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.     

基于微流控芯片的乳腺癌细胞微环境酸化检测

建立了基于微流控芯片的乳腺癌微环境酸化模型和动态检测微环境酸化情况的分析方法。设计了一种多层复合式微流控芯片,将乳腺癌细胞悬液引入含有水凝胶前体的芯片培养室后,在硝酸纤维素薄膜上固化形成3D培养支架。芯片通道连续灌流模拟血流供应,并将非电化学的pH检测器引入芯片,通过图像分析得到实时的pH变化。通过观察癌细胞的存活率、增殖率、乳酸水平及pH值,分析微环境的酸化情况,同时与正常细胞进行比较。结果表明,连续灌流培养7 d,乳腺癌细胞的存活率保持在90%以上;随着培养天数的增加,芯片上癌细胞微环境的pH值逐渐降低,且灌流速度越低,pH值下降越明显,而正常细胞微环境的pH值无明显变化。基于微流控芯片的微环境酸化检测平台可实时动态检测微环境的pH值,有望成为相关肿瘤研究的有力工具。     

High‐Throughput Isolation of Cell Protrusions with Single‐Cell Precision for Profiling Subcellular Gene Expression

Invading cancer cells extend cell protrusions, which guide cancer‐cell migration and invasion, eventually leading to metastasis. The formation and activity of cell protrusions involve the localization of molecules and organelles at the cell front; however, it is challenging to precisely isolate these subcellular structures at the single‐cell level for molecular analysis. Here, we describe a newly developed microfluidic platform capable of high‐throughput isolation of cell protrusions at single‐cell precision for profiling subcellular gene expression. Using this microfluidic platform, we demonstrate the efficient generation of uniform cell‐protrusion arrays (more than 5000 cells with protrusions) for a series of cell types. We show precise isolation of cell protrusions with high purity at single‐cell precision for subsequent RNA‐Seq analysis, which was further validated by RT‐qPCR and RNA FISH. Our highly controlled protrusion isolation method opens a new avenue for the study of subcellular functional mechanisms and signaling pathways in metastasis.     

Determination of single cell surface protein expression using a tagless microfluidic method

We describe a method to detect the expression of a surface protein in single cells without prior labeling or manipulation using a microfluidic device. When the protein is expressed on a cell surface, it undergoes transient bond formation with an immobilized ligand as the cell is pumped through a microfluidic channel, resulting in a specific decrease in the cell's velocity. We were able to detect the expression of interleukin 13 receptor alpha 2 (IL13Rα2) differentially expressed on LM2 cells, a subline of MDA-MB-231 human breast cancer cells with a unique lung metastatic capability. The detection of cells with high expression of the protein was near 100% sensitive and 100% specific. We also provided proof of principle of multiplexing by tracking the same cell over two, differentially-coated patches. The method is non-destructive and cells can be collected for reanalysis. The system can identify positive cells in a cell mixture. This method will have a potential impact in analyzing cancer cells when only a few are available, such as the case with needle aspirates and when labeling and manipulation result in cell loss.     

Nanoporous micro-element arrays for particle interception in microfluidic cell separation

The ability to control cell-surface interactions in order to achieve binding of specific cell types is a major challenge for microfluidic immunoaffinity cell capture systems. In the majority of existing systems, the functionalized capture surface is constructed of solid materials, where flow stagnation at the solid-liquid interface is detrimental to the convection of cells to the surface. We study the use of ultra-high porosity (99%) nanoporous micro-posts in microfluidic channels for enhancing interception efficiency of particles in flow. We show using both modelling and experiment that nanoporous posts improve particle interception compared to solid posts through two distinct mechanisms: the increase of direct interception, and the reduction of near-surface hydrodynamic resistance. We provide initial validation that the improvement of interception efficiency also results in an increase in capture efficiency when comparing nanoporous vertically aligned carbon nanotube (VACNT) post arrays with solid PDMS post arrays of the same geometry. Using both bacteria (～1 μm) and cancer cell lines (～15 μm) as model systems, we found capture efficiency increases by 6-fold and 4-fold respectively. The combined model and experimental platform presents a new generation of nanoporous microfluidic devices for cell isolation.     

A microfluidic system to study the cytotoxic effect of drugs: the combined effect of celecoxib and 5-fluorouracil on normal and cancer cells

We have investigated the response of normal and cancer cells to exposure a combination of celecoxib (Celbx) and 5-fluorouracil (5-FU) using a lab-on-a-chip microfluidic device. Specifically, we have tested the cytotoxic effect of Celbx on normal mouse embryo cells (Balb/c 3T3) and human lung carcinoma cells (A549). The single drugs or their combinations were adjusted to five different concentrations using a concentration gradient generator (CGG) in a single step. The results suggest that Celbx can enhanced the anticancer activity of 5-FU by stronger inhibition of cancer cell growth. We also show that the A549 cancer cells are more sensitive to Celbx than the Balb/c 3T3 normal cells. The results obtained with the microfluidic system were compared to those obtained with a macroscale in vitro cell culture method. In our opinion, the microfluidic system represents a unique approach for an evaluation of cellular response to multidrug exposure that also is more simple than respective microwell plate assays.

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.     

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.     

A programmable microfluidic cell array for combinatorial drug screening

We describe the development of a fully automatic and programmable microfluidic cell culture array that integrates on-chip generation of drug concentrations and pair-wise combinations with parallel culture of cells for drug candidate screening applications. The device has 64 individually addressable cell culture chambers in which cells can be cultured and exposed either sequentially or simultaneously to 64 pair-wise concentration combinations of two drugs. For sequential exposure, a simple microfluidic diffusive mixer is used to generate different concentrations of drugs from two inputs. For generation of 64 pair-wise combinations from two drug inputs, a novel time dependent variable concentration scheme is used in conjunction with the simple diffusive mixer to generate the desired combinations without the need for complex multi-layer structures or continuous medium perfusion. The generation of drug combinations and exposure to specific cell culture chambers are controlled using a LabVIEW interface capable of automatically running a multi-day drug screening experiment. Our cell array does not require continuous perfusion for keeping cells exposed to concentration gradients, minimizing the amount of drug used per experiment, and cells cultured in the chamber are not exposed to significant shear stress continuously. The utility of this platform is demonstrated for inducing loss of viability of PC3 prostate cancer cells using combinations of either doxorubicin or mitoxantrone with TRAIL (TNF-alpha Related Apoptosis Inducing Ligand) either in a sequential or simultaneous format. Our results demonstrate that the device can capture the synergy between different sensitizer drugs and TRAIL and demonstrate the potential of the microfluidic cell array for screening and optimizing combinatorial drug treatments for cancer therapy.     

Continuous sorting of magnetic cells via on-chip free-flow magnetophoresis

The ability to separate living cells is an essential aspect of cell research. Magnetic cell separation methods are among some of the most efficient methods for bulk cell separation. With the development of microfluidic platforms within the biotechnology sector, the design of miniaturised magnetic cell sorters is desirable. Here, we report the continuous sorting of cells loaded with magnetic nanoparticles in a microfluidic magnetic separation device. Cells were passed through a microfluidic chamber and were deflected from the direction of flow by means of a magnetic field. Two types of cells were studied, mouse macrophages and human ovarian cancer cells (HeLa cells). The deflection was dependent on the magnetic moment and size of the cells as well as on the applied flow rate. The experimentally observed deflection matched well with calculations. Furthermore, the separation of magnetic and non-magnetic cells was demonstrated using the same microfluidic device.     

Label-free, microfluidic separation and enrichment of human breast cancer cells by adhesion difference

A label-free microfluidic method for separation and enrichment of human breast cancer cells is presented using cell adhesion as a physical marker. To maximize the adhesion difference between normal epithelial and cancer cells, flat or nanostructured polymer surfaces (400 nm pillars, 400 nm perpendicular, or 400 nm parallel lines) were constructed on the bottom of polydimethylsiloxane (PDMS) microfluidic channels in a parallel fashion using a UV-assisted capillary moulding technique. The adhesion of human breast epithelial cells (MCF10A) and cancer cells (MCF7) on each channel was independently measured based on detachment assays where the adherent cells were counted with increasing flow rate after a pre-culture for a period of time (e.g., one, two, and four hours). It was found that MCF10A cells showed higher adhesion than MCF7 cells regardless of culture time and surface nanotopography at all flow rates, resulting in label-free separation and enrichment of cancer cells. For the cell types used in our study, an optimum separation was found for 2 hours pre-culture on the 400 nm perpendicular line pattern followed by flow-induced detachment at a flow rate of 200 microl min(-1). The fraction of MCF7 cells was increased from 0.36 +/- 0.04 to 0.83 +/- 0.04 under these optimized conditions.     

Microfluidic techniques for tumor cell detection

Cancer metastasis is the main cause of cancer‐related death. Early detection of tumor cell in peripheral blood is of great significant to early diagnosis and effective treatment of cancer. Over the past two decades, microfluidic technologies have been demonstrated to have great potential for isolating and detecting tumor cell from blood. The present paper reviews microfluidic techniques for tumor cell detection based on various physical principles. The specific methods are categorized into active and passive methods depending on whether extra force field is applied. Working principles of the two methods are explained in detail, including microfluidics combined with optical tweezer, electric field, magnetic field, acoustophoresis, and without extra fields for tumor cell detection. Typical experiments and the results are reviewed. Based on these, research characteristics of the two methods are analyzed.     

基于双向浓度梯度的微流控芯片系统对 肿瘤细胞侵袭能力的多重分析

利用微流控芯片易于模拟体内生理环境、 流体控制精确及易于集成等优势, 将基于扩散原理的浓度梯度形成结构与经典的圣诞树形浓度梯度发生器相集成, 建立了在垂直和水平方向上形成连续、 双向浓度梯度的微流控芯片系统, 采用该系统对不同类型细胞(HEK-293, MCF-7, SGC-7901)的侵袭力进行了定量分析; 通过在垂直方向上施加血清浓度梯度, 在水平方向上施加抗肿瘤药物十字孢碱浓度梯度, 分析了在连续药物浓度作用下的人胃癌SGC-7901细胞侵袭能力被抑制的情况, 同时观察并定量评价了伴随细胞侵袭力变化过程中细胞增殖能力受抑制的情况. 研究结果表明, 该系统可形成稳定的双向物质浓度梯度; 在血清浓度梯度存在情况下, 伴随十字孢碱浓度梯度的升高, 肿瘤细胞侵袭(P<0.0001)和增殖能力(P<0.001)均呈现浓度依赖性的连续降低. 建立的双向浓度梯度微流控芯片系统可用于评价复杂环境对细胞的多重影响, 也为研究细胞间相互作用、 多种药物联用及药物筛选等提供了良好的研究平台.     

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.     

Microfluidic depletion of endothelial cells, smooth muscle cells, and fibroblasts from heterogeneous suspensions

Interactions between ligands and cell surface receptors can be exploited to design adhesion-based microfluidic cell separation systems. When ligands are immobilized on the microfluidic channel surfaces, the resulting cell capture devices offer the typical advantages of small sample volumes and low cost associated with microfluidic systems, with the added benefit of not requiring complex fabrication schemes or extensive operational infrastructure. Cell-ligand interactions can range from highly specific to highly non-specific. This paper describes the design of an adhesion-based microfluidic separation system that takes advantage of both types of interactions. A 3-stage system of microfluidic devices coated with the tetrapeptides arg-glu-asp-val (REDV), val-ala-pro-gly (VAPG), and arg-gly-asp-ser (RGDS) is utilized to deplete a heterogeneous suspension containing endothelial cells, smooth muscle cells, and fibroblasts. The ligand-coated channels together with a large surface area allow effective depletion of all three cell types in a stagewise manner.     

Analysis of the paracrine loop between cancer cells and fibroblasts using a microfluidic chip

We use a microfluidic cell culture chip equipped with pneumatic microvalves to analyze the paracrine loop between lung cancer cells and fibroblasts. In order to assess the cellular responses in the paracrine loop, we measure the migration speeds of cancer cells and the aspect ratios of fibroblasts which reflect the phenotype of myofibroblasts. With well-controlled interaction sequences between these two types of cells, we verify that the cytokines from cancer cells effectively stimulate the fibroblasts into myofibroblasts. The cytokines from myofibroblasts, rather than fibroblasts, increase the migration speeds of cancer cells. We confirm that the transforming growth factor-β1 (TGF-β1) is involved in the interaction between cancer cells and fibroblasts, and we also interrupt this paracrine loop in the cell culture chip by inhibiting the TGF-β1 receptors on fibroblasts.     

Inflammatory mimetic microfluidic chip by immobilization of cell adhesion molecules for T cell adhesion

Leukocyte adhesion to adhesion molecules on endothelial cells is important in immune function, cancer metastasis and inflammation. This cell-cell binding is mediated via cell adhesion molecules such as E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) found on endothelial cells. Because these adhesion molecules on endothelial cells vary significantly across several disease conditions such as autoimmune diseases, inflammation or cancer metastasis, investigations of therapeutic agents that down-regulate leukocyte-endothelial interactions have been based on in vitro models using endothelial cell lines. Here we report a new model, an inflammatory mimetic microfluidic chip, which emulates leukocyte binding to cell adhesion molecules (CAM) by controlling the types and ratio of adhesion molecules. In our model, E-selectin was essential for the synergic binding of Jurkat T cells. Immunosuppressive drugs, such as tacrolimus (FK506) and cyclosporine A (CsA), were used to inhibit T cell interactions under the physiologic model of T cell migration at a ratio of 5?:?4.3?:?3.9 (E-selectin?:?ICAM-1?:?VCAM-1). Our results support the potential usefulness of the inflammatory mimetic microfluidic chip as a T cell adhesion assay tool with modified adhesion molecules for applications such as immunosuppressive drug screening. The inflammatory mimetic microfluidic chip can also be used as a biosensor in clinical diagnostics, drug efficacy tests and high throughput drug screening due to the dynamic monitoring capability of the microfluidic chip.     

Dual‐micropillar‐based microfluidic platform for single embryonic stem cell‐derived neuronal differentiation

We developed the dual‐micropillar‐based microfluidic platform to direct embryonic stem (ES) cell fate. 4 × 4 dual‐micropillar‐based microfluidic platform consisted of 16 circular‐shaped outer micropillars and 8 saddle‐shaped inner micropillars in which single ES cells were cultured. We hypothesized that dual‐micropillar arrays would play an important role in controlling the shear stress and cell docking. Circular‐shaped outer micropillars minimized the shear stress, whereas saddle‐shaped inner micropillars allowed for docking of individual ES cells. We observed the effect of saddle‐shaped inner micropillars on cell docking in response to hydrodynamic resistance. We also demonstrated that ES cells cultured for 6 days within the dual‐micropillar‐based microfluidic platform differentiated into neural‐like cells. Therefore, this dual‐micropillar‐based microfluidic platform could be a potentially powerful method for screening of lineage commitments of single ES cells.     

Microbioassay system for an anti-cancer agent test using animal cells on a microfluidic gradient mixer.

We developed a novel microbioassay system equipped with a gradient mixer of two solutions, and we applied the microfluidic system to an anti-cancer agent test using living animal cells on a microchip. A microchannel for the gradient mixing of two solutions and eight other microchannels for cell assay were fabricated on a poly(dimethylsiloxane) substrate using a soft-lithography method. The functions necessary for this bioassay, i.e., cell culturing, chemical stimulation, cell staining, and fluorescence determination, were integrated into the microfluidic chip. Eight gradient concentrations of the fluorescein solution, ranging from 1 to 98 microg/ml, were archived at 0.1 microl/min on a microchip. A stomach cancer cell line was cultured, and a cell viability assay was conducted using 5-Fluorouracil as an anti-cancer agent on the microchip. Cell viability changed according to the estimated concentration of the agent solution. With the microbioassay system, an anti-cancer agent test was conducted using living cells simultaneously in eight individual channels with the gradient concentration of the agent on a microchip.