming our knowledge of the molecular mechanisms of disease, facilitating effective drug screening and avenues for personalised medicine. Despite the emergence of 3D in vitro intestinal organoid culture systems that replicate the genetic and functional characteristics of the epithelial tissue of origin, there are still challenges in reproducing the human physiological tissue environment in a format that enables functional readouts. Here, we describe the latest platforms engineered to investigate environmental tissue impacts, host-microbe interactions and enable drug discovery. This highlights the potential to revolutionise knowledge on the impact of intestinal infection and inflammation and enable personalised disease modelling and clinical translation.

Biomechanical research using advanced micro-nano devices: In-Vitro cell Characterization focus

BACKGROUND

Cells in the body reside in a dynamic microenvironment subjected to various physical stimuli, where mechanical stimulation plays a crucial role in regulating cellular physiological behaviors and functions.

AIM OF REVIEW

Investigating the mechanisms and interactions of mechanical transmission is essential for understanding the physiological and functional interplay between cells and physical stimuli. Therefore, establishing an in vitro biomechanical stimulation cell culture system holds significant importance for research related to cellular biomechanics.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this review, we primarily focused on various biomechanically relevant cell culture systems and highlighted the advancements and prospects in their preparation processes. Firstly, we discussed the types and characteristics of biomechanics present in the microenvironment within the human body. Subsequently, we introduced the research progress, working principles, preparation processes, potential advantages, applications, and challenges of various biomechanically relevant in vitro cell culture systems. Additionally, we summarized and categorized currently commercialized biomechanically relevant cell culture systems, offering a comprehensive reference for researchers in related fields.

Rapid automated production of tubular 3D intestine-on-a-chip with diverse cell types using coaxial bioprinting

Despite considerable animal sacrifices and investments, drug development often falters in clinical trials due to species differences. To address this issue, specific in vitro models, such as organ-on-a-chip technology using human cells in microfluidic devices, are recognized as promising alternatives. Among the various organs, the human small intestine plays a pivotal role in drug development, particularly in the assessment of digestion and nutrient absorption. However, current intestine-on-a-chip devices struggle to accurately replicate the complex 3D tubular structures of the human small intestine, particularly when it comes to integrating a variety of cell types effectively. This limitation is primarily due to conventional fabrication methods, such as soft lithography and replica molding. In this research, we introduce a novel coaxial bioprinting method to construct 3D tubular structures that closely emulate the organization and functionality of the small intestine with multiple cell types. To ensure stable production of these small intestine-like tubular structures, we analyzed the rheological properties of bioinks to select the most suitable materials for coaxial bioprinting technology. Additionally, we conducted biological assessments to validate the gene expression patterns and functional attributes of the 3D intestine-on-a-chip. Our 3D intestine-on-a-chip, which faithfully replicates intestinal functions and organization, demonstrates clear superiority in both structure and biological function compared to the conventional 2D model. This innovative approach holds significant promise for a wide range of future applications.

Advancements in Microphysiological systems: Exploring organoids and organ-on-a-chip technologies in drug development -focus on pharmacokinetics related organs

This study explored the evolving landscape of Microphysiological Systems (MPS), with a focus on organoids and organ-on-a-chip (OoC) technologies, which are promising alternatives to animal testing in drug discovery. MPS technology offers in vitro models with high physiological relevance, simulating organ function for pharmacokinetic studies. Organoids composed of 3D cell aggregates and OoCs mimicking in vivo environments based on microfluidic platforms represent the forefront of MPS. This paper provides a comprehensive overview of their application in studying the gut, liver, and kidney and their challenges in becoming reliable alternatives to in vivo models. Although MPS technology is not yet fully comparable to in vivo systems, its continued development, aided by in silico, automation, and AI approaches, is anticipated to bring about further advancements. Collaboration across multiple disciplines and ongoing regulatory discussions will be crucial in driving MPS toward practical and ethical applications in biomedical research and drug development.

A Review on Microengineering of Epithelial Barriers for Biomedical and Pharmaceutical Research

Epithelial tissue forms a barrier around the human body and visceral organs, providing protection, permeation, sensation, and secretion. It is vital for our sustenance as it protects the tissue from harm and injury by restricting the entry of foreign bodies inside. Furthermore, it is a strong barrier to drugs, nutrients, and other essential deliverables. This layer also houses a large consortium of microbes, which thrive in tandem with human tissue, providing several health benefits. Moreover, the complex interplay of the microbiome with the barrier tissue is poorly understood. Therefore, replicating these barrier tissues on microdevices to generate physiological and pathophysiological models has been a huge interest for researchers over the last few decades. The artificially engineered reconstruction of these epithelial cellular barriers on microdevices could help underpin the host-microbe interaction, generating a physiological understanding of the tissue, tissue remodeling, receptor-based selective diffusion, drug testing, and others. In addition, these devices could reduce the burden of animal sacrifices for similar research and minimize the failure rate in drug discovery due to the use of primary human cells and others. This review discusses the nature of the epithelial barrier at different tissue sites, the recent developments in creating engineered barrier models, and their applications in pathophysiology, host-microbe interactions, drug discovery, and cytotoxicity. The review aims to provide know-how and knowledge behind engineered epithelial barrier tissue to bioengineers, biotechnologists, and scientists in allied fields.

Development of intestinal organoids and microphysiological systems and their application to drug discovery

The intestines are an important organ with a variety of functions. For drug discovery research, experimental animals and Caco-2 cells derived from a human colon carcinoma may be used to evaluate the absorption and safety of orally administered drugs. These systems have issues, such as species differences with humans in experimental animals, variations in gene expression patterns, very low drug-metabolizing activities in Caco-2 cells, and the recent trend toward reduced animal testing. Thus, there is a need for new evaluation systems. Intestinal organoid technology and microphysiological systems (MPS) have attracted attention as novel evaluation systems for predicting drug disposition, safety, and efficacy in humans in vitro. Intestinal organoids are three-dimensional structures that contain a variety of intestinal cells. They also contain crypt-villus structures similar to those of living bodies. Using MPS, it is possible to improve the functionality of cells and evaluate the linkage and crosstalk between the intestine and the liver. These systems are expected to be powerful tools for drug discovery research to predict efficacy and toxicity in humans. This review outlines the current status of intestinal organoids and MPS studies.

Inflammatory Bowel Disease Drivers Revealed in Human Organ Chips

Inflammatory bowel disease (IBD) patients exhibit compromised intestinal barrier function and decreased mucus accumulation, as well as increased inflammation, fibrosis, and cancer risk, with symptoms often being exacerbated in women during pregnancy. Here, we show that these IBD hallmarks can be replicated using human Organ Chips lined by IBD patient-derived colon epithelial cells interfaced with matched fibroblasts cultured under flow. Use of heterotypic tissue recombinants revealed that IBD fibroblasts are the primary drivers of multiple IBD symptoms. Inflammation and fibrosis are accentuated by peristalsis-like motions in IBD Chips and when exposed to pregnancy-associated hormones in female IBD Chips. Carcinogen exposure also increases inflammation, gene mutations, and chromosome duplication in IBD Chips, but not in Healthy Chips. These data enabled by human Organ Chip technology suggest that the intestinal stroma and peristalsis-associated mechanical deformations play a key role in driving inflammation and disease progression in male and female IBD patients.

Intestinal transport of organic food compounds and drugs: A scoping review on the alterations observed in chronic kidney disease

BACKGROUND AND AIMS

Around 850 million people worldwide are affected by chronic kidney disease (CKD). Patients with CKD often develop malnutrition and sarcopenia and changes in the pharmacokinetics of drugs. A reduced kidney function partially explains the prolonged half-life of certain drugs due to decreased renal clearance, which leads to an increased risk of adverse effects. While the intestine plays a fundamental role in this context, a systematic review of the effects of CKD on intestinal transport is lacking. We aimed to systematically summarize all the available evidence on intestinal transport of organic food components (carbohydrates/sugar, proteins/amino acids, fats, vitamins) and drugs (including drug transporters) in CKD.

METHODS

We conducted a systematic search of all the articles published until the 1st of April 2024, on five databases i.e. Embase, PubMed, Web of Science Core Collection, Cochrane Library, and Scopus. This systematic review was registered on the Open Science Framework (OSF) (osf.io/5e6wb) and was carried out according to the PRISMA 2020 guidelines.

RESULTS

From 9205 articles identified, 68 met the inclusion criteria. Absorption of organic food compounds seems to be altered, in general, and reduced for vitamins. The expression of intestinal efflux drug transporters may be altered in CKD.

CONCLUSIONS

Despite alterations in intestinal transport is suggested to be altered in CKD, the lack of recent studies, the paucity of human data and the heterogeneity of the methodologies used underscore the need for more research on the effect of CKD and uremia on intestinal transport.

Organ chips with integrated multifunctional sensors enable continuous metabolic monitoring at controlled oxygen levels

Despite remarkable advances in Organ-on-a-chip (Organ Chip) microfluidic culture technology, recreating tissue-relevant physiological conditions, such as the region-specific oxygen concentrations, remains a formidable technical challenge, and analysis of tissue functions is commonly carried out using one analytical technique at a time. Here, we describe two-channel Organ Chip microfluidic devices fabricated from polydimethylsiloxane and gas impermeable polycarbonate materials that are integrated with multiple sensors, mounted on a printed circuit board and operated using a commercially available Organ Chip culture instrument. The novelty of this system is that it enables the recreation of physiologically relevant tissue-tissue interfaces and oxygen tension as well as non-invasive continuous measurement of transepithelial electrical resistance, oxygen concentration and pH, combined with simultaneous analysis of cellular metabolic activity (ATP/ADP ratio), cell morphology, and tissue phenotype. We demonstrate the reliable and reproducible functionality of this system in living human Gut and Liver Chip cultures. Changes in tissue barrier function and oxygen tension along with their functional and metabolic responses to chemical stimuli (e.g., calcium chelation, oligomycin) were continuously and noninvasively monitored on-chip for up to 23 days. A physiologically relevant microaerobic microenvironment that supports co-culture of human intestinal cells with living Lactococcus lactis bacteria also was demonstrated in the Gut Chip. The integration of multi-functional sensors into Organ Chips provides a robust and scalable platform for the simultaneous, continuous, and non-invasive monitoring of multiple physiological functions that can significantly enhance the comprehensive and reliable evaluation of engineered tissues in Organ Chip models in basic research, preclinical modeling, and drug development.

Micro- and nano-fibers for organ-on-a-chip: Construction, applications, and prospects

Organ-on-a-chip, an in vitro biomimetic microsystem that enables precise regulation and real-time observation of the cell microenvironment, has the potential to become a powerful platform for recapitulating the real microenvironment of organs in vitro. Microenvironmental factors, such as living cells, three-dimensional (3D) culture, tissue-tissue interfaces, and biomechanical factors, are important cues in the construction of biomimetic microsystems. It is important to provide an appropriate 3D culture environment for living cells to grow. Fibers, particularly microfibers and nanofibers, can provide a suitable 3D culture environment for living cells via surface adhesion or internal loading. In addition, fibers can further expand their applications in tissue engineering and biomedical research by being assembled at a higher level in various ways to create functional 3D tissues or organs with more complex structures. The use of fiber to construct an organ-on-a-chip, whether as a 3D scaffold for cell culture or to more closely mimic real tissues/organs, will introduce new ideas and strategies for developing novel organ-on-a-chip systems. Based on this context, this review summarizes the research progress in the construction and applications of micro/nanofibers for organ-on-a-chip systems. It outlines the preparation methods and material selections for micro/nanofibers and provides a detailed overview of their respective strategies for cell 3D culture and organ-on-a-chip construction. This review also highlights the main research findings and applications of micro/nanofiber in this field, which have significant implications for future practice, and finally concludes by examining potential directions for future development.

Transformation gap from research findings to large-scale commercialized products in microfluidic field

The field of microfluidics has experienced rapid growth in the last several decades, yet it isn't considered to be a large industry comparable to semiconductor and consumer electronics. In this review, we analyzed the entire process of the transformation from research findings to commercialized products in microfluidics, as well as the significant gap during the whole developing process between microchip fabrication in R&D and large-scale production in the industry. We elaborated in detail on various materials in the microfluidics industry, including silicon, glass, PDMS, and thermoplastics, discussing their characteristics, production processes, and existing products. Despite challenges hindering the large-scale commercialization of microfluidic chips, ongoing advancements and applications are expected to integrate microfluidic technology into everyday life, transforming it into a commercially viable field with substantial potential and promising prospects.

iPS cell therapy 2.0: Preparing for next-generation regenerative medicine

This year marks the tenth anniversary of the world's first transplantation of tissue generated from induced pluripotent stem cells (iPSCs). There is now a growing number of clinical trials worldwide examining the efficacy and safety of autologous and allogeneic iPSC-derived products for treating various pathologic conditions. As we patiently wait for the results from these and future clinical trials, it is imperative to strategize for the next generation of iPSC-based therapies. This review examines the lessons learned from the development of another advanced cell therapy, chimeric antigen receptor (CAR) T cells, and the possibility of incorporating various new bioengineering technologies in development, from RNA engineering to tissue fabrication, to apply iPSCs not only as a means to achieve personalized medicine but also as designer medical applications.

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.

Revolutionizing IBD research with on-chip models of disease modeling and drug screening

Inflammatory bowel disease (IBD) comprises chronic inflammatory conditions with complex mechanisms and diverse manifestations, posing significant clinical challenges. Traditional animal models and ethical concerns in human studies necessitate innovative approaches. This review provides an overview of human intestinal architecture in health and inflammation, emphasizing the role of microfluidics and on-chip technologies in IBD research. These technologies allow precise manipulation of cellular and microbial interactions in a physiologically relevant context, simulating the intestinal ecosystem microscopically. By integrating cellular components and replicating 3D tissue architecture, they offer promising models for studying host-microbe interactions, wound healing, and therapeutic approaches. Continuous refinement of these technologies promises to advance IBD understanding and therapy development, inspiring further innovation and cross-disciplinary collaboration.

Shearmetry of Fluids with Tunable Rheology by Polarized Luminescence of Rare Earth-Doped Nanorods

Shear stress plays a critical role in regulating physiological processes within microcirculatory systems. While particle imaging velocimetry is a standard technique for quantifying shear flow, uncertainty near boundaries and low resolution remain severe restrictions. Additionally, shear stress determination is particularly challenging in biofluids due to their significant non-Newtonian behaviors. The present study develops a shearmetry technique in physiological settings using a biomimetic fluid containing rare earth-doped luminescent nanorods acting in two roles. First, they are used as colloidal additives adjusting rheological properties in physiological media. Their anisotropic morphology and interparticle interaction synergistically induce a non-Newtonian shear-thinning effect emulating real biofluids. Second, they can probe shear stress due to the shear-induced alignment. The polarized luminescence of the nanorods allows for quantifying their orientational order parameter and thus correlated shear stress. Using scanning confocal microscopy, we demonstrate the tomographic mapping of the shear stress distribution in microfluidics. High shear stress is evident near the constriction and the cellular periphery, in which non-Newtonian effects can have a significant impact. This emerging shearmetry technique is promising for implementation in physiological and rheological environments of biofluids.

Predicting nanocarrier permeation across the human intestine in vitro: model matters

For clinical translation of oral nanocarriers, simulation of the intestinal microenvironment during in vitro testing is crucial to evaluate interactions with the intestinal mucosa. However, studies are often conducted using simplistic cell culture models, overlooking key physiological factors, and potentially leading to an overestimation of nanocarrier permeation. In this study, we systematically investigate different tissue models of the human intestine under static cultivation and dynamic flow conditions and analyze the impact of altered tissue characteristics on nanocarrier permeation. Our results reveal that the selection of cell types as well as the respective culture condition have a notable impact on the physiological characteristics of the resulting tissues. Tissue layer thickness, mucus secretion, and barrier impairment, all increase with increasing amounts of goblet cells and the application of dynamic flow conditions. Permeation studies with poly(lactic-co-glycolic acid) (PLGA) nanocarriers with and without polyethylene glycol (PEG) coating elucidate that the amount of mucus present in the respective model is the limiting factor for the permeation of PLGA nanocarriers, while tissue topography presents the key factor influencing PEG-PLGA nanocarrier permeation. Furthermore, both nanocarriers exhibit diametrically opposite permeation kinetics compared to soluble compounds. In summary, these findings reveal the critical role of the implemented test systems on permeation assessment and emphasize that, in the context of preclinical nanocarrier testing, the choice of in vitro model matters.

Leveraging Organ-on-Chip Models to Investigate Host-Microbiota Dynamics and Targeted Therapies for Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an idiopathic gastrointestinal disease with drastically increasing incidence rates. Due to its multifactorial etiology, a precise investigation of the pathogenesis is extremely difficult. Although reductionist cell culture models and more complex disease models in animals have clarified the understanding of individual disease mechanisms and contributing factors of IBD in the past, it remains challenging to bridge research and clinical practice. Conventional 2D cell culture models cannot replicate complex host-microbiota interactions and stable long-term microbial culture. Further, extrapolating data from animal models to patients remains challenging due to genetic and environmental diversity leading to differences in immune responses. Human intestine organ-on-chip (OoC) models have emerged as an alternative in vitro model approach to investigate IBD. OoC models not only recapitulate the human intestinal microenvironment more accurately than 2D cultures yet may also be advantageous for the identification of important disease-driving factors and pharmacological interventions targets due to the possibility of emulating different complexities. The predispositions and biological hallmarks of IBD focusing on host-microbiota interactions at the intestinal mucosal barrier are elucidated here. Additionally, the potential of OoCs to explore microbiota-related therapies and personalized medicine for IBD treatment is discussed.

Ex vivo and miniaturized in vitro models to study microbiota-gut-brain axis

The microbiota-gut-brain axis involves complex bidirectional communication through neural, immune, and endocrine pathways. Microbial metabolites, such as short-chain fatty acids, influence gut motility and brain function by interacting with gut receptors and modulating hormone release. Additionally, microbial components such as lipopolysaccharides and cytokines can cross the gut epithelium and the blood-brain barrier, impacting immune responses and cognitive function. Ex vivo models, which preserve gut tissue and neural segments, offer insight into localized gut-brain communication by allowing for detailed study of nerve excitability in response to microbial signals, but they are limited in systemic complexity. Miniaturized in vitro models, including organ-on-chip platforms, enable precise control of the cellular environment and simulate complex microbiota-host interactions. These systems allow for the study of microbial metabolites, immune responses, and neuronal activity, providing valuable insights into gut-brain communication. Despite challenges such as replicating long-term biological processes and integrating immune and hormonal systems, advancements in bioengineered platforms are enhancing the physiological relevance of these models, offering new opportunities for understanding the mechanisms of the microbiota-gut-brain axis. This review aims to describe the ex vivo and miniaturized in vitro models which are used to mimic the in vivo conditions and facilitate more precise studies of gut brain communication.

An Intelligent Intestine-on-a-Chip for Rapid Screening of Probiotics with Relief-Enteritis Function

Screening probiotics with specific functions is essential for advancing probiotic research. Current screening methods primarily use animal studies or clinical trials, which are inefficient and costly in terms of time, money, and labor. An intelligent intestine-on-a-chip integrating machine learning (ML) is developed to screen relief-enteritis functional probiotics. A high-throughput microfluidic chip combined with environment control systems provides a standardized and scalable intestinal microenvironment for multiple probiotic cocultures. An unsupervised ML-based score analyzer is constructed to accurately, comprehensively, and efficiently evaluate interactions between 12 Bifidobacterium strains and host cells of the colitis model in the intestine-on-a-chips. The most effective contender, Bifidobacterium longum 3-14, is discovered to relieve intestinal inflammation and enhance epithelial barrier function in vitro and in vivo. A distinct advantage of this strategy is that it can intelligently differentiate small therapeutic variations in probiotic strains and prioritize their efficacies, allowing for economical, efficient, accurate functional probiotics screening.

A Pumpless and Tubeless Microfluidic Device Enables Extended In Vitro Development of Cryptosporidium parvum

Background

The enteric parasite Cryptosporidium remains a treatment challenge for drinking water utilities globally due to its resistance to chlorine disinfection. However, the lack of an in vitro culture system for Cryptosporidium that is both cost-effective and reliable remains a key bottleneck in Cryptosporidium research.

Methods

Here we report that the microfluidic culture of human ileocecal colorectal adenocarcinoma (HCT-8) cells under fluid shear stress enables the extended development of Cryptosporidium parvum. Specifically, the growth of C. parvum in a user-friendly pumpless microfluidic device was assessed using immunofluorescence assays, scanning electron microscopy, and quantitative polymerase chain reaction, which revealed that development continued for 10 days in total.

Results

Oocysts produced within the microfluidic device were infective to fresh HCT-8 monolayers; however, these oocysts were only present at low levels.

Conclusions

We anticipate that such microfluidic approaches will facilitate a wide range of in vitro studies on Cryptosporidium and may have the potential to be further developed as a routine infectivity assessment tool for the water industry.

Intestinal organ chips for disease modelling and personalized medicine

Alterations in intestinal structure, mechanics and physiology underlie acute and chronic intestinal conditions, many of which are influenced by dysregulation of microbiome, peristalsis, stroma or immune responses. Studying human intestinal physiology or pathophysiology is difficult in preclinical animal models because their microbiomes and immune systems differ from those of humans. Although advances in organoid culture partially overcome this challenge, intestinal organoids still lack crucial features that are necessary to study functions central to intestinal health and disease, such as digestion or fluid flow, as well as contributions from long-term effects of living microbiome, peristalsis and immune cells. Here, we review developments in organ-on-a-chip (organ chip) microfluidic culture models of the human intestine that are lined by epithelial cells and interfaced with other tissues (such as stroma or endothelium), which can experience both fluid flow and peristalsis-like motions. Organ chips offer powerful ways to model intestinal physiology and disease states for various human populations and individual patients, and can be used to gain new insight into underlying molecular and biophysical mechanisms of disease. They can also be used as preclinical tools to discover new drugs and then validate their therapeutic efficacy and safety in the same human-relevant model.