Organ-on-a-chip for assessing environmental toxicants

Recent advances in environmental toxicology: Exploring gene editing, organ-on-a-chip, chimeric animals, and in silico models

In our daily life, we are exposed to various environmental pollutants in multiple ways. At present, we mainly rely on animal models and two-dimensional cell culture models to evaluate the toxicity of environmental pollutants. Nevertheless, results in animal models do not always apply to humans because of differences between species, while two-dimensional cell culture models cannot replicate the in vivo microenvironments, making it difficult to predict the true toxic response of environmental pollutants in humans. The development of various high-end technologies in recent years has provided new opportunities for environmental toxicology research. The application of these high-end technologies in environmental toxicology can complement the limitations of traditional environmental toxicology screening and more accurately predict the toxicity of environmental pollutants. In this review, we first introduce the advantages and disadvantages of traditional environmental toxicology methods, then review the principles and development of four high-end technologies, such as gene editing, organ-on-a-chip, chimeric animals, and in silico models, summarize their application in toxicity testing, and finally emphasize their importance/potential in environmental toxicology.

Tissue chips as headway model and incitement technology

Tissue on a chip or organ-on-chip (OOC) is a technology that's dignified to form a transformation in drug discovery through the use of advanced platforms. These are 3D in-vitro cell culture models that mimic micro-environment of human organs or tissues on artificial microstructures built on a portable microfluidic chip without involving sacrificial humans or animals. This review article aims to offer readers a thorough and insightful understanding of technology. It begins with an in-depth understanding of chip design and instrumentation, underlining its pivotal role and the imperative need for its development in the modern scientific landscape. The review article explores into the myriad applications of OOC technology, showcasing its transformative impact on fields such as radiobiology, drug discovery and screening, and its pioneering use in space research. In addition to highlighting these diverse applications, the article provides a critical analysis of the current challenges that OOC technology faces. It examines both the biological and technical limitations that hinder its progress and efficacy and discusses the potential advancements and innovations that could drive the OOC technology forward. Through this comprehensive review, readers will gain a deep appreciation of the significance, capabilities, and evolving landscape of OOC technology.

Protective effect of lycopene against celecoxib induced fat deposition and glycogen reduction in liver cells

Objective

Oxidative stress develops because of a shift in the prooxidant-antioxidant balance toward the former, because of disturbances in redox signaling and control. Celecoxib (Cb), a selective COX-2 inhibitor, is a drug that effectively decreases pain and inflammation. However, Cb causes oxidative injury to hepatic tissues via enhanced lipid peroxidation, thus resulting in excessive production of reactive oxygen species. Consequently, frequent or long-term Cb use may lead to hepatic, renal, and other noticeable adverse effects. Lycopene (lyco), a potent antioxidant naturally occurring in pigmented fruits and vegetables, actively eradicates singlet oxygen and other free radicals, thereby protecting cells against destruction of the plasma membrane by free radicals.

Methods

We hypothesized that lyco might protect rat liver cells against Cb-induced oxidative stress, thus reducing fatty infiltration and glycogen depletion. Rats were randomized into three groups (with ten rats each) receiving control (group A, saline only), Cb (group B, 50 mg/kg, orally), or Cb + lyco (group C, 50 mg/kg, orally) for 30 days. Subsequently, liver tissues were examined, and the average liver weight and histological changes in fat and glycogen content were determined.

Results

Lyco mitigated hepatocyte damage in Cb-treated rats, reducing fat accumulation and glycogen loss, probably through its antioxidant properties. Concomitant lyco and Cb intake prevented hepatotoxic adverse effects due to oxidative injury, as well as non-alcoholic fatty liver disease (NAFLD), a key component of metabolic syndrome. Moreover, the binding orientation of lyco in the binding site of COX-2 enzyme revealed that the docked complex had noteworthy binding strength.

Conclusion

In conclusion, our study revealed lyco's protective effects against Cb-induced hepatic damage by reducing fat and glycogen depletion.

Modeling Wound Chronicity In Vivo: The Translational Challenge to Capture the Complexity of Chronic Wounds

In an aging society with common lifestyle-associated health issues such as obesity and diabetes, chronic wounds pose a frequent challenge that physicians face in everyday clinical practice. Therefore, nonhealing wounds have attracted much scientific attention. Several in vitro and in vivo models have been introduced to deepen our understanding of chronic wound pathogenesis and amplify therapeutic strategies. Understanding how wounds become chronic will provide insights to reverse or avoid chronicity. Although choosing a suitable model is of utmost importance to receive valuable outcomes, an ideal in vivo model capturing the complexity of chronic wounds is still missing and remains a translational challenge. This review discusses the most relevant mammalian models for wound healing studies and provides guidance on how to implement the hallmarks of chronic wounds. It highlights the benefits and pitfalls of established models and maps out future avenues for research.

The hidden threat: Environmental toxins and their effects on gut microbiota

The human gut microbiota (GM), which consists of a complex and diverse ecosystem of bacteria, plays a vital role in overall wellness. However, the delicate balance of this intricate system is being compromised by the widespread presence of environmental toxins. The intricate connection between contaminants in the environment and human well-being has garnered significant attention in recent times. Although many environmental pollutants and their toxicity have been identified and studied in laboratory settings and animal models, there is insufficient data concerning their relevance to human physiology. Consequently, research on the toxicity of environmental toxins in GM has gained prominence in recent years. Various factors, such as air pollution, chemicals, heavy metals, and pesticides, have a detrimental impact on the composition and functioning of the GM. This comprehensive review aims to comprehend the toxic effects of numerous environmental pollutants, including antibiotics, endocrine-disrupting chemicals, heavy metals, and pesticides, on GM by examining recent research findings. The current analysis concludes that different types of environmental toxins can lead to GM dysbiosis and have various potential adverse effects on the well-being of animals. We investigate the alterations to the GM composition induced by contaminants and their impact on overall well-being, providing a fresh perspective on research related to pollutant exposure.

The hepatotoxicity assessment of micro/nanoplastics: A preliminary study to apply the adverse outcome pathways

Plastic pollution has become a significant global problem over the years, leading to the continuous decomposition and accumulation of micro/nanoplastics (MNPLs) in the environment. As a result, human exposure to these MNPLs is inevitable. The liver, in particular, is highly susceptible to potential MNPL toxicity. In this study, we systematically reviewed the current literature on MNPLs-induced hepatotoxicity and collected data on toxic events occurring at different biological levels. Then, to better understand the cause-mechanism causality, we developed an Adverse Outcome Pathway (AOP) framework for MNPLs-induced hepatotoxicity. The AOP framework provided insights into the mechanism of MNPL-induced hepatotoxicity and highlighted potential health risks such as liver dysfunction and inflammation, metabolism disorders and liver fibrosis. Moreover, we discussed the potential application of emerging toxicological models in the hepatotoxicity study. Liver organoids and liver-on-chips, which can simulate the structure and function of the liver in vitro, offer a promising alternative platform for toxicity testing and risk assessment. We proposed combining the AOP framework with these emerging toxicological models to improve our understanding of the hepatotoxic effects of MNPLs. Overall, this study performed a preliminary exploration of novel toxicological methodologies to assess the hepatotoxicity of MNPLs, providing a deeper understanding of environmental toxicology.

Tailoring biomaterials for biomimetic organs-on-chips

Organs-on-chips are microengineered microfluidic living cell culture devices with continuously perfused chambers penetrating to cells. By mimicking the biological features of the multicellular constructions, interactions among organs, vascular perfusion, physicochemical microenvironments, and so on, these devices are imparted with some key pathophysiological function levels of living organs that are difficult to be achieved in conventional 2D or 3D culture systems. In this technology, biomaterials are extremely important because they affect the microstructures and functionalities of the organ cells and the development of the organs-on-chip functions. Thus, herein, we provide an overview on the advances of biomaterials for the construction of organs-on-chips. After introducing the general components, structures, and fabrication techniques of the biomaterials, we focus on the studies of the functions and applications of these biomaterials in the organs-on-chips systems. Applications of the biomaterial-based organs-on-chips as alternative animal models for pharmaceutical, chemical, and environmental tests are described and highlighted. The prospects for exciting future directions and the challenges of biomaterials for realizing the further functionalization of organs-on-chips are also presented.

Development of lumen-based perfusable 3D liver in vitro model using single-step bioprinting with composite bioinks

Hepatic sinusoids are uniquely organized structures that help maintain a spectrum of hepatic functions. Although several in vitro liver models have been developed to replicate liver sinusoids, most of these platforms require complex, multi-step fabrication methods making it difficult to achieve truly three-dimensional (3D) channel geometries. In this study, a single-step bioprinting technique was demonstrated to simultaneously print a chip platform and develop a perfusable vascularized liver sinusoid in vitro model. The integrated system uses a co-axial-based bioprinting approach to develop a liver sinusoid-like model that consists of a sacrificial core compartment containing a perfusable pre-vascular structure and an alginate-collagen-based shell compartment containing hepatocytes. The lumen-based perfusable 3D liver sinusoid-on-a-chip (LSOC-P) demonstrated significantly better hepatocyte viability, proliferation, and liver-specific gene and protein expression compared to a 3D hepatocyte-based core/shell model with static media and the standard hepatocyte-based 2D sandwich culture system. A drug toxicity evaluation of hepatotoxins highlighted the comparatively higher sensitivity of the LSOC system with a close estimation of the therapeutic range of safe drug concentrations for humans. In conclusion, the current findings indicate that the combinatorial single-step co-axial bioprinting technique is a promising fabrication approach for the development of a perfusable LSOC platform for drug screening applications.

Relationship between Adsorption and Toxicity of Nephrotoxic Drugs in Microphysiological Systems (MPS)

Microphysiological systems (MPS) are an emerging technology for next-generation drug screening in non-clinical tests. Microphysiological systems are microfluidic devices that reconstitute the physiological functions of a human organ using a three-dimensional in vivo-mimicking microenvironment. In the future, MPSs are expected to reduce the number of animal experiments, improve prediction methods for drug efficacy in clinical settings, and reduce the costs of drug discovery. However, drug adsorption onto the polymers used in an MPS is a critical issue for assessment because it changes the concentration of the drug. Polydimethylsiloxane (PDMS), a basic material used for the fabrication of MPS, strongly adsorbs hydrophobic drugs. As a substitute for PDMS, cyclo-olefin polymer (COP) has emerged as an attractive material for low-adsorption MPS. However, it has difficulty bonding with different materials and, therefore, is not commonly used. In this study, we assessed the drug adsorption properties of each material constituting an MPS and subsequent changes in drug toxicity for the development of a low-adsorption MPSs using COP. The hydrophobic drug cyclosporine A showed an affinity for PDMS and induced lower cytotoxicity in PDMS-MPS but not in COP-MPS, whereas adhesive tapes used for bonding adsorbed a significant quantity of drugs, lowering their availability, and was cytotoxic. Therefore, easily-adsorbed hydrophobic drugs and bonding materials having lower cytotoxicity should be used with a low-adsorption polymer such as COP.

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

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

Assaying Proliferation Characteristics of Cells Cultured Under Static Versus Periodic Conditions

Two-dimensional in vitro culture models are widely being employed for assessing a vast variety of biological questions in different scientific fields. Common in vitro culture models are typically maintained under static conditions, where the surrounding culture medium is replaced every few days-typically every 48 to 72 h-with the aim to remove metabolites and to replenish nutrients. Although this approach is sufficient for supporting cellular survival and proliferation, static culture conditions do mostly not reflect the in vivo situation where cells are continuously being perfused by extracellular fluid, and thus, create a less-physiological environment. In order to evaluate whether the proliferation characteristics of cells in 2D culture maintained under static conditions differ from cells kept in a dynamic environment, in this chapter, we provide a protocol for differential analysis of cellular growth under static versus pulsed-perfused conditions, mimicking continuous replacement of extracellular fluid in the physiological environment. The protocol involves long-term life-cell high-content time-lapse imaging of fluorescent cells at 37 °C and ambient CO₂ concentration using multi-parametric biochips applicable for microphysiological analysis of cellular vitality. We provide instructions and useful information for (i) the culturing of cells in biochips, (ii) setup of cell-laden biochips for culturing cells under static and pulsed-perfused conditions, (iii) long-term life-cell high-content time-lapse imaging of fluorescent cells in biochips, and (iv) quantification of cellular proliferation from image series generated from imaging of differentially cultured cells.

Recent Trends in Multiclass Analysis of Emerging Endocrine Disrupting Contaminants (EDCs) in Drinking Water

Ingestion of water is a major route of human exposure to environmental contaminants. There have been numerous studies exploring the different compounds present in drinking water, with recent attention drawn to a new class of emerging contaminants: endocrine-disrupting compounds (EDCs). EDCs encompass a broad range of physio-chemically diverse compounds; from naturally occurring to manmade. Environmentally, EDCs are found as mixtures containing multiple classes at trace amounts. Human exposure to EDCs, even at low concentrations, is known to lead to adverse health effects. Therefore, the ability to evaluate EDC contamination with a high degree of sensitivity and accuracy is of the utmost importance. This review includes (i) discussion on the perceived and actual risks associated with EDC exposure (ii) regulatory actions that look to limit EDC contamination (iii) analytical methods, including sample preparation, instrumentation and bioassays that have been advanced and employed for multiclass EDC identification and quantitation.

Organ-On-A-Chip Database Revealed-Achieving the Human Avatar in Silicon

Organ-on-a-chip (OOC) provides microphysiological conditions on a microfluidic chip, which makes up for the shortcomings of traditional in vitro cellular culture models and animal models. It has broad application prospects in drug development and screening, toxicological mechanism research, and precision medicine. A large amount of data could be generated through its applications, including image data, measurement data from sensors, ~omics data, etc. A database with proper architecture is required to help scholars in this field design experiments, organize inputted data, perform analysis, and promote the future development of novel OOC systems. In this review, we overview existing OOC databases that have been developed, including the BioSystics Analytics Platform (BAP) developed by the University of Pittsburgh, which supports study design as well as data uploading, storage, visualization, analysis, etc., and the organ-on-a-chip database (Ocdb) developed by Southeast University, which has collected a large amount of literature and patents as well as relevant toxicological and pharmaceutical data and provides other major functions. We used examples to overview how the BAP database has contributed to the development and applications of OOC technology in the United States for the MPS consortium and how the Ocdb has supported researchers in the Chinese Organoid and Organs-On-A-Chip society. Lastly, the characteristics, advantages, and limitations of these two databases were discussed.

High-throughput screening paradigms in ecotoxicity testing: Emerging prospects and ongoing challenges

The rapidly increasing number of new production chemicals coupled with stringent implementation of global chemical management programs necessities a paradigm shift towards boarder uses of low-cost and high-throughput ecotoxicity testing strategies as well as deeper understanding of cellular and sub-cellular mechanisms of ecotoxicity that can be used in effective risk assessment. The latter will require automated acquisition of biological data, new capabilities for big data analysis as well as computational simulations capable of translating new data into in vivo relevance. However, very few efforts have been so far devoted into the development of automated bioanalytical systems in ecotoxicology. This is in stark contrast to standardized and high-throughput chemical screening and prioritization routines found in modern drug discovery pipelines. As a result, the high-throughput and high-content data acquisition in ecotoxicology is still in its infancy with limited examples focused on cell-free and cell-based assays. In this work we outline recent developments and emerging prospects of high-throughput bioanalytical approaches in ecotoxicology that reach beyond in vitro biotests. We discuss future importance of automated quantitative data acquisition for cell-free, cell-based as well as developments in phytotoxicity and in vivo biotests utilizing small aquatic model organisms. We also discuss recent innovations such as organs-on-a-chip technologies and existing challenges for emerging high-throughput ecotoxicity testing strategies. Lastly, we provide seminal examples of the small number of successful high-throughput implementations that have been employed in prioritization of chemicals and accelerated environmental risk assessment.

In silico modeling of endocrine organ-on-a-chip systems

The organ-on-a-chip (OoC) is an artificially reconstructed microphysiological system that is implemented using tissue mimics integrated into miniaturized perfusion devices. OoCs emulate dynamic and physiologically relevant features of the body, which are not available in standard in vitro methods. Furthermore, OoCs provide highly sophisticated multi-organ connectivity and biomechanical cues based on microfluidic platforms. Consequently, they are often considered ideal in vitro systems for mimicking self-regulating biophysical and biochemical networks in vivo where multiple tissues and organs crosstalk through the blood flow, similar to the human endocrine system. Therefore, OoCs have been extensively applied to simulate complex hormone dynamics and endocrine signaling pathways in a mechanistic and fully controlled manner. Mathematical and computational modeling approaches are critical for quantitatively analyzing an OoC and predicting its complex responses. In this review article, recently developed in silico modeling concepts of endocrine OoC systems are summarized, including the mathematical models of tissue-level transport phenomena, microscale fluid dynamics, distant hormone signaling, and heterogeneous cell-cell communication. From this background, whole chip-level analytic approaches in pharmacokinetics and pharmacodynamics will be described with a focus on the spatial and temporal behaviors of absorption, distribution, metabolism, and excretion in endocrine biochips. Finally, quantitative design frameworks for endocrine OoCs are reviewed with respect to support parameter calibration/scaling and enable predictive in vitro-in vivo extrapolations. In particular, we highlight the analytical and numerical modeling strategies of the nonlinear phenomena in endocrine systems on-chip, which are of particular importance in drug screening and environmental health applications.

Genome-wide evaluation of transcriptomic responses of human tissues to smoke: A systems biology study

The harmful compounds in various sources of smoke threaten human health. So far, many studies have investigated the effects of compounds of smoke on transcriptome changes in different human tissues. However, no study has been conducted on the effects of these compounds on transcriptome changes in different human tissues simultaneously. Hence, the present study was conducted to identify smoke-related genes (SRGs) and their response mechanisms to smoke in various human cells and tissues using systems biology based methods. A total of 6,484 SRGs were identified in the studied tissues, among which 4,095 SRGs were up-regulated and 2,389 SRGs were down-regulated. Totally, 459 SRGs were smoke-related transcription factors (SRTFs). Gene regulatory network analysis showed that the studied cells and tissues have different gene regulation and responses to compounds of smoke. The comparison of different tissues revealed no common SRG among the all studied tissues. However, the CYP1B1 gene was common among seven cells and tissues, and had the same expression trend. Network analysis showed that the CYP1B1 is a hub gene among SRGs in various cells and tissues. To the best of our knowledge, for the first time, our results showed that compounds of smoke induce and increase the expression of CYP1B1 key gene in all target and non-target tissues of human. Moreover, despite the specific characteristics of CYP1B1 gene and its identical expression trend in target and non-target tissues, it can be used as a biomarker for diagnosis and prognosis.

Microscopic Imaging Methods for Organ-on-a-Chip Platforms

Microscopic imaging is essential and the most popular method for in situ monitoring and evaluating the outcome of various organ-on-a-chip (OOC) platforms, including the number and morphology of mammalian cells, gene expression, protein secretions, etc. This review presents an overview of how various imaging methods can be used to image organ-on-a-chip platforms, including transillumination imaging (including brightfield, phase-contrast, and holographic optofluidic imaging), fluorescence imaging (including confocal fluorescence and light-sheet fluorescence imaging), and smartphone-based imaging (including microscope attachment-based, quantitative phase, and lens-free imaging). While various microscopic imaging methods have been demonstrated for conventional microfluidic devices, a relatively small number of microscopic imaging methods have been demonstrated for OOC platforms. Some methods have rarely been used to image OOCs. Specific requirements for imaging OOCs will be discussed in comparison to the conventional microfluidic devices and future directions will be introduced in this review.

Human Organs-on-Chips: A Review of the State-of-the-Art, Current Prospects, and Future Challenges

New emerging technologies, remarkably miniaturized 3D organ models and microfluidics, enable simulation of the real in vitro microenvironment ex vivo more closely. There are many fascinating features of innovative organ-on-a-chip (OOC) technology, including the possibility of integrating semipermeable and/or stretchable membranes, creating continuous perfusion of fluids into microchannels and chambers (while maintaining laminar flow regime), embedding microdevices like microsensors, microstimulators, micro heaters, or different cell lines, along with other 3D cell culture technologies. OOC systems are designed to imitate the structure and function of human organs, ranging from breathing lungs to beating hearts. This technology is expected to be able to revolutionize cell biology studies, personalized precision medicine, drug development process, and cancer diagnosis/treatment. OOC systems can significantly reduce the cost associated with tedious drug development processes and the risk of adverse drug reactions in the body, which makes drug screening more effective. The review mainly focus on presenting an overview of the several previously developed OOC systems accompanied by subjects relevant to pharmacy-, cancer-, and placenta-on-a-chip. The challenging issues and opportunities related to these systems are discussed, along with a future perspective for this technology.

Emerging Technologies for In Vitro Inhalation Toxicology

Respiratory toxicology remains a major research area in the 21st century since current scenario of airborne viral infection transmission and pollutant inhalation is expected to raise the annual morbidity beyond 2 million. Clinical and epidemiological research connecting human exposure to air contaminants to understand adverse pulmonary health outcomes is, therefore, an immediate subject of human health assessment. Important observations in defining systemic effects of environmental contaminants on inhalation metabolic dysfunction, liver health, and gastrointestinal tract have been well explored with in vivo models. In this review, a framework is provided, a paradigm is established about inhalation toxicity testing in vitro, and a brief overview of breathing Lungs-on-Chip (LoC) as design concepts is given. The optimized bioengineering approaches and microfluidics with their fundamental pros, and cons are presented. There are different strategies that researchers apply to inhalation toxicity studies to assess a variety of inhalable substances and relevant LoC approaches. A case study from published literature and frame arguments about reproducibility as well as in vitro/in vivo correlations are discussed. Finally, the opportunities and challenges in soft robotics, systems inhalation toxicology approach integrating bioengineering, machine learning, and artificial intelligence to address a multitude model for future toxicology are discussed.

Stem cells of aquatic invertebrates as an advanced tool for assessing ecotoxicological impacts

Environmental stressors are assessed through methods that quantify their impacts on a wide range of metrics including species density, growth rates, reproduction, behaviour and physiology, as on host-pathogen interactions and immunocompetence. Environmental stress may induce additional sublethal effects, like mutations and epigenetic signatures affecting offspring via germline mediated transgenerational inheritance, shaping phenotypic plasticity, increasing disease susceptibility, tissue pathologies, changes in social behaviour and biological invasions. The growing diversity of pollutants released into aquatic environments requires the development of a reliable, standardised and 3R (replacement, reduction and refinement of animals in research) compliant in vitro toolbox. The tools have to be in line with REACH regulation 1907/2006/EC, aiming to improve strategies for potential ecotoxicological risks assessment and monitoring of chemicals threatening human health and aquatic environments. Aquatic invertebrates' adult stem cells (ASCs) are numerous and can be pluripotent, as illustrated by high regeneration ability documented in many of these taxa. This is of further importance as in many aquatic invertebrate taxa, ASCs are able to differentiate into germ cells. Here we propose that ASCs from key aquatic invertebrates may be harnessed for applicable and standardised new tests in ecotoxicology. As part of this approach, a battery of modern techniques and endpoints are proposed to be tested for their ability to correctly identify environmental stresses posed by emerging contaminants in aquatic environments. Consequently, we briefly describe the current status of the available toxicity testing and biota-based monitoring strategies in aquatic environmental ecotoxicology and highlight some of the associated open issues such as replicability, consistency and reliability in the outcomes, for understanding and assessing the impacts of various chemicals on organisms and on the entire aquatic environment. Following this, we describe the benefits of aquatic invertebrate ASC-based tools for better addressing ecotoxicological questions, along with the current obstacles and possible overhaul approaches.

Establishing a 3D In Vitro Hepatic Model Mimicking Physiologically Relevant to In Vivo State

Three-dimensional (3D) bioprinting is a promising technology to establish a 3D in vitro hepatic model that holds great potential in toxicological evaluation. However, in current hepatic models, the central area suffers from hypoxic conditions, resulting in slow and weak metabolism of drugs and toxins. It remains challenging to predict accurate drug effects in current bioprinted hepatic models. Here, we constructed a hexagonal bioprinted hepatic construct and incorporated a spinning condition with continuous media stimuli. Under spinning conditions, HepG2 cells in the bioprinted hepatic construct exhibited enhanced proliferation capacity and functionality compared to those under static conditions. Additionally, the number of spheroids that play a role in boosting drug-induced signals and responses increased in the bioprinted hepatic constructs cultured under spinning conditions. Moreover, HepG2 cells under spinning conditions exhibited intensive TGFβ-induced epithelial-to-mesenchymal transition (EMT) and increased susceptibility to acetaminophen (APAP)-induced hepatotoxicity as well as hepatotoxicity prevention by administration of N-acetylcysteine (NAC). Taken together, the results of our study demonstrate that the spinning condition employed during the generation of bioprinted hepatic constructs enables the recapitulation of liver injury and repair phenomena in particular. This simple but effective culture strategy facilitates bioprinted hepatic constructs to improve in vitro modeling for drug effect evaluation.

A Decade of Organs-on-a-Chip Emulating Human Physiology at the Microscale: A Critical Status Report on Progress in Toxicology and Pharmacology

Organ-on-a-chip technology has the potential to accelerate pharmaceutical drug development, improve the clinical translation of basic research, and provide personalized intervention strategies. In the last decade, big pharma has engaged in many academic research cooperations to develop organ-on-a-chip systems for future drug discoveries. Although most organ-on-a-chip systems present proof-of-concept studies, miniaturized organ systems still need to demonstrate translational relevance and predictive power in clinical and pharmaceutical settings. This review explores whether microfluidic technology succeeded in paving the way for developing physiologically relevant human in vitro models for pharmacology and toxicology in biomedical research within the last decade. Individual organ-on-a-chip systems are discussed, focusing on relevant applications and highlighting their ability to tackle current challenges in pharmacological research.

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

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

PLGA Nanofiber/PDMS Microporous Composite Membrane-Sandwiched Microchip for Drug Testing

Lung-on-a-chip devices could provide new strategies for a biomimetic lung cell microenvironment and construction of lung disease models in vitro, and are expected to greatly promote the development of drug evaluation, toxicological detection, and disease model building. In this study, we developed a novel poly (lactic-co-glycolic acid) (PLGA) nanofiber/polydimethylsiloxane (PDMS) microporous composite membrane-sandwiched lung-on-a-chip to perform anti-tumor drug testing. The composite membrane was characterized, and the results showed that it was permeable to molecules and thus could be used to study small-molecule drug diffusion. In addition, the microchip could apply perfusion fluids to simulate blood flow under extremely low fluid shear stress, and could also simulate the spherical-like shape of the alveoli by deformation of the composite membrane. Using this chip, we evaluated the anti-tumor drug efficacy of gefitinib in two kinds of non-small cell lung cancer cells, the lung adenocarcinoma NCI-H1650 cell line and the large cell lung cancer NCI-H460 cell line. We further probed the resistance of NCI-H460 cells to gefitinib under normoxic and hypoxic conditions. The established composite membrane-sandwiched lung chip can simulate more biochemical and biophysical factors in the lung physiological and pathological microenvironment, and it has important applications in the personalized treatment of lung tumors. It is expected to play a potential role in clinical diagnosis and drug screening.

Gut-on-a-chip: Current progress and future opportunities

Organ-on-a-chip technology tries to mimic the complexity of native tissues in vitro. Important progress has recently been made in using this technology to study the gut with and without microbiota. These in vitro models can serve as an alternative to animal models for studying physiology, pathology, and pharmacology. While these models have greater physiological relevance than two-dimensional (2D) cell systems in vitro, endocrine and immunological functions in gut-on-a-chip models are still poorly represented. Furthermore, the construction of complex models, in which different cell types and structures interact, remains a challenge. Generally, gut-on-a-chip models have the potential to advance our understanding of the basic interactions found within the gut and lay the foundation for future applications in understanding pathophysiology, developing drugs, and personalizing medical treatments.

Organ-on-a-Chip

Limitations of the current tools used in the drug development process, cell cultures, and animal models have highlighted the need for a new powerful tool that can emulate the human physiology in vitro. Advances in the field of microfluidics have made the realization of this tool closer than ever. Organ-on-a-chip platforms have been the first step forward, leading to the combination and integration of multiple organ models in the same platform with human-on-a-chip being the ultimate goal. Despite the current progress and technological developments, there are still several unmet engineering and biological challenges curtailing their development and widespread application in the biomedical field. The potentials, challenges, and current work on this unprecedented tool are being discussed in this chapter.

Integrating Biophysics in Toxicology

Integration of biophysical stimulation in test systems is established in diverse branches of biomedical sciences including toxicology. This is largely motivated by the need to create novel experimental setups capable of reproducing more closely in vivo physiological conditions. Indeed, we face the need to increase predictive power and experimental output, albeit reducing the use of animals in toxicity testing. In vivo, mechanical stimulation is essential for cellular homeostasis. In vitro, diverse strategies can be used to model this crucial component. The compliance of the extracellular matrix can be tuned by modifying the stiffness or through the deformation of substrates hosting the cells via static or dynamic strain. Moreover, cells can be cultivated under shear stress deriving from the movement of the extracellular fluids. In turn, introduction of physical cues in the cell culture environment modulates differentiation, functional properties, and metabolic competence, thus influencing cellular capability to cope with toxic insults. This review summarizes the state of the art of integration of biophysical stimuli in model systems for toxicity testing, discusses future challenges, and provides perspectives for the further advancement of in vitro cytotoxicity studies.

Building upon current knowledge and techniques of indoor microbiology to construct the next era of theory into microorganisms, health, and the built environment

In the constructed habitat in which we spend up to 90% of our time, architectural design influences occupants' behavioral patterns, interactions with objects, surfaces, rituals, the outside environment, and each other. Within this built environment, human behavior and building design contribute to the accrual and dispersal of microorganisms; it is a collection of fomites that transfer microorganisms; reservoirs that collect biomass; structures that induce human or air movement patterns; and space types that encourage proximity or isolation between humans whose personal microbial clouds disperse cells into buildings. There have been recent calls to incorporate building microbiology into occupant health and exposure research and standards, yet the built environment is largely viewed as a repository for microorganisms which are to be eliminated, instead of a habitat which is inexorably linked to the microbial influences of building inhabitants. Health sectors have re-evaluated the role of microorganisms in health, incorporating microorganisms into prevention and treatment protocols, yet no paradigm shift has occurred with respect to microbiology of the built environment, despite calls to do so. Technological and logistical constraints often preclude our ability to link health outcomes to indoor microbiology, yet sufficient study exists to inform the theory and implementation of the next era of research and intervention in the built environment. This review presents built environment characteristics in relation to human health and disease, explores some of the current experimental strategies and interventions which explore health in the built environment, and discusses an emerging model for fostering indoor microbiology rather than fearing it.

Intervertebral disc organ culture for the investigation of disc pathology and regeneration - benefits, limitations, and future directions of bioreactors

Low back pain is the leading cause of disability worldwide and in many patients the source of pain can be attributed to pathological changes within the intervertebral disc (IVD). As present treatment options fail to address the underlying biological problem, novel therapies are currently subject to intense research. The physiologic IVD microenvironment features a highly complex interaction of biochemical and mechanical factors influencing cell metabolism and extracellular matrix turnover and is therefore difficult to simulate for research purposes on IVD pathology. The first whole organ culture models were not able to sufficiently replicate human in vivo conditions as mechanical loading, the predominant way of IVD nutrient supply and waste exchange, remained disregarded. To mimic the unique IVD niche more realistically, whole organ culture bioreactors have been developed, allowing for dynamic loading of IVDs and nutrient exchange. Recent advancements on bioreactor systems have facilitated whole organ culture of various IVDs for extended periods. IVD organ culture bioreactors have the potential to bridge the gap between in vitro and in vivo systems and thus may give valuable insights on IVD pathology and/or potential novel treatment approaches if the respective model is adjusted according to a well-defined research question. In this review, we outline the potential of currently utilized IVD bioreactor systems and present suggestions for further developments to more reliably investigate IVD biology and novel treatment approaches.

Critical assessment and integration of separate lines of evidence for risk assessment of chemical mixtures

Humans are exposed to multiple chemicals on a daily basis instead of to just a single chemical, yet the majority of existing toxicity data comes from single-chemical exposure. Multiple factors must be considered such as the route, concentration, duration, and the timing of exposure when determining toxicity to the organism. The need for adequate model systems (in vivo, in vitro, in silico and mathematical) is paramount for better understanding of chemical mixture toxicity. Currently, shortcomings plague each model system as investigators struggle to find the appropriate balance of rigor, reproducibility and appropriateness in mixture toxicity studies. Significant questions exist when comparing single-to mixture-chemical toxicity concerning additivity, synergism, potentiation, or antagonism. Dose/concentration relevance is a major consideration and should be subthreshold for better accuracy in toxicity assessment. Previous work was limited by the technology and methodology of the time, but recent advances have resulted in significant progress in the study of mixture toxicology. Novel technologies have added insight to data obtained from in vivo studies for predictive toxicity testing. These include new in vitro models: omics-related tools, organs-on-a-chip and 3D cell culture, and in silico methods. Taken together, all these modern methodologies improve the understanding of the multiple toxicity pathways associated with adverse outcomes (e.g., adverse outcome pathways), thus allowing investigators to better predict risks linked to exposure to chemical mixtures. As technology and knowledge advance, our ability to harness and integrate separate streams of evidence regarding outcomes associated with chemical mixture exposure improves. As many national and international organizations are currently stressing, studies on chemical mixture toxicity are of primary importance.

Precision-Cut Tissue Slices (PCTS) from the digestive gland of the Mediterranean mussel Mytilus galloprovincialis: An ex vivo approach for molecular and cellular responses in marine invertebrates

The precision-cut tissue slices (PCTS) represent a largely used biological model in mammalian research. This ex vivo approach offers the main advantages of in vitro systems, while maintaining the natural architecture of the tissue. The use of PCTS in toxicological research has been proposed for investigating the cellular effects of xenobiotics or bioactive compounds mostly in mammalian models. Their application is increasing also in marine organisms, but still limited to fish. This work validates the use of PCTS in an invertebrate species, the Mediterranean mussel Mytilus galloprovincialis. Intact tissue slices of different thicknesses (300, 350 and 400 μm) were successfully obtained from the digestive gland. The slices maintained the histological integrity and the viability after 6 h and 24 h incubation in culture medium, with some differences depending on the thickness. The enzymatic activities and mRNA levels of catalase and glutathione S-transferase, chosen as model biological endpoints, were measured until 24 h incubation, revealing the functionality of such systems. This work demonstrates the suitability of mussel PCTS for investigating molecular and cellular responses in ecotoxicological research.

Aerosol delivery into small anatomical airway model through spontaneous engineered breathing

Pulmonary administration is a noninvasive drug delivery method that, in contrast to systemic administration, reduces drug dosage and possible side effects. Numerous testing models, such as impingers and impactors, have previously been developed to evaluate the fate of inhaled drugs. However, such models are limited by the lack of information regarding several factors, such as pulmonary morphology and breathing motion, which are required to fully interpret actual inhaled-drug deposition profiles within the human respiratory tract. In this study, a spontaneous breathing-lung model that integrates branched morphology and deformable alveolar features was constructed using a multilayered fabrication technology to mimic the complex environment of the human lower respiratory tract. The developed model could emulate cyclic and spontaneous breathing motions to inhale and exhale aerosols generated by a nebulizer under diseaselike conditions. Results of this research demonstrate that aerosols (4.2 μm) could reach up to the deeper lung regions (generation 19 of the branched lung structure) within the obstructivelike model, whereas lesser penetration (generation 17) was observed when using the restrictivelike model. The proposed breathing-lung model can serve as a testing platform to provide a comprehensive understanding of the pharmacokinetics of pulmonary drugs within the lower lungs.

Monitoring of Microphysiological Systems: Integrating Sensors and Real-Time Data Analysis toward Autonomous Decision-Making

Microphysiological systems replicate human organ function and are promising technologies for discovery of translatable biomarkers, pharmaceuticals, and regenerative therapies. Because microphysiological systems require complex microscale anatomical structures and heterogeneous cell populations, a major challenge remains to manufacture and operate these products with reproducible and standardized function. In this Perspective, three stages of microphysiological system monitoring, including process, development, and function, are assessed. The unique features and remaining technical challenges for the required sensors are discussed. Monitoring of microphysiological systems requires nondestructive, continuous biosensors and imaging techniques. With such tools, the extent of cellular and tissue development, as well as function, can be autonomously determined and optimized by correlating physical and chemical sensor outputs with markers of physiological performance. Ultimately, data fusion and analyses across process, development, and function monitors can be implemented to adopt microphysiological systems for broad research and commercial applications.

Organoids-on-a-chip

Recent studies have demonstrated an array of stem cell-derived, self-organizing miniature organs, termed organoids, that replicate the key structural and functional characteristics of their in vivo counterparts. As organoid technology opens up new frontiers of research in biomedicine, there is an emerging need for innovative engineering approaches for the production, control, and analysis of organoids and their microenvironment. In this Review, we explore organ-on-a-chip technology as a platform to fulfill this need and examine how this technology may be leveraged to address major technical challenges in organoid research. We also discuss emerging opportunities and future obstacles for the development and application of organoid-on-a-chip technology.

Toxicological evaluation of airborne particulate matter. Are cell culture technologies ready to replace animal testing?

Exposure to atmospheric particulate matter (PM) can affect human health, causing asthma, atherosclerosis, renal disease and cancer. In the last few years, outdoor air pollution has increased globally, leading to a public health emergency. Epidemiological studies have reported a correlation between the development of severe respiratory and systemic diseases and exposure to PM. To evaluate the toxic effect of PM of different origins, conventional experimental toxicological investigations have been conducted in animals; however, animal experimentation poses major ethical issues and usually differs from human conditions. As an alternative, human cell cultures are increasingly being used to investigate cellular and molecular mechanisms of PM toxicity. Although 2D cell cultures have been proven helpful, they are far from being a valid alternative to animal tests. Recently, 3D cell culture and organ-on-chip technology have provided systems that are more complex and that can be more informative for toxicity studies. In this review, the results of the 2D systems that are most frequently used for PM toxicity evaluations are summarized with a special focus on their limitations. We also examined to which extent 3D cell culture and particularly the organ-on-chip technology may overcome these limitations and represent effective tools to improve airborne PM toxicity evaluations.

Biomimetic cardiovascular platforms for in vitro disease modeling and therapeutic validation

Bioengineered tissues have become increasingly more sophisticated owing to recent advancements in the fields of biomaterials, microfabrication, microfluidics, genetic engineering, and stem cell and developmental biology. In the coming years, the ability to engineer artificial constructs that accurately mimic the compositional, architectural, and functional properties of human tissues, will profoundly impact the therapeutic and diagnostic aspects of the healthcare industry. In this regard, bioengineered cardiac tissues are of particular importance due to the extremely limited ability of the myocardium to self-regenerate, as well as the remarkably high mortality associated with cardiovascular diseases worldwide. As novel microphysiological systems make the transition from bench to bedside, their implementation in high throughput drug screening, personalized diagnostics, disease modeling, and targeted therapy validation will bring forth a paradigm shift in the clinical management of cardiovascular diseases. Here, we will review the current state of the art in experimental in vitro platforms for next generation diagnostics and therapy validation. We will describe recent advancements in the development of smart biomaterials, biofabrication techniques, and stem cell engineering, aimed at recapitulating cardiovascular function at the tissue- and organ levels. In addition, integrative and multidisciplinary approaches to engineer biomimetic cardiovascular constructs with unprecedented human and clinical relevance will be discussed. We will comment on the implementation of these platforms in high throughput drug screening, in vitro disease modeling and therapy validation. Lastly, future perspectives will be provided on how these biomimetic platforms will aid in the transition towards patient centered diagnostics, and the development of personalized targeted therapeutics.

Cell-printed 3D liver-on-a-chip possessing a liver microenvironment and biliary system

To overcome the drawbacks of in vitro liver testing during drug development, numerous liver-on-a-chip models have been developed. However, current liver-on-a-chip technologies are labor-intensive, lack extracellular matrix (ECM) essential for liver cells, and lack a biliary system essential for excreting bile acids, which contribute to intestinal digestion but are known to be toxic to hepatocytes. Therefore, fabrication methods for development of liver-on-a-chip models that overcome the above limitations are required. Cell-printing technology enables construction of complex 3D structures with multiple cell types and biomaterials. We used cell-printing to develop a 3D liver-on-a-chip with multiple cell types for co-culture of liver cells, liver decellularized ECM bioink for a 3D microenvironment, and vascular/biliary fluidic channels for creating vascular and biliary systems. A chip with a biliary fluidic channel induced better biliary system creation and liver-specific gene expression and functions compared to a chip without a biliary system. Further, the 3D liver-on-a-chip showed better functionalities than 2D or 3D cultures. The chip was evaluated using acetaminophen and it showed an effective drug response. In summary, our results demonstrate that the 3D liver-on-a-chip we developed is promising in vitro liver test platform for drug discovery.

Proliferation characteristics of cells cultured under periodic versus static conditions

In vitro culture models have become an indispensable tool for assessing a vast variety of biological questions in many scientific fields. However, common in vitro cultures are maintained under static conditions, which do not reflect the in vivo situation and create a non-physiological environment. To assess whether the growth characteristics of cells cultured at pulsed-perfused versus static conditions differ, we observed the growth of differentially cultured cells in vitro by life-cell time-lapse imaging of recombinant HEK293^YFPI152L cells, stably expressing yellow fluorescent protein. Cells were grown for ~ 30 h at 37 °C and ambient CO₂ concentration in biochips mounted into a custom-designed 3D printed carrier and were imaged at a rate of ten images per hour using a fluorescence microscope with environment control infrastructure. Cells in one chip were maintained under static conditions whereas cells in another chip were recurrently perfused with fresh media. Generated image series were quantitatively analyzed using a custom-modified cell detection software. Imaging data averaged from four biological replicates per culturing condition demonstrate that cells cultured under conventional conditions exhibit an exponential growth rate. In contrast, cells cultured in periodic mode exhibited a non-exponential growth rate. Our data clearly indicate differential growth characteristics of cells cultured under periodic versus static conditions highlighting the impact of the culture conditions on the physiology of cells in vitro.

Kidney-on-a-chip: untapped opportunities

The organs-on-a-chip technology has shown strong promise in mimicking the complexity of native tissues in vitro and ex vivo, and recently significant advances have been made in applying this technology to studies of the kidney and its diseases. Individual components of the nephron, including the glomerulus, proximal tubule, and distal tubule/medullary collecting duct, have been successfully mimicked using organs-on-a-chip technology and yielding strong promises in advancing the field of ex vivo drug toxicity testing and augmenting renal replacement therapies. Although these models show promise over 2-dimensional cell systems in recapitulating important nephron features in vitro, nephron functions, such as tubular secretion, intracellular metabolism, and renin and vitamin D production, as well as prostaglandin synthesis are still poorly recapitulated in on-chip models. Moreover, construction of multiple-renal-components-on-a-chip models, in which various structures and cells of the renal system interact with each other, has remained a challenge. Overall, on-chip models show promise in advancing models of normal and pathological renal physiology, in predicting nephrotoxicity, and in advancing treatment of chronic kidney diseases.

Screening Estrogen Receptor Modulators in a Paper-Based Breast Cancer Model

The health risks associated with acute and prolonged exposure to estrogen receptor (ER) modulators has led to a concerted effort to identify and prioritize potential disruptors present in the environment. ER agonists and antagonists are identified with end-point assays, quantifying changes in cellular proliferation or gene transactivation in monolayers of estrogen receptor alpha expressing (ER+) cells upon exposure. While these monolayer cultures can be prepared, dosed, and analyzed in a highly parallelized manner, they are unable to predict the potencies of ER modulators in vivo accurately. Physiologically relevant model systems that better predict tissue- or organ-level responses are needed. To address this need, we describe here a screening platform capable of quantitatively assessing ER modulators in 96 chemically isolated 3D cultures. These cultures are supported in wax-patterned paper scaffolds whose design has improved performance and throughput over previously described paper-based setups. To highlight the potential of paper-based cultures for toxicity screens, we measured the potency of known ER modulators with a luciferase-based reporter assay. We also quantified the proliferation and invasion of two ER+ cell lines in the presence of estradiol. Despite the inability of the current setup to better predict in vivo potencies of ER modulators than monolayer cultures, the results demonstrate the potential of this platform to support increasingly complex and physiologically relevant tissue-like structures for environmental chemical risk assessment.

Medium throughput breathing human primary cell alveolus-on-chip model

Organs-on-chips have the potential to improve drug development efficiency and decrease the need for animal testing. For the successful integration of these devices in research and industry, they must reproduce in vivo contexts as closely as possible and be easy to use. Here, we describe a ‘breathing’ lung-on-chip array equipped with a passive medium exchange mechanism that provide an in vivo-like environment to primary human lung alveolar cells (hAEpCs) and primary lung endothelial cells. This configuration allows the preservation of the phenotype and the function of hAEpCs for several days, the conservation of the epithelial barrier functionality, while enabling simple sampling of the supernatant from the basal chamber. In addition, the chip design increases experimental throughput and enables trans-epithelial electrical resistance measurements using standard equipment. Biological validation revealed that human primary alveolar type I (ATI) and type II-like (ATII) epithelial cells could be successfully cultured on the chip over multiple days. Moreover, the effect of the physiological cyclic strain showed that the epithelial barrier permeability was significantly affected. Long-term co-culture of primary human lung epithelial and endothelial cells demonstrated the potential of the lung-on-chip array for reproducible cell culture under physiological conditions. Thus, this breathing lung-on-chip array, in combination with patients’ primary ATI, ATII, and lung endothelial cells, has the potential to become a valuable tool for lung research, drug discovery and precision medicine.

Engineered nanomaterial applications in perinatal therapeutics

Engineered nanomaterials (ENM) are widely used in commercial, domestic, and more recently biomedical applications. While the majority of exposures to ENM are unintentional, biomedical platforms are being evaluated for use in individualized and/or tissue-targeted therapies. Treatments are often avoided during prenatal periods to reduce adverse effects on the developing fetus. The placenta is central to maternal-fetal medicine. Perturbation of placental functions can limit transfer of necessary nutrients, alter production of hormones needed during pregnancy, or allow undesired passage of xenobiotics to the developing fetus. The development of therapeutics to target specific maternal, placental, or fetal tissues would be especially important to reduce or circumvent toxicities. Therefore, this review will discuss the potential use of ENM in perinatal medicine, the applicable physiochemical properties of ENM in therapeutic use, and current methodologies of ENM testing in perinatal medicine, and identify maternal, fetal, and offspring concerns associated with ENM exposure during gestation. As potential nanoparticle-based therapies continue to develop, so does the need for thorough consideration and evaluation for use in perinatal medicine.

Ecotoxicology Goes on a Chip: Embracing Miniaturized Bioanalysis in Aquatic Risk Assessment

Biological and environmental sciences are, more than ever, becoming highly dependent on technological and multidisciplinary approaches that warrant advanced analytical capabilities. Microfluidic lab-on-a-chip technologies are perhaps one the most groundbreaking offshoots of bioengineering, enabling design of an entirely new generation of bioanalytical instrumentation. They represent a unique approach to combine microscale engineering and physics with specific biological questions, providing technological advances that allow for fundamentally new capabilities in the spatiotemporal analysis of molecules, cells, tissues, and even small metazoan organisms. While these miniaturized analytical technologies experience an explosive growth worldwide, with a substantial promise of a direct impact on biosciences, it seems that lab-on-a-chip systems have so far escaped the attention of aquatic ecotoxicologists. In this Critical Review, potential applications of the currently existing and emerging chip-based technologies for aquatic ecotoxicology and water quality monitoring are highlighted. We also offer suggestions on how aquatic ecotoxicology can benefit from adoption of microfluidic lab-on-a-chip devices for accelerated bioanalysis.