1
|
Capillary electrophoresis and Raman: Can we ever expect light at the end of the tunnel? Trends Analyt Chem 2023. [DOI: 10.1016/j.trac.2023.117017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
|
2
|
Ni C, Zhao J, Xia X, Wang Z, Zhao X, Yang J, Zhang N, Yang Y, Zhang H, Gao D. Constructing a Ring-like Self-Aggregation SERS Sensor with the Coffee Ring Effect for Ultrasensitive Detection and Photocatalytic Degradation of the Herbicides Paraquat and Diquat. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2022; 70:15296-15310. [PMID: 36441926 DOI: 10.1021/acs.jafc.2c06488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A strategy for building ring-like deposit surface-enhanced Raman scattering (SERS) sensors with the coffee ring effect through the functional modification of the silica nanoparticle surface encapsulated by free-tagged Ag nanoparticles is addressed along with their applications in the SERS-based detection and degradation of target species, including paraquat, diquat, and their free radicals. The nanogap formed by two interparticles with SERS hotspots provides a gigantic amplification signal for the Raman scattering intensity of the analyte molecule located approximately at the hotspots. The enhanced Raman spectrum signals of these target analytes were achieved through the hotspot region of the surface plasmon resonance (SPR) located on the embankment formed by self-aggregation of SiO2@Ag nanoparticles due to the coffee ring effect. Meanwhile, the intrinsic properties of Ag nanoparticles embedded onto the silica surface were applied to photocatalytically degrade the target analytes by harvesting energy from sunlight. The SERS sensor detected the analytes down to 10-9 M in the aqueous solution.
Collapse
Affiliation(s)
- Caiyu Ni
- Department of Chemical Engineering, School of Energy, Materials and Chemical Engineering, Hefei University, Hefei230601, Anhui, China
| | - Jiadong Zhao
- Department of Chemical Engineering, School of Energy, Materials and Chemical Engineering, Hefei University, Hefei230601, Anhui, China
| | - Xiaoxiao Xia
- Department of Biological Engineering, School of Biology, Food and Environment Engineering, Hefei University, Hefei230601, Anhui, China
| | - Zhihui Wang
- Department of Chemical Engineering, School of Energy, Materials and Chemical Engineering, Hefei University, Hefei230601, Anhui, China
| | - Xiaoxiao Zhao
- Department of Chemical Engineering, School of Energy, Materials and Chemical Engineering, Hefei University, Hefei230601, Anhui, China
| | - Junyu Yang
- Department of Chemical Engineering, School of Energy, Materials and Chemical Engineering, Hefei University, Hefei230601, Anhui, China
| | - Nianxi Zhang
- Department of Chemical Engineering, School of Energy, Materials and Chemical Engineering, Hefei University, Hefei230601, Anhui, China
| | - Yang Yang
- Department of Biological Engineering, School of Biology, Food and Environment Engineering, Hefei University, Hefei230601, Anhui, China
| | - Hui Zhang
- Department of Chemical Engineering, School of Energy, Materials and Chemical Engineering, Hefei University, Hefei230601, Anhui, China
| | - Daming Gao
- Department of Chemical Engineering, School of Energy, Materials and Chemical Engineering, Hefei University, Hefei230601, Anhui, China
| |
Collapse
|
3
|
Abstract
Isotachophoresis (ITP) is a versatile electrophoretic technique that can be used for sample preconcentration, separation, purification, and mixing, and to control and accelerate chemical reactions. Although the basic technique is nearly a century old and widely used, there is a persistent need for an easily approachable, succinct, and rigorous review of ITP theory and analysis. This is important because the interest and adoption of the technique has grown over the last two decades, especially with its implementation in microfluidics and integration with on-chip chemical and biochemical assays. We here provide a review of ITP theory starting from physicochemical first-principles, including conservation of species, conservation of current, approximation of charge neutrality, pH equilibrium of weak electrolytes, and so-called regulating functions that govern transport dynamics, with a strong emphasis on steady and unsteady transport. We combine these generally applicable (to all types of ITP) theoretical discussions with applications of ITP in the field of microfluidic systems, particularly on-chip biochemical analyses. Our discussion includes principles that govern the ITP focusing of weak and strong electrolytes; ITP dynamics in peak and plateau modes; a review of simulation tools, experimental tools, and detection methods; applications of ITP for on-chip separations and trace analyte manipulation; and design considerations and challenges for microfluidic ITP systems. We conclude with remarks on possible future research directions. The intent of this review is to help make ITP analysis and design principles more accessible to the scientific and engineering communities and to provide a rigorous basis for the increased adoption of ITP in microfluidics.
Collapse
Affiliation(s)
- Ashwin Ramachandran
- Department
of Aeronautics and Astronautics, Stanford
University, Stanford, California 94305, United States
| | - Juan G. Santiago
- Department
of Mechanical Engineering, Stanford University, Stanford, California 94305, United States
| |
Collapse
|
4
|
Somaweera H, Estlack Z, Devadhasan JP, Kim J, Kim J. Characterization and Optimization of Isotachophoresis Parameters for Pacific Blue Succinimidyl Ester Dye on a PDMS Microfluidic Chip. MICROMACHINES 2020; 11:mi11110951. [PMID: 33105673 PMCID: PMC7690402 DOI: 10.3390/mi11110951] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 10/20/2020] [Accepted: 10/20/2020] [Indexed: 01/23/2023]
Abstract
Isotachophoresis (ITP) for Pacific Blue (PB) dye using a polydimethylsiloxane (PDMS) microfluidic chip is developed and characterized by determining the types and concentrations of electrolytes, the ITP duration, and the electric field density. Among candidate buffers for the trailing electrolyte (TE) and leading electrolyte (LE), 40 mM borate buffer (pH 9) and 200 mM trisaminomethane hydrochloride (Tris-HCl) (pH 8) were selected to obtain the maximum preconcentration and resolution of the PB bands, respectively. With the selected TE and LE buffers, further optimization was performed to determine the electric field (EF) density and the ITP duration. These ITP parameters showed a 20–170,000 preconcentration ratio from initial PB concentrations of 10 nM–100 fM. Further demonstration was implemented to preconcentrate PB-conjugated lactate dehydrogenase (LDH) using the PDMS microfluidic chip. By utilizing the quenching nature of PB-LDH conjugation, we were able to identify concentrations of LDH as low as 10 ng/mL. This simple PDMS microfluidic chip-based ITP for PB preconcentration enables highly sensitive biological and chemical analyses by coupling with various downstream detection systems.
Collapse
Affiliation(s)
- Himali Somaweera
- Department of Mechanical Engineering, Texas Tech University, Lubbock, TX 79409, USA; (H.S.); (J.P.D.)
| | - Zachary Estlack
- Department of Mechanical Engineering, University of Utah, Salt Lake City, UT 84112, USA;
| | | | | | - Jungkyu Kim
- Department of Mechanical Engineering, University of Utah, Salt Lake City, UT 84112, USA;
- Correspondence: ; Tel.: +1-(801)-581-6743
| |
Collapse
|
5
|
Masár M, Troška P, Hradski J, Talian I. Microchip isotachophoresis coupled to surface-enhanced Raman spectroscopy for pharmaceutical analysis. Mikrochim Acta 2020; 187:448. [PMID: 32676809 DOI: 10.1007/s00604-020-04436-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 07/07/2020] [Indexed: 11/26/2022]
Abstract
A novel online coupling of microchip isotachophoresis (μITP) with surface-enhanced Raman spectroscopy (SERS) for the analysis of complex samples is presented. Polymeric microchip with coupled channels was used for μITP-SERS analysis of four structurally similar Raman active synthetic dyes (brilliant black BN, carmoisine, ponceau 4R, and sunset yellow FCF) in pharmaceuticals. The μITP separation and simultaneous pre-concentration of the analytes were performed in the first channel of the microchip at pH 6.0 with the aid of non-Raman active discrete spacers (acetate, butyrate, glutarate, pantothenate, and valerate). Silver nanoparticles used for Raman enhancement were present in the second channel, and individual SERS spectra of the dyes were acquired by a mini Raman spectrometer operating at 532 nm. The analytical enhancement factors for silver nanoparticles were 1-5 × 104. The microchip with coupled channels enabled independent μITP separation and SERS detection, and eliminated any adverse impact of nanoparticles on the separation. The developed approach allowed reliable online SERS identification and detection of dyes with limits of detection ranging from 12 to 62 nM. Synthetic dyes were successfully separated, identified, and quantified in pharmaceutical preparations within 7 min without the need for complex or time-consuming sample pretreatment. The results were in good agreement with those obtained by an independent analytical method reported for studied dyes. Graphical abstract.
Collapse
Affiliation(s)
- Marián Masár
- Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH2, Ilkovičova 6, 842 15, Bratislava, Slovakia.
| | - Peter Troška
- Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH2, Ilkovičova 6, 842 15, Bratislava, Slovakia
| | - Jasna Hradski
- Department of Analytical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH2, Ilkovičova 6, 842 15, Bratislava, Slovakia
| | - Ivan Talian
- Department of Medical and Clinical Biophysics, Faculty of Medicine, Pavol Jozef Šafárik University in Košice, Trieda SNP 1, 04011, Košice, Slovakia
| |
Collapse
|
6
|
Abstract
Microfluidic systems are developing in application and importance in many aspects of chemistry. This short review aims to provide a simple introduction to some of the concepts and instrumentation involved in this field. In particular, a number of systems for reactions, detections and analysis that have arisen from the research of our group are illustrated.
Collapse
|
7
|
Li X, Luo L, Crooks RM. Low-voltage paper isotachophoresis device for DNA focusing. LAB ON A CHIP 2015; 15:4090-8. [PMID: 26338530 PMCID: PMC4589534 DOI: 10.1039/c5lc00875a] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We present a new paper-based isotachophoresis (ITP) device design for focusing DNA samples having lengths ranging from 23 to at least 1517 bp. DNA is concentrated by more than two orders of magnitude within 4 min. The key component of this device is a 2 mm-long, 2 mm-wide circular paper channel formed by concertina folding a paper strip and aligning the circular paper zones on each layer. Due to the short channel length, a high electric field of ~16 kV m(-1) is easily generated in the paper channel using two 9 V batteries. The multilayer architecture also enables convenient reclamation and analysis of the sample after ITP focusing by simply opening the origami paper and cutting out the desired layers. We profiled the electric field in the origami paper channel during ITP experiments using a nonfocusing fluorescent tracer. The result showed that focusing relied on formation and subsequent movement of a sharp electric field boundary between the leading and trailing electrolyte.
Collapse
Affiliation(s)
- Xiang Li
- Department of Chemistry, The University of Texas at Austin, 105 E. 24th St., Stop A5300, Austin, TX 78712-1224, USA.
| | | | | |
Collapse
|
8
|
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.
Collapse
|
9
|
Negri P, Schultz ZD. Online SERS detection of the 20 proteinogenic L-amino acids separated by capillary zone electrophoresis. Analyst 2014; 139:5989-98. [PMID: 25268706 PMCID: PMC4249764 DOI: 10.1039/c4an01177e] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A sheath-flow surface-enhanced Raman scattering (SERS) detector is demonstrated to provide chemical information enabling identification of the 20 proteinogenic L-amino acids separated by capillary zone electrophoresis (CZE). Amino acids were used to illustrate the chemical specificity of SERS detection from structurally related molecules. Analysis of the SERS electropherograms obtained from the separation and sequential online detection of six groups of structurally related amino acids shows that our sheath-flow SERS detector is able to resolve the characteristic Raman bands attributed to the amine, carboxyl, and side chain constituents. The results demonstrate the chemical information available from our detector and also provide insight into the nature of the analyte interaction with the silver SERS substrate. The spectra extracted from the SERS electropherogram of a mixture containing the 20 proteinogenic L-amino acids show unique signatures characteristic to each amino acid, thus enabling identification. The results presented here demonstrate the potential of this sheath-flow SERS detector as a general purpose method for high throughput characterization and identification following separations of complex biomolecular mixtures.
Collapse
Affiliation(s)
- Pierre Negri
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
| | | |
Collapse
|
10
|
Goet G, Baier T, Hardt S, Sen AK. Isotachophoresis with emulsions. BIOMICROFLUIDICS 2013; 7:44103. [PMID: 24404037 PMCID: PMC3732298 DOI: 10.1063/1.4816347] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 07/09/2013] [Indexed: 05/16/2023]
Abstract
An experimental study on isotachophoresis (ITP) in which an emulsion is used as leading electrolyte (LE) is reported. The study aims at giving an overview about the transport and flow phenomena occurring in that context. Generally, it is observed that the oil droplets initially dispersed in the LE are collected at the ITP transition zone and advected along with it. The detailed behavior at the transition zone depends on whether or not surfactants (polyvinylpyrrolidon, PVP) are added to the electrolytes. In a system without surfactants, coalescence is observed between the droplets collected at the ITP transition zone. After having achieved a certain size, the droplets merge with the channel walls, leaving an oil film behind. In systems with PVP, coalescence is largely suppressed and no merging of droplets with the channel walls is observed. Instead, at the ITP transition zone, a droplet agglomerate of increasing size is formed. In the initial stages of the ITP experiments, two counter rotating vortices are formed inside the terminating electrolyte. The vortex formation is qualitatively explained based on a hydrodynamic instability triggered by fluctuations of the number density of oil droplets.
Collapse
Affiliation(s)
- G Goet
- Institute for Nano- and Microfluidics, Center of Smart Interfaces, TU Darmstadt, 64287 Darmstadt, Germany
| | - T Baier
- Institute for Nano- and Microfluidics, Center of Smart Interfaces, TU Darmstadt, 64287 Darmstadt, Germany
| | - S Hardt
- Institute for Nano- and Microfluidics, Center of Smart Interfaces, TU Darmstadt, 64287 Darmstadt, Germany
| | - A K Sen
- Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036, India
| |
Collapse
|
11
|
Cao Z, Yobas L. Microchannel plate as a novel bipolar electrode for high-performance enrichment of anions. Electrophoresis 2013; 34:1991-7. [DOI: 10.1002/elps.201300040] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Zhen Cao
- Department of Electronic and Computer Engineering; Hong Kong University of Science and Technology, Clear Water Bay; Kowloon; Hong Kong
| | - Levent Yobas
- Department of Electronic and Computer Engineering; Hong Kong University of Science and Technology, Clear Water Bay; Kowloon; Hong Kong
| |
Collapse
|
12
|
Smejkal P, Bottenus D, Breadmore MC, Guijt RM, Ivory CF, Foret F, Macka M. Microfluidic isotachophoresis: A review. Electrophoresis 2013; 34:1493-509. [DOI: 10.1002/elps.201300021] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 03/06/2013] [Accepted: 03/07/2013] [Indexed: 12/22/2022]
Affiliation(s)
- Petr Smejkal
- ACROSS and School of Chemistry; University of Tasmania; Hobart; Australia
| | - Danny Bottenus
- Voiland School of Chemical Engineering and Bioengineering; Washington State University; Pullman; WA; USA
| | | | - Rosanne M. Guijt
- ACROSS and School of Pharmacy; University of Tasmania; Hobart; Australia
| | - Cornelius F. Ivory
- Voiland School of Chemical Engineering and Bioengineering; Washington State University; Pullman; WA; USA
| | - František Foret
- Institute of Analytical Chemistry of the Academy of Sciences of the Czech Republic; v.v.i., Brno; Czech Republic
| | - Mirek Macka
- ACROSS and School of Chemistry; University of Tasmania; Hobart; Australia
| |
Collapse
|
13
|
Microfluidic Paper-Based Analytical Devices (μPADs) and Micro Total Analysis Systems (μTAS): Development, Applications and Future Trends. Chromatographia 2013; 76:1201-1214. [PMID: 24078738 PMCID: PMC3779795 DOI: 10.1007/s10337-013-2413-y] [Citation(s) in RCA: 139] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 12/26/2012] [Accepted: 01/30/2013] [Indexed: 01/09/2023]
Abstract
Microfluidic paper-based analytical devices and micro total analysis systems are relatively new group of analytical tools, capable of analyzing complex biochemical samples containing macromolecules, proteins, nucleic acids, toxins, cells or pathogens. Within one analytical run, fluidic manipulations like transportation, sorting, mixing or separation are available. Recently, microfluidic devices are a subject of extensive research, mostly for fast and non-expensive biochemical analysis but also for screening of medical samples and forensic diagnostics. They are used for neurotransmitter detection, cancer diagnosis and treatment, cell and tissue culture growth and amplification, drug discovery and determination, detection and identification of microorganisms. This review summarizes development history, basic fabrication methods, applications and also future development trends for production of such devices.
Collapse
|
14
|
|
15
|
|
16
|
Janssen KGH, Li J, Hoang HT, Vulto P, van den Berg RJBHN, Overkleeft HS, Eijkel JCT, Tas NR, van der Linden HJ, Hankemeier T. Limits of miniaturization: assessing ITP performance in sub-micron and nanochannels. LAB ON A CHIP 2012; 12:2888-2893. [PMID: 22691967 DOI: 10.1039/c2lc21011h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The feasibility of isotachophoresis in channels of sub micrometer and nanometer dimension is investigated. A sample injection volume of 0.4 pL is focused and separated in a 330 nm deep channel. The sample consists of a biomatrix containing the fluorescently-labeled amino acids glutamate and phenylalanine, 20 attomoles of each. Isotachophoretic focusing is successfully demonstrated in a 50 nm deep channel. Separation of the two amino acids in the 50 nm deep channel however, could not be performed as the maximum applicable voltage was insufficient. This limit is imposed by bubble formation that we contribute to cavitation as a result of the mismatch in electro-osmotic flow, so called electrocavitation. This represents an unexpected limit on the miniaturization of ITP. Nonetheless, we report the smallest isotachophoretic separation and focusing experiment to date, both in terms of controlled sample injection volume and channel height.
Collapse
Affiliation(s)
- Kjeld G H Janssen
- Department of Analytical Biosciences, Leiden/Amsterdam Centre for Drug Research (LACDR), Leiden University, P.O. Box 9502, 2300 RA, Leiden, The Netherlands
| | | | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Kenyon SM, Weiss NG, Hayes MA. Using electrophoretic exclusion to manipulate small molecules and particles on a microdevice. Electrophoresis 2012; 33:1227-35. [PMID: 22589099 DOI: 10.1002/elps.201100622] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Electrophoretic exclusion, a novel separations technique that differentiates species in bulk solution using the opposing forces of electrophoretic velocity and hydrodynamic flow, has been adapted to a microscale device. Proof-of-principle experiments indicate that the device was able to exclude small particles (1 μm polystyrene microspheres) and fluorescent dye molecules (rhodamine 123) from the entrance of a channel. Additionally, differentiation of the rhodamine 123 and polystyrene spheres was demonstrated. The current studies focus on the direct observation of the electrophoretic exclusion behavior on a microchip.
Collapse
Affiliation(s)
- Stacy M Kenyon
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA
| | | | | |
Collapse
|
18
|
Draper MC, Niu X, Cho S, James DI, Edel JB. Compartmentalization of Electrophoretically Separated Analytes in a Multiphase Microfluidic Platform. Anal Chem 2012; 84:5801-8. [DOI: 10.1021/ac301141x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Mark C. Draper
- Department of Chemistry, Imperial College London, Exhibition Road, South Kensington,
London, SW7 2AZ, United Kingdom
| | - Xize Niu
- Engineering and the Environment,
and Institute for Life Sciences, University of Southampton, Highfield, Southampton, SO17 1BJ, United Kingdom
| | - Soongwon Cho
- Department of Chemistry, Imperial College London, Exhibition Road, South Kensington,
London, SW7 2AZ, United Kingdom
| | - David I. James
- Department of Chemistry, Imperial College London, Exhibition Road, South Kensington,
London, SW7 2AZ, United Kingdom
| | - Joshua B. Edel
- Department of Chemistry, Imperial College London, Exhibition Road, South Kensington,
London, SW7 2AZ, United Kingdom
| |
Collapse
|
19
|
Microfluidic Raman Spectroscopy for Bio-chemical Sensing and Analysis. SPRINGER SERIES ON CHEMICAL SENSORS AND BIOSENSORS 2012. [DOI: 10.1007/978-3-642-25498-7_9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
20
|
Quist J, Janssen KGH, Vulto P, Hankemeier T, van der Linden HJ. Single-Electrolyte Isotachophoresis Using a Nanochannel-Induced Depletion Zone. Anal Chem 2011; 83:7910-5. [DOI: 10.1021/ac2018348] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Jos Quist
- Division of Analytical Biosciences, LACDR, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
- Netherlands Metabolomics Centre, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| | - Kjeld G. H. Janssen
- Division of Analytical Biosciences, LACDR, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
- Netherlands Metabolomics Centre, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| | - Paul Vulto
- Division of Analytical Biosciences, LACDR, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
- Netherlands Metabolomics Centre, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| | - Thomas Hankemeier
- Division of Analytical Biosciences, LACDR, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
- Netherlands Metabolomics Centre, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| | - Heiko J. van der Linden
- Division of Analytical Biosciences, LACDR, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
- Netherlands Metabolomics Centre, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| |
Collapse
|
21
|
Ashok PC, Singh GP, Rendall HA, Krauss TF, Dholakia K. Waveguide confined Raman spectroscopy for microfluidic interrogation. LAB ON A CHIP 2011; 11:1262-70. [PMID: 21225053 DOI: 10.1039/c0lc00462f] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We report the first implementation of the fiber based microfluidic Raman spectroscopic detection scheme, which can be scaled down to micrometre dimensions, allowing it to be combined with other microfluidic functional devices. This novel Raman spectroscopic detection scheme, which we termed as Waveguide Confined Raman Spectroscopy (WCRS), is achieved through embedding fibers on-chip in a geometry that confines the Raman excitation and collection region which ensures maximum Raman signal collection. This results in a microfluidic chip with completely alignment-free Raman spectroscopic detection scheme, which does not give any background from the substrate of the chip. These features allow a WCRS based microfluidic chip to be fabricated in polydimethylsiloxane (PDMS) which is a relatively cheap material but has inherent Raman signatures in fingerprint region. The effects of length, collection angle, and fiber core size on the collection efficiency and fluorescence background of WCRS were investigated. The ability of the device to predict the concentration was studied using urea as a model analyte. A major advantage of WCRS is its scalability that allows it to be combined with many existing microfluidic functional devices. The applicability of WCRS is demonstrated through two microfluidic applications: reaction monitoring in a microreactor and detection of analyte in a microdroplet based microfluidic system. The WCRS approach may lead to wider use of Raman spectroscopy based detection in microfluidics, and the development of portable, alignment-free microfluidic devices.
Collapse
Affiliation(s)
- Praveen C Ashok
- SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, Fife KY16 9SS, UK.
| | | | | | | | | |
Collapse
|
22
|
Ranc V, Staňová A, Marák J, Maier V, Ševčík J, Kaniansky D. Preparative isotachophoresis with surface enhanced Raman scattering as a promising tool for clinical samples analysis. J Chromatogr A 2011; 1218:205-10. [DOI: 10.1016/j.chroma.2010.11.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Revised: 10/29/2010] [Accepted: 11/15/2010] [Indexed: 11/26/2022]
|
23
|
Du JR, Wei HH. Focusing and trapping of DNA molecules by head-on ac electrokinetic streaming through join asymmetric polarization. BIOMICROFLUIDICS 2010; 4:034108. [PMID: 20838480 PMCID: PMC2937043 DOI: 10.1063/1.3481468] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Accepted: 07/31/2010] [Indexed: 05/23/2023]
Abstract
In this work, invoking join asymmetric ac polarization using double half-quadrupole electrodes in a symmetric arrangement, we demonstrate a head-on ac electro-osmotic streaming capable of focusing and trapping DNA molecules efficiently. This is manifested by the observation that picomolar DNA molecules can be trapped into a large crosslike spot with at least an order of magnitude concentration enhancement within just half a minute. We identify that the phenomenon is a combined result of the formation of two prefocused DNA jets flowing toward each other, dipole-induced attraction between focused DNA molecules, and dielectrophoretic trap on the spot. With an additional horizontal pumping, we observe that the trap can transform into a peculiar pitchfork streaming capable of continuous collection and long-distance transport of concentrated DNA molecules. We also show that the same electrode design can be used to direct assembly of submicrometer particles. This newly designed microfluidic platform not only has potentials in enhancing detection sensitivity and facilitating functional assembly for on-chip analysis but also provides an added advantage of transporting target molecules in a focused and continuous manner.
Collapse
Affiliation(s)
- Jung-Rong Du
- Department of Chemical Engineering and Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan
| | | |
Collapse
|
24
|
Greener J, Abbasi B, Kumacheva E. Attenuated total reflection Fourier transform infrared spectroscopy for on-chip monitoring of solute concentrations. LAB ON A CHIP 2010; 10:1561-1566. [PMID: 20376405 DOI: 10.1039/c001889a] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We report a cost-efficient Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) method for monitoring concentrations of solutes in solutions flowing through microfluidic channels. The method allows rapid acquisition of spectra and enables chemical characterisation and concentration measurements that are independent of the flow rate of liquids. The method enables independent measurement of concentrations of solutes with distinct spectral features in mixed solutions. For the polymer solutes studied in the present work, the method has a sensitivity of at least 10 microM (0.01 wt%). We also propose the applicability of the method for the differentiation between dissolved and adsorbed amphiphilic species.
Collapse
Affiliation(s)
- Jesse Greener
- Department of Chemistry, University of Toronto, 80 Saint George Street, Toronto, Ontario, Canada M5S 3H6
| | | | | |
Collapse
|
25
|
On-column silver substrate synthesis and surface-enhanced Raman detection in capillary electrophoresis. Anal Bioanal Chem 2010; 396:2341-8. [DOI: 10.1007/s00216-010-3468-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 12/21/2009] [Accepted: 01/11/2010] [Indexed: 11/27/2022]
|
26
|
Kogan M, Solomon MJ. Electric-field-induced yielding of colloidal gels in microfluidic capillaries. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:1207-1213. [PMID: 20067317 DOI: 10.1021/la9023635] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We introduce a method to generate a purely internal rupture of colloidal particle gels by application of an electric field as they are confined in a microfluidic device. Characterization of the local, microstructural effect of yielding made possible by the device avoids the complication of shear banding that often occurs in attempts to generate yielding of colloidal gels. The gels are comprised of spherical sterically stabilized poly(methyl methacrylate) particles suspended in a density and refractive index matched organic solvent mixture. Because the particles are charged, application of an electric field imposes a force on the gel body that results in homogeneous internal rupture and yielding. After cessation of the electric field, the gel network rapidly reforms. The structure of the reformed gel differs significantly from the one present prior to the application of the electric field. The microstructural changes that accompany the yielding transition are quantified by comparing confocal microscopy image volumes acquired before and after rupture. We find that the local structure of the colloidal gel after recovery, as quantified by the contact number distribution, is negligibly affected by the yielding transition; however, the long-range structure of the gel, as quantified by spatial fluctuations in number density, is significantly impacted. The result highlights the effect of the small number of short-range bond-breaking events that induce the observed changes in collective, long-range structure.
Collapse
Affiliation(s)
- Michael Kogan
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136, USA
| | | |
Collapse
|
27
|
Huh YS, Chung AJ, Cordovez B, Erickson D. Enhanced on-chip SERS based biomolecular detection using electrokinetically active microwells. LAB ON A CHIP 2009; 9:433-9. [PMID: 19156293 PMCID: PMC2718423 DOI: 10.1039/b809702j] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Here we present a novel microfluidic technique for on-chip surface enhanced Raman spectroscopy (SERS) based biomolecular detection, exploiting the use of electrokinetically active microwells. Briefly, the chip comprises of a series of microfluidic channels containing embedded microwells that, when electrically actuated, either locally attract or repulse species from solution through a combination of electrokinetic effects. We demonstrate that the approach combines the advantages of existing homogeneous (solution phase) and heterogeneous (surface phase) on-chip techniques by enabling active mixing to enhance the rate of binding between the SERS enhancers and the biomolecular targets as well as rapid concentration of the product for surface phase optical interrogation. This paper describes the chip design and fabrication procedure, experimental results illustrating the optimal conditions for our concentration and mixing processes, and a numerical analysis of the flow pattern. To demonstrate the usefulness of the device we apply it to the quantitative detection of nucleic acid sequences associated with Dengue virus serotype 2. We report a limit of detection for Dengue sequences of 30 pM and show excellent specificity against other serotypes.
Collapse
Affiliation(s)
- Yun Suk Huh
- Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853, USA.
| | | | | | | |
Collapse
|
28
|
Becker M, Budich C, Deckert V, Janasek D. Isotachophoretic free-flow electrophoretic focusing and SERS detection of myoglobin inside a miniaturized device. Analyst 2009; 134:38-40. [DOI: 10.1039/b816717f] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
29
|
Sueyoshi K, Kitagawa F, Otsuka K. Recent progress of online sample preconcentration techniques in microchip electrophoresis. J Sep Sci 2008; 31:2650-66. [PMID: 18693308 DOI: 10.1002/jssc.200800272] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Microchip electrophoresis (MCE) has been advanced remarkably by the applications of several separation modes and the integration with several chemical operations on a single planer substrate. MCE shows superior analytical performance, e.g., high-speed analysis, high resolution, low consumption of reagents, and so on, whereas low-concentration sensitivity is still one of the major problems. To overcome this drawback, various online sample preconcentration techniques have been developed in MCE over the past 15 years, which have successfully enhanced the detection sensitivity in MCE. This review highlights recent developments in online sample preconcentration in MCE categorized on the basis of "dynamic" and "static" methods. The dynamic techniques including field amplified stacking, ITP, sweeping, and focusing have been easily applied to MCE, which provide effective enrichments of various analytes. The static techniques such as SPE and filtration have also been combined with MCE. In the static techniques, extremely high preconcentration efficiency can be obtained, compared to the dynamic methods. This review provides comprehensive tables listing the applications and sensitivity enhancement factors of these preconcentration techniques employed in MCE.
Collapse
Affiliation(s)
- Kenji Sueyoshi
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan.
| | | | | |
Collapse
|
30
|
|
31
|
Hlushkou D, Dhopeshwarkar R, Crooks RM, Tallarek U. The influence of membrane ion-permselectivity on electrokinetic concentration enrichment in membrane-based preconcentration units. LAB ON A CHIP 2008; 8:1153-62. [PMID: 18584092 DOI: 10.1039/b800549d] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The performance of nanoporous hydrogel microplugs with varying surface charge density is described in concentrating charged analytes electrokinetically in a microfluidic device. A neutral hydrogel plug with a mean pore size smaller than the size of charged analytes acts as a simple size-exclusion membrane. The presence of fixed charges on the backbone of a nanoporous hydrogel creates ion-permselectivity which results in charge-selective transport through the hydrogel. This leads to the development of concentration polarization (CP) in the adjoining bulk electrolyte solutions under the influence of an applied electrical field. CP strongly affects the distribution of the local electrical field strength, in particular, in the vicinity of the hydrogel plug which can significantly reduce the concentration enrichment factors compared to the neutral hydrogel. A theoretical model and simulations are presented, together with experimental data, to explain the interplay of hydrogel or membrane cation-selectivity, electrical field-induced CP, and the distribution of the local electrical field strength with respect to concentration enrichment of negatively charged analytes at the cathodic membrane-solution interface.
Collapse
Affiliation(s)
- Dzmitry Hlushkou
- Institut für Verfahrenstechnik, Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg, Germany
| | | | | | | |
Collapse
|
32
|
Zhang H, Yang X, Wang K, Tan W, Zhou L, Zuo X, Wen J, Chen Y. Detection of single-base mutations using 1-D microfluidic beads array. Electrophoresis 2008; 28:4668-78. [PMID: 18072213 DOI: 10.1002/elps.200700048] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The application of a 1-D microfluidic beads array that is composed of individually addressable functionalized SiO2 beads has been demonstrated for detection of single-base mutations based on "sandwich" hybridization assay without additional sample labeling and PCR amplification. We concentrated on detection of mutations in the human p53 tumor suppressor gene with more than 50% mutation frequency in the known human cancers. Using a microinjection system, functionalized beads could be selectively and linearly arrayed in a single microfluidic channel comprising many periodic chambers. This 1-D microfluidic beads array was sufficiently sensitive to identify single-nucleotide mutations in 40 pM quantities of DNA targets and could discriminate the mutated alleles in an excess of nonmutated alleles at a level of one mutant in 100 wild-type sequences. The surface of beads was regenerated and rehybridized up to six times without obvious loss of signal. The entire reaction process was done at room temperature within minutes, and only 2-10 microL sample solution was needed to complete the whole detection process. The p53 genotypes of A549, CNE2, and SKBr-3 cell lines were also correctly evaluated by using mRNA extracts as target without need for sample labeling and amplification. Thus, this platform enabled rapid and exact discrimination of gene mutations with the advantages of reusability, simple handling of liquid, low cost, and little reagent consumption.
Collapse
Affiliation(s)
- He Zhang
- State Key Laboratory of Chemo/Biosensing & Chemometrics, Biomedical Engineering Center, College of Chemistry & Chemical Engineering, Hunan University, Changsha, Hunan, PR China
| | | | | | | | | | | | | | | |
Collapse
|
33
|
Connatser RM, Cochran M, Harrison RJ, Sepaniak MJ. Analytical optimization of nanocomposite surface-enhanced Raman spectroscopy/scattering detection in microfluidic separation devices. Electrophoresis 2008; 29:1441-50. [DOI: 10.1002/elps.200700585] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
34
|
On-chip oligonucleotide ligation assay using one-dimensional microfluidic beads array for the detection of low-abundant DNA point mutations. Biosens Bioelectron 2008; 23:945-51. [DOI: 10.1016/j.bios.2007.09.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2007] [Revised: 09/07/2007] [Accepted: 09/17/2007] [Indexed: 11/17/2022]
|
35
|
Sarrazin F, Salmon JB, Talaga D, Servant L. Chemical Reaction Imaging within Microfluidic Devices Using Confocal Raman Spectroscopy: The Case of Water and Deuterium Oxide as a Model System. Anal Chem 2008; 80:1689-95. [DOI: 10.1021/ac7020147] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
36
|
Park CC, Kazakova I, Kawabata T, Spaid M, Chien RL, Wada HG, Satomura S. Controlling data quality and reproducibility of a high-sensitivity immunoassay using isotachophoresis in a microchip. Anal Chem 2008; 80:808-14. [PMID: 18173249 DOI: 10.1021/ac701709n] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This report describes a method of controlling the sensitivity and reproducibility of a microchip-based immunoassay by using isotachophoresis to preconcentrate the antigen and antibody prior to binding. Gel electrophoresis separation is coupled to the preconcentration step to separate the immunocomplex products formed. The system employs a quartz-based LabChip that automates the metering, preconcentration, reaction, separation, and detection. The system also uses a handoff mechanism that switches the immunocomplex from the stacking mode to the separation mode. We show that the handoff timing affects the data quality and repeatability of the electropherograms, and we demonstrate an automatic handoff mechanism to precisely control the signal intensity and separation of peaks of interest. In so doing, the automatic handoff mechanism also improves the reproducibility of the assay. When applied to the homogeneous liquid-phase detection of alpha-fetoprotein, a common tumor marker, the system shows a greater than 200-fold stacking of specific analytes of interest.
Collapse
Affiliation(s)
- C Charles Park
- Caliper Life Sciences, Mountain View, California 94043, USA.
| | | | | | | | | | | | | |
Collapse
|
37
|
Harrison SLM, Ivory CF. Prediction of the location of stationary steady-state zone positions in counterflow isotachophoresis performed under constant voltage in a vortex-stabilized annular column. J Sep Sci 2007; 30:3255-61. [PMID: 18008279 PMCID: PMC2921190 DOI: 10.1002/jssc.200700243] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A theoretical model is presented and an analytical expression derived to predict the locations of stationary steady-state zone positions in ITP as a function of current for a straight channel under a constant applied voltage. Stationary zones may form in the presence of a countercurrent flow whose average velocity falls between that of a pure leader zone and of a pure trailer zone. A comparison of model predictions with experimental data from an anionic system shows that the model is able to predict the location of protein zones with reasonable accuracy once the ITP stack has formed. This result implies that an ITP stack can be precisely directed by the operator to specific positions in a channel whence portions of the stack can be removed or redirected for further processing or analysis.
Collapse
Affiliation(s)
- Schurie L M Harrison
- School of Chemical Engineering and Bioengineering, Washington State University, Pullman 99164-2710, USA
| | | |
Collapse
|
38
|
Vickers JA, Dressen BM, Weston MC, Boonsong K, Chailapakul O, Cropek DM, Henry CS. Thermoset polyester as an alternative material for microchip electrophoresis/electrochemistry. Electrophoresis 2007; 28:1123-9. [PMID: 17340646 DOI: 10.1002/elps.200600445] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Microchip CE coupled with electrochemical detection (MCE-EC) is a good method for the direct detection of many small molecule analytes because the technique is sensitive and readily miniaturized. Polymer materials are being increasingly used with MCE due to their affordability and ease of fabrication. While PDMS has become arguably the most widely used material in MCE-EC due to the simplicity of microelectrode incorporation, it suffers from a lack of separation efficiency, lower surface stability, and a tendency for analyte sorption. Other polymers, such as poly(methylmethacrylate) (PMMA) and poly(carbonate) (PC), have higher separation efficiencies but require more difficult fabrication techniques for electrode incorporation. In this report, thermoset polyester (TPE) was characterized as an alternative material for MCE-EC. TPE microchips were characterized in their native and plasma oxidized forms and after coating with polyelectrolyte multilayers (PEMs). TPE provides higher separation efficiencies when compared to PDMS microchips, while still using simple fabrication protocols. In this work, separation efficiencies as high as 295,000 N/m were seen when using TPE MCE-EC devices. Furthermore, the EOF was higher and more consistent as a function of pH for both native and plasma-treated TPE than PDMS. Finally, TPE is amenable to modification using simple PEM coatings as another way to control surface chemistry and surface charge.
Collapse
Affiliation(s)
- Jonathan A Vickers
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | | | | | | | | | | | | |
Collapse
|
39
|
Jung B, Zhu Y, Santiago JG. Detection of 100 aM fluorophores using a high-sensitivity on-chip CE system and transient isotachophoresis. Anal Chem 2007; 79:345-9. [PMID: 17194159 DOI: 10.1021/ac060949p] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present a highly sensitive capillary electrophoresis (CE) assay that combines transient, single-interface on-chip isotachophoresis (ITP) and a laser-induced confocal fluorescence detection setup. We performed experimental parametric studies to show the effects of microscope objective specifications and intensity of excitation laser on optimization of a high-sensitivity on-chip CE detection system. Using the optimized detection system, single-molecule detection of Alexa Fluor 488 was demonstrated, and signal data were validated with autocorrelation analysis. We also demonstrated a separation and detection of 100 aM fluorophores (Alexa Fluor 488 and bodipy) in a fast assay using a high-sensitivity on-chip CE detection system and an ITP/CE protocol with no manual buffer exchange steps. This is, to the knowledge of the authors, the highest electrophoretic separation sensitivity ever reported.
Collapse
Affiliation(s)
- Byoungsok Jung
- Department of Mechanical Engineering, Stanford University, Stanford, California 94305, USA
| | | | | |
Collapse
|
40
|
Chapter 2 Chip Capillary Electrophoresis and Total Genetic Analysis Systems. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/s1871-0069(06)02002-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
41
|
Jung B, Bharadwaj R, Santiago JG. On-Chip Millionfold Sample Stacking Using Transient Isotachophoresis. Anal Chem 2006; 78:2319-27. [PMID: 16579615 DOI: 10.1021/ac051659w] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We present a simple and robust isotachophoresis (ITP) method that can be integrated with microchip-based capillary electrophoresis (CE) devices to achieve millionfold sample stacking. We performed an experimental parametric study to show the effects of initial sample ion concentration, leading ion concentration, and trailing ion concentration on ITP stacking. We also discuss the usefulness and limitations of a simple one-dimensional nondispersive model and a scaling analysis for dispersion rate. We found that a single-column ITP configuration together with electroosmotic flow suppression and high leading ion concentration provide high-performance ITP and can be integrated readily with CE separation. We demonstrated detection of trace of 100 fM Alexa Fluor 488 (signal-to-noise ratio of 11) with a concentration increase of a factor of 2 x 10(6). Application of our ITP/CE protocol to the stacking and separation of negatively charged fluorescent tracers (Alexa Fluor 488 and bodipy) resulted in a concentration increase of 6.4 x 10(4) and a signal increase of 4.5 x 10(5). The ITP/CE protocol can be performed with a standard microchannel cross design or simple flow control. The method can be implemented with available off-the-shelf chip systems using off-the-shelf voltage control systems and buffer chemistries.
Collapse
Affiliation(s)
- Byoungsok Jung
- Department of Mechanical Engineering, and Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA
| | | | | |
Collapse
|
42
|
Chen L, Prest JE, Fielden PR, Goddard NJ, Manz A, Day PJR. Miniaturised isotachophoresis analysis. LAB ON A CHIP 2006; 6:474-87. [PMID: 16572209 DOI: 10.1039/b515551g] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The application of miniaturized total analysis systems (microTAS) has seen rapid development over the past few years. Isotachophoresis (ITP) has been transferred into microchip format for both electrophoretic separation and pretreatment purposes, due to its advantageous features including separation parameters controlled by electrolyte composition and high sample load capacity. The primary focus of this concise review is to summarize the basic features of microchip based ITP and its applications to the analysis and pretreatment of ionic compounds and biomolecules that have arisen since 1998.
Collapse
Affiliation(s)
- Lin Chen
- Institute for Analytical Sciences, Bunsen-Kirchhoff Str. 11, D-44139 Dortmund, Germany
| | | | | | | | | | | |
Collapse
|
43
|
Abstract
There is a great demand in separation technologies for faster and more effective analysis processes. Miniaturization is a suitable technique for satisfying this demand as reduction in size gives increased separation speed with higher efficiency. CEC is an electric-field-mediated separation technique where the liquid flow is generated by the electric field itself. The main advantage of using electric field over pressure for flow generation is the flat flow profile of the EOF; thus, CEC is one of the best candidates to construct a novel and high-efficiency microanalytical device. The aim of the present paper is to review the basic fabrication and bonding principles, as well as connection and system integration options for microfluidics-based electrochromatography. The physical structure and fluidic channel formation are critically evaluated, including glass microstructuring and fusion bonding. Recent developments in nanoflow measurements and the application of various flow control units are also extensively discussed.
Collapse
Affiliation(s)
- László Székely
- Horváth Laboratory of Bioseparation Sciences, Inst. Anal. Chem. Radiochem., University of Innsbruck, Austria
| | | |
Collapse
|
44
|
Abstract
CE on microchip is an emerging separation technique that has attracted wide attention and gained considerable popularity. Because of miniaturization of the separation format, CE on chip typically offers shorter analysis time and lower reagent consumption with potential development of portable analytical instrumentation. This review with 143 references is focused on proteins and peptides analysis, DNA separation including fragment sizing, genotyping, mutation detection and sequencing, and also the analysis of low-molecular-weight compounds, namely explosive residues and warfare agents, pharmaceuticals and drugs of abuse, and various small molecules in body fluids.
Collapse
|
45
|
Dhopeshwarkar R, Sun L, Crooks RM. Electrokinetic concentration enrichment within a microfluidic device using a hydrogel microplug. LAB ON A CHIP 2005; 5:1148-54. [PMID: 16175272 DOI: 10.1039/b509063f] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
A simple and efficient approach for concentration of charged molecules in microfluidic devices is described. The functional component of the system is a hydrogel microplug photopolymerized within the main channel of a microfluidic device. When an appropriately biased voltage is applied across the hydrogel, charged analyte molecules move from the source well toward the hydrogel. Transport of the analyte through the hydrogel is slow compared to its velocity in the microfluidic channel, however, and therefore it concentrates at the hydrogel/solution interface. For an uncharged hydrogel, a bias of 100 V leads to a approximately 500-fold enrichment of the DNA concentration within 150 s, while the same conditions result in an enrichment of only 50-fold for fluorescein. Somewhat lower enrichment factors are observed when a negatively charged hydrogel is used. A qualitative model is proposed to account for the observed behavior.
Collapse
Affiliation(s)
- Rahul Dhopeshwarkar
- Department of Chemical Engineering, Texas A&M University, Mailstop 3122, College Station, TX 77843-3122, USA
| | | | | |
Collapse
|
46
|
Hernández-Borges J, Rodríguez-Delgado MA, García-Montelongo FJ, Cifuentes A. Chiral analysis of pollutants and their metabolites by capillary electromigration methods. Electrophoresis 2005; 26:3799-813. [PMID: 16217833 DOI: 10.1002/elps.200500084] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Chiral separation of enantiomers is one of the most challenging tasks for any analytical technique including CE. Since the first report in 1985 showing the great possibilities of CE for the separation of chiral compounds, the amount of publications concerning this topic has quickly increased. Although chiral electromigration methods have mainly been used for enantioseparation of drugs and pharmaceuticals, they have also been applied to analyze chiral pollutants. This article intends to provide an updated overview, including works published till January 2005, on the principal applications of CE to the chiral analysis of pollutants and their metabolites, with special emphasis on articles published in the last 10 years. The main advantages and drawbacks regarding the use of CE for chiral separation of pollutants are addressed including some discussion on the foreseen trends of electromigration procedures applied to chiral analysis of contaminants.
Collapse
Affiliation(s)
- Javier Hernández-Borges
- Department of Analytical Chemistry, Nutrition and Food Science, University of La Laguna, La Laguna, Tenerife, Spain
| | | | | | | |
Collapse
|
47
|
Affiliation(s)
- Fumihiko KITAGAWA
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University
| | - Koji OTSUKA
- Department of Material Chemistry, Graduate School of Engineering, Kyoto University
| |
Collapse
|
48
|
Connatser RM, Riddle LA, Sepaniak MJ. Metal-polymer nanocomposites for integrated microfluidic separations and surface enhanced Raman spectroscopic detection. J Sep Sci 2004; 27:1545-50. [PMID: 15638165 DOI: 10.1002/jssc.200401886] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The widespread development of microfluidics (microfluidics) has allowed the extension of efficient separations, fluid handling, and hyphenation with many detection modes to a small, portable, highly controllable physico-chemical platform. Surface enhanced Raman spectroscopy (SERS) offers the powerful advantage of obtaining vibrational spectroscopic information about analytes in an aqueous matrix with negligible background. The mating of electrophoretic separations with vibrational spectroscopy on a microfluidic device will allow the chromatographic efficiency of capillary electrophoresis (CE) with the unequivocal analyte "fingerprinting" capability of detailed structural information. By utilizing SERS as a means of detection, this work promises to yield redress for the hindrances of electrophoretic separations, including uncertainty in analyte band identification due to changing migration times as well as compromised detection sensitivity for non-fluorescent analytes. Our work represents the first steps toward developing CE-SERS on a microfluidic platform with a region of novel metal-pliable polymer nanocomposite SERS substrate fabricated directly into the device. The device fabrication material has been extensively employed by the microfluidics community for over five years. SERS detection can be achieved in real time or after the separations, with on-column laser-induced fluorescence employed as a secondary detection mode used for confirmation of efficiencies and band locations.
Collapse
Affiliation(s)
- R Maggie Connatser
- Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600, USA
| | | | | |
Collapse
|
49
|
Hernández-Borges J, Frías-García S, Cifuentes A, Rodríguez-Delgado MA. Pesticide analysis by capillary electrophoresis. J Sep Sci 2004; 27:947-63. [PMID: 15352712 DOI: 10.1002/jssc.200401820] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In this work, a critical and updated revision of the current situation of the analysis of pesticides by Capillary Electrophoresis (CE) is presented. The review has been written in two main sections. The first one presents a thorough revision of the various offline and on-line sample preconcentration procedures that have been used in conjunction with CE to analyze these compounds. The second part reviews the various detection strategies (i.e., UV, LIF, MS, and electrochemical) and CE modes that have been applied to the analysis of pesticides. Future trends that can be expected from this hot research area are also discussed.
Collapse
Affiliation(s)
- J Hernández-Borges
- Department of Analytical Chemistry, Nutrition and Food Science, University of La Laguna, 38071 Tenerife, Spain
| | | | | | | |
Collapse
|
50
|
Baldock SJ, Fielden PR, Goddard NJ, Kretschmer HR, Prest JE, Treves Brown BJ. Novel variable volume injector for performing sample introduction in a miniaturised isotachophoresis device. J Chromatogr A 2004; 1042:181-8. [PMID: 15296404 DOI: 10.1016/j.chroma.2004.05.062] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
A microdevice design furnished with a novel sample injector, capable of delivering variable volume samples, for miniaturised isotachophoretic separations is presented. Micromachining by direct milling was used to realise two flow channel network designs on poly(methyl methacrylate) chips. Both designs comprised a wide bore sample channel interfaced, via a short connection channel, to a narrow bore separation channel. Superior injection performance was observed with a connection channel angled at 45 degrees to the separation channel compared to a device using a channel angled at 90 degrees. Automated delivery of electrolytes to the microdevice was demonstrated with both hydrostatic pumping and syringe pumps; both gave reproducible sample injection. A range of different sampling strategies were investigated. Isotachophoretic separations of model analytes (metal ions and an anionic dye) demonstrated the potential of the device. Separations of ten metal cations were achieved in under 475 s.
Collapse
Affiliation(s)
- S J Baldock
- Department of Instrumentation and Analytical Science, UMIST, PO Box 88, Manchester M60 1QD, UK.
| | | | | | | | | | | |
Collapse
|