A Biomimetic Microfluidic Tumor Microenvironment Platform Mimicking the EPR Effect for Rapid Screening of Drug Delivery Systems

Development and validation of a controlled heating apparatus for long-term MRI of 3D microfluidic tumor models

Conventional testing of novel contrast agents for magnetic resonance imaging (MRI) involves cell and animal studies. However, 2D cultures lack dynamic flow and in vivo MRI is limited by regulatory approval of long-term anesthesia use. Microfluidic tumor models (MTMs) offer a cost-effective, reproducible, and high throughput platform for bridging cell and animal models. Yet, MRI of microfluidic devices is challenging, due to small fluid volumes generating low sensitivity. For the first time, an MRI of MTMs was performed at low field strength (1 T) using conventional imaging equipment without microcoils. To enable longitudinal MRI, we developed (1) CHAMP-3 (controlled heating apparatus for microfluidics and portability) which heats MTMs during MRI scans and (2) an MRI-compatible temperature monitoring system. CHAMP-3 maintained chip surface temperature at ~37°C and the media inside at ~35.5°C. Enhanced T1-weighted MRI contrast was achieved in 3D MTMs with free manganese (Mn2+) solutions and Mn2+ labeled tumor cells.

Functional Integration of Synthetic Cells into 3D Microfluidic Devices for Artificial Organ-On-Chip Technologies

Microfluidics plays a pivotal role in organ-on-chip technologies and in the study of synthetic cells, especially in the development and analysis of artificial cell models. However, approaches that use synthetic cells as integral functional components for microfluidic systems to shape the microenvironment of natural living cells cultured on-chip are not explored. Here, colloidosome-based synthetic cells are integrated into 3D microfluidic devices, pioneering the concept of synthetic cell-based microenvironments for organs-on-chip. Methods are devised to create dense and stable networks of silica colloidosomes, enveloped by supported lipid bilayers, within microfluidic channels. These networks promote receptor-ligand interactions with on-chip cultured cells. Furthermore, a technique is introduced for the controlled release of growth factors from the synthetic cells into the channels, using a calcium alginate-based hydrogel formation within the colloidosomes. To demonstrate the potential of the technology, a modular plug-and-play lymph-node-on-a-chip prototype that guides the expansion of primary human T cells by stimulating receptor ligands on the T cells and modulating their cytokine environment is presented. This integration of synthetic cells into microfluidic systems offers a new direction for organ-on-chip technologies and suggests further avenues for exploration in potential therapeutic applications.

Investigation of tumour environments through advancements in microtechnology and nanotechnology

Cancer has a significant negative social and economic impact on both developed and developing countries. As a result, understanding the onset and progression of cancer is critical for developing therapies that can improve the well-being and health of individuals with cancer. With time, study has revealed, the tumor microenvironment has great influence on this process. Micro and nanoscale engineering techniques can be used to study the tumor microenvironment. Nanoscale and Microscale engineering use Novel technologies and designs with small dimensions to recreate the TME. Knowing how cancer cells interact with one another can help researchers develop therapeutic approaches that anticipate and counteract cancer cells' techniques for evading detection and fighting anti-cancer treatments, such as microfabrication techniques, microfluidic devices, nanosensors, and nanodevices used to study or recreate the tumor microenvironment. Nevertheless, a complicated action just like the growth and in cancer advancement, and their intensive association along the environment around it that has to be studied in more detail.

Tumor-On-A-Chip Models for Predicting In Vivo Nanoparticle Behavior

Nanosized drug formulations are broadly explored for the improvement of cancer therapy. Prediction of in vivo nanoparticle (NP) behavior, however, is challenging, given the complexity of the tumor and its microenvironment. Microfluidic tumor-on-a-chip models are gaining popularity for the in vitro testing of nanoparticle targeting under conditions that simulate the 3D tumor (microenvironment). In this review, following a description of the tumor microenvironment (TME), the state of the art regarding tumor-on-a-chip models for investigating nanoparticle delivery to solid tumors is summarized. The models are classified based on the degree of compartmentalization (single/multi-compartment) and cell composition (tumor only/tumor microenvironment). The physiological relevance of the models is critically evaluated. Overall, microfluidic tumor-on-a-chip models greatly improve the simulation of the TME in comparison to 2D tissue cultures and static 3D spheroid models and contribute to the understanding of nanoparticle behavior. Interestingly, two interrelated aspects have received little attention so far which are the presence and potential impact of a protein corona as well as nanoparticle uptake through phagocytosing cells. A better understanding of their relevance for the predictive capacity of tumor-on-a-chip systems and development of best practices will be a next step for the further refinement of advanced in vitro tumor models.

Vascularized tumor models for the evaluation of drug delivery systems: a paradigm shift

As the conversion rate of preclinical studies for cancer treatment is low, user-friendly models that mimic the pathological microenvironment and drug intake with high throughput are scarce. Animal models are key, but an alternative to reduce their use would be valuable. Vascularized tumor-on-chip models combine great versatility with scalable throughput and are easy to use. Several strategies to integrate both tumor and vascular compartments have been developed, but few have been used to assess drug delivery. Permeability, intra/extravasation, and free drug circulation are often evaluated, but imperfectly recapitulate the processes at stake. Indeed, tumor targeting and chemoresistance bypass must be investigated to design promising cancer therapeutics. In vitro models that would help the development of drug delivery systems (DDS) are thus needed. They would allow selecting good candidates before animal studies based on rational criteria such as drug accumulation, diffusion in the tumor, and potency, as well as absence of side damage. In this review, we focus on vascularized tumor models. First, we detail their fabrication, and especially the materials, cell types, and coculture used. Then, the different strategies of vascularization are described along with their classical applications in intra/extravasation or free drug assessment. Finally, current trends in DDS for cancer are discussed with an overview of the current efforts in the domain.

pH-Responsive Hyaluronic Acid Nanomicelles for Photodynamic /Chemodynamic Synergistic Therapy Trigger Immunogenicity and Oxygenation

Cancer metastasis and invasion are closely related to tumor cell immunosuppression and intracellular hypoxia. Activation of immunogenicity and intracellular oxygenation are effective strategies for cancer treatment. In this study, multifunctional nanomicelle hyaluronic acid and cinnamaldehyde is self-assembled into nanomicelles (HPCNPs) were constructed for immunotherapy and tumor cell oxygenation. The Schiff base was constructed of HPCNPs with pyropheophorbide a-Cu (PPa-Cu). HPCNPs are concentrated in tumor sites under the guidance of CD44 proteins, and under the stimulation of tumor environment (weakly acidic), the Schiff base is destroyed to release free PPa. HPCNPs with photodynamic therapeutic functions and chemokinetic therapeutic functions produce a large number of reactive oxygen species (1O2 and •OH) under exogenous (laser) and endogenous (H2O2) stimulations, causing cell damage, and then inducing immunogenic cell death (ICD). ICD markers (CRT and ATP) and immunoactivity markers (IL-2 and CD8) were characterized by immunofluorescence. Downregulation of Arg1 protein proved that the tumor microenvironment changed from immunosuppressive type (M2) to antitumor type (M1). The oxidation of glutathione by HPCNP cascades to amplify the concentration of reactive oxygen species. In situ oxygenation by HPCNPs based on a Fenton-like reaction improves the intracellular oxygen level. In vitro and in vivo experiments demonstrated that HPCNPs combined with an immune checkpoint blocker (α-PD-L1) effectively ablated primary tumors, effectively inhibited the growth of distal tumors, and increased the oxygen level in tumor cells.

Engineering Heterogeneous Tumor Models for Biomedical Applications

Tumor tissue engineering holds great promise for replicating the physiological and behavioral characteristics of tumors in vitro. Advances in this field have led to new opportunities for studying the tumor microenvironment and exploring potential anti-cancer therapeutics. However, the main obstacle to the widespread adoption of tumor models is the poor understanding and insufficient reconstruction of tumor heterogeneity. In this review, the current progress of engineering heterogeneous tumor models is discussed. First, the major components of tumor heterogeneity are summarized, which encompasses various signaling pathways, cell proliferations, and spatial configurations. Then, contemporary approaches are elucidated in tumor engineering that are guided by fundamental principles of tumor biology, and the potential of a bottom-up approach in tumor engineering is highlighted. Additionally, the characterization approaches and biomedical applications of tumor models are discussed, emphasizing the significant role of engineered tumor models in scientific research and clinical trials. Lastly, the challenges of heterogeneous tumor models in promoting oncology research and tumor therapy are described and key directions for future research are provided.

Biomimetic on-chip assay reveals the anti-metastatic potential of a novel thienopyrimidine compound in triple-negative breast cancer cell lines

Introduction: This study presents a microfluidic tumor microenvironment (TME) model for evaluating the anti-metastatic efficacy of a novel thienopyrimidines analog with anti-cancer properties utilizing an existing commercial platform. The microfluidic device consists of a tissue compartment flanked by vascular channels, allowing for the co-culture of multiple cell types and providing a wide range of culturing conditions in one device. Methods: Human metastatic, drug-resistant triple-negative breast cancer (TNBC) cells (SUM159PTX) and primary human umbilical vein endothelial cells (HUVEC) were used to model the TME. A dynamic perfusion scheme was employed to facilitate EC physiological function and lumen formation. Results: The measured permeability of the EC barrier was comparable to observed microvessels permeability in vivo. The TNBC cells formed a 3D tumor, and co-culture with HUVEC negatively impacted EC barrier integrity. The microfluidic TME was then used to model the intravenous route of drug delivery. Paclitaxel (PTX) and a novel non-apoptotic agent TPH104c were introduced via the vascular channels and successfully reached the TNBC tumor, resulting in both time and concentration-dependent tumor growth inhibition. PTX treatment significantly reduced EC barrier integrity, highlighting the adverse effects of PTX on vascular ECs. TPH104c preserved EC barrier integrity and prevented TNBC intravasation. Discussion: In conclusion, this study demonstrates the potential of microfluidics for studying complex biological processes in a controlled environment and evaluating the efficacy and toxicity of chemotherapeutic agents in more physiologically relevant conditions. This model can be a valuable tool for screening potential anticancer drugs and developing personalized cancer treatment strategies.

Bridging the gap between tumor-on-chip and clinics: a systematic review of 15 years of studies

Over the past 15 years, the field of oncology research has witnessed significant progress in the development of new cell culture models, such as tumor-on-chip (ToC) systems. In this comprehensive overview, we present a multidisciplinary perspective by bringing together physicists, biologists, clinicians, and experts from pharmaceutical companies to highlight the current state of ToC research, its unique features, and the challenges it faces. To offer readers a clear and quantitative understanding of the ToC field, we conducted an extensive systematic analysis of more than 300 publications related to ToC from 2005 to 2022. ToC offer key advantages over other in vitro models by enabling precise control over various parameters. These parameters include the properties of the extracellular matrix, mechanical forces exerted on cells, the physico-chemical environment, cell composition, and the architecture of the tumor microenvironment. Such fine control allows ToC to closely replicate the complex microenvironment and interactions within tumors, facilitating the study of cancer progression and therapeutic responses in a highly representative manner. Importantly, by incorporating patient-derived cells or tumor xenografts, ToC models have demonstrated promising results in terms of clinical validation. We also examined the potential of ToC for pharmaceutical industries in which ToC adoption is expected to occur gradually. Looking ahead, given the high failure rate of clinical trials and the increasing emphasis on the 3Rs principles (replacement, reduction, refinement of animal experimentation), ToC models hold immense potential for cancer research. In the next decade, data generated from ToC models could potentially be employed for discovering new therapeutic targets, contributing to regulatory purposes, refining preclinical drug testing and reducing reliance on animal models.

In Vitro Models of Blood and Lymphatic Vessels-Connecting Tissues and Immunity

Blood and lymphatic vessels are regulators of physiological processes, including oxygenation and fluid transport. Both vessels are ubiquitous throughout the body and are critical for sustaining tissue homeostasis. The complexity of each vessel's processes has limited the understanding of exactly how the vessels maintain their functions. Both vessels have been shown to be involved in the pathogenesis of many diseases, including cancer metastasis, and it is crucial to probe further specific mechanisms involved. In vitro models are developed to better understand blood and lymphatic physiological functions and their mechanisms. In this review, blood and lymphatic in vitro model systems, including 2D and 3D designs made using Transwells, microfluidic devices, organoid cultures, and various other methods, are described. Models studying endothelial cell-extracellular matrix interactions, endothelial barrier properties, transendothelial transport and cell migration, lymph/angiogenesis, vascular inflammation, and endothelial-cancer cell interactions are particularly focused. While the field has made significant progress in modeling and understanding lymphatic and blood vasculature, more models that include coculture of multiple cell types, complex extracellular matrix, and 3D morphologies, particularly for models mimicking disease states, will help further the understanding of the role of blood and lymphatic vasculature in health and disease.

The Applications and Challenges of the Development of In Vitro Tumor Microenvironment Chips

The tumor microenvironment (TME) plays a critical, yet mechanistically elusive role in tumor development and progression, as well as drug resistance. To better understand the pathophysiology of the complex TME, a reductionist approach has been employed to create in vitro microfluidic models called "tumor chips". Herein, we review the fabrication processes, applications, and limitations of the tumor chips currently under development for use in cancer research. Tumor chips afford capabilities for real-time observation, precise control of microenvironment factors (e.g. stromal and cellular components), and application of physiologically relevant fluid shear stresses and perturbations. Applications for tumor chips include drug screening and toxicity testing, assessment of drug delivery modalities, and studies of transport and interactions of immune cells and circulating tumor cells with primary tumor sites. The utility of tumor chips is currently limited by the ability to recapitulate the nuances of tumor physiology, including extracellular matrix composition and stiffness, heterogeneity of cellular components, hypoxic gradients, and inclusion of blood cells and the coagulome in the blood microenvironment. Overcoming these challenges and improving the physiological relevance of in vitro tumor models could provide powerful testing platforms in cancer research and decrease the need for animal and clinical studies.

3D bioprinted cancer models: from basic biology to drug development

Effort invested in the development of new drugs often fails to be translated into meaningful clinical benefits for patients with cancer. The development of more effective anticancer therapeutics and accurate prediction of their clinical merit remain urgent unmet medical needs. As solid cancers have complex and heterogeneous structures composed of different cell types and extracellular matrices, three-dimensional (3D) cancer models hold great potential for advancing our understanding of cancer biology, which has been historically investigated in tumour cell cultures on rigid plastic plates. Advanced 3D bioprinted cancer models have the potential to revolutionize the way we discover therapeutic targets, develop new drugs and personalize anticancer therapies in an accurate, reproducible, clinically translatable and robust manner. These ex vivo cancer models are already replacing existing in vitro systems and could, in the future, diminish or even replace the use of animal models. Therefore, profound understanding of the differences in tumorigenesis between 2D, 3D and animal models of cancer is essential. This Review presents the state of the art of 3D bioprinted cancer modelling, focusing on the biological processes that underlie the molecular mechanisms involved in cancer progression and treatment response as well as on proteomic and genomic signatures.

Tumor-on-a-chip: Perfusable vascular incorporation brings new approach to tumor metastasis research and drug development

The extracellular matrix interacts with cancer cells and is a key factor in the development of cancer. Traditional two-dimensional models cannot mimic the natural in situ environment of cancer tissues, whereas three-dimensional (3D) models such as spherical culture, bioprinting, and microfluidic approaches can achieve in vitro reproduction of certain structures and components of the tumor microenvironment, including simulation of the hypoxic environment of tumor tissue. However, the lack of a perfusable vascular network is a limitation of most 3D models. Solid tumor growth and metastasis require angiogenesis, and tumor models with microvascular networks have been developed to better understand underlying mechanisms. Tumor-on-a-chip technology combines the advantages of microfluidics and 3D cell culture technology for the simulation of tumor tissue complexity and characteristics. In this review, we summarize progress in constructing tumor-on-a-chip models with efficiently perfused vascular networks. We also discuss the applications of tumor-on-a-chip technology to studying the tumor microenvironment and drug development. Finally, we describe the creation of several common tumor models based on this technology to provide a deeper understanding and new insights into the design of vascularized cancer models. We believe that the tumor-on-a-chip approach is an important development that will provide further contributions to the field.

Biomedical Applications of Microfluidic Devices: A Review

Both passive and active microfluidic chips are used in many biomedical and chemical applications to support fluid mixing, particle manipulations, and signal detection. Passive microfluidic devices are geometry-dependent, and their uses are rather limited. Active microfluidic devices include sensors or detectors that transduce chemical, biological, and physical changes into electrical or optical signals. Also, they are transduction devices that detect biological and chemical changes in biomedical applications, and they are highly versatile microfluidic tools for disease diagnosis and organ modeling. This review provides a comprehensive overview of the significant advances that have been made in the development of microfluidics devices. We will discuss the function of microfluidic devices as micromixers or as sorters of cells and substances (e.g., microfiltration, flow or displacement, and trapping). Microfluidic devices are fabricated using a range of techniques, including molding, etching, three-dimensional printing, and nanofabrication. Their broad utility lies in the detection of diagnostic biomarkers and organ-on-chip approaches that permit disease modeling in cancer, as well as uses in neurological, cardiovascular, hepatic, and pulmonary diseases. Biosensor applications allow for point-of-care testing, using assays based on enzymes, nanozymes, antibodies, or nucleic acids (DNA or RNA). An anticipated development in the field includes the optimization of techniques for the fabrication of microfluidic devices using biocompatible materials. These developments will increase biomedical versatility, reduce diagnostic costs, and accelerate diagnosis time of microfluidics technology.

Application of Microfluidics in Drug Development from Traditional Medicine

While there are many clinical drugs for prophylaxis and treatment, the search for those with low or no risk of side effects for the control of infectious and non-infectious diseases is a dilemma that cannot be solved by today's traditional drug development strategies. The need for new drug development strategies is becoming increasingly important, and the development of new drugs from traditional medicines is the most promising strategy. Many valuable clinical drugs have been developed based on traditional medicine, including drugs with single active ingredients similar to modern drugs and those developed from improved formulations of traditional drugs. However, the problems of traditional isolation and purification and drug screening methods should be addressed for successful drug development from traditional medicine. Advances in microfluidics have not only contributed significantly to classical drug development but have also solved many of the thorny problems of new strategies for developing new drugs from traditional drugs. In this review, we provide an overview of advanced microfluidics and its applications in drug development (drug compound synthesis, drug screening, drug delivery, and drug carrier fabrication) with a focus on its applications in conventional medicine, including the separation and purification of target components in complex samples and screening of active ingredients of conventional drugs. We hope that our review gives better insight into the potential of traditional medicine and the critical role of microfluidics in the drug development process. In addition, the emergence of new ideas and applications will bring about further advances in the field of drug development.

Clinical application of advanced multi-omics tumor profiling: Shaping precision oncology of the future

Next-generation DNA sequencing technology has dramatically advanced clinical oncology through the identification of therapeutic targets and molecular biomarkers, leading to the personalization of cancer treatment with significantly improved outcomes for many common and rare tumor entities. More recent developments in advanced tumor profiling now enable dissection of tumor molecular architecture and the functional phenotype at cellular and subcellular resolution. Clinical translation of high-resolution tumor profiling and integration of multi-omics data into precision treatment, however, pose significant challenges at the level of prospective validation and clinical implementation. In this review, we summarize the latest advances in multi-omics tumor profiling, focusing on spatial genomics and chromatin organization, spatial transcriptomics and proteomics, liquid biopsy, and ex vivo modeling of drug response. We analyze the current stages of translational validation of these technologies and discuss future perspectives for their integration into precision treatment.

In Vitro Models of Biological Barriers for Nanomedical Research

Nanoconstructs developed for biomedical purposes must overcome diverse biological barriers before reaching the target where playing their therapeutic or diagnostic function. In vivo models are very complex and unsuitable to distinguish the roles plaid by the multiple biological barriers on nanoparticle biodistribution and effect; in addition, they are costly, time-consuming and subject to strict ethical regulation. For these reasons, simplified in vitro models are preferred, at least for the earlier phases of the nanoconstruct development. Many in vitro models have therefore been set up. Each model has its own pros and cons: conventional 2D cell cultures are simple and cost-effective, but the information remains limited to single cells; cell monolayers allow the formation of cell–cell junctions and the assessment of nanoparticle translocation across structured barriers but they lack three-dimensionality; 3D cell culture systems are more appropriate to test in vitro nanoparticle biodistribution but they are static; finally, bioreactors and microfluidic devices can mimicking the physiological flow occurring in vivo thus providing in vitro biological barrier models suitable to reliably assess nanoparticles relocation. In this evolving context, the present review provides an overview of the most representative and performing in vitro models of biological barriers set up for nanomedical research.

Omics of endothelial cell dysfunction in sepsis

During sepsis, defined as life-threatening organ dysfunction due to dysregulated host response to infection, systemic inflammation activates endothelial cells and initiates a multifaceted cascade of pro-inflammatory signaling events, resulting in increased permeability and excessive recruitment of leukocytes. Vascular endothelial cells share many common properties but have organ-specific phenotypes with unique structure and function. Thus, therapies directed against endothelial cell phenotypes are needed to address organ-specific endothelial cell dysfunction. Omics allow for the study of expressed genes, proteins and/or metabolites in biological systems and provide insight on temporal and spatial evolution of signals during normal and diseased conditions. Proteomics quantifies protein expression, identifies protein-protein interactions and can reveal mechanistic changes in endothelial cells that would not be possible to study via reductionist methods alone. In this review, we provide an overview of how sepsis pathophysiology impacts omics with a focus on proteomic analysis of mouse endothelial cells during sepsis/inflammation and its relationship with the more clinically relevant omics of human endothelial cells. We discuss how omics has been used to define septic endotype signatures in different populations with a focus on proteomic analysis in organ-specific microvascular endothelial cells during sepsis or septic-like inflammation. We believe that studies defining septic endotypes based on proteomic expression in endothelial cell phenotypes are urgently needed to complement omic profiling of whole blood and better define sepsis subphenotypes. Lastly, we provide a discussion of how in silico modeling can be used to leverage the large volume of omics data to map response pathways in sepsis.

Progress in cancer drug delivery based on AS1411 oriented nanomaterials

Targeted cancer therapy has become one of the most important medical methods because of the spreading and metastatic nature of cancer. Based on the introduction of AS1411 and its four-chain structure, this paper reviews the research progress in cancer detection and drug delivery systems by modifying AS1411 aptamers based on graphene, mesoporous silica, silver and gold. The application of AS1411 in cancer treatment and drug delivery and the use of AS1411 as a targeting agent for the detection of cancer markers such as nucleoli were summarized from three aspects of active targeting, passive targeting and targeted nucleic acid apharmers. Although AS1411 has been withdrawn from clinical trials, the research surrounding its structural optimization is still very popular. Further progress has been made in the modification of nanoparticles loaded with TCM extracts by AS1411.

Application of Microfluidic Systems for Breast Cancer Research

Cancer is a disease in which cells in the body grow out of control; breast cancer is the most common cancer in women in the United States. Due to early screening and advancements in therapeutic interventions, deaths from breast cancer have declined over time, although breast cancer remains the second leading cause of cancer death among women. Most deaths are due to metastasis, as cancer cells from the primary tumor in the breast form secondary tumors in remote sites in distant organs. Over many years, the basic biological mechanisms of breast cancer initiation and progression, as well as the subsequent metastatic cascade, have been studied using cell cultures and animal models. These models, although extremely useful for delineating cellular mechanisms, are poor predictors of physiological responses, primarily due to lack of proper microenvironments. In the last decade, microfluidics has emerged as a technology that could lead to a paradigm shift in breast cancer research. With the introduction of the organ-on-a-chip concept, microfluidic-based systems have been developed to reconstitute the dominant functions of several organs. These systems enable the construction of 3D cellular co-cultures mimicking in vivo tissue-level microenvironments, including that of breast cancer. Several reviews have been presented focusing on breast cancer formation, growth and metastasis, including invasion, intravasation, and extravasation. In this review, realizing that breast cancer can recur decades following post-treatment disease-free survival, we expand the discussion to account for microfluidic applications in the important areas of breast cancer detection, dormancy, and therapeutic development. It appears that, in the future, the role of microfluidics will only increase in the effort to eradicate breast cancer.

Advanced Microfluidic Technologies for Lipid Nano-Microsystems from Synthesis to Biological Application

Microfluidics is an emerging technology that can be employed as a powerful tool for designing lipid nano-microsized structures for biological applications. Those lipid structures can be used as carrying vehicles for a wide range of drugs and genetic materials. Microfluidic technology also allows the design of sustainable processes with less financial demand, while it can be scaled up using parallelization to increase production. From this perspective, this article reviews the recent advances in the synthesis of lipid-based nanostructures through microfluidics (liposomes, lipoplexes, lipid nanoparticles, core-shell nanoparticles, and biomimetic nanovesicles). Besides that, this review describes the recent microfluidic approaches to produce lipid micro-sized structures as giant unilamellar vesicles. New strategies are also described for the controlled release of the lipid payloads using microgels and droplet-based microfluidics. To address the importance of microfluidics for lipid-nanoparticle screening, an overview of how microfluidic systems can be used to mimic the cellular environment is also presented. Future trends and perspectives in designing novel nano and micro scales are also discussed herein.

From cell spheroids to vascularized cancer organoids: Microfluidic tumor-on-a-chip models for preclinical drug evaluations

Chemotherapy is one of the most effective cancer treatments. Starting from the discovery of new molecular entities, it usually takes about 10 years and 2 billion U.S. dollars to bring an effective anti-cancer drug from the benchtop to patients. Due to the physiological differences between animal models and humans, more than 90% of drug candidates failed in phase I clinical trials. Thus, a more efficient drug screening system to identify feasible compounds and pre-exclude less promising drug candidates is strongly desired. For their capability to accurately construct in vitro tumor models derived from human cells to reproduce pathological and physiological processes, microfluidic tumor chips are reliable platforms for preclinical drug screening, personalized medicine, and fundamental oncology research. This review summarizes the recent progress of the microfluidic tumor chip and highlights tumor vascularization strategies. In addition, promising imaging modalities for enhancing data acquisition and machine learning-based image analysis methods to accurately quantify the dynamics of tumor spheroids are introduced. It is believed that the microfluidic tumor chip will serve as a high-throughput, biomimetic, and multi-sensor integrated system for efficient preclinical drug evaluation in the future.

Recent Advances in Microfluidic Platforms for Programming Cell-Based Living Materials

Cell-based living materials, including single cells, cell-laden fibers, cell sheets, organoids, and organs, have attracted intensive interests owing to their widespread applications in cancer therapy, regenerative medicine, drug development, and so on. Significant progress in materials, microfabrication, and cell biology have promoted the development of numerous promising microfluidic platforms for programming these cell-based living materials with a high-throughput, scalable, and efficient manner. In this review, the recent progress of novel microfluidic platforms for programming cell-based living materials is presented. First, the unique features, categories, and materials and related fabrication methods of microfluidic platforms are briefly introduced. From the viewpoint of the design principles of the microfluidic platforms, the recent significant advances of programming single cells, cell-laden fibers, cell sheets, organoids, and organs in turns are then highlighted. Last, by providing personal perspectives on challenges and future trends, this review aims to motivate researchers from the fields of materials and engineering to work together with biologists and physicians to promote the development of cell-based living materials for human healthcare-related applications.

Multi-Organs-on-Chips for Testing Small-Molecule Drugs: Challenges and Perspectives

Organ-on-a-chip technology has been used in testing small-molecule drugs for screening potential therapeutics and regulatory protocols. The technology is expected to boost the development of novel therapies and accelerate the discovery of drug combinations in the coming years. This has led to the development of multi-organ-on-a-chip (MOC) for recapitulating various organs involved in the drug-body interactions. In this review, we discuss the current MOCs used in screening small-molecule drugs and then focus on the dynamic process of drug absorption, distribution, metabolism, and excretion. We also address appropriate materials used for MOCs at low cost and scale-up capacity suitable for high-performance analysis of drugs and commercial high-throughput screening platforms.

Embracing Mechanobiology in Next Generation Organ-On-A-Chip Models of Bone Metastasis

Bone metastasis in breast cancer is associated with high mortality. Biomechanical cues presented by the extracellular matrix play a vital role in driving cancer metastasis. The lack of in vitro models that recapitulate the mechanical aspects of the in vivo microenvironment hinders the development of novel targeted therapies. Organ-on-a-chip (OOAC) platforms have recently emerged as a new generation of in vitro models that can mimic cell-cell interactions, enable control over fluid flow and allow the introduction of mechanical cues. Biomaterials used within OOAC platforms can determine the physical microenvironment that cells reside in and affect their behavior, adhesion, and localization. Refining the design of OOAC platforms to recreate microenvironmental regulation of metastasis and probe cell-matrix interactions will advance our understanding of breast cancer metastasis and support the development of next-generation metastasis-on-a-chip platforms. In this mini-review, we discuss the role of mechanobiology on the behavior of breast cancer and bone-residing cells, summarize the current capabilities of OOAC platforms for modeling breast cancer metastasis to bone, and highlight design opportunities offered by the incorporation of mechanobiological cues in these platforms.

Meet me halfway: Are in vitro 3D cancer models on the way to replace in vivo models for nanomedicine development?

The complexity and diversity of the biochemical processes that occur during tumorigenesis and metastasis are frequently over-simplified in the traditional in vitro cell cultures. Two-dimensional cultures limit researchers' experimental observations and frequently give rise to misleading and contradictory results. Therefore, in order to overcome the limitations of in vitro studies and bridge the translational gap to in vivo applications, 3D models of cancer were developed in the last decades. The three dimensions of the tumor, including its cellular and extracellular microenvironment, are recreated by combining co-cultures of cancer and stromal cells in 3D hydrogel-based growth factors-inclusive scaffolds. More complex 3D cultures, containing functional blood vasculature, can integrate in the system external stimuli (e.g. oxygen and nutrient deprivation, cytokines, growth factors) along with drugs, or other therapeutic compounds. In this scenario, cell signaling pathways, metastatic cascade steps, cell differentiation and self-renewal, tumor-microenvironment interactions, and precision and personalized medicine, are among the wide range of biological applications that can be studied. Here, we discuss a broad variety of strategies exploited by scientists to create in vitro 3D cancer models that resemble as much as possible the biology and patho-physiology of in vivo tumors and predict faithfully the treatment outcome.

Identifying Candidate Biomarkers of Ionizing Radiation in Human Pulmonary Microvascular Lumens Using Microfluidics-A Pilot Study

The microvasculature system is critical for the delivery and removal of key nutrients and waste products and is significantly damaged by ionizing radiation. Single-cell capillaries and microvasculature structures are the primary cause of circulatory dysfunction, one that results in morbidities leading to progressive tissue and organ failure and premature death. Identifying tissue-specific biomarkers that are predictive of the extent of tissue and organ damage will aid in developing medical countermeasures for treating individuals exposed to ionizing radiation. In this pilot study, we developed and tested a 17 µL human-derived microvascular microfluidic lumen for identifying candidate biomarkers of ionizing radiation exposure. Through mass-spectrometry-based proteomics, we detected 35 proteins that may be candidate early biomarkers of ionizing radiation exposure. This pilot study demonstrates the feasibility of using humanized microfluidic and organ-on-a-chip systems for biomarker discovery studies. A more elaborate study of sufficient statistical power is needed to identify candidate biomarkers and test medical countermeasures of ionizing radiation.

Emerging Approaches to Understanding Microvascular Endothelial Heterogeneity: A Roadmap for Developing Anti-Inflammatory Therapeutics

The endothelium is the inner layer of all blood vessels and it regulates hemostasis. It also plays an active role in the regulation of the systemic inflammatory response. Systemic inflammatory disease often results in alterations in vascular endothelium barrier function, increased permeability, excessive leukocyte trafficking, and reactive oxygen species production, leading to organ damage. Therapeutics targeting endothelium inflammation are urgently needed, but strong concerns regarding the level of phenotypic heterogeneity of microvascular endothelial cells between different organs and species have been expressed. Microvascular endothelial cell heterogeneity in different organs and organ-specific variations in endothelial cell structure and function are regulated by intrinsic signals that are differentially expressed across organs and species; a result of this is that neutrophil recruitment to discrete organs may be regulated differently. In this review, we will discuss the morphological and functional variations in differently originated microvascular endothelia and discuss how these variances affect systemic function in response to inflammation. We will review emerging in vivo and in vitro models and techniques, including microphysiological devices, proteomics, and RNA sequencing used to study the cellular and molecular heterogeneity of endothelia from different organs. A better understanding of microvascular endothelial cell heterogeneity will provide a roadmap for developing novel therapeutics to target the endothelium.

Engineering Breast Cancer On-chip-Moving Toward Subtype Specific Models

Breast cancer is the second leading cause of death among women worldwide, and while hormone receptor positive subtypes have a clear and effective treatment strategy, other subtypes, such as triple negative breast cancers, do not. Development of new drugs, antibodies, or immune targets requires significant re-consideration of current preclinical models, which frequently fail to mimic the nuances of patient-specific breast cancer subtypes. Each subtype, together with the expression of different markers, genetic and epigenetic profiles, presents a unique tumor microenvironment, which promotes tumor development and progression. For this reason, personalized treatments targeting components of the tumor microenvironment have been proposed to mitigate breast cancer progression, particularly for aggressive triple negative subtypes. To-date, animal models remain the gold standard for examining new therapeutic targets; however, there is room for in vitro tools to bridge the biological gap with humans. Tumor-on-chip technologies allow for precise control and examination of the tumor microenvironment and may add to the toolbox of current preclinical models. These new models include key aspects of the tumor microenvironment (stroma, vasculature and immune cells) which have been employed to understand metastases, multi-organ interactions, and, importantly, to evaluate drug efficacy and toxicity in humanized physiologic systems. This review provides insight into advanced in vitro tumor models specific to breast cancer, and discusses their potential and limitations for use as future preclinical patient-specific tools.

Microfluidic Reconstitution of Tumor Microenvironment for Nanomedical Applications

Nanoparticles have an extensive range of diagnostic and therapeutic applications in cancer treatment. However, their current clinical translation is slow, mainly due to the failure to develop preclinical evaluation techniques that can draw similar conclusions to clinical outcomes by adequately mimicking nanoparticle behavior in complicated tumor microenvironments (TMEs). Microfluidic methods offer significant advantages over conventional in vitro methods to resolve these challenges by recapitulating physiological cues of the TME such as the extracellular matrix, shear stress, interstitial flow, soluble factors, oxygen, and nutrient gradients. The methods are capable of de-coupling microenvironmental features, spatiotemporal controlling of experimental sequences, and high throughput readouts in situ. This progress report highlights the recent achievements of microfluidic models to reconstitute the physiological microenvironment, especially for nanomedical tools for cancer treatment.

Biomimetic Microfluidic Platforms for the Assessment of Breast Cancer Metastasis

Of around half a million women dying of breast cancer each year, more than 90% die due to metastasis. Models necessary to understand the metastatic process, particularly breast cancer cell extravasation and colonization, are currently limited and urgently needed to develop therapeutic interventions necessary to prevent breast cancer metastasis. Microfluidic approaches aim to reconstitute functional units of organs that cannot be modeled easily in traditional cell culture or animal studies by reproducing vascular networks and parenchyma on a chip in a three-dimensional, physiologically relevant in vitro system. In recent years, microfluidics models utilizing innovative biomaterials and micro-engineering technologies have shown great potential in our effort of mechanistic understanding of the breast cancer metastasis cascade by providing 3D constructs that can mimic in vivo cellular microenvironment and the ability to visualize and monitor cellular interactions in real-time. In this review, we will provide readers with a detailed discussion on the application of the most up-to-date, state-of-the-art microfluidics-based breast cancer models, with a special focus on their application in the engineering approaches to recapitulate the metastasis process, including invasion, intravasation, extravasation, breast cancer metastasis organotropism, and metastasis niche formation.

Breast tumor-on-chip models: From disease modeling to personalized drug screening

Breast cancer is one of the leading causes of mortality worldwide being the most common cancer among women. Despite the significant progress obtained during the past years in the understanding of breast cancer pathophysiology, women continue to die from it. Novel tools and technologies are needed to develop better diagnostic and therapeutic approaches, and to better understand the molecular and cellular players involved in the progression of this disease. Typical methods employed by the pharmaceutical industry and laboratories to investigate breast cancer etiology and evaluate the efficiency of new therapeutic compounds are still based on traditional tissue culture flasks and animal models, which have certain limitations. Recently, tumor-on-chip technology emerged as a new generation of in vitro disease model to investigate the physiopathology of tumors and predict the efficiency of drugs in a native-like microenvironment. These microfluidic systems reproduce the functional units and composition of human organs and tissues, and importantly, the rheological properties of the native scenario, enabling precise control over fluid flow or local gradients. Herein, we review the most recent works related to breast tumor-on-chip for disease modeling and drug screening applications. Finally, we critically discuss the future applications of this emerging technology in breast cancer therapeutics and drug development.

In Vitro and In Vivo Tumor Models for the Evaluation of Anticancer Nanoparticles

Multiple studies about tumor biology have revealed the determinant role of the tumor microenvironment in cancer progression, resulting from the dynamic interactions between tumor cells and surrounding stromal cells within the extracellular matrix. This malignant microenvironment highly impacts the efficacy of anticancer nanoparticles by displaying drug resistance mechanisms, as well as intrinsic physical and biochemical barriers, which hamper their intratumoral accumulation and biological activity.Currently, two-dimensional cell cultures are used as the initial screening method in vitro for testing cytotoxic nanocarriers. However, this fails to mimic the tumor heterogeneity, as well as the three-dimensional tumor architecture and pathophysiological barriers, leading to an inaccurate pharmacological evaluation.Biomimetic 3D in vitro tumor models, on the other hand, are emerging as promising tools for more accurately assessing nanoparticle activity, owing to their ability to recapitulate certain features of the tumor microenvironment and thus provide mechanistic insights into nanocarrier intratumoral penetration and diffusion rates.Notwithstanding, in vivo validation of nanomedicines remains irreplaceable at the preclinical stage, and a vast variety of more advanced in vivo tumor models is currently available. Such complex animal models (e.g., genetically engineered mice and patient-derived xenografts) are capable of better predicting nanocarrier clinical efficiency, as they closely resemble the heterogeneity of the human tumor microenvironment.Herein, the development of physiologically more relevant in vitro and in vivo tumor models for the preclinical evaluation of anticancer nanoparticles will be discussed, as well as the current limitations and future challenges in clinical translation.

Emodin-Conjugated PEGylation of Fe3O4 Nanoparticles for FI/MRI Dual-Modal Imaging and Therapy in Pancreatic Cancer

BACKGROUND

Pancreatic cancer (PC) remains a difficult tumor to diagnose and treat. It is often diagnosed as advanced by reason of the anatomical structure of the deep retroperitoneal layer of the pancreas, lack of typical symptoms and effective screening methods to detect this malignancy, resulting in a low survival rate. Emodin (EMO) is an economical natural product with effective treatment and few side effects of cancer treatment. Magnetic nanoparticles (MNPs) can achieve multiplexed imaging and targeted therapy by loading a wide range of functional materials such as fluorescent dyes and therapeutic agents.

PURPOSE

The purpose of this study was to design and evaluate a multifunctional theranostic nanoplatform for PC diagnosis and treatment.

METHODS

In this study, we successfully developed EMO-loaded, Cy7-functionalized, PEG-coated Fe₃O₄ (Fe₃O₄-PEG-Cy7-EMO). Characteristics including morphology, hydrodynamic size, zeta potentials, stability, and magnetic properties of Fe₃O₄-PEG-Cy7-EMO were evaluated. Fluorescence imaging (FI)/magnetic resonance imaging (MRI) and therapeutic treatment were examined in vitro and in vivo.

RESULTS

Fe₃O₄-PEG-Cy7-EMO nanoparticles had a core size of 9.9 ± 1.2 nm, which showed long-time stability and FI/MRI properties. Bio-transmission electron microscopy (bio-TEM) results showed that Fe₃O₄-PEG-Cy7-EMO nanoparticles were endocytosed into BxPC-3 cells, while few were observed in hTERT-HPNE cells. Prussian blue staining also confirmed that BxPC-3 cells have a stronger phagocytic ability as compared to hTERT-HPNE cells. Additionally, Fe₃O₄-PEG-Cy7-EMO had a stronger inhibition effect on BxPC-3 cells than Fe₃O₄-PEG and EMO. The hemolysis experiment proved that Fe₃O₄-PEG-Cy7-EMO can be used in vivo experiments. In vivo analysis demonstrated that Fe₃O₄-PEG-Cy7-EMO enabled FI/MRI dual-modal imaging and targeted therapy in pancreatic tumor xenografted mice.

CONCLUSION

Fe₃O₄-PEG-Cy7-EMO may serve as a potential theranostic nanoplatform for PC.

Real-Time Ratiometric Imaging of Micelles Assembly State in a Microfluidic Cancer-on-a-Chip

The performance of supramolecular nanocarriers as drug delivery systems depends on their stability in the complex and dynamic biological media. After administration, nanocarriers are challenged by physiological barriers such as shear stress and proteins present in blood, endothelial wall, extracellular matrix, and eventually cancer cell membrane. While early disassembly will result in a premature drug release, extreme stability of the nanocarriers can lead to poor drug release and low efficiency. Therefore, comprehensive understanding of the stability and assembly state of supramolecular carriers in each stage of delivery is the key factor for the rational design of these systems. One of the main challenges is that current 2D in vitro models do not provide exhaustive information, as they fail to recapitulate the 3D tumor microenvironment. This deficiency in the 2D model complexity is the main reason for the differences observed in vivo when testing the performance of supramolecular nanocarriers. Herein, we present a real-time monitoring study of self-assembled micelles stability and extravasation, combining spectral confocal microscopy and a microfluidic cancer-on-a-chip. The combination of advanced imaging and a reliable 3D model allows tracking of micelle disassembly by following the spectral properties of the amphiphiles in space and time during the crucial steps of drug delivery. The spectrally active micelles were introduced under flow and their position and conformation continuously followed by spectral imaging during the crossing of barriers, revealing the interplay between carrier structure, micellar stability, and extravasation. Integrating the ability of the micelles to change their fluorescent properties when disassembled, spectral confocal imaging and 3D microfluidic tumor blood vessel-on-a-chip resulted in the establishment of a robust testing platform suitable for real-time imaging and evaluation of supramolecular drug delivery carrier's stability.

The evolution of polymer conjugation and drug targeting for the delivery of proteins and bioactive molecules

Polymer conjugation can be considered one of the leading approaches within the vast field of nanotechnology-based drug delivery systems. In fact, such technology can be exploited for delivering an active molecule, such as a small drug, a protein, or genetic material, or it can be applied to other drug delivery systems as a strategy to improve their in vivo behavior or pharmacokinetic activities such as prolonging the half-life of a drug, conferring stealth properties, providing external stimuli responsiveness, and so on. If on the one hand, polymer conjugation with biotech drug is considered the linchpin of the protein delivery field boasting several products in clinical use, on the other, despite dedicated research, conjugation with low molecular weight drugs has not yet achieved the milestone of the first clinical approval. Some of the primary reasons for this debacle are the difficulties connected to achieving selective targeting to diseased tissue, organs, or cells, which is the main goal not only of polymer conjugation but of all delivery systems of small drugs. In light of the need to achieve better drug targeting, researchers are striving to identify more sophisticated, biocompatible delivery approaches and to open new horizons for drug targeting methodologies leading to successful clinical applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Mechanical Stimulation: A Crucial Element of Organ-on-Chip Models

Organ-on-chip (OOC) systems recapitulate key biological processes and responses in vitro exhibited by cells, tissues, and organs in vivo. Accordingly, these models of both health and disease hold great promise for improving fundamental research, drug development, personalized medicine, and testing of pharmaceuticals, food substances, pollutants etc. Cells within the body are exposed to biomechanical stimuli, the nature of which is tissue specific and may change with disease or injury. These biomechanical stimuli regulate cell behavior and can amplify, annul, or even reverse the response to a given biochemical cue or drug candidate. As such, the application of an appropriate physiological or pathological biomechanical environment is essential for the successful recapitulation of in vivo behavior in OOC models. Here we review the current range of commercially available OOC platforms which incorporate active biomechanical stimulation. We highlight recent findings demonstrating the importance of including mechanical stimuli in models used for drug development and outline emerging factors which regulate the cellular response to the biomechanical environment. We explore the incorporation of mechanical stimuli in different organ models and identify areas where further research and development is required. Challenges associated with the integration of mechanics alongside other OOC requirements including scaling to increase throughput and diagnostic imaging are discussed. In summary, compelling evidence demonstrates that the incorporation of biomechanical stimuli in these OOC or microphysiological systems is key to fully replicating in vivo physiology in health and disease.

Endothelial Regulation of Drug Transport in a 3D Vascularized Tumor Model

Drug discovery and efficacy in cancer treatments are limited by the inability of pre-clinical models to predict successful outcomes in humans. Limitations remain partly due to their lack of a physiologic tumor microenvironment (TME), which plays a considerable role in drug delivery and tumor response to therapy. Chemotherapeutics and immunotherapies rely on transport through the vasculature, via the smallest capillaries and stroma to the tumor, where passive and active transport processes are at play. Here, a 3D vascularized tumor on-chip is used to examine drug delivery in a relevant TME within a large bed of perfusable vasculature. This system demonstrates highly localized pathophysiological effects of two tumor spheroids (Skov3 and A549) which cause significant changes in vessel density and barrier function. Paclitaxel (Taxol) uptake is examined through diffusivity measurements, functional efflux assays and accumulation of the fluorescent-conjugated drug within the TME. Due to vascular and stromal contributions, differences in the response of vascularized tumors to Taxol (shrinkage and CD44 expression) are apparent compared with simpler models. This model specifically allows for examination of spatially resolved tumor-associated endothelial dysfunction, likely improving the representation of in vivo drug distribution, and has potential for development into a more predictable model of drug delivery.

Organotypic Modeling of the Tumor Landscape

Cancer is a complex disease and it is now clear that not only epithelial tumor cells play a role in carcinogenesis. The tumor microenvironment is composed of non-stromal cells, including endothelial cells, adipocytes, immune and nerve cells, and a stromal compartment composed of extracellular matrix, cancer-associated fibroblasts and mesenchymal cells. Tumorigenesis is a dynamic process with constant interactions occurring between the tumor cells and their surroundings. Even though all connections have not yet been discovered, it is now known that crosstalk between actors of the microenvironment drives cancer progression. Taking into account this complexity, it is important to develop relevant models to study carcinogenesis. Conventional 2D culture models fail to represent the entire tumor microenvironment properly and the use of animal models should be decreased with respect to the 3Rs rule. To this aim, in vitro organotypic models have been significantly developed these past few years. These models have different levels of complexity and allow the study of tumor cells alone or in interaction with the microenvironment actors during the multiple stages of carcinogenesis. This review depicts recent insights into organotypic modeling of the tumor and its microenvironment all throughout cancer progression. It offers an overview of the crosstalk between epithelial cancer cells and their microenvironment during the different phases of carcinogenesis, from the early cell autonomous events to the late metastatic stages. The advantages of 3D over classical 2D or in vivo models are presented as well as the most promising organotypic models. A particular focus is made on organotypic models used for studying cancer progression, from the less complex spheroids to the more sophisticated body-on-a-chip. Last but not least, we address the potential benefits of these models in personalized medicine which is undoubtedly a domain paving the path to new hopes in terms of cancer care and cure.

Interweaving Tumor Heterogeneity into the Cancer Epigenetic/Metabolic Axis

Significance: The epigenomic/metabolic landscape in cancer has been studied extensively in the past decade and forms the basis of various drug targets. Yet, cancer treatment remains a challenge, with clinical trials exhibiting limited efficacy and high relapse rates. Patients respond differently to therapy, which is fundamentally attributed to tumor heterogeneity, both across and within tumors. This review focuses on the interactions between the heterogeneous tumor microenvironment (TME) and the epigenomic/metabolic axis in cancer, as well as the emerging technologies under development to aid heterogeneity studies. Recent Advances: Interlinks between epigenetics and metabolism in cancer have been reported. Emerging studies have unveiled interactions between the TME and cancer cells that play a critical role in regulating epigenetics and reprogramming cancer metabolism, suggesting a three-way cross talk. Critical Issues: This cross talk accentuates the multiplex nature of cancer, and the importance of considering tumor heterogeneity in various epigenomic/metabolic cancer studies. Future Directions: With the advancement in single-cell profiling, it may be possible to identify cancer subclones and their unique vulnerabilities to develop a multimodal therapy. Drugs targeting the TME are currently being studied, and a better understanding of the TME in regulating cancer epigenetics and metabolism may hold the key to identifying novel therapeutic targets.

Organ-on-a-chip platforms for accelerating the evaluation of nanomedicine

Nanomedicine involves the use of engineered nanoscale materials in an extensive range of diagnostic and therapeutic applications and can be applied to the treatment of many diseases. Despite the rapid progress and tremendous potential of nanomedicine in the past decades, the clinical translational process is still quite slow, owing to the difficulty in understanding, evaluating, and predicting nanomaterial behaviors within the complex environment of human beings. Microfluidics-based organ-on-a-chip (Organ Chip) techniques offer a promising way to resolve these challenges. Sophisticatedly designed Organ Chip enable in vitro simulation of the in vivo microenvironments, thus providing robust platforms for evaluating nanomedicine. Herein, we review recent developments and achievements in Organ Chip models for nanomedicine evaluations, categorized into seven broad sections based on the target organ systems: respiratory, digestive, lymphatic, excretory, nervous, and vascular, as well as coverage on applications relating to cancer. We conclude by providing our perspectives on the challenges and potential future directions for applications of Organ Chip in nanomedicine.

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Microfluidics-based organ-on-a-chip (Organ Chip) techniques offer a promising way to understand, evaluate, and predict nanomedicine behaviors within the complex environment.

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Organ Chip models for nanomedicine evaluations are categorized into seven broad sections based on the targeted body systems.

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Limitations, challenges, and perspectives of Organ Chip for accelerating the assessment of nanomedicine are discussed, respectively.

In vitro vascularized tumor platform for modeling tumor-vasculature interactions of inflammatory breast cancer

Inflammatory breast cancer (IBC), a rare form of breast cancer associated with increased angiogenesis and metastasis, is largely driven by tumor-stromal interactions with the vasculature and the extracellular matrix (ECM). However, there is currently a lack of understanding of the role these interactions play in initiation and progression of the disease. In this study, we developed the first three-dimensional, in vitro, vascularized, microfluidic IBC platform to quantify the spatial and temporal dynamics of tumor-vasculature and tumor-ECM interactions specific to IBC. Platforms consisting of collagen type 1 ECM with an endothelialized blood vessel were cultured with IBC cells, MDA-IBC3 (HER2+) or SUM149 (triple negative), and for comparison to non-IBC cells, MDA-MB-231 (triple negative). Acellular collagen platforms with endothelialized blood vessels served as controls. SUM149 and MDA-MB-231 platforms exhibited a significantly (p < .05) higher vessel permeability and decreased endothelial coverage of the vessel lumen compared to the control. Both IBC platforms, MDA-IBC3 and SUM149, expressed higher levels of vascular endothelial growth factor (p < .05) and increased collagen ECM porosity compared to non-IBCMDA-MB-231 (p < .05) and control (p < .01) platforms. Additionally, unique to the MDA-IBC3 platform, we observed progressive sprouting of the endothelium over time resulting in viable vessels with lumen. The newly sprouted vessels encircled clusters of MDA-IBC3 cells replicating a key feature of in vivo IBC. The IBC in vitro vascularized platforms introduced in this study model well-described in vivo and clinical IBC phenotypes and provide an adaptable, high throughput tool for systematically and quantitatively investigating tumor-stromal mechanisms and dynamics of tumor progression.

An Improved Vascularized, Dual-Channel Microphysiological System Facilitates Modeling of Proximal Tubular Solute Secretion

A vascularized human proximal tubule model in a dual-channel microphysiological system (VPT-MPS) was developed, representing an advance over previous, single-cell-type kidney microphysiological systems. Human proximal tubule epithelial cells (PTECs) and human umbilical vein endothelial cells (HUVECs) were cocultured in side-by-side channels. Over 24 h of coculturing, PTECs maintained polarized expression of Na+/K+ ATPase, tight junctions (ZO-1), and OAT1. HUVECs showed the absence of ZO-1 but expressed endothelial cell marker (CD-31). In time-lapse imaging studies, fluorescein isothiocyanate (FITC)-dextran passed freely from the HUVEC vessel into the supporting extracellular matrix, confirming the leakiness of the endothelium (at 80 min, matrix/intravessel fluorescence ratio = 0.2). Dextran-associated fluorescence accumulated in the matrix adjacent to the basolateral aspect of the PTEC tubule with minimal passage of the compound into the tubule lumen observed (at 80 min, tubule lumen/matrix fluorescence ratio = 0.01). This demonstrates that the proximal tubule compartment is the rate-limiting step in the secretion of compounds in VPT-MPS. In kinetic studies with radiolabeled markers, p-aminohippuric acid (PAH) exhibited greater output into the tubule lumen than did paracellular markers mannitol and FITC-dextran (tubule outflow/vessel outflow concentration ratio of 7.7% vs 0.5 and 0.4%, respectively). A trend toward reduced PAH secretion by 45% was observed upon coadministration of probenecid. This signifies functional expression of renal transporters in PTECs that normally mediate the renal secretion of PAH. The VPT-MPS holds the promise of providing an in vitro platform for evaluating the renal secretion of new drug candidates and investigating the dysregulation of tubular drug secretion in chronic kidney disease.

Protein Kinase C-Delta (PKCδ) Tyrosine Phosphorylation is a Critical Regulator of Neutrophil-Endothelial Cell Interaction in Inflammation

BACKGROUND

Neutrophil dysfunction plays an important role in inflammation-induced tissue injury. Previously, we identified protein kinase C-δ (PKCδ) as a critical controller of neutrophil activation and trafficking but how PKCδ is regulated in inflammation has not been delineated. PKCδ activity is regulated by tyrosine phosphorylation on multiple sites. Tyrosine155 is a key regulator of apoptosis and gene expression, but its role in proinflammatory signaling is not known.

METHODS

In-vitro studies - superoxide anion (O2) and neutrophil extracellular traps (NETs) were measured in bone marrow neutrophils (BMN) isolated from wild type (WT) and PKCδY155F knock-in mice (PKCδ tyrosine 155 → phenylalanine). Our novel 3D biomimetic microfluidic assay (bMFA) was used to delineate PKCδ-mediated regulation of individual steps in neutrophil adhesion and migration using WT and PKCδY155F BMN and mouse lung microvascular endothelial cells (MLMVEC). In-vivo studies - WT and PKCδY155F knock-in mice underwent sham or cecal ligation and puncture surgery and the lungs harvested 24 h post-surgery.

RESULTS

In vitro - PKCδY155F BMN had significantly reduced O2 and NETs release compared with WT. WT BMN, but not PKCδY155F BMN, demonstrated significant adhesion and migration across tumor necrosis factor-activated MLMVEC in bMFA. PKCδ inhibition significantly reduced WT BMN adhesion and migration under low shear and near bifurcations, but had no effect on PKCδY155F BMN. In vivo - mutation of PKCδ tyrosine 155 significantly decreased neutrophil migration into the lungs of septic mice.

CONCLUSIONS

PKCδ tyrosine 155 is a key phosphorylation site controlling proinflammatory signaling and neutrophil-endothelial cell interactions. These studies provide mechanistic insights into PKCδ regulation during inflammation.

Recent Advances in Microfluidic Platforms Applied in Cancer Metastasis: Circulating Tumor Cells' (CTCs) Isolation and Tumor-On-A-Chip

Cancer remains the leading cause of death worldwide despite the enormous efforts that are made in the development of cancer biology and anticancer therapeutic treatment. Furthermore, recent studies in oncology have focused on the complex cancer metastatic process as metastatic disease contributes to more than 90% of tumor-related death. In the metastatic process, isolation and analysis of circulating tumor cells (CTCs) play a vital role in diagnosis and prognosis of cancer patients at an early stage. To obtain relevant information on cancer metastasis and progression from CTCs, reliable approaches are required for CTC detection and isolation. Additionally, experimental platforms mimicking the tumor microenvironment in vitro give a better understanding of the metastatic microenvironment and antimetastatic drugs' screening. With the advancement of microfabrication and rapid prototyping, microfluidic techniques are now increasingly being exploited to study cancer metastasis as they allow precise control of fluids in small volume and rapid sample processing at relatively low cost and with high sensitivity. Recent advancements in microfluidic platforms utilized in various methods for CTCs' isolation and tumor models recapitulating the metastatic microenvironment (tumor-on-a-chip) are comprehensively reviewed. Future perspectives on microfluidics for cancer metastasis are proposed.

Application of microphysiological systems in biopharmaceutical research and development

Within the last 10 years, several tissue microphysiological systems (MPS) have been developed and characterized for retention of morphologic characteristics and specific gene/protein expression profiles from their natural in vivo state. Once developed, their utility is typically further tested by comparing responses to known toxic small-molecule pharmaceuticals in efforts to develop strategies for further toxicity testing of compounds under development. More recently, application of this technology in biopharmaceutical (large molecules) development is beginning to be more appreciated. In this review, we describe some of the advances made for tissue-specific MPS and outline the advantages and challenges of applying and further developing MPS technology in preclinical biopharmaceutical research.

Magnetic hyperthermia therapy in glioblastoma tumor on-a-Chip model

OBJECTIVE

To evaluate the magnetic hyperthermia therapy in glioblastoma tumor-on-a-Chip model using a microfluidics device.

METHODS

The magnetic nanoparticles coated with aminosilane were used for the therapy of magnetic hyperthermia, being evaluated the specific absorption rate of the magnetic nanoparticles at 300 Gauss and 305kHz. A preculture of C6 cells was performed before the 3D cells culture on the chip. The process of magnetic hyperthermia on the Chip was performed after administration of 20μL of magnetic nanoparticles (10mgFe/mL) using the parameters that generated the specific absorption rate value. The efficacy of magnetic hyperthermia therapy was evaluated by using the cell viability test through the following fluorescence staining: calcein acetoxymethyl ester (492/513nm), for live cells, and ethidium homodimer-1 (526/619nm) for dead cells dyes.

RESULTS

Magnetic nanoparticles when submitted to the alternating magnetic field (300 Gauss and 305kHz) produced a mean value of the specific absorption rate of 115.4±6.0W/g. The 3D culture of C6 cells evaluated by light field microscopy imaging showed the proliferation and morphology of the cells prior to the application of magnetic hyperthermia therapy. Fluorescence images showed decreased viability of cultured cells in organ-on-a-Chip by 20% and 100% after 10 and 30 minutes of the magnetic hyperthermia therapy application respectively.

CONCLUSION

The study showed that the therapeutic process of magnetic hyperthermia in the glioblastoma on-a-chip model was effective to produce the total cell lise after 30 minutes of therapy.

Synthesis of controlled-size silver nanoparticles for the administration of methotrexate drug and its activity in colon and lung cancer cells

A controlled synthesis of methotrexate (MTX) silver nanoparticles (AgNPs-MTX) using borohydride and citrate as reduction and reduction/capping agents, respectively, was performed in order to obtain AgNPs-MTX conjugates with a narrow size distribution. Their characterization showed polydispersed spherical shape nanoparticles with a mean size around 13 nm and distribution range between 7–21 nm. The presence of MTX was confirmed by FTIR and EDX analysis. Spectroscopic determinations suggest the chemisorption of MTX through a carboxylic group (–COOH) onto AgNPs via the exchange with a citrate molecule. Drug loading capacities calculated for AgNPs synthesized using different amounts of MTX were 28, 31 and 40%. In vitro drug release tests depicted similar release profiles for all conjugated amounts releasing between 77 to 85% of the initial MTX loaded into the AgNPs. With respect to free MTX, the addition of the nanocarrier delayed its release and also changed its pharmacokinetics. Free MTX is released after 3 hours following a first order kinetic model, whereas in the presence of AgNPs, a fast initial release is observed during the first 5 hours, followed by a plateau after 24 hours. In this case, AgNPs-MTX fitted a Higuchi model, where its solubilization is controlled by a diffusion process. Results obtained from flow cytometry of different cell lines treated with AgNPs-MTX demonstrated the combined anticancer effect of both reagents, decreasing the percentage of living cells in a colon cancer cell line (HTC-116) down to 40% after 48 hours of exposure. This effect was weaker but still significant for a lung cancer cell line (A-549). Finally, a zebrafish assay with AgNPs-MTX did not show any significant cytotoxic effect, confirming thereby the reduction of systemic drug toxicity achieved by coupling MTX to AgNPs. This observed toxicity reduction in the zebrafish model implies also a probable improvement of the usage of AgNPs-MTX in chemotherapy against human cancers.

A controlled synthesis of methotrexate (MTX) silver nanoparticles (AgNPs-MTX) using borohydride and citrate as reduction and reduction/capping agents, respectively, was performed in order to obtain AgNPs-MTX conjugates with a narrow size distribution.

Nanoparticles and Microfluidic Devices in Cancer Research

Cancer is considered the disease of the century, which can be easily understood considering its increasing incidence worldwide. Over the last years, nanotechnology has been presenting promising theranostic approaches to tackle cancer, as the development of nanoparticle-based therapies. But, regardless of the promising outcomes within in vitro settings, its translation into the clinics has been delayed. One of the main reasons is the lack of an appropriate in vitro model, capable to mimic the true environment of the human body, to test the designed nanoparticles. In fact, most of in vitro models used for the validation of nanoparticle-based therapies do not address adequately the complex barriers that naturally occur in a tumor scenario, as such as blood vessels, the interstitial fluid pressure or the interactions with surrounding cells that can hamper the proper delivery of the nanoparticles into the desired site. In this reasoning, to get a step closer to the in vivo reality, it has been proposed of the use of microfluidic devices. In fact, microfluidic devices can be designed on-demand to exhibit complex structures that mimic tissue/organ-level physiological architectures. Even so, despite microfluidic-based in vitro models do not compare with the reality and complexity of the human body, the most complex systems created up to now have been showing similar results to in vivo animal models. Microfluidic devices have been proven to be a valuable tool to accomplish more realistic tumour's environment. The recent advances in this field, and in particular, the ones enabling the rapid test of new therapies, and show great promise to be translated to the clinics will be overviewed herein.