SEARCH · PubMed Health

Results for “biosensor”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55Linked to original sources

PubMed2004

Dynamic formation of optically trapped microstructure arrays for biosensor applications.

We explore the dynamic properties of multiple-beam optical traps to manipulate arrays of microstructures for biosensor applications. Multiple optical traps are generated by a virtually loss-less transformation of input phase patterns into high-intensity trapping-beams. A direct image projection of the phase patterns enables an adjustable number of optical traps in addition to instantaneous control of the position, size, shape and intensity of each trapping-beam. We present experimental results showing various colloidal formations through dynamic optical manipulation of polystyrene microspheres and yeast cells in aqueous media. The experimental configurations are geared towards the use of multiple-beam optical traps for biosensor applications.

Biosensing Techniques↗

PubMed2004

A biosensor for the determination of amylase activity.

A new biosensing flow injection method for the determination of alpha-amylase activity has been introduced. The method is based on the analysis of maltose produced during the hydrolysis of starch in the presence of alpha-amylase. Maltose determination in the flow system was allowed by the application of peroxide electrode equipped with an enzyme membrane. The membrane was obtained by immobilisation of glucose oxidase, alpha-glucosidase and optionally mutarotase on a cellophane, co-crosslinked by gelatin-glutaraldehyde together with bovine serum albumine. alpha-Glucosidase hydrolyses maltose to alpha-D-glucose, which is converted to beta-D-glucose by mutarotase. beta-D-Glucose is then determined via glucose oxidase. The new biosensor has the limit of detection of 50 nmol l(-1) maltose, which means 2 nkat ml(-1) in alpha-amylase activity units, when the reaction time of amylase was 5 min (determined with respect to a signal-to-noise ratio 3:1). When the reaction time of alpha-amylase was 30 min, the limit of detection was 0.5 nkat ml(-1). A linear range of current response was 0.1-3 mmol l(-1) maltose, with a response time of 35s. The biosensor was stable at least two months and retained 70% of its original activity (with mutarotase the stability is decreased to 3 weeks). When the enzyme membrane was stored in a dry state at 4 degrees C in a refrigerator, the lifetime was approximately 6 months (with mutarotase only 3 months).

Biosensing Techniques↗

PubMed2004

Synergetic effect for NADH oxidation of ferrocene and zeolite in modified carbon paste electrodes. New approach for dehydrogenase based biosensors.

The development of electrochemical biosensors using dehydrogenases associated with the corresponding cofactor is strongly related to the better understanding of NADH oxidation at the electrode surface. The aim is to lower the necessary overvoltage and consequently to escape interferences and electrode fouling. In this paper, we show that carbon paste electrode (CPE) modified with NaY zeolite fulfils this requirements thanks to its hydrophilic surface. Oxidation of NADH at ferrocene (FcH) modified carbon paste electrode exhibits a rather slow electrocatalytic effect. We demonstrated the existence of synergetic effect on the electrocatalytic oxidation of NADH when the CPE is doped with zeolite (NaY) and FcH mediator or with the zeolite exchanged beforehand with the mediator (Y-Ferricinium, YFcH). This cumulative effect permits to reach high sensitivity for NADH detection and offers new way for the development of enzymatic biosensors using dehydrogenases depending on NADH as cofactor.

Biosensing Techniques↗

PubMed2004

Sonochemically fabricated microelectrode arrays for biosensors offering widespread applicability: Part I.

A novel and patented procedure is described for the sonochemical fabrication of a new class of microelectrode array based sensor with electrode element populations of up to 2 x 10(5) cm(-2). For some years it has been accepted that microelectrode arrays offer an attractive route for lowering minimum limits of detection and imparting stir (convectional mass transport) independence to sensor responses; despite this no commercial biosensors, to date, have employed microelectrode arrays, largely due to the cost of conventional fabrication routes that have not proved commercially viable for disposable devices. Biosensors formed by our sonochemical approach offer unrivalled sensitivity and impart stir independence to sensor responses. This format lends itself for mass fabrication due to the simplicity and inexpensiveness of the approach; in the first instance impedimetric and amperometric sensors are reported for glucose as model systems. Sensors already developed for ethanol, oxalate and a number of pesticide determinations will be reported in subsequent publications.

Biosensing Techniques↗

PubMed2004

HRP/[Zn-Cr-ABTS] redox clay-based biosensor: design and optimization for cyanide detection.

A novel inexpensive and simple amperometric biosensor, based on the immobilization of HRP into redox active [Zn-Cr-ABTS] layered double hydroxide, is applied to the determination of cyanide. The electrochemical transduction step corresponds to the reduction at 0.0 V of ABTS+* enzymatically formed in the presence of H2O2. The biosensor has a fast response to H2O2 (8s) with a linear range of 1.7 x 10(-9) to 2.1 x 10(-6) M and a sensitivity of 875 mA M(-1) cm(-2). The apparent Michaelis-Menten constant (KMapp) is 12 microM. The detection of cyanide is performed via its non competitive inhibiting action on the HRP/[Zn-Cr-ABTS] electrode. The concentration range of the linear response and the apparent inhibition constant (ki) are 5 x 10(-9) to 4 x 10(-8) and 1.4 x 10 (-7) M, respectively.

Aluminum Silicates↗

PubMed2004

A bioelectrochemical polypyrrole-containing Fe(CN)6(3-) interface for the design of a NAD-dependent reagentless biosensor.

Ferricyanide ions were immobilized on a platinum electrode surface by means of an electrochemically grown polypyrrole film. The entrapped Fe(CN)6(3-)/Fe(CN)6(4-) redox system displayed a high heterogeneous electron transfer rate. The resulting modified electrode was efficient for the ferricyanide-mediated NADH oxidation catalyzed by a diaphorase. The bioelectrochemical interface was applied to the design of a reagentless amperometric D-lactate biosensor. A weakly polarized two polypyrrole-containing Fe(CN)6(3-) modified electrode system was involved without any reference. An enzymatic solution containing D-lactate dehydrogenase, diaphorase and NAD-dextran was further confined on the sensing electrode using a semi-permeable membrane. The sensitivity and the response time of the reagentless biosensor were similar to those of the analogous sensor working with soluble mediator and cofactor, i.e. 25 microA mM(-1) cm(-2) and 120 s, respectively. The other analytical performances were less satisfactorily: the detection limit was 5 x 10 mmol L(-1) and the linearity range was comprised between 0.1 and 0.5 mmol L(-1).

Biosensing Techniques↗

PubMed2004

Versatile method of cholinesterase immobilisation via affinity bonds using Concanavalin A applied to the construction of a screen-printed biosensor.

Development of new and more reliable methods to immobilise biomolecules has emerged rapidly due to a continuous need for more stable, sensitive and reliable biosensors. This paper reports a new method of acetylcholine-esterase (AChE) immobilisation based on the high affinity interaction between the glycoproteic enzyme and Concanavalin A (Con A). In order to establish the nature of the link formed between the glycoenzyme, lectin and support, three different configurations are presented. The optimum immobilisation procedure was further used for biosensor manufacturing. The non-specific adsorption is around 3% and the chemical cross-linking of the proteins is avoided. The optimised method allows loading of the working electrode surface with different amounts of enzyme ranging from 0.3 to 3.3 mIU with a good operational stability. The sensor showed a linear response range to acetylthiocholine substrate between 10 and 110 micromol l(-1) with a sensitivity of 3.6 mA l mol(-1). The applicability of the method to the detection of organophosphorus insecticides resulted in a detection limit of 10(-8) mol l(-1) for chlorpyriphos.

Biosensing Techniques↗

PubMed2004

Short-term BOD (BODst) as a parameter for on-line monitoring of biological treatment process. Part I. A novel design of BOD biosensor for easy renewal of bio-receptor.

A novel design of a biochemical oxygen demand (BOD) biosensor has been developed for on-line monitoring of easily biodegradable organic compounds in aqueous samples. The biological recognition element of the sensor could be easily renewed by injecting new bacterial paste without disassembling the sensor system. The sensor measurements were carried out in the initial-rate mode using a flow injection (FI) system, resulting in 60 s for one sample analysis followed by a recovery time less than 10 min. The sensor performance achieved showed a wide detection linearity over the range of 5-700 mg BOD5.l(-1) and a generally good agreement between the BOD values estimated by the biosensor and the conventional 5-day test. Furthermore, the precision test was in the control range (i.e. repeatability < or = /+/-7.5%/, reproducibility < or = /+/-7.3%/). The sensor could be used over 1 week in continuous test, however, the best performance was found within the first 24 h where standard deviation of the sensor response was +/-2.4%. The design of the sensor allows easy and fast renewal of the cells used as sensing elements. Replacement of biological recognition element and calibration of the sensor responses can be performed in a rather simple procedure on a daily regular basis. By using a mixed culture as the bio-receptor, one gets a sensor that reacts to a wide range of substrates. The new sensor construction will thus allow fast and convenient replacement of the bio-receptor and on-line assay of a broad range of substrates. This makes the sensor being an interesting and promising candidate for on-line monitoring of biological treatment process.

Bacteria, Aerobic↗

PubMed2004

In situ measurement of degranulation as a biosensor based on RBL-2H3 mast cells.

A direct degranulation assay has been developed to enable the use of RBL mast cells as a biosensor for screening chemical libraries for drug discovery and environmental toxicity evaluation. Release of beta-hexosaminidase into the extracellular milleu is widely used to characterize cellular components and mechanisms involved in stimulated exocytosis, including those initiated by crosslinking of IgE receptors on mast cells. To adapt this versatile assay for high throughput screening, we developed a direct, in situ method in which beta-hexosaminidase detection is carried out in a single step, convenient for multi-sample processing and thus for biosensor applications. This direct assay is efficient for measuring exocytosis in antigen-stimulated RBL mast cells, detecting antigen concentrations as low as 1 pM. We also demonstrate its utility in detecting inhibition of degranulation by a known pharmacologic inhibitor that blocks Syk tyrosine kinase activity critical for cell activation.

Animals↗

PubMed2004

Development of acetylcholinesterase silica sol-gel immobilized biosensor--an application towards oxydemeton methyl detection.

An amperometric silica sol-gel film immobilized biosensor doped with acetylcholinesterase was fabricated in the laboratory finding application in organophosphate detection based on enzyme inhibition. The substrate used was acetylthiocholine chloride and thiocholine released from the enzymatic hydrolysis was electrochemically oxidized giving larger anodic current at 0.5-0.6 V (versus Ag/AgCl reference). The dependencies of the current response on pH, enzyme loading and thermal stability of the developed biosensor were evaluated. The analytical performance of enzyme electrode towards substrate and inhibitor was investigated. Oxydemeton methyl was taken as a model compound for the inhibition studies. Linear calibration for oxydemeton methyl was obtained in the range of 2-200 ppb under the optimized conditions following an incubation time of 20 min. Treatment of the inhibited enzyme with pyridine-2-aldehyde restored 92% of its original activity. The sensor stored at -20 degrees C had a good storage and operational stability retaining 85% of its original activity for 60 successive measurements.

Acetylcholinesterase↗

PubMed2004

Acetylcholinesterase-based biosensor electrodes for organophosphate pesticide detection. I. Modification of carbon surface for immobilization of acetylcholinesterase.

Screen-printed carbon electrodes modified with the dialdehydes, glutaraldehyde and terephthaldicarboxaldehyde, and then polyethyleneimine have been utilized for production of pesticide biosensors based on acetylcholinesterase. To improve the extent of dialdehyde modification, the electrodes were NH2-derivatized, initially by electrochemical reduction of 4-nitrobenzenediazonium to a nitroaryl radical permitting attachment to the carbon surface. Subsequent reduction of the 4-nitrobenzene yields a 4-aminobenzene modified carbon surface. Drosophila melanogaster acetylcholinesterase was immobilized either covalently onto dialdehyde modified electrodes or non-covalently onto polyethyleneimine modified electrodes. Internal diffusion limitations due to the dialdehyde and polyethyleneimine modifications increased the apparent Km of the immobilized enzyme. The thiocholine sensitivity was about 90% for dialdehyde modified electrodes and about 10% for polyethyleneimine modified electrodes as compared with non-modified carbon electrodes. The detection limit of the biosensors produced by non-covalent immobilization of acetylcholinesterase onto polyethyleneimine modified carbon electrodes was found to be about 10(-10) M for the organophosphate pesticide dichlorvos.

Acetylcholinesterase↗

PubMed2005

Characterization of a self-assembled monolayer of thiol on a gold surface and the fabrication of a biosensor chip based on surface plasmon resonance for detecting anti-GAD antibody.

A biosensor chip utilizing surface plasmon resonance (SPR) was fabricated for detecting anti-glutamic acid decarboxylase (GAD) antibody, which is an indicator of the presence of type I diabetes mellitus. The sensor surfaces were constructed from various thiol mixtures of different molar ratios of 3-mercaptopropionic acid (3-MPA) to 11-mercaptoundecanoic acid (11-MUA). To determine the surface characteristics of the different alkanethiol monolayers, several quantitative and kinetic measurements were carried out. The extent of immobilization of streptavidin (SA) and biotin-GAD (the anti-GAD receptor) and the immune response of anti-GAD antibody against GAD were measured using the SPR biosensor. The terminal functional group of a thiol has different effects on the adsorption and covalent binding of protein depending on the steric hindrance. The protein chip described herein permits simple, rapid detection of anti-GAD antibody.

Antibodies↗

PubMed2005

Glucose biosensor based on platinum microparticles dispersed in nano-fibrous polyaniline.

A sensitive and selective amperometric glucose biosensor based on platinum microparticles dispersed in nano-fibrous polyaniline (PANI) was investigated. Poly (m-phenylenediamine) (PMPD), which was employed as an anti-interferent barrier and a protective layer to platinum microparticles, was deposited onto platinum-modified PANI in the presence of glucose oxidase. The morphology of PANI, Pt/PANI and PMPD-GOD/Pt/PANI were investigated by scanning electron microscopy. The results show that PANI has a nano-fibrous morphology. The enzyme electrode exhibits excellent response performance to glucose with linear range from 2 x 10(-6) to 12 x 10(-3) M and fast response time within 7s. Due to the selective permeability of PMPD, the enzyme electrode also shows good anti-interference to uric acid and ascorbic acid. The Michaelis-Menten constant km and the maximum current density imax of the enzyme electrode were 9.34 x 10(-3) M and 917.43 microA cm(-2), respectively. Furthermore, this glucose biosensor also has good stability and reproducibility.

Aniline Compounds↗

PubMed2005

Sensitivity of cell-based biosensors to environmental variables.

Electrically active living cells cultured on extracellular electrode arrays are utilized to detect biologically active agents. Because cells are highly sensitive to environmental conditions, environmental fluctuations can elicit cellular responses that contribute to the noise in a cell-based biosensor system. Therefore, the characterization and control of environmental factors such as temperature, pH, and osmolarity is critical in such a system. The cell-based biosensor platform described here utilizes the measurement of action potentials from cardiac cells cultured on electrode arrays. A recirculating fluid flow system is presented for use in dose-response experiments that regulates temperature within +/-0.2 degrees C, pH to within +/-0.05 units, and allows no significant change in osmolarity. Using this system, the relationship between the sensor output parameters and environmental variation was quantified. Under typical experimental conditions, beat rate varied approximately 10% per degree change in temperature or per 0.1 unit change in pH. Similar relationships were measured for action potential amplitude, duration, and conduction velocity. For the specific flow system used in this work, the measured environmental sensitivity resulted in an overall beat rate variation of +/-4.7% and an overall amplitude variation of +/-3.3%. The magnitude of the noise due to environmental sensitivity has a large impact on the detection capability of the cell-based system. The significant responses to temperature, pH, and osmolarity have important implications for the use of living cells in detection systems and should be considered in the design and evaluation of such systems.

Biosensing Techniques↗

PubMed2005

Development of a commercial amperometric biosensor electrode for the ketone D-3-hydroxybutyrate.

Representatives of the common classes of quinoid NADH redox mediator, including Meldola Blue (MB) 3, 4-methyl-1,2-benzoquinone (4-MBQ) 4, 1-methoxy phenazine methosulphate (1-MeO-PMS) 5 and 2,6-dichloroindophenol (DCIP) 6, are shown to inhibit the NAD-dependent enzyme D-3-hydroxybutyrate dehydrogenase (HBDH), severely limiting their utility in the construction of a stable biosensor electrode for the ketone body D-3-hydroxybutyrate (3-OHB). It is proposed that these mediators bind covalently to important thiol groups in the enzyme. This mode of inhibition is overcome through the use of mediators such as 1,10-phenanthroline quinone (1,10-PQ) 7, which avoid 1,4-nucleophilic addition with enzyme amino acid residues such as Cys. As a result, 1,10-PQ 7 was selected for incorporation in a biosensor electrode for 3-OHB. The resulting MediSense Optiumtrade mark beta-Ketone electrode is stable (<or=10% loss in response at 30 degrees C versus 4 degrees C) with a long shelf life of 18 months. Diabetics can determine their D-3-hydroxybutyrate level with good precision (0.43 mM 3-OHB, 10.5% CV; 1.08 mM, 5.9%; 3.55 mM, 3.2%; n=20 per level) and accuracy (versus reference assay: slope=0.98; intercept=0.02 mM, r=0.97, n=120) over the range 0.0-6.0 mM in 30 s using a small volume of blood (5 microl). The electrode has a low operating potential (+200 mV versus Ag/AgCl) such that the effect of electroactive agents in blood is minimised.

3-Hydroxybutyric Acid↗

PubMed2005

Biosensor for the determination of phenols based on cross-linked enzyme crystals (CLEC) of laccase.

Cross-linked enzyme crystals (CLECs) are a versatile form of biocatalyst that can also be used for biosensor application. Laccase from Trametes versicolor (E.C.1.10.3.2) was crystallized, cross-linked and lyophilized with beta-cyclodextrin. The CLEC laccase was found to be highly active towards phenols like 2-amino phenol, guaiacol, catechol, pyrogallol, catechin and ABTS (non-phenolic). The CLEC laccase was embedded in 30% polyvinylpropylidone (PVP) gel and mounted into an electrode to make the sensor. The biosensor was used to detect the phenols in 50-1000 micromol concentration level. Phenols with lower molecular weight such as 2-amino phenol, catechol and pyrogallol gave a short response time where as the higher molecular weight substrates like catechin and ABTS had comparatively a long response time. The optimum pH of the analyte was 5.5-6.0 when catechol was used as substrate. The CLEC laccase retained good activity for over 3 months.

Biosensing Techniques↗

PubMed2005

A multi-biosensor based on immobilized Photosystem II on screen-printed electrodes for the detection of herbicides in river water.

A multi-biosensor for detection of herbicides and pollutants was constructed using various photosynthetic preparations as biosensing elements. The photosynthetic thylakoid from Spinacia oleracea L., Senecio vulgaris and its mutant resistant to atrazine were immobilized with (BSA-GA) on the surface of screen-printed sensors composed of a graphite-working electrode and Ag/AgCl reference electrode deposited on a polymeric substrate. The biosensor was composed of four flow cells with independent illumination of 650 nm to activate electron transfer in Photosystem II. The principle of the detection was based on the fact that herbicides selectively block electron transport activity in a concentration-dependent manner and that the four PSII biomediators show differential recognition activity toward herbicides. Changes of the activity were registered amperometrically as rate of photoreduction of the artificial electron acceptor DQ. The setup resulted in a reusable herbicide multibiosensor with a good stability (half-life of 16.7 h for spinach thylakoids) and limit of detection of about 10(-8) M for herbicides recovered in spring in river.

Adsorption↗

PubMed2005

Detection of TP53 mutation using a portable surface plasmon resonance DNA-based biosensor.

A DNA-based surface plasmon resonance (SPR) biosensor has been developed for the detection of TP53 mutation using the inexpensive and commercially available instrument, SPREETA SPR-EVM-BT, from Texas Instruments. A direct immobilisation procedure, based on the coupling of thiol-derivatised oligonucleotide probes (Probe-C6-SH) to bare gold sensor surfaces, was optimized using synthetic oligonucleotides. Hybridisation reactions between the immobilised probe and a short sequence (26 mer) complementary, non-complementary and one-point mutation DNA were then investigated. The main analytical parameters of the sensor system were studied in detail including selectivity, sensitivity, reproducibility and analysis time. Finally, the sensor system was successfully applied to polymerase chain reaction (PCR)-amplified real samples, DNA extracted from both normal, wild-type, (Jurkat) and mutated (Molt 4), carrying the mutation at codon 248 of the TP53 cell lines. The results obtained demonstrate that the DNA-based SPR biosensor was able to distinguish sequences present in the various samples that differ only by one base; and hence, it appears to be a strong candidate technique for the detection of gene mutation.

Biosensing Techniques↗