Construction of Tumor Tissue Array on An Open-Access Microfluidic Chip

An open-access microfluidic chip which enabled automatic cell distribution and complex multi-step operations was developed. The microfluidic chip featured a key structure in which a nanoporous membrane was sandwiched by a cell culture chamber array layer and a corresponding media reservoir array layer. The microfluidic approach took advantage of the characteristics of nanoporous membrane. On one side, this membrane permitted the flow of air but not liquid, thus acting as a flow-stop valve to enable automatic cell distribution. On the other side, it allowed diffusion-based media exchange and thus, mimicked the endothelial layer. In synergy with a liquid transferring platform, the open-access microfluidic system enabled complex multi-step operations involving medium exchange, drug treatment, and cell viability testing. By using this microfluidic protocol, a 10 × 10 tissue arrays was constructed in 90 s, followed by schedule-dependent drug testing. Morphological and immunohistochemical assays results indicated that the resultant tumor tissue was faithful to that in vivo. Drug testing assays showed that the microfluidic tissue array promised multi-step cell assays under biomimetic microenvironment, thus providing an advantageous tool for cell research.     

Integration of intra- and extravasation in one cell-based microfluidic chip for the study of cancer metastasis

Most studies of cancer metastasis focus on cancer cell invasion utilizing adhesion assays that are performed independently, and are thus limited in their ability to mimic complex cancer metastasis on a chip. Here we report the development of an integrated cell-based microfluidic chip for intra- and extravasation that combines two assays on one chip for the study of the complex cascade of cancer metastasis. This device consists of two parts; one is an intravasation chamber for the three-dimensional (3-D) culture of cancer cells using a Matrigel matrix, and the other is an extravasation chamber for the detection of metastasized cancer cells by adhesion molecules expressed by epithelial cells. In this novel system, the intravasation and extravasation processes of cancer metastasis can be studied simultaneously using four screw valves. Metastatic LOVO and non-metastatic SW480 cells were used in this study, and the invasion of LOVOs was found to be higher compared to SW480. In contrast, invasion of cells treated with metalloproteinase (MMP) inhibitors decreased within the intravasation chamber. Degraded cancer cells from the intravasation chamber were detected within the extravasation chamber under physiological conditions of shear stress, and differences in binding efficiency were also detected when CA19-9 antibody, an inhibitor of cancer cell adhesion, was used to treat degraded cancer cells. Our results support the potential usefulness of this new 3D cell-based microfluidic system as a drug screening tool to select targets for the development of new drugs and to verify their effectiveness.     

Low-cost polymer-film spiral inertial microfluidic device for label-free separation of malignant tumor cells

We developed a low-cost polymer-film spiral inertial microfluidic device for the effective size-dependent separation of malignant tumor cells. The device was fabricated in polymer films by rapid laser cutting and chemical bonding. After fabricating the prototype device, the separation performance of our device was evaluated using particles and cells. The effects of operational flow rate, cell diameter, and cell concentration on the separation performance were explored. Our device successfully separated tumor cells from polydisperse white blood cells according to their different migration modes and lateral positions. Then, the separation of rare cells was carried out using the high-concentration lysed blood spiked with 200 tumor cells. Experimental results showed that 83.90% of the tumor cells could be recovered, while 99.87% of white blood cells could be removed. We successfully employed our device for processing clinical pleural effusion samples from patients with advanced metastatic breast cancer. Malignant tumor cells with an average purity of 2.37% could be effectively enriched, improving downstream diagnostic accuracy. Our device offers the advantages of label-free operation, low cost, and fast fabrication, thus being a potential tool for effective cell separation.     

Hydrogel microfluidic co‐culture device for photothermal therapy and cancer migration

We developed the photo‐crosslinkable hydrogel microfluidic co‐culture device to study photothermal therapy and cancer cell migration. To culture MCF7 human breast carcinoma cells and metastatic U87MG human glioblastoma in the microfluidic device, we used 10 w/v% gelatin methacrylate (GelMA) hydrogels as a semi‐permeable physical barrier. We demonstrated the effect of gold nanorod on photothermal therapy of cancer cells in the microfluidic co‐culture device. Interestingly, we observed that metastatic U87MG human glioblastoma largely migrated toward vascular endothelial growth factor (VEGF)‐treated GelMA hydrogel‐embedding microchannels. The main advantage of this hydrogel microfluidic co‐culture device is to simultaneously analyze the physiological migration behaviors of two cancer cells with different physiochemical motilities and study gold nanorod‐mediated photothermal therapy effect. Therefore, this hydrogel microfluidic co‐culture device could be a potentially powerful tool for photothermal therapy and cancer cell migration applications.     

An Enzyme-Loaded Metal–Organic Framework-Assisted Microfluidic Platform Enables Single-Cell Metabolite Analysis

Colonization of cancer cells at secondary sites, a decisive step in tumor metastasis, is strongly dependent on the formation of metastatic microenvironments regulated by intrinsic single-cell metabolism traits. Herein, we report a single-cell microfluidic platform for high-throughput dynamic monitoring of tumor cell metabolites to evaluate tumor malignancy. This microfluidic device empowers efficient isolation of single cells (>99 %) in a squashed state similar to tumor extravasation, and employs enzyme-packaged metal–organic frameworks to catalyze tumor cell metabolites for visualization. The microfluidic evaluation was confirmed by in vivo assays, suggesting that the platform allowed predicting the tumorigenicity of captured tumor cells and screening metabolic inhibitors as anti-metastatic drugs. Furthermore, the platform efficiently detected various aggressive cancer cells in unprocessed whole blood samples with high sensitivity, showing potential for clinical application.     

Characterization of the interaction between fibroblasts and tumor cells on a microfluidic co‐culture device

Fibroblasts and tumor cells have been involved in the process of cancer development, progression and therapy. Here, we present a simple microfluidic device which enables to study the interaction between fibroblasts and tumor cells by indirect contact co‐culture. The device is composed of multiple cell culture chambers which are connected by a parallel of cell migration regions, and it enables to realize different types of cells to communicate each other on the single device. In this work, human embryonic lung fibroblasts cells were observed to exhibit obvious migration towards tumor cells instead of normal epithelial cells on the co‐culture device. Moreover, transdifferentiation of human embryonic lung fibroblast cells was recognized by the specific expression of α‐smooth musle actin, indicating the effect of tumor cells on the behavior of fibroblasts. Furthermore, multiple types of cell co‐culture can be demonstrated on the single device which enables to mimic the complicated microenviroment in vivo. The device is simple and easy to operate, which enables to realize real‐time observation of cell migration after external stimulus. This microfluidic device allows for the characterization of various cellular events on a single device sequentially, faciliating the better understanding of interaction between heterotypic cells in a more complex microenvironment.     

Nuclear deformation during breast cancer cell transmigration

Metastasis is the main cause of cancer mortality. During this process, cancer cells dislodge from a primary tumor, enter the circulation and form secondary tumors in distal organs. It is poorly understood how these cells manage to cross the tight syncytium of endothelial cells that lines the capillaries. Such capillary transmigration would require a drastic change in cell shape. We have therefore developed a microfluidic platform to study the transmigration of cancer cells. The device consists of an array of microchannels mimicking the confined spaces encountered. A thin glass coverslip bottom allows high resolution imaging of cell dynamics. We show that nuclear deformation is a critical and rate-limiting step for transmigration of highly metastatic human breast cancer cells. Transmigration was significantly reduced following the treatment with a protein methyltransferase inhibitor, suggesting that chromatin condensation might play an important role. Since transmigration is critical for cancer metastasis, this new platform may be useful for developing improved cancer therapies.     

Perfusion-based microfluidic device for three-dimensional dynamic primary human hepatocyte cell culture in the absence of biological or synthetic matrices or coagulants

We describe a perfusion-based microfluidic device for three-dimensional (3D) dynamic primary human hepatocyte cell culture. The microfluidic device was used to promote and maintain 3D tissue-like cellular morphology and cell-specific functionality of primary human hepatocytes by restoring membrane polarity and hepatocyte transport function in vitro without the addition of biological or synthetic matrices or coagulants. A unique feature of our dynamic cell culture device is the creation of a microenvironment, without the addition of biological or synthetic matrices or coagulants, that promotes the 3D organization of hepatocytes into cord-like structures that exhibit functional membrane polarity as evidenced by the expression of gap junctions and the formation of an extended, functionally active, bile canalicular network.     

Endothelial cell polarization and chemotaxis in a microfluidic device

The directed migration of endothelial cells is an early and critical step in angiogenesis, or new blood vessel formation. In this study, the polarization and chemotaxis of human umbilical vein endothelial cells (HUVEC) in response to quantified gradients of vascular endothelial growth factor (VEGF) were examined. To accomplish this, a microfluidic device was designed and fabricated to generate stable concentration gradients of biomolecules in a cell culture chamber while minimizing the fluid shear stress experienced by the cells. Finite element simulation of the device geometry produced excellent agreement with the observed VEGF concentration distribution, which was found to be stable across multiple hours. This device is expected to have wide applicability in the study of shear-sensitive cells such as HUVEC and non-adherent cell types as well as in the study of migration through three-dimensional matrices. HUVEC were observed to chemotax towards higher VEGF concentrations across the entire range of concentrations studied (18-32 ng mL(-1)) when the concentration gradient was 14 ng mL(-1) mm(-1). In contrast, shallow gradients (2 ng mL(-1) mm(-1)) across the same concentration range were unable to induce HUVEC chemotaxis. Furthermore, while all HUVEC exposed to elevated VEGF levels (both in steep and shallow gradients) displayed an increased number of filopodia, only chemotaxing HUVEC displayed an asymmetric distribution of filopodia, with enhanced numbers of protrusions present along the leading edge. These results suggest a two-part requirement to induce VEGF chemotaxis: the VEGF absolute concentration enhances the total number of filopodia extended while the VEGF gradient steepness induces filopodia localization, cell polarization, and subsequent directed migration.     

Patterned cell culture inside microfluidic devices

This paper describes a simple plasma-based dry etching method that enables patterned cell culture inside microfluidic devices by allowing patterning, fluidic bonding and sterilization steps to be carried out in a single step. This plasma-based dry etching method was used to pattern cell-adhesive and non-adhesive areas on the glass and polystyrene substrates. The patterned substrate was used for selective attachment and growth of human umbilical vein endothelial cells, MDA-MB-231 human breast cancer cells, NIH 3T3 mouse fibroblasts, and primary rat cortical neurons. Finally, we have successfully combined the dry-patterned substrate with a microfluidic device. Patterned primary rat neurons were maintained for up to 6 days inside the microfluidic devices and the neurons' somas and processes were confined to the cell-adhesive region. The method developed in this work offers a convenient way of micropatterning biomaterials for selective attachment of cells on the substrates, and enables culturing of patterned cells inside microfluidic devices for a number of biological research applications where cells need to be exposed to well-controlled fluidic microenvironment.     

Live cell imaging analysis of the epigenetic regulation of the human endothelial cell migration at single-cell resolution

Epigenetic regulation plays an important role in cell migration. Although many methods have been developed to measure the motility of mammalian cells, accurate quantitative assessments of the migration speed of individual cells remain a major challenge. It is difficult for conventional scratch assays to differentiate proliferation from migration during the so-called wound-healing processes because of the long experimental time required. In addition, it is also challenging to create identical conditions for evaluating cell migration by conventional methods. We developed a microfluidic device with precisely created blanks allowing for robust and reproducible cell migration inside accurately-controlled microenvironments to study the regulatory effect of the epigenetic regulator histone deacetylase 7 (HDAC7) on cell migration. Through analyzing time-lapse imaging of the cells migrating into individual blank regions, we can measure the migration speed parameter for human primary cells within a few hours, eliminating the confounding effect of cell proliferation. We also developed an automatic image analysis and a numeric model-based data fitting to set up an integrated cell migration analysis system at single-cell resolution. Using this system, we measured the motility of primary human umbilical vein endothelial cells (HUVECs) and the migration speed reduction due to the silencing of HDAC7 and various other genes. We showed that the migration behaviour of these human primary cells are clearly regulated by epigenetic mechanisms, demonstrating the great potential of this accurate and robust assay in the fields of quantitatively migration studies and high-throughput screening.     

Circular‐shaped microfluidic device to study the effect of shear stress on cellular orientation

Understanding the effects of shear stress on mammalian cells is a crucial factor for understanding a number of biological processes and diseases. Here, we show the development of a circular‐shaped microfluidic device for the facile generation of shear stress gradients. With this microfluidic device, the effect of shear stress on orientation of human umbilical vein endothelial cells was studied. This microfluidic device, which enables to control the alignment of human umbilical vein endothelial cells within a microchannel, can be a valuable tool to mimic blood vessels.     

Selenadiazole Derivatives Inhibit Angiogenesis‐Mediated Human Breast Tumor Growth by Suppressing the VEGFR2‐Mediated ERK and AKT Signaling Pathways

Selenadiazole derivatives (SeDs) have been found to show promise in chemo‐/radiotherapy applications by activating various downstream signaling pathways. However, the functional role of SeDs on angiogenesis, which is pivotal for tumor progression and metastasis, has not yet been elucidated. In the present study, we have examined the antiangiogenic activities of SeDs and elucidated their underlying mechanisms. The results showed that the as‐synthesized SeDs not only enhanced their anticancer activities against several human cancer cells but also showed more potent inhibition on human umbilical vein endothelial cells (HUVECs). The in vitro results suggested that SeDs, especially 1 a , dose‐dependently inhibited the vascular endothelial growth factor (VEGF)‐induced cell migration, invasion, and capillary‐like structure formation of HUVECs. Compound 1 a also significantly suppressed VEGF‐induced angiogenesis in a Matrigel plug assay as part of a C57/BL6 mice assay by means of down regulation of VEGF. Furthermore, we found that 1 a significantly inhibited MCF‐7 human breast tumor growth in nude mice without severe systematic cytotoxicity. Compound 1 a was more effective in inhibiting cell proliferation and induced a much more pronounced apoptosis effect in endothelial cells than MCF‐7 cells, which implies that endothelial cells might be the primary target of 1 a . Further mechanistic studies on tumor growth inhibition effects and neovessel formation suppression demonstrated that 1 a inhibited cell viability of MCF‐7 and HUVECs by induction of cell apoptosis, accompanied by poly(adenosine diphosphate ribose)polymerase (PARP) cleavage and caspase activation. Additionally, the 1 a ‐induced antiangiogenesis effect was achieved by abolishing the VEGF‐VEGFR2‐ERK/AKT (ERK=extracellular signal–regulated kinases; AKT=protein kinease B) signal axis and enhanced the apoptosis effect by triggering reactive oxygen species (ROS)‐mediated DNA damage. Taken together, these results clearly demonstrate the antiangiogenic potency of SeDs and the underlying molecular mechanisms.     

Microfluidic Device Using a Gold Pillar Array and Integrated Electrodes for On‐chip Endothelial Cell Immobilization,Direct RBC Contact,and Amperometric Detection of Nitric Oxide

We describe a microfluidic device that can be used to detect interactions between red blood cells (RBCs) and endothelial cells using a gold pillar array (created by electrodeposition) and an integrated detection electrode. Endothelial cells can release nitric oxide (NO) via stimulation by RBC‐derived ATP. These studies incorporate on‐chip endothelial cell immobilization, direct RBC contact, and detection of NO in a single microfluidic device. In order to study the RBC‐EC interactions, this work used a microfluidic device made of a PDMS chip with two adjacent channels and a polystyrene base with embedded electrodes for creating a membrane (via gold pillars) and detecting NO (at a glassy carbon electrode coated with platinum‐black and Nafion). RBCs were pharmacologically treated with treprostinil in the absence and presence of glybenclamide, and ATP release was determined as was the resultant NO release from endothelial cells. Treprostinil treatment of RBCs resulted in ATP release that stimulated endothelial cells to release on average 1.8±0.2 nM NO per endothelial cell (average±SEM, n=8). Pretreatment of RBCs with glybenclamide inhibited treprostinil‐induced ATP release and, therefore, less NO was produced by the endothelial cells (0.92±0.1 nM NO per endothelial cell, n=7). In the future, this device can be used to study interactions between many other cell types (both adherent and non‐adherent cell lines) and incorporate other detection schemes.     

T cell chemotaxis in a simple microfluidic device

This paper describes the use of a simple microfluidic device for studying T cell chemotaxis. The microfluidic device is fabricated in poly(dimethylsiloxane) (PDMS) using soft-lithography and consists of a "Y" type fluidic channel. Solutions are infused into the device by syringe pumps and generate a concentration gradient in the channel by diffusion. We show that the experimentally measured gradient profiles agree nicely with theoretical predictions and the gradient is stable in the observation region for cell migration. Using this device, we demonstrate robust chemotaxis of human T cells in response to single and competing gradients of chemokine CCL19 and CXCL12. Because of the simplicity of the device, it can flexibly control gradient generation in space and time, and would allow generation of multiple gradient conditions in a single chip for highly parallel chemotaxis experimentation. Visualization of T cell chemotaxis has previously been limited to studies in 3D matrices or under agarose assays, which do not allow precise control or variation in conditions. Acknowledging the importance of lymphocyte homing in the adaptive immune response, the ability to study T cell chemotaxis in microfluidic devices offers a new approach for investigating lymphocyte migration and chemotaxis in vitro.     

A micropillar-integrated smart microfluidic device for specific capture and sorting of cells

An integrated smart microfluidic device consisting of nickel micropillars, microvalves, and microchannels was developed for specific capture and sorting of cells. A regular hexagonal array of nickel micropillars was integrated on the bottom of a microchannel by standard photolithography, which can generate strong induced magnetic field gradients under an external magnetic field to efficiently trap superparamagnetic beads (SPMBs) in a flowing stream, forming a bed with sufficient magnetic beads as a capture zone. Fluids could be manipulated by programmed controlling the integrated air-pressure-actuated microvalves, based on which in situ bio-functionalization of SPMBs trapped in the capture zone was realized by covalent attachment of specific proteins directly to their surface on the integrated microfluidic device. In this case, only small volumes of protein solutions (62.5 nL in the capture zone; 375 nL in total volume needed to fill the device from inlet A to the intersection of outlet channels F and G) can meet the need for protein! The newly designed microfluidic device reduced greatly chemical and biological reagent consumption and simplified drastically tedious manual handling. Based on the specific interaction between wheat germ agglutinin (WGA) and N-acetylglucosamine on the cell membrane, A549 cancer cells were effectively captured and sorted on the microfluidic device. Capture efficiency ranged from 62 to 74%. The integrated microfluidic device provides a reliable technique for cell sorting.     

Activated T lymphocytes migrate toward the cathode of DC electric fields in microfluidic devices

Immune cell migration is a fundamental process that enables immunosurveillance and immune responses. Understanding the mechanism of immune cell migration is not only of importance to the biology of cells, but also has high relevance to cell trafficking mediated physiological processes and diseases such as embryogenesis, wound healing, autoimmune diseases and cancers. In addition to the well-known chemical concentration gradient based guiding mechanism (i.e. chemotaxis), recent studies have shown that lymphocytes can respond to applied physiologically relevant direct current (DC) electric fields by migrating toward the cathode of the fields (i.e. electrotaxis) in both in vitro and in vivo settings. In the present study, we employed two microfluidic devices allowing controlled application of electric fields inside the microfluidic channel for quantitative studies of lymphocyte electrotaxis in vitro at the single cell level. The first device is fabricated by soft-lithography and the second device is made in glass with integrated on-chip electrodes. Using both devices, we for the first time showed that anti-CD3/CD28 antibodies activated human blood T cells migrate to the cathode of the applied DC electric field. This finding is consistent with previous electrotaxis studies on other lymphocyte subsets suggesting electrotaxis is a novel guiding mechanism for immune cell migration. Furthermore, the characteristics of electrotaxis and chemotaxis of activated T cells in PDMS microfluidic devices are compared.     

An integrated microfluidic culture device to regulate endothelial cell differentiation from embryonic stem cells

We developed an integrated microfluidic culture device to regulate embryonic stem (ES) cell fate. The integrated microfluidic culture device consists of an air control channel and a fluidic channel with 4×4 micropillar arrays. We hypothesized that the microscale posts within the micropillar arrays would enable the control of uniform cell docking and shear stress profiles. We demonstrated that ES cells cultured for 6 days in the integrated microfluidic culture device differentiated into endothelial cells. Therefore, our integrated microfluidic culture device is a potentially powerful tool for directing ES cell fate.     

Integrated cell manipulation system--CMOS/microfluidic hybrid

Manipulation of biological cells using a CMOS/microfluidic hybrid system is demonstrated. The hybrid system starts with a custom-designed CMOS (complementary metal-oxide semiconductor) chip fabricated in a semiconductor foundry. A microfluidic channel is post-fabricated on top of the CMOS chip to provide biocompatible environments. The motion of individual biological cells that are tagged with magnetic beads is directly controlled by the CMOS chip that generates microscopic magnetic field patterns using an on-chip array of micro-electromagnets. Furthermore, the CMOS chip allows high-speed and programmable reconfiguration of the magnetic fields, substantially increasing the manipulation capability of the hybrid system. Extending from previous work that verified the concept of the hybrid system, this paper reports a set of manipulation experiments with biological cells, which further confirms the advantage of the hybrid approach. To enhance the biocompatibility of the system, the microfluidic channel is redesigned and the temperature of the device is monitored by on-chip sensors. Combining microelectronics and microfluidics, the CMOS/microfluidic hybrid system presents a new model for a cell manipulation platform in biological and biomedical applications.     

A digital microfluidic platform for primary cell culture and analysis

Digital microfluidics (DMF) is a technology that facilitates electrostatic manipulation of discrete nano- and micro-litre droplets across an array of electrodes, which provides the advantages of single sample addressability, automation, and parallelization. There has been considerable interest in recent years in using DMF for cell culture and analysis, but previous studies have used immortalized cell lines. We report here the first digital microfluidic method for primary cell culture and analysis. A new mode of "upside-down" cell culture was implemented by patterning the top plate of a device using a fluorocarbon liftoff technique. This method was useful for culturing three different primary cell types for up to one week, as well as implementing a fixation, permeabilization, and staining procedure for F-actin and nuclei. A multistep assay for monocyte adhesion to endothelial cells (ECs) was performed to evaluate functionality in DMF-cultured primary cells and to demonstrate co-culture using a DMF platform. Monocytes were observed to adhere in significantly greater numbers to ECs exposed to tumor necrosis factor (TNF)-α than those that were not, confirming that ECs cultured in this format maintain in vivo-like properties. The ability to manipulate, maintain, and assay primary cells demonstrates a useful application for DMF in studies involving precious samples of cells from small animals or human patients.