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PubMed2005

Electrochemical biosensors for DNA analysis.

Over the past few years, progress in electrochemical biosensors for DNA analysis is outstanding. This article briefly reviewed the principals of such biosensors, followed by a selection of topics that are of particular current interest. Selectivity and sensitivity are the two major challenges in DNA analysis. The former can be accomplished using peptide nucleic acids as probes, or relying on the DNA-mediated electron transfer. Special emphasis has been given to the efforts for high sensitivity, involving combination with polymerase chain reaction techniques, enzyme-labeled methods, direct label-free detection and nano-based techniques.

Biosensing Techniques↗

PubMed2005

Enzyme-based amperometric biosensors for continuous and on-line monitoring of cerebral extracellular microdialysate.

Analytical systems integrating in vivo microdialysis sampling with enzyme-based electrochemical biosensor detection have been increasingly accepted to be a new technique for continuous and on-line monitoring of biologically important species. Extensive interests in such integrated on-line analytical systems have suggested that these systems are very useful for physiological and pathological investigations. This review mainly focuses on the principle, development and striking applications of the enzyme-based amperometric biosensors integrated with in vivo microdialysis for continuous and on-line monitoring of cerebral extracellular fluid in recent years.

Acetylcholine↗

PubMed2005

Analytical aspects of fet-based biosensors.

Field-effect transistor (FET)-based biosensors (BioFETs) have undergone great progress especially in the last decade, since they were first realized in 1980. Recently, BioFETs have become one of the most important branches of biosensors. This paper briefly reviewed the operating principles of BioFETs and summarized the improvement and application of BioFETs, finally, the future prospects of BioFETs were discussed with 126 references.

Biosensing Techniques↗

PubMed2005

Reagentless electrochemical biosensor based on the multi-wall carbon nanotubes and nanogold particles composite film.

A novel method was used to prepare the nano-composite by assembling nanogold (NG) particles on the multiwall carbon nanotubes (MWNTs) surface. The nano-composite could be immobilized on a glassy carbon (GC) electrode to get a novel modified electrode. The electrode can easily immobilize the horseradish peroxidase (HRP) molecules to construct a reagentless biosensor. The NG particles in the composite film have a good biological compatibility. And due to the existence of quinone groups on the MWNTs surface, the MWNTs can promote the electron transfer between enzymes and electrode surface. The biosensor shows a good stability and responds to H2O2 in the range from 2.0 microM to 3.5 mM with a detection limit of 1.0 microM.

Biosensing Techniques↗

PubMed2006

A novel electrochemical biosensor for the detection of uric acid and adenine.

A novel electrochemical biosensor for the detection of uric acid and adenine was prepared based on a gel containing multi-walled carbon nanotubes and room-temperature ionic liquid of 1-octyl-3-methylimidazolium hexafluorophosphate. The electrochemistry of uric acid and adenine was studied in this gel modified electrode. There was a significant two-way electrocatalytic activity upon both oxidation and reduction of uric acid. Similar to a bare glassy carbon electrode, uric acid undergoes a 2e,2H+ oxidation in phosphate buffer in the modified electrode. A diimine, the oxidation product of uric acid, was found to be an unstable intermediate, which was converted by a follow-up hydration reaction to an imine alcohol, with the reaction rate constant of 8.5 +/- 0.3 M(-1).s(-1) according to Nicholson's theory. Under optimum conditions, linear calibration graphs were obtained over the concentration range of 1.0 x 10(-7) M approximately 1.0 x 10(-5) M (uric acid) and 1.0 x 10(-5) M approximately 6.0 x 10(-4) M (adenine). Based on the signal-to-noise ratio of 3, the detection limits of the current technique was found to be as low as 9.0 x 10(-8) M (uric acid) and 2.0 x 10(-6) M (adenine), respectively. This novel biosensor was successfully applied for the assay of uric acid in human urine. Because of its good stability and long-term durability, such a gel modified electrode can provide a simple and easy approach for sensitive detection of uric acid and adenine.

Adenine↗

PubMedDate not supplied

Biosensors: clinical requirements and scientific promise.

Biosensors are currently very fashionable, even though they are not new! - an enzyme electrode being described almost 20 years ago by Updike and Hicks in 1967. The aim of this review is to put into perspective why biosensors are needed in clinical medicine and to describe some of the research that is being performed to develop such devices for, in particular, 'in vivo' applications.

Biotechnology↗

PubMed1995

Principles and applications of biosensors for bioprocess monitoring and control.

Biosensors are useful analytical devices that can be integrated with on-line process monitoring schemes. In this article, the principles and applications of these devices for bioprocess monitoring are considered. Several different types of biosensors are described, and the applications and limitations of flow injection analysis (FIA) for these applications are discussed. It is hoped that the background provided here can be useful to researchers in this area.

Animals↗

PubMed1999

Rapid detection of Escherichia coli O157:H7 in ground beef using a fiber-optic biosensor.

A portable fiber-optic biosensor was used to detect Escherichia coli O157:H7 in seeded ground beef samples. The principle of the system is a sandwich immunoassay using cyanine 5 dye-labeled polyclonal anti-E. coli O157:H7 antibodies for generation of a specific fluorescent signal. Signal acquisition is effected by launching light from a 635-nm diode laser into a dual tapered 600-microm silica fiber. Fluorescent molecules within approximately 100 nm of the fiber surface are excited by the evanescent field, and a portion of the emission recouples into the fiber. A photodiode allows for quantitation of the collected emission light at wavelengths of 670 to 710 nm. Biotin-avidin interactions are used to attach polyclonal antibodies specific for E. coli O157:H7 to the final 7.5 cm of the fiber probe. The biosensor was able to detect E. coli O157:H7 to 3 to 30 CFU/ml in seeded ground beef samples. The reaction was highly specific. Signals with Listeria monocytogenes, Salmonella Typhimurium, or E. coli nonO157:H7 were 2 to 3% of those observed with a similar concentration of E. coli O157:H7. Assays were conducted at or near real-time with results obtained within 20 min of sampling.

Animals↗

PubMed2004

A rapid and automated fiber optic-based biosensor assay for the detection of Salmonella in spent irrigation water used in the sprouting of sprout seeds.

Recent outbreaks of foodborne illness have been linked to the consumption of contaminated sprouts. The spent irrigation water used to irrigate sprouts can carry many microorganisms, including pathogenic strains of Escherichia coli and Salmonella enterica. These pathogens are believed to originate from the seeds. The U.S. Food and Drug Administration recommends that sprout producers conduct microbiological testing of spent irrigation water from each production lot at least 48 h after seeds have germinated. Microbial analysis for the detection of Salmonella is labor-intensive and takes days to complete. A rapid and automated fiber-optic biosensor assay for the detection of Salmonella in sprout rinse water was developed in this study. Alfalfa seeds contaminated with various concentrations of Salmonella Typhimurium were sprouted. The spent irrigation water was assayed 67 h after alfalfa seed germination with the RAPTOR (Research International, Monroe, Wash.), an automated fiber optic-based detector. Salmonella Typhimurium could be positively identified in spent irrigation water when seeds were contaminated with 50 CFU/g. Viable Salmonella Typhimurium cells were also recovered from the waveguides after the assay. This biosensor assay system has the potential to be directly connected to water lines within the sprout-processing facility and to operate automatically, requiring manual labor only for preventative maintenance. Therefore, the presence of Salmonella Typhimurium in spent irrigation water could be continuously and rapidly detected 3 to 5 days before the completion of the sprouting process.

Biosensing Techniques↗

PubMed1995

Biosensors: where do we go from here?

In the 1980s, researchers predicted that biosensors would dominate hospital POC, POL, and home testing. While that hasn't quite come to pass, here's what biosensors have accomplished and a look at their future.

Biosensing Techniques↗

PubMed1995

Optical biosensors. A bright future.

Progress in fibre-optic technology, laser miniaturization, and the reproducible manufacture of prisms and wave guides has made the commercial exploitation of optical biosensors possible. Some optical biosensors are miniaturized versions of traditional spectrophotometers, others are based on new integrated-optic methods. This article reviews the achievements already made in this area and the opportunities for the future.

Biosensing Techniques↗

PubMedDate not supplied

[Effect of various methods of immobilization on stability of a microbial biosensor based on Pseudomonas rathonis T during detection of surfactants].

The operating and storage stability of a receptor element of an amperometric biosensor based on the Pseudomonas rathonis strain T capable of degrading surfactants was tested. Microbial cells were immobilized by incorporation in gels (agar, agarose, and calcium-alginate), polyvinyl alcohol membrane, adhesion to the chromatographic paper GF/A, or by the cross-linking induced by glutaric aldehyde. Incorporation of microbial cells in agar gel provides the long-standing conservation of their activity and viability during measurements of high concentrations of surfactants and allows the receptory element of the biosensor to be rapidly recovered after the measurements.

Biosensing Techniques↗

PubMedDate not supplied

[Effect of conditions of culturing Pseudomonas rathonis T on characteristics of a biosensor for determining anionic surface-active agents].

The dependence of the sensitivity of a microbial biosensor of anionic surfactants (AS) on the growth phase of Pseudomonas rathonis T, a strain capable of degrading surfactants, was studied. Correlations were found between the optimum values of temperature and pH of microbial growth, substrate utilization, and functional performance of the microbial biosensor. These results allow the process of AS detection to be optimized.

Anions↗

PubMed2001

Development of a novel plant system as biosensor for detecting environmental hazards and bioactive molecules through distinct responses.

Currently, chemicals are used excessively in medicine, industry, and agriculture throughout the world. Because of the current rise in environmental pollutants and hazardous exposures of human beings, there is an imperative need for monitoring the environment for biosafety. In addition, the importance of natural products with novel activity for drug or agrochemical scopes is being more and more realized. We report on a novel test system that can act as biosensors for detecting useful compounds while simultaneously monitoring or forecasting the biohazard exposure of organisms to chemicals as well as to physical factors in a given environment. Using different compounds and factors with known biological and cytotoxic activities, a detail plant test procedure has been developed that can be used in detecting and analyzing the value and/or danger of any given compound or treatment, including cell division inhibition, cytotoxicity, growth inhibition, and anticancer activities. The method provides a highly efficient single biosensor system that can replace several individual biotesting procedures. This plant assay procedure is a highly sensitive system for monitoring physical stress factors in the environment, including ionizing and nonionizing radiation. The procedure can be followed throughout the year because of the rapid growth rate of the plant used and its regeneration in ambient conditions. Therefore, the described system is highly useful to thoroughly monitor the environment and detection of new chemicals/compounds.

Biosensing Techniques↗

PubMed2001

Polymer modified electrodes for the reversible oxidation-reduction of NAD+/NADH for use within amperometric biosensors.

Electrochemical enzyme based biosensors continue to attract much attention due to the simplified analyses they promise, in comparison to many more complicated analytical procedures. The largest group of enzymes, are those that rely NAD(P)+/NAD(P)H as cofactors. One of the problems associated with the use NAD(P)+/NAD(P)H redox couples, however, within electrochemical biosensors is their ability to passivate noble metal electrodes. There have been many attempts to overcome this problem, such as the use of carbon paste electrodes [1], although approaches such as these are both cumbersome and typically irreproducible. In recent years conducting polymers such as poly(3-methylthiophene) [2] have also been used to modify noble metal electrode surfaces to lower the overpotentials required, while poly(phenol red) has been incorporated into films to offer selectivity against interferents [3,4]. In this study platinum electrodes have been electrochemically coated with mixed polymer films of poly(phenol red) together with poly(3-methylthiophene), poly(aniline) or poly(o-phenylenediamine) to offer enhanced performance. Cyclic voltammetry has been used to compare the electrochemical behaviour of the NAD+/NADH redox couple over repeated potential cycles, with the most favourable results being seen with the poly(aniline)/poly(phenol red) and poly(o-phenylenediamine)/poly(phenol red) coated electrodes.

Biosensing Techniques↗

PubMed2001

A novel toxicity fingerprinting method for pollutant identification with lux-marked biosensors.

A novel technique is described for the identification and quantification of environmental pollutants based on toxicity fingerprinting with a metabolic lux-marked bacterial biosensor. This method involved characterizing the toxicity-based responses of the biosensor to seven calibration pollutants as acute temporal-dose response fingerprints. An algorithm is described to allow comparisons of responses of an unknown pollutant to be made against the calibration data. This is based on predicting pollutant concentration at each of six different time points over the course of a 5-min assay. If the prediction is consistent between the unknown pollutant and a calibration pollutant at the 95% test level, this is considered to be a positive identification. All seven calibration pollutants could be successfully distinguished from each other with this technique. Environmental samples, individually spiked with single concentrations of pollutants, were compared in this way against the calibration pollutants. An 83% identification success was achieved, with no false positives at the 95% test level. This is a simple and rapid technique that potentially can be applied to monitoring of industrial wastewater or as a screening tool for regulators.

Algorithms↗

PubMed2002

The usefulness of a biosensor controlled perfusion cell culture for the investigation of new drugs demonstrated with the marine fungus Kirschsteiniothelia maritima.

The investigation of new biological active substances from limited sources for example from marine organisms needs sensitive and evident test systems. Such a system is the glucose biosensor controlled perfusion cell culture. The glucose consumption of cells is a very sensitive parameter which allows the continuous measurement of external effects of test substances on the cells under in vivo-like conditions. Cytotoxic concentrations of active substances as well as a virus infection lowers the glucose consumption of continuously perfused cells. This effect can be monitored using a glucose biosensor. The influence of drugs and the virus infection can be observed simultaneously in the same system continuously over several days. With two substances isolated from the marine fungus Kirschsteiniothelia maritima investigations for cytotoxic and for antiviral effects are demonstrated.

Anti-Bacterial Agents↗

PubMed2002

Integral toxicity test of sea waters by an algal biosensor.

An integral toxicity test, based on an algal biosensor and suitable to be used in sea water, is presented. The biosensor was designed and built by coupling a Clark oxygen electrode as transducer and the marine alga Spirulina subsalsa as biological mediator; it constitutes the "core" in a lab-scale prototype of a flow apparatus suitable to continuously monitor, in sea water, the photosynthetic activity of the alga and, from its variation, the marine pollution from the toxicological point of view. Inorganic pollutants (heavy metals) were tested in previous researches while organic ones (chlorophenols, pesticides and surfactants) are the object of the present paper.

Bacterial Proteins↗