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At least 379 records · Page 21Linked to original sources

PubMed2001

A two-cell biosensor that couples neuronal cells to optically monitored fish chromatophores.

A two-cell biosensor was developed that uses optically detected changes in naturally colored fish chromatophores to measure the neurosecretory output of mammalian neuronal cells. The specific version of the biosensor described here is a continuous flow device that places red-pigmented, dendritic erythrophore cells directly downstream of an immobilized population of PC12 neuronal cells, a well-established model cell-line having neuroendocrine function. Agents known to stimulate catecholamine neurosecretion (secretagogues) were presented to the PC12 cells. It was found that the varying level of neurosecretion from the PC12 cells was measurable by judging the degree of pigment aggregation in the erythrophores. Increases in catecholamine secretion and consequent pigment aggregation were observed for several known secretagogues, including receptor agonists (ATP, acetylcholine), membrane depolarizing agents (high K(+) concentration), and specific neurotoxins (black widow spider venom, alpha-latrotoxin). This particular two-cell biosensor, which is applicable to the detection of any agents that affect the levels of catecholamine secretion from PC12 cells, demonstrates the general principle that the breadth of sensitivity of a biosensor is increased by employing coupled cell types.

Adenosine Triphosphate↗

PubMed2001

Design and demonstration of an automated cell-based biosensor.

Cell-based biosensors have the capacity to respond to a wide range of analytes in a physiologically relevant manner and appear well-suited for toxicity monitoring of both known and unknown analytes. One means of acquiring cellular functional information for biosensor applications involves extracellular recording from excitable cells, which can generate noninvasive and long-term measurements. Previous work from our laboratory described a prototype portable system capable of high signal-to-noise extracellular recordings, in spite of deficiencies in thermal control, fluidics handling, and absence of data acquisition (DAQ) capability. The present work describes a cell-based biosensor system that incorporates low noise amplifier and filter boards, a two-stage thermal control system with integrated fluidics and a flexible graphical user interface for DAQ and control implemented on a personal computer. Wherever possible, commercial off-the-shelf components have been utilized for system design and fabrication. The system exhibits input-referred noise levels of 5-10 microV(RMS), such that extracellular potentials exceeding 50-60 microV can be readily resolved. In addition, the biosensor system is capable of automated temperature and fluidics control. Flow rates can range from 0-2.5 ml/min, while the cell recording chamber temperature is maintained within a range of 36-37 degrees C. To demonstrate the capability of this system to resolve small extracellular potentials, recordings from embryonic chick cardiac myocytes have been performed.

Action Potentials↗

PubMed2001

Cellular biosensors for drug discovery.

Recent advances in cell biology, fluorescent probe chemistry, miniaturization and automation have allowed the use of mammalian cells in a variety of medical and industrial applications. Here we describe the generation of cell-based biosensors, engineered to optically report specific biological activity. Cellular biosensors are comprised of living cells and can be used in various applications, including screening chemical libraries for drug discovery and environmental sensing. Panels of biosensors may also be useful for elucidating the function of novel genes. Here we describe two examples of the construction and use of engineered cell lines as biosensors for drug discovery.

Animals↗

PubMed2002

A nano-molar sensitive disposable biosensor for determination of dopamine.

The studies on a nano-molar sensitive disposable biosensor based on the screen-printing basal electrode and the supramolecular assembly of dual mediators, tetramethylbenzidine and ferrocene, by beta-cyclodextrin inclusion complexation have been reported in this paper. This biosensor shows the high quality of analytical performance because of the complexation and the microenvironment in the supramolecular structure. The extracted protein of mushroom, which contains abundant polyphenol oxidase, was immobilized in the membrane of cross-linked cyclodextrin film. This biosensor responds to dopamine with high selectivity and sensitivity. Its response range on the concentration of dopamine is from 1.0 x 10(-9) to 1.0 x 10(-6) M with the detection limit as low as 5.0 x 10(-10) M. The response time reaching to 90% of its steady value is less than 60 s. The biosensor can keep its activity for at least 15 days.

Animals↗

PubMed2001

Microbial corrosion monitoring by an amperometric microbial biosensor developed using whole cell of Pseudomonas sp.

A microbial biosensor was developed for monitoring microbiologically influenced corrosion (MIC) of metallic materials in industrial systems. The Pseudomonas sp. isolated from corroded metal surface was immobilized on acetylcellulose membrane and its respiratory activity was estimated by measuring oxygen consumption. The microbial biosensor was used for the measurement of sulfuric acid in a batch culture medium contaminated by microorganisms. A linear relationship between the microbial sensor response and the concentration of sulfuric acid was observed. The response time of biosensor was 5 min and was dependent on the immobilized cell loading of Pseudomonas sp., pH, temperature and corrosive environments. The microbial biosensor response was stable, reproducible and specific for sensing of sulfur oxidizing bacterial activity.

Biosensing Techniques↗

PubMed2001

A quartz crystal microbalance cell biosensor: detection of microtubule alterations in living cells at nM nocodazole concentrations.

The quartz crystal microbalance (QCM) was used to create a piezoelectric biosensor utilizing living endothelial cells (ECs) as the biological signal transduction element. ECs adhere to the hydrophilically treated gold QCM surface under growth media containing serum. At 24 h following cell addition, calibration curves were constructed relating the steady state Deltaf and DeltaR shift values observed to the numbers of electronically counted cells requiring trypsinization to be removed from the surface. We then utilized this EC QCM biosensor for the detection of the effect of [nocodazole] on the steady state Deltaf and DeltaR shift values. Nocodazole, a known microtubule binding drug, alters the cytoskeletal properties of living cells. At the doses used in these studies (0.11-15 microM), nocodazole, in a dose dependent fashion, causes the depolymerization of microtubules in living cells. This leads a monolayer of well spread ECs to gradually occupy a smaller area, lose cell to cell contact, exhibit actin stress fibers at the cell periphery and acquire a rounded cell shape. We observed the negative Deltaf shift values and the positive DeltaR shift values to increase significantly in magnitude over a 4-h incubation period following nocodazole addition, in a dose dependent fashion, with a transition midpoint of 900 nM. Fluorescence microscopy of the ECs, fixed on the gold QCM surface and stained for actin, demonstrated that the shape and cytoskeleton of ECs were affected by as little as 330 nM nocodazole. These results indicate that the EC QCM biosensor can be used for the study of EC attachment and to detect EC cytoskeletal alterations. We suggest the potential of this cellular biosensor for the real time identification or screening of all classes of biologically active drugs or biological macromolecules that affect cellular attachment, regardless of their molecular mechanism of action.

Actins↗

PubMed2001

Soil biosensor for the detection of PAH toxicity using an immobilized recombinant bacterium and a biosurfactant.

A biosensor for detecting the toxicity of polycylic aromatic hydrocarbons (PAHs) contaminated soil has been successfully constructed using an immobilized recombinant bioluminescent bacterium, GC2 (lac::luxCDABE), which constitutively produces bioluminescence. The biosurfactant, rhamnolipids, was used to extract a model PAH, phenanthrene, and was found to enhance the bioavailability of phenanthrene via an increase in its rate of mass transfer from sorbed soil to the aqueous phase. The monitoring of phenanthrene toxicity was achieved through the measurement of the decrease in bioluminescence when a sample extracted with the biosurfactant was injected into the minibioreactor. The concentrations of phenanthrene in the aqueous phase were found to correlate well with the corresponding toxicity data obtained by using this toxicity biosensor. In addition, it was also found that the addition of glass beads to the agar media enhanced the stability of the immobilized cells. This biosensor system using a biosurfactant may be applied as an in-situ biosensor to detect the toxicity of hydrophobic contaminants in soils and for performance evaluation of PAH degradation in soils.

Biosensing Techniques↗

PubMed2002

Enhancement in the sensitivity of a gas biosensor by using an advanced immobilization of a recombinant bioluminescent bacterium.

A genetically engineered bioluminescent bacterium (lac::luxCDABE) was immobilized to develop a whole cell biosensor for the detection of toxic gaseous chemicals. The toxicity of chemicals can be evaluated through the bioluminescent reaction as it reduces in intensity when the cells experience toxic or lethal conditions. This whole cell biosensor was fabricated, using an immobilization technique utilizing solid agar medium, for the measurement of toxicity through direct contact of the cells with the gas. To enhance the sensitivity of the biosenor, glass beads were used and the thickness of the agar layer was reduced. The bioluminescent response was measured using a fiber optic probe connected between the biosensor kit and a luminometer. As sample gaseous toxic chemicals, BTEX (Benzene, Toluene, Ethylbenzene, and Xylene) gases were selected and their vapors were produced by a gas generation system. The concentrations of the gaseous chemicals injected into the chamber were controlled by the time of exposure and were measured using a portable gas chromatograph (Allstech., USA). Additions of glass beads facilitated gas diffusion through the solid medium, making the biosensor more sensitive. In addition, a thinner matrix layer was more advantageous for the detection of gas toxicity.

Bacteria↗

PubMed2002

Genetic modification of glucose oxidase for improving performance of an amperometric glucose biosensor.

Glucose oxidase (GOD) was genetically modified by adding a poly-lysine chain at the C-terminal with a peptide linker inserted between the enzyme and poly-lysine chain. The poly-lysine chain was added in order to anchor more electron transfer mediator, ferrocenecarboxylic acid, to GOD for the purpose of improving sensitivity and stability of glucose biosensors. The modified GOD had similar K(m) and K(cat) to those of the wild type enzyme. After interacted with the electron transfer mediator, the modified enzyme retained 90.01% of its native activity, while the commercial GOD and the wild type GOD (Aspergillus niger) retained only 22.43 and 22.17%, respectively. Screen-printed electrodes coated with the modified GOD, wild type yeast-derived GOD or the commercial GOD were tested in glucose solution of different concentrations. Experimental results showed that the biosensor based on the modified GOD gave the largest signal among the three. In addition, the linear range of the biosensor prepared by the modified GOD could extend to 45 mM, while they were about 20 mM for the biosensors based on the wild type yeast-derived enzyme and the commercial enzyme.

Biosensing Techniques↗

PubMed2003

Detection of organophosphate and carbamate pesticides in vegetable samples by a photothermal biosensor.

Previously developed photothermal biosensor was optimised by determining the most suitable enzyme substrate (acetylthiocholine iodide) and the optimal carrier buffer (0.05 M phosphate buffer, pH 8.0). Excitation laser operating at 488 nm and 120 mW power provided the highest biosensor sensitivity. The biosensor was tested for detection of toxic organophosphate and carbamate compounds present in samples of salad, iceberg lettuce, and onion. Sufficient sensitivities to different pesticides (carbofuran, propamocarb, oxydemeton-methyl and parathion-ethyl) were achieved without time-consuming sample preparation procedures. The results show good agreement with the concentrations of pesticides determined with standard GC-MS detection method. The developed photothermal biosensor offers new low cost means to detect low concentrations of pesticides in vegetable samples with high throughput and little or no sample pretreatment.

Biosensing Techniques↗

PubMed2002

Bio-smart hydrogels: co-joined molecular recognition and signal transduction in biosensor fabrication and drug delivery.

Two classes of polymers that are currently receiving widespread attention in biosensor development are hydrogels and conducting electroactive polymers. The present study reports on the integration of these two materials to produce electroactive hydrogel composites that physically entrap enzymes within their matrices for biosensor construction and chemically stimulated controlled release. Enhanced biosensing capabilities of these membranes have been demonstrated in the fabrication of glucose, cholesterol and galactose amperometric biosensors. All biosensors displayed extended linear response ranges (10(-5)-10(-2) M), rapid response times (<60 s), retained storage stabilities of up to 1 year, and excellent screening of the physiological interferents ascorbic acid, uric acid, and acetaminophen. When the cross-linked hydrogel components of these composite membranes were prepared with the amine containing dimethylaminoethyl methacrylate monomer the result was polymeric devices that swelled in response to pH changes (neutral to acidic). Entrapment of glucose oxidase within these materials made them glucose-responsive through the formation of gluconic acid. When insulin was co-loaded with glucose oxidase into these "bio-smart" devices, there was a twofold increase in insulin release rate when the devices were immersed in glucose solutions. This demonstrates the potential of such systems to function as a chemically-synthesized artificial pancreas.

Biocompatible Materials↗

PubMed2003

Market analysis of biosensors for food safety.

This paper is presented as an overview of the pathogen detection industry. The review includes pathogen detection markets and their prospects for the future. Potential markets include the medical, military, food, and environmental industries. Those industries combined have a market size of $563 million for pathogen detecting biosensors and are expected to grow at a compounded annual growth rate of 4.5%. The food market is further segmented into different food product industries. The overall food-pathogen testing market is expected to grow to $192 million and 34 million tests by 2005. The trend in pathogen testing emphasizes the need to commercialize biosensors for the food safety industry as legislation creates new standards for microbial monitoring. With quicker detection time and reusable features, biosensors will be important to those interested in real time diagnostics of disease causing pathogens. As the world becomes more concerned with safe food and water supply, the demand for rapid detecting biosensors will only increase.

Biological Assay↗

PubMed2003

Novel synthetic phytochelatin-based capacitive biosensor for heavy metal ion detection.

A novel capacitance biosensor based on synthetic phytochelatins for sensitive detection of heavy metals is described. Synthetic phytochelatin (Glu-Cys)(20)Gly (EC20) fused to the maltose binding domain protein was expressed in Escherichia coli and purified for construction of the biosensor. The new biosensor was able to detect Hg(2+), Cd(2+), Pb(2+), Cu(2+) and Zn(2+) ions in concentration range of 100 fM-10 mM, and the order of sensitivity was S(Zn)>S(Cu)>S(Hg)>>S(Cd) congruent with S(Pb). The biological sensing element of the sensor could be regenerated using EDTA and the storage stability of the biosensor was 15 days.

Biosensing Techniques↗

PubMed2003

Evaluation of a high throughput toxicity biosensor and comparison with a Daphnia magna bioassay.

A high throughput toxicity biosensor has been designed and constructed using recombinant Escherichia coli cells, containing stress specific promoters (recA, fabA, or katG) or constitutive promoters (lac) fused to luciferase genes originating from Vibrio fisheri. These genetically engineered cells were immobilized in 96 well plates. By optimizing cell immobilization conditions and the strains' response specificity to toxic chemicals, bioluminescent outputs decreased or increased dose-dependently upon adding test chemicals. However, to date the toxicity data obtained using this biosensor have not been compared with the results of other toxicity tests. Phenolics were chosen to evaluate the correlation between the LD50 and the EC50 (GC2) or EC120 (DPD2540) of Daphnia magna and E. coli, respectively. Toxicity data obtained from constitutive strains by bioluminescent level decrements were compared with the results from D. magna as a standard. LD50 values were used as parameters of D. magna toxicity and EC50 of EC120 values were used for the immobilized biosensor. In the DPD2540 test, phenolics, membrane damaging toxic chemicals, for testing immobilized stress specific bacterial strains trigger dose-dependant bioluminescence increase within specific concentration. Although the stress specific responsiveness from the strains could not be compared with D. magna's LD50 values, these responses offer additional information, such as upon the mode of toxic action in the sample, in addition to the cellular toxicity results as indicated by the EC50. This novel high throughput toxicity biosensor can be implemented to investigate the toxicity of any other soluble materials, and can be used as a standardization tool for the evaluation of toxicity.

Animals↗

PubMed2003

Development of a conductimetric biosensor using immobilised Rhodococcus ruber whole cells for the detection and quantification of acrylonitrile.

A conductimetric biosensor for the detection of acrylonitrile in solution was designed and characterised using whole cells of Rhodococcus ruber NCIMB 40757, which were immobilised into a disc of dimethyl silicone sponge (ImmobaSil). The biosensor described was capable of the detection and quantification of acrylonitrile in aqueous solution, having a linear response to concentrations between 2 and 50 mM (106-2650 ppm) acrylonitrile. The biosensor has been shown to be reproducible with respect to the data obtained over a number of days, and retains stability for a minimum period of at least 5 days before recalibration of the biosensor is required.

Acrylonitrile↗

PubMed2003

Amperometric cytochrome c3-based biosensor for chromate determination.

The chromate reductase activity of cytochrome c(3) (Cyt c(3), M(r) 13000), isolated from the sulfate-reducing bacterium Desulfomicrobium norvegicum, was used to develop an amperometric biosensor to measure chromate (CrO(4)(2-)) bioavailability. The performance of various biosensor configurations for qualitative and quantitative determination of Cr(VI) was studied. Biosensor properties depend on the technique used to immobilize the enzyme on the electrode (glassy carbon electrode). Immobilization of Cyt c(3) by entrapment in poly 3,4-ethylenedioxythiophene films denatured the enzyme, while application of an adsorption technique did not affect enzyme activity but the detection range was limited. The best results were obtained with dialysis membranes, which allowed the determination of Cr(VI) from 0.20 to 6.84 mg l(-1) (3.85-132 microM) with a sensitivity of 35 nA mg(-1) l (1.82 nA microM(-1)). No interference was observed with As(V), As(III) and Fe(III). Only a small amount of Cyt c(3) (372 ng of protein) was needed for this biosensor.

Biosensing Techniques↗

PubMed2003

Biosensor for rapid phosphate monitoring in a sequencing batch reactor (SBR) system.

A thick-film phosphate biosensor based on hydrogel immobilized pyruvate oxidase (POD) has been developed for rapid phosphate process control monitoring in an experimental sequencing batch reactor (SBR) system. We have employed a phosphate biosensor in an off-line monitoring of phosphate concentrations in a bench scale SBR. Measurements with biosensor show a good correlation (r2=0.98) with those of commercial colorimetric phosphate testing kits. The signal response time was 1 min with a detection limit of 5 microM. The biosensor method showed a good operational stability, needed less experimental procedures and a small sample size (approximately 20 microl). This allows its practical application for rapid phosphate measurements to obtain real time process data in a SBR system.

Bioreactors↗

PubMed1998

Electrodeposited polytyramine as an immobilisation matrix for enzyme biosensors.

The application of an electrodeposited polytyramine film as an immobilisation matrix for the construction of enzyme biosensors is described. Glucose oxidase (used as a model enzyme) is covalently attached to free amine groups on the polytyramine film using the coupling reagents 1-ethyl-3(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide. The resultant recognition interface consisted of multilayers of GOx immobilised onto the polymer surface. This method of constructing enzyme biosensors is shown to produce a highly reproducible and stable device. The biosensor showed no loss in electrode response after four months of dry storage and exhibited only minor loss in response after 20 days of repeated use. The resultant biosensor had a linear range of 0.1-28 mM glucose and a detection limit of 0.01 mM.

Biosensing Techniques↗