1
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Lomeli G, Herr AE. Reducing Cathodic Drift during Isoelectric Focusing Using Microscale Immobilized pH Gradient Gels. Anal Chem 2024; 96:8648-8656. [PMID: 38716690 PMCID: PMC11140684 DOI: 10.1021/acs.analchem.4c00788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 04/26/2024] [Accepted: 04/30/2024] [Indexed: 05/29/2024]
Abstract
Microfluidic analytical tools play an important role in miniaturizing targeted proteomic assays for improved detection sensitivity, throughput, and automation. Microfluidic isoelectric focusing (IEF) can resolve proteoforms in lysate from low-to-single cell numbers. However, IEF assays often use carrier ampholytes (CAs) to establish a pH gradient for protein separation, presenting limitations like pH instability in the form of cathodic drift (migration of focused proteins toward the cathode). Immobilized pH gradient (IPG) gels reduce cathodic drift by covalently immobilizing the pH buffering components to a matrix. To our knowledge, efforts to implement IPG gels at the microscale have been limited to glass microdevices. To adapt IEF using IPGs to widely used microfluidic device materials, we introduce a polydimethylsiloxane (PDMS)-based microfluidic device and compare the microscale pH gradient stability of IEF established with IPGs, CAs, and a hybrid formulation of IPG gels and CAs (mixed-bed IEF). The PDMS-based IPG microfluidic device (μIPG) resolved analytes differing by 0.1 isoelectric point within a 3.5 mm separation lane over a 20 min focusing duration. During the 20 min duration, we observed markedly different cathodic drift velocities among the three formulations: 60.1 μm/min in CA-IEF, 2.5 μm/min in IPG-IEF (∼24-fold reduction versus CA-IEF), and 1.4 μm/min in mixed-bed IEF (∼43-fold reduction versus CA-IEF). Lastly, mixed-bed IEF in a PDMS device resolved green fluorescent protein (GFP) proteoforms from GFP-expressing human breast cancer cell lysate, thus establishing stability in lysate from complex biospecimens. μIPG is a promising and stable technique for studying proteoforms from small volumes.
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Affiliation(s)
- Gabriela Lomeli
- The
UC Berkeley−UCSF Graduate Program in Bioengineering, University of California, Berkeley, California 94720, United States
- Department
of Bioengineering, University of California, Berkeley, California 94720, United States
| | - Amy E. Herr
- The
UC Berkeley−UCSF Graduate Program in Bioengineering, University of California, Berkeley, California 94720, United States
- Department
of Bioengineering, University of California, Berkeley, California 94720, United States
- Chan
Zuckerberg Biohub, San Francisco, California 94158, United States
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2
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Thormann W, Mosher RA. Mobilization in two-step capillary isoelectric focusing: Concepts assessed by computer simulation. Electrophoresis 2024; 45:618-638. [PMID: 38115749 DOI: 10.1002/elps.202300218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 11/26/2023] [Accepted: 12/07/2023] [Indexed: 12/21/2023]
Abstract
The mobilization step in a two-step capillary isoelectric focusing protocol is discussed by means of dynamic computer simulation data for systems without and with spacer compounds that establish their zones at the beginning and end of the focusing column. After focusing in an electroosmosis-free environment (first step), mobilization (second step) can be induced electrophoretically, by the application of a hydrodynamic flow, or by a combination of both means. Dynamic simulations provide insight into the complexity of the various modes of electrophoretic mobilization and dispersion associated with hydrodynamic mobilization. The data are discussed together with the relevant literature.
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Affiliation(s)
- Wolfgang Thormann
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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3
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Fan X, Zhang X, Bao H, Zhang X, Ping J. On-chip microscale isoelectric focusing enhances protein detection limit. APPLIED PHYSICS LETTERS 2024; 124:103701. [PMID: 38449998 PMCID: PMC10914402 DOI: 10.1063/5.0190380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 02/03/2024] [Indexed: 03/08/2024]
Abstract
Enhancing the detection limit in protein analysis is essential for a wide range of biomedical applications. In typical fluorescent protein assays, this limit is constrained by the detection capacity of the photon detector. Here, we develop an approach that significantly enhances the protein detection threshold by using microscale isoelectric focusing implemented directly at the detection site on a protein sensor chip. We demonstrate that by electrically generating a localized pH environment within a radius of ∼60 μm, protein molecules can be concentrated within this range and be detected at levels over four times lower than those achieved by measurements without on-chip isoelectric focusing. We find that this detection-limit enhancement results from a dual effect: the concentrating of the protein molecules and a reduction in the diffusion-induced fluctuation. Our approach offers a simple, yet highly effective ultra-low-power all-electronic solution for substantially improving protein analysis detection limits for diverse applications, including healthcare, clinical diagnostics, and therapeutics.
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Affiliation(s)
- Xiao Fan
- Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA
| | - Xiaoyu Zhang
- Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA
| | - Huilu Bao
- Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA
| | - Xin Zhang
- Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA
| | - Jinglei Ping
- Author to whom correspondence should be addressed:
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4
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Maxted G, Estrela P, Moschou D. Employing electrochemically derived pH gradients for Lab-on-PCB protein preconcentration devices. MICROSYSTEMS & NANOENGINEERING 2024; 10:10. [PMID: 38261896 PMCID: PMC10796359 DOI: 10.1038/s41378-023-00638-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 09/22/2023] [Accepted: 10/16/2023] [Indexed: 01/25/2024]
Abstract
Protein preconcentration is an essential sample preparation step for analysis in which the targeted proteins exist in low concentrations, such as bodily fluids, water, or wastewater. Nonetheless, very few practical implementations of miniaturized protein preconcentration devices have been demonstrated in practice, and even fewer have been integrated with other microanalytical steps. Existing approaches rely heavily on additional chemicals and reagents and introduce complexity to the overall assay. In this paper, we propose a novel miniaturized isoelectric focusing-based protein preconcentration screening device based on electrochemically derived pH gradients rather than existing chemical reagent approaches. In this way, we reduce the need for additional chemical reagents to zero while enabling device incorporation in a seamlessly integrated full protein analysis microsystem via Lab-on-PCB technology. We apply our previously presented Lab-on-PCB approach to quantitatively control the pH of a solution in the vicinity of planar electrodes using electrochemical acid generation through redox-active self-assembled monolayers. The presented device comprises a printed circuit board with an array of gold electrodes that were functionalized with 4-aminothiophenol; this formed a self-assembled monolayer that was electropolymerized to improve its electrochemical reversibility. Protein preconcentration was performed in two configurations. The first was open and needed the use of a holder to suspend a well of fluid above the electrodes; the second used microfluidic channels to enclose small volumes of fluid. Reported here are the resulting data for protein preconcentration in both these forms, with a quantitative concentration factor shown for the open form and qualitative proof shown for the microfluidic.
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Affiliation(s)
- Grace Maxted
- Department of Electronic and Electrical Engineering, University of Bath, Bath, BA2 7AY UK
- Centre for Bioengineering and Biomedical Technologies (CBio), University of Bath, Bath, BA2 7AY UK
| | - Pedro Estrela
- Department of Electronic and Electrical Engineering, University of Bath, Bath, BA2 7AY UK
- Centre for Bioengineering and Biomedical Technologies (CBio), University of Bath, Bath, BA2 7AY UK
| | - Despina Moschou
- Department of Electronic and Electrical Engineering, University of Bath, Bath, BA2 7AY UK
- Centre for Bioengineering and Biomedical Technologies (CBio), University of Bath, Bath, BA2 7AY UK
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5
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Fan X, Zhang X, Ping J. Graphene-Enabled High-Performance Electrokinetic Focusing and Sensing. ACS NANO 2022; 16:10852-10858. [PMID: 35714280 DOI: 10.1021/acsnano.2c03054] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Transverse isoelectric focusing, i.e., isoelectric focusing that is normal to the fluid-flow direction, is an electrokinetic method ideal for micro total analysis. However, a major challenge remains: There is no electrode system integrable in a microfluidic device to allow reliable transverse isoelectric focusing and electrokinetic sensing. Here, we overcome this barrier by developing devices that incorporate microelectrodes made of monolayer graphene. We find that the electrolysis stability over time for graphene microelectrodes is >103× improved compared to typical microfabricated inert-metal microelectrodes. Through transverse isoelectric focusing between graphene microelectrodes, within minutes, specific proteins can be separated and concentrated to scales of ∼100 μm. Based on the concentrating effect and the high optical transparency of graphene, we develop a three-dimensional multistream microfluidic strategy for label-free detection of the proteins at same processing position with a sensitivity that is ∼102× higher than those of the state-of-the-art label-free sensors. These results demonstrate the advantage of monolayer-graphene microelectrodes for high-performance electrokinetic analysis to allow lab-on-a-chips of maximal time and size efficiencies.
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Affiliation(s)
- Xiao Fan
- Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Xiaoyu Zhang
- Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Jinglei Ping
- Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
- Institute of Applied Life Sciences, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
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6
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Thormann W, Mosher RA. Instabilities of the pH gradient in carrier ampholyte-based isoelectric focusing: Elucidation of the contributing electrokinetic processes by computer simulation. Electrophoresis 2020; 42:814-833. [PMID: 33184847 DOI: 10.1002/elps.202000269] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 10/22/2020] [Accepted: 11/05/2020] [Indexed: 11/05/2022]
Abstract
Electrokinetic processes that lead to pH gradient instabilities in carrier ampholyte-based IEF are reviewed. In addition to electroosmosis, there are four of electrophoretic nature, namely (i) the stabilizing phase with the plateau phenomenon, (ii) the gradual isotachophoretic loss of carrier ampholytes at the two column ends in presence of electrode solutions, (iii) the inequality of the mobilities of positively and negatively charged species of ampholytes, and (iv) the continuous penetration of carbonate from the catholyte into the focusing column. The impact of these factors to cathodic and anodic drifts was analyzed by simulation of carrier ampholyte-based focusing in closed and open columns. Focusing under realistic conditions within a 5 cm long capillary in which three amphoteric low molecular mass dyes were focused in a pH 3-10 gradient formed by 140 carrier ampholytes was investigated. In open columns, electroosmosis displaces the entire gradient toward the cathode or anode whereas the electrophoretic processes act bidirectionally with a transition around pH 4 (drifts for pI > 4 and pI < 4 typically toward the cathode and anode, respectively). The data illustrate that focused zones of carrier ampholytes have an electrophoretic flux and that dynamic simulation can be effectively used to assess the magnitude of each of the electrokinetic destabilizing factors and the resulting drift for a combination of these effects. Predicted drifts of focused marker dyes are compared to those observed experimentally in a setup with coated capillary and whole column optical imaging.
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Affiliation(s)
- Wolfgang Thormann
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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7
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Chau MK, Arega NG, Nhung Tran NA, Song J, Lee S, Kim J, Chung M, Kim D. Capacitively coupled contactless conductivity detection for microfluidic capillary isoelectric focusing. Anal Chim Acta 2020; 1124:60-70. [PMID: 32534676 DOI: 10.1016/j.aca.2020.05.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 03/25/2020] [Accepted: 05/09/2020] [Indexed: 12/30/2022]
Abstract
We report capacitively coupled contactless conductivity detection (C4D) of proteins separated by microfluidic capillary isoelectric focusing (μCIEF). To elucidate the evolution of negative conductivity peaks during focusing and seek IEF conditions for sensitive conductivity detection, numerical simulation was performed using a model protein GFP (green fluorescence protein) and hypothetical carrier ampholytes (CAs). C4D was successfully applied to the μCIEF by optimizing assay conditions using a simple and effective pressure-mobilization approach. The conductivity and fluorescence signals of a focused GFP band were co-detected, confirming that the obtained negative C4D peak could be attributed to the actual protein, not the non-uniform background conductivity profile of the focused CAs. GFP concentrations of 10 nM-30 μM was quantified with a detection limit of 10 nM. Finally, the resolving power was analyzed by separating a mixture of R-phycoerythrin (pI 5.01), GFP-F64L (pI 5.48), and RK-GFP (pI 6.02). The conductivities of the three separated fluorescence proteins were measured with average separation resolution of 2.06. We expect the newly developed label-free μCIEF-C4D technique to be widely adopted as a portable, electronics-only protein-analysis tool.
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Affiliation(s)
- Minh Khang Chau
- Department of Mechanical Engineering, Myongji University, Yongin-si, Gyeonggi-do, 17508, South Korea
| | - Nebiyu Getachew Arega
- Department of Mechanical Engineering, Myongji University, Yongin-si, Gyeonggi-do, 17508, South Korea
| | - Nguyen Anh Nhung Tran
- Department of Chemical Engineering, Hongik University, Mapo-gu, Seoul, 04066, South Korea
| | - Jin Song
- Department of Mechanical Engineering, Myongji University, Yongin-si, Gyeonggi-do, 17508, South Korea
| | - Sangmin Lee
- Department of Chemical Engineering, Hongik University, Mapo-gu, Seoul, 04066, South Korea
| | - Jintae Kim
- Department of Electrical Engineering, Konkuk University, Gwangjin-gu, Seoul, 05029, South Korea
| | - Minsub Chung
- Department of Chemical Engineering, Hongik University, Mapo-gu, Seoul, 04066, South Korea
| | - Dohyun Kim
- Department of Mechanical Engineering, Myongji University, Yongin-si, Gyeonggi-do, 17508, South Korea; Natural Science Research Institute, Myongji University, Yongin-si, Gyeonggi-do, 17508, South Korea.
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8
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Integrated Electrochemical Biosensors for Detection of Waterborne Pathogens in Low-Resource Settings. BIOSENSORS-BASEL 2020; 10:bios10040036. [PMID: 32294961 PMCID: PMC7236604 DOI: 10.3390/bios10040036] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 03/21/2020] [Accepted: 04/05/2020] [Indexed: 12/24/2022]
Abstract
More than 783 million people worldwide are currently without access to clean and safe water. Approximately 1 in 5 cases of mortality due to waterborne diseases involve children, and over 1.5 million cases of waterborne disease occur every year. In the developing world, this makes waterborne diseases the second highest cause of mortality. Such cases of waterborne disease are thought to be caused by poor sanitation, water infrastructure, public knowledge, and lack of suitable water monitoring systems. Conventional laboratory-based techniques are inadequate for effective on-site water quality monitoring purposes. This is due to their need for excessive equipment, operational complexity, lack of affordability, and long sample collection to data analysis times. In this review, we discuss the conventional techniques used in modern-day water quality testing. We discuss the future challenges of water quality testing in the developing world and how conventional techniques fall short of these challenges. Finally, we discuss the development of electrochemical biosensors and current research on the integration of these devices with microfluidic components to develop truly integrated, portable, simple to use and cost-effective devices for use by local environmental agencies, NGOs, and local communities in low-resource settings.
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9
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Stastna M. Continuous flow electrophoretic separation - Recent developments and applications to biological sample analysis. Electrophoresis 2019; 41:36-55. [PMID: 31650578 DOI: 10.1002/elps.201900288] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 10/08/2019] [Accepted: 10/10/2019] [Indexed: 01/23/2023]
Abstract
Continuous flow electrophoretic separation with continuous sample loading provides the advantage of processing volumes of any sizes, as well as the benefit of a real-time monitoring and optimization of the separation process. In addition, the spatial separation of the sample enables collecting multiple separated components simultaneously and in a continuous manner. The separation is usually performed in mild buffers without organic solvents and detergents (sample biological activity is retained) and it is carried out without usage of a solid support in the separation space preventing the interaction of the sample with it (high sample recovery). The method is used for the separation of proteins/peptides in proteomic applications, and its great applicability is to the separation of the cells, cellular organelles, vesicles, membrane fragments, and DNA. This review focuses on the electrophoretic separation performed in a continuous flow and it describes various electrophoretic modes and instrumental setups. Recent developments in methodology and instrumentation, the integration with other techniques, and the application to the biological sample analysis are discussed as well.
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Affiliation(s)
- Miroslava Stastna
- Institute of Analytical Chemistry of the Czech Academy of Sciences, Brno, Czech Republic
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10
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Isoelectric focusing on microfluidic paper-based chips. Anal Bioanal Chem 2019; 411:5415-5422. [DOI: 10.1007/s00216-019-02008-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 06/24/2019] [Accepted: 06/28/2019] [Indexed: 01/25/2023]
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11
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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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12
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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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13
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Sanuki R, Sueyoshi K, Endo T, Hisamoto H. Double Sweeping: Highly Effective Sample Preconcentration Using Cationic and Anionic Micelles and Its Application to a Multiple Enzyme Activity Assay. Anal Chem 2017; 89:6505-6512. [DOI: 10.1021/acs.analchem.7b00586] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ryota Sanuki
- Department of Applied
Chemistry,
Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku,
Sakai-shi, Osaka 599-8531, Japan
| | - Kenji Sueyoshi
- Department of Applied
Chemistry,
Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku,
Sakai-shi, Osaka 599-8531, Japan
| | - Tatsuro Endo
- Department of Applied
Chemistry,
Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku,
Sakai-shi, Osaka 599-8531, Japan
| | - Hideaki Hisamoto
- Department of Applied
Chemistry,
Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku,
Sakai-shi, Osaka 599-8531, Japan
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14
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FUJII Y, SUEYOSHI K, ENDO T, HISAMOTO H. A Simple and Easy-to-Use Capillary Isoelectric Focusing Technique Using Reagent-Release Hydrogels. CHROMATOGRAPHY 2017. [DOI: 10.15583/jpchrom.2017.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Yuji FUJII
- Graduate School of Engineering, Osaka Prefecture University
| | - Kenji SUEYOSHI
- Graduate School of Engineering, Osaka Prefecture University
| | - Tatsuro ENDO
- Graduate School of Engineering, Osaka Prefecture University
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15
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Sueyoshi K, Nogawa Y, Sugawara K, Endo T, Hisamoto H. Highly Sensitive and Multiple Enzyme Activity Assay Using Reagent-release Capillary-Isoelectric Focusing with Rhodamine 110-based Substrates. ANAL SCI 2016; 31:1155-61. [PMID: 26561260 DOI: 10.2116/analsci.31.1155] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In this study, a simple and highly sensitive enzyme activity assay based on reagent-release capillary-isoelectric focusing is described. Reagent-release capillaries containing a fluorescent substrate, which produces fluorescent products possessing an isoelectric point after reaction with enzymes, provides a simple procedure. This is because it allows to spontaneously inject a sample solution into the capillary by capillary action, mixing reagents, and subsequently concentrating the fluorescent products based on isoelectric focusing. Fluorescent rhodamine 110 and its monoamide derivative, which were generated as a final product and an intermediate, respectively, were then focused and separated by reagent-release capillary-isoelectric focusing. After 30 min of enzyme reactions, two focused fluorescent bands were clearly isolated along the prepared capillaries. Employing the focused band of rhodamine 110 monoamide allowed for highly sensitive detection of enzyme activity in the 10 pg mL(-1) order, while that of the conventional assay using a microplate was in the ng mL(-1) order. Furthermore, arraying reagent-release capillaries of different substrates on a chip allowed for simultaneous multi-assay of enzyme activity with good sensitivity in the pg mL(-1) order for each protein.
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Affiliation(s)
- Kenji Sueyoshi
- Graduate School of Engineering, Osaka Prefecture University
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16
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Choi H, Choi N, Lim B, Kim TW, Song S, Kim YP. Sequential phosphorylation analysis using dye-tethered peptides and microfluidic isoelectric focusing electrophoresis. Biosens Bioelectron 2015; 73:93-99. [PMID: 26050965 DOI: 10.1016/j.bios.2015.05.047] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Revised: 05/11/2015] [Accepted: 05/21/2015] [Indexed: 11/25/2022]
Abstract
We report a simple method for analyzing sequential phosphorylation by protein kinases using fluorescent peptide substrates and microfluidic isoelectric focusing (μIEF) electrophoresis. When a dye-labeled peptide substrate was sequentially phosphorylated by two consecutive protein kinases (mitogen-activated protein kinase (MAPK) and glycogen synthase kinase 3 (GSK3)), its differently phosphorylated forms were easily separated and visualized by fluorescent focusing zones in the μIEF channel based on a change in the isoelectric point (pI) by phosphorylation. As a result, ratiometric and quantitative analysis of the fluorescent focusing regions shifted by phosphorylation enabled the analysis of phosphorylation efficiency and the relevant inhibition of protein kinases (MAPK and GSK3) with high simplicity and selectivity. Furthermore, the GSK3 activity in the cell lysates was elucidated by μIEF electrophoresis in combination with immunoprecipitation. Our results suggest that this method has great potential for analyzing the sequential phosphorylation of multiple protein kinases that are implicated in cellular signaling pathways.
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Affiliation(s)
- Hoseok Choi
- Department of Life Science, Hanyang University, Seoul 133-791, Republic of Korea; Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, Republic of Korea
| | - Nakchul Choi
- Department of Mechanical Convergence Engineering, Hanyang University, Seoul 133-791, Republic of Korea
| | - Butaek Lim
- Department of Life Science, Hanyang University, Seoul 133-791, Republic of Korea; Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, Republic of Korea
| | - Tae-Wuk Kim
- Department of Life Science, Hanyang University, Seoul 133-791, Republic of Korea; Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, Republic of Korea
| | - Simon Song
- Department of Mechanical Convergence Engineering, Hanyang University, Seoul 133-791, Republic of Korea; Institute of Nano Science and Technology, Hanyang University, Seoul 133-791, Republic of Korea.
| | - Young-Pil Kim
- Department of Life Science, Hanyang University, Seoul 133-791, Republic of Korea; Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, Republic of Korea; Institute of Nano Science and Technology, Hanyang University, Seoul 133-791, Republic of Korea.
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17
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Mikkonen S, Thormann W, Emmer Å. Computer simulations of sample preconcentration in carrier-free systems and isoelectric focusing in microchannels using simple ampholytes. Electrophoresis 2015; 36:2386-95. [PMID: 26036978 DOI: 10.1002/elps.201500120] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 04/27/2015] [Accepted: 05/12/2015] [Indexed: 01/05/2023]
Abstract
In this work, electrophoretic preconcentration of protein and peptide samples in microchannels was studied theoretically using the 1D dynamic simulator GENTRANS, and experimentally combined with MS. In all configurations studied, the sample was uniformly distributed throughout the channel before power application, and driving electrodes were used as microchannel ends. In the first part, previously obtained experimental results from carrier-free systems are compared to simulation results, and the effects of atmospheric carbon dioxide and impurities in the sample solution are examined. Simulation provided insight into the dynamics of the transport of all components under the applied electric field and revealed the formation of a pure water zone in the channel center. In the second part, the use of an IEF procedure with simple well defined amphoteric carrier components, i.e. amino acids, for concentration and fractionation of peptides was investigated. By performing simulations a qualitative description of the analyte behavior in this system was obtained. Neurotensin and [Glu1]-Fibrinopeptide B were separated by IEF in microchannels featuring a liquid lid for simple sample handling and placement of the driving electrodes. Component distributions in the channel were detected using MALDI- and nano-ESI-MS and data were in agreement with those obtained by simulation. Dynamic simulations are demonstrated to represent an effective tool to investigate the electrophoretic behavior of all components in the microchannel.
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Affiliation(s)
- Saara Mikkonen
- Department of Chemistry, Analytical Chemistry, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Åsa Emmer
- Department of Chemistry, Analytical Chemistry, KTH Royal Institute of Technology, Stockholm, Sweden
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18
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Zeng H, Glawdel T, Ren CL. Microchip with an open tubular immobilized ph gradient for UV whole column imaging detection. Electrophoresis 2015; 36:2542-5. [PMID: 26101201 DOI: 10.1002/elps.201500041] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 06/09/2015] [Accepted: 06/10/2015] [Indexed: 01/06/2023]
Abstract
This study reports a new method for establishing an open tubular IPG in a microchip coupled with a whole column image detection (WCID) system for protein separation applications. This method allows a wider range of immobilized pH (2.6-9.5) to be established in a PDMS/quartz channel by controlling the diffusion of acidic and basic polymer solutions into the channel through well-designed channel dimensions. The developed pH gradient was experimentally validated by performing the separation of a mixture of standard pI markers. It was further validated by the separation of the hemoglobin control AFSC sample. This method is advantageous over existing IPG methods because it has a wider range of pH and maintains the open tubular feature that matches the UV WCID to improve the sensitivity.
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Affiliation(s)
- Hulie Zeng
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada
| | - Tomasz Glawdel
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada
| | - Carolyn L Ren
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada
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19
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Lilienthal S, Drotleff AM, Ternes W. Changes in the protein secondary structure of hen's egg yolk determined by Fourier transform infrared spectroscopy during the first eight days of incubation. Poult Sci 2015; 94:68-79. [DOI: 10.3382/ps/peu051] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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20
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Xia L, Lin F, Wu X, Liu C, Wang J, Tang Q, Yu S, Huang K, Deng Y, Geng L. On-chip protein isoelectric focusing using a photoimmobilized pH gradient†. J Sep Sci 2014; 37:3174-80. [DOI: 10.1002/jssc.201400795] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 07/23/2014] [Accepted: 08/02/2014] [Indexed: 02/01/2023]
Affiliation(s)
- Lin Xia
- School of Life Science; Beijing Institute of Technology; Beijing P. R. China
| | - FengMing Lin
- School of Life Science; Beijing Institute of Technology; Beijing P. R. China
| | - Xin Wu
- School of Life Science; Beijing Institute of Technology; Beijing P. R. China
| | - Chuanli Liu
- School of Life Science; Beijing Institute of Technology; Beijing P. R. China
| | - Jianshe Wang
- School of Life Science; Beijing Institute of Technology; Beijing P. R. China
| | - Qi Tang
- School of Life Science; Beijing Institute of Technology; Beijing P. R. China
| | - Shiyong Yu
- School of Life Science; Beijing Institute of Technology; Beijing P. R. China
| | - Kunjie Huang
- School of Life Science; Beijing Institute of Technology; Beijing P. R. China
| | - Yulin Deng
- School of Life Science; Beijing Institute of Technology; Beijing P. R. China
| | - Lina Geng
- School of Life Science; Beijing Institute of Technology; Beijing P. R. China
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21
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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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22
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Hsu WL, Inglis DW, Startsev MA, Goldys EM, Davidson MR, Harvie DJE. Isoelectric focusing in a silica nanofluidic channel: effects of electromigration and electroosmosis. Anal Chem 2014; 86:8711-8. [PMID: 25098739 DOI: 10.1021/ac501875u] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Isoelectric focusing of proteins in a silica nanofluidic channel filled with citric acid and disodium phosphate buffers is investigated via numerical simulation. Ions in the channel migrate in response to (i) the electric field acting on their charge and (ii) the bulk electroosmotic flow (which is directed toward the cathode). Proteins are focused near the low pH (anode) end when the electromigration effect is more significant and closer to the high pH (cathode) end when the electroosmotic effect dominates. We simulate the focusing behavior of Dylight labeled streptavidin (Dyl-Strep) proteins in the channel, using a relationship between the protein's charge and pH measured in a previous experiment. Protein focusing results compare well to previous experimental measurements. The effect of some key parameters, such as applied voltage, isoelectric point (pI), bulk pH, and bulk conductivity, on the protein trapping behavior in a nanofluidic channel is examined.
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Affiliation(s)
- Wei-Lun Hsu
- Department of Chemical and Biomolecular Engineering, University of Melbourne , Parkville, Victoria 3010, Australia
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23
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Wang S, Chen S, Wang J, Xu P, Luo Y, Nie Z, Du W. Interface solution isoelectric focusing with in situ MALDI-TOF mass spectrometry. Electrophoresis 2014; 35:2528-33. [DOI: 10.1002/elps.201400083] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 04/19/2014] [Accepted: 04/21/2014] [Indexed: 01/03/2023]
Affiliation(s)
- Shujun Wang
- Department of Chemistry; Renmin University of China; Beijing China
- State Key Laboratory of Microbial Resources; Institute of Microbiology; Chinese Academy of Sciences; Beijing China
| | - Suming Chen
- Beijing National Laboratory for Molecular Sciences; Key Laboratory of Analytical Chemistry for Living Biosystems; Institute of Chemistry; Chinese Academy of Sciences; Beijing China
| | - Jianing Wang
- Beijing National Laboratory for Molecular Sciences; Key Laboratory of Analytical Chemistry for Living Biosystems; Institute of Chemistry; Chinese Academy of Sciences; Beijing China
| | - Peng Xu
- State Key Laboratory of Microbial Resources; Institute of Microbiology; Chinese Academy of Sciences; Beijing China
| | - Yuanming Luo
- State Key Laboratory of Microbial Resources; Institute of Microbiology; Chinese Academy of Sciences; Beijing China
| | - Zongxiu Nie
- Beijing National Laboratory for Molecular Sciences; Key Laboratory of Analytical Chemistry for Living Biosystems; Institute of Chemistry; Chinese Academy of Sciences; Beijing China
| | - Wenbin Du
- State Key Laboratory of Microbial Resources; Institute of Microbiology; Chinese Academy of Sciences; Beijing China
- Department of Chemistry; Renmin University of China; Beijing China
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24
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Schoonen JW, van Duinen V, Oedit A, Vulto P, Hankemeier T, Lindenburg PW. Continuous-flow microelectroextraction for enrichment of low abundant compounds. Anal Chem 2014; 86:8048-56. [PMID: 24892382 DOI: 10.1021/ac500707v] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We present a continuous-flow microelectroextraction flow cell that allows for electric field enhanced extraction of analytes from a large volume (1 mL) of continuously flowing donor phase into a micro volume of stagnant acceptor phase (13.4 μL). We demonstrate for the first time that the interface between the stagnant acceptor phase and fast-flowing donor phase can be stabilized by a phaseguide. Chip performance was assessed by visual experiments using crystal violet. Then, extraction of a mixture of acylcarnitines was assessed by off-line coupling to reversed phase liquid chromatography coupled to time-of-flight mass spectrometry, resulting in concentration factors of 80.0 ± 9.2 times for hexanoylcarnitine, 73.8 ± 9.1 for octanoylcarnitine, and 34.1 ± 4.7 times for lauroylcarnitine, corresponding to recoveries of 107.8 ± 12.3%, 98.9 ± 12.3%, and 45.7 ± 6.3%, respectively, in a sample of 500 μL delivered at a flow of 50 μL min(-1) under an extraction voltage of 300 V. Finally, the method was applied to the analysis of acylcarnitines spiked to urine, resulting in detection limits as low as 0.3-2 nM. Several putative endogenous acylcarnitines were found. The current flowing-to-stagnant phase microelectroextraction setup allows for the extraction of milliliter range volumes and is, as a consequence, very suited for analysis of low-abundant metabolites.
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Affiliation(s)
- Jan-Willem Schoonen
- Division of Analytical Biosciences, Leiden Academic Center for Drug Research, Leiden University , Leiden, The Netherlands
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25
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Sikorsky AA, Fourkas JT, Ross D. Gradient Elution Moving Boundary Electrophoresis with Field-Amplified Continuous Sample Injection. Anal Chem 2014; 86:3625-32. [DOI: 10.1021/ac500242a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alison A. Sikorsky
- Department
of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
- Material
Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20878, United States
| | - John T. Fourkas
- Department
of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
- Institute for Physical
Science and Technology, Maryland NanoCenter, and Center for Nanophysics
and Advanced Materials, University of Maryland, College Park, Maryland 20742, United States
| | - David Ross
- Material
Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20878, United States
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26
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Zhao Y, Pereira F, deMello AJ, Morgan H, Niu X. Droplet-based in situ compartmentalization of chemically separated components after isoelectric focusing in a Slipchip. LAB ON A CHIP 2014; 14:555-561. [PMID: 24292781 DOI: 10.1039/c3lc51067k] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Isoelectric focusing (IEF) is a powerful and widely used technique for protein separation and purification. There are many embodiments of microscale IEF that use capillary or microfluidic chips for the analysis of small sample volumes. Nevertheless, collecting the separated sample volumes without causing remixing remains a challenge. Herein, we describe a microfluidic Slipchip device that is able to efficiently compartmentalize focused analyte bands in situ into microdroplets. The device contains a microfluidic "zig-zag" separation channel that is composed of a sequence of wells formed in the two halves of the Slipchip. The analytes are focused in the channel and then compartmentalised into droplets by slipping the chip. Importantly, sample droplets can be analysed on chip or collected for subsequent analysis using electrophoresis or mass spectrometry for example. To demonstrate this approach, we perform IEF separation using standard markers and protein samples, with on-chip post-processing. Compared to alternative approaches for sample collection, the method avoids remixing, is scalable and is easily hyphenated with the other analytical methods.
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Affiliation(s)
- Yan Zhao
- Faculty of Physical Sciences and Engineering, and Institute for Life Sciences, University of Southampton, Highfield, Southampton, SO17 1BJ, UK.
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27
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Kim D, Herr AE. Protein immobilization techniques for microfluidic assays. BIOMICROFLUIDICS 2013; 7:41501. [PMID: 24003344 PMCID: PMC3747845 DOI: 10.1063/1.4816934] [Citation(s) in RCA: 218] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2013] [Accepted: 07/16/2013] [Indexed: 05/07/2023]
Abstract
Microfluidic systems have shown unequivocal performance improvements over conventional bench-top assays across a range of performance metrics. For example, specific advances have been made in reagent consumption, throughput, integration of multiple assay steps, assay automation, and multiplexing capability. For heterogeneous systems, controlled immobilization of reactants is essential for reliable, sensitive detection of analytes. In most cases, protein immobilization densities are maximized, while native activity and conformation are maintained. Immobilization methods and chemistries vary significantly depending on immobilization surface, protein properties, and specific assay goals. In this review, we present trade-offs considerations for common immobilization surface materials. We overview immobilization methods and chemistries, and discuss studies exemplar of key approaches-here with a specific emphasis on immunoassays and enzymatic reactors. Recent "smart immobilization" methods including the use of light, electrochemical, thermal, and chemical stimuli to attach and detach proteins on demand with precise spatial control are highlighted. Spatially encoded protein immobilization using DNA hybridization for multiplexed assays and reversible protein immobilization surfaces for repeatable assay are introduced as immobilization methods. We also describe multifunctional surface coatings that can perform tasks that were, until recently, relegated to multiple functional coatings. We consider the microfluidics literature from 1997 to present and close with a perspective on future approaches to protein immobilization.
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Affiliation(s)
- Dohyun Kim
- Department of Mechanical Engineering, Myongji University, 116 Myongji-ro, Cheoin-gu, Yongin-si, Gyeonggi-do 449-728, South Korea
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28
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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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29
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Mikkonen S, Rokhas MK, Jacksén J, Emmer A. Sample preconcentration in open microchannels combined with MALDI-MS. Electrophoresis 2012; 33:3343-50. [PMID: 23086729 DOI: 10.1002/elps.201200129] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Revised: 06/10/2012] [Accepted: 06/26/2012] [Indexed: 01/22/2023]
Abstract
In this work, a method for preconcentrating samples in 1 cm long, 50-150 μm wide open microchannels is presented. Platinum electrodes were positioned at the channel ends, voltage was applied, and charged analyte was preconcentrated at the oppositely charged side during continuous supply of sample. The preconcentration was initially studied in a closed system, where an influence on the analyte position from a pH gradient, generated by water electrolysis, was observed. In the open channel, the analyte distribution after preconcentration was evaluated using MALDI-MS with the channel as MALDI target. MALDI matrix was applied with an airbrush or by electrospray matrix deposition and by using the latter technique higher degrees of crystallization in the channels were obtained. After preconcentrating a 1 nM cytochrome c solution for 5 min, corresponding to a supplied amount of 1.25 fmol, a signal on the cathodic channel end could be detected. When a solution of cytochrome c trypsin digest was supplied, the peptides were preconcentrated at different positions along the channel depending on their charge.
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Affiliation(s)
- Saara Mikkonen
- Analytical Chemistry, Division of Applied Physical Chemistry, Department of Chemistry, School of Chemical Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden
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30
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Zhao SS, Zhong X, Tie C, Chen DD. Capillary electrophoresis-mass spectrometry for analysis of complex samples. Proteomics 2012; 12:2991-3012. [DOI: 10.1002/pmic.201200221] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Revised: 07/10/2012] [Accepted: 07/18/2012] [Indexed: 12/20/2022]
Affiliation(s)
- Shuai Sherry Zhao
- Department of Chemistry; University of British Columbia; Vancouver BC Canada
| | - Xuefei Zhong
- Department of Chemistry; University of British Columbia; Vancouver BC Canada
| | - Cai Tie
- Department of Chemistry; University of British Columbia; Vancouver BC Canada
| | - David D.Y. Chen
- Department of Chemistry; University of British Columbia; Vancouver BC Canada
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31
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Mai J, Sommer GJ, Hatch AV. Microfluidic digital isoelectric fractionation for rapid multidimensional glycoprotein analysis. Anal Chem 2012; 84:3538-45. [PMID: 22409593 DOI: 10.1021/ac203076p] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Here we present an integrated microfluidic device for rapid and automated isolation and quantification of glycoprotein biomarkers directly from biological samples on a multidimensional analysis platform. In the first dimension, digital isoelectric fractionation (dIEF) uses discrete pH-specific membranes to separate proteins and their isoforms into precise bins in a highly flexible spatial arrangement on-chip. dIEF provides high sample preconcentration factors followed by immediate high-fidelity transfer of fractions for downstream analysis. We successfully fractionate isoforms of two potential glycoprotein cancer markers, fetuin and prostate-specific antigen (PSA), with 10 min run time, and results are compared qualitatively and quantitatively to conventional slab gel IEF. In the second dimension, functionalized monolithic columns are used to capture and detect targeted analytes from each fraction. We demonstrate rapid two-dimensional fractionation, immunocapture, and detection of C-reactive protein (CRP) spiked in human serum. This rapid, flexible, and automated approach is well-suited for glycoprotein biomarker research and verification studies and represents a practical avenue for glycoprotein isoform-based diagnostic testing.
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Affiliation(s)
- Junyu Mai
- Department of Biotechnology and Bioengineering, Sandia National Laboratories, Livermore, California 94551, United States
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32
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Morales MC, Lin H, Zahn JD. Continuous microfluidic DNA and protein trapping and concentration by balancing transverse electrokinetic forces. LAB ON A CHIP 2012; 12:99-108. [PMID: 22045330 DOI: 10.1039/c1lc20605b] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Sample pre-concentration can be a critical element to improve sensitivity of integrated microchip assays. In this work a converging Y-inlet microfluidic channel with integrated coplanar electrodes was used to investigate transverse DNA and protein migration under uniform direct current (DC) electric fields to assess the ability to concentrate a sample prior to other enzymatic modifications or capillary electrophoretic separations. Employing a pressure-driven flow to perfuse the microchannel, negatively charged samples diluted in low and high ionic strength buffers were co-infused with a receiving buffer of the same ionic strength into a main daughter channel. Experimental results demonstrated that, depending of the buffer selection, different DNA migration and accumulation dynamics were seen. Charged analytes could traverse the channel width and accumulate at the positive bias electrode in a low electroosmotic mobility, high electrophoretic mobility, high ionic strength buffer or migrated towards an equilibrium position within the channel in a high electroosmotic mobility, high electrophoretic mobility, low ionic strength buffer. The various migration behaviours are the result of a balance between the electrophoretic force and a drag force induced by a recirculating electroosmotic flow generated across the channel width due to the bounding walls. Under continuous flow conditions, DNA samples were concentrated several-fold by balancing these transverse electrokinetic forces. The electrokinetic trapping technique presented here is a simple technique which could be expanded to concentrate or separate other analytes as a preconditioning step for downstream processes.
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Affiliation(s)
- Mercedes C Morales
- BioMEMS Laboratory, Department of Biomedical Engineering, Rutgers, The State University of New Jersey, 599 Taylor Road, Piscataway, New Jersey 08854, USA
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33
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Gencoglu A, Camacho-Alanis F, Nguyen VT, Nakano A, Ros A, Minerick A. Quantification of pH gradients and implications in insulator-based dielectrophoresis of biomolecules. Electrophoresis 2011; 32:2436-47. [PMID: 21874654 PMCID: PMC3226333 DOI: 10.1002/elps.201100090] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2011] [Revised: 05/04/2011] [Accepted: 05/05/2011] [Indexed: 11/08/2022]
Abstract
Direct current (DC) insulator-based dielectrophoretic (iDEP) microdevices have the potential to replace traditional alternating current dielectrophoretic devices for many cellular and biomolecular separation applications. The use of large DC fields suggest that electrode reactions and ion transport mechanisms can become important and impact ion distributions in the nanoliters of fluid in iDEP microchannels. This work tracked natural pH gradient formation in a 100 μm wide, 1 cm-long microchannel under applicable iDEP protein manipulation conditions. Using fluorescence microscopy with the pH-sensitive dye FITC Isomer I and the pH-insensitive dye TRITC as a reference, pH was observed to drop drastically in the microchannels within 1 min in a 3000 V/cm electric field; pH drops were observed in the range of 6-10 min within a 100 V/cm electric field and varied based on the buffer conductivity. To address concerns of dye transport impacting intensity data, electrokinetic mobilities of FITC were carefully examined and found to be (i) toward the anode and (ii) 1 to 2 orders of magnitude smaller than H⁺ transport which is responsible for pH drops from the anode toward the cathode. COMSOL simulations of ion transport showed qualitative agreement with experimental results. The results indicate that pH changes are severe enough and rapid enough to influence the net charge of a protein or cause aggregation during iDEP experiments. The results also elucidate reasonable time periods over which the phosphate buffering capacity can counter increases in H⁺ and OH⁻ for unperturbed iDEP manipulations.
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Affiliation(s)
- Aytug Gencoglu
- : Department of Chemical Engineering, Michigan Technological University, Houghton, MI 49931, USA
| | - Fernanda Camacho-Alanis
- : Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA
| | - Vi Thanh Nguyen
- : Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA
| | - Asuka Nakano
- : Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA
| | - Alexandra Ros
- : Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA
| | - Adrienne Minerick
- : Department of Chemical Engineering, Michigan Technological University, Houghton, MI 49931, USA
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34
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Yamamoto S, Watanabe Y, Nishida N, Suzuki S. Simultaneous concentration enrichment and electrophoretic separation of weak acids on a microchip, using in situ
photopolymerized carboxylate-type polyacrylamide gels as the permselective preconcentrator. J Sep Sci 2011; 34:2879-84. [DOI: 10.1002/jssc.201100423] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Revised: 06/17/2011] [Accepted: 06/21/2011] [Indexed: 12/24/2022]
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35
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Sommer GJ, Mai J, Singh AK, Hatch AV. Microscale isoelectric fractionation using photopolymerized membranes. Anal Chem 2011; 83:3120-5. [PMID: 21417312 DOI: 10.1021/ac200073p] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In this work, we introduce microscale isoelectric fractionation (μIF) for isolation and enrichment of molecular species at any desired location in a microfluidic chip. Narrow pH-specific polyacrylamide membranes are photopatterned in situ for customizable device fabrication; multiple membranes of precise pH are easily incorporated throughout existing channel layouts. Samples are electrophoretically driven across the membranes such that charged species, for example, proteins and peptides, are rapidly discretized into fractions based on their isoelectric points (pI) without the use of carrier ampholytes. This format makes fractions easy to compartmentalize and access for integrated preparative or analytical operations on-chip. We present and discuss the key design considerations and trade-offs associated with proper system operation and optimal run conditions. Efficient and reproducible fractionation of model fluorescent pI markers and proteins is achieved using single membrane fractionators at pH 6.5 and 5.3 from both buffer and Escherichia coli cell lysate sample conditions. Effective fractionation is also shown using a serial 3-membrane fractionator tailored for isolating analytes-of-interest from high abundance components of serum. We further demonstrate that proteins focused in pH specific bins can be rapidly and efficiently transferred to another location in the same chip without unwanted dilution or dispersive effects. μIF provides a rapid and versatile option for integrated sample prep or multidimensional analysis, and addresses the glaring proteomic need to isolate trace analytes from high-abundance species in minute volumes of complex samples.
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Affiliation(s)
- Greg J Sommer
- Biotechnology and Bioengineering Department, Sandia National Laboratories, Livermore, California 94550, USA.
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Shameli SM, Elbuken C, Ou J, Ren CL, Pawliszyn J. Fully integrated PDMS/SU-8/quartz microfluidic chip with a novel macroporous poly dimethylsiloxane (PDMS) membrane for isoelectric focusing of proteins using whole-channel imaging detection. Electrophoresis 2010; 32:333-9. [PMID: 21298660 DOI: 10.1002/elps.201000643] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Revised: 12/03/2010] [Accepted: 12/09/2010] [Indexed: 01/02/2023]
Abstract
A fully integrated polydimethylsiloxane (PDMS)/modified PDMS membrane/SU-8/quartz hybrid chip was developed for protein separation using isoelectric focusing (IEF) mechanism coupled with whole-channel imaging detection (WCID) method. This microfluidic chip integrates three components into one single chip: (i) modified PDMS membranes for separating electrolytes in the reservoirs from the sample in the microchannel and thus reducing pressure disturbance, (ii) SU-8 optical slit to block UV light (below 300 nm) outside the channel aiming to increase detection sensitivity, and (iii) injection and discharge capillaries for continuous operation. Integration of all these components on a single chip is challenging because it requires fabrication techniques for perfect bonding between different materials and is prone to leakage and blockage. This study has addressed all the challenges and presented a fully integrated chip, which is more robust with higher sensitivity than the previously developed IEF chips. This chip was tested by performing protein and pI marker separation. The separation results obtained in this chip were compared with that obtained in commercial cartridges. Side-by-side comparison validated the developed chip and fabrication techniques.
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Affiliation(s)
- Seyed Mostafa Shameli
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada
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Köster J, Hayen H, von Wirén N, Weber G. Isoelectric focusing of small non-covalent metal species from plants. Electrophoresis 2010; 32:772-81. [PMID: 21192102 DOI: 10.1002/elps.201000529] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Revised: 11/08/2010] [Accepted: 11/09/2010] [Indexed: 12/12/2022]
Abstract
IEF is known as a powerful electrophoretic separation technique for amphoteric molecules, in particular for proteins. The objective of the present work is to prove the suitability of IEF also for the separation of small, non-covalent metal species. Investigations are performed with copper-glutathione complexes, with the synthetic ligand ethylenediamine-N,N'-bis(o-hydroxyphenyl)acetic acid (EDDHA) and respective metal complexes (Fe, Ga, Al, Ni, Zn), and with the phytosiderophore 2'-deoxymugineic acid (DMA) and its ferric complex. It is shown that ethylenediamine-N,N'-bis(o-hydroxyphenyl)acetic acid and DMA species are stable during preparative scale IEF, whereas copper-glutathione dissociates considerably. It is also shown that preparative scale IEF can be applied successfully to isolate ferric DMA from real plant samples, and that multidimensional separations are possible by combining preparative scale IEF with subsequent HPLC-MS analysis. Focusing of free ligands and respective metal complexes with di- and trivalent metals results in different pIs, but CIEF is usually needed for a reliable estimation of pI values. Limitations of the proposed methods (preparative IEF and CIEF) and consequences of the results with respect to metal speciation in plants are discussed.
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Affiliation(s)
- Jessica Köster
- Leibniz-Institut für Analytische Wissenschaften, ISAS, Dortmund, Germany
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Xu Z, Okabe N, Arai A, Hirokawa T. Investigation of the pH gradient formation and cathodic drift in microchip isoelectric focusing with imaged UV detection. Electrophoresis 2010; 31:3558-65. [DOI: 10.1002/elps.201000395] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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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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Tran NT, Ayed I, Pallandre A, Taverna M. Recent innovations in protein separation on microchips by electrophoretic methods: An update. Electrophoresis 2010; 31:147-73. [DOI: 10.1002/elps.200900465] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Laws DR, Hlushkou D, Perdue RK, Tallarek U, Crooks RM. Bipolar Electrode Focusing: Simultaneous Concentration Enrichment and Separation in a Microfluidic Channel Containing a Bipolar Electrode. Anal Chem 2009; 81:8923-9. [DOI: 10.1021/ac901545y] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Derek R. Laws
- Department of Chemistry and Biochemistry and Center for Electrochemistry, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, and Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032 Marburg, Germany
| | - Dzmitry Hlushkou
- Department of Chemistry and Biochemistry and Center for Electrochemistry, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, and Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032 Marburg, Germany
| | - Robbyn K. Perdue
- Department of Chemistry and Biochemistry and Center for Electrochemistry, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, and Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032 Marburg, Germany
| | - Ulrich Tallarek
- Department of Chemistry and Biochemistry and Center for Electrochemistry, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, and Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032 Marburg, Germany
| | - Richard M. Crooks
- Department of Chemistry and Biochemistry and Center for Electrochemistry, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, and Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032 Marburg, Germany
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