共查询到20条相似文献，搜索用时 15 毫秒
1.
Biomolecule gradients play an important role in the understanding of various biological processes. Typically, biological cells are exposed to linear and nonlinear concentration gradients and their response is studied for understanding cell growth, cell migration, and cell differentiation mechanisms. Recent studies have demonstrated the use of microfluidic devices for precise and stable concentration gradient generation. However, most of the reported devices are geometrically complex and lack dynamic controllability. In this work, a novel microfluidic gradient generator is presented which utilizes the induced charge electro-osmosis (ICEO) by introducing conducting obstacle in the microchannel. With the ICEO flow component, significant transverse convection can be generated within the microchannel, which can, in turn, be used to create nonlinear as well as asymmetric gradients. The characteristics of the developed concentration gradient are dependent on the interplay between fixed charge electro-osmotic and ICEO flows. It is shown that the proposed device can switch between linear and nonlinear gradients by just altering the applied electric field. Finally, the formation of user-defined concentration profiles (linear, convex, and concave) is demonstrated by varying the conducting obstacle size. 相似文献
2.
Sarit K. Das Seok Chung Ioannis Zervantonakis Joseph Atnafu Roger D. Kamm 《Biomicrofluidics》2008,2(3)
Studies on the effects of variations in temperature and mild temperature gradients on cells, gels, and scaffolds are important from the viewpoint of biological function. Small differences in temperature are known to elicit significant variations in cell behavior and individual protein reactivity. For the study of thermal effects and gradients in vitro, it is important to develop microfluidic platforms which are capable of controlling temperature gradients in an environment which mimics the range of physiological conditions. In the present paper, such a microfluidic thermal gradient system (μTGS) system is proposed which can create and maintain a thermal gradient throughout a cell-seeded gel matrix using the hot and cold water supply integrated in the system in the form of a countercurrent heat exchanger. It is found that a uniform temperature gradient can be created and maintained in the device even inside a high temperature and high humidity environment of an incubator. With the help of a hot and cold circuit controlled from outside the incubator the temperature gradient can be regulated. A numerical simulation of the device demonstrates the thermal feature of the chip. Cell viability and activity under a thermal gradient are examined by placing human breast cancer cells in the device. 相似文献
3.
Hui Huang Lili Jiang Shu Li Jun Deng Yan Li Jie Yao Biyuan Li Junsong Zheng 《Biomicrofluidics》2014,8(1)
Molecular gradients play a significant role in regulating biological and pathological processes. Although conventional gradient-generators have been used for studying chemotaxis and axon guidance, there are still many limitations, including the inability to maintain stable tempo-spatial gradients and the lack of the cell monitoring in a real-time manner. To overcome these shortcomings, microfluidic devices have been developed. In this study, we developed a microfluidic gradient device for regulating neuron axon guidance. A microfluidic device enables the generation of Brain-derived neurotrophic factor (BDNF) gradient profiles in a temporal and spatial manner. We test the effect of the gradient profiles on axon guidance, in the BDNF concentration gradient axon towards the high concentration gradient. This microfluidic gradient device could be used as a powerful tool for cell biology research. 相似文献
4.
High-throughput study of alpha-synuclein expression in yeast using microfluidics for control of local cellular microenvironment 总被引：1，自引：0，他引：1
Microfluidics is an emerging technology which allows the miniaturization, integration, and automation of fluid handling processes. Microfluidic systems offer low sample consumption, significantly reduced processing time, and the prospect of massive parallelization. A microfluidic platform was developed for the control of the soluble cellular microenvironment of Saccharomyces cerevisiae cells, which enabled high-throughput monitoring of the controlled expression of alpha-synuclein (aSyn), a protein involved in Parkinson's disease. Y-shaped structures were fabricated using particle desorption mass spectrometry-based soft-lithography techniques to generate biomolecular gradients along a microchannel. Cell traps integrated along the microchannel allowed the positioning and monitoring of cells in precise locations, where different, well-controlled chemical environments were established. S. cerevisiae cells genetically engineered to encode the fusion protein aSyn-GFP (green fluorescent protein) under the control of GAL1, a galactose inducible promoter, were loaded in the microfluidic structure. A galactose concentration gradient was established in the channel and a time-dependent aSyn-GFP expression was obtained as a function of the positioning of cells along the galactose gradient. Our results demonstrate the applicability of this microfluidic platform to the spatiotemporal control of cellular microenvironment and open a range of possibilities for the study of cellular processes based on single-cell analysis. 相似文献
5.
Yu-Chiu Kao Meng-Hua Hsieh Chung-Chun Liu Huei-Jyuan Pan Wei-Yu Liao Ji-Yen Cheng Po-Ling Kuo Chau-Hwang Lee 《Biomicrofluidics》2014,8(2)
We employed direct-current electric fields (dcEFs) to modulate the chemotaxis of lung cancer cells in a microfluidic cell culture device that incorporates both stable concentration gradients and dcEFs. We found that the chemotaxis induced by a 0.5 μM/mm concentration gradient of epidermal growth factor can be nearly compensated by a 360 mV/mm dcEF. When the effect of chemical stimulation was balanced by the electrical drive, the cells migrated randomly, and the path lengths were largely reduced. We also demonstrated electrically modulated chemotaxis of two types of lung cancer cells with opposite directions of electrotaxis in this device. 相似文献
6.
The accurate viscosity measurement of complex fluids is essential for characterizing fluidic behaviors in blood vessels and in microfluidic channels of lab-on-a-chip devices. A microfluidic platform that accurately identifies biophysical properties of blood can be used as a promising tool for the early detections of cardiovascular and microcirculation diseases. In this study, a flow-switching phenomenon depending on hydrodynamic balancing in a microfluidic channel was adopted to conduct viscosity measurement of complex fluids with label-free operation. A microfluidic device for demonstrating this proposed method was designed to have two inlets for supplying the test and reference fluids, two side channels in parallel, and a junction channel connected to the midpoint of the two side channels. According to this proposed method, viscosities of various fluids with different phases (aqueous, oil, and blood) in relation to that of reference fluid were accurately determined by measuring the switching flow-rate ratio between the test and reference fluids, when a reverse flow of the test or reference fluid occurs in the junction channel. An analytical viscosity formula was derived to measure the viscosity of a test fluid in relation to that of the corresponding reference fluid using a discrete circuit model for the microfluidic device. The experimental analysis for evaluating the effects of various parameters on the performance of the proposed method revealed that the fluidic resistance ratio (RJL/RL, fluidic resistance in the junction channel (RJL) to fluidic resistance in the side channel (RL)) strongly affects the measurement accuracy. The microfluidic device with smaller RJL/RL values is helpful to measure accurately the viscosity of the test fluid. The proposed method accurately measured the viscosities of various fluids, including single-phase (Glycerin and plasma) and oil-water phase (oil vs. deionized water) fluids, compared with conventional methods. The proposed method was also successfully applied to measure viscosities of blood with varying hematocrits, chemically fixed RBCS, and channel sizes. Based on these experimental results, the proposed method can be effectively used to measure the viscosities of various fluids easily, without any fluorescent labeling and tedious calibration procedures. 相似文献
7.
Precisely controlling the spatial distribution of biomolecules on biomaterial surface is important for directing cellular activities in the controlled cell microenvironment. This paper describes a polydimethylsiloxane (PDMS) gradient-generating microfluidic device to immobilize the gradient of cellular adhesive Arg-Gly-Asp (RGD) peptide on poly (ethylene glycol) (PEG) hydrogel. Hydrogels are formed by exposing the mixture of PEG diacrylate (PEGDA), acryloyl-PEG-RGD, and photo-initiator with ultraviolet light. The microfluidic chip was simulated by a fluid dynamic model for the biomolecule diffusion process and gradient generation. PEG hydrogel covalently immobilized with RGD peptide gradient was fabricated in this microfluidic device by photo-polymerization. Bone marrow derived rat mesenchymal stem cells (MSCs) were then cultured on the surface of RGD gradient PEG hydrogel. Cell adhesion of rat MSCs on PEG hydrogel with various RGD gradients were then qualitatively and quantitatively analyzed by immunostaining method. MSCs cultured on PEG hydrogel surface with RGD gradient showed a grated fashion for cell adhesion and spreading that was proportional to RGD concentration. It was also found that 0.107–0.143 mM was the critical RGD concentration range for MSCs maximum adhesion on PEG hydrogel. 相似文献
8.
This work describes the development of a prototypic microfluidic platform for the generation of stepwise concentration gradients of drugs. A sensitive apoptotic analysis method is integrated into this microfluidic system for studying apoptosis of HeLa cells under the influence of anticancer drug, etoposide, with various concentrations in parallel; it measures the yellow fluorescent protein∕cyan fluorescent protein fluorescence resonance energy transfer (FRET) signal that responds to the activation of caspase-3, an indicator of cell apoptosis. Sets of microfluidic valves on the chip generate stepwise concentration gradient of etoposide in various cell-culture microchambers. The FRET signals from multiple chambers are simultaneously monitored under a fluorescent microscope for long-time observation and the on-chip results are compared with those from 96-well plate study and the methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. The microfluidic platform shows several advantages including high-throughput capacity, low drug consumption, and high sensitivity. 相似文献
9.
In this report, we demonstrate a simple and low cost method that can be reproducibly used for fabrication of microfluidic devices in nitrocellulose. The fluidic patterns are created via a laser-based direct-write technique that induces polymerisation of a photo-polymer previously impregnated in the nitrocellulose. The resulting structures form hydrophobic barriers that extend through the thickness of the nitrocellulose and define an interconnected hydrophilic fluidic-flow pattern. Our experimental results show that using this method it is possible to achieve microfluidic channels with lateral dimensions of ∼100 μm using hydrophobic barriers that form the channel walls with dimensions of ∼60 μm; both of these values are considerably smaller than those that can be achieved with other current techniques used in the fabrication of nitrocellulose-based fluidic devices. A simple grid patterned nitrocellulose device was then used for the detection of C-reactive protein via a sandwich enzyme-linked immunosorbent assay, which served as a useful proof-of-principle experiment. 相似文献
10.
Circulating tumor cells (CTCs) are the principal vehicle for the spread of non-hematologic cancer disease from a primary tumor, involving extravasation of CTCs across blood vessel walls, to form secondary tumors in remote organs. Herein, a polydimethylsiloxane-based microfluidic system is developed and characterized for in vitro systematic studies of organ-specific extravasation of CTCs. The system recapitulates the two major aspects of the in vivo extravasation microenvironment: local signaling chemokine gradients in a vessel with an endothelial monolayer. The parameters controlling the locally stable chemokine gradients, flow rate, and initial chemokine concentration are investigated experimentally and numerically. The microchannel surface treatment effect on the confluency and adhesion of the endothelial monolayer under applied shear flow has also been characterized experimentally. Further, the conditions for driving a suspension of CTCs through the microfluidic system are discussed while simultaneously maintaining both the local chemokine gradients and the confluent endothelial monolayer. Finally, the microfluidic system is utilized to demonstrate extravasation of MDA-MB-231 cancer cells in the presence of CXCL12 chemokine gradients. Consistent with the hypothesis of organ-specific extravasation, control experiments are presented to substantiate the observation that the MDA-MB-231 cell migration is attributed to chemotaxis rather than a random process. 相似文献
11.
Jae-Woo Choi Seyyed Mohammad Hosseini Hashemi David Erickson Demetri Psaltis 《Biomicrofluidics》2014,8(4)
We present a method to perform sample concentration within a lab-on-a-chip using a microfluidic structure which controls the liquid-gas interface through a micropillar array fabricated in polydimethylsiloxane between microfluidic channels. The microstructure confines the liquid flow and a thermal gradient is used to drive evaporation at the liquid-gas-interface. The evaporation occurs in-plane to the microfluidic device, allowing for precise control of the ambient environment. This method is demonstrated with a sample containing 1 μm, 100 nm fluorescent beads and SYTO-9 labelled Escherichia coli bacteria. Over 100 s, the fluorescent beads and bacteria are concentrated by a factor of 10. 相似文献
12.
This paper presents a continuous flow microfluidic device for the separation of DNA from blood using magnetophoresis for biological applications and analysis. This microfluidic bio-separation device has several benefits, including decreased sample handling, smaller sample and reagent volumes, faster isolation time, and decreased cost to perform DNA isolation. One of the key features of this device is the use of short-range magnetic field gradients, generated by a micro-patterned nickel array on the bottom surface of the separation channel. In addition, the device utilizes an array of oppositely oriented, external permanent magnets to produce strong long-range field gradients at the interfaces between magnets, further increasing the effectiveness of the device. A comprehensive simulation is performed using COMSOL Multiphysics to study the effect of various parameters on the magnetic flux within the separation channel. Additionally, a microfluidic device is designed, fabricated, and tested to isolate DNA from blood. The results show that the device has the capability of separating DNA from a blood sample with a purity of 1.8 or higher, a yield of up to 33 μg of polymerase chain reaction ready DNA per milliliter of blood, and a volumetric throughput of up to 50 ml/h. 相似文献
13.
In this paper, we develop a microfluidic device capable of generating nitric oxide (NO) gradients for cell culture using spatially controlled chemical reactions. NO plays an essential role in various biological activities, including nervous, immune, and cardiovascular systems. The device developed in this paper can control NO gradients without utilizing expensive and hazardous high purity NO gas sources or direct addition of NO donors. Consequently, the device provides an efficient, cost-effective, robust, and stable platform to generate NO gradients for cell culture studies. In the experiments, NO gradients are first characterized using a NO-sensitive fluorescence dye, and cell experiments using aortic smooth muscle cells are conducted. The results demonstrate that the device can alter the intracellular NO concentrations and further affect the Ca2+ concentration oscillation for the cells. The device developed in this paper provides a powerful platform for researchers better study the biological roles of NO and its spatial distribution using in vitro cell models with minimal instrumentation. 相似文献
14.
Microfluidic devices have been established as useful platforms for cell culture for a broad range of applications, but challenges associated with controlling gradients of oxygen and other soluble factors and hemodynamic shear forces in small, confined channels have emerged. For instance, simple microfluidic constructs comprising a single cell culture compartment in a dynamic flow condition must handle tradeoffs between sustaining oxygen delivery and limiting hemodynamic shear forces imparted to the cells. These tradeoffs present significant difficulties in the culture of mesenchymal stem cells (MSCs), where shear is known to regulate signaling, proliferation, and expression. Several approaches designed to shield cells in microfluidic devices from excessive shear while maintaining sufficient oxygen concentrations and transport have been reported. Here we present the relationship between oxygen transport and shear in a "membrane bilayer" microfluidic device, in which soluble factors are delivered to a cell population by means of flow through a proximate channel separated from the culture channel by a membrane. We present an analytical model that describes the characteristics of this device and its ability to independently modulate oxygen delivery and hemodynamic shear imparted to the cultured cells. This bilayer configuration provides a more uniform oxygen concentration profile that is possible in a single-channel system, and it enables independent tuning of oxygen transport and shear parameters to meet requirements for MSCs and other cells known to be sensitive to hemodynamic shear stresses. 相似文献
15.
Three-dimensional microfluidics holds great promise for large-scale integration of versatile, digitalized, and multitasking fluidic manipulations for biological and clinical applications. Successful translation of microfluidic toolsets to these purposes faces persistent technical challenges, such as reliable system-level packaging, device assembly and alignment, and world-to-chip interface. In this paper, we extended our previously established fit-to-flow (F2F) world-to-chip interconnection scheme to a complete system-level assembly strategy that addresses the three-dimensional microfluidic integration on demand. The modular F2F assembly consists of an interfacial chip, pluggable alignment modules, and multiple monolithic layers of microfluidic channels, through which convoluted three-dimensional microfluidic networks can be easily assembled and readily sealed with the capability of reconfigurable fluid flow. The monolithic laser-micromachining process simplifies and standardizes the fabrication of single-layer pluggable polymeric modules, which can be mass-produced as the renowned Lego® building blocks. In addition, interlocking features are implemented between the plug-and-play microfluidic chips and the complementary alignment modules through the F2F assembly, resulting in facile and secure alignment with average misalignment of 45 μm. Importantly, the 3D multilayer microfluidic assembly has a comparable sealing performance as the conventional single-layer devices, providing an average leakage pressure of 38.47 kPa. The modular reconfigurability of the system-level reversible packaging concept has been demonstrated by re-routing microfluidic flows through interchangeable modular microchannel layers. 相似文献
16.
A sequential and high-throughput single-cell manipulation system for a large volume of cells was developed and the successive manipulation for single cell involving single-cell isolation, individual labeling, and individual rupture was realized in a microhydrodynamic flow channel fabricated by using two-dimensional simple flow channels. This microfluidic system consisted of the successive single-cell handlings of single-cell isolation from a large number of cells in cell suspension, labeling each isolated single cell and the lysate extraction from each labeled single cell. This microfluidic system was composed of main channels, cell-trapping pockets, drain channels, and single-cell content collection channels which were fabricated by polydimethylsiloxane. We demonstrated two kinds of prototypes for sequential single-cell manipulations, one was equipped with 16 single-cell isolation pockets in microchannel and the other was constructed of 512 single-cell isolation pockets. In this study, we demonstrated high-throughput and high-volume single-cell isolation with 512 pocket type device. The total number of isolated single cells in each isolation pocket from the cell suspension at a time was 426 for the cell line of African green monkey kidney, COS-1, and 360 for the rat primary brown preadipocytes, BAT. All isolated cells were stained with fluorescence dye injected into the same microchannel successfully. In addition, the extraction and collection of the cell contents was demonstrated using isolated stained COS-1 cells. The cell contents extracted from each captured cell were individually collected within each collection channel by local hydrodynamic flow. The sequential trapping, labeling, and content extraction with 512 pocket type devices realized high-throughput single-cell manipulations for innovative single-cell handling, feasible staining, and accurate cell rupture. 相似文献
17.
We present a microfluidic parallel circuit that directly compares the test channel of an unknown hydraulic resistance with the reference channel with a known resistance, thereby measuring the unknown resistance without any measurement setup, such as standard pressure gauges. Many of microfluidic applications require the precise transport of fluid along a channel network with complex patterns. Therefore, it is important to accurately characterize and measure the hydraulic resistance of each channel segment, and determines whether the device principle works well. However, there is no fluidic device that includes features, such as the ability to diagnose microfluidic problems by measuring the hydraulic resistance of a microfluidic component in microscales. To address the above need, we demonstrate a simple strategy to measure an unknown hydraulic resistance, by characterizing the hydraulic resistance of microchannels with different widths and defining an equivalent linear channel of a microchannel with repeated patterns of a sudden contraction and expansion. 相似文献
18.
Matthew J. Kennedy Harold D. Ladouceur Tiffany Moeller Dickson Kirui Carl A. Batt 《Biomicrofluidics》2012,6(4)
The present work describes the operation and simulation of a microfluidic laminar-flow mixer. Diffusive mixing takes place between a core solution containing lipids in ethanol and a sheath solution containing aqueous buffer, leading to self assembly of liposomes. Present device architecture hydrodynamically focuses the lipid solution into a cylindrical core positioned at the center of a microfluidic channel of 125 × 125-μm2 cross-section. Use of the device produces liposomes in the size range of 100–300 nm, with larger liposomes forming at greater ionic strength in the sheath solution and at lower lipid concentration in the core solution. Finite element simulations compute the concentration distributions of solutes at axial distances of greater than 100 channel widths. These simulations reduce computation time and enable computation at long axial distances by utilizing long hexahedral elements in the axial flow region and fine tetrahedral elements in the hydrodynamic focusing region. Present meshing technique is generally useful for simulation of long microfluidic channels and is fully implementable using comsol Multiphysics. Confocal microscopy provides experimental validation of the simulations using fluorescent solutions containing fluorescein or enhanced green fluorescent protein. 相似文献
19.
Control of the 3D microenvironment for cultured cells is essential for understanding the complex relationships that biomolecular concentration gradients have on cellular growth, regeneration, and differentiation. This paper reports a microfluidic device for delivering gradients of soluble molecules to cells in an open reservoir without exposing the cells to flow. The cells are cultured on a polyester membrane that shields them from the flow that delivers the gradient. A novel "lid" design is implemented which prevents leakage from around the membrane without requiring sealing agents or adhesives. Once layers are molded, device fabrication can be performed within minutes while at room temperature. Surface gradients were characterized with epifluorescence microscopy; image analysis verified that sharp gradients (～33 μm wide) can be reproducibly generated. We show that heterogeneous laminar flow patterns of Orange and Green Cell Tracker (CT) applied beneath the membrane can be localized to cells cultured on the other side; concentration profile scans show the extent of CT diffusion parallel to the membrane's surface to be 10-20 μm. Our device is ideal for conventional cell culture because the cell culture surface is readily accessible to physical manipulation (e.g., micropipette access), the cell culture medium is in direct contact with the incubator atmosphere (i.e., no special protocols for ensuring proper equilibration of gas concentrations are required), and the cells are not subjected to flow-induced shear forces, which are advantageous attributes not commonly found in closed-channel microfluidic designs. 相似文献
20.
Blood viscosity has been considered as one of important biophysical parameters for effectively monitoring variations in physiological and pathological conditions of circulatory disorders. Standard previous methods make it difficult to evaluate variations of blood viscosity under cardiopulmonary bypass procedures or hemodialysis. In this study, we proposed a unique microfluidic device for simultaneously measuring viscosity and flow rate of whole blood circulating in a complex fluidic network including a rat, a reservoir, a pinch valve, and a peristaltic pump. To demonstrate the proposed method, a twin-shaped microfluidic device, which is composed of two half-circular chambers, two side channels with multiple indicating channels, and one bridge channel, was carefully designed. Based on the microfluidic device, three sequential flow controls were applied to identify viscosity and flow rate of blood, with label-free and sensorless detection. The half-circular chamber was employed to achieve mechanical membrane compliance for flow stabilization in the microfluidic device. To quantify the effect of flow stabilization on flow fluctuations, a formula of pulsation index (PI) was analytically derived using a discrete fluidic circuit model. Using the PI formula, the time constant contributed by the half-circular chamber is estimated to be 8 s. Furthermore, flow fluctuations resulting from the peristaltic pumps are completely removed, especially under periodic flow conditions within short periods (T < 10 s). For performance demonstrations, the proposed method was applied to evaluate blood viscosity with respect to varying flow rate conditions [(a) known blood flow rate via a syringe pump, (b) unknown blood flow rate via a peristaltic pump]. As a result, the flow rate and viscosity of blood can be simultaneously measured with satisfactory accuracy. In addition, the proposed method was successfully applied to identify the viscosity of rat blood, which circulates in a complex fluidic network. These observations confirm that the proposed method can be used for simultaneous measurement of viscosity and flow rate of whole blood circulating in the complex fluid network, with sensorless and label-free detection. Furthermore, the proposed method will be used in evaluating variations in the viscosity of human blood during cardiopulmonary bypass procedures or hemodialysis. 相似文献