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1.
Digital bioanalysis 总被引:3,自引:1,他引:2
Digital microfluidics has recently emerged as a new paradigm in the world of lab-on-a-chip technology. A wide variety of bioanalyses
have been successfully implemented in this format. This paper reviews the various techniques that have been adapted to digital
microfluidic systems, and the current state of the field.
Figure A multiplexed digital microfluidic device. Six analytical platforms are wired in series, allowing multiple independent analyses
to be performed simultaneously from a single set of controls. 相似文献
2.
Ute Pyell Wendelin Bücking Carolin Huhn Barbara Herrmann Alexey Merkoulov Joachim Mannhardt Hartmut Jungclas Thomas Nann 《Analytical and bioanalytical chemistry》2009,395(6):1681-1691
Although colloidal nanoparticles show an electrophoretic heterogeneity under the conditions of capillary electrophoresis,
which can be either due to the particle-size distribution and/or the particle shape distribution and/or the zeta-potential
distribution, they can form correct isotachophoretic zones with sharp-moving boundaries. Therefore, the technique of isotachophoresis
permits to generate plugs in which the co-ions and counter ions of the original colloidal solution are removed and replaced
by the buffering counter ions of the leading electrolyte. It is shown that analytical isotachophoresis can be used to measure
directly, without calibration, the molar (particle) concentration of dispersed ionic colloids provided that the transference
number and the mean effective charge number of the particles (within the isotachophoretic zone) can be determined with adequate
accuracy. The method can also be used to measure directly the effective charge number of biomacromolecules or colloidal particles,
if solutions with known molar (particle) concentration can be prepared. The validity of the approach was confirmed for a model
solution containing a known molar concentration of bovine serum albumin.
相似文献
3.
Tastet L Schaumlöffel D Bouyssiere B Lobinski R 《Analytical and bioanalytical chemistry》2006,385(5):948-953
A method based on ICP collision-cell MS detection in capillary HPLC was developed to gain an insight into the purity and identity of selenium-containing proteins separated by 1-D and 2-D electrophoresis. The bands and spots obtained after the separation of water-soluble proteins in selenized yeast were digested with trypsin prior to chromatography. Selenium could be detected down to the subpicogram level. The method, assisted by information obtained by MALDI TOF MS on the 5000 Da cut-off fraction, permitted the purity of bands and spots to be estimated and the efficiency of tryptic digestion and the quantity of selenium present in individual peptides to be evaluated. Owing to the high sensitivity and the lack of matrix suppression effects, the method provided chromatograms with signal-to-noise ratios of 10–1000 in conditions where the common ES Q–TOF MS detection failed.
相似文献
4.
Solution-enhanced dispersion by supercritical fluids (SEDS) was applied to produce nano-sized recombinant human growth hormone
(hGH) particles. Ethanol was used to help the supercritical carbon dioxide to extract water from the aqueous protein solution.
Various sizes of hGH nanoparticles were successfully prepared with a narrow particle size distribution from aqueous ethanol
solution without using any additive. The theoretical particle sizes were deduced from the calculated droplet sizes based on
a modified Jasuja’s equation. The calculated mean particle sizes and the experimentally obtained ones were compared and the
results showed an excellent correlation coefficient (R
2) of 0.995.
Figure Distribution of hGH Nano-particles 相似文献
5.
Emily O’Neill Danielle Harrington John Allison 《Analytical and bioanalytical chemistry》2009,393(8):2029-2038
Monitoring of cell cultures in microbioreactors is a crucial task in cell bioassays and toxicological tests. In this work
a novel tool based on a miniaturized sensor array fabricated using low-temperature cofired ceramics (LTCC) technology is presented.
The developed device is applied to the monitoring of cell-culture media change, detection of the growth of various species,
and in toxicological studies performed with the use of cells. Noninvasive monitoring performed with the LTCC microelectrode
array can be applied for future cell-engineering purposes.
Figure Microelectrode array for monitoring of cell cultures 相似文献
6.
Boettcher M Jaeger M Kirschbaum M Mueller T Schnelle T Duschl C 《Analytical and bioanalytical chemistry》2008,390(3):857-863
We present a simple lab-on-chip device for handling small samples of delicate cells, e.g. stem cells. It uses a combination
of sedimentation and dielectrophoresis. The transport of cells is driven by gravitation. Dielectrophoresis uses radio-frequency
electric fields for generating particle-selective forces dependent on size and polarisability. Electrodes along the channels
hold particles and/or cells in a defined position and deflect them towards different outlets. The absence of external pumping
and the integration of injection and sampling ports allow the processing of tiny sample volumes. Various functions are demonstrated,
such as contact-free cell trapping and cell/particle sorting. Pairs of human cells and antibody-coated beads, as they are
formed for T cell activation, are separated from unbound beads. The cells experience only low stress levels compared with
the stress levels in dielectrophoresis systems, where transport depends on external pumping. Our device is a versatile yet
simple tool that finds applications in cellular biotechnology, in particular when an economic solution is required.
Figure A simple gravitation-driven lab-on-chip device for the separation of mixed populations of microparticles or cells by negative
dielectrophoresis. 相似文献
7.
A method based on use of functionalized gold nanoparticles on polyethylenimine film has been developed for colorimetric detection of immunoglobulin G (IgG). The immunogold nanoparticles were immobilized on quartz slides by recognition between antibody and antigen, with the antigen chemically adsorbed on the polyethylenimine film. By measurement of the UV–visible spectra of the immobilized immunogold, detection of h-IgG was achieved. The detection limit for h-IgG by use of this method can be as low as 0.01 μg mL−1. This method is quite promising for numerous applications in immunoassay.
Figure 相似文献
8.
Upon adsorbing on a solid-state substrate, water-soluble proteins are prone to denaturation and deterioration of their functions
due to the conformation change. The surface electric field of a conductive substrate is one of the important factors that
influence the character of adsorbed proteins. In this work, a 3D macroporous gold electrode has been prepared and served as
the working electrode to study the influence of surface electric field on the adsorption kinetics and conformation of the
adsorbed cytochrome c (cyt-c) with the help of electrochemical, in situ electrochemical IR spectroscopic, atomic force microscopic,
and contact angle measurements. The external electric field creates excess surface charge which can manipulate the adsorption
rate of proteins on the substrate by the enhanced electrostatic interactions between the electrode and protein patches by
coupling with complementary charges. The amount of immobilized cyt-c with electrochemical activity on the 3D macroporous gold
electrode showed a minimum at potential of zero charge (PZC) and it increased with increasing net excess surface charge. Higher
electric field could influence the conformation and the corresponding properties such as direct electrochemistry, bioactivity,
and surface character of the adsorbed cyt-c molecules. However, high external electric field leads to damage of the protein
secondary structure. This study provides fundamentals for the fabrication of biomolecular devices, biosensors, and biofuel
cells through electrostatic interactions.
Figure Two cases are illustrated for the protein immobilized on electrode surfaces: a retention of protein structure under moderate excess surface charge, b denaturation and conformation change of proteins adsorbed at high excess surface charge, e.g., due to the higher external
electric field. 相似文献
9.
Sum-frequency generation (SFG) is a nonlinear laser-spectroscopy technique suitable for analysis of adsorbed molecules. The
sub-monolayer sensitivity of SFG spectroscopy enables vibrational spectra to be obtained with high specificity for a variety
of molecules on a range of surfaces, including metals, oxides, and semiconductors. The use of ultra-short laser pulses on
time-scales of picoseconds also makes time-resolved measurements possible; this can reveal ultrafast transient changes in
molecular arrangements. This article reviews recent time-resolved SFG spectroscopy studies revealing site-hopping of adsorbed
CO on metal surfaces and the dynamics of energy relaxation at water/metal interfaces.
Time-resolved sum frequency generation spectroscopy at surfaces with non-resonant laser pulse irradiation 相似文献
10.
Lieberzeit PA Afzal A Glanzing G Dickert FL 《Analytical and bioanalytical chemistry》2007,389(2):441-446
Titanate sol–gel layers imprinted with midchain carbonic acids have proven highly useful for detecting engine oil degradation
processes owing to selective incorporation of oxidised base oil components. Synthesising the material from TiCl4 in CCl4 and precipitating with water leads to imprinted TiO2 nanoparticles with a diameter of 200–300 nm. Replacing the water by a 1 M ammonium hydroxide solution reduces the average
particle size to 50–100 nm with retention of the interaction capabilities. Experiments with the latter solution revealed that
the 100-nm particles take up substantially more analyte, indicating a size-dependent phenomenon. As the number of interaction
sites within each material is the same, this cannot be a consequence of thermodynamics but must be one of accessibility. The
sensor characteristic of water-precipitated particles towards engine oil degradation products shows substantially increased
sensitivity and dynamic range compared with the corresponding thin films. Coating quartz crystal microbalances with such nanoparticle
materials leads to engine oil degradation sensors owing to incorporation of acidic base oil oxidation products. Interaction
studies over a large range of layer thicknesses revealed that both the absolute signal and the steepness of the correlation
between the sensor signal and the layer height is 2 times higher for the particles.
Figure Generation of molecularly imprinted sol–gel nanoparticles 相似文献
11.
Cruz Enriquez A Rivero Espejel IA Andrés García E Díaz-García ME 《Analytical and bioanalytical chemistry》2008,391(3):807-815
The interaction of 11-mercaptoundecanoic acid capped gold nanoparticles (MUA-GNPs) with europium ions and aminoacids has been
studied by UV-Vis spectrophotometry, fluorescence, confocal fluorescence microscopy, resonance light scattering and TEM. Results
demonstrated that hyper-Rayleigh scattering emission occurs upon the addition of lysine to the MUA-GNPs–Eu(III) system, thus
providing an inherently sensitive method for lysine determination. The effects of geometrical factors of the gold nanoparticles
(aspect ratio, particle size, cluster formation) and the surrounding medium (pH) on this behavior are discussed. The cooperative
binding interactions of Eu3+ and lysine with gold nanoparticles permitted the discrimination of lysine from other amino acids. The probable mechanism
for the spectral changes and the enhanced resonance light scattering observed is outlined.
Figure Gold nanoparticle resonance light scattering plasmon enhancement through cooperative binding with europium and lysine 相似文献
12.
Environmental analysis is a potential key application for chemical sensors owing to their inherent ability to detect analytes
on-line and in real time in distributed systems. Operating a chemosensor in a natural environment poses substantial challenges
in terms of ruggedness, long-term stability and calibration. This article highlights current trends of achieving both the
necessary selectivity and ruggedness: one way is deploying sensor arrays consisting of robust broadband sensors and extracting
information via chemometrics. If using only a single sensor is desired, molecularly imprinted polymers offer a straightforward
way for designing artificial recognition materials. Molecularly imprinted polymers can be utilized in real-life environments,
such as water and air, aiming at detecting analytes ranging from small molecules to entire cells.
Figure 相似文献
13.
Nan Li Hui Tang Hongwei Gai Xiuling Dong Qi Wang Edward S. Yeung 《Analytical and bioanalytical chemistry》2009,394(7):1879-1885
Determination of protein surface excess is an important way of evaluating the properties of biomaterials and the characteristics
of biosensors. A single-molecule counting method is presented that uses a standard fluorescence microscope to measure coverage
of a liquid/solid interface by adsorbed proteins. The extremely low surface excess of lysozyme and bovine serum albumin (BSA),
in a bulk concentration range from 0.3 nmol L−1 (0.02 μg mL−1) to 3 nmol L−1 (0.2 μg mL−1), were measured by recording the counts of spatially isolated single molecules on either hydrophilic (glass) or hydrophobic
(polydimethylsiloxane, PDMS) surfaces at different pH. The differences observed in amounts of adsorbed proteins under different
experimental conditions can be qualitatively explained by the combined interactions of electrostatic and hydrophobic forces.
This, in turn, implies that single-molecule counting is an effective way of measuring surface coverage at a liquid/solid interface.
Figure Adsorption fraction of proteins on different surfaces changed with pH. 相似文献
14.
Jung C 《Analytical and bioanalytical chemistry》2008,392(6):1031-1058
Cytochrome P450 proteins (CYPs) are a big class of heme proteins which are involved in various metabolic processes of living
organisms. CYPs are the terminal catalytically active components of monooxygenase systems where the substrate binds and is
hydroxylated. In order to be functionally competent, the protein structures of CYPs possess specific properties that must
be explored in order to understand structure–function relationships and mechanistic aspects. Fourier transform infrared spectroscopy
(FTIR) is one tool that is used to study these structural properties. The application of FTIR spectroscopy to the secondary
structures of CYP proteins, protein unfolding, protein–protein interactions and the structure and dynamics of the CYP heme
pocket is reviewed. A comparison with other thiolate heme proteins (nitric oxide synthase and chloroperoxidase) is also included.
Figure The protein secondary structure, protein unfolding, redox-partner protein–protein interaction, structural changes induced
by the reduction of the heme iron, and the structure and dynamics of the active site of cytochromes P450 (CYP) can be studied
using Fourier transform infrared spectroscopy (FTIR). FTIR spectroscopy is a good approach for gaining a deeper insight into
structure–function relationships in CYPs.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
Anna Evans Anja Bieberle-Hütter Henning Galinski Jennifer L. M. Rupp Thomas Ryll Barbara Scherrer René Tölke Ludwig J. Gauckler 《Monatshefte für Chemie / Chemical Monthly》2009,140(9):975-983
Abstract Micro-solid oxide fuel cells (micro-SOFC) are predicted to be of high energy density and are potential power sources for portable
electronic devices. A micro-SOFC system consists of a fuel cell comprising a positive electrode-electrolyte-negative electrode
(i.e. PEN) element, a gas-processing unit, and a thermal system where processing is based on micro-electro-mechanical-systems
fabrication techniques. A possible system approach is presented. The critical properties of the thin film materials used in
the PEN membrane are discussed, and the unsolved subtasks related to micro-SOFC membrane development are pointed out. Such
a micro-SOFC system approach seems feasible and offers a promising alternative to state-of-the-art batteries in portable electronics.
Graphical abstract Graphical Abstract text
相似文献
16.
Möhrle BP Köhler K Jaehrling J Brock R Gauglitz G 《Analytical and bioanalytical chemistry》2006,384(2):407-413
Reflectometric interference spectroscopy (RIfS) is a label-free, time-resolved technique for detecting interactions of molecules
immobilized on a surface with ligands in solution. Here we show that RIfS also permits the detection of the adhesion of tissue
culture cells to a functionalized surface in a flow system. Interactions of T cells with other leukocytes or epithelial cells
of blood vessels are crucial steps in the regulating immune response and inflammatory reactions. Jurkat T cell leukemia cells
rapidly attached to a transducer functionalized with a monoclonal antibody directed against the T cell receptor (TCR)/CD3
complex, followed by activation-dependent cell spreading. RIfS curves were obtained for the Jurkat derivative JCaM 1.6 (which
lacks the key signaling protein Lck), cells preincubated with cytochalasin D (an inhibitor of actin polymerization), and for
surfaces functionalized with an antibody directed against the coreceptor CD28. These curves differed with respect to the maximum
signal and the initial slope of the increase in optical thickness. The testing of chemical inhibitors, cell surface molecules
and gene products relevant to a key event in T cell immunity illustrates the potential of label-free techniques for the analysis
of activation-dependent cell-surface contacts.
The first two authors contributed equally to this paper 相似文献
17.
The use of electrochemical impedance spectroscopy for biosensing 总被引:1,自引:0,他引:1
This review introduces the basic concepts and terms associated with impedance and techniques of measuring impedance. The focus
of this review is on the application of this transduction method for sensing purposes. Examples of its use in combination
with enzymes, antibodies, DNA and with cells will be described. Important fields of application include immune and nucleic
acid analysis. Special attention is devoted to the various electrode design and amplification schemes developed for sensitivity
enhancement. Electrolyte insulator semiconductor (EIS) structures will be treated separately.
Figure An alternating current which is forced to pass an interface is sensitive to surface changes and will detect impedance changes
due to biomolecule immobilisation or formation of a recognition complex. This can be used for the construction of biosensor
electrodes 相似文献
18.
The detection and identification of dilute bacterial samples by surface-enhanced Raman spectroscopy has been explored by mixing
aqueous suspensions of bacteria with a suspension of nanocolloidal silver particles. An estimate of the detection limit of
E. coli was obtained by varying the concentration of bacteria. By correcting the Raman spectra for the broad librational OH band
of water, reproducible spectra were obtained for E. coli concentrations as low as approximately 103 cfu/mL. To aid in the assignment of Raman bands, spectra for E. coli in D2O are also reported.
Figure Light scattering apparatus used to detect bacteria 相似文献
19.
Moschou EA Nicholson AD Jia G Zoval JV Madou MJ Bachas LG Daunert S 《Analytical and bioanalytical chemistry》2006,385(3):596-605
This work demonstrates the development of microfluidic compact discs (CDs) for protein purification and fractionation integrating a series of microfluidic features, such as microreservoirs, microchannels, and microfluidic fractionators. The CDs were fabricated with polydimethylsiloxane (PDMS), and each device contained multiple identical microfluidic patterns. Each pattern employed a microfluidic fractionation feature with operation that was based on the redirection of fluid into an isolation chamber as a result of an overflow. This feature offers the advantage of automated operation without the need for any external manipulation, which is independent of the size and the charge of the fractionated molecules. The performance of the microfluidic fractionator was evaluated by its integration into a protein purification microfluidic architecture. The microfluidic architecture employed a microchamber that accommodated a monolithic microcolumn, the fractionator, and an isolation chamber, which was also utilized for the optical detection of the purified protein. The monolithic microcolumn was polymerized “in situ” on the CD from a monolith precursor solution by microwave-initiated polymerization. This technique enabled the fast, efficient, and simultaneous polymerization of monoliths on disposable CD microfluidic platforms. The design of the CD employed allows the integration of various processes on a single microfluidic device, including protein purification, fractionation, isolation, and detection.
相似文献
20.
Stefaniak AB Brink CA Dickerson RM Day GA Brisson MJ Hoover MD Scripsick RC 《Analytical and bioanalytical chemistry》2007,387(7):2411-2417
Complete digestion of all chemical forms and sizes of particulate analytes in environmental samples is usually necessary to
obtain accurate results with atomic spectroscopy. In the current study, we investigate the physicochemical properties of beryllium
particles likely to be encountered in samples collected from different occupational environments and present a hypothesis
that a dissolution theory can be used as a conceptual framework to guide development of strategies for digestion procedures.
For monodisperse single-chemical constituent primary particles, such as those encountered when handling some types of beryllium
oxide (BeO) powder, theory predicts that a digestion procedure is sufficient when it completely dissolves all primary particles,
independent of cluster size. For polydisperse single-chemical constituent particles, such as those encountered during the
handling of some types of beryllium metal powder, theory predicts that a digestion procedure is sufficient only when it completely
dissolves the largest particle in the sample. For samples with unknown or multi-chemical constituent particles and with particles
having undefined sizes, e.g., fume emissions from a copper–beryllium alloy furnace operation or dust from a beryl ore crushing
operation, a surface area-limited and single-constituent-dependent dissolution theory may not predict complete dissolution,
thereby requiring non-routine robust treatment procedures with post-digestion filtration, followed by examination of residual
particulate material. Additionally, for beryllium, and likely other poorly soluble materials, particulate reference materials
of various chemical forms and size distributions are needed to better evaluate and harmonize analytical digestion procedures.
Figure Generation of aerosol particles during machining of beryllium oxide
The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National
Institute for Occupational Safety and Health. 相似文献