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At least 1,099 records · Page 61Linked to original sources
PubMed2005

Environmental microbiology-on-a-chip and its future impacts.

Rapid advances in microfabrication, DNA and protein microarray and microfluidic technologies have enabled the development of fully-integrated, miniaturized systems. These so called 'laboratory-on-a-chip' (LOC) devices perform sample preparation (i.e. concentration, separation and purification) together with biochemical reactions and detection steps in a simple and automated manner. We believe LOC technology for environmental microbiology studies will have immediate impacts on microbial monitoring by achieving detection and identification within minutes at the single-cell level, and on microbial ecology by deepening the understanding of microbial community structure and diversity and correlating these with niche-specific functions within a micro space. In the long run, significant impacts are anticipated on environmental metagenomics and proteomics.

Environmental Microbiology↗
PubMed2005

Aptamer-derived nucleic acid oligos: applications to develop nucleic acid chips to analyze proteins and small ligands.

The specificity and affinity of aptamers for their cognate ligands are comparable to those of antibodies for antigens. To use aptamers effectively in high-throughput assays in a microarray format, to analyze various analytes, we developed a strategy in which the aptamer was split into two nonfunctional units and allowed to reassemble into the functional aptamer by the cognate ligand. We have named this method "analyte-dependent oligonucleotide modulation assay" (ADONMA). As proof-of-principle, we used oligonucleotides derived from the aptamer RNA against HIV-1 Tat and demonstrated, with both titer plates and plastic slide chips, that specifically in the presence of Tat or its peptide, the two oligos reconstituted the core binding regions of Tat. Thus, these results suggest that ADNOMA has the potential for use in nucleic acid microarrays for detecting various ligands.

Aptamers, Nucleotide↗
PubMed2005

Temperature alternation by an on-chip microheater to reveal enzymatic activity of beta-galactosidase at high temperatures.

A method to measure enzymatic activity at high temperatures by rapid temperature alternation of a microreactor with a microheater is proposed. On-chip microreactor and microheater were integrated on a glass plate by MEMS technology; this microheater can control the temperature of the microreactor with a response speed of 34.2 and 31.5 K/s for temperature rise and fall, respectively, with an accuracy of 3 degrees C. The enzyme, beta-galactosidase, was revealed to survive short exposure (4-s pulses) to temperatures above that which would "normally" denature them. Its activity at 60 degrees C was revealed to be approximately 4 times greater than that at room temperature. This method not only gives new kinetic information in biochemistry but also enables application in highly sensitive biosensors.

Hot Temperature↗
PubMed2006

Future lab-on-a-chip technologies for interrogating individual molecules.

Advances in technology have allowed chemical sampling with high spatial resolution and the manipulation and measurement of individual molecules. Adaptation of these approaches to lab-on-a-chip formats is providing a new class of research tools for the investigation of biochemistry and life processes.

Lab-On-A-Chip Devices↗
PubMed2004

Thin chip microsprayer system coupled to quadrupole time-of-flight mass spectrometer for glycoconjugate analysis.

A thin chip polymer-based microsprayer has been coupled to a hybrid quadrupole time-of-flight mass spectrometer (QTOF MS) and introduced in carbohydrate research. The feasibility of the approach is demonstrated for mapping, sequencing and structural elucidation of glycoconjugates originating from human body fluids and tissues such as a glycopeptide mixture from normal human urine and an isolated and purified GT1 ganglioside fraction from normal adult human brain. The optimization procedure required by each glycoconjugate category is described and the advantages of the system in terms of flexibility and adaptability to QTOF MS, stability of the ESI MS signal, carbohydrate ionization and sequencing, sensitivity, speed of analysis and sample consumption are discussed.

Amino Acids↗
PubMed2006

Development and optimization of a lab-on-a-chip device for the measurement of trace nitrogen dioxide gas in the atmosphere.

We propose the use of lab-on-a-chip technology for measuring gaseous chemical pollutants, and describe the development of a microchip for the detection of nitrogen dioxide (NO2) in air. A microchip fabricated from quartz glass has been developed for handling the following three functions, gas absorption, chemical reaction and fluorescence detection. Channels constructed in the microchip were covered with porous glass plates, allowing nitrogen dioxide to penetrate into the triethanolamine (TEA) flowing within the microchannel beneath. The nitrogen dioxide was then mixed with TEA and reacted with a suitable fluorescence reagent in the chemical reaction chamber in the microchip. The reacted solution was then allowed to flow into the fluorescence detection area to be excited by an ultraviolet light-emitting diode (UV-LED), and the fluorescence was detected using a photomultiplier tube (PMT). The reaction time, reagent concentration, pH, flow rate and other measurement conditions were optimised for analysis of nitrogen dioxide in air. Preliminary studies with standardized test solutions revealed quantitative measurements of nitrite ion (NO2-), which corresponded to atmospheric nitrogen dioxide in the range of 10-80 ppbv.

Air Pollutants↗
PubMed2006

Lab-on-a-chip devices for global health: past studies and future opportunities.

A rapidly emerging field in lab-on-a-chip (LOC) research is the development of devices to improve the health of people in developing countries. In this review, we identify diseases that are most in need of new health technologies, discuss special design criteria for LOC devices to be deployed in a variety of resource-poor settings, and review past research into LOC devices for global health. We focus mainly on diagnostics, the nearest-term application in this field.

Clinical Chemistry Tests↗
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↗
PubMed1999

DNA chip technology.

A mini-revolution is sweeping the world of science and medicine. DNA chip or microarray technology will have a more profound impact than other recent major advances, including DNA sequencing and the polymerase chain reaction (PCR). This mini-review explains the technology, its scope, and impact on science and medicine, as well as its cost and possible limitations.

Chromosome Mapping↗
PubMed1997

Integrated multichannel microchip electrospray ionization mass spectrometry: analysis of peptides from on-chip tryptic digestion of melittin.

In continuation of our work to develop an integrated multichannel microchip interfaced to electrospray mass spectrometry (ESI-MS), this paper demonstrates one of several applications of this approach in monitoring tryptic digestion products. The multichannel microchip allowed integration of sample preparation onto the microchip to facilitate the analysis process. Melittin was selected as a model oligopeptide because it possesses a cluster of four adjacent basic residues which enable probing the site specificity of trypsin as a function of digest times. Reactions were performed on-chip in different wells for specific time periods and then analyzed by infusion from the microchip by ESI-MS, using leucine enkephalin as internal standard. The rate of formation and disappearance of the molecular ion and individual fragments was followed for a melittin to trypsin concentration ratio of 300:1. The results indicate the potential of integrating enzymatic reactions with multichannel microchip ESI-MS for automated optimization of reaction condition while consuming only small amounts of sample.

Amino Acid Sequence↗
PubMed1996

Comparative genomic hybridization imaging by the one-chip true-color CCD camera kappa CF 15 MC.

In comparative genomic hybridization (CGH), quantitative measurement of fluorescence intensity ratios on metaphase chromosomes is the basic method for detecting copy number changes in the test DNA. The microscope images are usually acquired by high-resolution, highly sensitive, black and white (B&W) CCD cameras. This requires subsequent recording of the different color images using appropriate filter combinations for excitation and emission. We describe an alternative approach using the one-chip true-color CCD camera Kappa CF 15 MC and an Omega triple-bandpass filter for simultaneous registration of the three dyes Texas red, FTTC, and DAPI. A detailed examination of the imaging properties of the system was performed. The camera response in the three color planes R, G, and B was evaluated, and calibration factors for image correction were calculated. An error estimate is given. A complete computer program for the image analysis of CGH experiments has been developed for an 80486 PC, using the commercially available software package Optimas as the basis for image recording. Examples that confirm the suitability of the system for ratio imaging in CGH are presented. The results were compared with others obtained from the same microscope slides using an established setup consisting of a B&W CCD camera (Photometrics) and a software program based on the TCL software package and run on a Macintosh Quadra 950. The results obtained using the two different systems were found to correspond closely.

Calibration↗
PubMed2000

Active microeletronic chip devices which utilize controlled electrophoretic fields for multiplex DNA hybridization and other genomic applications.

Microelectronic DNA chip devices that contain planar arrays of microelectrodes have been developed for multiplex DNA hybridization and a variety of genomic research and DNA diagnostic applications. These devices are able to produce almost any desired electric field configuration on their surface. This ability to produce well-defined electric fields allows charged molecules (DNA, RNA, proteins, enzymes, antibodies, nanobeads, and even micron scale semiconductor devices) to be electrophoretically transported to or from any microlocation on the planar surface of the device. Of key importance to the device function is the permeation layer which overcoats the microelectrodes. The permeation layer is generally a porous hydrogel material that allows water molecules and small ions (Na+, CI-, etc.) to freely contact the microelectrode surface, but impedes the transport of the larger analytes (oligonucleotides, DNA, RNA, proteins, etc.). The permeation layer prevents the destruction of DNA at the active microelectrode surface, ameliorates the adverse effects of electrolysis products on the sensitive hybridization reactions, and serves as a porous support structure for attaching DNA probes and other molecules to the array. In order to maintain rapid transport of DNA molecules, facilitate hybridization, and work within constrained current and voltage ranges, low conductance buffers and various electronic pulsing scenarios have also been developed. These active microelectronic array devices allow electrophoretic fields to be used to carry out accelerated DNA hybridization reactions and to improve selectivity for single nucleotide polymorphism (SNP), short tandem repeat (STR), and point mutation analysis.

Animals↗
PubMed2000

On-chip chiral and achiral separation of amphetamine and related compounds labeled with 4-fluoro-7-nitrobenzofurazane.

Amphetamine and analogous compounds have been labeled with 4-fluoro-7-nitrobenzofurazane and analyzed on a microfabricated chip. Separation of norephedrine, ephedrine, cathinone, pseudoephedrine, methcathinone, amphetamine and methamphetamine is demonstrated using micellar electrokinetic capillary chromatography (MEKC) and laser-induced fluorescence (LIF) detection. Chiral separations of individual drugs were studied using neutral and negatively charged cyclodextrins (CDs) with and without the addition of an organic modifier and/or sodium dodecyl sulfate (SDS). The best results were obtained using a highly sulfated gamma-CD (HS-gamm-CD) in combination with a low concentration of SDS. To obtain complete separation of a mixture of (+/-)-norephedrine, (+/-)ephedrine, (+/-)-pseudoephedrine, (+/-)-methcathinone, (+/-)-amphetamine and (+/-)-methamphetamine it was necessary to add a small amount (1.5 mM) of SDS to the separation buffer. Optimized chiral separation was achieved within 7 min using an S-folded separation channel, a separation voltage of 8 kV and a buffer consisting of 50 mM phosphate (pH 7.35), 10 mM HS-gamma-CD and 1.5 mM SDS.

4-Chloro-7-nitrobenzofurazan↗
PubMed2001

Fabrication and evaluation of a carbon-based dual-electrode detector for poly(dimethylsiloxane) electrophoresis chips.

The first carbon-based dual-electrode detector for microchip capillary electrophoresis (CE) is described. The poly(dimethylsiloxane) (PDMS)-based microchip CE devices were constructed by reversibly sealing a PDMS layer containing separation and injection channels to another PDMS layer containing carbon fiber working electrodes. End-channel amperometric detection was employed and the performance of the chip was evaluated using catechol. The response was found to be linear between 1 and 600 microM with an experimentally determined limit of detection (LOD) of 500 nM and a sensitivity of 30 pA/microM. Collection efficiencies for catechol ranged from 36.0 to 43.7% at field strengths of 260-615 V/cm. The selectivity that can be gained with these devices is demonstrated by the first CE-based dual-electrode detection of a Cu(II) peptide complex. These devices illustrate the potential for a rugged and easily constructed microchip CE system with an integrated carbon-based detector of similar scale.

Carbon↗
PubMed2001

Design of an interface to allow microfluidic electrophoresis chips to drink from the fire hose of the external environment.

An interface design is presented that facilitates automated sample introduction into an electrokinetic microchip, without perturbing the liquids within the microfluidic device. The design utilizes an interface flow channel with a volume flow resistance that is 0.54-4.1 x 10(6) times lower than the volume flow resistance of the electrokinetic fluid manifold used for mixing, reaction, separation, and analysis. A channel, 300 microm deep, 1 mm wide and 15-20 mm long, was etched in glass substrates to create the sample introduction channel (SIC) for a manifold of electrokinetic flow channels in the range of 10-13 microm depth and 36-275 microm width. Volume flow rates of up to 1 mL/min were pumped through the SIC without perturbing the solutions within the electrokinetic channel manifold. Calculations support this observation, suggesting a leakage flow to electroosmotic flow ratio of 0.1:1% in the electrokinetic channels, arising from 66-700 microL/min pressure-driven flow rates in the SIC. Peak heights for capillary electrophoresis separations in the electrokinetic flow manifold showed no dependence on whether the SIC pump was on or off. On-chip mixing, reaction and separation of anti-ovalbumin and ovalbumin could be performed with good quantitative results, independent of the SIC pump operation. Reproducibility of injection performance, estimated from peak height variations, ranged from 1.5-4%, depending upon the device design and the sample composition.

Animals↗
PubMed2001

A capillary electrophoresis chip for the analysis of print and film photographic developing agents in commercial processing solutions using indirect fluorescence detection.

The separation and detection of both print and film developing agents (CD-3 and CD-4) in photographic processing solutions using chip-based capillary electrophoresis is presented. For simultaneous detection of both analytes under identical experimental conditions a buffer pH of 11.9 is used to partially ionise the analytes. Detection is made possible by indirect fluorescence, where the ions of the analytes displace the anionic fluorescing buffer ion to create negative peaks. Under optimal conditions, both analytes can be analyzed within 30 s. The limits of detection for CD-3 and CD-4 are 0.17 mM and 0.39 mM, respectively. The applicability of the method for the analysis of seasoned photographic processing developer solutions is also examined.

Buffers↗
PubMed2001

Mass spectrometry meets chip technology: a new proteomic tool in cancer research?

DNA chip technologies are the most exiting genomic tools, which were developed within the last few years. It is, however, evident that knowledge of the gene sequence or the quantity of gene expression is not sufficient to predict the biological nature and function of a protein. This can be particularly important in cancer research where post-translational modifications of a protein can specifically contribute to the disease. To address this problem, several proteomic tools have been developed. Currently the most widely used proteomic tool is two-dimensional protein gel electrophoresis (2-DE), which can display protein expression patterns to a high degree of resolution. As an alternative to 2-DE, a preliminary study using a new technique was employed to generate protein expression patterns from whole tissue extracts. Surface-enhanced laser desorption/ionization (SELDI) allows the retention of proteins on a solid-phase chromatographic surface (ProteinChip Array) with direct detection of retained proteins by time of flight-mass spectrometry (TOF-MS). Using this system, we analyzed eight cases of renal cell carcinoma (RCC) including normal, peripheral and central tumor tissue as well as four microdissected cases of cervical intraepithelial neoplasia (CIN) and three microdissected cases of cervix uteri carcinoma. Differentially expressed proteins were found by comparing the protein expression patterns generated using SELDI-based TOF-MS of tumor tissue with normal and neoplastic tissue, respectively. By applying this fast and powerful ProteinChip array technology it becomes possible to investigate complex changes at the protein level in cancer associated with tumor development and progression.

Carcinoma, Renal Cell↗
PubMed2001

Isotachophoresis separations of enantiomers on a planar chip with coupled separation channels.

The use of a poly(methylmethacrylate) chip, provided with a pair of on-line coupled separation channels and on-column conductivity detectors, to isotachophoresis (ITP) separations of optical isomers was investigated. Single-column ITP, ITP in the tandem-coupled columns, and concentration-cascade ITP in the tandem-coupled columns were employed in this investigation using tryptophan enantiomers as model analytes. Although providing a high production rate (about 2 pmol of a pure tryptophan enantiomer separated per second), single-column ITP was found suitable only to the analysis of samples containing the enantiomers at close concentrations. A 94-mm separation path in ITP with the tandem-coupled separation channels made possible a complete resolution of a 1.5 nmol amount of the racemic mixture of the enantiomers. However, this led only to a moderate extension of the concentration range within which the enantiomers could be simultaneously quantified. The best results in this respect were achieved by using a concentration-cascade of the leading anions in the tandem-coupled separation channels. Here, a high production rate, favored in the first separation channel, was followed by the ITP migration of the enantiomers in the second channel under the electrolyte conditions enhancing their detectabilities. In dependence on the migration configuration of the enantiomers, this technique made possible their simultaneous determinations when their ratios in the loaded sample were 35:1 or less (D-tryptophan a major constituent) and 70:1 or less (L-tryptophan a major constituent).

Anions↗