1
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Microfluidic free-flow electrophoresis: a promising tool for protein purification and analysis in proteomics. J IND ENG CHEM 2022. [DOI: 10.1016/j.jiec.2022.02.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Preuss JA, Nguyen GN, Berk V, Bahnemann J. Miniaturized free-flow electrophoresis: production, optimization, and application using 3D printing technology. Electrophoresis 2020; 42:305-314. [PMID: 33128392 DOI: 10.1002/elps.202000149] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 10/22/2020] [Accepted: 10/25/2020] [Indexed: 12/11/2022]
Abstract
The increasing resolution of three-dimensional (3D) printing offers simplified access to, and development of, microfluidic devices with complex 3D structures. Therefore, this technology is increasingly used for rapid prototyping in laboratories and industry. Microfluidic free flow electrophoresis (μFFE) is a versatile tool to separate and concentrate different samples (such as DNA, proteins, and cells) to different outlets in a time range measured in mere tens of seconds and offers great potential for use in downstream processing, for example. However, the production of μFFE devices is usually rather elaborate. Many designs are based on chemical pretreatment or manual alignment for the setup. Especially for the separation chamber of a μFFE device, this is a crucial step which should be automatized. We have developed a smart 3D design of a μFFE to pave the way for a simpler production. This study presents (1) a robust and reproducible way to build up critical parts of a μFFE device based on high-resolution MultiJet 3D printing; (2) a simplified insertion of commercial polycarbonate membranes to segregate separation and electrode chambers; and (3) integrated, 3D-printed wells that enable a defined sample fractionation (chip-to-world interface). In proof of concept experiments both a mixture of fluorescence dyes and a mixture of amino acids were successfully separated in our 3D-printed μFFE device.
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Affiliation(s)
- John-Alexander Preuss
- Institute of Technical Chemistry, Leibniz University Hannover, Callinstraße 5, Hannover, 30167, Germany
| | - Gia Nam Nguyen
- Institute of Technical Chemistry, Leibniz University Hannover, Callinstraße 5, Hannover, 30167, Germany
| | - Virginia Berk
- Institute of Technical Chemistry, Leibniz University Hannover, Callinstraße 5, Hannover, 30167, Germany
| | - Janina Bahnemann
- Institute of Technical Chemistry, Leibniz University Hannover, Callinstraße 5, Hannover, 30167, Germany
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3
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Anciaux SK, Bowser MT. Reduced surface adsorption in 3D printed acrylonitrile butadiene styrene micro free-flow electrophoresis devices. Electrophoresis 2020; 41:225-234. [PMID: 31816114 PMCID: PMC7316087 DOI: 10.1002/elps.201900179] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 12/03/2019] [Accepted: 12/04/2019] [Indexed: 01/27/2023]
Abstract
We have 3D printed and fabricated micro free-flow electrophoresis (µFFE) devices in acrylonitrile butadiene styrene (ABS) that exhibit minimal surface adsorption without requiring additional surface coatings or specialized buffer additives. 2D, nano LC-micro free flow electrophoresis (2D nLC × µFFE) separations were used to assess both spatial and temporal broadening as peaks eluted through the separation channel. Minimal broadening due to wall adsorption was observed in either the spatial or temporal dimensions during separations of rhodamine 110, rhodamine 123, and fluorescein. Surface adsorption was observed in separations of Chromeo P503 labeled myoglobin and cytochrome c but was significantly reduced compared to previously reported glass devices. Peak widths of < 30 s were observed for both proteins. For comparison, Chromeo P503 labeled myoglobin and cytochrome c adsorb strongly to the surface of glass µFFE devices resulting in peak widths >20 min. A 2D nLC × µFFE separation of a Chromeo P503 labeled tryptic digest of BSA was performed to demonstrate the high peak capacity possible due to the low surface adsorption in the 3D printed ABS devices, even in the absence of surface coatings or buffer additives.
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Affiliation(s)
- Sarah K. Anciaux
- University of Minnesota, Department of Chemistry, 207 Pleasant St. SE, Minneapolis, MN, 55455
| | - Michael T. Bowser
- University of Minnesota, Department of Chemistry, 207 Pleasant St. SE, Minneapolis, MN, 55455
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4
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Łapińska U, Saar KL, Yates EV, Herling TW, Müller T, Challa PK, Dobson CM, Knowles TPJ. Gradient-free determination of isoelectric points of proteins on chip. Phys Chem Chem Phys 2018; 19:23060-23067. [PMID: 28817152 DOI: 10.1039/c7cp01503h] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The isoelectric point (pI) of a protein is a key characteristic that influences its overall electrostatic behaviour. The majority of conventional methods for the determination of the isoelectric point of a molecule rely on the use of spatial gradients in pH, although significant practical challenges are associated with such techniques, notably the difficulty in generating a stable and well controlled pH gradient. Here, we introduce a gradient-free approach, exploiting a microfluidic platform which allows us to perform rapid pH change on chip and probe the electrophoretic mobility of species in a controlled field. In particular, in this approach, the pH of the electrolyte solution is modulated in time rather than in space, as in the case for conventional determinations of the isoelectric point. To demonstrate the general approachability of this platform, we have measured the isoelectric points of representative set of seven proteins, bovine serum albumin, β-lactoglobulin, ribonuclease A, ovalbumin, human transferrin, ubiquitin and myoglobin in microlitre sample volumes. The ability to conduct measurements in free solution thus provides the basis for the rapid determination of isoelectric points of proteins under a wide variety of solution conditions and in small volumes.
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Affiliation(s)
- Urszula Łapińska
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
| | - Kadi L Saar
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
| | - Emma V Yates
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
| | - Therese W Herling
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
| | - Thomas Müller
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK. and Fluidic Analytics, Unit 5 Chesterton Mill, French's Road, Cambridge CB4 3NP, UK
| | - Pavan K Challa
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
| | - Christopher M Dobson
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
| | - Tuomas P J Knowles
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK. and Department of Physics, Cavendish Laboratory, 19 J J Thomson Avenue, Cambridge CB3 0HE, UK
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5
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Saar KL, Zhang Y, Müller T, Kumar CP, Devenish S, Lynn A, Łapińska U, Yang X, Linse S, Knowles TPJ. On-chip label-free protein analysis with downstream electrodes for direct removal of electrolysis products. LAB ON A CHIP 2017; 18:162-170. [PMID: 29192926 DOI: 10.1039/c7lc00797c] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The ability to apply highly controlled electric fields within microfluidic devices is valuable as a basis for preparative and analytical processes. A challenge encountered in the context of such approaches in conductive media, including aqueous buffers, is the generation of electrolysis products at the electrode/liquid interface which can lead to contamination, perturb fluid flows and generally interfere with the measurement process. Here, we address this challenge by designing a single layer microfluidic device architecture where the electric potential is applied outside and downstream of the microfluidic device while the field is propagated back to the chip via the use of a co-flowing highly conductive electrolyte solution that forms a stable interface at the separation region of the device. The co-flowing electrolyte ensures that all the generated electrolysis products, including Joule heat and gaseous products, are flowed away from the chip without coming into contact with the analytes while the single layer fabrication process where all the structures are defined lithographically allows producing the devices in a simple yet highly reproducible manner. We demonstrate that by allowing stable and effective application of electric fields in excess of 100 V cm-1, the described platform provides the basis for rapid separation of heterogeneous mixtures of proteins and protein complexes directly in their native buffers as well as for the simultaneous quantification of their charge states. We illustrate this by probing the interactions in a mixture of an amyloid forming protein, amyloid-β, and a molecular chaperone, Brichos, known to inhibit the process of amyloid formation. The availability of a platform for applying stable electric fields and its compatibility with single-layer soft-lithography processes opens up the possibility of separating and analysing a wide range of molecules on chip, including those with similar electrophoretic mobilities.
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Affiliation(s)
- Kadi L Saar
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
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Rodríguez-Ruiz I, Babenko V, Martínez-Rodríguez S, Gavira JA. Protein separation under a microfluidic regime. Analyst 2017; 143:606-619. [PMID: 29214270 DOI: 10.1039/c7an01568b] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Lab-on-a-Chip (LoC), or micro-Total Analysis Systems (μTAS), is recognized as a powerful analytical technology with high capabilities, though end-user products for protein purification are still far from being available on the market. Remarkable progress has been achieved in the separation of nucleic acids and proteins using electrophoretic microfluidic devices, while pintsize devices have been developed for protein isolation according to miniaturized chromatography principles (size, charge, affinity, etc.). In this work, we review the latest advances in the fabrication of components, detection methods and commercial implementation for the separation of biological macromolecules based on microfluidic systems, with some critical remarks on the perspectives of their future development towards standardized microfluidic systems and protocols. An outlook on the current needs and future applications is also presented.
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Affiliation(s)
| | - V Babenko
- Laboratorio de Estudios Cristalograficos, Instituto Andaluz de Ciencias de la Tierra, CSIC-University of Granada, Avenida de las Palmeras 4, 18100 Armilla, Granada, Spain.
| | - S Martínez-Rodríguez
- Department of Biochemistry and Molecular Biology III and Immunology. University of Granada, Granada, Spain
| | - J A Gavira
- Laboratorio de Estudios Cristalograficos, Instituto Andaluz de Ciencias de la Tierra, CSIC-University of Granada, Avenida de las Palmeras 4, 18100 Armilla, Granada, Spain.
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Novo P, Janasek D. Current advances and challenges in microfluidic free-flow electrophoresis-A critical review. Anal Chim Acta 2017; 991:9-29. [PMID: 29031303 DOI: 10.1016/j.aca.2017.08.017] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 08/10/2017] [Accepted: 08/11/2017] [Indexed: 12/30/2022]
Abstract
The research field on microfluidic free-flow electrophoresis has developed vast amounts of devices, methods, applications and raised new questions, often in analogy to conventional techniques from which it derives. Most efforts have been employed on device development and a myriad of architectures and fabrication techniques have been reported using simple proof-of-principle separations. As technological aspects reach a quite mature state, researchers' new challenges include the development of protocols for the separation of complex mixtures, as required in the fields of application. The success of this effort is extremely dependent on the capability to transfer the device's fabrication to an industrial setting as well as to ensure interfacing simplicity, namely at the solutions' supply and collection, and actuation such as electric potential application and temperature control. Other advanced applications such as direct interfacing to downstream systems such as mass spectrometry, integration of sensing and feedback controls will require further development in the laboratory. In this review we provide an overview on the field, from basic concepts, through advanced developments both in the theoretical and experimental arenas, and addressing the above details. A comprehensive survey of designs, materials and applications is presented with particular highlights to most recent developments, namely the integration of electrodes, flow control and hyphenation of microfluidic free-flow electrophoresis with other techniques.
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Affiliation(s)
- Pedro Novo
- Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V., 44227, Otto-Hahn-Str. 6b, Dortmund, Germany
| | - Dirk Janasek
- Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V., 44227, Otto-Hahn-Str. 6b, Dortmund, Germany.
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8
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Wang Z, Ivory C, Minerick AR. Surface isoelectric focusing (sIEF) with carrier ampholyte pH gradient. Electrophoresis 2017; 38:2565-2575. [PMID: 28722147 DOI: 10.1002/elps.201600565] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 06/16/2017] [Accepted: 07/12/2017] [Indexed: 11/08/2022]
Abstract
Isoelectric focusing (IEF) is a powerful tool for amphoteric protein separations because of high sensitivity, bio-compatibility, and reduced complexity compared to chromatography or mechanical separation techniques. IEF miniaturization is attractive because it enables rapid analysis, easier adaptation to point of care applications, and smaller sample demands. However, existing small-scale IEF tools have not yet been able to analyze single protein spots from array libraries, which are ubiquitous in many pharmaceutical discovery and screening protocols. Thus, we introduce an in situ, novel, miniaturized protein analysis approach that we have termed surface isoelectric focusing (sIEF). Low volume printed sIEF gels can be run at length scales of ∼300 μm, utilize ∼0.9 ng of protein with voltages below 10 V. Further, the sIEF device platform is so simple that it can be integrated with protein library arrays to reduce cost; devices demonstrate reusability above 50 uses. An acrylamide monomer solution containing broad-range carrier ampholytes was microprinted with a Nano eNablerTM between micropatterned gold electrodes spaced 300 μm apart on a glass slide. The acrylamide gel was polymerized in situ followed by protein loading via printed diffusional exchange. A pH gradient formed via carrier ampholyte stacking when electrodes were energized; the gradient was verified using ratiometric pH-sensitive FITC/TRITC dyes. Green fluorescent protein (GFP) and R-phycoerythrin (R-PE) were utilized both as pI markers and to test sIEF performance as a function of electric field strength and ampholyte concentration. Factors hampering sIEF included cathodic drift and pH gradient compression, but were reduced by co-printing non-ionic Synperonic® F-108 surfactant to reduce protein-gel interactions. sIEF gels achieved protein separations in <10 min yielding bands < 50 μm wide with peak capacities of ∼8 and minimum pI differences from 0.12 to 0.14. This new sIEF technique demonstrated comparable focusing at ∼100 times smaller dimensions than any previous IEF. Further, sample volumes required were reduced four orders of magnitude from 20 μL for slab gel IEF to 0.002 μL for sIEF. In summary, sIEF advantages include smaller volumes, reduced power consumption, and microchip surface accessibility to focused bands along with equivalent separation resolutions to prior IEF tools. These attributes position this new technology for rapid, in situ protein library analysis in clinical and pharmaceutical settings.
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Affiliation(s)
- Zhichao Wang
- Department of Chemical Engineering, Michigan Technological University, Houghton, MI, USA
| | - Cornelius Ivory
- Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA, USA
| | - Adrienne R Minerick
- Department of Chemical Engineering, Michigan Technological University, Houghton, MI, USA
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9
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Abstract
The cost, time, and restrictions on creative flexibility associated with current fabrication methods present significant challenges in the development and application of microfluidic devices. Additive manufacturing, also referred to as three-dimensional (3D) printing, provides many advantages over existing methods. With 3D printing, devices can be made in a cost-effective manner with the ability to rapidly prototype new designs. We have fabricated a micro free-flow electrophoresis (μFFE) device using a low-cost, consumer-grade 3D printer. Test prints were performed to determine the minimum feature sizes that could be reproducibly produced using 3D printing fabrication. Microfluidic ridges could be fabricated with dimensions as small as 20 μm high × 640 μm wide. Minimum valley dimensions were 30 μm wide × 130 μm wide. An acetone vapor bath was used to smooth acrylonitrile-butadiene-styrene (ABS) surfaces and facilitate bonding of fully enclosed channels. The surfaces of the 3D-printed features were profiled and compared to a similar device fabricated in a glass substrate. Stable stream profiles were obtained in a 3D-printed μFFE device. Separations of fluorescent dyes in the 3D-printed device and its glass counterpart were comparable. A μFFE separation of myoglobin and cytochrome c was also demonstrated on a 3D-printed device. Limits of detection for rhodamine 110 were determined to be 2 and 0.3 nM for the 3D-printed and glass devices, respectively.
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Affiliation(s)
- Sarah K Anciaux
- Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Matthew Geiger
- Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
| | - Michael T Bowser
- Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
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10
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Fu X, Mavrogiannis N, Ibo M, Crivellari F, Gagnon ZR. Microfluidic free-flow zone electrophoresis and isotachophoresis using carbon black nano-composite PDMS sidewall membranes. Electrophoresis 2016; 38:327-334. [DOI: 10.1002/elps.201600104] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 05/12/2016] [Accepted: 05/13/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Xiaotong Fu
- Department of Chemical and Biomolecular Engineering; Johns Hopkins University; Baltimore MD USA
| | - Nicholas Mavrogiannis
- Department of Chemical and Biomolecular Engineering; Johns Hopkins University; Baltimore MD USA
| | - Markela Ibo
- Department of Chemical and Biomolecular Engineering; Johns Hopkins University; Baltimore MD USA
| | - Francesca Crivellari
- Department of Chemical and Biomolecular Engineering; Johns Hopkins University; Baltimore MD USA
| | - Zachary R. Gagnon
- Department of Chemical and Biomolecular Engineering; Johns Hopkins University; Baltimore MD USA
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11
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Geiger M, Bowser MT. Effect of Fluorescent Labels on Peptide and Amino Acid Sample Dimensionality in Two Dimensional nLC × μFFE Separations. Anal Chem 2016; 88:2177-87. [DOI: 10.1021/acs.analchem.5b03811] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Matthew Geiger
- Department of Chemistry, University of Minnesota, 207 Pleasant
Street SE, Minneapolis, Minnesota 55455, United States
| | - Michael T. Bowser
- Department of Chemistry, University of Minnesota, 207 Pleasant
Street SE, Minneapolis, Minnesota 55455, United States
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12
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Geiger M, Harstad RK, Bowser MT. Effect of Surface Adsorption on Temporal and Spatial Broadening in Micro Free Flow Electrophoresis. Anal Chem 2015; 87:11682-90. [DOI: 10.1021/acs.analchem.5b02262] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Matthew Geiger
- Department of Chemistry, University of Minnesota, 207 Pleasant
Street SE, Minneapolis, Minnesota 55455, United States
| | - Rachel K. Harstad
- Department of Chemistry, University of Minnesota, 207 Pleasant
Street SE, Minneapolis, Minnesota 55455, United States
| | - Michael T. Bowser
- Department of Chemistry, University of Minnesota, 207 Pleasant
Street SE, Minneapolis, Minnesota 55455, United States
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14
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Herzog C, Beckert E, Nagl S. Rapid Isoelectric Point Determination in a Miniaturized Preparative Separation Using Jet-Dispensed Optical pH Sensors and Micro Free-Flow Electrophoresis. Anal Chem 2014; 86:9533-9. [DOI: 10.1021/ac501783r] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Christin Herzog
- Institut
für Analytische Chemie, Universität Leipzig, Linnéstrasse
3, 04103 Leipzig, Germany
| | - Erik Beckert
- Fraunhofer-Institut für Angewandte Optik und Feinmechanik (IOF), Albert-Einstein-Strasse 7, 07745 Jena, Germany
| | - Stefan Nagl
- Institut
für Analytische Chemie, Universität Leipzig, Linnéstrasse
3, 04103 Leipzig, Germany
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Geiger M, Frost NW, Bowser MT. Comprehensive Multidimensional Separations of Peptides Using Nano-Liquid Chromatography Coupled with Micro Free Flow Electrophoresis. Anal Chem 2014; 86:5136-42. [DOI: 10.1021/ac500939q] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Matthew Geiger
- Department of Chemistry, University of Minnesota, 207 Pleasant
Street SE, Minneapolis, Minnesota 55455, United States
| | - Nicholas W. Frost
- Department of Chemistry, University of Minnesota, 207 Pleasant
Street SE, Minneapolis, Minnesota 55455, United States
| | - Michael T. Bowser
- Department of Chemistry, University of Minnesota, 207 Pleasant
Street SE, Minneapolis, Minnesota 55455, United States
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16
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Lee HY, Barber C, Minerick AR. Improving electrokinetic microdevice stability by controlling electrolysis bubbles. Electrophoresis 2014; 35:1782-9. [DOI: 10.1002/elps.201400013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 03/13/2014] [Accepted: 03/14/2014] [Indexed: 11/12/2022]
Affiliation(s)
- Hwi Yong Lee
- Department of Chemical Engineering; Michigan Technological University; Houghton MI USA
| | - Cedrick Barber
- Department of Chemical Engineering; Michigan Technological University; Houghton MI USA
| | - Adrienne R. Minerick
- Department of Chemical Engineering; Michigan Technological University; Houghton MI USA
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17
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Cheng LJ, Chang HC. Switchable pH actuators and 3D integrated salt bridges as new strategies for reconfigurable microfluidic free-flow electrophoretic separation. LAB ON A CHIP 2014; 14:979-87. [PMID: 24430103 DOI: 10.1039/c3lc51023a] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
We present novel strategies for reconfigurable, high-throughput microfluidic free-flow electrophoretic separation using electrically switchable pH actuators and 3D integrated salt bridges to allow rapid formation of stable pH gradients and efficient electrophoresis. The pH actuator is achieved by microfluidic integration of bipolar membranes which change electrolyte pH by injecting excess H(+) or OH(-) ions produced by a field-enhanced water dissociation phenomenon at the membrane junction upon voltage bias. The technique does not require conventional multiple buffer inflows and leaves no gas production as experienced in electrolysis, thus providing stable pH gradients for isoelectric focusing (IEF) separation. With the pH actuator inactivated, the platform can perform zone electrophoretic (ZE) separation in a medium of constant pH. We also describe the use of 3D integrated ion conductive polymers that serve as salt bridges for improving the voltage efficiency of electrophoresis and to allow high throughput. The proof of concept was successfully demonstrated for free-flow IEF and ZE separation of protein mixtures showing the potential and the simplicity of the platform for high-throughput and high-precision sample separation.
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Affiliation(s)
- Li-Jing Cheng
- School of Electrical Engineering and Computer Science, Oregon State University, OR 97331, USA.
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18
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Dzido TH, Łopaciuk E, Płocharz PW, Chomicki A, Zembrzycka M, Frank H. Equipment and preliminary results for orthogonal pressurized planar electrochromatography. J Chromatogr A 2014; 1334:149-55. [DOI: 10.1016/j.chroma.2014.02.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 01/30/2014] [Accepted: 02/02/2014] [Indexed: 11/28/2022]
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Song YA, Wu L, Tannenbaum SR, Wishnok JS, Han J. Tunable membranes for free-flow zone electrophoresis in PDMS microchip using guided self-assembly of silica microbeads. Anal Chem 2013; 85:11695-9. [PMID: 24251795 DOI: 10.1021/ac402169x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this paper, we evaluate the strategy of using self-assembled microbeads to build a robust and tunable membrane for free-flow zone electrophoresis in a PDMS microfluidic chip. To fabricate a porous membrane as a salt bridge for free-flow zone electrophoresis, we used silica or polystyrene microbeads between 3-6 μm in diameter and packed them inside a microchannel. After complete evaporation, we infiltrated the porous microbead structure with a positively or negatively charged hydrogel to modify its surface charge polarity. Using this device, we demonstrated binary sorting (separation of positive and negative species at a given pH) of peptides and dyes in standard buffer systems without using sheath flows. The sample loss during sorting could be minimized by using ion selectivity of hydrogel-infiltrated microbead membranes. Our fabrication method enables building a robust membrane for pressure-driven free-flow zone electrophoresis with tunable pore size as well as surface charge polarity.
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Affiliation(s)
- Yong-Ak Song
- Department of Electrical Engineering and Computer Science, ‡Department of Biological Engineering, §Department of Chemistry, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, MA 02139, United States
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Jezierski S, Belder D, Nagl S. Microfluidic free-flow electrophoresis chips with an integrated fluorescent sensor layer for real time pH imaging in isoelectric focusing. Chem Commun (Camb) 2013; 49:904-6. [DOI: 10.1039/c2cc38093e] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Köhler S, Nagl S, Fritzsche S, Belder D. Label-free real-time imaging in microchip free-flow electrophoresis applying high speed deep UV fluorescence scanning. LAB ON A CHIP 2012; 12:458-463. [PMID: 22011722 DOI: 10.1039/c1lc20558g] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report on label-free monitoring of microfluidic free-flow electrophoresis (μFFE) separations in real-time using a custom built high speed deep UV laser scanner. In combination with a novel layout realized in fused silica (FS) FFE chips the setup was successfully applied for continuous separations and detection of unlabeled analytes including native proteins by space-resolved intrinsic deep UV fluorescence scanning.
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Affiliation(s)
- Stefan Köhler
- Institute of Analytical Chemistry, University of Leipzig, Linnéstr. 3, 04103 Leipzig, Germany
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Ding H, Li X, Lv X, Xu J, Sun X, Zhang Z, Wang H, Deng Y. Fabrication of micro free-flow electrophoresis chip by photocurable monomer binding microfabrication technique for continuous separation of proteins and their numerical simulation. Analyst 2012; 137:4482-9. [DOI: 10.1039/c2an35535c] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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23
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Köhler S, Benz C, Becker H, Beckert E, Beushausen V, Belder D. Micro free-flow electrophoresis with injection molded chips. RSC Adv 2012. [DOI: 10.1039/c1ra00874a] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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24
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Multistep liquid-phase lithography for fast prototyping of microfluidic free-flow-electrophoresis chips. Anal Bioanal Chem 2011; 401:2651-6. [DOI: 10.1007/s00216-011-5351-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 08/17/2011] [Accepted: 08/19/2011] [Indexed: 10/17/2022]
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Abstract
Micro free flow electrophoresis (micro-FFE) is a continuous micro-separation or preparation technique, which has been applied in the analysis of biomolecules, such as cells, sub cell organics and proteins. In this review, the recent progresses in micro FFE are summarized, with emphasis on the design of microchips, the separation modes and the applications of micro-FFE. Furthermore, the further developments of micro-FFE are prospected.
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Affiliation(s)
- Pingli Wang
- National Chromatographic R. & A. Center, Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
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26
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Köhler S, Weilbeer C, Howitz S, Becker H, Beushausen V, Belder D. PDMS free-flow electrophoresis chips with integrated partitioning bars for bubble segregation. LAB ON A CHIP 2011; 11:309-14. [PMID: 21060908 DOI: 10.1039/c0lc00347f] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
In this work, a microfluidic free-flow electrophoresis device with a novel approach for preventing gas bubbles from entering the separation area is presented. This is achieved by integrating partitioning bars to reduce the channel depth between electrode channels and separation chamber in order to obtain electrical contact and simultaneously prevent bubbles from entering the separation area. The three-layer sandwich chip features a reusable carrier plate with integrated ports for fluidic connection combined with a softlithographically cast microfluidic PDMS layer and a sealing glass slide. This design allows for a straightforward and rapid chip prototyping process. The performance of the device is demonstrated by free-flow zone electrophoretic separations of fluorescent dye mixtures as well as by the separation of labeled amines and amino acids with separation voltages up to 297 V.
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Affiliation(s)
- Stefan Köhler
- Institute of Analytical Chemistry, University of Leipzig, Linnéstr. 3, 04103, Leipzig, Germany
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27
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Wen J, Albrecht JW, Jensen KF. Microfluidic preparative free-flow isoelectric focusing in a triangular channel: system development and characterization. Electrophoresis 2010; 31:1606-14. [PMID: 20419703 DOI: 10.1002/elps.200900577] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A preparative scale free-flow IEF device is developed and characterized with the aim of addressing needs of molecular biologists working with protein samples on the milligrams and milliliters scale. A triangular-shape separation channel facilitates the establishment of the pH gradient with a corresponding increase in separation efficiency and decrease in focusing time compared with that in a regular rectangular channel. Functionalized, ion-permeable poly(acrylamide) gel membranes are sandwiched between PDMS and glass layers to both isolate the electrode buffers from the central separation channel and also to selectively adjust the voltage efficiency across the separation channel to achieve high electric field separation. The 50 x 70 mm device is fabricated by soft lithography and has 24 outlets evenly spaced across a pH gradient between pH 4 and 10. This preparative free-flow IEF system is investigated and optimized for both aqueous and denaturing conditions with respect to the electric field and potential efficiency and with consideration of Joule-heating removal. Energy distribution across the functionalized polyacrylamide gel is investigated and controlled to adjust the potential efficiency between 15 and 80% across the triangular separation channel. The device is able to achieve constant electric fields high as 370+/-20 V/cm through the entire triangular channel given the separation voltage of 1800 V, enabling separation of five fluorescent pI markers as a demonstration example.
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Affiliation(s)
- Jian Wen
- Department of Chemical Engineering, Massachusetts Institute of Technology, MA 02139, USA
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28
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Wen J, Wilker EW, Yaffe MB, Jensen KF. Microfluidic preparative free-flow isoelectric focusing: system optimization for protein complex separation. Anal Chem 2010; 82:1253-60. [PMID: 20092256 DOI: 10.1021/ac902157e] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Isoelectric focusing (IEF) is the first step for two-dimensional (2D) gel electrophoresis and plays an important role in sample purification for proteomics. However, biases in protein size and pI resolution, as well as limitations in sample volume, gel capacity, sample loss, and experimental time, remain challenges. In order to address some of the limitations of traditional IEF, we present a microfluidic free flow IEF (FF-IEF) device for continuous protein separation into 24 fractions. The device reproducibly establishes a nearly linear pH gradient from 4 to 10. Optimized dynamic coatings of 4% poly(vinyl alcohol) (PVA) minimize peak broadening by transverse electrokinetic flows. Even though the device operates at high electric fields (up to 370 V/cm), efficient cooling maintains solution temperature inside the separation channel controllably in the range 2-25 degrees C. Protein samples with a dynamic concentration range from microg/mL to mg/mL can be loaded into the microdevice at a flow rate of 1 mL/h and residence time of approximately 12 min. By using a protein complex of nine proteins and 13 isoforms, we demonstrate improved separation with the FF-IEF system over traditional 2D gel electrophoresis. Device-to-device reproducibility is also illustrated through the efficient depletion of the albumin and hemoglobin assays. Post-device sample concentrations result in a 10-20-fold increase, which allow for isolation and detection of low abundance proteins. The separation of specific proteins from a whole cell lysate is demonstrated as an example. The microdevice has the further benefits of retaining high molecular weight proteins, providing higher yield of protein that has a broader range in pI, and reducing experimental time compared to conventional IEF IGP gel strip approaches.
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Affiliation(s)
- Jian Wen
- Department of Chemical Engineering, Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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29
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Song YA, Chan M, Celio C, Tannenbaum SR, Wishnok JS, Han J. Free-flow zone electrophoresis of peptides and proteins in PDMS microchip for narrow pI range sample prefractionation coupled with mass spectrometry. Anal Chem 2010; 82:2317-25. [PMID: 20163146 DOI: 10.1021/ac9025219] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this paper, we are evaluating the strategy of sorting peptides/proteins based on the charge to mass without resorting to ampholytes and/or isoelectric focusing, using a single- and two-step free-flow zone electrophoresis. We developed a simple fabrication method to create a salt bridge for free-flow zone electrophoresis in PDMS chips by surface printing a hydrophobic layer on a glass substrate. Since the surface-printed hydrophobic layer prevents plasma bonding between the PDMS chip and the substrate, an electrical junction gap can be created for free-flow zone electrophoresis. With this device, we demonstrated a separation of positive and negative peptides and proteins at a given pH in standard buffer systems and validated the sorting result with LC/MS. Furthermore, we coupled two sorting steps via off-chip titration and isolated peptides within specific pI ranges from sample mixtures, where the pI range was simply set by the pH values of the buffer solutions. This free-flow zone electrophoresis sorting device, with its simplicity of fabrication, and a sorting resolution of 0.5 pH unit, can potentially be a high-throughput sample fractionation tool for targeted proteomics using LC/MS.
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Affiliation(s)
- Yong-Ak Song
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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30
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Vázquez M, Paull B. Review on recent and advanced applications of monoliths and related porous polymer gels in micro-fluidic devices. Anal Chim Acta 2010; 668:100-13. [DOI: 10.1016/j.aca.2010.04.033] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Revised: 04/15/2010] [Accepted: 04/16/2010] [Indexed: 10/19/2022]
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31
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Wang P, Zhang L, Shan Y, Cong Y, Liang Y, Han B, Liang Z, Zhang Y. Protein separation using free-flow electrophoresis microchip etched in a single step. J Sep Sci 2010; 33:2039-44. [DOI: 10.1002/jssc.201000162] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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32
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Becker M, Marggraf U, Janasek D. Separation of proteins using a novel two-depth miniaturized free-flow electrophoresis device with multiple outlet fractionation channels. J Chromatogr A 2009; 1216:8265-9. [DOI: 10.1016/j.chroma.2009.06.079] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Revised: 06/15/2009] [Accepted: 06/30/2009] [Indexed: 11/29/2022]
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33
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Goodell JR, McMullen JP, Zaborenko N, Maloney JR, Ho CX, Jensen KF, Porco JA, Beeler AB. Development of an automated microfluidic reaction platform for multidimensional screening: reaction discovery employing bicyclo[3.2.1]octanoid scaffolds. J Org Chem 2009; 74:6169-80. [PMID: 20560568 PMCID: PMC2976622 DOI: 10.1021/jo901073v] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
An automated, silicon-based microreactor system has been developed for rapid, low-volume, multidimensional reaction screening. Use of the microfluidic platform to identify transformations of densely functionalized bicyclo[3.2.1]octanoid scaffolds will be described.
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Affiliation(s)
- John R. Goodell
- Contribution from the Department of Chemistry and Center for Chemical Methodology and Library Development (CMLD-BU), Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215
| | - Jonathan P. McMullen
- Department of Chemical Engineering Massachusetts Institute of Technology 77 Massachusetts Avenue, 66-342, Cambridge, Massachusetts 02139
| | - Nikolay Zaborenko
- Department of Chemical Engineering Massachusetts Institute of Technology 77 Massachusetts Avenue, 66-342, Cambridge, Massachusetts 02139
| | - Jason R. Maloney
- Contribution from the Department of Chemistry and Center for Chemical Methodology and Library Development (CMLD-BU), Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215
| | - Chuan-Xing Ho
- Contribution from the Department of Chemistry and Center for Chemical Methodology and Library Development (CMLD-BU), Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215
| | - Klavs F. Jensen
- Department of Chemical Engineering Massachusetts Institute of Technology 77 Massachusetts Avenue, 66-342, Cambridge, Massachusetts 02139
| | - John A. Porco
- Contribution from the Department of Chemistry and Center for Chemical Methodology and Library Development (CMLD-BU), Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215
| | - Aaron B. Beeler
- Contribution from the Department of Chemistry and Center for Chemical Methodology and Library Development (CMLD-BU), Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215
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34
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Micro free-flow electrophoresis: theory and applications. Anal Bioanal Chem 2009; 394:187-98. [PMID: 19290514 DOI: 10.1007/s00216-009-2656-5] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Revised: 01/23/2009] [Accepted: 01/26/2009] [Indexed: 10/21/2022]
Abstract
Free-flow electrophoresis (FFE) is a technique that performs an electrophoretic separation on a continuous stream of analyte as it flows through a planar flow channel. The electric field is applied perpendicularly to the flow to deflect analytes laterally according to their mobility as they flow through the separation channel. Miniaturization of FFE (microFFE) over the past 15 years has allowed analytical and preparative separation of small volume samples. Advances in chip design have improved separations by reducing interference from bubbles generated by electrolysis. Mechanisms of band broadening have been examined theoretically and experimentally to improve resolution in microFFE. Separations using various modes such as zone electrophoresis, isoelectric focusing, isotachophoresis, and field-step electrophoresis have been demonstrated.
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35
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36
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37
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Zalewski DR, Kohlheyer D, Schlautmann S, Gardeniers HJGE. Synchronized, continuous-flow zone electrophoresis. Anal Chem 2008; 80:6228-34. [PMID: 18620428 DOI: 10.1021/ac800567n] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new method for performing continuous electrophoretic separation of complex mixtures in microscale devices is proposed. Unlike in free-flow electrophoresis devices, no mechanical pumping is required--both fluid transport and separation are driven electrokinetically. This gives the method great potential for on-a-chip integration in multistep analytical systems. The method enables us to collect fractionated sample and tenfold purification is possible. The model of the operation is presented and a detailed description of the optimal conditions for performing purification is given. The chip devices with 10-microm-deep separation chamber of 1.5 mm x 4 mm in size were fabricated in glass. A standard microchip electrophoresis setup was used. Continuous separation of rhodamine B, rhodamine 6G, and fluorescein was accomplished. Purification was demonstrated on a mixture containing rhodamine B and fluorescein, and the recovery of both fractions was achieved. The results show the feasibility of the method.
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Affiliation(s)
- Dawid R Zalewski
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands.
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38
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39
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Kohlheyer D, Eijkel JCT, Schlautmann S, van den Berg A, Schasfoort RBM. Bubble-Free Operation of a Microfluidic Free-Flow Electrophoresis Chip with Integrated Pt Electrodes. Anal Chem 2008; 80:4111-8. [DOI: 10.1021/ac800275c] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dietrich Kohlheyer
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
| | - Jan C. T. Eijkel
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
| | - Stefan Schlautmann
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
| | - Albert van den Berg
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
| | - Richard B. M. Schasfoort
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
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40
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Sommer GJ, Singh AK, Hatch AV. On-chip isoelectric focusing using photopolymerized immobilized pH gradients. Anal Chem 2008; 80:3327-33. [PMID: 18341355 DOI: 10.1021/ac702523g] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present the first successful adaptation of immobilized pH gradients (IPGs) to the microscale (muIPGs) using a new method for generating precisely defined polymer gradients on-chip. Gradients of monomer were established via diffusion along 6 mm flow-restricted channel segments. Precise control over boundary conditions and the resulting gradient is achieved by continuous flow of stock solutions through side channels flanking the gradient segment. Once the desired gradient is established, it is immobilized via photopolymerization. Precise gradient formation was verified with spatial and temporal detection of a fluorescent dye added to one of the flanking streams. Rapid (<20 min) isoelectric focusing of several fluorescent pI markers and proteins is demonstrated across pH 3.8-7.0 muIPGs using both denaturing and nondenaturing conditions, without the addition of carrier ampholytes. The muIPG format yields improved stability and comparable resolution to prominent on-chip IEF techniques. In addition to rapid, high-resolution separations, the reported muIPG format is amenable to multiplexed and multidimensional analysis via custom gradients as well as integration with other on-chip separation methods.
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Affiliation(s)
- Greg J Sommer
- Biosystems Research Department, Sandia National Laboratories, Livermore, California 94551, USA
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41
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Kohlheyer D, Eijkel JCT, van den Berg A, Schasfoort RBM. Miniaturizing free-flow electrophoresis – a critical review. Electrophoresis 2008; 29:977-93. [DOI: 10.1002/elps.200700725] [Citation(s) in RCA: 151] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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42
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Albrecht JW, El-Ali J, Jensen KF. Cascaded free-flow isoelectric focusing for improved focusing speed and resolution. Anal Chem 2007; 79:9364-71. [PMID: 17994708 PMCID: PMC2560584 DOI: 10.1021/ac071574q] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This work presents the first implementation of cascaded stages for a microfabricated free-flow isoelectric focusing (FF-IEF) device. Both analytical and computational models for IEF suggest device performance will be improved by utilizing multiple stages to reduce device residence time. These models are shown to be applicable by using focusing of small IEF markers as a demonstration. We also show focusing of fluorescently tagged proteins under different channel geometries, with the most efficient focusing occurring in the cascaded design, as predicted by theory. An additional aim of this work is to demonstrate the compatibility of cascaded FF-IEF with common bioanalytical tools. As an example, outlet fractions from cascaded FF-IEF were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Processing of whole cell lysate followed by immunoblotting for cell signaling markers demonstrates the reduction of albumin from samples, as well as the enrichment of apoptotic markers.
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Affiliation(s)
- Jacob W. Albrecht
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Jamil El-Ali
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Klavs F. Jensen
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
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Kohlheyer D, Eijkel JCT, Schlautmann S, van den Berg A, Schasfoort RBM. Microfluidic High-Resolution Free-Flow Isoelectric Focusing. Anal Chem 2007; 79:8190-8. [PMID: 17902700 DOI: 10.1021/ac071419b] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A microfluidic free-flow isoelectric focusing glass chip for separation of proteins is described. Free-flow isoelectric focusing is demonstrated with a set of fluorescent standards covering a wide range of isoelectric points from pH 3 to 10 as well as the protein HSA. With respect to an earlier developed device, an improved microfluidic FFE chip was developed. The improvements included the usage of multiple sheath flows and the introduction of preseparated ampholytes. Preseparated ampholytes are commonly used in large-scale conventional free-flow isoelectric focusing instruments but have not been used in micromachined devices yet. Furthermore, the channel depth was further decreased. These adaptations led to a higher separation resolution and peak capacity, which were not achieved with previously published free-flow isoelectric focusing chips. An almost linear pH gradient ranging from pH 2.5 to 11.5 between 1.2 and 2 mm wide was generated. Seven isoelectric focusing markers were successfully and clearly separated within a residence time of 2.5 s and an electrical field of 20 V mm-1. Experiments with pI markers proved that the device is fully capable of separating analytes with a minimum difference in isoelectric point of Delta(pI) = 0.4. Furthermore, the results indicate that even a better resolution can be achieved. The theoretical minimum difference in isoelectric point is Delta(pI) = 0.23 resulting in a peak capacity of 29 peaks within 1.8 mm. This is an 8-fold increase in peak capacity to previously published results. The focusing of pI markers led to an increase in concentration by factor 20 and higher. Further improvement in terms of resolution seems possible, for which we envisage that the influence of electroosmotic flow has to be further reduced. The performance of the microfluidic free-flow isoelectric focusing device will enable new applications, as this device might be used in clinical analysis where often low sample volumes are available and fast separation times are essential.
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Affiliation(s)
- Dietrich Kohlheyer
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands.
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