Vesicle fusion and release in neurons under dynamic mechanical equilibrium

Vesicular fusion plays a pivotal role in cellular processes, involving stages like vesicle trafficking, fusion pore formation, content release, and membrane integration or separation. This dynamic process is regulated by a complex interplay of protein assemblies, osmotic forces, and membrane tension, which together maintain a mechanical equilibrium within the cell. Changes in cellular mechanics or external pressures prompt adjustments in this equilibrium, highlighting the system's adaptability. This review delves into the synergy between intracellular proteins, structural components, and external forces in facilitating vesicular fusion and release. It also explores how cells respond to mechanical stress, maintaining equilibrium and offering insights into vesicle fusion mechanisms and the development of neurological disorders.

Tau- and α-synuclein-targeted gold nanoparticles: applications, opportunities, and future outlooks in the diagnosis and therapy of neurodegenerative diseases

The use of nanomaterials in medicine offers multiple opportunities to address neurodegenerative disorders such as Alzheimer's and Parkinson's disease. These diseases are a significant burden for society and the health system, affecting millions of people worldwide without sensitive and selective diagnostic methodologies or effective treatments to stop their progression. In this sense, the use of gold nanoparticles is a promising tool due to their unique properties at the nanometric level. They can be functionalized with specific molecules to selectively target pathological proteins such as Tau and α-synuclein for Alzheimer's and Parkinson's disease, respectively. Additionally, these proteins are used as diagnostic biomarkers, wherein gold nanoparticles play a key role in enhancing their signal, even at the low concentrations present in biological samples such as blood or cerebrospinal fluid, thus enabling an early and accurate diagnosis. On the other hand, gold nanoparticles act as drug delivery platforms, bringing therapeutic agents directly into the brain, improving treatment efficiency and precision, and reducing side effects in healthy tissues. However, despite the exciting potential of gold nanoparticles, it is crucial to address the challenges and issues associated with their use in the medical field before they can be widely applied in clinical settings. It is critical to ensure the safety and biocompatibility of these nanomaterials in the context of the central nervous system. Therefore, rigorous preclinical and clinical studies are needed to assess the efficacy and feasibility of these strategies in patients. Since there is scarce and sometimes contradictory literature about their use in this context, the main aim of this review is to discuss and analyze the current state-of-the-art of gold nanoparticles in relation to delivery, diagnosis, and therapy for Alzheimer's and Parkinson's disease, as well as recent research about their use in preclinical, clinical, and emerging research areas.

Review on bile dynamics and microfluidic-based component detection: Advancing the understanding of bilestone pathogenesis in the biliary tract

Bilestones are solid masses found in the gallbladder or biliary tract, which block the normal bile flow and eventually result in severe life-threatening complications. Studies have shown that bilestone formation may be related to bile flow dynamics and the concentration level of bile components. The bile flow dynamics in the biliary tract play a critical role in disclosing the mechanism of bile stasis and transportation. The concentration of bile composition is closely associated with processes such as nucleation and crystallization. Recently, microfluidic-based biosensors have been favored for multiple advantages over traditional benchtop detection assays for their less sample consumption, portability, low cost, and high sensitivity for real-time detection. Here, we reviewed the developments in bile dynamics study and microfluidics-based bile component detection methods. These studies may provide valuable insights into the bilestone formation mechanisms and better treatment, alongside our opinions on the future development of in vitro lithotriptic drug screening of bilestones and bile characterization tests.

3D Inkjet-Bioprinted Lung-on-a-Chip

There is an urgent need for physiologically relevant and customizable biochip models of human lung tissue to provide a niche for lung disease modeling and drug efficacy. Although various lung-on-a-chips have been developed, the conventional fabrication method has been limited in reconstituting a very thin and multilayered architecture and spatial arrangements of multiple cell types in a microfluidic device. To overcome these limitations, we developed a physiologically relevant human alveolar lung-on-a-chip model, effectively integrated with an inkjet-printed, micron-thick, and three-layered tissue. After bioprinting lung tissues inside four culture inserts layer-by-layer, the inserts are implanted into a biochip that supplies a flow of culture medium. This modular implantation procedure enables the formation of a lung-on-a-chip to facilitate the culture of 3D-structured inkjet-bioprinted lung models under perfusion at the air-liquid interface. The bioprinted models cultured on the chip maintained their structure with three layers of tens of micrometers and achieved a tight junction in the epithelial layer, the critical properties of an alveolar barrier. The upregulation of genes involved in the essential functions of alveoli was also confirmed in our model. Our culture insert-mountable organ-on-a-chip is a versatile platform that can be applied to various organ models by implanting and replacing culture inserts. It is amenable to mass production and the development of customized models through the convergence with bioprinting technology.

Recent developments in organ-on-a-chip technology for cardiovascular disease research

Cardiovascular diseases are a group of heart and blood vessel disorders which remain a leading cause of morbidity and mortality worldwide. Currently, cardiovascular disease research commonly depends on in vivo rodent models and in vitro human cell culture models. Despite their widespread use in cardiovascular disease research, there are some long-standing limitations: animal models often fail to faithfully mimic human response, while traditional cell models ignore the in vivo microenvironment, intercellular communications, and tissue-tissue interactions. The convergence of microfabrication and tissue engineering has given rise to organ-on-a-chip technologies. The organ-on-a-chip is a microdevice containing microfluidic chips, cells, and extracellular matrix to reproduce the physiological processes of a certain part of the human body, and is nowadays considered a promising bridge between in vivo models and in vitro 2D or 3D cell culture models. Considering the difficulty in obtaining human vessel and heart samples, the development of vessel-on-a-chip and heart-on-a-chip systems can guide cardiovascular disease research in the future. In this review, we elaborate methods and materials to fabricate organ-on-a-chip systems and summarize the construction of vessel and heart chips. The construction of vessels-on-a-chip must consider the cyclic mechanical stretch and fluid shear stress, while hemodynamic forces and cardiomyocyte maturation are key factors in building hearts-on-a-chip. We also introduce the application of organs-on-a-chip in cardiovascular disease study.

Construction and Application of in vitro Alveolar Models Based on 3D Printing Technology

Increasing lung diseases, mutating coronaviruses, and the development of new compounds urgently require biomimetic in vitro lung models for lung pathology, toxicology, and pharmacology. The current construction strategies for lung models mainly include animal models, 2D cell culture, lung-on-a-chip, and lung organoids. However, current models face difficulties in reproducing in vivo-like alveolar size and vesicle-like structures, and are unable to contain multiple cell types. In this study, a strategy for constructing alveolar models based on degradable hydrogel microspheres is proposed. Hydrogel microspheres, 200–250 µm in diameter, were prepared using a self-developed printing technique driven by alternating viscous and inertial forces. Microcapsules were further constructed using a coacervation-based layer-by-layer technique and core liquefaction. Three types of cells were inoculated and co-cultured on hydrogel capsules based on optimized microcapsule surface treatment strategies. Finally, an in vitro three-dimensional endothelial alveolar model with a multicellular composition and vesicle-like structure with a diameter of approximately 230 µm was successfully constructed. Cells in the constructed alveolar model maintained a high survival rate. The LD₅₀ values of glutaraldehyde based on the constructed models were in good agreement with the reference values, validating the potential of the model for future toxicant and drug detection.

Population genetics in microchannels

Many microbial populations proliferate in small channels. In such environments, reproducing cells organize in parallel lanes. Reproducing cells shift these lanes, potentially expelling other cells from the channel. In this paper, we combine theory and experiments to understand how these dynamics affects the diversity of a microbial population. We theoretically predict that genetic diversity is quickly lost along lanes of cells. Our experiments confirm that a population of proliferating Escherichia coli in a microchannel organizes into lanes of genetically identical cells within a few generations. Our findings elucidate the effect of lane formation on populations evolution, with potential applications ranging from microbial ecology in soil to dynamics of epithelial tissues in higher organisms.

Spatial constraints, such as rigid barriers, affect the dynamics of cell populations, potentially altering the course of natural evolution. In this paper, we investigate the population genetics of Escherichia coli proliferating in microchannels with open ends. Our analysis is based on a population model, in which reproducing cells shift entire lanes of cells toward the open ends of the channel. The model predicts that diversity is lost very rapidly within lanes but at a much slower pace among lanes. As a consequence, two mixed, neutral E. coli strains competing in a microchannel must organize into an ordered regular stripe pattern in the course of a few generations. These predictions are in quantitative agreement with our experiments. We also demonstrate that random mutations appearing in the middle of the channel are much more likely to reach fixation than those occurring elsewhere. Our results illustrate fundamental mechanisms of microbial evolution in spatially confined space.

Applied Hepatic Bioengineering: Modeling the Human Liver Using Organoid and Liver-on-a-Chip Technologies

The liver is the most important metabolic hub of endo and xenobiotic compounds. Pre-clinical studies using rodents to evaluate the toxicity of new drugs and cosmetics may produce inconclusive results for predicting clinical outcomes in humans, moreover being banned in the European Union. Human liver modeling using primary hepatocytes presents low reproducibility due to batch-to-batch variability, while iPSC-derived hepatocytes in monolayer cultures (2D) show reduced cellular functionality. Here we review the current status of the two most robust in vitro approaches in improving hepatocyte phenotype and metabolism while mimicking the hepatic physiological microenvironment: organoids and liver-on-chip. Both technologies are reviewed in design and manufacturing techniques, following cellular composition and functionality. Furthermore, drug screening and liver diseases modeling efficiencies are summarized. Finally, organoid and liver-on-chip technologies are compared regarding advantages and limitations, aiming to guide the selection of appropriate models for translational research and the development of such technologies.

Micro/nanofluidic devices for drug delivery

Micro/nanofluidic drug delivery systems have attracted significant attention as they offer unique advantages in targeted and controlled drug delivery. Based on the desired application, these systems can be categorized into three different groups: in vitro, in situ and in vivo microfluidic drug delivery platforms. In vitro microfluidic drug delivery platforms are closely linked with the emerging concept of lab-on-a-chip for cell culture studies. These systems can be used to administer drugs or therapeutic agents, mostly at the cellular or tissue level, to find the therapeutic index and can potentially be used for personalized medicine. In situ and in vivo microfluidic drug delivery platforms are still at the developmental stage and can be used for drug delivery at tissue or organ levels. A famous example of these systems are microneedles that can be used for painless and controllable delivery of drugs or vaccines through human skin. This chapter presents the cutting edge advances in the design and fabrication of in vitro microfluidic drug delivery systems that can be used for both cellular and tissue drug delivery. It also briefly discusses the in situ drug delivery platforms using microneedles.

Microfluidics for Drug Development: From Synthesis to Evaluation

Drug development is a long process whose main content includes drug synthesis, drug delivery, and drug evaluation. Compared with conventional drug development procedures, microfluidics has emerged as a revolutionary technology in that it offers a miniaturized and highly controllable environment for bio(chemical) reactions to take place. It is also compatible with analytical strategies to implement integrated and high-throughput screening and evaluations. In this review, we provide a comprehensive summary of the entire microfluidics-based drug development system, from drug synthesis to drug evaluation. The challenges in the current status and the prospects for future development are also discussed. We believe that this review will promote communications throughout diversified scientific and engineering communities that will continue contributing to this burgeoning field.

Transforming a well into a chip: A modular 3D-printed microfluidic chip

Organ-on-a-Chip platforms provide rich opportunities to observe interactions between different cell types under in vivo-like conditions, i.e., in the presence of flow. Yet, the costs and know-how required for the fabrication and implementation of these platforms restrict their accessibility. This study introduces and demonstrates a novel Insert-Chip: a microfluidic device that provides the functionality of an Organ-on-a-Chip platform, namely, the capacity to co-culture cells, expose them to flow, and observe their interactions-yet can easily be integrated into standard culture systems (e.g., well plates or multi-electrode arrays). The device is produced using stereolithograpy 3D printing and is user-friendly and reusable. Moreover, its design features overcome some of the measurement and imaging challenges characterizing standard Organ-on-a-Chip platforms. We have co-cultured endothelial and epithelial cells under flow conditions to demonstrate the functionality of the device. Overall, this novel microfluidic device is a promising platform for the investigation of biological functions, cell-cell interactions, and response to therapeutics.

A Paradigm Shift in Tissue Engineering: From a Top–Down to a Bottom–Up Strategy

Tissue engineering (TE) was initially designed to tackle clinical organ shortage problems. Although some engineered tissues have been successfully used for non-clinical applications, very few (e.g., reconstructed human skin) have been used for clinical purposes. As the current TE approach has not achieved much success regarding more broad and general clinical applications, organ shortage still remains a challenging issue. This very limited clinical application of TE can be attributed to the constraints in manufacturing fully functional tissues via the traditional top–down approach, where very limited cell types are seeded and cultured in scaffolds with equivalent sizes and morphologies as the target tissues. The newly proposed developmental engineering (DE) strategy towards the manufacture of fully functional tissues utilises a bottom–up approach to mimic developmental biology processes by implementing gradual tissue assembly alongside the growth of multiple cell types in modular scaffolds. This approach may overcome the constraints of the traditional top–down strategy as it can imitate in vivo-like tissue development processes. However, several essential issues must be considered, and more mechanistic insights of the fundamental, underpinning biological processes, such as cell–cell and cell–material interactions, are necessary. The aim of this review is to firstly introduce and compare the number of cell types, the size and morphology of the scaffolds, and the generic tissue reconstruction procedures utilised in the top–down and the bottom–up strategies; then, it will analyse their advantages, disadvantages, and challenges; and finally, it will briefly discuss the possible technologies that may overcome some of the inherent limitations of the bottom–up strategy.

A multilayered cancer-on-a-chip model to analyze the effectiveness of new-generation photosensitizers

Three-dimensional (3D) cellular models of cancer tissue are necessary tools to analyze new anticancer drugs under in vitro conditions. Diagnostics and treatment of ovarian cancer are major challenges for current medicine. In our report we propose a new three-dimensional (3D) cellular model of ovarian cancer which can mimic a fragment of heterogeneous cancer tissue. We used Lab-on-a-chip technology to create a microfluidic system that allows cellular multilayer to be cultured. Cellular multilayer mimics the structure of two important elements of cancer tissue: flesh and stroma. For this reason, it has an advantage over other in vitro cellular models. We used human ovarian fibroblasts (HOF) and human ovarian cancer cells in our research (A2780). In the first stage of the study, we proved that the presence of non-malignant fibroblasts in co-culture with ovarian cancer cells stimulates the proliferation of cancer cells, which is important in the progression of ovarian cancer. In the next stage of the research, we tested the usefulness of the newly-developed cellular model in the analysis of anticancer drugs and therapies under in vitro conditions. We tested two photosensitizers (PS): free and nanoencapsulated meso-tetrafenylporphyrin, and we evaluated the potential of these drugs in anticancer photodynamic therapy (PDT) of ovarian cancer. We also studied the mechanism of PDT based on the analysis of the level of reactive oxygen species (ROS) in cell cultures. Our research confirmed that the use of new-generation PS can significantly increase the efficacy of PDT in the treatment of ovarian cancer. We also proved that the newly-developed 3D cellular model is suitable for rapid screening of anticancer drugs and has the potential to be used clinically in the future, e.g. in the selection of treatment methods for anticancer personalized medicine.

Angiogenic responses in a 3D micro-engineered environment of primary endothelial cells and pericytes

Angiogenesis plays a key role in the pathology of diseases such as cancer, diabetic retinopathy, and age-related macular degeneration. Understanding the driving forces of endothelial cell migration and organization, as well as the time frame of these processes, can elucidate mechanisms of action of important pathological pathways. Herein, we have developed an organ-specific microfluidic platform recapitulating the in vivo angiogenic microenvironment by co-culturing mouse primary brain endothelial cells with brain pericytes in a three-dimensional (3D) collagen scaffold. As a proof of concept, we show that this model can be used for studying the angiogenic process and further comparing the angiogenic properties between two different common inbred mouse strains, C57BL/6J and 129S1/SvlmJ. We further show that the newly discovered angiogenesis-regulating gene Padi2 promotes angiogenesis through Dll4/Notch1 signaling by an on-chip mechanistic study. Analysis of the interplay between primary endothelial cells and pericytes in a 3D microfluidic environment assists in the elucidation of the angiogenic response.

Micropatterned Coculture Platform for Screening Nerve-Related Anticancer Drugs

Accumulating evidence suggests that the neural microenvironment plays a vital role in the development and metastasis of cancers. The development of drug candidates or drug combinations targeting the neural microenvironment is thus becoming increasingly urgent. However, the low content of conventional drug screening platforms is a bottleneck that limits the drug evaluation process. In this study, we present a micropatterned coculture-based high-content (μCHC) platform by integrating a micropatterned coculture chip with the high-content analysis (HCA) system, for studying the neuron-cancer cell interactions and drug screening (simultaneously detecting 96 kinds of post-drug-treated conditions). We investigate the contribution of neurons on the migration of cancer cells from different tissues and validate the capability of the μCHC system to study the interaction between neurons and cancer cells. Moreover, we test the effects of individual or combinatory agents targeting the neuron or cancer cell on the neuron-cancer cell interactions, which proposes an optimized therapy regime for targeting both nervous and cancerous factors. Our study suggests that the μCHC system is a facile platform for screening drug candidates or drug combinations for clinical cancer therapy with high efficiency and fidelity.

A new drug testing platform based on 3D tri-culture in lab-on-a-chip devices

Drug discovery has a 90% rate of failure because preclinical platforms for drug testing do not mimic the in vivo conditions. Doxorubicin (DOX) is a commonly used drug to treat breast cancer patients even though it has side effects. Lab-on-a-chip (LOC) devices provide spatial control at the micrometer scale and can thus emulate the cancer microenvironment. Here, using a multidisciplinary approach, a new drug testing platform based on 3D tri-culture in LOC devices was developed. Breast cancer cells alone or with normal mammary epithelial cells and macrophages were cultured in matrigel in LOC devices. The platform was used to test DOX and (R)-4'-methylklavuzon (KLA), which is a new anti-cancer drug candidate. Results showed that DOX and KLA were equally effective on breast cancer cells in 3D monoculture. KLA produced 26% less death for breast cancer cells than DOX in 3D tri-culture. More importantly, DOX was not selective between breast cancer cells and normal mammary epithelial cells in 3D tri- culture whereas KLA caused 56% less cell death than DOX for normal mammary epithelial cells. Results strongly recommend that 3D tri-culture in LOC devices be used for assessment of drug toxicity at the preclinical stage.

Microfluidic organ-on-a-chip models of human liver tissue

The liver is the largest internal organ of the body with complex microarchitecture and function that plays critical roles in drug metabolism. Hepatotoxicity and drug-induced liver injury (DILI) caused by various drugs is the main reason for late-stage drug failures. Moreover, liver diseases are among the leading causes of death in the world, with the number of new cases arising each year. Although animal models have been used to understand human drug metabolism and toxicity before clinical trials, tridimensional microphysiological systems, such as liver-on-a-chip (Liver Chip) platforms, could better recapitulate features of human liver physiology and pathophysiology and thus, are often more predictive of human outcome. Liver Chip devices have shown promising results in mimicking in vivo condition by recapitulating the sinusoidal structure of the liver, maintaining high cell viability and cellular phenotypes, and emulating native liver functions. Here, we first review the cellular constituents and physiology of the liver and then critically discuss the state-of-the-art chip-based liver models and their applications in drug screening, disease modeling, and regenerative medicine. We finally address the pending issues of existing platforms and touch upon future directions for developing new, advanced on-chip models.

Mesenchymal Stem Cells as a Promising Cell Source for Integration in Novel In Vitro Models

The human-relevance of an in vitro model is dependent on two main factors-(i) an appropriate human cell source and (ii) a modeling platform that recapitulates human in vivo conditions. Recent years have brought substantial advancements in both these aspects. In particular, mesenchymal stem cells (MSCs) have emerged as a promising cell source, as these cells can differentiate into multiple cell types, yet do not raise the ethical and practical concerns associated with other types of stem cells. In turn, advanced bioengineered in vitro models such as microfluidics, Organs-on-a-Chip, scaffolds, bioprinting and organoids are bringing researchers ever closer to mimicking complex in vivo environments, thereby overcoming some of the limitations of traditional 2D cell cultures. This review covers each of these advancements separately and discusses how the integration of MSCs into novel in vitro platforms may contribute enormously to clinical and fundamental research.

Lung-on-a-chip: the future of respiratory disease models and pharmacological studies

Recently, organ-on-a-chip models, which are microfluidic devices that mimic the cellular architecture and physiological environment of an organ, have been developed and extensively investigated. The chips can be tailored to accommodate the disease conditions pertaining to many organs; and in the case of this review, the lung. Lung-on-a-chip models result in a more accurate reflection compared to conventional in vitro models. Pharmaceutical drug testing methods traditionally use animal models in order to evaluate pharmacological and toxicological responses to a new agent. However, these responses do not directly reflect human physiological responses. In this review, current and future applications of the lung-on-a-chip in the respiratory system will be discussed. Furthermore, the limitations of current conventional in vitro models used for respiratory disease modeling and drug development will be addressed. Highlights of additional translational aspects of the lung-on-a-chip will be discussed in order to demonstrate the importance of this subject for medical research.

Animal tissue culture principles and applications

Animal cell culture technology in today’s scenario has become indispensable in the field of life sciences, which provides a basis to study regulation, proliferation, and differentiation and to perform genetic manipulation. It requires specific technical skills to carry out successfully. This chapter describes the essential techniques of animal cell culture as well as its applications.

Nanoconjugates of graphene oxide derivatives and meso-tetraphenylporphyrin: a new avenue for anticancer photodynamic therapies – Cell-on-a-Chip analysis

Cell-on-a-Chip analysis of nanoconjugates of graphene oxide derivatives and mesotetraphenylporphyrin as a new selective and effective avenue for anticancer photodynamic therapies.

Recent Progress in Lab-On-a-Chip Systems for the Monitoring of Metabolites for Mammalian and Microbial Cell Research

Lab-on-a-chip sensing technologies have changed how cell biology research is conducted. This review summarises the progress in the lab-on-a-chip devices implemented for the detection of cellular metabolites. The review is divided into two subsections according to the methods used for the metabolite detection. Each section includes a table which summarises the relevant literature and also elaborates the advantages of, and the challenges faced with that particular method. The review continues with a section discussing the achievements attained due to using lab-on-a-chip devices within the specific context. Finally, a concluding section summarises what is to be resolved and discusses the future perspectives.

Development of a Microfluidic Culture Paradigm for Ex Vivo Maintenance of Human Glioblastoma Tissue: A New Glioblastoma Model?

BACKGROUND: One way to overcome the genetic and molecular variations within glioblastoma is to treat each tumour on an individual basis. To facilitate this, we have developed a microfluidic culture paradigm that maintains human glioblastoma tissue ex vivo. METHODS: The assembled device, fabricated using a photolithographic process, is composed of two layers of glass bonded together to contain a tissue chamber and a network of microchannels that allow continued tissue perfusion. RESULTS: A total of 128 tissue biopsies (from 33 patients) were maintained in microfluidic devices for an average of 72 hours. Tissue viability (measured with Annexin V and propidium iodide) was 61.1% in tissue maintained on chip compared with 68.9% for fresh tissue analysed at commencement of the experiments. Other biomarkers, including lactate dehydrogenase absorbance and trypan blue exclusion, supported the viability of the tissue maintained on chip. Histological appearances remained unchanged during the tissue maintenance period, and immunohistochemical analysis of Ki67 and caspase 3 showed no significant differences when compared with fresh tissues. A trend showed that tumours associated with poorer outcomes (recurrent tumours and Isocitrate Dehydrogenase - IDH wildtype) displayed higher viability on chip than tumours linked with improved outcomes (low-grade gliomas, IDH mutants and primary tumours). conclusions: This work has demonstrated for the first time that human glioblastoma tissue can be successfully maintained within a microfluidic device and has the potential to be developed as a new platform for studying the biology of brain tumours, with the long-term aim of replacing current preclinical GBM models and facilitating personalised treatments.

Cell-Based Assays on Microfluidics for Drug Screening

Microfluidics is an appealing platform for drug screening and discovery. Compared with the conventional drug screening methods based on Petri dishes and experimental animals, microfluidic devices have many advantages including miniaturized size, ease-to-use, high sensitivity, and high throughput. More importantly, bioassays on microfluidics can avoid ethical issues which can be a big obstacle hindering the performance of the experiments on animals or human being. Furthermore, three-dimensional (3D) microchips can recapitulate various biochemical and biophysical conditions in vivo and mimic the natural microenvironment of the tissues/organs, providing versatile in vitro models for biomedical applications. In this Perspective, we will focus on the cell-based microfluidic assays for drug screening. Meanwhile, we also propose potential solutions for the difficulties in this field and discuss the prospects of microfluidics-based technologies for drug screening.

Lab-on-a-chip systems for photodynamic therapy investigations

In recent years photodynamic therapy (PDT) has received widespread attention in cancer treatment due to its smaller surgical trauma, better selectivity towards tumor cells, reduced side effects and possibility of repeatable treatment. Since cancer is the second cause of death worldwide, scientists constantly seek for new potential therapeutic agents including nanotechnology-based photosensitizers used in PDT. The new-designed nanostructures must be carefully studied and well characterized what require analytically useful and powerful tools that enable real progress in nanoscience development. This review describes the current status of PDT investigations using microfluidic Lab-on-a-Chip systems, including recent developments of nanoparticle-based PDT agents, their combinations with different drugs, designs and examples of in vitro applications. This review mainly lays emphasis on biological evaluation of FDA approved photosensitizing agents as well as newly designed nanophotosensitizers. It also highlights the analytical performances of various microfluidic Lab-on-a-chip systems for PDT efficacy analysis on 3D culture and discusses microsystems designs in detail.

Rapid Prototyping of a Cyclic Olefin Copolymer Microfluidic Device for Automated Oocyte Culturing

Assisted reproductive technology (ART) can benefit from the features of microfluidic technologies, such as the automation of time-consuming labor-intensive procedures, the possibility to mimic in vivo environments, and the miniaturization of the required equipment. To date, most of the proposed approaches are based on polydimethylsiloxane (PDMS) as platform substrate material due to its widespread use in academia, despite certain disadvantages, such as the elevated cost of mass production. Herein, we present a rapid fabrication process for a cyclic olefin copolymer (COC) monolithic microfluidic device combining hot embossing—using a low-temperature cofired ceramic (LTCC) master—and micromilling. The microfluidic device was suitable for trapping and maturation of bovine oocytes, which were further studied to determine their ability to be fertilized. Furthermore, another COC microfluidic device was fabricated to store sperm and assess its quality parameters over time. The study herein presented demonstrates a good biocompatibility of the COC when working with gametes, and it exhibits certain advantages, such as the nonabsorption of small molecules, gas impermeability, and low fabrication costs, all at the prototyping and mass production scale, thus taking a step further toward fully automated microfluidic devices in ART.

3D lung spheroid cultures for evaluation of photodynamic therapy (PDT) procedures in microfluidic Lab-on-a-Chip system

The purpose of this paper is to present a fully integrated microchip for the evaluation of PDT procedures efficiency on 3D lung spheroid cultures. Human lung carcinoma A549 and non-malignant MRC-5 spheroids were utilized as culture models. Spheroid viability was evaluated 24 h after PDT treatment, in which 5-aminolevulinic acid (ALA) had been used as a precursor of a photosensitizer (protoporphyrin IX - PpIX). Moreover, spheroid viability over a long-term (10-day) culture was also examined. We showed that the proposed PDT treatment was toxic only for cancer spheroids. This could be because of a much-favoured enzymatic conversion of ALA to PpIX in cancer as opposed normal cells. Moreover, we showed that to obtain high effectiveness of ALA-PDT on lung cancer spheroids additional time of spheroid after light exposure was required. It was found that PDT had been effective 5 days after PDT treatment with 3 mM ALA. To the best of our knowledge this has been the first presentation of such research performed on a 3D lung spheroids culture in a microfluidic system.

Rapid large area fabrication of multiscale through-hole membranes

There are many proposed mechanisms by which single cells can be trapped; among them is the through-hole membrane for the characterization of individual microorganisms. Due to the small scale of the fabricated pores, the construction of through-hole membranes on a large scale and with relatively large areas faces many difficulties. This paper describes novel fabrication methods for a large-area, freestanding micro/nano through-hole membrane constructed from versatile membrane materials using through-hole membranes on a microfluidic chip (THMMC). This process can rapidly (<20 min) fabricate membranes with high fidelity multiscale hole size without residual layers. The through-hole site was easily customizable from the micro to the nanoscale, with a low or high aspect ratio giving rise to reliable membranes. Also, the rigidity and biocompatibility of the through-hole membrane are easily tunable by simple injection of versatile membrane materials to obtain a large area (up to 3600 mm²). Membranes produced in this manner were then applied as a proof of concept for the isolation, cultivation, and quantification of individual micro-algal cells for selection with respect to the growth rate, while controlling the quorum sensing mediated metabolic and proliferative changes.

Human microRNA-299-3p decreases invasive behavior of cancer cells by downregulation of Oct4 expression and causes apoptosis

PURPOSE

Oct4 was reported to be one of the most important pluripotency transcription factors in the biology of stem cells including cancer stem cells, and progressed malignant cells. Here we report the investigation of gene expression control of Oct4 by selected human microRNAs and the physiological effect of Oct4 silencing in invasive cancer cells.

METHODS AND RESULTS

High throughput luciferase activity assay revealed the microRNA-299-3p to be the most effective in reducing gene expression of Oct4, which was confirmed by Western blot analysis and Oct4 promoter activity in a target luciferase assay. Furthermore, it could be demonstrated that downregulation of Oct4 by microRNAs-299-3p in breast cancer and fibrosarcoma cells lead to a decreased invasiveness in a microfluidic chip assay. Additionally, microRNA-299-3p causes apoptosis in cancer cells. Comparison with Oct4 specific siRNA transfection confirmed that this effect is primary due to the blockade of Oct4 expression.

CONCLUSION

The results suggest that microRNA-299-3p is an interesting target for potential clinical use. It may be able to decrease invasive behaviour of carcinoma cells; or even kill these cells by causing apoptosis.

A549 and MRC-5 cell aggregation in a microfluidic Lab-on-a-chip system

In this paper, we present a culture of A549 and MRC-5 spheroids in a microfluidic system. The aim of our work was to develop a good lung cancer model for the evaluation of drug cytotoxicity. Our research was focused on determining the progress of cell aggregation depending on such factors as the depth of culture microwells in the microdevices, a different flow rate of the introduced cell suspensions, and the addition of collagen to cell suspensions. We showed that these factors had a significant influence on spheroid formation. It was found that both MRC-5 and A549 cells exhibited higher aggregation in 500 μm microwells. We also noticed that collagen needs to be added to A549 cells to form the spheroids. Optimizing the mentioned parameters allowed us to form 3D lung tissue models in the microfluidic system during the 10-day culture. This study indicates how important an appropriate selection of the specified parameters is (e.g., geometry of the microwells in the microsystem) to obtain the spheroids characterized by high viability in the microfluidic system.

Rapid Prototyping of a Cyclic Olefin Copolymer Microfluidic Device for Automated Oocyte Culturing

Assisted reproductive technology (ART) can benefit from the features of microfluidic technologies, such as the automation of time-consuming labor-intensive procedures, the possibility to mimic in vivo environments, and the miniaturization of the required equipment. To date, most of the proposed approaches are based on polydimethylsiloxane (PDMS) as platform substrate material due to its widespread use in academia, despite certain disadvantages, such as the elevated cost of mass production. Herein, we present a rapid fabrication process for a cyclic olefin copolymer (COC) monolithic microfluidic device combining hot embossing-using a low-temperature cofired ceramic (LTCC) master-and micromilling. The microfluidic device was suitable for trapping and maturation of bovine oocytes, which were further studied to determine their ability to be fertilized. Furthermore, another COC microfluidic device was fabricated to store sperm and assess its quality parameters over time. The study herein presented demonstrates a good biocompatibility of the COC when working with gametes, and it exhibits certain advantages, such as the nonabsorption of small molecules, gas impermeability, and low fabrication costs, all at the prototyping and mass production scale, thus taking a step further toward fully automated microfluidic devices in ART.

The severe impact of in vivo-like microfluidic flow and the influence of gemini surfactants on amyloid aggregation of hen egg white lysozyme

The formation of amyloid plaques is being intensively studied, as this process underlies severe human diseases, including Alzheimer's disease, and the exact mechanism of this specific aggregation has not been resolved yet.

Confined Gelatin Dehydration as a Viable Route To Go Beyond Micromilling Resolution and Miniaturize Biological Assays

Nowadays, microfluidic channels of a few tens of micrometers are required and widely used in many fields, especially for surface-processing applications and miniaturization of biological assays. Herein, we selected micromilling as a low-cost technology and proposed an approach capable of overcoming its limitations; in fact, microstructures below 20-30 μm in depth are difficult to obtain, and the manufacturing error is rather high, as it is inversely proportional to the depth. Indeed, the proposed method uses a confined dehydration process of a patterned gelatin substrate fabricated via replica molding onto a micromilled poly(methyl methacrylate) substrate to produce a gelatin master with demonstrated final micrometric features down to 3 μm for the channel depth and, in specific configurations, down to 5 μm for the channel width. Finally, we demonstrated the ability to flux liquids in miniaturized microfluidic devices and fabricated and tested-as an example-micrometric microstructures arrays connected via microchannels for biological assays.

Features of Microsystems for Cultivation and Characterization of Stem Cells with the Aim of Regenerative Therapy

Stem cells have infinite potential for regenerative therapy thanks to their advantageous ability which is differentiable to requisite cell types for recovery and self-renewal. The microsystem has been proved to be more helpful to stem cell studies compared to the traditional methods, relying on its advantageous feature of mimicking in vivo cellular environments as well as other profitable features such as minimum sample consumption for analysis and multiprocedures. A wide variety of microsystems were developed for stem cell studies; however, regenerative therapy-targeted applications of microtechnology should be more emphasized and gain more attractions since the regenerative therapy is one of ultimate goals of biologists and bioengineers. In this review, we introduce stem cell researches harnessing well-known microtechniques (microwell, micropattern, and microfluidic channel) in view point of physical principles and how these systems and principles have been implemented appropriately for characterizing stem cells and finding possible regenerative therapies. Biologists may gain information on the principles of microsystems to apply them to find solutions for their current challenges, and engineers may understand limitations of the conventional microsystems and find new chances for further developing practical microsystems. Through the well combination of engineers and biologists, the regenerative therapy-targeted stem cell researches harnessing microtechnology will find better suitable treatments for human disorders.

Application of a microfluidic-based perivascular tumor model for testing drug sensitivity in head and neck cancers and toxicity in endothelium

A drug sensitivity test prior to clinical treatment is necessary for individualized cancer therapy.

Comparative cell adhesion properties of cysteine extended peptide architectures

This study presents the comparative cell attachment investigation of TAT and well-known RGD peptide modified surfaces.

Scalable lithography from Natural DNA Patterns via polyacrylamide gel

A facile strategy for fabricating scalable stamps has been developed using cross-linked polyacrylamide gel (PAMG) that controllably and precisely shrinks and swells with water content. Aligned patterns of natural DNA molecules were prepared by evaporative self-assembly on a PMMA substrate, and were transferred to unsaturated polyester resin (UPR) to form a negative replica. The negative was used to pattern the linear structures onto the surface of water-swollen PAMG, and the pattern sizes on the PAMG stamp were customized by adjusting the water content of the PAMG. As a result, consistent reproduction of DNA patterns could be achieved with feature sizes that can be controlled over the range of 40%–200% of the original pattern dimensions. This methodology is novel and may pave a new avenue for manufacturing stamp-based functional nanostructures in a simple and cost-effective manner on a large scale.

Development of cell metabolite analysis on microfluidic platform

Cell metabolite analysis is of great interest to analytical chemists and physiologists, with some metabolites having been identified as important indicators of major diseases such as cancer. A high-throughput and sensitive method for drug metabolite analysis will largely promote the drug discovery industry. The basic barrier of metabolite analysis comes from the interference of complex components in cell biological system and low abundance of target substances. As a powerful tool in biosample analysis, microfluidic chip enhances the sensitivity and throughput by integrating multiple functional units into one chip. In this review, we discussed three critical steps of establishing functional microfluidic platform for cellular metabolism study. Cell in vitro culture model, on chip sample pretreatment, and microchip combined detectors were described in details and demonstrated by works in five years. And a brief summary was given to discuss the advantages as well as challenges of applying microchip method in cell metabolite and biosample analysis.