Microchip Capillary Electrophoresis System Research Articles

Research progress on analysis of human papillomavirus by microchip capillary electrophoresis

Human papillomavirus (HPV), is a common spherical DNA virus that can lead to six types of cancers later in life, which has recently garnered human's attention. Microchip capillary electrophoresis (MCE) has provided simple, fast, portable, and sensitive HPV typing assay assisted by a variety of signal amplification technologies. This review presents the latest research progress of MCE in routine HPV typing assays, including both of the MCE techniques and MCE combined with the nucleic acid amplification techniques for HPV assay. The introduction on the former part concerns the MCE system, the MCE chips design and electrophoretic separation methods. The typical MCE system includes high voltage power supply, microfluidic chip of separation, sample injection, electrolyte cell, detection unit and so on. Four different chips are reviewed, containing straight separation channel, T-channel, serpentine channel and dual channel, because these microchips are the most used in the last decade. Furthermore, the high integration and high throughput on a single chip are often integrated the sample preparation unit on a chip. The advantages and disadvantages of different designed microchips are introduced at the same time. The separation methods of chip electrophoresis are briefly introduced. With the development and application of MCE for HPV detection, the separation time is greatly shortened from a few hours to several minutes. The review on the second part gives the comments on various kinds of nucleic acid amplification technologies coupled with MCE for HPV assay. Firstly, the comparative analysis is given on the polymerase chain reaction (PCR) combined with MCE, loop-mediated isothermal amplification (LAMP), PCR combined with restriction fragment length polymorphism (RFLP) for HPV DNA detection, and nucleic acid sequence based amplification (NASBA) for the detection of HPV mRNA, nested PCR and so on. Secondly, the reviews on the other methods beside MCE are also summarized, including the PCR coupled with Fourier transform-infrared spectroscopy (FT-IR spectroscopy), nanotechnology, DNA probes combined with electrochemical methods, reductive Cu(Ⅰ) particles catalyzed Zn-doped MoS2 quantum dots and T7 exonuclease with electrochemiluminescence, LAMP with CRISPR/Cas12a based lateral. In these non-MCE methods, the electrochemical sensing, e. g., impedimetric detection, pulse voltammetry method and flow biosensor, is an ideal method due to its low background signal and excellent time control ability. Finally, although MCE technologies have been developed and the developed instruments are applied in recent years, there are still some challenges in MCE techniques, methods and applications. The first challenge faced in the application of MCE technique in HPV typing assay is that the MCE device can not be well utilized for the detection of HPV with high resolution and high sensitivity, because MCE can not do signal amplification of HPV nucleic acid. The second challenge is that even though some researchers have successfully integrated PCR and MCE on one chip, the technique still faces difficulty for wide application and there is still no really integrated PCR-MCE chip for HPV detection. The third one is the MCE technique is lack for the manufacture of miniaturized and automatic instrument. At the end of review, the authors' insights are given on the development of automatic, fast, high stable and reliable detection in the HPV typing via the portable MCE device.

Quantitative determination of dopamine in single rat pheochromocytoma cells by microchip electrophoresis with only one high-voltage power supply.

We developed a method for the direct identification of dopamine in single cultured rat pheochromocytoma cells by capillary electrophoresis using an end-channel carbon fiber nanoelectrode amperometric detector. The operation mode was designed to achieve single-cell injection and lysis in microfluidic chip electrophoresis with only one high-voltage power supply. The separation and detection conditions were optimized. Four catecholamines were baseline-separated and determined with this system, and the cell density and liquid height of the reservoirs were accommodated for single cell loading, docking and analysis. The microchip capillary electrophoresis system was successfully applied to determine dopamine in single cultured rat pheochromocytoma cells.

Automation Highlights from the Literature

Automation Highlights from the Literature

Fully automated sample preparation microsystem for genetic testing of hereditary hearing loss using two-color multiplex allele-specific PCR.

A fully automated microsystem consisting of a disposable DNA extraction and PCR microchip, as well as a compact control instrument, has been successfully developed for genetic testing of hereditary hearing loss from human whole blood. DNA extraction and PCR were integrated into a single 15-μL reaction chamber, where a piece of filter paper was embedded for capturing genomic DNA, followed by in-situ PCR amplification without elution. Diaphragm microvalves actuated by external solenoids together with a "one-way" fluidic control strategy operated by a modular valve positioner and a syringe pump were employed to control the fluids and to seal the chamber during thermal cycling. Fully automated DNA extractions from as low as 0.3-μL human whole blood followed by amplifications of 59-bp β-actin fragments can be completed on the microsystem in about 100 min. Negative control tests that were performed between blood sample analyses proved the successful elimination of any contamination or carryover in the system. To more critically test the microsystem, a two-color multiplex allele-specific PCR (ASPCR) assay for detecting c.176_191del16, c.235delC, and c.299_300delAT mutations in GJB2 gene that accounts for hereditary hearing loss was constructed. Two allele-specific primers, one labeled with TAMRA for wild type and the other with FAM for mutation, were designed for each locus. DNA extraction from blood and ASPCR were performed on the microsystem, followed by an electrophoretic analysis on a portable microchip capillary electrophoresis system. Blood samples from a healthy donor and five persons with genetic mutations were all accurately analyzed with only two steps in less than 2 h.

Microchip capillary electrophoresis based electroanalysis of triazine herbicides.

The number of pesticides used in agriculture is increasing steadily, leading to contamination of soil and drinking water. Herein, we present a microfluidic platform to detect the extent of contamination in soil samples. A microchip capillary electrophoresis system with in-channel electrodes was fabricated for label-free electroanalytical detection of triazine herbicides. The sample mixture contained three representative triazines: simazine, atrazine and ametryn. The electropherogram for each individual injection of simazine, atrazine and ametryn showed peaks at 58, 66 and 72 s whereas a mixture of them showed distinct peaks at 59, 67 and 71 s respectively. The technique as such may prove to be a useful qualitative and quantitative tool for the similar environmental pollutants.

Low electric field DNA separation and in-channel amperometric detection by microchip capillary electrophoresis.

Miniaturisation of microchip capillary electrophoresis (MCE) is becoming an increasingly important research topic, particularly in areas related to micro total analysis systems or lab on a chip. One of the important features associated with the miniaturised MCE system is the portable power supply unit. In this work, a very low electric field MCE utilising an amperometric detection scheme was designed for use in DNA separation. The device was fabricated from a glass/polydimethylsiloxane hybrid engraved microchannel with platinum electrodes sputtered onto a glass substrate. Measurement was based on a three-electrode arrangement, and separation was achieved using a very low electric field of 12 V/cm and sample volume of 1.5 µl. The device was tested using two commercial DNA markers of different base pair sizes. The results are in agreement with conventional electrophoresis, but with improved resolution. The sensitivity consistently higher than 100 nA, and the separation time approximately 45 min, making this microchip an ideal tool for DNA analysis.

Polymeric Microchip for the Simultaneous Determination of Anions and Cations by Hydrodynamic Injection Using a Dual-Channel Sequential Injection Microchip Electrophoresis System

A dual-channel sequential injection microchip capillary electrophoresis system with pressure-driven injection is demonstrated for simultaneous separations of anions and cations from a single sample. The poly(methyl methacrylate) (PMMA) microchips feature integral in-plane contactless conductivity detection electrodes. A novel, hydrodynamic "split-injection" method utilizes background electrolyte (BGE) sheathing to gate the sample flows, while control over the injection volume is achieved by balancing hydrodynamic resistances using external hydrodynamic resistors. Injection is realized by a unique flow-through interface, allowing for automated, continuous sampling for sequential injection analysis by microchip electrophoresis. The developed system was very robust, with individual microchips used for up to 2000 analyses with lifetimes limited by irreversible blockages of the microchannels. The unique dual-channel geometry was demonstrated by the simultaneous separation of three cations and three anions in individual microchannels in under 40 s with limits of detection (LODs) ranging from 1.5 to 24 μM. From a series of 100 sequential injections the %RSDs were determined for every fifth run, resulting in %RSDs for migration times that ranged from 0.3 to 0.7 (n = 20) and 2.3 to 4.5 for peak area (n = 20). This system offers low LODs and a high degree of reproducibility and robustness while the hydrodynamic injection eliminates electrokinetic bias during injection, making it attractive for a wide range of rapid, sensitive, and quantitative online analytical applications.

Integration of amperometric sensors for microchip capillary electrophoresis application

Capillary electrophoresis is a technique for the separation and analysis of chemical compounds. Techniques adopted from the microchip technology knowledge have led to recent developments of electrophoresis system with integration on microchip. Microchip Capillary Electrophoresis (μCE) systems offer a series of advantages as easy integration for Lab-on-a-chip applications, high performance, portability, speed, minimal solvent and sample requirements. A new technological challenge aims at the development of an economic modular microchip capillary electrophoresis systems using separable and independent units concerning the sensor. In this project we worked on the development of an interchangeable amperometric sensor in order to provide a solution to such electrode passivation and facilitating the use of tailored sensors for specific analyte detection besides. Fluidic chips have been machined from cyclic olefin polymer pallets (Zeonor®) using a micro-injection molding machine.

3-D Simulation of Electroosmotic Injection and Migration in Microchannels: Effects of Non-Rectangular Cross Section

A numerical study of the 3-D characteristics of electroosmotic injection and migration of sample species in microchip capillary electrophoresis systems is reported. In particular, the effect of a non-rectangular cross section commonly found in isotropically-etched microchannels is thoroughly investigated through 3-D numerical simulations. A non-rectangular cross section resulted in a vertically non-uniform sample plug during the loading stage. Conventional 2-D simulation approach can result in up to 40% errors in the calculation of injection qualities. It was also found that the 2-D simulation using a proper channel width has a good agreement with the 3-D simulation data.

Cover Picture: Electrophoresis 21'2010

AbstractIssue no. 22 is a special issue on “Miniaturization” and comprises 21 contributions 3 of them are Fast Track contributions. The other 18 manuscripts are distributed over 3 distinct parts. Part I is on Fundamentals and has 5 research articles on various aspects of fundamentals including gradient elution moving boundary electrophoresis, influence of cross‐sectional area and zeta potential on separations in hybrid‐chip‐based electrophoresis, collision of DNA with nanowires, and retention modeling for solid microfabricated pillar columns. Part II is on New Technology, and contains 9 full research articles. Various innovative applications are described in 4 research articles making up Part III of the issue.FAST TRACK articles:Electrothermal flow effects in insulating (electrodeless) dielectrophoresis systems (10.1002/elps.201000429))Characterization of particle capture in a sawtooth patterned insulating electrokinetic microfluidic device (10.1002/elps.201000438))Analysis of carbonaceous biomarkers with the Mars Organic Analyzer microchip capillary electrophoresis system: Aldehydes and ketones (10.1002/elps.201000424))

Building Exposure Biology Centers to Put the E into “G × E” Interaction Studies

Building Exposure Biology Centers to Put the E into “G × E” Interaction Studies

Development of an On-site Measurement System for Salivary Stress-related Substances Based on Microchip Capillary Electrophoresis Technology

Psychological stress is of major importance to all age groups in recent years, and may lead to mental disorder and various diseases. An objective and quantitative method for measuring salivary stress-related substances is highly desired because saliva collection is easy, stress free and noninvasive. We have developed a rapid and easy-to-use analytical tool for the measurement of cortisol and secretory immunoglobulin A (sIgA) based on microchip technology, immunoselectivity and electrophoretic separation technique. Performing immunoreaction and capillary electrophoresis (CE) separation on microchips is a promising technique for on-site determination of biogenic substances, and has a few advantages over conventional immunoassay methods: reduced sample size, shortening analysis times, high separation efficiency, reduced cost, and downsizing of analytical system. At this stage of our research, some preliminary prototypes of a high-sensitive microchip CE instrument were constructed to determine the stress-related substances in real saliva samples. However, there is not enough detection sensitivity for cortisol analysis. On the other hand, sIgA was successfully analyzed using a laboratory-built microchip CE system and optimal analytical conditions. The sIgA determination is rapid compared with a conventional immunoassay method, and provides an acceptable degree of repeatability and recovery. In the future, microchip technologies will enable total automation and integration of sample preparation. This research has widespread future potential for monitoring multiple stress-related markers within minutes from a trace of saliva, and can contribute to disease prevention and overall good health.

Analysis of Neuroactive Amines in Fermented Beverages Using a Portable Microchip Capillary Electrophoresis System

A portable microfabricated capillary electrophoresis (CE) instrument is used for the determination of neurologically active biogenic amines, especially tyramine and histamine, in fermented beverages. The target molecules are labeled on their primary amino groups with fluorescamine in a 10-min reaction, and the samples analyzed directly, producing a detailed electropherogram in only 120 s on a microfabricated glass CE device containing 21.4-cm-long separation channels. Tyramine was found mainly in red wines at <1-3.4 mg/L, while the histamine content of these samples ranged from 1.8 to 19 mg/L. The highest levels of histamine (20-40 mg/L) were found in sake. The analysis of samples drawn from grape crush through malolactic fermentation in four varieties of zinfandel red wines revealed that histamine and tyramine are produced during yeast and malolactic fermentation, respectively. Following malolactic fermentation, the histamine content in these samples ranged from 3.3 to 30 mg/L, and the tyramine content ranged from 1.0 to 3.0 mg/L. This highly sensitive and rapid lab-on-a-chip analysis method establishes the feasibility of monitoring neurologically active amine content and potentially other chemically and allergenically important molecules in our food supply.

Microchip Capillary Electrophoresis for Point-of-Care Analysis of Lithium

Microchip capillary electrophoresis (CE) is a promising method for chemical analysis of complex samples such as whole blood. We evaluated the method for point-of-care testing of lithium. Chemical separation was performed on standard glass microchip CE devices with a conductivity detector as described in previous work. Here we demonstrate a new sample-to-chip interface. Initially, we took a glass capillary as a sample collector for whole blood from a finger stick. In addition, we designed a novel disposable sample collector and tested it against the clinical standard at the hospital (Medisch Spectrum Twente). Both types of collectors require < 10 microL of test fluid. The collectors contain an integrated filter membrane, which prevents the transfer of blood cells into the microchip. The combination of such a sample collector with microchip CE allows point-of-care measurements without the need for off-chip sample treatment. This new on-chip protocol was verified against routine lithium testing of 5 patients in the hospital. Sodium, lithium, magnesium, and calcium were separated in < 20 s. The detection limit for lithium was 0.15 mmol/L. The new microchip CE system provides a convenient and rapid method for point-of-care testing of electrolytes in serum and whole blood.

Highly sensitive fluorescence detection with Hg-lamp and photon counter in microchip capillary electrophoresis

A microchip capillary electrophoresis system with highly sensitive fluorescence detection is reported. The system was successfully constructed using an inverted fluorescence microscope, a highly sensitive photon counter, a photomultiplier tube (PMT) and a capillary electrophoresis microchip. This system can be applied to the fluorescence detection with various wavelengths (300–600 nm). Different fluorescence reagents require different excitation wavelengths. The wavelengths of UV light (300–385 nm), blue light (450–480 nm) and green light (530–550 nm) are employed to excite Titan yellow, fluorescence-5-isothiocyanate (FITC) and Rhodamine 6G, respectively. The detection limit (S/N = 3) of FITC is 7 × 10 −10 M, which is 2–3 orders of magnitude lower than that obtained with the lamp-based fluorescence and PMT detection system and approaches the data gained by the laser-induced fluorescence detection. The linear relationship is excellent within the range of concentration 1.3 × 10 −9 to 6.5 × 10 −8 M FITC. It offers a new method to widen the application of the lamp-based fluorescence detection.

Chemiluminescence detection for capillary electrophoresis and microchip capillary electrophoresis

Capillary electrophoresis (CE) has become a very important micro-analytical method in many fields, such as biology, biomedicine, and environmental and food sciences. However, the small injection volume makes it a challenge to achieve high-sensitivity detection. CE and microchip capillary electrophoresis (MCE) coupled with chemiluminescence (CL) detection have certain advantages from combining the high separation efficiency of CE with the high sensitivity of CL. To date, CE-CL and MCE-CL systems have been used successfully for separating metal ions, amino acids, biomarkers, and bio-macromolecules, such as proteins, enzymes and DNA fragments. In this article, we give an overview on the methodological aspects of CL detection with CE and MCE systems, summarize key applications, and discuss future prospects.

Rapid Separation of Microorganisms by Quartz Microchip Capillary Electrophoresis

We developed and optimized a system coupling microchip capillary electrophoresis (MCE) and laser-induced fluorescence (LIF) detection for the analysis of microorganisms. The MCE-LIF system successfully separated pure cultures of lactic acid bacteria and Saccharomyces cerevisiae within 200 s. The results indicate that the MCE system can be conveniently used for the rapid and highly sensitive detection of microorganisms. Thus, MCE can provide a cheap and simple method for the on-line detection of microbial contamination.

Recent developments in electrochemical detection for microchip capillary electrophoresis

Significant progress in the development of miniaturized microfluidic systems has occurred since their inception over a decade ago. This is primarily due to the numerous advantages of microchip analysis, including the ability to analyze minute samples, speed of analysis, reduced cost and waste, and portability. This review focuses on recent developments in integrating electrochemical (EC) detection with microchip capillary electrophoresis (CE). These detection modes include amperometry, conductimetry, and potentiometry. EC detection is ideal for use with microchip CE systems because it can be easily miniaturized with no diminution in analytical performance. Advances in microchip format, electrode material and design, decoupling of the detector from the separation field, and integration of sample preparation, separation, and detection on-chip are discussed. Microchip CEEC applications for enzyme/immunoassays, clinical and environmental assays, as well as the detection of neurotransmitters are also described.

Low-density lipoprotein analysis in microchip capillary electrophoresis systems.

Due to the mounting evidence for altered lipoprotein and cholesterol-lipoprotein content in several disease states, there has been an increasing interest in analytical methods for lipoprotein profiling for diagnosis. The separation of low- and high-density lipoproteins (LDL and HDL, respectively) has been recently demonstrated using a microchip capillary electrophoresis (CE) system [1]. In contrast to this previous study, the present report demonstrates that LDL analysis can be performed in an uncoated glass microchannel. Moreover, by adding sodium dodecyl sulfate (SDS) to the sample at a concentration well below the critical micellar concentration prior to injection, the LDL peak undergoes a focusing effect and exhibits an apparent efficiency of 2.2 x 10(7) plates/m. Laser light scattering experiments demonstrate that the low concentration of SDS used does not significantly alter lipoprotein particle size distribution within the time course that the analysis is performed. It is thus hypothesized that SDS nondisruptively coats LDL particles. The peak sharpening effect, observed only when SDS is added solely to the sample, is probably due to a mobility gradient created between the sample and the running buffer. The chip-based method demonstrated here has the potential for rapid analysis and sensitive detection of different LDL forms of clinical relevance.

Integrated circuit microchip system with multiplex capillary electrophoresis module for DNA analysis

In this paper, we describe the use of an integrated circuit (IC) microchip system as a detector in multiplex capillary electrophoresis (CE). This combination of multiplex capillary gel electrophoresis and the IC microchip technology represents a novel approach to DNA analysis on the microchip platform. Separation of DNA ladders using a multiplex CE microsystem of four capillaries was monitored simultaneously using the IC microchip system. The IC microchip–CE system has advantages such as low cost, rapid analysis, compactness, and multiplex capability, and has great potential as an alternative system to conventional capillary array gel electrophoresis systems based on charge-coupled device (CCD) detection.