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At least 19 recordsLinked to original sources
PubMed1992

[Biosensing techniques for the laboratory medicine].

Biosensing techniques are utilized in micro analysis of the biological constituents with an integrated device. Their applications to laboratory medicine are of great interest. Recently, several types of micro electrodes or ion sensitive field effect transistors (ISOFET) were developed. For fabrication of the biosensor selection of the proper bio-element and transducer to assay our sample, is important. In this article we will indicate some items on the future prospect of biosensing techniques for laboratory medicine.

Biosensing Techniques↗
PubMed2006

Theoretical and experimental analysis of arrayed imaging reflectometry as a sensitive proteomics technique.

Arrayed imaging reflectometry (AIR) is a newly developed label-free optical biosensing technique based on the creation and perturbation of a condition of zero reflectance on a silicon substrate. The antireflective coating is formed by covalently immobilizing arrayed probes on a silicon dioxide film. Probe-target complex formation causes a localized increase in optical thickness and a measurable reflectance change. To evaluate the performance of AIR, we have employed two proteins, intimin and tir, from enteropathogenic E. coli that are critical to the bacterium's mechanism of host infection. Using substrates functionalized with the intimin-binding domain of tir, we demonstrate detection of the extracellular domain of intimin at concentrations as low as 10 pM. Through the use of a diffusion-limited model for the intimin-tir binding interaction at this concentration, we estimate the detected intimin surface concentration to be 0.33 pg/mm2.

Adhesins, Bacterial↗
PubMed2006

Hydration dependence of conformational dielectric relaxation of lysozyme.

Dielectric response of hen egg white lysozyme is measured in the far infrared (5-65 cm-1, 0.15-1.95 THz, 0.6-8.1 meV) as a function of hydration. The frequency range is associated with collective vibrational modes of protein tertiary structure. The observed frequency dependence of the absorbance is broad and glass-like. For the entire frequency range, there is a slight increase in both the absorbance and index of refraction with increasing hydration for <0.27 h (mass of H2O per unit mass protein). At 0.27 h, the absorbance and index begin to increase more rapidly. This transition corresponds to the point where the first hydration shell is filled. The abrupt increase in dielectric response cannot be fully accounted for by the additional contribution to the dielectric response due to bulk water, suggesting that the protein has not yet achieved its fully hydrated state. The broad, glass-like response suggests that at low hydrations, the low frequency conformational hen egg white lysozyme dynamics can be described by a dielectric relaxation model where the protein relaxes to different local minima in the conformational energy landscape. However, the low frequency complex permittivity does not allow for a pure relaxational mechanism. The data can best be modeled with a single low frequency resonance (nu approximately 120 GHz=4 cm-1) and a single Debye relaxation process (tau approximately .03-.04 ps). Terahertz dielectric response is currently being considered as a possible biosensing technique and the results demonstrate the required hydration control necessary for reliable biosensor applications.

Animals↗
PubMed1997

A biosensor that uses ion-channel switches.

Biosensors are molecular sensors that combine a biological recognition mechanism with a physical transduction technique. They provide a new class of inexpensive, portable instrument that permit sophisticated analytical measurements to be undertaken rapidly at decentralized locations. However, the adoption of biosensors for practical applications other than the measurement of blood glucose is currently limited by the expense, insensitivity and inflexibility of the available transduction methods. Here we describe the development of a biosensing technique in which the conductance of a population of molecular ion channels is switched by the recognition event. The approach mimics biological sensory functions and can be used with most types of receptor, including antibodies and nucleotides. The technique is very flexible and even in its simplest form it is sensitive to picomolar concentrations of proteins. The sensor is essentially an impedance element whose dimensions can readily be reduced to become an integral component of a microelectronic circuit. It may be used in a wide range of applications and in complex media, including blood. These uses might include cell typing, the detection of large proteins, viruses, antibodies, DNA, electrolytes, drugs, pesticides and other low-molecular-weight compounds.

Biosensing Techniques↗
PubMed2004

Highly sensitive differential phase-sensitive surface plasmon resonance biosensor based on the Mach-Zehnder configuration.

A high-sensitivity surface plasmon resonance (SPR) biosensor based on the Mach-Zehnder interferometer design is presented. The novel feature of the new design is the use of a Wollaston prism through which the phase quantities of the p and s polarizations are interrogated simultaneously. Since SPR affects only the p polarization, the signal due to the s polarization can be used as the reference. Consequently, the differential phase between the two polarizations allows us to eliminate all common-path phase noise while keeping the phase change caused by the SPR effect. Experimental results obtained from glycerin-water mixtures indicate that the sensitivity limit of our scheme is 5.5 x 10(-8) refractive-index units per 0.01 degrees phase change. To our knowledge, this is a significant improvement over previously obtained results when gold was used as the sensor surface. Such an improvement in the sensitivity limit should allow SPR biosensors to become a possible replacement for conventional biosensing techniques based on fluorescence. Monitoring of the bovine serum albumin (BSA) binding reaction with BSA antibodies is also demonstrated.

Antigen-Antibody Complex↗
PubMed2005

Immunodetection of pentamer and modified C-reactive protein using surface plasmon resonance biosensing.

In clinical practices, the examination of pentamer C-reactive protein (pCRP) is commonly used as a prognostic indicator of the risk of a patient developing cardiovascular disease (CVD). Structural modification of pCRP produces a modified CRP (mCRP) which exhibits different biological activities in the body. In recent years, mCRP has come to be regarded as a more powerful inducer than pCRP, and hence mCRP measurement has emerged as an important indicator for assessing the risk of developing CVD. The surface plasmon resonance (SPR) biosensing technique can be employed to increase the detection accuracy and real-time response when sensing pCRP or mCRP. In this study, three monoclonal antibodies (Mabs), C8, 8D8, and 9C9, are immobilized on a protein G layer for subsequent CRP detection. The experimental results reveal that the Mab C8 reacts with both pCRP and mCRP, the Mab 8D8 with pCRP, and the Mab 9C9 with mCRP. No false signals caused by non-specific binding are observed. When detecting pCRP using Mab C8, the SPR bioassay provides sufficient sensitivity to evaluate whether or not a patient is at risk of developing CVD. SPR biosensing provides a viable and accurate approach for the real-time evaluation of pCRP and mCRP levels, and is therefore of considerable benefit in clinical examinations of CPR.

Antibodies, Monoclonal↗
PubMed2006

QCM detection of DNA targets with single-base mutation based on DNA ligase reaction and biocatalyzed deposition amplification.

A novel biosensing technique for highly specific identification of gene with single-base mutation is proposed based on the implementation of the DNA ligase reaction and the biocatalyzed deposition of an insoluble product. The target gene mediated deposition of an insoluble precipitate is then transduced by quartz crystal microbalance (QCM) measurements. In this method, the DNA target hybridizes with a capture DNA probe tethered onto the gold electrode and then with a biotinylated allele-specific detection DNA. A ligase reaction is performed to generate the ligation between the capture and the detection probes, provided there is perfect match between the DNA target and the detection probe. Otherwise even when there is an allele mismatch between them, no ligation would take place. After thermal treatment at an elevated temperature, the formed duplex melts apart that merely allows the detection probe perfectly matched with the target to remain on the electrode surface. The presence of the biotinylated allele-matched probe is then detected by the QCM via the binding to streptavidin-peroxide horseradish (SA-HRP), which catalyzes the oxidative precipitation of 3,3-diaminobenzidine (DAB) by H2O2 on the electrode and provides an amplified frequency response. The proposed approach has been successfully implemented for the identification of single-base mutation in -28 site of the beta-thalassemia gene with a detection limit of 0.1 nM, demonstrating that this method provides a highly specific and cost-efficient approach for point mutation detection.

Biosensing Techniques↗
PubMed1992

A biosensor for L-proline determination by use of immobilized microbial cells.

A biosensor to quantify L-proline within 10(-5)-10(-3) mole/L concentration is described. Immobilized Pseudomonas sp. cells grown in a medium containing L-proline as the only source of carbon and nitrogen were used to create the biosensor. The cells oxidized L-proline specifically consuming O2 and did not react with other amino acids and sugars. The change in oxygen concentration was detected with a Clark oxygen membrane electrode. The cells were immobilized by entrapment in polyvinyl alcohol (PVA) cryogel. The resultant biocatalyst had a high mechanical strength and retained its L-proline-oxidizing ability for at least two months.

Adenosine Triphosphate↗
PubMed1993

Control of microbial activity by flow injection analysis during high cell density cultivation of Escherichia coli.

The application of an automated flow injection analysis (FIA) system for on-line determination of microbial activity, during high cell density cultivations of Escherichia coli is reported. Based on a bioelectrochemical principle, the FIA method used a redox mediator (potassium hexacyanoferrate(III)) to facilitate electron transfer from the microorganisms to an electrochemical detector. Assays were carried out using a new sampling device which provided aseptic operation by use of a valve and chemical sterilisation. No sample dilution or pretreatment was necessary for biomass concentrations up to approx. 40 g l-1. The sample volume was 0.5 ml and the overall analysis time was 5 min. FIA signals were found to correlate well with the oxygen uptake rate (OUR). Changes in metabolic activity due to low substrate levels or high inhibitor concentrations in the cultivation medium became obvious from the FIA signals.

Bacteriological Techniques↗
PubMed1991

Microbial sensor system for nondestructive evaluation of fish meat quality.

A microbial sensor system consisting of the bacterium (Alteromonas putrefaciens) immobilized within membranes, a flow cell, an oxygen electrode, peristaltic pumps, a buffer tank, a thermostatically controlled bath and a recorder, was constructed for the nondestructive quality evaluation of bluefin tuna. The chemical compounds on fish meat surfaces which are the indicators of fish meat quality were rapidly determined by using the proposed sensor system. Fish meat quality was determined from the rate of current decrease of the sensor. Good correlations were obtained between fish meat quality and sensor response. One assay could be completed within one minute.

Animals↗
PubMed1996

Microbial detection.

There is a widespread need for commercial instrumentation for the rapid and inexpensive detection of microbial contamination of food, industrial waste water and clinical samples. A large number of detection methods have been developed utilizing the optical, electrochemical, biochemical and physical properties of microorganisms. The need for a device which can produce a rapid, accurate, sensitive, real-time analysis for clinical, industrial and environmental applications has led to considerable progress being achieved in recent years in the development of biosensors for microbial detection. This intense research has resulted in the commercialization of several instruments. Techniques used for the quantification of microorganisms are reviewed under the general categories of non-bioelectrochemical and bioelectrochemical methods.

Bacteriological Techniques↗
PubMed1995

The development of single molecule environmental sensors.

The participants at the meeting reflected the broad range of expertise that is required to realize improved methods for extremely high sensitivity or single molecule detection. It is quite clear that the answers lie at the interface of biology, chemistry, engineering and molecular design.

Bacteria↗
PubMed2005

Advances in preservation methods: keeping biosensor microorganisms alive and active.

The ability of bacteria to sense their surroundings can be employed to measure the bioavailability and toxicity of pollutants. However, long-term maintenance of both viability and activity of the sensor bacteria is required for the development of cell-based devices for environmental monitoring. To meet these demands, various techniques to conserve such bacteria have been reported, including freeze drying, vacuum drying, continuous cultivation, and immobilisation in biocompatible polymers of organic or inorganic origin. Much effort has been invested in merging these bacterial preservation schemes with the construction of sensor cell arrays on platforms such as biochips or optic fibres, hopefully leading to effective miniaturised whole-cell biosensor systems. These approaches hold much promise for the future. Nevertheless, their eventual implementation in practical devices calls for significant enhancement of current knowledge on formulation of reporter microorganisms.

Bacteria↗
PubMed2005

Biosensor signal amplification of vesicles functionalized with glycolipid for colorimetric detection of Escherichia coli.

A supramolecular assembly of phospholipid-polymerized diacetylene vesicles functionalized with glycolipid can provide a molecular recognition function. The Escherichia coli-glycolipid binding event leads to a visible color change from blue to red, readily seen with the naked eye and quantified by absorption spectroscopy. The biosensor signal is amplified through a suitable increase of phospholipid content in the mixed lipid vesicles and pH of aqueous solutions.

Acetylene↗
PubMed2005

The SOS-LUX-TOXICITY-Test on the International Space Station.

For the safety of astronauts and to ensure the stability and integrity of the genome of microorganisms and plants used in bioregenerative life support systems, it is important to improve our knowledge of the combined action of (space) radiation and microgravity. The SOS-LUX-TOXICITY test, as part of the TRIPLE-LUX project (accepted for flight at Biolab in Columbus on the International Space Station, (ISS)), will provide an estimation of the health risk resulting from exposure of astronauts to the radiation environment of space in microgravity. The project will: (i) increase our knowledge of biological/health threatening action of space radiation and enzymatic DNA repair; (ii) uncover cellular mechanisms of synergistic interaction of microgravity and space radiation; (iii) provide specified biosensors for spacecraft milieu examination; and (iv) provide experimental data on stability and integrity of bacterial DNA in spacecrafts. In the bacterial biosensor "SOS-LUX-Test" developed at DLR (patent), bacteria are transformed with the pBR322-derived plasmid pPLS-1 or the similar, advanced plasmid SWITCH, both carrying the promoterless lux operon of Photobacterium leiognathi as the reporter element controlled by a DNA damage-dependent SOS promoter as sensor element. A short description of the space experiment is given, and the current status of adaptation of the SOS-LUX-Test to the ISS, i.e. first results of sterilization, biocompatibility and functional tests performed with the already available hardware and bread board model of the automated space hardware under development, is described here.

Bacteriological Techniques↗
PubMed1998

Bioluminescence-based assays for detection and characterization of bacteria and chemicals in clinical laboratories.

OBJECTIVES: To survey recent advances in the application of bioluminescence to public health problems. The usefulness of bacterial (lux) and eucaryotic (luc) luciferase genes is presented, along with several examples that demonstrate their value as "reporters" of many endpoints of clinical concern. CONCLUSIONS: The development of new technologies for monitoring biological and chemical contaminants is in continuous progress. Recent excitement in this area has come from the use of genes encoding enzymes for bioluminescence as reporter systems. Applications of the recombinant luciferase reporter phage concept now provide a sensitive approach for bacterial detection, their viability, and sensitivity to antimicrobial agents. Moreover, a number of fusions of the lux and luc genes to stress inducible genes in different bacteria can allow a real-time measurement of gene expression and determination of cellular viability, and also constitute a new tool to detect toxic chemicals and their bioavailability.

Animals↗
PubMed2000

Rapid and sensitive biosensor for Salmonella.

The rapid and sensitive detection of Salmonella typhymurium based on the use of a polyclonal antibody immobilized by the Langmuir-Blodgett method on the surface of a quartz crystal acoustic wave device was demonstrated. The binding of bacteria to the surface changed the crystal resonance parameters; these were quantified by the output voltage of the sensor instrumentation. The sensor had a lower detection limit of a few hundred cells/ml, and a response time of < 100 s over the range of 10(2)-10(10) cells/ml. The sensor response was linear between bacterial concentrations of 10(2)-10(7) cells/ml, with a sensitivity of 18 mV/decade. The binding of bacteria was specific with two binding sites needed to bind a single cell. The sensors preserve approximately 75% of their sensitivity over a period of 32 days.

Animals↗
PubMed2003

Rapid identification of viable Escherichia coli subspecies with an electrochemical screen-printed biosensor array.

Rapid identification of Escherichia coli strains is an important diagnostic goal in applied medicine as well as the environmental and food sciences. This paper reports an electrochemical, screen-printed biosensor array, where selective recognition is accomplished using lectins that recognize and bind to cell-surface lipopolysaccharides and coulometric transduction exploits non-native external oxidants to monitor respiratory cycle activity in lectin-bound cells. Ten different lectins were separately immobilized onto porous membranes that feature activated surfaces (ImmunodyneABC). Modified membranes were exposed to untreated E. coli cultures for 30 min, rinsed, and layered over the individual screen-printed carbon electrodes of the sensor array. The membranes were were incubated 5 min in a reagent solution that contained the oxidants menadione and ferricyanide as well as the respiratory substrates succinate and formate. Electrochemical oxidation of ferrocyanide for 2 min provided chronocoulometric data related to the quantities of bound cells. These screen-printed sensor arrays were used in conjunction with factor analysis for the rapid identification of four E. coli subspecies (E. coli B, E. coli Neotype, E. coli JM105 and E. coli HB101). Systematic examination of lectin-binding patterns showed that these four E. coli subspecies are readily distinguished using only five essential lectins.

Agglutination Tests↗