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Hydrodynamic guiding for addressing subsets of immobilized cells and molecules in microfluidic systems.

Brevig T, Krühne U, Kahn RA, Ahl T, Beyer M, Pedersen LH - BMC Biotechnol. (2003)

Bottom Line: The use of hydrodynamic guiding made multiple and dynamic experimental conditions on a small surface area possible.The ability to change the direction of flow and produce two-dimensional grids can increase the number of reactions per surface area even further.The described microfluidic system is widely applicable, and can take advantage of surfaces produced by current and future techniques for patterning in the micro- and nanometer scale.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Molecular Characterization, Biotechnological Institute, Kogle Allé 2, DK-2970 Hørsholm, Denmark. tbr@bioteknologisk.dk

ABSTRACT

Background: The interest in microfluidics and surface patterning is increasing as the use of these technologies in diverse biomedical applications is substantiated. Controlled molecular and cellular surface patterning is a costly and time-consuming process. Methods for keeping multiple separate experimental conditions on a patterned area are, therefore, needed to amplify the amount of biological information that can be retrieved from a patterned surface area. We describe, in three examples of biomedical applications, how this can be achieved in an open microfluidic system, by hydrodynamically guiding sample fluid over biological molecules and living cells immobilized on a surface.

Results: A microfluidic format of a standard assay for cell-membrane integrity showed a fast and dose-dependent toxicity of saponin on mammalian cells. A model of the interactions of human mononuclear leukocytes and endothelial cells was established. By contrast to static adhesion assays, cell-cell adhesion in this dynamic model depended on cytokine-mediated activation of both endothelial and blood cells. The microfluidic system allowed the use of unprocessed blood as sample material, and a specific and fast immunoassay for measuring the concentration of C-reactive protein in whole blood was demonstrated.

Conclusion: The use of hydrodynamic guiding made multiple and dynamic experimental conditions on a small surface area possible. The ability to change the direction of flow and produce two-dimensional grids can increase the number of reactions per surface area even further. The described microfluidic system is widely applicable, and can take advantage of surfaces produced by current and future techniques for patterning in the micro- and nanometer scale.

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The microfluidic system. (A): The reusable microfluidic chip and a slide with immobilized biological material are inserted in the docking station. When closed, the docking station provides the mechanical force for sealing of the flow chamber between the chip and the slide. The loaded docking station is placed on the stage of a microscope, and the capillaries from the microchip are connected to a liquid-controlling unit (not shown). (B): Inside the flow chamber, lanes of the immobilized biological material are sequentially exposed to sample. Two guiding streams (arrows) are used to obtain the desired flow trajectory of the sample stream, and these form a sheath on both sides of the sample, confining it between the guiding streams and the roof and the floor of the flow chamber. The distance between the sample stream and the previous lane is fully adjustable, and overlapping lanes can be produced. Adjusting guiding and sample flows controls the width of the sample stream, which can be as narrow as 25 μm, given that a precise fluid-controlling unit is used, and as wide as the chip allows. In the present study, 50–500-μm-wide sample streams were positioned in the central 3000 μm of the chip with gaps of 50–500 μm, in order to obtain defined lanes of comparable shape (only the straight part of lanes was included in the analyses).
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Figure 1: The microfluidic system. (A): The reusable microfluidic chip and a slide with immobilized biological material are inserted in the docking station. When closed, the docking station provides the mechanical force for sealing of the flow chamber between the chip and the slide. The loaded docking station is placed on the stage of a microscope, and the capillaries from the microchip are connected to a liquid-controlling unit (not shown). (B): Inside the flow chamber, lanes of the immobilized biological material are sequentially exposed to sample. Two guiding streams (arrows) are used to obtain the desired flow trajectory of the sample stream, and these form a sheath on both sides of the sample, confining it between the guiding streams and the roof and the floor of the flow chamber. The distance between the sample stream and the previous lane is fully adjustable, and overlapping lanes can be produced. Adjusting guiding and sample flows controls the width of the sample stream, which can be as narrow as 25 μm, given that a precise fluid-controlling unit is used, and as wide as the chip allows. In the present study, 50–500-μm-wide sample streams were positioned in the central 3000 μm of the chip with gaps of 50–500 μm, in order to obtain defined lanes of comparable shape (only the straight part of lanes was included in the analyses).

Mentions: The microfluidic system presented here consists of a reusable microfluidic chip connected to fluid pumps by fine capillaries, and a docking station which holds the chip and a slide with immobilized biological material (Figure 1A). The chip and the surface of the slide confine a flow chamber, in which lanes of the immobilized biological material are sequentially exposed to sample. Two guiding streams are used to obtain the desired flow trajectory and width of sample stream in the flow chamber (Figure 1B). The narrow tubing and small dimensions of the flow chamber eliminates turbulence phenomena. Mixing between guiding and sample fluids is, therefore, due only to diffusion, which is a relatively slow process. The docking station fits a standard microscope, allowing observation and recording of events occurring in the flow chamber.


Hydrodynamic guiding for addressing subsets of immobilized cells and molecules in microfluidic systems.

Brevig T, Krühne U, Kahn RA, Ahl T, Beyer M, Pedersen LH - BMC Biotechnol. (2003)

The microfluidic system. (A): The reusable microfluidic chip and a slide with immobilized biological material are inserted in the docking station. When closed, the docking station provides the mechanical force for sealing of the flow chamber between the chip and the slide. The loaded docking station is placed on the stage of a microscope, and the capillaries from the microchip are connected to a liquid-controlling unit (not shown). (B): Inside the flow chamber, lanes of the immobilized biological material are sequentially exposed to sample. Two guiding streams (arrows) are used to obtain the desired flow trajectory of the sample stream, and these form a sheath on both sides of the sample, confining it between the guiding streams and the roof and the floor of the flow chamber. The distance between the sample stream and the previous lane is fully adjustable, and overlapping lanes can be produced. Adjusting guiding and sample flows controls the width of the sample stream, which can be as narrow as 25 μm, given that a precise fluid-controlling unit is used, and as wide as the chip allows. In the present study, 50–500-μm-wide sample streams were positioned in the central 3000 μm of the chip with gaps of 50–500 μm, in order to obtain defined lanes of comparable shape (only the straight part of lanes was included in the analyses).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC183863&req=5

Figure 1: The microfluidic system. (A): The reusable microfluidic chip and a slide with immobilized biological material are inserted in the docking station. When closed, the docking station provides the mechanical force for sealing of the flow chamber between the chip and the slide. The loaded docking station is placed on the stage of a microscope, and the capillaries from the microchip are connected to a liquid-controlling unit (not shown). (B): Inside the flow chamber, lanes of the immobilized biological material are sequentially exposed to sample. Two guiding streams (arrows) are used to obtain the desired flow trajectory of the sample stream, and these form a sheath on both sides of the sample, confining it between the guiding streams and the roof and the floor of the flow chamber. The distance between the sample stream and the previous lane is fully adjustable, and overlapping lanes can be produced. Adjusting guiding and sample flows controls the width of the sample stream, which can be as narrow as 25 μm, given that a precise fluid-controlling unit is used, and as wide as the chip allows. In the present study, 50–500-μm-wide sample streams were positioned in the central 3000 μm of the chip with gaps of 50–500 μm, in order to obtain defined lanes of comparable shape (only the straight part of lanes was included in the analyses).
Mentions: The microfluidic system presented here consists of a reusable microfluidic chip connected to fluid pumps by fine capillaries, and a docking station which holds the chip and a slide with immobilized biological material (Figure 1A). The chip and the surface of the slide confine a flow chamber, in which lanes of the immobilized biological material are sequentially exposed to sample. Two guiding streams are used to obtain the desired flow trajectory and width of sample stream in the flow chamber (Figure 1B). The narrow tubing and small dimensions of the flow chamber eliminates turbulence phenomena. Mixing between guiding and sample fluids is, therefore, due only to diffusion, which is a relatively slow process. The docking station fits a standard microscope, allowing observation and recording of events occurring in the flow chamber.

Bottom Line: The use of hydrodynamic guiding made multiple and dynamic experimental conditions on a small surface area possible.The ability to change the direction of flow and produce two-dimensional grids can increase the number of reactions per surface area even further.The described microfluidic system is widely applicable, and can take advantage of surfaces produced by current and future techniques for patterning in the micro- and nanometer scale.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Molecular Characterization, Biotechnological Institute, Kogle Allé 2, DK-2970 Hørsholm, Denmark. tbr@bioteknologisk.dk

ABSTRACT

Background: The interest in microfluidics and surface patterning is increasing as the use of these technologies in diverse biomedical applications is substantiated. Controlled molecular and cellular surface patterning is a costly and time-consuming process. Methods for keeping multiple separate experimental conditions on a patterned area are, therefore, needed to amplify the amount of biological information that can be retrieved from a patterned surface area. We describe, in three examples of biomedical applications, how this can be achieved in an open microfluidic system, by hydrodynamically guiding sample fluid over biological molecules and living cells immobilized on a surface.

Results: A microfluidic format of a standard assay for cell-membrane integrity showed a fast and dose-dependent toxicity of saponin on mammalian cells. A model of the interactions of human mononuclear leukocytes and endothelial cells was established. By contrast to static adhesion assays, cell-cell adhesion in this dynamic model depended on cytokine-mediated activation of both endothelial and blood cells. The microfluidic system allowed the use of unprocessed blood as sample material, and a specific and fast immunoassay for measuring the concentration of C-reactive protein in whole blood was demonstrated.

Conclusion: The use of hydrodynamic guiding made multiple and dynamic experimental conditions on a small surface area possible. The ability to change the direction of flow and produce two-dimensional grids can increase the number of reactions per surface area even further. The described microfluidic system is widely applicable, and can take advantage of surfaces produced by current and future techniques for patterning in the micro- and nanometer scale.

Show MeSH
Related in: MedlinePlus