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Microchip
Terms modified by Microchip Selected AbstractsElectrochemical Detection of Anions on an Electrophoresis Microchip with Integrated Silver ElectrodeELECTROANALYSIS, Issue 13 2005Jilin Yan Abstract A poly(dimethylsiloxane)/glass hybrid microfluidic chip with integrated silver electrode is described for electrochemical detection of anions. The working electrode was directly fabricated on a glass slide and the chip formed by reversibly sealing of a PDMS slab with microchannels to the slide. Under an alkaline phosphate condition, thiocyanide and three halides were sensitively detected. Factors influencing the separation and detection procedure were discussed and optimized. Linear responses over two magnitudes were obtained with limit of detection at the micromolar level. [source] Microchip-based small, dense low-density lipoproteins assay for coronary heart disease risk assessmentELECTROPHORESIS, Issue 9 2008Hua Wang Abstract Small, dense low-density lipoprotein (sdLDL) has been accepted as an emerging cardiovascular risk factor, and there has been an increasing interest in analytical methods for sdLDL profiling for diagnosis. Serum sdLDL may be measured by different laboratory techniques, but all these methods are laborious, time-consuming, and costly. Recently, we have demonstrated that a low-temperature bonding of quartz microfluidic chips for serum lipoproteins analysis (Zhuang, G., Jin, Q., Liu, J., Cong, H. et al., Biomed. Microdevices 2006, 8, 255,261). In contrast to this previous study, we chose SDS as anionic surfactant to modify both lipoproteins and the channel surface to minimize lipoprotein adsorption and improve the resolution of lipoprotein separation. Two major LDL subclass patterns including large, buoyant LDL (lLDL), sdLDL, and high-density lipoprotein (HDL) were effectively separated with high reproducibility. RSD values of the migration time (min) and peak areas of standard LDL and HDL were 6.28, 4.02, 5.02, and 2.5%, respectively. Serum lipoproteins of 15 healthy subjects and 15 patients with coronary heart disease (CHD) were separated by microchip CE. No peaks of sdLDL were detected in serum samples of healthy subjects while sdLDL fractional peaks were observed in patients' entire serum samples. These results suggested that the microchip-based sdLDLs assay was a simple, rapid, and highly efficient technique and significantly improved the analysis of CHD risk factors. [source] Microchip, reverse transcription-polymerase chain reaction and culture methods to detect enterovirus infection in pediatric patientsPEDIATRICS INTERNATIONAL, Issue 1 2006LON-YEN TSAO Abstract Background: Enterovirus infection usually presents with mild and self-limited illness in children. However, Enterovirus type 71 can be characterized by neurotropism and may cause severe illness or even sudden death. Early detection of the virus will allow a physician to provide intensive or aggressive intervention. The purpose of the present study was to compare sensitivity of two innovative laboratory methods, that is, the DR.EV microchip method (DR. Chip Biotechnology, Shin-Tsu, Taiwan) and the reverse transcription-polymerase chain reaction (RT-PCR) method following conventional virus culture in detecting enterovirus infection in pediatric patients with herpangina or hand,foot,mouth disease. Methods: A total of 87 children (age range: 1,8 years) were enrolled because of typical clinical findings of herpangina and hand,foot,mouth disease. Two hundred children selected after a careful clinical history review and physical examinations, were included as controls. All of these children had at least throat swab and rectal swab specimens taken and tested for evidence of enterovirus infection by microchip, RT-PCR and virus culture methods. In addition, 21 patients also had cerebrospinal fluid (CSF) specimens taken to test for possible central nervous system involvement. Result: The test results obtained from the 200 healthy kindergarten children were all negative for enteroviral infection by these three methods. Among the 87 test patients, the positive rates for throat swab, rectal swab and CSF by DR.EV chip, RT-PCR and virus culture were 71%, 68%, and 45% (throat swab); 66%, 61%, and 33% (rectal swab); and 52%, 29%, and 5% (CSF), respectively. There was no significant difference in the positive rates between the DR.EV chip and the RT-PCR methods (P > 0.1) on all types of specimens. However, statistically significant differences in positive rates were noted between the DR.EV chip and the conventional virus culture methods on all types of specimens (P < 0.001). Sensitivity of the microchip, RT-PCR and virus culture methods, was 82%, 72%, and 53%, respectively. Conclusion: The DR.EV chip method yielded a statistically higher positive rate and faster test results than the conventional viral culture method. [source] Kinetic Measurements of Protein Conformation in a MicrochipBIOTECHNOLOGY PROGRESS, Issue 5 2006Matthew B. Kerby This paper presents a microchip-based system for collecting kinetic time-based information on protein refolding and unfolding. Dynamic protein conformational change pathways were studied in microchannel flow using a microfluidic device. We present a protein-conserving approach for quantifying refolding by dynamically varying the concentration of the chemical denaturants, guanidine hydrochloride and urea. Short diffusion distances in the microchannel result in rapid equilibrium between protein and titrating solutions. Dilutions on the chip were tightly regulated using pressure controls rather than syringe-based flow, as verified with extensive on-chip tracer dye controls. To validate this protein assay method, folding transition experiments were performed using two well-characterized proteins, human serum albumin (HSA) and bovine carbonic anhydrase (BCA). Transition events were monitored through fluorescence intensity shifts of the protein dye 8-anilino-1-naphthalenesulfonic acid (ANS) during dilutions of protein from urea or guanidine hydrochloride solutions. The enzymatic activity of refolded BCA was measured by UV absorption through the conversion of p -nitrophenyl acetate (p-NPA). The microchip protein refolding transitions using ANS were well-correlated with conventional plate-based experiments. The microfluidic platform enables refolding studies to identify rapidly the optimal folding strategy for a protein using small quantities of material. [source] Separation and Detection of Narcotic Drugs on a Microchip Using Micellar Electrokinetic Chromatography and ElectrochemiluminescenceELECTROANALYSIS, Issue 6 2008Yan Du Abstract A new approach for fast and sensitive electrochemiluminescence (ECL) detection of narcotic drugs on a microchip after separation by micellar electrokinetic chromatography (MEKC) is presented, taking the cocaine and its hydrolysate ecgonine as the test analytes. The mixture of hydrophilic BMIMBF4 ionic liquid (IL) and sodium dodecyl sulfate (SDS) was used directly as the buffer of MEKC with less noisy baselines, lower electrophoretic current and satisfactory separation performance. This developed microchip MEKC,ECL system was successfully applied to the determination of two very similar narcotics, heroin and codeine, within 100s in urine sample and was demonstrated as a promising method in clinical and forensic analysis. [source] Electrochemical Sensing of ExplosivesELECTROANALYSIS, Issue 4 2007Joseph Wang Abstract This article reviews recent advances in electrochemical sensing and detection of explosive substances. Escalating threats of terrorist activities and growing environmental concerns have generated major demands for innovative field-deployable tools for detecting explosives in a fast, sensitive, reliable and simple manner. Field detection of explosive substances requires that a powerful analytical performance be coupled to miniaturized low-cost instrumentation. Electrochemical devices offer attractive opportunities for addressing the growing explosive sensing needs. The advantages of electrochemical systems include high sensitivity and selectivity, speed, a wide linear range, compatibility with modern microfabrication techniques, minimal space and power requirements, and low-cost instrumentation. The inherent electroactivity of nitroaromatic, nitramine and nitroester compounds makes them ideal candidates for electrochemical detection. Recent activity in various laboratories has led to the development of disposable sensor strips, novel electrode materials, submersible remote sensors, and electrochemical detectors for microchip (,Lab-on-Chip') devices for on-site electrochemical detection of explosive substances. The attractive behavior of these electrochemical monitoring systems makes them very promising for addressing major security and environmental problems. [source] Total analysis of endocrine disruptors in a microchip with gold nanoparticlesELECTROPHORESIS, Issue 18 2010Hui-Bog Noh Abstract The development of a simple, sensitive, and direct method for the total analysis of certain endocrine disruptors was performed by integrating preconcentration steps to a separation step on a microchip through the modification of the field-amplified sample stacking and field-amplified sample injection steps. To improve the preconcentration and separation performances, the preconcentration and separation buffers were modified with citrate-stabilized gold nanoparticles (AuNPs). For the detection of the separated samples, cellulose-dsDNA/AuNPs-modified carbon paste electrodes were used at the channel end. The experimental parameters affecting the analytical performances, such as the buffer concentration, water plug length, SDS concentration in the separation buffer, AuNPs concentration, preconcentration time, detection potential and electrode to channel distance, were examined. The detection limits of the test compounds were between 7.1 and 11.1,fM and that for 4-pentylphenol was 7.1 (±1.1) fM. Dynamic ranges were in the range from 0.15 to 600.0,pM. The experiments with real samples were performed to evaluate the reliability of the proposed method. [source] Microfluidic devices for electrokinetic sample fractionationELECTROPHORESIS, Issue 15 2010Zhen Wang Abstract We present three generations of microchip-based "in-space" sample fractionators and collectors for use in proteomics. The basic chip design consisted of a single channel for CE separation of analytes that then intersects a fractionation zone feed into multiple high aspect ratio microchannels for fractionation of separated components. Achievements of each generation are discussed in relation to important design criteria. CE-separated samples were electrokinetically driven to multiple collection channels in sequence without cross-contamination under the protection of sheath streams. A 36-channel fractionator demonstrated the efficacy of a high-throughput fractionator with no observed cross-contamination. A mixture of IgG and BSA was used to test the efficiency of the fractionator and collector. CE of the fractionated samples was performed on the same device to verify their purity. Our demonstration proved to be efficient and reproducible in obtaining non-contaminated samples over 15 sample injections. Experimental results were found to be in close agreement with PSpice simulation in terms of flow behavior, contamination control and device performance. The design presented here has a great potential to be integrated in proteomic platforms. [source] Filmy channel microchip with amperometric detectionELECTROPHORESIS, Issue 22 2009Wei Wang Abstract In this article, a new type of microchip with filmy channels and a sample-injection fracture is introduced. Unlike commercial microchip, new microchip possessed filmy channel with width 2,3,mm. The effective cooling ability made filmy channel microchip restrain the generation of Joule heat even under electric field of 588,V/cm. Moreover, wider channel could be more easily modified to prevent the absorption of samples, load more samples and result in a higher sensitivity. Sample-injection fracture was first applied to match the filmy channel in microchip. Equipped with an amperometric detector, the characteristics of the newly designed filmy channel microchip had been studied and the results showed that it had good reproducibility, higher sensitivity and excellent separation ability. The microchip was also applied to separate L -tryptophan's metabolites, namely 5-hydroxy- L -tryptophan, 5-hydroxytryptamine and 5-hydroxy-indole-3-acetic acid. [source] Multiple-point electrochemical detection for a dual-channel hybrid PDMS-glass microchip electrophoresis deviceELECTROPHORESIS, Issue 19 2009Mario Castaño-Álvarez Abstract A new PDMS-based dual-channel MCE with multiple-point amperometric detection has been evaluated. Electrophoresis has been optimised in a single-channel device. Pretreatment with 0.1,M NaOH is very important for increasing and stabilising the EOF. The precision is adequate for a day's work in terms of both peak current and migration time. The RSD of the peak current for five successive signals was 1.9, 2.4 and 3.1% for dopamine, p- aminophenol and hydroquinone. RSD for the migration time was always less than 1.3%, which demonstrates the stability of the EOF and the possibility of running multiple experiments in the same microchip. The adequate inter-microchip precision as well as the rapid and simple manufacturing procedure indicates the disposable nature of the PDMS microchips. A dual-channel device with very simple multiple-point amperometric detection is proposed here. Elasticity of the PDMS allows removing the polymer slightly and aligning gold wires working electrodes. Injection can be performed from each of the sample reservoirs or from both simultaneously. The distance between the separation channels is critical for obtaining adequate signals as well as the introduction of a high-voltage electrode in the buffer reservoir. Simultaneous measurement of the same analytes in both channels is possible by applying the same potential. Moreover, since no cross-separation is produced, different analytes or samples can be simultaneously measured. [source] Highly efficient capture and enumeration of low abundance prostate cancer cells using prostate-specific membrane antigen aptamers immobilized to a polymeric microfluidic deviceELECTROPHORESIS, Issue 18 2009Udara Dharmasiri Abstract Prostate tumor cells over-express a prostate-specific membrane antigen (PSMA) that can be used as a marker to select these cells from highly heterogeneous clinical samples, even when found in low abundance. Antibodies and aptamers have been developed that specifically bind to PSMA. In this study, anti-PSMA aptamers were immobilized onto the surface of a capture bed poised within a PMMA, microchip, which was fabricated into a high-throughput micro-sampling unit (HTMSU) used for the selective isolation of rare circulating prostate tumor cells resident in a peripheral blood matrix. The HTMSU capture bed consisted of 51 ultra-high-aspect ratio parallel curvilinear channels with a width similar to the prostate cancer cell dimensions. The surface density of the PSMA-specific aptamers on an ultraviolet-modified PMMA microfluidic capture bed surface was determined to be 8.4×1012,molecules/cm2. Using a linear velocity for optimal cell capture in the aptamer-tethered HTMSU (2.5,mm/s), a recovery of 90% of LNCaP cells (prostate cancer cell line; used as a model in this example) was found. Due to the low abundance of these cells, the input volume required was 1,mL and this could be processed in ,29,min using an optimized linear flow rate of 2.5,mm/s. Captured cells were subsequently released intact from the affinity surface using 0.25%,w/w trypsin followed by counting individual cells using a contact conductivity sensor integrated into the HTMSU that provided high detection and sampling efficiency (,100%) and did not require staining of the cells for enumeration. [source] Chip-CE/MS using a flat low-sheath-flow interfaceELECTROPHORESIS, Issue 24 2008Fu-An Li Abstract A chip-CE/ESI/MS interface based on a low-sheath-flow design has been developed. A flat low-sheath-flow interface was fabricated to facilitate the coupling with a CE microchip. The interface consists of a PMMA reservoir block, a PMMA platform and a replaceable ESI sprayer. A CE interface was constructed by using a wire-assisted epoxy-fixing method to connect a 1.5,cm connecting capillary to the end of chip-CE channel. The opposite end of the connecting capillary was tapered to approximately 40,,m od to fit tightly inside the back end of a removable fused-silica capillary ESI sprayer, which was also tapered to give a 10,,m orifice. With this 1.5,cm connecting capillary, the sheath liquid flowed coaxially around the connecting capillary to create a low dead volume liquid junction at the interface between the connecting capillary and the ESI emitter. An advantage of the current design over existing chip-based CE/MS interfaces is that ESI emitter can easily be replaced. The analytical utility of this microdevice was demonstrated by the analysis of two synthetic mixtures: a series histamine antagonists and a mixture of synthetic peptides. [source] Cover Picture: Electrophoresis 23'2008ELECTROPHORESIS, Issue 23 2008Article first published online: 3 DEC 200 Issue 23 is a paper symposium on "DNA sequencing and genotyping". It consists of 22 contributions covering a wide spectrum of investigations in the area of DNA sequencing by capillary electrophoresis and the latest technologies for DNA sequencing and genotyping on microfluidic devices. Ten contributions deal with microchip-based electrophoresis analyses of DNA, an indication that miniaturized devices may surge to the fore for medical sequencing applications on individual DNA samples, as well as for forensic applications. [source] A parylene-based dual channel micro-electrophoresis system for rapid mutation detection via heteroduplex analysis,ELECTROPHORESIS, Issue 18 2008Sertan Sukas Abstract A new dual channel micro-electrophoresis system for rapid mutation detection based on heteroduplex analysis was designed and implemented. Mutation detection was successfully achieved in a total separation length of 250,,m in less than 3,min for a 590,bp DNA sample harboring a 3,bp mutation causing an amino acid change. Parylene-C was used as the structural material for fabricating the micro-channels as it provides conformal deposition, transparency, biocompatibility, and low background fluorescence without any surface treatment. A new dual channel architecture was derived from the traditional cross-channel layout by forming two identical channels with independent sample loading and waste reservoirs. The control of injected sample volume was accomplished by a new u-turn injection technique with pull-back method. The use of heteroduplex analysis as a mutation detection method on a cross-linked polyacrylamide medium provided accurate mutation detection in an extremely short length and time. The presence of two channels on the microchip offers the opportunity of comparing the sample to be tested with a desired control sample rapidly, which is very critical for the accuracy and reliability of the mutation analyses, especially for clinical and research purposes. [source] Underivatized cyclic olefin copolymer as substrate material and stationary phase for capillary and microchip electrochromatographyELECTROPHORESIS, Issue 15 2008Omar Gustafsson Abstract We report, for the first time, the use of underivatized cyclic olefin copolymer (COC, more specifically: Topas) as the substrate material and the stationary phase for capillary and microchip electrochromatography (CEC), and demonstrate chromatographic separations without the need of coating procedures. Electroosmotic mobility measurements in a 25,,m id Topas capillary showed a significant cathodic EOF that is pH-dependent. The magnitude of the electroosmotic mobility is comparable to that found in glass substrates and other polymeric materials. Open-tubular CEC was employed to baseline-separate three neutral compounds in an underivatized Topas capillary with plate heights ranging from 5.3 to 12.7,,m. The analytes were detected using UV absorbance at 254,nm, thus taking advantage of the optical transparency of Topas at short wavelengths. The fabrication of a Topas-based electrochromatography microchip by nanoimprint lithography is also presented. The microchip has an array of pillars in the separation column to increase the surface area. The smallest features that were successfully imprinted were around 2,,m wide and 5,,m high. No plasma treatment was used during the bonding, thus keeping the surface properties of the native material. An RP microchip electrochromatography separation of three fluorescently labeled amines is demonstrated on the underivatized microchip with plate heights ranging from 3.4 to 22,,m. [source] Cover Picture: Electrophoresis 14/2008ELECTROPHORESIS, Issue 14 2008Article first published online: 23 JUL 200 Issue 14 is a regular issue including an Emphasis Section offering a series of 9 papers on ,Microfluidics and Miniaturization". These 9 research papers report on various topics including studying single DNA molecules, selective release of intracellular molecules on the single cell level, isoelectric focusing of proteins in an ordered micropillar array, sample stream focusing in a microchip, integrated microfluidic system for sensing infectious viral disease, EOF in annulus and rectangular channels, confinement effects on monolith morphology, accumulation and filtering of nanoparticles in microchannels, and carbon nanotubes disposable detectors. [source] Carbon nanotube disposable detectors in microchip capillary electrophoresis for water-soluble vitamin determination: Analytical possibilities in pharmaceutical quality controlELECTROPHORESIS, Issue 14 2008Agustín G. Crevillén Abstract In this work, the synergy of one mature example from "lab-on-chip" domain, such as CE microchips with emerging miniaturized carbon nanotube detectors in analytical science, is presented. Two different carbon electrodes (glassy carbon electrode (GCE) 3,mm diameter, and screen-printed electrode (SPE) 0.3,mm×2.5,mm) were modified with multiwalled carbon nanotubes (MWCNTs) and their electrochemical behavior was evaluated as detectors in CE microchip using water-soluble vitamins (pyridoxine, ascorbic acid, and folic acid) in pharmaceutical preparations as representative examples. The SPE modified with MWCNT was the best electrode for the vitamin analysis in terms of analytical performance. In addition, accurate determination of the three vitamins in four different pharmaceuticals was obtained (systematic error less than 9%) in only 400,s using a protocol that combined the sample analysis and the methodological calibration. [source] On-line cell lysis and DNA extraction on a microfluidic biochip fabricated by microelectromechanical system technologyELECTROPHORESIS, Issue 9 2008Xing Chen Dr. Abstract Integrating cell lysis and DNA purification process into a micrototal analytical system (,TAS) is one critical step for the analysis of nucleic acids. On-chip cell lysis based on a chemical method is realized by sufficient blend of blood sample and the lyzing reagent. In this paper two mixing models, T-type mixing model and sandwich-type mixing model, are proposed and simulation of those models is conducted. Result of simulation shows that the sandwich-type mixing model with coiled channel performs best and this model is further used to construct the microfluidic biochip for on-line cell lysis and DNA extraction. The result of simulation is further verified by experiments. It asserts that more than 80% mixing of blood sample and lyzing reagent which guarantees that completed cell lysis can be achieved near the inlet location when the cell/buffer velocity ratio is less than 1:5. After cell lysis, DNA extraction by means of a solid-phase method is implemented by using porous silicon matrix which is integrated in the biochip. During continuous flow process in the microchip, rapid cell lysis and PCR-amplifiable genomic DNA purification can be achieved within 20,min. The potential of this microfluidic biochip is illustrated by pretreating a whole blood sample, which shows the possibility of integration of sample preparation, PCR, and separation on a single device to work as portable point-of-care medical diagnostic system. [source] Microchip-based small, dense low-density lipoproteins assay for coronary heart disease risk assessmentELECTROPHORESIS, Issue 9 2008Hua Wang Abstract Small, dense low-density lipoprotein (sdLDL) has been accepted as an emerging cardiovascular risk factor, and there has been an increasing interest in analytical methods for sdLDL profiling for diagnosis. Serum sdLDL may be measured by different laboratory techniques, but all these methods are laborious, time-consuming, and costly. Recently, we have demonstrated that a low-temperature bonding of quartz microfluidic chips for serum lipoproteins analysis (Zhuang, G., Jin, Q., Liu, J., Cong, H. et al., Biomed. Microdevices 2006, 8, 255,261). In contrast to this previous study, we chose SDS as anionic surfactant to modify both lipoproteins and the channel surface to minimize lipoprotein adsorption and improve the resolution of lipoprotein separation. Two major LDL subclass patterns including large, buoyant LDL (lLDL), sdLDL, and high-density lipoprotein (HDL) were effectively separated with high reproducibility. RSD values of the migration time (min) and peak areas of standard LDL and HDL were 6.28, 4.02, 5.02, and 2.5%, respectively. Serum lipoproteins of 15 healthy subjects and 15 patients with coronary heart disease (CHD) were separated by microchip CE. No peaks of sdLDL were detected in serum samples of healthy subjects while sdLDL fractional peaks were observed in patients' entire serum samples. These results suggested that the microchip-based sdLDLs assay was a simple, rapid, and highly efficient technique and significantly improved the analysis of CHD risk factors. [source] Microchip micellar electrokinetic chromatography separation of alkaloids with UV-absorbance spectral detectionELECTROPHORESIS, Issue 4 2008Carl I. D. Newman Abstract A microchip device is demonstrated for the electrophoretic separation and UV-absorbance spectral detection of four toxic alkaloids: colchicine, aconitine, strychnine, and nicotine. A fused-silica (quartz) microchip containing a simple cross geometry is utilized to perform the separations, and a miniature, fiber-optic CCD spectrometer is coupled to the microchip for detection. Sensitive UV-absorbance detection is achieved via the application of online preconcentration techniques in combination with the quartz microchip substrate which contains an etched bubble-cell for increased pathlength. The miniature CCD spectrometer is configured to detect light between 190 and 645,nm and LabView programming written in-house enables absorbance spectra as well as separations to be monitored from 210 to 400,nm. Consequently, the configuration of this microchip device facilitates qualitative and quantitative separations via simultaneous spatial and spectral resolution of solutes. UV-absorbance limits of quantification for colchicine, 20,,M (8,mg/L); strychnine, 50,,M (17,mg/L); aconitine, 50,,M (32,mg/L); and nicotine, 100,,M (16,mg/L) are demonstrated on the microchip. With the exception of aconitine, these concentrations are ,20-times more sensitive than lethal dose monitoring requirements. Finally, this device is demonstrated to successfully detect each toxin in water, skim milk, and apple juice samples spiked at sublethal dose concentrations after a simple, SPE procedure. [source] Real-time monitoring of intracellular calcium dynamic mobilization of a single cardiomyocyte in a microfluidic chip pertaining to drug discoveryELECTROPHORESIS, Issue 24 2007Xiujun Li Abstract A microfluidic method for real-time quantitative measurement of cellular response pertaining to drug discovery is reported. This method is capable of multiple-step liquid delivery for measuring the drug response of a single cardiomyocyte, due to the improved cell retention by a newly designed chip. The chip, which consists of a cell-retention chamber with a weir structure, was fabricated just by a one-photomask microfabrication procedure followed by on-chip etching. This method differs from the conventional method, which uses two-mask photolithography to fabricate the microchannel (deep etch) and the weir structure (shallow etch). The dimensions of the weir structure have been predicted by a mathematical model, and confirmed by confocal microscopy. Using this microfluidic method, the dynamic [Ca2+]i mobilization in a single cardiomyocyte during its spontaneous contraction was quantified. Furthermore, we measured the cellular response of a cardiomyocyte on (i) a known cardiotonic agent (caffeine), (ii) a cardiotoxic chemotherapeutic drug (daunorubicin), and (iii) an herbal anticancer drug candidate , isoliquiritigenin (IQ) based on the fluorescent calcium measurement. It was found that IQ had produced a less pronounced effect on calcium mobilization of the cardiomyocytes whereas caffeine and daunorubicin had much stronger effects on the cells. These three experiments on cardiomyocytes pertaining to drug discovery were only possible after the improved cell retention provided by the new chip design (MV2) required for multiple-step real-time cellular analysis on a microchip, as compared with our old chip design (MV1). [source] Determination of 1-methylhistidine and 3-methylhistidine by capillary and chip electrophoresis with contactless conductivity detectionELECTROPHORESIS, Issue 13 2007Petr T, ma Dr. Abstract CE with capacitively coupled contactless detection (C4D) was used to determine 3-methylhistidine (3-MH) and 1-methylhistidine (1-MH). The C4D response to 3-MH was studied in a BGE consisting of 500,mM acetic acid and ammonia at varying concentration and the results were compared with the theory. Complete separation of a model mixture of 3-MH, 1-MH, and histidine (His) was attained in two optimized BGEs, one containing 500,mM HAc, 20,mM NH4OH, and 0.1 % m/v hydroxyethylcellulose (HEC), pH,3.4 (I) and the other consisting of 100,mM morpholinoethanesulfonic acid (MES), 25,mM LiOH, and 0.1 % m/v HEC, pH,5.5 (II). These optimized BGEs were tested in CE/C4D analyses of urine. Promising results were obtained for separation and determination of 3-MH, 1-MH, and His on a silicon microchip, using aluminum strips as the C4D electrodes; the three analytes were baseline-separated within less than 30,s with a separation channel effective length of 38,mm. The LOD were satisfactory and amounted to 26.4,,M for 3-MH and 18.3,,M for 1-MH. [source] Toward an integrated microchip sized 2-D polyacrylamide slab gel electrophoresis device for proteomic analysisELECTROPHORESIS, Issue 3 2007Zuzana Demianová Abstract We describe a miniaturized instrument capable of performing 2-DE. Our miniaturized device is able to perform IEF and polyacrylamide slab gel electrophoresis (PASGE) in the same unit. It consists of a compartment for a first-dimensional IEF gel, which is connected to a second-dimensional PASGE gel. The focused samples are automatically transferred from the IEF gel to the PASGE gel by electromigration. Our preliminary experiments show that the device is able to focus and separate a mixture of proteins in approximately 1,h, excluding the time required for the staining procedure. On average, the gel-to-gel retardation factor,(Rf) variation was 6.2% (±0.9%) and pI variation was 2.5% (±0.6%). Separated protein spots were excised from stained gels, digested with trypsin, and further identified by MS, thus enabling direct proteomic analysis of the separated proteins. [source] Dielectrophoresis microsystem with integrated flow cytometers for on-line monitoring of sorting efficiencyELECTROPHORESIS, Issue 24 2006Zhenyu Wang Abstract Dielectrophoresis (DEP) and flow cytometry are powerful technologies and widely applied in microfluidic systems for handling and measuring cells and particles. Here, we present a novel microchip with a DEP selective filter integrated with two microchip flow cytometers (FCs) for on-line monitoring of cell sorting processes. On the microchip, the DEP filter is integrated in a microfluidic channel network to sort yeast cells by positive DEP. The two FCs detection windows are set upstream and downstream of the DEP filter. When a cell passes through the detection windows, the light scattered by the cell is measured by integrated polymer optical elements (waveguide, lens, and fiber coupler). By comparing the cell counting rates measured by the two FCs, the collection efficiency of the DEP filter can be determined. The chips were used for quantitative determination of the effect of flow rate, applied voltage, conductivity of the sample, and frequency of the electric field on the sorting efficiency. A theoretical model for the capture efficiency was developed and a reasonable agreement with the experimental results observed. Viable and non-viable yeast cells showed different frequency dependencies and were sorted with high efficiency. At 2,MHz, more than 90% of the viable and less than 10% of the non-viable cells were captured on the DEP filter. The presented approach provides quantitative real-time data for sorting a large number of cells and will allow optimization of the conditions for, e.g., collecting cancer cells on a DEP filter while normal cells pass through the system. Furthermore, the microstructure is simple to fabricate and can easily be integrated with other microstructures for lab-on-a-chip applications. [source] A new method for fabrication of an integrated indium tin oxide electrode on electrophoresis microchips with amperometric detection and its application for determination of synephrine and hesperidin in pericarpium citri reticulataeELECTROPHORESIS, Issue 21 2006Wei Wang Abstract A new, simple, and fast method to integrate indium tin oxide electrode in an amperometric detection (AD) microchip is introduced. Without the help of photoresist and complicated apparatus, the microchip could be fabricated in most laboratories in a very short time by this method. The experiment indicated that the microchip was stable and had good reproducibility. On this microchip, a new method was established to separate and determine synephrine and hesperidin, which are the main electroactively bioactive ingredients of pericarpium citri reticulatae, by AD. Under the optimal conditions, the two compounds could be completely separated within 5.5,min and the detection limits were 0.13 and 0.57,,g/mL, respectively. The proposed method has been successfully used to determine synephrine and hesperidin in real pericarpium citri reticulatae sample, and the results show that the proposed method is sensitive, reliable, fast, and economical. [source] Monolithic media in microfluidic devices for proteomicsELECTROPHORESIS, Issue 18 2006Kyung Won Ro Abstract Considerable effort has been invested in the development of integrated microfluidic devices for fast and highly efficient proteomic studies. Among various fabrication techniques for the preparation of analytical components (separation columns, reactors, extractors, valves, etc.) in integrated microchips, in situ fabrication of monolithic media is receiving increasing attention. This is mainly due to the ease and simplicity of preparation of monolithic media and the availability of various precursors and chemistries. In addition, UV-initiated photopolymerization technique enables the incorporation of multiple analytical components into specified parts of a single microchip using photomasks. This review summarizes preparation methods for monolithic media and their application as microfluidic analytical components in microchips. [source] Modified Hadamard transform microchip electrophoresisELECTROPHORESIS, Issue 16 2005Renato Guchardi Abstract Sensitivity is a crucial point in the development applications for medicine or environmental samples in which the analytes are present in the nanomolar range. Besides further technical development of detection systems, the multiplex sample injection technique can be applied for enhancing the signal-to-noise ratio. Hadamard transform is easily applied to microchip electrophoresis due to the fact that sample injection is generally achieved through cross, double-tee, or tee injector structures. This paper reports the first demonstration of a modified Hadamard transform electrophoresis on a microchip by using an amperometric detector. Contrary to the previous Hadamard applications, the resolution (number of points per unit of time) of electropherograms obtained is independent of the number of injections. [source] Poly(methylmethacrylate) and Topas capillary electrophoresis microchip performance with electrochemical detectionELECTROPHORESIS, Issue 16 2005Mario Castaño-Álvarez Abstract A capillary electrophoresis (CE) microchip made of a new and promising polymeric material: Topas (thermoplastic olefin polymer of amorphous structure), a cyclic olefin copolymer with high chemical resistance, has been tested for the first time with analytical purposes, employing an electrochemical detection. A simple end-channel platinum amperometric detector has been designed, checked, and optimized in a poly-(methylmethacrylate) (PMMA) CE microchip. The end-channel design is based on a platinum wire manually aligned at the exit of the separation channel. This is a simple and durable detection in which the working electrode is not pretreated. H2O2 was employed as model analyte to study the performance of the PMMA microchip and the detector. Factors influencing migration and detection processes were examined and optimized. Separation of H2O2 and L -ascorbic acid (AsA) was developed in order to evaluate the efficiency of microchips using different buffer systems. This detection has been checked for the first time with a microchip made of Topas, obtaining a good linear relationship for mixtures of H2O2 and AsA in different buffers. [source] Microautosamplers for discrete sample injection and dispensationELECTROPHORESIS, Issue 9 2005Chun-Wei Huang Abstract Microfluidic systems show considerable potential for use in the continuous reaction and analysis of biosamples for various applications, such as drug screening and chemical synthesis. Typically, microfluidic chips are externally connected with large-scale autosamplers to inject specific volumes of discrete samples in the continuous monitoring and analysis of multiple samples. This paper presents a novel microelectromechanical system (MEMS)-based autosampler capable of performing the discrete injection and dispensation of variable-volume samples. This microdevice can be integrated with other microfluidic devices to facilitate the continuous monitoring and analysis of multiple biosamples. By means of electroosmotic focusing and switching controlled by the direct application of electric sources on specific fluid reservoirs, a precise sample volume can be injected into the specified outlet port. Fluorescence dye images verify the performance of the developed device. An injection-and-washing scheme is developed to prevent cross-contamination during the continuous injection of different samples. This approach renders feasible the injection of several discrete samples using a single microchip. Compared to its large-scale counterparts, the developed microautosampler is compact in size, has low fabrication costs, is straightforward to control, and most importantly, is readily integrated with other microfluidic devices (e.g., microcapillary electrophoresis chips) to form a microfluidic system capable of the continuous monitoring and analysis of bioreactions. The proposed microautosampler could be promising towards realizing the micrototal analysis system (,-TAS) concept. [source] Simultaneous electrochemical and electrochemiluminescence detection for microchip and conventional capillary electrophoresisELECTROPHORESIS, Issue 3 2005Haibo Qiu Abstract A simultaneous electrochemical (EC) and electrochemiluminescence (ECL) detection scheme was introduced to both microchip and conventional capillary electrophoresis (CE). In this dual detection scheme, tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)32+) was used as an ECL reagent as well as a catalyst (in the formation of Ru(bpy)33+) for the EC detection. In the Ru(bpy)32+ -ECL process, Ru(bpy)33+ was generated and then reacted with analytes resulting in an ECL emission and a great current enhancement in EC detection due to the catalysis of Ru(bpy)33+. The current response and ECL signals were monitored simultaneously. In the experiments, dopamine and three kinds of pharmaceuticals, anisodamine, ofloxacin, and lidocaine, were selected to validate this dual detection strategy. Typically, for the EC detection of dopamine with the presence of Ru(bpy)32+, a ,5 times higher signal-to-noise ratio (S/N) can be achieved than that without Ru(bpy)32+, during the simultaneous EC and ECL detection of a mixture of dopamine and lidocaine using CE separation. The results indicated that this dual EC and ECL detection strategy could provide a simple and convenient detection method for analysis of more kinds of analytes in CE separation than the single EC or ECL detection alone, and more information of analytes could be achieved in analytical applications simultaneously. [source] | |||||||||||||||||||