Microchip isoelectric focusing using a miniature scanning detection system

Raisi, Fariba; Belgrader, Phillip; Borkholder, David A.; Herr, Amy E.; Kintz, Gregory J.; Pourhamadi, Farzad; Taylor, Michael T.; Northrup, M. Allen

doi:10.1002/1522-2683(20017)22:11<2291::aid-elps2291>3.0.co;2-a

Cited by 43 publications

(27 citation statements)

References 13 publications

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“…We present evidence that the observed flow reversal is due to local changes in electroendosmotic and electrophoretic velocities due to the formation of a pH gradient in the capillary from an electrolysis reaction at the electrodes [12,13]. At the anode end of the capillary, pH drops so low that the surface charge either becomes neutral or changes sign [14].…”

Section: Introductionmentioning

confidence: 99%

Electrokinetic transport of red blood cells in microcapillaries

2002

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Electrokinetic flow of a suspension of erythrocytes (red blood cells, RBCs) in 20 num cylindrical fused-silica capillaries is examined in the present work. Flow direction anomalies are observed experimentally and tentatively explained by the development of a pH gradient between the cathode well and the anode well due to electrolysis reactions at the electrodes. This pH gradient alters the local zeta potentials of both the capillary and the RBC and thus the local electroendosmotic liquid flow (EOF) velocities and RBC electrophoretic (EP) velocities. The two velocities are opposite in direction but with EOF dominating such that the RBC moves toward the cathode, opposite to the anode migration observed in bulk conditions. The opposing zeta potentials also lead to RBC aggregation at the anode end for low fields less than 25 V/cm. As the electroendosmotic velocity decreases at the anode end due to decreasing pH, pressure-driven back flow develops to oppose the original EOF at the remaining portions of the capillary ensuring constant fluid flux. When the anode EOF velocity is smaller in magnitude than the EP velocity, reversal of blood cell transport is observed after a short transient time in which a pH gradient forms. RBC velocities and pH dependencies on electric field and MgCl(2) concentration are presented along with data showing the accumulation of charge separation across the capillary. Also, a short-term solution to the pH gradient formation is presented that could help thwart development of pH gradients in micro-devices at lower voltages.

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Section: Introductionmentioning

confidence: 99%

Electrokinetic transport of red blood cells in microcapillaries

2002

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“…In conventional CIEF, however, the focused analytes must be transported toward a detection window, which can sometimes decrease the resolution due to a band broadening during transportation [5]. Recently, many IEF techniques using microfluidic devices (microfluidic IEF, MIEF) have been developed to overcome this drawback [6][7][8][9][10][11][12]. MIEF has many advantages compared to CIEF, including a short analysis time (within 5 min) due to a short separation channel (several cm) and the requirement of a minimal amount of reagents and samples (several L).…”

Section: Introductionmentioning

confidence: 87%

“…MIEF has many advantages compared to CIEF, including a short analysis time (within 5 min) due to a short separation channel (several cm) and the requirement of a minimal amount of reagents and samples (several L). In particular, a short separation length in MIEF makes whole-column imaging possible, which enables real-time observation of an IEF process over the whole length of the microchannel without the requirement of any of the transportation processes necessary for conventional CIEF [9][10][11][12]. More recently, a microfluidic device for two-dimensional electrophoresis was independently developed by Kim and Moon and Yang et al to obtain a higher resolution for analyzing a complicated mixture of biogenic samples [13,14].…”

Section: Introductionmentioning

confidence: 99%

A Simple and Easy-to-Use Capillary Isoelectric Focusing Technique Using Reagent-Release Hydrogels

et al. 2017

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Reagent-release hydrogels containing an acid or a base solution were prepared and employed as ion suppliers in isoelectric focusing using short capillaries. In conventional isoelectric focusing techniques using microfluidic channels, complicated liquid manipulations are required, which can decrease analytical performance such as the reproducibility of a focusing position. To develop a rapid and sensitive assay based on microfluidic isoelectric focusing, we previously prepared reagent-release capillaries retaining ampholytes by physical adsorption on the inner surface of a short capillary, which were then applied to isoelectric focusing. In this study, reagent-release hydrogels containing an acid or a base solution were developed for isoelectric focusing using short capillaries in place of the acid and base solutions used in conventional microfluidic isoelectric focusing. The prepared reagent-release hydrogels showed some advantages for isoelectric focusing, e.g., high durability for at least five weeks of storage, easy handling as compared to the conventional solutions, and suppression of hydrodynamic flow in capillaries, which often decreases the reproducibility in capillary isoelectric focusing. The migration behavior of ions from the hydrogels into the capillary and the formation of a pH gradient in isoelectric focusing using the reagent-release hydrogels were investigated, which confirmed that the prepared reagent-release hydrogels could form a similar pH gradient to that obtained with conventional capillary isoelectric focusing using the solutions.

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“…Raisi et al [33] discuss their system which consisted of a 60 mm long channel; analysis of peptides was achieved in 5 min. Capillary isoelectric focussing (CIEF) is useful for the study of protein-protein interactions.…”

Section: Capillary Isoelectric Focussingmentioning

confidence: 99%

Review on the development of truly portable andin-situcapillary electrophoresis systems

Lewis

Cranny

Harris

et al. 2013

Meas. Sci. Technol.

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Capillary electrophoresis (CE) is a technique which uses an electric field to separate a mixed sample into its constituents. Portable CE systems enable this powerful analysis technique to be used in the field. Many of the challenges for portable systems are similar to those of autonomous in-situ analysis and therefore portable systems may be considered a stepping stone towards autonomous in-situ analysis. CE is widely used for biological and chemical analysis and example applications include: water quality analysis; drug development and quality control; proteomics and DNA analysis; counter-terrorism (explosive material identification) and corrosion monitoring. The technique is often limited to laboratory use, since it requires large electric fields, sensitive detection systems and fluidic control systems. All of these place restrictions in terms of: size, weight, cost, choice of operating solutions, choice of fabrication materials, electrical power and lifetime. In this review we bring together and critique the work by researchers addressing these issues. We emphasize the importance of a holistic approach for portable and in-situ CE systems and discuss all the aspects of the design. We identify gaps in the literature which require attention for the realization of both truly portable and in-situ CE systems.

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Microchip isoelectric focusing using a miniature scanning detection system

Cited by 43 publications

References 13 publications

Electrokinetic transport of red blood cells in microcapillaries

Electrokinetic transport of red blood cells in microcapillaries

A Simple and Easy-to-Use Capillary Isoelectric Focusing Technique Using Reagent-Release Hydrogels

Review on the development of truly portable andin-situcapillary electrophoresis systems

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