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At least 181 records · Page 10Linked to original sources
PubMed2005

Precise nanoliter fluid handling system with integrated high-speed flow sensor.

A system for accurate low-volume delivery of liquids in the micro- to nanoliter range makes use of an integrated miniature flow sensor as part of an intelligent feedback control loop driving a micro-solenoid valve. The flow sensor is hydraulically connected with the pressurized system liquid in the dispensing channel and located downstream from the pressure source, above the solenoid valve. The sensor operates in a differential mode and responds in real-time to the internal flow-pulse resulting from the brief opening interval of the solenoid valve leading to a rapid ejection of a fluid droplet. The integral of the flow-pulse delivered by the sensor is directly proportional to the volume of the ejected droplet from the nozzle. The quantitative information is utilized to provide active control of the effectively dispensed or aspirated volume by adjusting the solenoid valve accordingly. This process significantly enhances the precision of the fluid delivery. The system furthermore compensates automatically for any changes in the viscosity of the dispensed liquid. The data delivered by the flow sensor can be saved and backtracked in order to confirm and validate the aspiration and dispensing process in its entirety. The collected dispense information can be used for quality control assessments and automatically be made part of an electronic record.

Biological Assay↗
PubMed2005

Nanoliter dispensing for uHTS using pin tools.

Miniaturization of assays is an important objective in Ultra-HTS. One of the major obstacles has been to find fluid handling systems capable of reliably and accurately delivering between 2 and 200 nl of test compound to assay plates. New methods of forming pins, placing slots in the pins, and hydrophobic coatings bonded onto the pins solve many of the problems encountered by early pin tools. Unlike other low-volume liquid handlers, these new pin tools provide the ability to transfer approximately 2 nl-5 microl of compounds. These pin tools can also use low-volume source plates (2-10 microl) and achieve an accuracy of better than 5%. This, coupled with the ability to transfer small volumes directly from the compound library to assay plates without an intervening dilution plate, saves reagents, throughput time, and consumables and is, therefore, very cost effective. Pin tool compound transfers in the 2-100 nl range provide a simple method to dilute away from the toxic effect that dimethyl sulfoxide has on some assay target cells. The factors that affect liquid transfers by pin tools are discussed in detail as well as the advantages and limitations of pin tools.

Biological Assay↗
PubMed2005

Development of an oligochip for genotyping human leukocyte antigen-B51 and its clinical application.

Human leukocyte antigen (HLA) has been associated with Behcet's disease (BD), among which HLA-B51 is the most strongly associated genetic marker. The sandwich hybridization technique was applied in the design of the specific oligonucleotide probes to ensure the specific and accurate results. The probe-spotted chip was hybridized with the polymerase chain reaction (PCR) amplicons including nine suballeles (B*5101-B*5109) of exons 2 and 3 of HLA-B51 gene to determine the HLA-B51 genotypes. The results were subsequently confirmed by (PCR-SSP) and sequencing and were identical to those from polymerase chain reaction-sequencing specific primers (PCR-SSP) in 27 patients with BD and 30 healthy controls. This suggests that we successfully developed the oligochip for Behcet's-associated gene HLA-B51, which can effectively and accurately identify the HLA-B51 genotypes.

Alleles↗
PubMed2004

Metabolite fingerprinting: detecting biological features by independent component analysis.

MOTIVATION: Metabolite fingerprinting is a technology for providing information from spectra of total compositions of metabolites. Here, spectra acquisitions by microchip-based nanoflow-direct-infusion QTOF mass spectrometry, a simple and high throughput technique, is tested for its informative power. As a simple test case we are using Arabidopsis thaliana crosses. The question is how metabolite fingerprinting reflects the biological background. In many applications the classical principal component analysis (PCA) is used for detecting relevant information. Here a modern alternative is introduced-the independent component analysis (ICA). Due to its independence condition, ICA is more suitable for our questions than PCA. However, ICA has not been developed for a small number of high-dimensional samples, therefore a strategy is needed to overcome this limitation. RESULTS: To apply ICA successfully it is essential first to reduce the high dimension of the dataset, by using PCA. The number of principal components determines the quality of ICA significantly, therefore we propose a criterion for estimating the optimal dimension automatically. The kurtosis measure is used to order the extracted components to our interest. Applied to our A. thaliana data, ICA detects three relevant factors, two biological and one technical, and clearly outperforms the PCA.

Algorithms↗
PubMedDate not supplied

ELISA on a microchip with a photodiode for detection of amphetamine in plasma and urine.

A rapid and sensitive assay was developed for the detection of amphetamine in plasma and urine. The method relies on the principle of competitive ELISA (enzyme-linked immunosorbent assay). A flow microchip with a total volume of 7 microL was used for the development of a chemiluminescent ELISA technique. Solutions, samples, and the chemiluminescence substrate were injected by a flow system, and a photodiode detector was used to measure the light intensity. The incubation time of the competitor (competition phase) was reduced to 10 min. Calibration curves corresponding to analyte concentrations ranging from 40 to 1,000 microg/L in urine samples and from 6 to 96 microg/L in plasma samples were obtained. The detection limits were in the region of 20 and 6 microg/L in urine and plasma, respectively. The main focus of the work was on speed, reliability, reproducibility, and operational stability of the assay. This method was proven readily adaptable to automation and provided reproducible results.

Amphetamine↗
PubMed2005

Arginase activity differs with allergen in the effector phase of ovalbumin- versus trimellitic anhydride-induced asthma.

Both trimellitic anhydride (TMA), a small molecular weight chemical, and ovalbumin (OVA), a reference protein allergen, cause asthma with eosinophilia. To test the hypothesis that different allergens elicit symptoms of asthma via different effector pathways, gene expression was compared in lungs of Balb/c mice sensitized with either TMA or OVA, followed by intratracheal challenge with TMA conjugated to mouse serum albumin (TMA-MSA) or OVA, respectively. Sensitized animals challenged with mouse serum albumin (MSA) alone were controls. Seventy-two hours after challenge, lung eosinophil peroxidase indicated that both allergens caused the same significant change in eosinophilia. Total RNA was isolated from lung lobes of 6-8 animals in each of four treatment groups and hybridized to Affymetrix U74Av2 GeneChips. False discovery rates (q-values) were calculated from an overall F test to identify candidate genes with differences in expression for the four groups. Using a q-value cutoff of 0.1, 853 probe sets had significantly different expression across the four treatment groups. Of these 853 probe sets, 376 genes had an Experimental/Control ratio of greater than 1.2 or less than 1/1.2 for either OVA- or TMA-treated animals, and 249 of the 376 genes were uniquely up- or down-regulated for OVA or TMA (i.e., differentially expressed with the allergen). qRT-PCR analysis of selected transcripts confirmed the gene expression analysis. Increases in both arginase transcript and enzyme activity were significantly greater in OVA-induced asthma compared to TMA-induced asthma. These data suggest that pathways of arginine metabolism and the importance of nitric oxide may differ in OVA- and TMA-induced asthma.

Allergens↗
PubMed2005

Direct measurement of acid efflux from isolated guinea pig pancreatic ducts.

OBJECTIVES: The current studies used the technique of microphysiometry to directly determine the effects of stimulators and inhibitors of pancreatic duct secretion on acid efflux from isolated pancreatic ducts. METHODS: Main and interlobular ducts were isolated from guinea pig pancreata by collagenase digestion and manual selection. Segments were placed in the chambers of a microphysiometer, which uses a silicon chip-based, light-addressable potentiometric sensor to determine the proton concentration in the superfusing solution. Isolated ducts were superfused with a low buffer capacity Ringer's solution at 37 degrees C and the extracellular acidification rate (EAR) was determined by computer-directed protocols. RESULTS: A survey of potential agonists demonstrated that both secretin and the cholinomimetic, carbachol, dramatically increased EAR, with EC50 of 3 nmol/L and 0.6 mumol/L, respectively. The changes in EAR induced by both secretagogues were rapid, peaking within 4-6 minutes, and then declining to a level below the peak but above basal EAR. The enhanced EAR was maintained for at least 30 minutes in the presence of either secretagogue. More modest increases in EAR were evoked by bombesin, substance P, and vasoactive intestinal peptide (VIP). Cholecystokinin and isoproterenol caused no significant change in pancreatic duct EAR. A combination of amiloride and bafilomycin A1, inhibitors, respectively, of Na/H exchange and of vacuolar type H-ATPase activity, caused a dramatic drop in EAR but did not fully inhibit the increase in EAR elicited by carbachol, suggesting that other mechanisms may contribute to agonist-stimulated EAR of pancreatic ducts. CONCLUSIONS: Thus, the results support the use of microphysiometry as a tool to study pancreatic duct physiology and in particular a method to measure acid efflux from the serosal surface.

Acids↗
PubMed2004

Dynamic ion channel activation scheduling in patch clamp on a chip.

In 2002, Fertig et al. made a remarkable invention: the first successful demonstration of a patch clamp on a chip--a planar quartz-based biological chip that contains up to several hundred ion channels. This patch-clamp chip can be used in massively parallel screens for ion channel activity, thereby providing a high-throughput screening tool for drug discovery efforts. In this paper, we propose computationally efficient dynamic stochastic scheduling algorithms for activating individual ion channels in the patch-clamp chip. By formulating the ion channel activation scheduling problem as a partially observed Markov decision process with a multiarmed bandit structure, near-optimal dynamic scheduling for activation of the individual channels is achieved to optimize the information gained from the patch-clamp chip. Numerical examples using state-of-the-art algorithms developed recently in artificial intelligence and operations research are presented to illustrate these dynamic ion channel (macromolecule) activation scheduling algorithms.

Algorithms↗
PubMed2005

Microchip technology in ion-channel research.

The electrical activity of living cells can be monitored in various ways, but for the study of ion channels and the drugs that affect them, the patch-clamp techniques are the most sensitive. Recent developments in microfabricated patch-clamp electrodes are reviewed, and technical challenges for the future are discussed.

Action Potentials↗
PubMed2006

Microchip, reverse transcription-polymerase chain reaction and culture methods to detect enterovirus infection in pediatric patients.

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.

Child↗
PubMed2005

Assessing phylogenetic relationships of Lycium samples using RAPD and entropy theory.

AIM: To evaluate the phylogenetic relationships among related species of Lycium samples. METHODS: Random amplified polymorphic DNA (RAPD) fingerprinting and lab-on-a-chip electrophoresis techniques were used to analyze the characteristics of Lycium species. Seven species and 3 varieties of Lycium were studied. Based on RAPD fingerprint data obtained from 11 primers, we proposed a new index, called dispersivity, using entropy theory and projection methods to depict the diversity of the DNA fingerprints. RESULTS: Using the proposed dispersivity, primers were sorted and the dendrograms of the 7 species and 3 varieties of Lycium were constructed synthetically by merging primer information. CONCLUSION: Phylogenetic relationships among Lycium samples were constructed synthetically based on RAPD fingerprint data generated from 11 primers.

DNA Fingerprinting↗
PubMed2005

Recently available techniques applicable to genetic problems in the Middle East.

In this paper, we address the preventive health aspects of genetic problems in the Middle East and provide guidelines to prioritize preventive strategies. Applications of various novel genetic techniques such as comprehensive neonatal screening, high throughput heterozygote detection, preimplantation genetic diagnosis, Affymetrix systems, the NanoChip system and a new way of sensitive karyotyping for single-cell chromosome abnormalities are discussed. In conclusion, from the various genetic techniques available, each country should adopt strategies most suitable to its genetic needs and should prioritize the programs to be used in prevention.

Chromosome Aberrations↗
PubMed2006

Dynamic responses of single cardiomyocytes to graded ischemia studied by oxygen clamp in on-chip picochambers.

Single mouse cardiomyocytes were exposed to defined ischemia. We designed chambers on glass chips with a volume of 192 pL (picochambers). After a picochamber was loaded with a single cardiomyocyte, P(O2) in the picochamber was equilibrated with that in the headspace, where it was controlled in the critical range between <0.2 and 10 mm Hg. Because the extracellular fluid volume in a picochamber was restricted, these conditions are close to tissue ischemia. Responses of the sarcolemmal K(ATP)-channel current (I(KATP)), the production of reactive oxygen species (ROS), and the mitochondrial membrane potential (delta psi) of single cardiomyocytes to graded ischemia and, in particular, to rapid changes of the ischemic grade by defined oxygen steps were studied. The results show that I(KATP) is readily activated during ischemia and that the grade of ischemia tightly controls the amplitude of I(KATP). Furthermore, maximal ischemia-induced I(KATP) was similar when it followed either reoxygenation or reperfusion, suggesting that there is no major autocrine modulation of maximal I(KATP) during ischemia. A P(O2) staircase from <0.2 to 10 mm Hg increased the ROS signal, starting already at a P(O2) of approximately 0.3 mm Hg. With a similar P(O2) staircase, delta psi first hyperpolarized and then, above 1 mm Hg, depolarized. The depolarizing response of delta psi at a P(O2) of >1 mm Hg could be blocked by increasing the antioxidant defense with glutathione-monoethyl ester. It is concluded that in an ischemic cardiomyocyte I(KATP) is essentially controlled by Po(2) and that at low P(O2) delta psi is balanced by oxygen-induced hyperpolarization and ROS-induced depolarization.

Animals↗
PubMed2005

The Oral Fluid MEMS/NEMS Chip (OFMNC): diagnostic and translational applications.

The ability to monitor health status, disease onset and progression, and treatment outcome through non-invasive means is a most desirable goal in health-care promotion and delivery. There are three prerequisites for this goal to be realized: specific biomarkers associated with a health or disease state, a non-invasive approach to detect and monitor the biomarkers, and the technologies to discriminate between and among the biomarkers. We present a roadmap to achieve these goals using oral fluids as the diagnostic medium to scrutinize the health and/or disease status of individuals. This is an ideal opportunity to bridge state-of-the-art micro-/nano-electromechanical system (MEMS/NEMS) sensors to oral fluid for diagnostic applications. As the "mirror of body", oral fluid is a perfect medium to be explored for health and disease surveillance. The translational applications and opportunities are enormous.

Biomarkers↗
PubMed2005

Rapid, accurate and precise quantitative drug analysis: comparing liquid chromatography tandem mass spectrometry and chip-based nanoelectrospray ionisation mass spectrometry.

We have developed a liquid chromatography tandem mass spectrometry (LC-MS/MS) system capable of achieving better than 2% accuracy, routinely over a wide concentration range of 1800 ng mL-1. We demonstrate that the necessary high precision, high accuracy and rapid analysis can be achieved using LC-MS/MS technology. Automated nanoelectrospray ionisation tandem mass spectrometry (nanoESI-MS/MS) technology can be employed to eliminate the chromatographic step completely. In this paper, nanoESI-MS/MS is evaluated and compared directly with LC-MS/MS for the quantitative analysis of two-test analytes, amitriptyline (ATT) and 5-methoxytryptamine (5-MTT), in aqueous/organic mixture. Calibration curves were found to be linear over a wide concentration range of 1800 ng mL-1 for both analytes using LC-MS/MS. Using nanoESI-MS/MS ATT gave a linear response while 5-MTT gave a non-linear response using nanoESI-MS/MS over the same concentration range as in LC-MS/MS. Accuracy and precision values of quality control samples (QCs) at four concentration levels were analysed in replicates of six at each level using 5-MTT and ATT as test analytes for both techniques. The LC-MS/MS system was capable of achieving accuracy levels of 99.50101.96% for ATT and 100.17100.40% for 5-MTT. Accuracy levels using nanoESI-MS/MS were not comparable to LC-MS/MS, they ranged from 90.09100.18% for ATT and 95.95113.55% for 5-MTT. The precision values obtained for nanoESI-MS/MS were in good agreement with those obtained by LC-MS/MS.

5-Methoxytryptamine↗
PubMed2006

Single-molecule detection sensitivity using planar integrated optics on a chip.

We present a fully planar integrated optical approach to single-molecule detection based on microfabricated planar networks of intersecting solid and liquid-core waveguides. We study fluorescence from dye molecules in liquid-core antiresonant reflecting optical waveguides, and demonstrate subpicoliter excitation volumes, parallel excitation through multiple pump waveguides, and single-molecule detection sensitivity. Integrated silicon photonics combined with single-molecule detection in solution create a compact, robust, and sensitive platform that has applications in numerous fields ranging from atomic physics to the life sciences.

Biopolymers↗