Brain-on-a-chip Devices for Drug Screening and Disease Modeling Applications

Revolutionizing neurotherapeutics: blood-brain barrier-on-a-chip technologies for precise drug delivery

Introduction

The blood-brain barrier (BBB) is a critical neurovascular unit regulating substances' passage from the bloodstream to the brain. Its selective permeability poses significant challenges in drug delivery for neurological disorders. Conventional methods often fail due to the BBB's complex structure.

Aim

The study aims to shed light on their pivotal role in revolutionizing neurotherapeutics and explores the transformative potential of BBB-on-a-Chip technologies in drug delivery research to comprehensively review BBB-on-a-chip technologies, focusing on their design, and substantiate advantages over traditional models.

Methods

A detailed analysis of existing literature and experimental data pertaining to BBB-on-a-Chip technologies was conducted. Various models, their physiological relevance, and innovative design considerations were examined through databases like Scopus, EbscoHost, PubMed Central, and Medline. Case studies demonstrating enhanced drug transport through BBB-on-a-Chip models were also reviewed, highlighting their potential impact on neurological disorders.

Results

BBB-on-a-Chip models offer a revolutionary approach, accurately replicating BBB properties. These microphysiological systems enable high-throughput screening, real-time monitoring of drug transport, and precise localization of drugs. Case studies demonstrate their efficacy in enhancing drug penetration, offering potential therapies for diseases like Parkinson's and Alzheimer's.

Conclusion

BBB-on-a-Chip models represent a transformative milestone in drug delivery research. Their ability to replicate BBB complexities, offer real-time monitoring, and enhance drug transport holds immense promise for neurological disorders. Continuous research and development are imperative to unlock BBB-on-a-Chip models' full potential, ushering in a new era of targeted, efficient, and safer drug therapies for challenging neurological conditions.

Revolutionizing drug development: harnessing the potential of organ-on-chip technology for disease modeling and drug discovery

The inefficiency of existing animal models to precisely predict human pharmacological effects is the root reason for drug development failure. Microphysiological system/organ-on-a-chip technology (organ-on-a-chip platform) is a microfluidic device cultured with human living cells under specific organ shear stress which can faithfully replicate human organ-body level pathophysiology. This emerging organ-on-chip platform can be a remarkable alternative for animal models with a broad range of purposes in drug testing and precision medicine. Here, we review the parameters employed in using organ on chip platform as a plot mimic diseases, genetic disorders, drug toxicity effects in different organs, biomarker identification, and drug discoveries. Additionally, we address the current challenges of the organ-on-chip platform that should be overcome to be accepted by drug regulatory agencies and pharmaceutical industries. Moreover, we highlight the future direction of the organ-on-chip platform parameters for enhancing and accelerating drug discoveries and personalized medicine.

High-definition electroporation: Precise and efficient transfection on a microelectrode array

Intracellular delivery is critical for a plethora of biomedical applications, including mRNA transfection and gene editing. High transfection efficiency and low cytotoxicity, however, are often beyond the capabilities of bulk techniques and synonymous with extensive empirical optimization. Moreover, bulk techniques are not amenable to large screening applications. Here, we propose an expeditious workflow for achieving optimal electroporation-based intracellular delivery. Using the multiplexing ability of a high-definition microelectrode array (MEA) chip, we performed a sequence of carefully designed experiments, multiple linear regression modelling and validation to obtain optimal conditions for on-chip electroporation of primary fibroblasts. Five electric pulse parameters were varied to generate 32 different electroporation conditions. The effect of the parameters on cytotoxicity and intracellular delivery could be evaluated with just two experiments. Most successful electroporation conditions resulted in no cell death, highlighting the low cytotoxicity of on-chip electroporation. The resulting delivery models were then used to achieve dosage-controlled delivery of small molecules, delivery of Cas9-GFP single-guide RNA complexes and transfection with an mCherry-encoding mRNA, resulting in previously unreported high-efficiency, single-cell transfection on MEAs: cells expressed mCherry on 81% of the actuated electrodes, underscoring the vast potential of CMOS MEA technology for the transfection of primary cells.

Tissue-Engineered Models of the Human Brain: State-of-the-Art Analysis and Challenges

Neurological disorders affect billions of people across the world, making the discovery of effective treatments an important challenge. The evaluation of drug efficacy is further complicated because of the lack of in vitro models able to reproduce the complexity of the human brain structure and functions. Some limitations of 2D preclinical models of the human brain have been overcome by the use of 3D cultures such as cell spheroids, organoids and organs-on-chip. However, one of the most promising approaches for mimicking not only cell structure, but also brain architecture, is currently represented by tissue-engineered brain models. Both conventional (particularly electrospinning and salt leaching) and unconventional (particularly bioprinting) techniques have been exploited, making use of natural polymers or combinations between natural and synthetic polymers. Moreover, the use of induced pluripotent stem cells (iPSCs) has allowed the co-culture of different human brain cells (neurons, astrocytes, oligodendrocytes, microglia), helping towards approaching the central nervous system complexity. In this review article, we explain the importance of in vitro brain modeling, and present the main in vitro brain models developed to date, with a special focus on the most recent advancements in tissue-engineered brain models making use of iPSCs. Finally, we critically discuss achievements, main challenges and future perspectives.

Imaging Techniques: Essential Tools for the Study of SARS-CoV-2 Infection

The world has seen the emergence of a new virus in 2019, SARS-CoV-2, causing the COVID-19 pandemic and millions of deaths worldwide. Microscopy can be much more informative than conventional detection methods such as RT-PCR. This review aims to present the up-to-date microscopy observations in patients, the in vitro studies of the virus and viral proteins and their interaction with their host, discuss the microscopy techniques for detection and study of SARS-CoV-2, and summarize the reagents used for SARS-CoV-2 detection. From basic fluorescence microscopy to high resolution techniques and combined technologies, this article shows the power and the potential of microscopy techniques, especially in the field of virology.

Investigating the Interactions of Glioma Stem Cells in the Perivascular Niche at Single-Cell Resolution using a Microfluidic Tumor Microenvironment Model

The perivascular niche (PVN) is a glioblastoma tumor microenvironment (TME) that serves as a safe haven for glioma stem cells (GSCs), and acts as a reservoir that inevitably leads to tumor recurrence. Understanding cellular interactions in the PVN that drive GSC treatment resistance and stemness is crucial to develop lasting therapies for glioblastoma. The limitations of in vivo models and in vitro assays have led to critical knowledge gaps regarding the influence of various cell types in the PVN on GSCs behavior. This study developed an organotypic triculture microfluidic model as a means to recapitulate the PVN and study its impact on GSCs. This triculture platform, comprised of endothelial cells (ECs), astrocytes, and GSCs, is used to investigate GSC invasion, proliferation and stemness. Both ECs and astrocytes significantly increased invasiveness of GSCs. This study futher identified 15 ligand-receptor pairs using single-cell RNAseq with putative chemotactic mechanisms of GSCs, where the receptor is up-regulated in GSCs and the diffusible ligand is expressed in either astrocytes or ECs. Notably, the ligand-receptor pair SAA1-FPR1 is demonstrated to be involved in chemotactic invasion of GSCs toward PVN. The novel triculture platform presented herein can be used for therapeutic development and discovery of molecular mechanisms driving GSC biology.

Dual effect of TAT functionalized DHAH lipid nanoparticles with neurotrophic factors in human BBB and microglia cultures

Background

Neurodegenerative diseases (NDs) are an accelerating global health problem. Nevertheless, the stronghold of the brain- the blood–brain barrier (BBB) prevents drug penetrance and dwindles effective treatments. Therefore, it is crucial to identify Trojan horse-like drug carriers that can effectively cross the blood–brain barrier and reach the brain tissue. We have previously developed polyunsaturated fatty acids (PUFA)-based nanostructured lipid carriers (NLC), namely DHAH-NLC. These carriers are modulated with BBB-permeating compounds such as chitosan (CS) and trans-activating transcriptional activator (TAT) from HIV-1 that can entrap neurotrophic factors (NTF) serving as nanocarriers for NDs treatment. Moreover, microglia are suggested as a key causative factor of the undergoing neuroinflammation of NDs. In this work, we used in vitro models to investigate whether DHAH-NLCs can enter the brain via the BBB and investigate the therapeutic effect of NTF-containing DHAH-NLC and DHAH-NLC itself on lipopolysaccharide-challenged microglia.

Methods

We employed human induced pluripotent stem cell-derived brain microvascular endothelial cells (BMECs) to capitalize on the in vivo-like TEER of this BBB model and quantitatively assessed the permeability of DHAH-NLCs. We also used the HMC3 microglia cell line to assess the therapeutic effect of NTF-containing DHAH-NLC upon LPS challenge.

Results

TAT-functionalized DHAH-NLCs successfully crossed the in vitro BBB model, which exhibited high transendothelial electrical resistance (TEER) values (≈3000 Ω*cm²). Specifically, the TAT-functionalized DHAH-NLCs showed a permeability of up to 0.4% of the dose. Furthermore, using human microglia (HMC3), we demonstrate that DHAH-NLCs successfully counteracted the inflammatory response in our cultures after LPS challenge. Moreover, the encapsulation of glial cell-derived neurotrophic factor (GNDF)-containing DHAH-NLCs (DHAH-NLC-GNDF) activated the Nrf2/HO-1 pathway, suggesting the triggering of the endogenous anti-oxidative system present in microglia.

Conclusions

Overall, this work shows that the TAT-functionalized DHAH-NLCs can cross the BBB, modulate immune responses, and serve as cargo carriers for growth factors; thus, constituting an attractive and promising novel drug delivery approach for the transport of therapeutics through the BBB into the brain.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-022-00315-1.

The Future of 3D Brain Cultures in Developmental Neurotoxicity Testing

Human brain is undoubtedly the most complex organ in the body. Thus, it is difficult to develop adequate and at the same time human relevant test systems and models to cover the aspects of brain homeostasis and even more challenging to address brain development. Animal tests for Developmental Neurotoxicity (DNT) have been devised, but because of complex underlying mechanisms of neural development, and interspecies differences, there are many limitations of animal-based approaches. The high costs, high number of animals used per test and technical difficulties of these tests are prohibitive for routine DNT chemical screening. Therefore, many potential DNT chemicals remain unidentified. New approach methodologies (NAMs) are needed to change this. Experts in the field have recommended the use of a battery of human in vitro tests to be used for the initial prioritization of high-risk environmental chemicals for DNT testing. Microphysiological systems (MPS) of the brain mimic the in vivo counterpart in terms of cellular composition, recapitulation of regional architecture and functionality. These systems amendable to use in a DNT test battery with promising features such as (i) complexity, (ii) closer recapitulation of in vivo response and (iii) possibility to multiplex many assays in one test system, which can increase throughput and predictivity for human health. The resent progress in 3D brain MPS research, advantages, limitations and future perspectives are discussed in this review.

A Three-Dimensional Brain-on-a-Chip Using Human iPSC-Derived GABAergic Neurons and Astrocytes

Brain-on-a-chip is a miniaturized engineering platform to mimic the structural and functional aspects of brain tissue. We describe a method to construct a three-dimensional (3D) brain-on-a-chip in this chapter. We firstly portray the method of a brain-on-a-chip model with cocultured mice neurons, microglia, and astrocytes to mimic brain tissue and membrane-free perfusion with endothelial cells, in which we successfully build the blood-brain barrier to screen neurotoxicity. Then we describe a method to construct a brain-on-a-chip with human induced pluripotent stem cell (iPSC)-derived neurons and astrocytes to simulate human brain behavior. This platform consists of neuronal tissue with extracellular matrix (ECM)-embedded GABAergic neurons and astrocytes and a perfusion channel with dynamic flow. We also include the broader applicability test of this model using an organophosphate (OP), malathion, to induce acute and chronic neurotoxicity, and then using butyrylcholinesterase (BuChE) as an exogenous bioscavenger of OP. Following the methods listed in this chapter, we are able to measure the neurotoxic effects on construct integrity, viability, and total AChE and BuChE activity.

Modelling Human Physiology on-Chip: Historical Perspectives and Future Directions

For centuries, animal experiments have contributed much to our understanding of mechanisms of human disease, but their value in predicting the effectiveness of drug treatments in the clinic has remained controversial. Animal models, including genetically modified ones and experimentally induced pathologies, often do not accurately reflect disease in humans, and therefore do not predict with sufficient certainty what will happen in humans. Organ-on-chip (OOC) technology and bioengineered tissues have emerged as promising alternatives to traditional animal testing for a wide range of applications in biological defence, drug discovery and development, and precision medicine, offering a potential alternative. Recent technological breakthroughs in stem cell and organoid biology, OOC technology, and 3D bioprinting have all contributed to a tremendous progress in our ability to design, assemble and manufacture living organ biomimetic systems that more accurately reflect the structural and functional characteristics of human tissue in vitro, and enable improved predictions of human responses to drugs and environmental stimuli. Here, we provide a historical perspective on the evolution of the field of bioengineering, focusing on the most salient milestones that enabled control of internal and external cell microenvironment. We introduce the concepts of OOCs and Microphysiological systems (MPSs), review various chip designs and microfabrication methods used to construct OOCs, focusing on blood-brain barrier as an example, and discuss existing challenges and limitations. Finally, we provide an overview on emerging strategies for 3D bioprinting of MPSs and comment on the potential role of these devices in precision medicine.

Brain-on-a-Chip: Characterizing the next generation of advanced in vitro platforms for modeling the central nervous system

The complexity of the human brain creates significant, almost insurmountable challenges for neurological drug development. Advanced in vitro platforms are increasingly enabling researchers to overcome these challenges, by mimicking key features of the brain's composition and functionality. Many of these platforms are called "Brains-on-a-Chip"-a term that was originally used to refer to microfluidics-based systems containing miniature engineered tissues, but that has since expanded to describe a vast range of in vitro central nervous system (CNS) modeling approaches. This Perspective seeks to refine the definition of a Brain-on-a-Chip for the next generation of in vitro platforms, identifying criteria that determine which systems should qualify. These criteria reflect the extent to which a given platform overcomes the challenges unique to in vitro CNS modeling (e.g., recapitulation of the brain's microenvironment; inclusion of critical subunits, such as the blood-brain barrier) and thereby provides meaningful added value over conventional cell culture systems. The paper further outlines practical considerations for the development and implementation of Brain-on-a-Chip platforms and concludes with a vision for where these technologies may be heading.

Degenerative disease-on-a-chip: Developing microfluidic models for rapid availability of newer therapies

BACKGROUND

Understanding the pathophysiology of degenerative diseases pertaining to nervous system, ocular region, bone/cartilage and muscle are still being comprehended, thus delaying the availability of targeted therapies.

PURPOSE AND SCOPE

Newer micro-physiological systems (organ-on-chip technology) involves development of more sophisticated devices, modelling a range of in vitro human tissues and an array of models for diseased conditions. These models expand opportunities for high throughput screening (HTS) of drugs and are likely to be rapid and cost-effective, thus reducing extensive usage of animal models.

CONCLUSION

Through this review article, we aim to present an overview of the degenerative disease models that are presently being developed using microfluidic platforms with the aim of mimicking in vivo tissue physiology and micro-architecture. The manuscript provides an overview of the degenerative disease models and their potential for testing and screening of possible biotherapeutic molecules and drugs. It highlights the perspective of the regulatory bodies with respect to the established-on chip models and thereby enhancing its translational potential. This article is protected by copyright. All rights reserved.

On the road to the brain-on-a-chip: a review on strategies, methods, and applications

The brain is the most complex organ of our body. Such a complexity spans from the single-cell morphology up to the intricate connections that hundreds of thousands of neurons establish to create dense neuronal networks. All these components are involved in the genesis of the rich patterns of electrophysiological activity that characterize the brain. Over the years, researchers coming from different disciplines developedin vitrosimplified experimental models to investigate in a more controllable and observable way how neuronal ensembles generate peculiar firing rhythms, code external stimulations, or respond to chemical drugs. Nowadays, suchin vitromodels are namedbrain-on-a-chippointing out the relevance of the technological counterpart as artificial tool to interact with the brain: multi-electrode arrays are well-used devices to record and stimulate large-scale developing neuronal networks originated from dissociated cultures, brain slices, up to brain organoids. In this review, we will discuss the state of the art of the brain-on-a-chip, highlighting which structural and biological features a realisticin vitrobrain should embed (and how to achieve them). In particular, we identified two topological features, namely modular and three-dimensional connectivity, and a biological one (heterogeneity) that takes into account the huge number of neuronal types existing in the brain. At the end of this travel, we will show how 'far' we are from the goal and how interconnected-brain-regions-on-a-chip is the most appropriate wording to indicate the current state of the art.

Lab-on-a-Chip Platforms as Tools for Drug Screening in Neuropathologies Associated with Blood-Brain Barrier Alterations

Lab-on-a-chip (LOC) and organ-on-a-chip (OOC) devices are highly versatile platforms that enable miniaturization and advanced controlled laboratory functions (i.e., microfluidics, advanced optical or electrical recordings, high-throughput screening). The manufacturing advancements of LOCs/OOCs for biomedical applications and their current limitations are briefly discussed. Multiple studies have exploited the advantages of mimicking organs or tissues on a chip. Among these, we focused our attention on the brain-on-a-chip, blood-brain barrier (BBB)-on-a-chip, and neurovascular unit (NVU)-on-a-chip applications. Mainly, we review the latest developments of brain-on-a-chip, BBB-on-a-chip, and NVU-on-a-chip devices and their use as testing platforms for high-throughput pharmacological screening. In particular, we analyze the most important contributions of these studies in the field of neurodegenerative diseases and their relevance in translational personalized medicine.

One Brain-All Cells: A Comprehensive Protocol to Isolate All Principal CNS-Resident Cell Types from Brain and Spinal Cord of Adult Healthy and EAE Mice

In experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, the role of each central nervous system (CNS)-resident cell type during inflammation, neurodegeneration, and remission has been frequently addressed. Although protocols for the isolation of different individual CNS-resident cell types exist, none can harvest all of them within a single experiment. In addition, isolation of individual cells is more demanding in adult mice and even more so from the inflamed CNS. Here, we present a protocol for the simultaneous purification of viable single-cell suspensions of all principal CNS-resident cell types (microglia, oligodendrocytes, astrocytes, and neurons) from adult mice-applicable in healthy mice as well as in EAE. After dissociation of the brain and spinal cord from adult mice, microglia, oligodendrocytes, astrocytes and, neurons were isolated via magnetic-activated cell sorting (MACS). Validations comprised flow cytometry, immunocytochemistry, as well as functional analyses (immunoassay and Sholl analysis). The purity of each cell isolation averaged 90%. All cells displayed cell-type-specific morphologies and expressed specific surface markers. In conclusion, this new protocol for the simultaneous isolation of all major CNS-resident cell types from one CNS offers a sophisticated and comprehensive way to investigate complex cellular networks ex vivo and simultaneously reduce mice numbers to be sacrificed.

Drug delivery and targeting to brain tumors: considerations for crossing the blood-brain barrier

Introduction: The blood-brain barrier (BBB) selectively impedes the transportation of drug molecules into the brain, which makes the drug delivery and targeting of brain tumors very challenging.Areas covered: Having surveyed the recent literature, comprehensive insights are given into the impacts of the BBB on the advanced drug delivery and targeting modalities for brain tumors.Expert opinion: Brain capillary endothelial cells form the BBB in association with astrocytes, pericytes, neurons, and extracellular matrix. Coop of these forms the complex setting of neurovascular unite. The BBB maintains the brain homeostasis by restrictive controlling of the blood circulating nutrients/substances trafficking. Despite substantial progress on therapy of brain tumors, there is no impeccable strategy to safely deliver chemotherapeutics into the brain. Various strategies have been applied to deliver chemotherapeutics into the brain (e.g. BBB opening, direct delivery by infusion, injection, microdialysis, and implants, and smart nanosystems), which hold different pros and cons. Of note, smart nanoscale multifunctional nanomedicines can serve as targeting, imaging, and treatment modality for brain tumors. Given that aggressive brain tumors (e.g. gliomas) are often unresponsive to any treatments, an in-depth understanding of the molecular/cellular complexity of brain tumors might help the development of smart and effective treatment modalities.

Refining Host-Pathogen Interactions: Organ-on-Chip Side of the Coin

Bioinspired organ-level in vitro platforms that recapitulate human organ physiology and organ-specific responses have emerged as effective technologies for infectious disease research, drug discovery, and personalized medicine. A major challenge in tissue engineering for infectious diseases has been the reconstruction of the dynamic 3D microenvironment reflecting the architectural and functional complexity of the human body in order to more accurately model the initiation and progression of host-microbe interactions. By bridging the gap between in vitro experimental models and human pathophysiology and providing alternatives for animal models, organ-on-chip microfluidic devices have so far been implemented in multiple research areas, contributing to major advances in the field. Given the emergence of the recent pandemic, plug-and-play organ chips may hold the key for tackling an unmet clinical need in the development of effective therapeutic strategies. In this review, latest studies harnessing organ-on-chip platforms to unravel host-pathogen interactions are presented to highlight the prospects for the microfluidic technology in infectious diseases research.

Gaining Micropattern Fidelity in an NOA81 Microsieve Laser Ablation Process

We studied the micropattern fidelity of a Norland Optical Adhesive 81 (NOA81) microsieve made by soft-lithography and laser micromachining. Ablation opens replicated cavities, resulting in three-dimensional (3D) micropores. We previously demonstrated that microsieves can capture cells by passive pumping. Flow, capture yield, and cell survival depend on the control of the micropore geometry and must yield high reproducibility within the device and from device to device. We investigated the NOA81 film thickness, the laser pulse repetition rate, the number of pulses, and the beam focusing distance. For NOA81 films spin-coated between 600 and 1200 rpm, the pulse number controls the breaching of films to form the pore’s aperture and dominates the process. Pulse repetition rates between 50 and 200 Hz had no observable influence. We also explored laser focal plane to substrate distance to find the most effective ablation conditions. Scanning electron micrographs (SEM) of focused ion beam (FIB)-cut cross sections of the NOA81 micropores and inverted micropore copies in polydimethylsiloxane (PDMS) show a smooth surface topology with minimal debris. Our studies reveal that the combined process allows for a 3D micropore quality from device to device with a large enough process window for biological studies.

Phytohormone Abscisic Acid Improves Memory Impairment and Reduces Neuroinflammation in 5xFAD Mice by Upregulation of LanC-Like Protein 2

Alzheimer's disease (AD), a type of dementia, is the most common neurodegenerative disease in the elderly. Neuroinflammation caused by deposition of amyloid β (Aβ) is one of the most important pathological causes in AD. The isoprenoid phytohormone abscisic acid (ABA) has recently been found in mammals and was shown to be an endogenous hormone, acting in stress conditions. Although ABA has been associated with anti-inflammatory effects and reduced cognitive impairment in several studies, the mechanisms of ABA in AD has not been ascertained clearly. To investigate the clearance of Aβ and anti-inflammatory effects of ABA, we used quantitative real-time polymerase chain reaction and immunoassay. ABA treatment inhibited Aβ deposition and neuroinflammation, thus resulting in improvement of memory impairment in 5xFAD mice. Interestingly, these effects were not associated with activation of peroxisome proliferator-activated receptor gamma, well known as a molecular target of ABA, but related with modulation of the LanC-like protein 2 (LANCL2), known as a receptor of ABA. Taken together, our results indicate that ABA reduced Aβ deposition, neuroinflammation, and memory impairment, which is the most characteristic pathology of AD, via the upregulation of LANCL2. These data suggest that ABA might be a candidate for therapeutics for AD treatment.

Patient-Derived Induced Pluripotent Stem Cell-Based Models in Parkinson's Disease for Drug Identification

Parkinson's disease (PD) is a common progressive neurodegenerative disorder characterized by loss of striatal-projecting dopaminergic neurons of the ventral forebrain, resulting in motor and cognitive deficits. Despite extensive efforts in understanding PD pathogenesis, no disease-modifying drugs exist. Recent advances in cell reprogramming technologies have facilitated the generation of patient-derived models for sporadic or familial PD and the identification of early, potentially triggering, pathological phenotypes while they provide amenable systems for drug discovery. Emerging developments highlight the enhanced potential of using more sophisticated cellular systems, including neuronal and glial co-cultures as well as three-dimensional systems that better simulate the human pathophysiology. In combination with high-throughput high-content screening technologies, these approaches open new perspectives for the identification of disease-modifying compounds. In this review, we discuss current advances and the challenges ahead in the use of patient-derived induced pluripotent stem cells for drug discovery in PD. We address new concepts implicating non-neuronal cells in disease pathogenesis and highlight the necessity for functional assays, such as calcium imaging and multi-electrode array recordings, to predict drug efficacy. Finally, we argue that artificial intelligence technologies will be pivotal for analysis of the large and complex data sets obtained, becoming game-changers in the process of drug discovery.

Alzheimer's Disease, and Breast and Prostate Cancer Research: Translational Failures and the Importance to Monitor Outputs and Impact of Funded Research

Dementia and cancer are becoming increasingly prevalent in Western countries. In the last two decades, research focused on Alzheimer's disease (AD) and cancer, in particular, breast cancer (BC) and prostate cancer (PC), has been substantially funded both in Europe and worldwide. While scientific research outcomes have contributed to increase our understanding of the disease etiopathology, still the prevalence of these chronic degenerative conditions remains very high across the globe. By definition, no model is perfect. In particular, animal models of AD, BC, and PC have been and still are traditionally used in basic/fundamental, translational, and preclinical research to study human disease mechanisms, identify new therapeutic targets, and develop new drugs. However, animals do not adequately model some essential features of human disease; therefore, they are often unable to pave the way to the development of drugs effective in human patients. The rise of new technological tools and models in life science, and the increasing need for multidisciplinary approaches have encouraged many interdisciplinary research initiatives. With considerable funds being invested in biomedical research, it is becoming pivotal to define and apply indicators to monitor the contribution to innovation and impact of funded research. Here, we discuss some of the issues underlying translational failure in AD, BC, and PC research, and describe how indicators could be applied to retrospectively measure outputs and impact of funded biomedical research.

Human Organs-on-Chips for Virology

While conventional in vitro culture systems and animal models have been used to study the pathogenesis of viral infections and to facilitate development of vaccines and therapeutics for viral diseases, models that can accurately recapitulate human responses to infection are still lacking. Human organ-on-a-chip (Organ Chip) microfluidic culture devices that recapitulate tissue–tissue interfaces, fluid flows, mechanical cues, and organ-level physiology have been developed to narrow the gap between in vitro experimental models and human pathophysiology. Here, we describe how recent developments in Organ Chips have enabled re-creation of complex pathophysiological features of human viral infections in vitro.

Microfluidic Organ Chip culture devices are emerging alternatives to conventional in vitro and animal models due to their ability to replicate many structural and functional features of human physiology and disease states.

Recent innovations demonstrate that Organ Chip technology is a promising strategy for virology studies where there have been successes in reproducing various viral disease phenotypes.

Organ Chips have enabled investigation of many aspects of viral infection, including virus–host interactions, viral therapy-resistance evolution, and development of new antiviral therapeutics, as well as underlying pathogenesis.

As Organ Chip-based assays provide accessibility to study virus-induced diseases in real time and at high resolution, they can open new avenues to uncover viral pathogenesis in a human-relevant environment and may eventually enable development of novel therapeutics and vaccines.

Novel Strategies in Artificial Organ Development: What Is the Future of Medicine?

The technology of tissue engineering is a rapidly evolving interdisciplinary field of science that elevates cell-based research from 2D cultures through organoids to whole bionic organs. 3D bioprinting and organ-on-a-chip approaches through generation of three-dimensional cultures at different scales, applied separately or combined, are widely used in basic studies, drug screening and regenerative medicine. They enable analyses of tissue-like conditions that yield much more reliable results than monolayer cell cultures. Annually, millions of animals worldwide are used for preclinical research. Therefore, the rapid assessment of drug efficacy and toxicity in the early stages of preclinical testing can significantly reduce the number of animals, bringing great ethical and financial benefits. In this review, we describe 3D bioprinting techniques and first examples of printed bionic organs. We also present the possibilities of microfluidic systems, based on the latest reports. We demonstrate the pros and cons of both technologies and indicate their use in the future of medicine.

Multiscale brain research on a microfluidic chip

One major challenge in current brain research is generating an integrative understanding of the brain's functions and disorders from its multiscale neuronal architectures and connectivity. Thus, innovative neurotechnology tools are urgently required for deciphering the multiscale functional and structural organizations of the brain at hierarchical scales from the molecular to the organismal level by multiple brain research initiatives launched by the European Union, United States, Australia, Canada, China, Korea, and Japan. To meet this demand, microfluidic chips (μFCs) have rapidly evolved as a trans-scale neurotechnological toolset to enable multiscale studies of the brain due to their unique advantages in flexible microstructure design, multifunctional integration, accurate microenvironment control, and capacity for automatic sample processing. Here, we review the recent progress in applying innovative μFC-based neuro-technologies to promote multiscale brain research and uniquely focus on representative applications of μFCs to address challenges in brain research at each hierarchical level. We discuss the current trend of combinational applications of μFCs with other neuro- and biotechnologies, including optogenetics, brain organoids, and 3D bioprinting, for better multiscale brain research. In addition, we offer our insights into the existing outstanding questions at each hierarchical level of brain research that could potentially be addressed by advancing microfluidic techniques. This review will serve as a timely guide for bioengineers and neuroscientists to develop and apply μFC-based neuro-technologies for promoting basic and translational brain research.

The Fabrication and Application Mechanism of Microfluidic Systems for High Throughput Biomedical Screening: A Review

Microfluidic systems have been widely explored based on microfluidic technology, and it has been widely used for biomedical screening. The key parts are the fabrication of the base scaffold, the construction of the matrix environment in the 3D system, and the application mechanism. In recent years, a variety of new materials have emerged, meanwhile, some new technologies have been developed. In this review, we highlight the properties of high throughput and the biomedical application of the microfluidic chip and focus on the recent progress of the fabrication and application mechanism. The emergence of various biocompatible materials has provided more available raw materials for microfluidic chips. The material is not confined to polydimethylsiloxane (PDMS) and the extracellular microenvironment is not limited by a natural matrix. The mechanism is also developed in diverse ways, including its special physical structure and external field effects, such as dielectrophoresis, magnetophoresis, and acoustophoresis. Furthermore, the cell/organ-based microfluidic system provides a new platform for drug screening due to imitating the anatomic and physiologic properties in vivo. Although microfluidic technology is currently mostly in the laboratory stage, it has great potential for commercial applications in the future.

Microfluidic Brain-on-a-Chip: Perspectives for Mimicking Neural System Disorders

Neurodegenerative diseases (NDDs) include more than 600 types of nervous system disorders in humans that impact tens of millions of people worldwide. Estimates by the World Health Organization (WHO) suggest NDDs will increase by nearly 50% by 2030. Hence, development of advanced models for research on NDDs is needed to explore new therapeutic strategies and explore the pathogenesis of these disorders. Different approaches have been deployed in order to investigate nervous system disorders, including two-and three-dimensional (2D and 3D) cell cultures and animal models. However, these models have limitations, such as lacking cellular tension, fluid shear stress, and compression analysis; thus, studying the biochemical effects of therapeutic molecules on the biophysiological interactions of cells, tissues, and organs is problematic. The microfluidic "organ-on-a-chip" is an inexpensive and rapid analytical technology to create an effective tool for manipulation, monitoring, and assessment of cells, and investigating drug discovery, which enables the culture of various cells in a small amount of fluid (10-9 to 10-18 L). Thus, these chips have the ability to overcome the mentioned restrictions of 2D and 3D cell cultures, as well as animal models. Stem cells (SCs), particularly neural stem cells (NSCs), induced pluripotent stem cells (iPSCs), and embryonic stem cells (ESCs) have the capability to give rise to various neural system cells. Hence, microfluidic organ-on-a-chip and SCs can be used as potential research tools to study the treatment of central nervous system (CNS) and peripheral nervous system (PNS) disorders. Accordingly, in the present review, we discuss the latest progress in microfluidic brain-on-a-chip as a powerful and advanced technology that can be used in basic studies to investigate normal and abnormal functions of the nervous system.

3D cell culture models and organ-on-a-chip: Meet separation science and mass spectrometry

In vitro derived simplified 3D representations of human organs or organ functionalities are predicted to play a major role in disease modeling, drug development, and personalized medicine, as they complement traditional cell line approaches and animal models. The cells for 3D organ representations may be derived from primary tissues, embryonic stem cells or induced pluripotent stem cells and come in a variety of formats from aggregates of individual or mixed cell types, self-organizing in vitro developed "organoids" and tissue mimicking chips. Microfluidic devices that allow long-term maintenance and combination with other tissues, cells or organoids are commonly referred to as "microphysiological" or "organ-on-a-chip" systems. Organ-on-a-chip technology allows a broad range of "on-chip" and "off-chip" analytical techniques, whereby "on-chip" techniques offer the possibility of real time tracking and analysis. In the rapidly expanding tool kit for real time analytical assays, mass spectrometry, combined with "on-chip" electrophoresis, and other separation approaches offer attractive emerging tools. In this review, we provide an overview of current 3D cell culture models, a compendium of current analytical strategies, and we make a case for new approaches for integrating separation science and mass spectrometry in this rapidly expanding research field.