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Preuss JA, Nguyen GN, Berk V, Bahnemann J. Miniaturized free-flow electrophoresis: production, optimization, and application using 3D printing technology. Electrophoresis 2020; 42:305-314. [PMID: 33128392 DOI: 10.1002/elps.202000149] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 10/22/2020] [Accepted: 10/25/2020] [Indexed: 12/11/2022]
Abstract
The increasing resolution of three-dimensional (3D) printing offers simplified access to, and development of, microfluidic devices with complex 3D structures. Therefore, this technology is increasingly used for rapid prototyping in laboratories and industry. Microfluidic free flow electrophoresis (μFFE) is a versatile tool to separate and concentrate different samples (such as DNA, proteins, and cells) to different outlets in a time range measured in mere tens of seconds and offers great potential for use in downstream processing, for example. However, the production of μFFE devices is usually rather elaborate. Many designs are based on chemical pretreatment or manual alignment for the setup. Especially for the separation chamber of a μFFE device, this is a crucial step which should be automatized. We have developed a smart 3D design of a μFFE to pave the way for a simpler production. This study presents (1) a robust and reproducible way to build up critical parts of a μFFE device based on high-resolution MultiJet 3D printing; (2) a simplified insertion of commercial polycarbonate membranes to segregate separation and electrode chambers; and (3) integrated, 3D-printed wells that enable a defined sample fractionation (chip-to-world interface). In proof of concept experiments both a mixture of fluorescence dyes and a mixture of amino acids were successfully separated in our 3D-printed μFFE device.
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Affiliation(s)
- John-Alexander Preuss
- Institute of Technical Chemistry, Leibniz University Hannover, Callinstraße 5, Hannover, 30167, Germany
| | - Gia Nam Nguyen
- Institute of Technical Chemistry, Leibniz University Hannover, Callinstraße 5, Hannover, 30167, Germany
| | - Virginia Berk
- Institute of Technical Chemistry, Leibniz University Hannover, Callinstraße 5, Hannover, 30167, Germany
| | - Janina Bahnemann
- Institute of Technical Chemistry, Leibniz University Hannover, Callinstraße 5, Hannover, 30167, Germany
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2
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Electro-osmotic flow of electrolyte solutions of PEO in microfluidic channels. J Colloid Interface Sci 2020; 563:381-393. [DOI: 10.1016/j.jcis.2019.12.052] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 12/12/2019] [Accepted: 12/13/2019] [Indexed: 11/23/2022]
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3
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Gökaltun A, Kang YBA, Yarmush ML, Usta OB, Asatekin A. Simple Surface Modification of Poly(dimethylsiloxane) via Surface Segregating Smart Polymers for Biomicrofluidics. Sci Rep 2019; 9:7377. [PMID: 31089162 PMCID: PMC6517421 DOI: 10.1038/s41598-019-43625-5] [Citation(s) in RCA: 111] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 04/09/2019] [Indexed: 12/17/2022] Open
Abstract
Poly(dimethylsiloxane) (PDMS) is likely the most popular material for microfluidic devices in lab-on-a-chip and other biomedical applications. However, the hydrophobicity of PDMS leads to non-specific adsorption of proteins and other molecules such as therapeutic drugs, limiting its broader use. Here, we introduce a simple method for preparing PDMS materials to improve hydrophilicity and decrease non-specific protein adsorption while retaining cellular biocompatibility, transparency, and good mechanical properties without the need for any post-cure surface treatment. This approach utilizes smart copolymers comprised of poly(ethylene glycol) (PEG) and PDMS segments (PDMS-PEG) that, when blended with PDMS during device manufacture, spontaneously segregate to surfaces in contact with aqueous solutions and reduce the hydrophobicity without any added manufacturing steps. PDMS-PEG-modified PDMS samples showed contact angles as low as 23.6° ± 1° and retained this hydrophilicity for at least twenty months. Their improved wettability was confirmed using capillary flow experiments. Modified devices exhibited considerably reduced non-specific adsorption of albumin, lysozyme, and immunoglobulin G. The modified PDMS was biocompatible, displaying no adverse effects when used in a simple liver-on-a-chip model using primary rat hepatocytes. This PDMS modification method can be further applied in analytical separations, biosensing, cell studies, and drug-related studies.
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Affiliation(s)
- Aslıhan Gökaltun
- Center for Engineering in Medicine at Massachusetts General Hospital, Harvard Medical School, and Shriners Hospital for Children, 51 Blossom St., Boston, MA, 02114, USA
- Department of Chemical and Biological Engineering, Tufts University, 4 Colby Street, Medford, MA, 02474, USA
- Department of Chemical Engineering, Hacettepe University, 06532, Beytepe, Ankara, Turkey
| | - Young Bok Abraham Kang
- Center for Engineering in Medicine at Massachusetts General Hospital, Harvard Medical School, and Shriners Hospital for Children, 51 Blossom St., Boston, MA, 02114, USA
| | - Martin L Yarmush
- Center for Engineering in Medicine at Massachusetts General Hospital, Harvard Medical School, and Shriners Hospital for Children, 51 Blossom St., Boston, MA, 02114, USA
- Department of Biomedical Engineering, Rutgers University, 599 Taylor Rd., Piscataway, NJ, 08854, USA
| | - O Berk Usta
- Center for Engineering in Medicine at Massachusetts General Hospital, Harvard Medical School, and Shriners Hospital for Children, 51 Blossom St., Boston, MA, 02114, USA.
| | - Ayse Asatekin
- Department of Chemical and Biological Engineering, Tufts University, 4 Colby Street, Medford, MA, 02474, USA.
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Jing H, Sinha S, Das S. Elasto-electro-capillarity: drop equilibrium on a charged, elastic solid. SOFT MATTER 2017; 13:554-566. [PMID: 27935004 DOI: 10.1039/c6sm02463g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We present a study here on elasto-electro-capillarity - for the first time, the matter of drop equilibrium on a soft (elastic and incompressible) and charged solid has been studied. Charges on the elastic solid induce an electric double layer or EDL at the solid-drop interface. Our analysis accounts for the electrostatic wetting contribution of the EDL in the overall energy balance. Our results reveal that (a) with an increase in "softness", the equilibrium solid-liquid contact angles show transition from the EDL-modified Young's law (rigid limit) to the EDL-modified Neumann's law (soft limit); (b) the EDL effects invariably enhance solid deformation and lower the apparent contact angle made by the drop with the undeformed solid; (c) the solid contact angles increase and the cusp made by the deformed solid undergoes enhanced rotation due to the EDL effects; and (d) the EDL effects are more prominent for the case where the solid-vapor surface energy exceeds the solid-liquid surface energy. The fact that the EDL effects invariably decrease the overall wetting energy of the system, thereby supporting a larger increase in the elastic energy associated with a larger solid deformation, explains all these findings and establishes that surface charges enhance the "softness" of a soft surface in the context of elastocapillarity.
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Affiliation(s)
- Haoyuan Jing
- Department of Mechanical Engineering, University of Maryland, College Park, MD-20742, USA.
| | - Shayandev Sinha
- Department of Mechanical Engineering, University of Maryland, College Park, MD-20742, USA.
| | - Siddhartha Das
- Department of Mechanical Engineering, University of Maryland, College Park, MD-20742, USA.
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6
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Novo P, Dell'Aica M, Jender M, Höving S, Zahedi RP, Janasek D. Integration of polycarbonate membranes in microfluidic free-flow electrophoresis. Analyst 2017; 142:4228-4239. [DOI: 10.1039/c7an01514c] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A general difficulty in the miniaturization of free-flow electrophoresis relates to the need to separate electrodes and separation bed compartments.
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Affiliation(s)
- Pedro Novo
- Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V
- 44227 Dortmund
- Germany
| | - Margherita Dell'Aica
- Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V
- 44227 Dortmund
- Germany
| | - Matthias Jender
- Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V
- 44227 Dortmund
- Germany
| | - Stefan Höving
- Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V
- 44227 Dortmund
- Germany
| | - René P. Zahedi
- Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V
- 44227 Dortmund
- Germany
| | - Dirk Janasek
- Leibniz-Institut für Analytische Wissenschaften - ISAS - e.V
- 44227 Dortmund
- Germany
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Dirany M, Dies L, Restagno F, Léger L, Poulard C, Miquelard-Garnier G. Chemical modification of PDMS surface without impacting the viscoelasticity: Model systems for a better understanding of elastomer/elastomer adhesion and friction. Colloids Surf A Physicochem Eng Asp 2015. [DOI: 10.1016/j.colsurfa.2014.12.036] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Gitlin L, Schulze P, Ohla S, Bongard HJ, Belder D. Surface modification of PDMS microfluidic devices by controlled sulfuric acid treatment and the application in chip electrophoresis. Electrophoresis 2014; 36:449-56. [PMID: 25257973 DOI: 10.1002/elps.201400269] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 09/03/2014] [Accepted: 09/04/2014] [Indexed: 01/13/2023]
Abstract
Herein, we present a straightforward surface modification technique for PDMS-based microfluidic devices. The method takes advantage of the high reactivity of concentrated sulfuric acid to enhance the surface properties of PDMS bulk material. This results in alteration of the surface morphology and chemical composition that is in-depth characterized by ATR-FTIR, EDX, SEM, and XPS. In comparison to untreated PDMS, modified substrates exhibit a significantly reduced diffusive uptake of small organic molecules while retaining its low electroosmotic properties. This was demonstrated by exposing the channels of a microfluidic device to concentrated rhodamine B solution followed by fluorescence microscopy. The surface modification procedure was used to improve chip-based electrophoretic separations. Separation efficiencies of FITC-labeled amines/amino acids obtained in treated and untreated PDMS-devices as well as in glass chips were compared. We obtained higher efficiencies in H2 SO4 treated PDMS chips compared to untreated ones but lower efficiencies than those obtained in commercial microfluidic glass devices.
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Affiliation(s)
- Leonid Gitlin
- Institut für Analytische Chemie, Universität Leipzig, Leipzig, Germany
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9
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Evaluation of polydimethylsiloxane (PDMS) surface modification approaches for microfluidic applications. Colloids Surf A Physicochem Eng Asp 2012. [DOI: 10.1016/j.colsurfa.2012.10.008] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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10
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Yeh PY, Zhang Z, Lin M, Cao X. Nonfouling hydrophilic poly(ethylene glycol) engraftment strategy for PDMS/SU-8 heterogeneous microfluidic devices. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:16227-16236. [PMID: 23110374 DOI: 10.1021/la303196m] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report a novel nonfouling passivation method using poly(ethylene glycol) (PEG) engraftment on the surfaces of poly(dimethylsiloxane) (PDMS) microfluidic devices sealed with SU-8. To achieve bonding between the PDMS and SU-8 surfaces, the PDMS surface was first functionalized with amines by treatment with 3-aminopropyltrimethoxysilane (APTMS) for subsequent reaction with epoxide functional groups on SU-8 surfaces. To modify the heterogeneous surfaces of the resulting PDMS/SU-8 microfluidic device further, the remaining SU-8 surfaces were amino functionalized using ethylene diamine (EDA), followed by treating both amino-functionalized PDMS and SU-8 surfaces with mPEG-NHS (N-hydroxysuccinimide) through an amine-NHS reaction for facile PEG immobilizations, thus simultaneously modifying both PDMS and SU-8 surfaces in one reaction. Detailed surface analyses such as the water contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) were conducted to confirm the chemical reactions and characterize the resulting surface properties. To test the efficacy of this surface-modification strategy, we conducted nonspecific protein and particle binding tests using microfluidic devices with and without modifications. The PEG-modified PDMS/SU-8 device surfaces showed a 64.5% reduction in nonspecific bovine serum albumin (BSA) adsorption in comparison to that of the unmodified surfaces and 92.0 and 95.8% reductions in microbead adhesion under both stagnant and flowing conditions, respectively.
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Affiliation(s)
- Po Ying Yeh
- Department of Chemical and Biological Engineering, University of Ottawa, Ottawa, Ontario, Canada
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11
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Beal JHL, Bubendorfer A, Kemmitt T, Hoek I, Mike Arnold W. A rapid, inexpensive surface treatment for enhanced functionality of polydimethylsiloxane microfluidic channels. BIOMICROFLUIDICS 2012; 6:36503. [PMID: 23898359 PMCID: PMC3423308 DOI: 10.1063/1.4740232] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Accepted: 07/17/2012] [Indexed: 05/18/2023]
Abstract
A rapid, inexpensive method using alkoxysilanes has been developed to selectively coat the interior of polydimethylsiloxane (PDMS) microfluidic channels with an integral silicaceous layer. This method combines the rapid prototyping capabilities of PDMS with the desirable wetting and electroosmotic properties of glass. The procedure can be carried out on the open faces of PDMS blocks prior to enclosure of the channels, or by flowing the reagents through the preformed channels. Therefore, this methodology allows for high-throughput processing of entire microfluidic devices or selective modification of specific areas of a device. Modification of PDMS with tetraethoxysilane generated a stable surface layer, with enhanced wettability and a more stable electroosmotic flow rate than native PDMS. Modification of PDMS with 3-aminopropyltriethoxysilane generated a surface layer bearing amine functionalities allowing for further chemical derivatization of the PDMS surface.
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Affiliation(s)
- John H L Beal
- Nano- & Micro-Fluidics Team, Industrial Research Ltd., 69 Gracefield Road, P.O. Box 31310, Lower Hutt 5040, New Zealand
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12
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Chen LC, Wu CC, Wu RG, Chang HC. Electroosmotic flow control in microfluidic chips using a self-assembled monolayer as the insulator of a flow field-effect transistor. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:11281-11285. [PMID: 22799621 DOI: 10.1021/la302186d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A novel concept for electroosmotic flow (EOF) control in a microfluidic chip is presented by using a self-assembled monolayer as the insulator of a flow field-effect transistor. Bidirectional EOF control with mobility values of 3.4 × 10(-4) and -3.1 × 10(-4) cm(2)/V s can be attained, corresponding to the applied gate voltage at -0.8 and 0.8 V, respectively, without the addition of buffer additives. A relatively high control factor (approximately 400 × 10(-6) cm(2)/V(2) s) can be obtained. The method presented in this study offers a simple strategy to control the EOF.
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Affiliation(s)
- Li-Chia Chen
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
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13
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Viefhues M, Manchanda S, Chao TC, Anselmetti D, Regtmeier J, Ros A. Physisorbed surface coatings for poly(dimethylsiloxane) and quartz microfluidic devices. Anal Bioanal Chem 2011; 401:2113-22. [PMID: 21847528 DOI: 10.1007/s00216-011-5301-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 07/22/2011] [Accepted: 07/28/2011] [Indexed: 01/20/2023]
Abstract
Surface modifications of microfluidic devices are of essential importance for successful bioanalytical applications. Here, we investigate three different coatings for quartz and poly(dimethylsiloxane) (PDMS) surfaces. We employed a triblock copolymer with trade name F(108), poly(L-lysine)-g-poly(ethylene glycol) (PLL-PEG), as well as the hybrid coating n-dodecyl-β-D-maltoside and methyl cellulose (DDM/MC). The impact of these coatings was characterized by measuring the electroosmotic flow (EOF), contact angle, and prevention of protein adsorption. Furthermore, we investigated the influence of static coatings, i.e., the incubation with the coating agent prior to measurements, and dynamic coatings, where the coating agent was present during the measurement. We found that all coatings on PDMS as well as quartz reduced EOF, increased reproducibility of EOF, reduced protein adsorption, and improved the wettability of the surfaces. Among the coating strategies tested, the dynamic coatings with DDM/MC and F(108) demonstrated maximal reduction of EOF and protein adsorption and simultaneously best long-term stability concerning EOF. For PLL-PEG, a reversal in the EOF direction was observed. Interestingly, the static surface coating strategy with F(108) proved to be as effective to prevent protein adsorption as dynamic coating with this block copolymer. These findings will allow optimized parameter choices for coating strategies on PDMS and quartz microfluidic devices in which control of EOF and reduced biofouling are indispensable.
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Affiliation(s)
- M Viefhues
- Experimental Biophysics and Applied Nanoscience, Bielefeld University, 33615 Bielefeld, Germany
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Liu B, Zhang Y, Mayer D, Krause HJ, Jin Q, Zhao J, Offenhäusser A. A simplified poly(dimethylsiloxane) capillary electrophoresis microchip integrated with a low-noise contactless conductivity detector. Electrophoresis 2011; 32:699-704. [DOI: 10.1002/elps.201000562] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Revised: 12/10/2010] [Accepted: 12/11/2010] [Indexed: 11/09/2022]
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Salim M, McArthur SL, Vaidyanathan S, Wright PC. Towards proteomics-on-chip: The role of the surface. ACTA ACUST UNITED AC 2011; 7:101-15. [DOI: 10.1039/c005236a] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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16
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Zhou J, Voelcker NH, Ellis AV. Simple surface modification of poly(dimethylsiloxane) for DNA hybridization. BIOMICROFLUIDICS 2010; 4:46504. [PMID: 21264061 PMCID: PMC3025499 DOI: 10.1063/1.3523055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2010] [Accepted: 11/03/2010] [Indexed: 05/30/2023]
Abstract
Here, we present a simple chemical modification of poly(dimethylsiloxane) (PDMS) by curing a mixture of 2 wt% undecylenic acid (UDA) in PDMS prepolymer on a gold-coated glass slide. This gold slide had been previously pretreated with a self-assembled hydrophilic monolayer of 3-mercaptopropionic acid (MPA). During curing of the UDA∕PDMS prepolymer, the hydrophilic UDA carboxyl moieties diffuses toward the hydrophilic MPA carboxyl moieties on the gold surface. This diffusion of the UDA within the PDMS prepolymer to the surface is a direct result of surface energy minimization. Once completely cured, the PDMS is peeled off the gold substrate, thereby exposing the interfacial carboxyl groups. These groups are then available for subsequent attachment of 5(')-amino terminated DNA oligonucleotides via amide linkages. Our results show that the covalently tethered oligonucleotides can successfully capture fluorescein-labeled complementary oligonucleotides via hybridization, which are visualized using fluorescence microscopy.
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Affiliation(s)
- Jinwen Zhou
- Centre for NanoScale Science and Nanotechnology, School of Chemical and Physical Sciences, Flinders University, Adelaide SA 5001, Australia
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17
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Yamamoto T. Study on 172-nm vacuum ultraviolet light surface modifications of polydimethylsiloxane for micro/nanofluidic applications. SURF INTERFACE ANAL 2010. [DOI: 10.1002/sia.3715] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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18
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A simple poly(dimethylsiloxane) electrophoresis microchip with an integrated contactless conductivity detector. Mikrochim Acta 2010. [DOI: 10.1007/s00604-010-0482-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Affiliation(s)
- Richard N. Zare
- Department of Chemistry, Stanford University, Stanford, California 94305-5080;
| | - Samuel Kim
- Polymer Research Institute and National Core Research Center for Systems Bio-Dynamics, Pohang University of Science and Technology, Pohang, Kyungbuk, Korea;
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Surface modification with BSA blocking based on in situ synthesized gold nanoparticles in poly(dimethylsiloxane) microchip. Colloids Surf B Biointerfaces 2010; 75:608-11. [DOI: 10.1016/j.colsurfb.2009.10.015] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Revised: 09/25/2009] [Accepted: 10/08/2009] [Indexed: 11/18/2022]
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21
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Single-Molecule Spectroscopy Using Microfluidic Platforms. Methods Enzymol 2010. [DOI: 10.1016/s0076-6879(10)72013-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Schrott W, Slouka Z, Cervenka P, Ston J, Nebyla M, Pribyl M, Snita D. Study on surface properties of PDMS microfluidic chips treated with albumin. BIOMICROFLUIDICS 2009; 3:44101. [PMID: 20216963 PMCID: PMC2835281 DOI: 10.1063/1.3243913] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Accepted: 09/13/2009] [Indexed: 05/11/2023]
Abstract
Electrokinetic properties and morphology of PDMS microfluidic chips intended for bioassays are studied. The chips are fabricated by a casting method followed by polymerization bonding. Microchannels are coated with 1% solution of bovine serum albumin (BSA) in Tris buffer. Albumin passively adsorbs on the PDMS surface. Electrokinetic characteristics (electro-osmotic velocity, electro-osmotic mobility, and zeta potential) of the coated PDMS channels are experimentally determined as functions of the electric field strength and the characteristic electrolyte concentration. Atomic force microscopy (AFM) analysis of the surface reveals a "peak and ridge" structure of the protein layer and an imperfect substrate coating. On the basis of the AFM observation, several topologies of the BSA-PDMS surface are proposed. A nonslip mathematical model of the electro-osmotic flow is then numerically analyzed. It is found that the electrokinetic characteristics computed for a channel with the homogeneous distribution of a fixed electric charge do not fit the experimental data. Heterogeneous distribution of the fixed electric charge and the surface roughness is thus taken into account. When a flat PDMS surface with electric charge heterogeneities is considered, the numerical results are in very good agreement with our experimental data. An optimization analysis finally allowed the determination of the surface concentration of the electric charge and the degree of the PDMS surface coating. The obtained findings can be important for correct prediction and possibly for robust control of behavior of electrically driven PDMS microfluidic chips. The proposed method of the electro-osmotic flow analysis at surfaces with a heterogeneous distribution of the surface electric charge can also be exploited in the interpretation of experimental studies dealing with protein-solid phase interactions or substrate coatings.
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Affiliation(s)
- Walter Schrott
- Department of Chemical Engineering, Institute of Chemical Technology, Prague 16628, Czech Republic
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Wang H, Wang D, Wang J, Wang H, Gu J, Han C, Jin Q, Xu B, He C, Cao L, Wang Y, Zhao J. Application of poly(dimethylsiloxane)/glass microchip for fast electrophoretic separation of serum small, dense low-density lipoprotein. J Chromatogr A 2009; 1216:6343-7. [PMID: 19640543 DOI: 10.1016/j.chroma.2009.06.086] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2009] [Revised: 06/16/2009] [Accepted: 06/29/2009] [Indexed: 11/27/2022]
Abstract
Due to the mounting evidence of altered low-density lipoprotein (LDL) size in several disease states, there has been an increasing interest in developing new analytical methods for small, dense low-density lipoprotein (sdLDL) for diagnosis. The present report demonstrates that sdLDL analysis can be performed in a poly(dimethylsiloxane) (PDMS/glass) microchannel. n-Dodecyl beta-D-maltoside (DDM) was utilized to alter channel surface to make it become hydrophilic and nonionic, thus reducing the interaction between the protein and the surface. Moreover, hydroxypropylcellulose (HPC) was added into the running buffer to suppress the adsorption of analytes and also to serve as a sieving matrix. Under optimal conditions, two baseline separations of lipoproteins including high-density lipoprotein (HDL), sdLDL, and lLDL were achieved with different selectivity. LDL particles shown on the electropherogram were also identified by several procedures. This method affords high separation speed and high reproducibility. The intraassay and interassay RSDs of lipoprotein migration times were in the range of 2.01-2.45%. The variation of serum sdLDL of a patient between prior treatment and post-treatment was assessed by this method. This system has the potential for rapid and sensitive detection of different LDL forms, and thus will be applicable to clinical diagnosis.
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Affiliation(s)
- Hua Wang
- Clinical Medical College of Yangzhou University, 98 Nantong West Road, Yangzhou, 225001, China
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24
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Zhou J, Yan H, Ren K, Dai W, Wu H. Convenient Method for Modifying Poly(dimethylsiloxane) with Poly(ethylene glycol) in Microfluidics. Anal Chem 2009; 81:6627-32. [DOI: 10.1021/ac900551m] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jianhua Zhou
- Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Hui Yan
- Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Kangning Ren
- Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Wen Dai
- Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Hongkai Wu
- Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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Van der Steen M, Stevens CV. Undecylenic acid: a valuable and physiologically active renewable building block from castor oil. CHEMSUSCHEM 2009; 2:692-713. [PMID: 19650106 DOI: 10.1002/cssc.200900075] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A lot of attention is currently being paid to the transition to a biobased economy. In this movement, most efforts concentrate on the development of bioenergy applications including bioethanol, biodiesel, thermochemical conversion of biomass, and others. However, in the energy sector other nonbiomass alternatives are known, whereas no valuable alternatives are available when thinking about chemical building blocks. Therefore, it is also essential to develop new routes for the synthesis of bio-based chemicals and materials derived thereof. Such intermediates can originate either from plants or from animals. Castor oil is a non-edible oil extracted from the seeds of the castor bean plant Ricinus communis (Euphorbiaceae), which grows in tropical and subtropical areas. Globally, around one million tons of castor seeds are produced every year, the leading producing areas being India, PR China, and Brazil.2 10-Undecenoic acid or undecylenic acid is a fatty acid derived from castor oil that, owing to its bifunctional nature, has many possibilities to develop sustainable applications.
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Phillips KS, Kottegoda S, Kang KM, Sims CE, Allbritton NL. Separations in poly(dimethylsiloxane) microchips coated with supported bilayer membranes. Anal Chem 2008; 80:9756-62. [PMID: 19006406 PMCID: PMC2735572 DOI: 10.1021/ac801850z] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hybrid microchannels composed of poly(dimethylsiloxane) and glass were coated with supported bilayer membranes (SBMs) by the process of vesicle fusion. The electroosmotic mobility (mu(eo)) of zwitterionic, positively charged, and negatively charged phospholipid membranes was measured over a 4 h time to evaluate the stability of the coatings in an electric field. Coated microchips with a simple cross design were used to separate the fluorescent dyes fluorescein and Oregon Green. Migration time reproducibility was better than 5% RSD over 70 min of continuous separations. Separation of Oregon Green and fluorescein in channels coated with zwitterionic phosphatidylcholine (PC) membranes yielded efficiencies of 611,000 and 499,000 plates/m and a resolution of 2.4 within 2 s. Both zwitterionic and negatively charged membranes were used to separate peptide substrates from their phosphorylated analogues with efficiencies of 200,000-400,000 plates/m. Notably, separations of fluorescently labeled ABL substrate peptide from its phosphorylated counterpart were achieved using a high-salt physiological buffer with near-baseline resolution in 10 s. PC-coated devices were used to successfully separate enhanced green fluorescent protein (eGFP) from a fusion protein (eGFP-Crakl) with an efficiency of 358,000 and 278,000 plates/m respectively in less than 12 s. These SBM-based coatings may enable the separation of a broad range of analytes and may be ideal in biological applications for microfluidics.
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Affiliation(s)
- K Scott Phillips
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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Ding Y, Rogers K. Measurement of Nitrogen Mustard Degradation Products by Poly(dimethylsiloxane) Microchip Electrophoresis with Contactless Conductivity Detection. ELECTROANAL 2008. [DOI: 10.1002/elan.200804320] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Gao Y, Chen L. Versatile control of multiphase laminar flow for in-channel microfabrication. LAB ON A CHIP 2008; 8:1695-1699. [PMID: 18813393 DOI: 10.1039/b807468b] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We have improved the multiphase laminar flow based in-channel fabrication method to overcome diffusion-induced broadening. A sheathing phase with protecting molecules confines metal wire deposition and allows for flexible control of the location, width, and uniformity of deposited metal wires. Two-layered T-junctions are introduced to form vertically stacked multiphase laminar flow. Combining these techniques, we fabricate quadrupole silver electrodes on the four sidewalls of rectangular polydimethylsiloxane (PDMS) microchannels that are 3 cm in length.
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Affiliation(s)
- Yunxiang Gao
- Department of Chemistry and Biochemistry, Ohio University, 136 Clippinger Labs, Athens, Ohio 45701, USA
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Boonsong K, Caulum MM, Dressen BM, Chailapakul O, Cropek DM, Henry CS. Influence of polymer structure on electroosmotic flow and separation efficiency in successive multiple ionic layer coatings for microchip electrophoresis. Electrophoresis 2008; 29:3128-34. [DOI: 10.1002/elps.200800186] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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Abstract
Chemical cytometry, referring to the analysis of the chemical contents in individual cells, has been in intensive study since Kennedy's first work that was published in Science. The early researches relied on fine-tip capillaries to capture the cells and do the analyses, which were lab- and time-intensive and required high skills of operation. The emergence of microfluidics has greatly spurred this research field and a great number of research papers have been published in the last decades. Highly integrated microfluidic chips have been developed to capture multiple single cells, lyse them, perform chemical reactions in enclosed microchambers, separate contents by CE and detect chemical species in individual cells. This review focuses on the development of relevant components and their integration for on-chip chemical cytometry.
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Affiliation(s)
- Hui Yan
- Department of Chemistry, The Hong Kong University of Science and Technology, Hong Kong, P. R. China
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Wu D, Qin J, Lin B. Electrophoretic separations on microfluidic chips. J Chromatogr A 2008; 1184:542-59. [PMID: 18207148 PMCID: PMC7094303 DOI: 10.1016/j.chroma.2007.11.119] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Revised: 11/17/2007] [Accepted: 11/30/2007] [Indexed: 02/07/2023]
Abstract
This review presents a brief outline and novel developments of electrophoretic separation in microfluidic chips. Distinct characteristics of microchip electrophoresis (MCE) are discussed first, in which sample injection plug, joule heat, channel turn, surface adsorption and modification are introduced, and some successful strategies and recognized conclusions are also included. Important achievements of microfluidic electrophoresis separation in small molecules, DNA and protein are then summarized. This review is aimed at researchers, who are interested in MCE and want to adopt MCE as a functional unit in their integrated microsystems.
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Affiliation(s)
| | - Jianhua Qin
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Bingcheng Lin
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
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Xiao Y, Yu XD, Xu JJ, Chen HY. Bulk modification of PDMS microchips by an amphiphilic copolymer. Electrophoresis 2007; 28:3302-7. [PMID: 17854125 DOI: 10.1002/elps.200700024] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A simple and rapid bulk-modification method based on adding an amphiphilic copolymer during the fabrication process was employed to modify PDMS microchips. Poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) was used as the additive substance. Compared to the native PDMS microchips, both the contact angle and the EOF of the bulk-modified PDMS microchips decreased. The effects of the additive loading and the pH on the EOF were investigated in detail. The bulk-modified PDMS microchips exhibited reproducible and stable EOF behavior. The application of the bulk-modified PDMS microchips was also studied and the results indicated that they could be successfully used to separate amino acids and to suppress protein adsorption.
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Affiliation(s)
- Yan Xiao
- The Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, PR China
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Wu D, Qin J, Lin B. Self-assembled epoxy-modified polymer coating on a poly(dimethylsiloxane) microchip for EOF inhibition and biopolymers separation. LAB ON A CHIP 2007; 7:1490-6. [PMID: 17960276 DOI: 10.1039/b708877a] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A straightforward approach to generate a stable and protein-resistant poly(dimethylsiloxane) (PDMS) surface using self-assembled hydrophilic polymers is demonstrated in this work. Epoxy-modified polymers were directly adsorbed from aqueous solution onto plasma oxidized PDMS based on H-bond interaction, and epoxies of polymer and silanols on oxidized PDMS surface were crosslinked by heating at 110 degrees C. The coating process could be completed within half hour. Poly(dimethylacrylamide-co-glycidyl methacrylate) (PDMA-co-GMA), poly(vinyl pyrrolidone)-g-glycidyl methacrylate (PVP-g-GMA) and poly(vinyl alcohol)-g-glycidyl methacrylate (PVA-g-GMA) (D. P. Wu, B. X. Zhao, Z. P. Dai, J. H. Qin and B. C. Lin, Lab Chip, 2006, 6, 942) were employed as examples here. Unlike PDMA, PVP, and PVA themselves, these epoxy-modified hydrophilic polymers could be directly used as static surface coatings on oxidized PDMS, and inhibited electroosmotic flow (EOF) within pH 3-11. It was also found that hard baking of PDMS at 150 degrees C for 24 hours before surface coating could greatly retard surface hydrophobicity recovery after oxygen plasma exposure, which strengthened epoxy-modified polymer coatings on oxidized PDMS surface, and resulted in EOF less than 0.2 x 10(-4) cm(2) V(-1) s(-1) (pH 9.0) within two weeks. On epoxy-modified polymer coated PDMS microchips, basic proteins, peptides and DNA fragments could be separated satisfactorily, in which more than 2 x 10(4) plates per 2 cm and less than 3% RSD (>8 runs) for migration time were obtained for lysozyme.
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Affiliation(s)
- Dapeng Wu
- Dalian Institute of Chemical Physics, Dalian, 116023, China
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