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Qiu W, Lin X, Nagl S. In Situ Live Monitoring of Extracellular Acidosis near Cancer Cells Using Digital Microfluidics with an Integrated Optical pH Sensor Film. Anal Chem 2024. [PMID: 39171737 DOI: 10.1021/acs.analchem.4c02319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2024]
Abstract
We demonstrate the live monitoring of extracellular acidification on digital microfluidics using a chip-integrated fluorescent pH sensor film. The metabolism of various types of live cells including cancer and healthy cells were investigated through recording the extracellular pH (pHe) change. An optical pH sensor array was integrated onto a digital microfluidic (DMF) interface with a diameter of 2 mm per pH-sensing spot. Miniaturized, label-free, and noninvasive monitoring of extracellular acidosis on DMF was realized within a pH range of 5.0-8.0 with good sensitivity and rapid response. The pH sensitive probe fluorescein-5-isothiocyanate was covalently bound to poly-2-hydroxyethyl methacrylate and immobilized on a circularly exposed indium tin oxide interface on the DMF top plate. The surface of the fabricated pH sensor spots was modified with polydopamine via self-polymerization. Direct cell attachment on the sensor surfaces enabled rapid pH detection near the cell membranes. Automatic medium exchange on cell-attached pH sensing sites was achieved though solution passive dispensing on DMF. The developed DMF platform was used to monitor the pHe decrease during MCF-7 and A549 cancer cell proliferation due to abnormal glycolysis metabolism. A rapid pH decrease at the pH sensing area in the presence of cancer cells could be detected within 2 min after fresh medium exchange, while no obvious pHe change was observed with HUVEC healthy cells. Real-time detection of cell acidification and cellular response to different metabolic conditions such as higher glucose levels or administered anticancer drugs was possible.
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Affiliation(s)
- Wenting Qiu
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR 999077, China
| | - Xuyan Lin
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR 999077, China
| | - Stefan Nagl
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR 999077, China
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2
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Suarez GD, Bayer S, Tang YYK, Suarez DA, Cheung PPH, Nagl S. Rapid microfluidics prototyping through variotherm desktop injection molding for multiplex diagnostics. LAB ON A CHIP 2023; 23:3850-3861. [PMID: 37534874 DOI: 10.1039/d3lc00391d] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/04/2023]
Abstract
In this work, we demonstrate an inexpensive method of prototyping microfluidics using a desktop injection molding machine. A centrifugal microfluidic device with a novel central filling mechanism was developed to demonstrate the technique. We overcame the limitations of desktop machines in replicating microfluidic features by variotherm heating and cooling the mold between 50 °C and 110 °C within two minutes. Variotherm heating enabled good replication of microfeatures, with a coefficient of variation averaging only 3.6% attained for the measured widths of 100 μm wide molded channels. Using this methodology, we produced functional polystyrene centrifugal microfluidic chips, capable of aliquoting fluids into 5.0 μL reaction chambers with 97.5% accuracy. We performed allele-specific loop-mediated isothermal amplification (AS-LAMP) reactions for genotyping CYP2C19 alleles on these chips. Readouts were generated using optical pH sensors integrated onto chips, by drop-casting sensor precursor solutions into reaction chambers before final chip assembly. Positive reactions could be discerned by decreases in pH sensor fluorescence, thresholded against negative control reactions lacking the primers for nucleic acid amplification and with time-to-results averaging 38 minutes. Variotherm desktop injection molding can enable researchers to prototype microfluidic devices more cost-effectively, in an iterative fashion, due to reduced costs of smaller, in-house molds. Designs prototyped this way can be directly translated to mass production, enhancing their commercialization potential and positive impacts.
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Affiliation(s)
- Gianmarco D Suarez
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| | - Steevanson Bayer
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
| | - Yuki Yu Kiu Tang
- Quommni Technologies Limited, Tsuen Wan, New Territories, Hong Kong
| | | | - Peter Pak-Hang Cheung
- Department of Chemical Pathology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong.
| | - Stefan Nagl
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
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3
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Sharma H, Yadav V, D'Souza-Schorey C, Go DB, Senapati S, Chang HC. A Scalable High-Throughput Isoelectric Fractionation Platform for Extracellular Nanocarriers: Comprehensive and Bias-Free Isolation of Ribonucleoproteins from Plasma, Urine, and Saliva. ACS NANO 2023; 17:9388-9404. [PMID: 37071723 PMCID: PMC10756736 DOI: 10.1021/acsnano.3c01340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Extracellular nanocarriers (extracellular vesicles (EVs), lipoproteins, and ribonucleoproteins) of protein and nucleic acids mediate intercellular communication and are clinically adaptable as distinct circulating biomarkers. However, the overlapping size and density of the nanocarriers have so far prevented their efficient physical fractionation, thus impeding independent downstream molecular assays. Here, we report a bias-free high-throughput and high-yield continuous isoelectric fractionation nanocarrier fractionation technique based on their distinct isoelectric points. This nanocarrier fractionation platform is enabled by a robust and tunable linear pH profile provided by water-splitting at a bipolar membrane and stabilized by flow without ampholytes. The linear pH profile that allows easy tuning is a result of rapid equilibration of the water dissociation reaction and stabilization by flow. The platform is automated with a machine learning procedure to allow recalibration for different physiological fluids and nanocarriers. The optimized technique has a resolution of 0.3 ΔpI, sufficient to separate all nanocarriers and even subclasses of nanocarriers. Its performance is then evaluated with several biofluids, including plasma, urine, and saliva samples. Comprehensive, high-purity (plasma: >93%, urine: >95% and saliva: >97%), high-yield (plasma: >78%, urine: >87% and saliva: >96%), and probe-free isolation of ribonucleoproteins in 0.75 mL samples of various biofluids in 30 min is demonstrated, significantly outperforming affinity-based and highly biased gold standards having low yield and day-long protocols. Binary fractionation of EVs and different lipoproteins is also achieved with similar performance.
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Affiliation(s)
- Himani Sharma
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Vivek Yadav
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Crislyn D'Souza-Schorey
- Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana 46556, United States
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - David B Go
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Satyajyoti Senapati
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Hsueh-Chia Chang
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
- Harper Cancer Research Institute, University of Notre Dame, Notre Dame, Indiana 46556, United States
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4
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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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5
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Reciprocating free-flow isoelectric focusing with online array ultraviolet detector for process monitoring of protein separation. J Chromatogr A 2022; 1663:462747. [PMID: 34973480 DOI: 10.1016/j.chroma.2021.462747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 12/06/2021] [Accepted: 12/11/2021] [Indexed: 11/22/2022]
Abstract
Free-flow isoelectric focusing (FFIEF) is a useful tool for separating and purifying proteins, DNA, cells, and organelles, etc. However, the online monitoring of each fraction during an FFIEF run has not been achieved yet, resulting in a lack of process monitoring of FFIEF. Herein, an online array ultraviolet (UV) detection system was developed for the easy assay of FFE fractions. The detector was integrated with an apparatus of FFIEF with 32 fractions to show the online monitoring, and bovine serum albumin (BSA) and lysozyme were chosen as the model proteins for manifesting the UV detector performance. The experiments revealed that (i) all the fluidic cells had good linearity from 0.03 to 10 mg/mL BSA and fair limits of detection (LODs) of 0.01 mg/mL; (ii) all the cells had good uniformity of UV absorbance; and (iii) the deviations of intra-day and inter-day of UV detector were respectively 3.8% and 5.8%, indicating the fair stability of the UV detector. The UV detector could be well used for the process monitoring of two model proteins through the whole FFIEF run, and the online absorbance assay of proteins at the end of FFIEF. The UV detector herein had the evident potential for rapid and convenient assay of protein fraction in FFIEF as well as other FFE modes.
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Wolfbeis OS. Fluorescent chameleon labels for bioconjugation and imaging of proteins, nucleic acids, biogenic amines and surface amino groups. a review. Methods Appl Fluoresc 2021; 9. [PMID: 34340216 DOI: 10.1088/2050-6120/ac1a0a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 08/02/2021] [Indexed: 12/14/2022]
Abstract
Chameleon labels (ChLs) possess the unique property of changing (visible) color and fluorescence on binding to amino groups of biomolecules. MostChLs react with primary aliphatic amino groups such as those in lysine or with amino groups artificially introduced into polynucleic acids or saccharides, but someothers also react with secondary amino groups. Under controlled circumstances, the reactions are fairly specific. The review is subdivided into the following sections: (1) An introduction and classification of fluorescent labels; (2) pyrylium labels that undergo shortwave color changes upon labelling, typically from blue to red; (3) polymethine type of labels (that also undergo shortwave color changes, typically from green to blue; (4) various other (less common) chromogenic and fluorogenic systems; (5) hemicyanine labels that undergolongwavecolor changes, typically from yellow to purple; (6) the application of ChLs to labeling of proteins and oligonucleotides; (7) applications to fluorometric assays and sensing; (8) applications to fluorescence imaging of biomolecules; (9) applications in studies on affinity interactions (receptor-ligand binding); (10) applications in surface and interface chemistry; and (11) applications in chromatography, electrophoresis and isotachophoresis of biomolecules.
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Affiliation(s)
- Otto S Wolfbeis
- University of Regensburg, Institute of Analytical Chemistry, Chemo- and Biosensors, 94040 Regensburg, Germany
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7
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Steinegger A, Wolfbeis OS, Borisov SM. Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications. Chem Rev 2020; 120:12357-12489. [PMID: 33147405 PMCID: PMC7705895 DOI: 10.1021/acs.chemrev.0c00451] [Citation(s) in RCA: 181] [Impact Index Per Article: 45.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Indexed: 12/13/2022]
Abstract
This is the first comprehensive review on methods and materials for use in optical sensing of pH values and on applications of such sensors. The Review starts with an introduction that contains subsections on the definition of the pH value, a brief look back on optical methods for sensing of pH, on the effects of ionic strength on pH values and pKa values, on the selectivity, sensitivity, precision, dynamic ranges, and temperature dependence of such sensors. Commonly used optical sensing schemes are covered in a next main chapter, with subsections on methods based on absorptiometry, reflectometry, luminescence, refractive index, surface plasmon resonance, photonic crystals, turbidity, mechanical displacement, interferometry, and solvatochromism. This is followed by sections on absorptiometric and luminescent molecular probes for use pH in sensors. Further large sections cover polymeric hosts and supports, and methods for immobilization of indicator dyes. Further and more specific sections summarize the state of the art in materials with dual functionality (indicator and host), nanomaterials, sensors based on upconversion and 2-photon absorption, multiparameter sensors, imaging, and sensors for extreme pH values. A chapter on the many sensing formats has subsections on planar, fiber optic, evanescent wave, refractive index, surface plasmon resonance and holography based sensor designs, and on distributed sensing. Another section summarizes selected applications in areas, such as medicine, biology, oceanography, bioprocess monitoring, corrosion studies, on the use of pH sensors as transducers in biosensors and chemical sensors, and their integration into flow-injection analyzers, microfluidic devices, and lab-on-a-chip systems. An extra section is devoted to current challenges, with subsections on challenges of general nature and those of specific nature. A concluding section gives an outlook on potential future trends and perspectives.
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Affiliation(s)
- Andreas Steinegger
- Institute
of Analytical Chemistry and Food Chemistry, Graz University of Technology, Stremayrgasse 9, A-8010 Graz, Austria
| | - Otto S. Wolfbeis
- Institute
of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, D-93040 Regensburg, Germany
| | - Sergey M. Borisov
- Institute
of Analytical Chemistry and Food Chemistry, Graz University of Technology, Stremayrgasse 9, A-8010 Graz, Austria
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8
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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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9
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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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10
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Isoelectric focusing array with immobilized pH gradient and dynamic scanning imaging for diabetes diagnosis. Anal Chim Acta 2019; 1063:178-186. [DOI: 10.1016/j.aca.2019.03.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 03/02/2019] [Accepted: 03/07/2019] [Indexed: 12/24/2022]
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11
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Ren G, Zhang BY, Yao Q, Zavabeti A, Huertas CS, Brkljača R, Khan MW, Nili H, Datta RS, Khan H, Jannat A, Walia S, Haque F, O'Dell LA, Wang Y, Zhu L, Mitchell A, Ou JZ. An Ultrasensitive Silicon Photonic Ion Sensor Enabled by 2D Plasmonic Molybdenum Oxide. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1805251. [PMID: 30677221 DOI: 10.1002/smll.201805251] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Indexed: 06/09/2023]
Abstract
Silicon photonics has demonstrated great potential in ultrasensitive biochemical sensing. However, it is challenging for such sensors to detect small ions which are also of great importance in many biochemical processes. A silicon photonic ion sensor enabled by an ionic dopant-driven plasmonic material is introduced here. The sensor consists of a microring resonator (MRR) coupled with a 2D restacked layer of near-infrared plasmonic molybdenum oxide. When the 2D plasmonic layer interacts with ions from the environment, a strong change in the refractive index results in a shift in the MRR resonance wavelength and simultaneously the alteration of plasmonic absorption leads to the modulation of MRR transmission power, hence generating dual sensing outputs which is unique to other optical ion sensors. Proof-of-concept via a pH sensing model is demonstrated, showing up to 7 orders improvement in sensitivity per unit area across the range from 1 to 13 compared to those of other optical pH sensors. This platform offers the unique potential for ultrasensitive and robust measurement of changes in ionic environment, generating new modalities for on-chip chemical sensors in the micro/nanoscale.
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Affiliation(s)
- Guanghui Ren
- School of Engineering, RMIT University, Melbourne, VIC, 3001, Australia
| | - Bao Yue Zhang
- School of Engineering, RMIT University, Melbourne, VIC, 3001, Australia
| | - Qifeng Yao
- Key Laboratory of the Ministry of Education for Optoelectronic Measurement Technology and Instrument, Beijing Information Science & Technology University, Beijing, 100192, China
| | - Ali Zavabeti
- School of Engineering, RMIT University, Melbourne, VIC, 3001, Australia
- College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, 29 Jiangjun Ave., Nanjing, 211100, Nanjing, China
| | - Cesar S Huertas
- School of Engineering, RMIT University, Melbourne, VIC, 3001, Australia
| | - Robert Brkljača
- School of Science, RMIT University, Melbourne, VIC, 3001, Australia
| | | | - Hussein Nili
- Department of Electrical and Computer Engineering, University of California Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Robi S Datta
- School of Engineering, RMIT University, Melbourne, VIC, 3001, Australia
| | - Hareem Khan
- School of Engineering, RMIT University, Melbourne, VIC, 3001, Australia
| | - Azmira Jannat
- School of Engineering, RMIT University, Melbourne, VIC, 3001, Australia
| | - Sumeet Walia
- School of Engineering, RMIT University, Melbourne, VIC, 3001, Australia
| | - Farjana Haque
- School of Engineering, RMIT University, Melbourne, VIC, 3001, Australia
| | - Luke A O'Dell
- Institute for Frontier Materials, Deakin University, Geelong, VIC, 3220, Australia
| | - Yichao Wang
- School of Life and Environmental Sciences, Deakin University, Geelong, VIC, 3220, Australia
| | - Lianqing Zhu
- Key Laboratory of the Ministry of Education for Optoelectronic Measurement Technology and Instrument, Beijing Information Science & Technology University, Beijing, 100192, China
| | - Arnan Mitchell
- School of Engineering, RMIT University, Melbourne, VIC, 3001, Australia
| | - Jian Zhen Ou
- School of Engineering, RMIT University, Melbourne, VIC, 3001, Australia
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12
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Dalfen I, Dmitriev RI, Holst G, Klimant I, Borisov SM. Background-Free Fluorescence-Decay-Time Sensing and Imaging of pH with Highly Photostable Diazaoxotriangulenium Dyes. Anal Chem 2018; 91:808-816. [PMID: 30518209 DOI: 10.1021/acs.analchem.8b02534] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Novel fluorescent diazaoxatriangulenium (DAOTA) pH indicators for lifetime-based self-referenced pH sensing are reported. The DAOTA dyes were decorated with phenolic-receptor groups inducing fluorescence quenching via a photoinduced-electron-transfer mechanism. Electron-withdrawing chlorine substituents ensure response in the most relevant pH range (apparent p Ka' values of ∼5 and 7.5 for the p, p-dichlorophenol- and p-chlorophenol-substituted dyes, respectively). The dyes feature long fluorescence lifetimes (17-20 ns), high quantum yields (∼60%), and high photostabilities. Planar optodes are prepared upon immobilization of the dyes into polyurethane hydrogel D4. Apart from the response in the fluorescence intensity, the optodes show pH-dependent lifetime behavior, which makes them suitable for studying 2D pH distributions with the help of fluorescence-lifetime-imaging techniques. The lifetime response is particularly pronounced for the sensors with high dye concentrations (0.5-1 wt % with respect to the polymer) and is attributed to the efficient homo-FRET mechanism.
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Affiliation(s)
- Irene Dalfen
- Institute of Analytical Chemistry and Food Chemistry , Graz University of Technology , Stremayrgasse 9 , 8010 Graz , Austria
| | - Ruslan I Dmitriev
- School of Biochemistry and Cell Biology , University College Cork , T12 K8AF Cork , Ireland.,Institute for Regenerative Medicine , I.M. Sechenov First Moscow State University , 119146 Moscow , Russian Federation
| | | | - Ingo Klimant
- Institute of Analytical Chemistry and Food Chemistry , Graz University of Technology , Stremayrgasse 9 , 8010 Graz , Austria
| | - Sergey M Borisov
- Institute of Analytical Chemistry and Food Chemistry , Graz University of Technology , Stremayrgasse 9 , 8010 Graz , Austria
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13
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Nagl S. Microfluidic Free-Flow Isoelectric Focusing with Real-Time pI Determination. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2018; 1906:113-124. [PMID: 30488389 DOI: 10.1007/978-1-4939-8964-5_8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Free-flow electrophoresis (FFE) may be used for continuous and preparative separation of a wide variety of biomolecules. Isoelectric focusing (IEF) provides for the separation of compounds according to their isoelectric point (pI). Here we describe a microfluidic chip-based protocol for the fabrication, application, and optical monitoring of free-flow isoelectric focusing (FFIEF) of proteins and peptides on the microscale with optical surveillance of the microscopic pH gradient provided by an integrated pH sensing layer. This protocol may be used with modifications also for the FFIEF of other biomolecules and may serve as template for the fabrication of microfluidic chips with integrated fluorescent or luminescent pH sensor layers for FFE and other applications.
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Affiliation(s)
- Stefan Nagl
- Department of Chemistry, The Hong Kong University of Science and Technology, Kowloon, Hong Kong SAR, China.
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14
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Abstract
Micro free-flow electrophoresis (μFFE) is a continuous separation technique in which analytes are streamed through a perpendicularly applied electric field in a planar separation channel. Analyte streams are deflected laterally based on their electrophoretic mobilities as they flow through the separation channel. A number of μFFE separation modes have been demonstrated, including free zone (FZ), micellar electrokinetic chromatography (MEKC), isoelectric focusing (IEF) and isotachophoresis (ITP). Approximately 60 articles have been published since the first μFFE device was fabricated in 1994. We anticipate that recent advances in device design, detection, and fabrication, will allow μFFE to be applied to a much wider range of applications. Applications particularly well suited for μFFE analysis include continuous, real time monitoring and microscale purifications.
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Affiliation(s)
- Alexander C Johnson
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA.
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15
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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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16
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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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17
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Gruber P, Marques MPC, Szita N, Mayr T. Integration and application of optical chemical sensors in microbioreactors. LAB ON A CHIP 2017; 17:2693-2712. [PMID: 28725897 DOI: 10.1039/c7lc00538e] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The quantification of key variables such as oxygen, pH, carbon dioxide, glucose, and temperature provides essential information for biological and biotechnological applications and their development. Microfluidic devices offer an opportunity to accelerate research and development in these areas due to their small scale, and the fine control over the microenvironment, provided that these key variables can be measured. Optical sensors are well-suited for this task. They offer non-invasive and non-destructive monitoring of the mentioned variables, and the establishment of time-course profiles without the need for sampling from the microfluidic devices. They can also be implemented in larger systems, facilitating cross-scale comparison of analytical data. This tutorial review presents an overview of the optical sensors and their technology, with a view to support current and potential new users in microfluidics and biotechnology in the implementation of such sensors. It introduces the benefits and challenges of sensor integration, including, their application for microbioreactors. Sensor formats, integration methods, device bonding options, and monitoring options are explained. Luminescent sensors for oxygen, pH, carbon dioxide, glucose and temperature are showcased. Areas where further development is needed are highlighted with the intent to guide future development efforts towards analytes for which reliable, stable, or easily integrated detection methods are not yet available.
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Affiliation(s)
- Pia Gruber
- Department of Biochemical Engineering, University College London, Gower Street, WC1E 6BT, London, UK.
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18
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Nagl S. Micro free-flow isoelectric focusing with integrated optical pH sensors. Eng Life Sci 2017; 18:114-123. [PMID: 32624893 DOI: 10.1002/elsc.201700035] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 02/07/2017] [Accepted: 07/13/2017] [Indexed: 01/12/2023] Open
Abstract
Recently, a new observation method for monitoring of pH gradients in microfluidic free-flow electrophoresis has emerged. It is based on the use of chip-integrated fluorescent or luminescent micro sensor layers. These are able to monitor pH gradients in miniaturized separations in real time and spatially resolved; this is particularly useful in isoelectric focusing. Here these multifunctional microdevices that feature continuous separation, monitoring, and in some instances other functionalities, are reviewed. The employed microfabrication procedures to produce these devices are discussed and the different pH sensor matrices that were integrated and their applications in the separation of different types of biomolecules. The procedures for obtaining spatially resolved information about the separated molecules and the pH at the same time and different detection modalities to achieve this such as deep UV fluorescence as well as time-resolved referenced pH sensing and the integration of a precolumn labeling step into these platforms are also highlighted.
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Affiliation(s)
- Stefan Nagl
- Department of Chemistry The Hong Kong University of Science and Technology Kowloon Hong Kong SAR P. R. China
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19
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Affiliation(s)
- Judit Randek
- Division of Biotechnology, IFM, Linköping University, Linköping, Sweden
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20
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Gruber P, Marques MP, Sulzer P, Wohlgemuth R, Mayr T, Baganz F, Szita N. Real-time pH monitoring of industrially relevant enzymatic reactions in a microfluidic side-entry reactor (μSER) shows potential for pH control. Biotechnol J 2017; 12. [DOI: 10.1002/biot.201600475] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 01/16/2017] [Accepted: 01/18/2017] [Indexed: 01/23/2023]
Affiliation(s)
- Pia Gruber
- Department of Biochemical Engineering; University College London; Gordon Street London UK
| | - Marco P.C. Marques
- Department of Biochemical Engineering; University College London; Gordon Street London UK
| | - Philipp Sulzer
- Institute of Analytical Chemistry and Food Chemistry; Graz University of Technology; Graz Austria
| | - Roland Wohlgemuth
- Member of Merck Group; Sigma-Aldrich; Member of Merck Group; Buchs Switzerland
| | - Torsten Mayr
- Institute of Analytical Chemistry and Food Chemistry; Graz University of Technology; Graz Austria
| | - Frank Baganz
- Institute of Analytical Chemistry and Food Chemistry; Graz University of Technology; Graz Austria
| | - Nicolas Szita
- Department of Biochemical Engineering; University College London; Gordon Street London UK
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21
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Kochmann S, Krylov SN. Image processing and analysis system for development and use of free flow electrophoresis chips. LAB ON A CHIP 2017; 17:256-266. [PMID: 27957577 DOI: 10.1039/c6lc01381c] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We present an image processing and analysis system to facilitate detailed performance analysis of free flow electrophoresis (FFE) chips. It consists of a cost-effective self-built imaging setup and a comprehensive customizable software suite. Both components were designed modularly to be accessible, adaptable, versatile, and automatable. The system provides tools for i) automated identification of chip features (e.g. separation zone and flow markers), ii) extraction and analysis of stream trajectories, and iii) evaluation of flow profiles and separation quality (e.g. determination of resolution). Equipped with these tools, the presented image processing and analysis system will enable faster development of FFE chips and applications. It will also serve as a robust detector for fluorescence-based analytical applications of FFE.
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Affiliation(s)
- Sven Kochmann
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada.
| | - Sergey N Krylov
- Department of Chemistry and Centre for Research on Biomolecular Interactions, York University, Toronto, Ontario M3J 1P3, Canada.
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22
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Štěpánová S, Kašička V. Analysis of proteins and peptides by electromigration methods in microchips. J Sep Sci 2016; 40:228-250. [PMID: 27704694 DOI: 10.1002/jssc.201600962] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 09/14/2016] [Accepted: 09/14/2016] [Indexed: 11/07/2022]
Abstract
This review presents the developments and applications of microchip electromigration methods in the separation and analysis of peptides and proteins in the period 2011-mid-2016. The developments in sample preparation and preconcentration, microchannel material, and surface treatment are described. Separations by various microchip electromigration methods (zone electrophoresis in free and sieving media, affinity electrophoresis, isotachophoresis, isoelectric focusing, electrokinetic chromatography, and electrochromatography) are demonstrated. Advances in detection methods are reported and novel applications in the areas of proteomics and peptidomics, quality control of peptide and protein pharmaceuticals, analysis of proteins and peptides in biomatrices, and determination of physicochemical parameters are shown.
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Affiliation(s)
- Sille Štěpánová
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
| | - Václav Kašička
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czech Republic
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23
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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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24
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Shi N, Ugaz VM. Tunable in-situ electro-polymerization of hydrogel films for microchip-based bioanalysis. BIOMICROFLUIDICS 2016; 10:033103. [PMID: 27279930 PMCID: PMC4884193 DOI: 10.1063/1.4952420] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 05/11/2016] [Indexed: 05/08/2023]
Abstract
Electro-polymerization phenomena have been previously investigated at the macroscale in the context of producing polymeric coatings over extended surface areas. But electrical actuation also offers exquisite local control of the polymerized films' position, morphology, and thickness, suggesting compelling advantages in microfluidic-based analysis systems. Here, we introduce a microfabricated platform incorporating arrays of individually addressable on-chip electrodes capable of generating discretely positioned electro-polymerized hydrogel films inside microchannels in timescales of ∼5 min. Sequential actuation of specific electrode pairs initiates localized propagation of anchored polyacrylamide gel films and permits directed control of their size, shape, and growth rate. In addition to precise positioning of hydrogel films, obstacles, and barriers within microchannel networks, our approach makes it possible to encapsulate macromolecules within the films during polymerization, suggesting utility in a host of areas including separations, sample purification, and immunoassays.
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Affiliation(s)
- Nan Shi
- Artie McFerrin Department of Chemical Engineering, Texas A&M University , College Station, Texas 77843-3122, USA
| | - Victor M Ugaz
- Artie McFerrin Department of Chemical Engineering, Texas A&M University , College Station, Texas 77843-3122, USA
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25
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Herzog C, Poehler E, Peretzki AJ, Borisov SM, Aigner D, Mayr T, Nagl S. Continuous on-chip fluorescence labelling, free-flow isoelectric focusing and marker-free isoelectric point determination of proteins and peptides. LAB ON A CHIP 2016; 16:1565-1572. [PMID: 27064144 DOI: 10.1039/c6lc00055j] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We present a microfluidic platform that contains a micro flow reactor for on-chip biomolecule labelling that is directly followed by a separation bed for continuous free-flow electrophoresis and has an integrated hydrogel-based near-infrared fluorescent pH sensor layer. Using this assembly, labelling of protein and peptide mixtures, their separation via free-flow isoelectric focusing and the determination of the isoelectric point (pI) of the separated products via the integrated sensor layer could be carried out within typically around 5 minutes. Spatially-resolved immobilization of fluidic and sensing structures was carried out via multistep photolithography. The assembly was characterized and optimized with respect to their fluidic and pH sensing properties and applied in the IEF of model proteins, peptides and a tryptic digest from physalaemine. We have therefore realized continuous sample preparation and preparative separation, analyte detection, process observation and analyte assignment capability based on pI on a single platform the size of a microscope slide.
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Affiliation(s)
- Christin Herzog
- Institut für Analytische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
| | - Elisabeth Poehler
- Institut für Analytische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
| | - Andrea J Peretzki
- Institut für Analytische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
| | - Sergey M Borisov
- Institut für Analytische Chemie und Lebensmittelchemie, Technische Universität Graz, Stremayrgasse 9/III, 8010 Graz, Austria
| | - Daniel Aigner
- Institut für Analytische Chemie und Lebensmittelchemie, Technische Universität Graz, Stremayrgasse 9/III, 8010 Graz, Austria
| | - Torsten Mayr
- Institut für Analytische Chemie und Lebensmittelchemie, Technische Universität Graz, Stremayrgasse 9/III, 8010 Graz, Austria
| | - Stefan Nagl
- Institut für Analytische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany.
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26
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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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27
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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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28
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Dietze C, Scholl T, Ohla S, Appun J, Schneider C, Belder D. Rapid prototyping of microfluidic chips for dead-volume-free MS coupling. Anal Bioanal Chem 2015; 407:8735-43. [DOI: 10.1007/s00216-015-9027-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 08/20/2015] [Accepted: 09/03/2015] [Indexed: 11/30/2022]
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29
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Park JK, Campos CDM, Neužil P, Abelmann L, Guijt RM, Manz A. Direct coupling of a free-flow isotachophoresis (FFITP) device with electrospray ionization mass spectrometry (ESI-MS). LAB ON A CHIP 2015; 15:3495-3502. [PMID: 26183237 DOI: 10.1039/c5lc00523j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present the online coupling of a free-flow isotachophoresis (FFITP) device to an electrospray ionization mass spectrometer (ESI-MS) for continuous analysis without extensive sample preparation. Free-flow-electrophoresis techniques are used for continuous electrophoretic separations using an electric field applied perpendicular to the buffer and sample flow, with FFITP using a discontinuous electrolyte system to concurrently focus a target analyte and remove interferences. The online coupling of FFITP to ESI-MS decouples the separation and detection timeframe because the electrophoretic separation takes place perpendicular to the flow direction, which can be beneficial for monitoring (bio)chemical changes and/or extensive MS(n) studies. We demonstrated the coupling of FFITP with ESI-MS for simultaneous concentration of target analytes and sample clean-up. Furthermore, we show hydrodynamic control of the fluidic fraction injected into the MS, allowing for fluidically controlled scanning of the ITP window. Future applications of this approach are expected in monitoring biochemical changes and proteomics.
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Affiliation(s)
- J K Park
- Korea Institute of Science and Technology (KIST)-Europe, Campus e 7 1, 66123, Germany.
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30
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Recent applications of microchip electrophoresis to biomedical analysis. J Pharm Biomed Anal 2015; 113:72-96. [DOI: 10.1016/j.jpba.2015.03.002] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 02/28/2015] [Accepted: 03/03/2015] [Indexed: 11/22/2022]
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31
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Pfeiffer SA, Nagl S. Microfluidic platforms employing integrated fluorescent or luminescent chemical sensors: a review of methods, scope and applications. Methods Appl Fluoresc 2015; 3:034003. [DOI: 10.1088/2050-6120/3/3/034003] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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32
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Poehler E, Herzog C, Suendermann M, Pfeiffer SA, Nagl S. Development of microscopic time-domain dual lifetime referencing luminescence detection for pH monitoring in microfluidic free-flow isoelectric focusing. Eng Life Sci 2015. [DOI: 10.1002/elsc.201400081] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Elisabeth Poehler
- Institut für Analytische Chemie; Universität Leipzig; Leipzig Germany
| | - Christin Herzog
- Institut für Analytische Chemie; Universität Leipzig; Leipzig Germany
| | | | - Simon A. Pfeiffer
- Institut für Analytische Chemie; Universität Leipzig; Leipzig Germany
| | - Stefan Nagl
- Institut für Analytische Chemie; Universität Leipzig; Leipzig Germany
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33
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Poehler E, Herzog C, Lotter C, Pfeiffer SA, Aigner D, Mayr T, Nagl S. Label-free microfluidic free-flow isoelectric focusing, pH gradient sensing and near real-time isoelectric point determination of biomolecules and blood plasma fractions. Analyst 2015; 140:7496-502. [DOI: 10.1039/c5an01345c] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Continuous biomolecular separation and pH gradient observation using UV and NIR fluorescence.
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Affiliation(s)
- Elisabeth Poehler
- Institut für Analytische Chemie
- Universität Leipzig
- 04103 Leipzig
- Germany
| | - Christin Herzog
- Institut für Analytische Chemie
- Universität Leipzig
- 04103 Leipzig
- Germany
| | - Carsten Lotter
- Institut für Analytische Chemie
- Universität Leipzig
- 04103 Leipzig
- Germany
| | - Simon A. Pfeiffer
- Institut für Analytische Chemie
- Universität Leipzig
- 04103 Leipzig
- Germany
| | - Daniel Aigner
- Institut für Analytische Chemie und Lebensmittelchemie
- Technische Universität Graz
- 8010 Graz
- Austria
| | - Torsten Mayr
- Institut für Analytische Chemie und Lebensmittelchemie
- Technische Universität Graz
- 8010 Graz
- Austria
| | - Stefan Nagl
- Institut für Analytische Chemie
- Universität Leipzig
- 04103 Leipzig
- Germany
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34
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Poehler E, Herzog C, Pfeiffer SA, Lotter C, Peretzki AJ, Aigner D, Mayr T, Beckert E, Nagl S. Application of Optical pH Sensors in the Microfluidic Free-flow Isoelectric Focusing of Biomolecules. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/j.proeng.2015.08.603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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35
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Present state of microchip electrophoresis: state of the art and routine applications. J Chromatogr A 2014; 1382:66-85. [PMID: 25529267 DOI: 10.1016/j.chroma.2014.11.034] [Citation(s) in RCA: 130] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 11/07/2014] [Accepted: 11/12/2014] [Indexed: 12/20/2022]
Abstract
Microchip electrophoresis (MCE) was one of the earliest applications of the micro-total analysis system (μ-TAS) concept, whose aim is to reduce analysis time and reagent and sample consumption while increasing throughput and portability by miniaturizing analytical laboratory procedures onto a microfluidic chip. More than two decades on, electrophoresis remains the most common separation technique used in microfluidic applications. MCE-based instruments have had some commercial success and have found application in many disciplines. This review will consider the present state of MCE including recent advances in technology and both novel and routine applications in the laboratory. We will also attempt to assess the impact of MCE in the scientific community and its prospects for the future.
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36
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37
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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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38
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Agostino FJ, Cherney LT, Kanoatov M, Krylov SN. Reducing pH Gradients in Free-Flow Electrophoresis. Anal Chem 2014; 86:5656-60. [DOI: 10.1021/ac501081b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Fletcher J. Agostino
- York University, Department of Chemistry and the Centre for Research
on Biomolecular Interactions, 4700 Keele St., Toronto, Ontario M3J 1P3, Canada
| | - Leonid T. Cherney
- York University, Department of Chemistry and the Centre for Research
on Biomolecular Interactions, 4700 Keele St., Toronto, Ontario M3J 1P3, Canada
| | - Mirzo Kanoatov
- York University, Department of Chemistry and the Centre for Research
on Biomolecular Interactions, 4700 Keele St., Toronto, Ontario M3J 1P3, Canada
| | - Sergey N. Krylov
- York University, Department of Chemistry and the Centre for Research
on Biomolecular Interactions, 4700 Keele St., Toronto, Ontario M3J 1P3, Canada
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39
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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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Hackl C, Beyreiss R, Geissler D, Jezierski S, Belder D. Rapid prototyping of electrochromatography chips for improved two-photon excited fluorescence detection. Anal Chem 2014; 86:3773-9. [PMID: 24666258 DOI: 10.1021/ac500793e] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In the present study, we introduce two-photon excitation at 532 nm for label-free fluorescence detection in chip electrochromatography. Two-photon excitation at 532 nm offers a promising alternative to one-photon excitation at 266 nm, as it enables the use of economic chip materials instead of fused silica. In order to demonstrate these benefits, one-photon and two-photon induced fluorescence detection are compared in different chip layouts and materials with respect to the achievable sensitivity in the detection of polycyclic aromatic hydrocarbons (PAHs). Customized chromatography chips with cover or bottom slides of different material and thickness are produced by means of a rapid prototyping method based on liquid-phase lithography. The design of thin bottom chips (180 μm) enables the use of high-performance immersion objectives with low working distances, which allows one to exploit the full potential of two-photon excitation for a sensitive detection. The developed method is applied for label-free analysis of PAHs separated on a polymer monolith inside polymer glass sandwich chips made from fused silica or soda-lime glass. The obtained limits of detection range from 40 nM to 1.95 μM, with similar sensitivities in fused silica thin bottom chips for one-photon and two-photon excitation. In deep-UV non- or less-transparent devices two-photon excitation is mandatory for label-free detection of aromatics with high sensitivity.
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Affiliation(s)
- Claudia Hackl
- Institut für Analytische Chemie, Universität Leipzig , Linnéstraße 3, 04103 Leipzig, Germany
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41
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Ungerböck B, Fellinger S, Sulzer P, Abel T, Mayr T. Magnetic optical sensor particles: a flexible analytical tool for microfluidic devices. Analyst 2014; 139:2551-9. [DOI: 10.1039/c4an00169a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Magnetic optical sensor particles are used to generate in situ sensor spots within microfluidic channels and serve as flexible analytical tools.
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Affiliation(s)
- Birgit Ungerböck
- Applied Sensors
- Institute of Analytical Chemistry and Food Chemistry
- Graz University of Technology
- 8010 Graz, Austria
| | - Siegfried Fellinger
- Applied Sensors
- Institute of Analytical Chemistry and Food Chemistry
- Graz University of Technology
- 8010 Graz, Austria
| | - Philipp Sulzer
- Applied Sensors
- Institute of Analytical Chemistry and Food Chemistry
- Graz University of Technology
- 8010 Graz, Austria
| | - Tobias Abel
- Applied Sensors
- Institute of Analytical Chemistry and Food Chemistry
- Graz University of Technology
- 8010 Graz, Austria
| | - Torsten Mayr
- Applied Sensors
- Institute of Analytical Chemistry and Food Chemistry
- Graz University of Technology
- 8010 Graz, Austria
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42
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Affiliation(s)
- Dorota Wencel
- Optical Sensors Laboratory, School of Physical Sciences, Biomedical Diagnostics Institute, Dublin City University , Dublin, 9 Ireland
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43
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Aigner D, Ungerböck B, Mayr T, Saf R, Klimant I, Borisov SM. Fluorescent materials for pH sensing and imaging based on novel 1,4-diketopyrrolo-[3,4- c]pyrrole dyes†Electronic supplementary information (ESI) available: NMR and MS spectra, further sensor characteristics and sensor long-time performance. See DOI: 10.1039/c3tc31130aClick here for additional data file. JOURNAL OF MATERIALS CHEMISTRY. C 2013; 1:5685-5693. [PMID: 24078864 PMCID: PMC3778741 DOI: 10.1039/c3tc31130a] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 07/16/2013] [Indexed: 05/05/2023]
Abstract
New optical pH-sensors relying on 1,4-diketopyrrolo-[3,4-c]pyrroles (DPPs) as fluorescent pH-indicators are presented. Different polymer hydrogels are useful as immobilization matrices, achieving excellent sensitivity and good brightness in the resulting sensor. The operational pH can be tuned over a wide range (pH 5-12) by selecting the fine structure of the indicator and the matrix. A ratiometric sensor in the form of nanoparticles is also presented. It is suitable for RGB camera readout, and its practical applicability for fluorescence imaging in microfluidic systems is demonstrated. The indicators are synthesized starting from the commercially available DPP pigments by a straightforward concept employing chlorosulfonation and subsequent reaction with amines. Their sensitivity derives from two distinct mechanisms. At high pH (>9), they exhibit a remarkable alteration of both absorption and fluorescence spectra due to deprotonation of the lactam nitrogen atoms. If a phenolic group is introduced, highly effective fluorescence quenching at near-neutral pH occurs due to photoinduced electron transfer (PET) involving the phenolate form.
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Affiliation(s)
- Daniel Aigner
- Institute of Analytical Chemistry and Food Chemistry , Graz University of Technology , Stremayrgasse 9 , Graz , Austria . ; Tel: +43 316 873 32516
| | - Birgit Ungerböck
- Institute of Analytical Chemistry and Food Chemistry , Graz University of Technology , Stremayrgasse 9 , Graz , Austria . ; Tel: +43 316 873 32516
| | - Torsten Mayr
- Institute of Analytical Chemistry and Food Chemistry , Graz University of Technology , Stremayrgasse 9 , Graz , Austria . ; Tel: +43 316 873 32516
| | - Robert Saf
- Institute for Chemistry and Technology of Materials , Graz University of Technology , Stremayrgasse 9 , A-8010 Graz , Austria
| | - Ingo Klimant
- Institute of Analytical Chemistry and Food Chemistry , Graz University of Technology , Stremayrgasse 9 , Graz , Austria . ; Tel: +43 316 873 32516
| | - Sergey M. Borisov
- Institute of Analytical Chemistry and Food Chemistry , Graz University of Technology , Stremayrgasse 9 , Graz , Austria . ; Tel: +43 316 873 32516
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Jezierski S, Klein AS, Benz C, Schaefer M, Nagl S, Belder D. Towards an integrated device that utilizes adherent cells in a micro-free-flow electrophoresis chip to achieve separation and biosensing. Anal Bioanal Chem 2013; 405:5381-6. [PMID: 23591645 DOI: 10.1007/s00216-013-6945-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Revised: 03/16/2013] [Accepted: 03/25/2013] [Indexed: 11/28/2022]
Abstract
We immobilized adherent human embryonic kidney (HEK) cells--which are able to trace adenosine triphosphate (ATP)--inside a microfluidic free-flow electrophoresis (μFFE) chip in order to develop an integrated device combining separation and biosensing capabilities. HEK 293 cells loaded with fluorescent calcium indicators were used as a model system to enable the spatially and temporally resolved detection of ATP. The local position of a 20 μM ATP stream was successfully visualized by these cells during free-flow electrophoresis, demonstrating the on-line detection capability of this technique towards native, unlabeled compounds.
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Affiliation(s)
- Stefan Jezierski
- Institut für Analytische Chemie, Universität Leipzig, Johannisallee 29, 04103 Leipzig, Germany
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Jezierski S, Tehsmer V, Nagl S, Belder D. Integrating continuous microflow reactions with subsequent micropreparative separations on a single microfluidic chip. Chem Commun (Camb) 2013; 49:11644-6. [DOI: 10.1039/c3cc46548a] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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