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At least 451 records · Page 25Linked to original sources

PubMed2005

Glucose biosensor based on carbon nanotube epoxy composites.

A novel glucose biosensor based on a rigid and renewable carbon nanotube (CNT) based biocomposite is reported. The biosensor was based on the immobilization of glucose oxidase (GOx) within the CNT epoxy-composite matrix prepared by dispersion of multi-wall CNT inside the epoxy resin. The use of CNT, as the conductive part of the composite, ensures better incorporation of enzyme into the epoxy matrix and faster electron transfer rates between the enzyme and the transducer. Experimental results show that the CNT epoxy composite biosensor (GOx-CNTEC) offers an excellent sensitivity, reliable calibration profile, and stable electrochemical properties together with significantly lower detection potential (+0.55 V) than GOx-graphite epoxy composites (+0.90 V; difference deltaE = 0.35 V). The results obtained favorably compare to those of a glucose biosensor based on a graphite epoxy composite (GOx-GEC).

Biosensing Techniques↗

PubMed2006

Optical waveguide biosensors constructed with subwavelength gratings.

The reflection resonance spectrum of a subwavelength diffraction-grating-coupled waveguide is used to analyze biomolecular interactions in real time. By detecting this resonance wavelength shift, the optical waveguide biosensor provides the ability to identify the kinetics of the biomolecular interaction on an on-line basis without the need for extrinsic labeling of the biomolecules. A theoretical analysis of the subwavelength optical waveguide biosensor is performed. A biosensor with a narrow reflection resonance spectrum, and hence an enhanced detection resolution, is then designed and fabricated. Currently, the detection limit of the optical waveguide sensor is approximately 10(-5) refractive-index units. The biosensor is successfully applied to study of the dynamic response of an antibody interaction with protein G adsorbed on the sensing surface.

Biosensing Techniques↗

PubMed2004

Enhancement of the resolution of surface plasmon resonance biosensors by control of the size and distribution of nanoparticles.

A new resolution-enhanced surface plasmon resonance (SPR) biosensor offers a tenfold improvement in resolution compared with conventional SPR biosensors in the detection of the surface coverage of biomaterials. The proposed optical biosensor, based on the attenuated total-reflection method, excites both the surface plasmons and particle plasmons to enhance the local electromagnetic field by control of the size and volume fraction of embedded Au nanoparticles to increase the resolution of the device. The SPR biosensor design is based on the Maxwell-Garnett model and the Fresnel equations, and the device is fabricated with a cosputtering deposition system.

Biocompatible Materials↗

PubMed2005

Development and testing of a green fluorescent protein-based bacterial biosensor for measuring bioavailable arsenic in contaminated groundwater samples.

A green fluorescent protein (GFP)-based bacterial biosensor for the detection of bioavailable As(III), As(V), and Sb(III) was developed and characterized. The biosensor strain Escherichia coli DH5alpha (pVLAS1) was developed based on the expression of gfp under the control of the ars promoter and the arsR gene of Staphylococcus aureus plasmid pI258. Strain DH5alpha (pVLAS1) responded mainly to As(III), As(V), and Sb(III), with the lowest detectable concentrations being 0.4, 1, and 0.75 microM, respectively, during a 2-h exposure and 0.1 microM for all three metal ions with an 8-h induction period. To assess its applicability for analyzing environmentally relevant samples, the biosensor was field-tested on shallow-well groundwater for which contaminant levels were known. Our results demonstrate that the nonpathogenic bacterial biosensor developed in the present study is useful and applicable in determining the bioavailability of arsenic with high sensitivity in contaminated groundwater samples, and they suggest a potential for its inexpensive application in field-ready tests.

Arsenic↗

PubMed2005

Degradation and movement in soil of the herbicide isoproturon analyzed by a Photosystem II-based biosensor.

We have examined the persistence and movement of a urea-type herbicide, isoproturon [IPU; 3-(4-isopropylphenyl)-1,1'-dimethylurea], in soil using a novel herbicide-detection device, the prototype of a portable electrochemical biosensor based on Photosystem II particles immobilized on printed electrodes, and evaluated its results against two other methods: (i) chlorophyll-fluorescence bioassay based on polyphasic induction curves, and (ii) standard analysis represented by liquid chromatography. The data of the herbicide's content determined in soil extracts from field experiments correlated in all three methods. The biosensor assay was effective in determining the herbicide's concentration to as low as 10(-7) M. The results of our experiments also showed the kinetics of movement, degradation, and persistence of isoproturon in various depths of soil. After 6 to 9 wk, almost half of the isoproturon was still actively present in the upper soil layers (0-10 and 10-20 cm) and only 5 to 10% of biological activity was inhibited in the deeper soil layer tested (20-30 cm). Thus, inhibition within the limit of detection of both bioassays could be observed up to 9 wk after application in all profiles (0-30 cm), whereas inhibition persisted for up to 11 wk in the upper soil profile (0-10 cm). The use of the biosensor demonstrated its possibility for making rapid and cheap phytotoxicity tests. Our biosensor can give preliminary information about the biological activity of isoproturon in hours--much faster than growth biotests that may take several days or more.

Biodegradation, Environmental↗

PubMed2000

A three-cascaded-enzymes biosensor to determine lactose concentration in raw milk.

The increasing demand for on-line measurement of milk composition directs science and industry to search for practical solutions, and biosensors may be a possibility. The specific objective of this work was to develop an electrochemical biosensor to determine lactose concentration in fresh raw milk. The sensor is based on serial reactions of three enzymes--beta-galactosidase, glucose oxidase, and horseradish peroxidase--immobilized on a glassy carbon electrode. The sequential enzymatic reactions increase the selectivity and sensitivity of the sensor. The sensor requires dilution of the raw milk and the addition of 5-aminosalicylic acid. Lactose concentrations in raw milk measured by the sensor were in good agreement with those measured by a reference laboratory using infrared technology. The results were obtained in milk samples that varied in fat and protein composition. From the results, we conclude that an electrochemical biosensor for determination of lactose concentration in fresh raw milk can be developed, and that the biosensor presented in this study maintained the qualities required for further development into an online sensor in the milking parlor.

Animals↗

PubMed1993

Biosensors: applications for dairy food industry.

Biosensors are defined as indicators of biological compounds that can be as simple as temperature-sensitive paint or as complex as DNA-RNA probes. Food microbiologists are constantly seeking rapid and reliable automated systems for the detection of biological activity. Biosensors provide sensitive, miniaturized systems that can be used to detect unwanted microbial activity or the presence of a biologically active compound, such as glucose or a pesticide. Immunodiagnostics and enzyme biosensors are two of the leading technologies that have had the greatest impact on the food industry. The use of these two systems has reduced the time for detection of pathogens such as Salmonella to 24 h and has provided detection of biological compounds such as cholesterol or chymotrypsin. The continued development of biosensor technology will soon make available "on-line quality control" of food production, which will not only reduce cost of food production but will also provide greater safety and increased food quality.

Biosensing Techniques↗

PubMed2002

Detection of Escherichia coli O157:H7 in 10- and 25-gram ground beef samples with an evanescent-wave biosensor with silica and polystyrene waveguides.

A portable evanescent-wave fiber-optic biosensor was used to detect Escherichia coli O157:H7 in seeded 10- and 25-g ground beef samples. The biosensor works by launching light from a 635-nm laser diode into specially designed optical fiber probes, generating an evanescent field that extends approximately 1,000 nm from the fiber surface. Fluorescent molecules within the evanescent field are excited, and a portion of their emission recouples into the fiber probe. The return path emission is transported by an optical fiber to a photodiode within the biosensor that detects and quantifies the fluorescent signal. A sandwich immunoassay was performed on the fiber probes with cyanine 5 dye-labeled polyclonal anti-E. coli O157:H7 antibodies for generation of the specific fluorescent signal. Biotin-streptavidin interactions were used to attach polyclonal anti-E. coli O157:H7 antibodies to the surface of the fiber probe. A centrifugation method was developed to obtain samples suitable for biosensor analysis from 10- and 25-g ground beef samples. The assay was shown to be sensitive and repeatable. One hundred percent correct identification of positive samples was demonstrated at 9.0 x 10(3) CFU/g for 25-g ground beef samples with silica waveguides and at 5.2 x 10(2) CFU/g for 10-g ground beef samples with polystyrene waveguides. The reaction was highly specific. No false positives were observed for 10-g ground beef samples not spiked with the pathogen. In addition, when samples were spiked with high concentrations of a variety of non-E. coli O157:H7 organisms, no false positives were observed. The method was rapid, with results being obtained within 25 min of sample processing.

Animals↗

PubMed1999

PNA biosensors for nucleic acid detection.

Biosensor devices, based on the conversion of nucleic acid recognition reactions into useful electrical signals, offer considerable promise for DNA diagnostics. The unique hybridization properties of solution-phase PNA can be extrapolated onto transducer surfaces in connection with the design of remarkably specific DNA biosensors. This article reviews the development of PNA biosensors, and discusses common PNA-biosensing protocols along with their prospects in DNA biosensor technology.

Biosensing Techniques↗

PubMedDate not supplied

[Detection of the hepatitis B virus surface antigen with a biosensor].

A new method for detection of hepatitis B surface antigen (HBsAg) has been developed. It employees IAsys optical biosensor registration kinetics of HBsAg complexes with monoclonal antibodies. Detection of intermolecular interactions is accompanied by changes of the light refraction coefficient in the sensitive layer of the biosensor cuvette. The main advantage of this diagnostic technique consists in rapid registration of these interactions in real time, without any introduction of special labels into analysing molecules. The optical biosensor method was successfully employed for the detection of HBsAg in human blood serum. A comparative study of HBsAg detection by the optical biosensor and by immunoenzyme analysis demonstrated high specificity of HBsAg detection by this new method.

Antibodies, Monoclonal↗

PubMed2002

On-line determination of nitrite in wastewater treatment by use of a biosensor.

A newly developed biosensor for nitrite having a 90% response time of about 1 min was used to monitor nitrite concentration in activated sludge exposed to oxic/anoxic cycles. The NO2- biosensor contains bacteria that reduce NO2-, but not NO3-, to N2O that is subsequently monitored by a built-in electrochemical sensor. Nitrite plus nitrate (NOx-) was simultaneously monitored by a NOx- biosensor. The maximum operational lifetime of the NO2- biosensor was 6 weeks, but much longer lifetimes can be expected as malfunctioning by the 3 sensors used for longer periods was due to either mechanical damage or ineffective internal sterilization during the construction. Insufficiently sterilized sensors became sensitive also to NO3- after some time due to development of NO3(-)-reducing bacterial populations within the sensor. The fraction of NO2- as compared to NO3- in the activated sludge was very dependent on prehistory, actual loading, and aeration. During balanced operation with NH4+ being exhausted during the later parts of the aerobic cycle, NO2- increased in concentration up to about 50 microM during the early part of the aeration cycle until NH4+ became limiting. At that time the NO2- concentration decreased to low levels. Under some operating conditions a peak of NO2- also appeared in the beginning of the anoxic period. NO2- and NO3- were depleted simultaneously during the anoxic period.

Biosensing Techniques↗

PubMedDate not supplied

[Study of the tissue and subcellular distribution of isatin-binding proteins with optical biosensor].

An original method for the integral evaluation of tissue and subcellular distribution of isatin binding proteins has been developed. This method is based on continuous monitoring of changes of optical characteristics that accompany complex formation between a ligand (immobilized on dextran bed of IAsys biosensor cell) and its soluble receptor. Solubilisation of tissue preparations and subcellular fractions with detergent (1% Triton X-100) is the important preconditions for the applicability of this method. The immobilisation of 5-aminoisatin was achieved by peptide bond formation between amino group of this isatin analogue and carboxyl group of the dextran bed of the biosensor cell. Addition of Triton X-100 treated preparations of membrane and soluble fractions of rat brain, liver, heart, and kidneys to the biosensor cell resulted in appearance of the characteristic response, indicating complex formation with the immobilised isatin analogue. The magnitude and a shape of kinetic curve vary in these samples. Isatin binding proteins predominated in membrane fractions of brain, liver and heart preparations whereas in the kidneys the highest isatin-binding response was detected in the soluble fraction. The distribution of isatin binding sites in the particulate fraction reduced in the following order: brainstem > brain hemispheres = cerebellum > heart > kidneys > liver. In the soluble fraction there was different rank of isatin binding activity: kidneys > heart > brainstem = brain hemispheres > liver > cerebellum. Liver outer mitochondrial membranes are characterised by the higher isatin-binding than mitochondria. Treatment of mitochondria with clorgyline and deprenyl, specifically inhibiting MAO A and B, respectively, significantly reduced the magnitude of the biosensor response and changed the shape of the kinetic curve. These data are consistent with the notion that within mitochondria MAOs are the major targets of isatin.

Animals↗

PubMedDate not supplied

Biosensor analysis of beta-lactams in milk: comparison with microbiological, immunological, and receptor-based screening methods.

Two recently developed surface plasmon resonance biosensor assays for detection of beta-lactams in milk were used to screen raw producer milk samples. Both assays use a beta-lactam receptor protein with carboxypeptidase activity for detection. The results of the biosensor assays were compared with those of various commercial screening tests, i.e., the Delvotest SP, Penzym S, Beta-STAR, SNAP, and Parallux. The results of the 2 biosensor assays showed good agreement with those of the other screening tests. Of 195 analyzed milk samples, the results of only 5 samples differed between the assays. Additionally, 30 milk samples with both negative and positive results in the screening assays were analyzed by liquid chromatography for identification and quantification of any beta-lactam residues. All screening tests showed 0% false-negative results with 15 incurred samples containing between 4.0 and 268 microg/kg penicillin G. The biosensor assays showed 27% positive results (false violatives) with 15 producer milk samples containing penicillin G concentrations between 0 and 3.6 microg/kg, i.e., below maximum residue limit. This figure varied between 27 and 53% for the other screening tests.

Animals↗

PubMed2004

[Superoxide dismutase biosensor for screening substances possessing scavenging superoxide anion activity].

AIM: To establish a method for screening active substance with scavenging effects on superoxide anion in vitro by designed superoxide dismutase biosensor. METHODS: The enzyme sensor was built by connecting the immobilized CuZnSOD with optical oxygen sensor through a special way. Superoxide anions were generated by auto-oxidation of pyrogallol. The auto-oxidation speed was examined before and after adding samples into the system, and the Vit C having the scavenging radical activities was served as a positive control. RESULTS: The limit of biosensor detection was 7.0 U in activity, and lifetime of the immobilized enzyme in the reaction-cell was above 2 weeks. The scavenging effects on superoxide radicals of fifteen active substance were studied in vitro by the sensor, and some of them presented scavenging activities. CONCLUSION: The signal from biosensor is stable, easy to be determined, and the kinetic information on scavenging superoxide radicals could be obtained directly. The biosensor system can be used for screening drugs simply and rapidly.

Ascorbic Acid↗

PubMed2004

Development of a genotoxicity detection system using a biosensor.

The umu-lux test is a genotoxicity test using the two genetically modified S. typhmurium TA1535 strains (TL210 and TL210ctl) transformed with the luxCDABE (luciferase gene and fatty acid reductase genes) of Vibrio fischeri as a reporter gene. The TL210 strain detects genotoxicants and the TL210ctl strain detects cytotoxicants. In order to develop a highly sensitive, simple and rapid genotoxicity detection system, we constructed a biosensor using these immobilized strains. The biosensor consists of two immobilized microbial membranes, a sample vessel and photodetectors, and the genotoxicity detection system consists of the biosensor, an isothermal box, a photodetector and an air pump. The total measurement time for genotoxicants using this detection system is about 4 h. When 2% (v/v) DMSO was used as a control, the TL210 strain was not emitting light while the TL210ctl strain was. When 0.3 mg/l 4NQO was used as a genotoxicant, TL210 strain and TL210ctl strain were both emitting light. When HgCl2 was used as a cytotoxicant, neither the TL210 strain nor the TL210ctl strain were emitting light. Therefore, the false negative prevention function of a biosensor using the TL210ctl strain has been checked. These results show that our proposed system can correctly detect genotoxicants.

4-Nitroquinoline-1-oxide↗

PubMed2005

Grid-enabled biosensor networks for pervasive healthcare.

Current advances in biosensor technology allow multiple miniaturized or textile sensors to record continuously biosignals, such as blood pressure or heart rate, and transmit the information of interest to clinical sites. New applications are emerging, based on such systems, towards pervasive healthcare. This paper describes an architecture enabling biosensors, forming a Body Area Network (BAN), to be integrated in a Grid infrastructure. The Grid services proposed, such as access to recorded data, are offered via the BAN console, an enhanced wearable computer, where the recordings of multiple biosensors are integrated. Medical Grid-enabled Nodes can have access to biosensor measurements upon demand, or can agree to get notifications and alerts. Thus, in such a distributed environment, data and computational resources are independent, yet cooperating unobtrusively, contributing to the notion of pervasive healthcare.

Blood Pressure Monitoring, Ambulatory↗

PubMed2005

A novel thermal biosensor based on enzyme reaction for pesticides measurement.

A novel thermal biosensor based on enzyme reaction for pesticides detection has been developed. This biosensor is a flow injection analysis system and consists of two channels with enzyme reaction column and identical reference column, which is set for eliminating the unspecific heat. The enzyme reaction takes place in the enzyme reaction column at a constant temperature (40 degrees C) realized by a thermoelectric thermostat. Thermosensor based on the thermoelectric module containing 127 serial BiTe-thermocouples is used to monitor the temperature difference between two effluents from enzyme reaction column and reference column. The ability of this biosensor to detect pesticides is demonstrated by the decreased degree of the hydrolytic heat in two types of thermosensor mode. The hydrolytic reaction is inhibited by 36% at 1 mg/L DDVP and 50% at 10 mg/L DDVP when cell-typed thermosensor is used. The percent inhibition is 30% at 1 mg/L DDVP and 42% at 10 mg/L DDVP in tube-typed thermosensor mode. The detection for real sample shows that this biosensor can be used for detection of organophosphate pesticides residue.

Animals↗

PubMedDate not supplied

[Amperometric biosensor for ethanol analysis in wines and grape must during wine fermentation].

The amperometric biosensor for ethanol determination based on alcohol oxidase immobilised by the method of electrochemical polymerization has been developed. The industrial screen-printed platinum electrodes were used as transducers for creation of amperometric alcohol biosensor. Optimal conditions for electrochemical deposition of an active membrane with alcohol oxidase has been determined. Biosensors are characterised by good reproducibility and operational stability with minimal detection limit of ethanol 8 x 10(-5) M. The good correlation of results for ethanol detection in wine and during wine fermentation by using the developed amperometric biosensor with the data obtained by the standard methods was shown (r = 0.995).

Biosensing Techniques↗