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PubMed1985

Biosensors: recent trends.

One of the major bottlenecks in automation and process control of industrial bioprocesses is the lack of suitable sensing devices to accurately measure the concentrations of biomolecules. The measurement of ions (e.g., H(+), NH(4)(+)) and gases (e.g., O(2), CO(2), NH(3)) using standard ion-selective and gas sensing electrodes respectively, is well established. Chemical analysis of biomolecules off-line is generally unreliable, labour intensive and may lead to contamination of the biological systems. Problems of maintaining sterile conditions are especially important when dealing with slow growing mammalian or plant cells in culture. Active research in the development of biosensors for monitoring fermentation processes, food production and pollution control, and for medical and veterinary applications is currently underway. This paper reviews recent approaches toward the development of biosensors which involve a biochemical interaction to measure the concentrations of biomolecules, primarily for the on-line monitoring and control of fermentation processes.

Journal Article↗

PubMed1995

Biosensors for environmental monitoring.

Increasing environmental legislation which controls the release and the levels of certain chemicals in the environment has created a need for reliable monitoring of these substances in air, soil and especially water. Conventional analytical techniques, although highly precise, suffer from the disadvantages of high cost, the need for trained personnel and the fact that they are mostly laboratory bound. Biosensors because of their specificity, fast response times, low cost, portability, ease of use and a continuous real time signal, can present distinct advantages in certain cases. Their biological base makes them ideal for toxicological measurements which are suited for health and safety applications. Over the last 3-4 years there has been an increase in the number of publications concerning biosensors for environmental monitoring, especially in the field of pesticide measurements. This paper reviews some of the more important developments over the past 3-4 years.

Journal Article↗

PubMed1994

A first look at biosensors.

This is a very elementary guide to biosensors, outlining the principles of operation of some optoelectronic and current measuring biosensors. Factors which can influence successful translation to the marketplace are addressed.

Journal Article↗

PubMed1995

Application of a novel fiber-optic biosensor in situ to investigate the metabolic effect of lactate infusion.

Recently developed biosensor technology, which allows near real-time measurement in situ of gas tension (pCO2 and pO2) and of pH, was applied to arterial blood, cerebrospinal fluid (CSF), and brain parenchyma during intravenous lactate infusion in monkeys. Comparison of simultaneous biosensor measurements and discrete arterial blood sampling for traditional blood gas analyses indicated a high level of correlation for pCO2, pO2, and pH. Arterial pO2 and pH values were significantly higher and pCO2 significantly lower than corresponding CSF and brain parenchyma values at baseline, during and following lactate infusion. There was a divergence between arterial and brain parenchyma pH and pO2 measurements. Lactate infusion was associated with progressive arterial pH rises, consistent with the production of a metabolic alkalosis. Cerebrospinal fluid pCO2 remained unchanged during and following lactate infusion. Brain parenchyma exhibited a complex pattern of response characterized by a trend for pO2 and pH to decrease during lactate infusion, which reversed following completion of the infusion. These observations are suggestive of a transient hypoxia from decreased cerebral blood flow and/or reduced oxyhemoglobin dissociation during lactate infusion, but verification of these results is required.

Animals↗

PubMed1990

A fast responding fibre optic glucose biosensor based on an oxygen optrode.

A fast responding glucose biosensor for the continuous determination of glucose is presented. The biosensor is based on an oxygen optrode, which measures the consumption of oxygen via dynamic quenching of the fluorescence of an indicator by molecular oxygen. Glucose oxidase (GOD) is immobilised onto the surface of this oxygen optrode by adsorption to carbon black and by crosslinking with glutardialdehyde. Carbon black is used as an optical isolation to protect the optrode from the interference of ambient light and sample fluorescence. The measurements were performed in a flow through cell with air saturated glucose standard solutions (phosphate buffered saline pH 6.9). The effect of four different qualities of GOD in relation to response times (the time required to reach 90% of the steady-state signal, tau 90, was 8-60 s, the linear analytical range (0.01 to 2 mM glucose) and the long-term stability (tau 1/2 was 1-20 weeks) were investigated. A simple device is presented capable of enlarging the analytical range up to 200 mM glucose concentration.

Biosensing Techniques↗

PubMed1990

Piezoelectric crystal biosensors.

The recent development of piezoelectric devices as biosensors is reviewed. Biological materials, like enzymes, lipids, antibodies and antigens, have been used as specific coatings and were utilized for the determination of different substrates. Methods of protein coating and several applications are reported including microgravimetric immunoassays, microbial assays, DNA hybridization, enzyme detections and gas phase biosensors. Although the piezoelectric immunochemical sensor is convenient to use and very promising, a thorough understanding of the different phenomena associated with crystals frequency measurement in biological reactions is still lacking and deserves further investigation.

Antibodies↗

PubMed1991

The potential role of biosensors in the food and drink industries.

Despite their apparent potential as analytical tools in the food and drink industries, only a few biosensors are used routinely. This article describes the development of biosensors for these sectors and discusses the technical and economic problems of applying this technology to the monitoring of food and drink products.

Beverages↗

PubMed1991

An FIA biosensor system for the determination of phosphate.

A flow injection analysis (FIA) biosensor system for the determination of phosphate was constructed using immobilized nucleoside phosphorylase and xanthine oxidase and an amperometric electrode (platinum vs silver/silver chloride, polarized at 0.7 V). When a phosphate-containing sample was injected into the detection cell, phosphate reacted with inosine in the carrier buffer to produce hypoxanthine and ribose-1-phosphate in the presence of nucleoside phosphorylase. Hypoxanthine was then oxidized by xanthine oxidase to uric acid and hydrogen peroxide, which were both detected by the amperometric electrode. The response of the FIA biosensor system was linear up to 100 microM phosphate, with a minimum detectable concentration of 1.25 microM phosphate. Each assay could be performed in 5-6 min and the system could be used for about 160 repeated analyses. This system was applicable for the determination of phosphate in various food products and plasma, and the results obtained agreed well with those of the enzymatic assay.

Biosensing Techniques↗

PubMed1991

Internal supply of coenzyme to an amperometric glucose biosensor based on a chemically modified electrode.

A biosensor for glucose using glucose dehydrogenase immobilized on a chemically modified graphite electrode was supplied with coenzyme, nicotinamide adenine dinucleotide (NAD+), through pores in the material. A graphite rod was hollowed out, leaving 0.3 mm at the end contacting the solution, filled with 10 mM NAD+ and pressurized. The response factor was 40% of that obtained when 2 mM NAD+ was mixed with the sample solution in a flow system. The coenzyme consumption was 11 microliters h-1 representing a 500-fold saving compared to supply through the bulk solution. The biosensor had a linear calibration curve from the detection limit, 1 microM, to 2 mM glucose and a repeatability of 0.3%. The graphite electrode was modified by adsorption of a bis-(benzophenoxazinyl)-terephthaloyl derivative in order to be able to oxidize NADH at 0 mV versus Ag/AgCl, 0.1 M KCl.

Biosensing Techniques↗

PubMed1992

A chemiluminescence fiber-optic biosensor system for the determination of glutamine in mammalian cell cultures.

A chemiluminescence fiber-optic biosensor system has been developed for determining glutamine in hybridoma cell cultures producing monoclonal antibodies against viral surface antigens. Glutaminase and glutamate oxidase (GLO) were immobilized onto aminopropyl glass beads via glutaraldehyde activation separately and packed in a column. Two separate columns containing immobilized GLO and catalase were placed upstream to eliminate endogenous glutamate. In the presence of ferricyanide, luminol reacted with hydrogen peroxide released from the enzymatic reactions to produce a chemiluminescence (CL) light signal which was detected and quantitated with a fiber-optic system. In combination with flow injection analysis it was possible to process samples virtually identically, thus avoiding difficulties in reproducing the CL signal. There was an excellent linear relationship between the CL response and standard glutamine concentration in the range 10(-6) to 10(-3) M. A complete analysis could be performed in 2 min including sampling and washing. Each immobilized enzyme column was stable for at least 300 repeated analyses without any loss of activity. When the biosensor system was used for the determination of glutamine in spent mammalian cell cultures, the values obtained compared well with those of high-performance liquid chromatography, thus validating the applicability of the CL fiber-optic system.

Animals↗

PubMed1992

Biosensors for environmental monitoring.

In this article we will outline several biosensor applications which may fill existing technology gaps in the area of environmental monitoring. The requirements for these environmental biosensors, as well as difficulties in commercialization, are also addressed.

Biosensing Techniques↗

PubMed1992

A single mode fibre-optic evanescent wave biosensor.

This paper reports experimental developments in the construction and operation of a single-mode fibre-optic evanescent wave biosensor using an exposed core silica single-mode fibre embedded in a silica block. The device was able to monitor the concentration of a blue dye, Procion Blue MX-G, in overlayers of various refractive indices. The practicality of such a biosensor has been demonstrated with a colorimetric enzyme assay system. Penicillin G in the 0-0.4 mM concentration range was monitored at 633 nm by the decoloration of the starch-iodine reagent when Bacillus cereus penicillinase was immobilized over the exposed core of the monomode fibre.

Biosensing Techniques↗

PubMed1993

An integrated silicon thermophile as biosensor for the thermal monitoring of glucose, urea and penicillin.

A new kind of calorimetric biosensor for the measurement of the heat (molar enthalpy change) of enzymatic reactions is presented. The device operates according to the Seebeck effect, the same principle on which thermocouples are based. The thermopile used in this work consists of an array of p-type silicon/aluminium strips integrated on a thin silicon membrane (5 microns). Its sensitivity is about 1 V output voltage per watt of heating power, corresponding to a temperature resolution in the order of 10(-5) K and a heating power resolution of some tenths of a mu W in the flow system used. Furthermore, this performance is obtained without any control of external temperature because of the high common-mode thermal noise rejection ratio of the thermopile. The universal technique of calorimetry combined with the specificity of biochemical reactions makes this biosensor very versatile, with a broad range of possible applications. Glucose oxidase together with catalase for the determination of glucose, urease and penicillinase for the monitoring of urea and penicillin G, respectively, were immobilized directly onto the back side of the thermopile. The sensor was operated in conjunction with flow injection analysis which, in addition to its traditional advantages, allows preconditioning of the samples. Thus, artefacts due to mixing effects were suppressed and interference caused by differences in ionic strength between sample and carrier was strongly decreased. Detection limits between 1 and 2 mM were reported in the flow injection conditions described.

Biosensing Techniques↗

PubMed1994

Tyrosinase-based ruthenium dispersed carbon paste biosensor for phenols.

Highly sensitive biosensors for phenolic compounds, based on the incorporation of the enzyme tyrosinase within metal-dispersed carbon paste matrices are described. In particular, ruthenium-doped carbon pastes display excellent electrocatalytic activity for the reduction of the enzymatically generated quinone species. Hence, convenient quantitation of micromolar concentrations is feasible at 0.0 V (vs. Ag/AgCl reference), with a greatly enhanced response compared to conventional carbon-paste tyrosinase biosensors. The influence of various experimental variables is explored. Fast, sensitive and reproducible flow injection detection of phenolic compounds is illustrated. Analogous improvements are reported for tyrosinase-rich plant tissue electrodes.

Biosensing Techniques↗

PubMed1994

Application of a flow injection fibre optic biosensor for the analysis of different amino acids.

The analysis of different amino acids is described using a fibre optic biosensor previously described in its principles. This biosensor works according to the measurement principle of flow injection analysis (FIA) and consists of a fluorosensor and a measurement cell operating under pressure. In the measurement cell, enzymes and molecular weight enlarged coenzyme PEG (MW 20000)-N6-(2-aminoethyl)-NAD(H) are confined behind a solid ultrafiltration membrane. Assays for the analysis of L-phenylalanine and L-alanine were developed. The analysis frequency is in the range of 1 to 2 samples per hour, and the sensor stability was found to be sensitive to the stability of each enzyme system used. This effect was studied in detail. The L-alanine assay was found to be especially reliable, sensitive, specific, and highly selective for the L-enantiomer.

Alanine↗

PubMed1994

Application of biotin-streptavidin technology in developing a xanthine biosensor based on a self-assembled phospholipid membrane.

We have designed an amperometric xanthine minibiosensor based on a supported biotinylated phospholipid membrane. To this membrane streptavidin-modified xanthine oxidase was coupled. The fabricated biosensor corresponds in shape and size to a needle of 0.3 mm in diameter. The assay is based on the electrochemical detection of enzymatically generated hydrogen peroxide. The response to xanthine was linear up to 1 mmol.l-1 with a detection limit of 0.02 mmol.l-1. The response time was less than one minute and the biosensor was stable for at least five days.

Bacterial Proteins↗

PubMed1994

Characterization of biomembranes by spectral ellipsometry, surface plasmon resonance and interferometry with regard to biosensor application.

Phospholipid bilayers with transport proteins and antigen/antibody interfaces are considered to be suitable biosensor systems. The quality of such membranes or interfaces depends on the properties of the layers. Optical methods have proved to be an appropriate tool for characterizing those layers in situ and in a non-destructive manner. Two systems with potential for biosensor applications are characterized by some of these methods: phospholipid bilayer membranes spread from vesicle solution and protein-antigens both adsorbed on planar solid support. The results of spectral ellipsometry, surface plasmon resonance (SPR) and spectral interferometry are compared with respect to quality of characterization, expenditure of sample preparation and measurement, and time resolution. The phospholipid membranes adsorbed show a relatively low refractive index and a relatively high thickness. Bruggeman effective medium approximation is used to calculate the effective layer thickness. This result is compared to SPR measurements. A correlation between thickness and vesicle concentration may be detected. Further, the test protocol of an immunoassay is examined by spectral interferometry and SPR. Thicknesses determined are compared to results obtained by applying spectral ellipsometry. The data measured by ellipsometry are in agreement with the molecular dimensions of the immunoglobulins. Differences between details can be explained by physical considerations.

Biosensing Techniques↗

PubMed1994

An in situ electrosynthesized amperometric biosensor based on lactate oxidase immobilized in a poly-o-phenylenediamine film: determination of lactate in serum by flow injection analysis.

The electrochemical immobilization of lactate oxidase in a poly-o-phenylenediamine film permits the one-step and all-chemical construction of a lactate amperometric biosensor. The sensor was prepared in situ i.e. in the flow injection analysis (FIA) system by simply injecting a plug of a solution containing the monomer and the enzyme. At a flow rate of 50 microL/min linearity was observed up to 0.2 mM lactate and detection limits of about 2 microM could be easily achieved. Faradaic interferences caused by ascorbate, urate, cysteine and acetaminophen were sufficiently minimized to permit lactate determination in diluted serum by FIA. Results obtained by FIA-amperometric detection compared well (according to a proper t-test at a 95% confidence level) with those obtained by a standard enzymatic colorimetric assay. At a flow rate of 1 ml/min a sample throughput higher than 70 sample h-1 was achieved. After one week of continuous use in the FIA system a 75% decrease in biosensor sensitivity was observed.

Animals↗