1
|
Chu HCW, Garoff S, Tilton RD, Khair AS. Tuning chemotactic and diffusiophoretic spreading via hydrodynamic flows. SOFT MATTER 2022; 18:1896-1910. [PMID: 35188176 DOI: 10.1039/d2sm00139j] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The transport of microorganisms by chemotaxis is described by the same "log-sensing" response as colloids undergoing diffusiophoresis, despite their different mechanistic origins. We employ a recently-developed macrotransport theory to analyze the advective-diffusive transport of a chemotactic or diffusiophoretic colloidal species (both referred to as "colloids") in a circular tube under a steady pressure-driven flow (referred to as hydrodynamic flow) and transient solute gradient. First, we derive an exact solution to the log-sensing chemotactic/diffusiophoretic macrotransport equation. We demonstrate that a strong hydrodynamic flow can reduce spreading of solute-repelled colloids, by eliminating super-diffusion which occurs in an otherwise quiescent system. In contrast, hydrodynamic flows always enhance spreading of solute-attracted colloids. Second, we generalize the exact solution to show that the above tunable spreading phenomena by hydrodynamic flows persist quantitatively for decaying colloids, as may occur with cell death, for example. Third, we examine the spreading of chemotactic colloids by employing a more general model that captures a hallmark of chemotaxis, that log-sensing occurs only over a finite range of solute concentration. Apart from demonstrating for the first time the generality of the macrotransport theory to incorporate an arbitrary chemotactic flow model, we reveal via numerical solutions new regimes of anomalous spreading, which match qualitatively with experiments and are tunable by hydrodynamic flows. The results presented here could be employed to tailor chemotactic/diffusiophoretic colloid transport using hydrodynamic flows, which are central to applications such as oil recovery and bioremediation of aquifers.
Collapse
Affiliation(s)
- Henry C W Chu
- Department of Chemical Engineering, University of Florida, Gainesville, FL 32611, USA.
| | - Stephen Garoff
- Department of Physics and Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Robert D Tilton
- Department of Chemical Engineering, Department of Biomedical Engineering and Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Aditya S Khair
- Department of Chemical Engineering and Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| |
Collapse
|
2
|
Startsev MA, Inglis DW, Baker MS, Goldys EM. Nanochannel pH gradient electrofocusing of proteins. Anal Chem 2013; 85:7133-8. [PMID: 23819922 DOI: 10.1021/ac4014447] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We demonstrate matrix-free pH gradient electrofocusing of proteins within an 85 nm deep nanochannel. In contrast to conventional isoelectric focusing where the fluid does not move, this pH gradient method traps protein molecules flowing through a channel by balancing electric forces due to pH-dependent protein charge and viscous drag forces caused by electro-osmosis. The nanoscale depth of the device and the low voltage used limit convection relative to diffusion, thus producing a stable focused band of protein. R-Phycoerythrin (RPE) and Dylight labeled streptavidin (Dyl-Strep) were focused within a nanochannel using applied voltages between 0.4 and 1.6 V. Concentration enhancement factors of over 380 have been achieved within 5 min. Varying the buffer pH (between 2.7 and 7.2) at the boundaries of the nanochannel affected the shape of the focused bands. For RPE, a pH span of 4.5 (pH 2.7 to 7.2) yielded the narrowest peak while a span of 2.4 (pH 2.7 to 5.1) produced a significantly wider peak. Such matrix-free nanofluidic devices with pH gradient electrofocusing may enable on-chip integration of orthogonal separation techniques with mass spectrometry offering labor savings and enhanced performance.
Collapse
Affiliation(s)
- Michael A Startsev
- Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109, Australia.
| | | | | | | |
Collapse
|
3
|
Hurth C, Gu J, Aboud M, Estes MD, Nordquist AR, McCord B, Zenhausern F. Direct loading of polymer matrices in plastic microchips for rapid DNA analysis: a comparative study. Electrophoresis 2012; 33:2604-11. [PMID: 22899270 DOI: 10.1002/elps.201200148] [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
We report the design and performance validation of microfluidic separation technologies for human identification using a disposable plastic device suitable for integration into an automated rapid DNA analysis system. A fabrication process for a 15-cm long hot-embossed plastic microfluidic devices with a smooth semielliptical cross section out of cyclic olefin copolymer is presented. We propose a mixed polymer solution of 95% w/v hydroxyethylcellulose and 5% w/v polyvinylpyrrolidone for a final polymer concentration of 2.5 or 3.0% to be used as coating and sieving matrix for DNA separation. This formulation allows preparing the microchip without pretreatment in a single-loading step and provides high-resolution separation (≈1.2 bp for fragments <200 bp), which is superior to existing commercial matrices under the same conditions. The hot-embossed device performance is characterized and compared to injection-molded devices made out of cyclic olefin copolymer based on their respective injector geometry, channel shape, and surface charges. Each device design is assessed by fluorescence videomicroscopy to evaluate the formation of injection plugs, then by comparing electropherograms for the separation of a DNA size standard relevant to human identification.
Collapse
Affiliation(s)
- Cedric Hurth
- Center for Applied Nanobioscience and Medicine, The University of Arizona College of Medicine, Phoenix, AZ 85004, USA.
| | | | | | | | | | | | | |
Collapse
|
4
|
Chen Y, Seo TS. PCR-free digital minisatellite tandem repeat genotyping. Electrophoresis 2011; 32:1456-64. [PMID: 21626523 DOI: 10.1002/elps.201100073] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Revised: 03/03/2011] [Accepted: 03/03/2011] [Indexed: 11/11/2022]
Abstract
We demonstrated a proof-of-concept for novel minisatellite tandem repeat typing, called PCR-free digital VNTR (variable number tandem repeat) typing, which is composed of three steps: a ligation reaction instead of PCR thermal cycling, magnetic bead-based solid-phase capture for purification, and an elongated sample stacking microcapillary electrophoresis (μCE) for sensitive digital coding of repeat number. We designed a 16-bp fluorescently labeled ligation probe which is complementary to a repeat unit of a biotinylated synthetic template mimicking the human D1S80 VNTR locus and is randomly hybridized with the minisatellite tandem repeats. A quick isothermal ligation reaction was followed to link the adjacent ligation probes on the DNA templates, and then the ligated products were purified by streptavidin-coated magnetic beads. After a denaturing step, a large amount of ligated products whose size difference was equivalent to the repeat unit were released and recovered. Through the elongated sample stacking μCE separation on a microdevice, the fluorescence signal of the ligated products was generated in the electropherogram and the peak number was directly counted which was exactly matched with the repeat number of VNTR locus. We could successfully identify the minisatellite tandem repeat number with only 5 fmol of DNA template in 30 min.
Collapse
Affiliation(s)
- Yuchao Chen
- Department of Chemical and Biomolecular Engineering (BK21 program) and Institute for the BioCentury, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
| | | |
Collapse
|
5
|
Kong Q, Able RA, Dudu V, Vazquez M. A microfluidic device to establish concentration gradients using reagent density differences. J Biomech Eng 2011; 132:121012. [PMID: 21142326 DOI: 10.1115/1.4002797] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Microfabrication has become widely utilized to generate controlled microenvironments that establish chemical concentration gradients for a variety of engineering and life science applications. To establish microfluidic flow, the majority of existing devices rely upon additional facilities, equipment, and excessive reagent supplies, which together limit device portability as well as constrain device usage to individuals trained in technological disciplines. The current work presents our laboratory-developed bridged μLane system, which is a stand-alone device that runs via conventional pipette loading and can operate for several days without need of external machinery or additional reagent volumes. The bridged μLane is a two-layer polydimethylsiloxane microfluidic device that is able to establish controlled chemical concentration gradients over time by relying solely upon differences in reagent densities. Fluorescently labeled Dextran was used to validate the design and operation of the bridged μLane by evaluating experimentally measured transport properties within the microsystem in conjunction with numerical simulations and established mathematical transport models. Results demonstrate how the bridged μLane system was used to generate spatial concentration gradients that resulted in an experimentally measured Dextran diffusivity of (0.82 ± 0.01) × 10(-6) cm(2)/s.
Collapse
Affiliation(s)
- Qingjun Kong
- Department of Biomedical Engineering, The City College of The City University of New York, Room 403D, Steinman Hall, 160 Convent Avenue, New York, NY 10031, USA
| | | | | | | |
Collapse
|
6
|
Chen Y, Choi JY, Choi SJ, Seo TS. Sample stacking capillary electrophoretic microdevice for highly sensitive mini Y short tandem repeat genotyping. Electrophoresis 2010; 31:2974-80. [PMID: 20715129 DOI: 10.1002/elps.201000270] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Lab-on-a-chip provides an ideal platform for short tandem repeat (STR) genotyping due to its intrinsic low sample consumption, rapid analysis, and high-throughput capability. One of the challenges, however, in the forensic human identification on the microdevice is the detection sensitivity derived from the nanoliter volume sample handling. To overcome such a sensitivity issue, here we developed a sample stacking CE microdevice for mini Y STR genotyping. The mini Y STR includes redesigned primer sequences to generate smaller-sized PCR amplicons to enhance the PCR efficiency and the success rate for a low copy number and degraded DNA. The mini Y STR amplicons occupied in the 5- and 10-mm stacking microchannels are preconcentrated efficiently in a defined narrow region through the optimized sample stacking CE scheme, resulting in more than tenfold improved fluorescence peak intensities compared with that of a conventional cross-injection microcapillary electrophoresis method. Such signal enhancement allows us to successfully analyze the Y STR typing with only 25 pg of male genomic DNA, with high background of female genomic DNA, and with highly degraded male genomic DNA. The combination of the mini Y STR system with the novel sample stacking CE microdevice provides the highly sensitive Y STR typing on a chip, making it promising to perform high-performance on-site forensic human identification.
Collapse
Affiliation(s)
- Yuchao Chen
- Department of Chemical and Biomolecular Engineering (BK21 program) KAIST, 335 Gwahangno, Yuseong-Gu, Daejeon, Republic of Korea
| | | | | | | |
Collapse
|
7
|
Ueberfeld J, Ehrlich DJ. Scaling of nucleic acid assays on microelectrophoresis array devices: High-dynamic range multi-gene readout from less than ten transcripts. Electrophoresis 2009; 30:2090-9. [DOI: 10.1002/elps.200800774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
8
|
Llopis SL, Osiri J, Soper SA. Surface modification of poly(methyl methacrylate) microfluidic devices for high-resolution separations of single-stranded DNA. Electrophoresis 2007; 28:984-93. [PMID: 17309052 DOI: 10.1002/elps.200600435] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
While polymer-based microfluidic devices offer some unique opportunities in developing low-cost systems for a variety of application areas, the ability to sort electrophoretically with high efficiency a number of different targets has remained somewhat elusive with an example consisting of achieving single base resolution as required for DNA sequencing. While the reasons for this are many-fold, it is clear that some type of coating is required on the polymer substrate to suppress the EOF and/or minimize potential solute/wall interactions. To this end, we report on a simple grafting procedure to allow the formation of polymer coats, which in this example used linear polyarcylamides (LPAs), onto a poly(methyl methacrylate) (PMMA) microfluidic device. The procedure involved creating an amine-terminated PMMA surface by appropriately functionalizing the PMMA through either a chemical or photochemical process. The aminated surface could then be used to covalently anchor methacrylic acid, which was used as a scaffold to produce LPAs on the surface through radical polymerization of acrylamide. The resulting surfaces demonstrated EOFs that were nearly an order of magnitude smaller than native PMMA. In addition, these LPA-coated devices could produce highly reproducible migration times of over approximately 20 runs with plate numbers exceeding 10(5) m(-1). Using gel electrophoretic analysis of a single base track generated from an M13mp18 template using Sanger cycle sequencing and dye-primer chemistry, the resolution value obtained for bases 199 and 200 was 0.18 while for bases 208 and 209 it was 0.21. For the native PMMA, these bands were found to comigrate.
Collapse
Affiliation(s)
- Shawn L Llopis
- Department of Chemistry, Department of Mechanical Engineering, Center for BioModular Multi-Scale Systems, Louisiana State University, Baton Rouge, LA 70803, USA
| | | | | |
Collapse
|
9
|
Zhang L, Yin XF. Field amplified sample stacking coupled with chip-based capillary electrophoresis using negative pressure sample injection technique. J Chromatogr A 2006; 1137:243-8. [PMID: 17055523 DOI: 10.1016/j.chroma.2006.10.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Revised: 10/02/2006] [Accepted: 10/04/2006] [Indexed: 11/21/2022]
Abstract
A multi-T microchip for integrated field amplified sample stacking (FASS) with CE separation to increase the chip-based capillary electrophoresis (chip-based CE) sensitivity was developed. Volumetrically defined large sample plug was formed in one step within 5s by the negative pressure in headspace of the two sealed sample waste reservoirs produced using a syringe pump equipped with a 3-way valve. Stacking and separation can proceed only by switching the 3-way valve to release the vacuum in headspace of the two sample waste reservoirs. This approach considerably simplified the operations and the equipments for FASS in chip-based CE systems. Migration time precisions of 3.3% and 1.3% RSD for rhodamine123 (Rh123) and fluorescien sodium salt (Flu) in the separation of a mixture of Flu and Rh123 were obtained for nine consecutive determinations with peak height precisions of 4.8% and 3.4% RSD, respectively. Compared with the chip-based CE on the cross microchip, the sensitivity for analysis of FlTC, FITC-labeled valine (Val) and Alanine (Ala) increased 55-, 41- and 43-fold, respectively.
Collapse
Affiliation(s)
- Lei Zhang
- Institute of Microanalytical Systems, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | | |
Collapse
|
10
|
El-Difrawy SA, Srivastava A, Gismondi EA, McKenna BK, Ehrlich DJ. Numerical model for DNA loading in microdevices: Stacking and autogating effects. Electrophoresis 2006; 27:3779-87. [PMID: 16960830 DOI: 10.1002/elps.200600088] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Many electrophoresis-based DNA sequencing and genotyping microdevices rely on field-driven effects to load and preconcentrate the sample. A quantitative model is developed for a broad class of electrophoresis-based microfabricated sample injectors. Quantitative predictions of DNA preconcentration are compared with experimental data and are shown to qualitatively reproduce the detailed time-evolving sample distribution in the injector. The model provides practical guidance on device and protocol design, in order to optimize this critical aspect of microfluidic devices.
Collapse
|
11
|
Ueberfeld J, El-Difrawy SA, Ramdhanie K, Ehrlich DJ. Solid-Support Sample Loading for DNA Sequencing. Anal Chem 2006; 78:3632-7. [PMID: 16737217 DOI: 10.1021/ac052201x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present a new method for simplified low-quantity DNA loading onto microelectrophoresis devices. The method is based on combined solid-phase extraction, purification, and transport of DNA reversibly bound on paramagnetic microspheres. DNA is adsorbed onto the microspheres, captured with a magnetized permalloy wire, and then directly injected as a highly focused sample plug into the separation channel. This method circumvents both the minimum volume requirement of pipettors (since only solid beads are transported) and the timing complications of double-T microfluidic injection. Injections from Sanger samples of <100 pg total suspended weight match the signal strength of our previous conventional injections at >10-times the starting DNA sample. Sequencing traces show a resolution that matches or exceeds double-T injections. A kinetic model reproduces the time-dependence of the injection signals and proves that total nonidealities in the method produce injection-broadened plugs of approximately 1-s duration. The method should be broadly extendable to DNA and protein separations in both microdevice and capillary electrophoresis.
Collapse
Affiliation(s)
- Jörn Ueberfeld
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, Massachusetts 02142, USA
| | | | | | | |
Collapse
|
12
|
Goedecke N, McKenna B, El-Difrawy S, Gismondi E, Swenson A, Carey L, Matsudaira P, Ehrlich DJ. Microdevice DNA forensics by the simple tandem repeat method. J Chromatogr A 2005; 1111:206-13. [PMID: 16569579 DOI: 10.1016/j.chroma.2005.05.100] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Revised: 05/23/2005] [Accepted: 05/25/2005] [Indexed: 11/16/2022]
Abstract
We review recent experiments on DNA forensics by the simple tandem repeat (STR) method using a 16-lane micromachined device as the active separation element. Separations by linear polyacrylamide matrices show very high data quality metrics when evaluated with statistically significant data sets. Full 16-locus multiplexes are verified on the multilane system. Multi-donor mixed samples are studied in the context of the limits of the laser-induced fluorescence detector and data-reduction software. The microdevice appears to be posed to outperform current capillary arrays in terms of stability and, through specialized sample loading, in the interpretation of complex mixtures.
Collapse
Affiliation(s)
- Nils Goedecke
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, MA 02142-1479, USA
| | | | | | | | | | | | | | | |
Collapse
|
13
|
Lin R, Burke DT, Burns MA. Addressable Electric Fields for Size-Fractioned Sample Extraction in Microfluidic Devices. Anal Chem 2005; 77:4338-47. [PMID: 16013844 DOI: 10.1021/ac048132o] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fraction collection following electrophoresis is of major importance for a variety of biological analyses. These assays typically need to identify specific fractions in the separated sample for further processing and require extraction of one or a group of fragments. In this paper, we have developed and characterized a technique to generate addressable electric fields for improved extraction during electrophoresis in microfluidic devices. The addressable electric field is achieved by applying a low bias voltage (1-2 V) to microelectrode pairs within the electrophoresis microchannel. Theoretical analysis shows the purity of the extracted sample can be improved as much as 30% over extraction without the shaped electric fields, and nearly 100% predicted yield can be achieved. We also describe the theoretical design of shaped electric fields by characterizing the optimal electrode geometry, field strength, channel configuration, and electrophoretic migration behavior needed for efficient band extraction.
Collapse
Affiliation(s)
- Rongsheng Lin
- Department of Chemical Engineering, The University of Michigan, Ann Arbor, Michigan 48109-2136, USA
| | | | | |
Collapse
|
14
|
Srivastava A, Metaxas AC, So P, Matsudaira P, Ehrlich D, Georghiou GE. Numerical simulation of DNA sample preconcentration in microdevice electrophoresis. Electrophoresis 2005; 26:1130-43. [PMID: 15704245 DOI: 10.1002/elps.200406192] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A numerical model is presented for the accurate and efficient prediction of preconcentration and transport of DNA during sample introduction and injection in microcapillary electrophoresis. The model incorporates conservation laws for the different buffer ions, salt ions, and DNA sample, coupled through a Gaussian electric field to account for the field modifications that cause electromigration. The accuracy and efficiency required to capture the physics associated with such a complex transient problem are realized by the use of the finite element-flux corrected transport (FE-FCT) algorithm in two dimensions. The model has been employed for the prediction of DNA sample preconcentration and transport during electrophoresis in a double-T injector microdevice. To test its validity, the numerical results have been compared with the corresponding experimental data under similar conditions, and excellent agreement has been found. Finally, detailed results from a simulation of DNA sample preconcentration in electrophoretic microdevices are presented using as parameters the electric field strength and the other species concentrations. The effect of the Tris concentration on sample stacking is also investigated. These results demonstrate the great potential offered by the model for future optimization of such microchip devices with respect to significantly enhanced speed and resolution of sample separation.
Collapse
Affiliation(s)
- Alok Srivastava
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | | | | | | | | | | |
Collapse
|
15
|
Fluorescence detection in capillary electrophoresis. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/s0166-526x(05)45006-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
16
|
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
|
17
|
Ugaz VM, Elms RD, Lo RC, Shaikh FA, Burns MA. Microfabricated electrophoresis systems for DNA sequencing and genotyping applications: current technology and future directions. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2004; 362:1105-29. [PMID: 15306487 DOI: 10.1098/rsta.2003.1365] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Many routine genomic-analysis assays rely on gel electrophoresis to perform size-selective fractionation of DNA fragments in the size range below 1 kb in length. Over the past decade, impressive progress has been made towards the development of microfabricated electrophoresis systems to conduct these assays in a microfluidic lab-on-a-chip format. Since these devices are inexpensive, require only nanolitre sample volumes, and do not rely on the availability of a pre-existing laboratory infrastructure, they are readily deployable in remote field locations for use in a variety of medical and biosensing applications. The design and construction of microfabricated electrophoresis devices poses a variety of challenges, including the need to achieve high-resolution separations over distances of a few centimetres or less, and the need to easily interface with additional microfluidic components to produce self-contained integrated DNA-analysis systems. In this paper, we review recent efforts to develop devices to satisfy these requirements and live up to the promise of fulfilling the growing need for inexpensive portable genomic-analysis equipment.
Collapse
Affiliation(s)
- Victor M Ugaz
- Department of Chemical Engineering, Texas A&M University, College Station, TX 77843, USA
| | | | | | | | | |
Collapse
|
18
|
Lee NY, Yamada M, Seki M. Pressure-Driven Sample Injection with Quantitative Liquid Dispensing for On-Chip Electrophoresis. ANAL SCI 2004; 20:483-7. [PMID: 15068292 DOI: 10.2116/analsci.20.483] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A novel pressure-driven sample injection method was developed as an alternative to electrokinetic injection, and electrophoretic separation was carried out on a microfabricated device employing this method. This method enables a defined volume of liquid dispensing, followed by instantaneous injection driven by pneumatic pressure, greatly simplifying the injection procedure. A particular microstructure, called a "metering chamber", has been designed for the quantitative dispensing of an ultra-low volume of sample liquid; a "hydrophobic passive valve" equipped with an air vent channel is employed for injecting a dispensed sample into the separation channel. The reproducibility of dispensing was 3.3% (n = 15), expressed by the variation of dispensed volumes. The electrophoretic separation of DNA fragments was performed using this injection method, varying the injection volumes from 0.45 to 4.0 nL, and the separation efficiencies were compared. This precise injection method, easily variable in injection volumes, is highly suitable for quantitative as well as qualitative electrophoretic analyses.
Collapse
Affiliation(s)
- Nae Yoon Lee
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | | | | |
Collapse
|
19
|
Abstract
DNA separation is important for numerous applications in biotechnology and medicine. Efforts to improve DNA separation in microdevices have led to advances in capillary electrophoresis and the development of novel separation strategies. Current research on microcapillary electrophoresis materials is focused on the development of separation matrices with low injection viscosities and wall-coating capabilities. Microcapillary injector geometries are being designed to allow increased control of sample plug volumes. Novel separation strategies using entropic traps, arrays of pillars and Brownian ratchets are also being developed.
Collapse
Affiliation(s)
- Randolph Ashton
- Howard P. Isermann Department of Chemical Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180, USA.
| | | | | |
Collapse
|
20
|
|
21
|
Dang F, Zhang L, Jabasini M, Kaji N, Baba Y. Characterization of electrophoretic behavior of sugar isomers by microchip electrophoresis coupled with videomicroscopy. Anal Chem 2003; 75:2433-9. [PMID: 12918987 DOI: 10.1021/ac034110a] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The electrophoretic behavior of oligosaccharide isomers was investigated by microchip electrophoresis (micro-CE) coupled with videomicroscopy using maltose, cellobiose, maltriose, and panose as oligosaccharide isomer models. The present study revealed for the first time that the formation of a carbohydrate-phosphate complex is a pH-independent rapid process, whereas the formation of a carbohydrate-borate complex is a highly pH-dependent slow process. As a result, phosphate buffer gave much better separation on oligosaccharide isomers than borate and borate-Tris buffers over a wide pH range in micro-CE. The imaging analysis of the complete process of sample loading and injection with field-amplified stacking (FAS) demonstrated that FAS could be used as an efficient method for manipulating the shape of injected sample plugs, and thus improving the performance of micro-CE in the absence of electroosmotic flow. However, once the ionic strength mismatch between sample and running buffer reached a critical threshold, a further increase in ionic strength mismatch deteriorated the effect of FAS, resulting in a surprising decrease in separation efficiency and peak distortion. Under optimal conditions, high-resolution separation of some oligosaccharide isomers and a complex oligosaccharide mixture released from ribonuclease B was achieved using PMMA microchips with an effective separation channel of 30 mm.
Collapse
Affiliation(s)
- Fuquan Dang
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, The University of Tokushima, CREST, Japan Science and Technology Corporation, Shomachi, Tokushima 770-8505, Japan.
| | | | | | | | | |
Collapse
|