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PubMed2006

[Study on characteristic of biosensors associated with cholinesterase for detection of pesticide residues].

Current research activity in characteristic of biosensors associated with cholinesterase (ChE) for detection of organophosphate and carbamate pesticide residues is summarized. Some novel methods, which aimed to overcome the problems inherent to ChE inhibition analysis, namely selectivity, accuracy, irreversible inhibition and matrix effect, etc, are commented. More sensitive genetically engineered ChE variants and sophisticated parallel detection systems are also envisaged when it comes to turning biosensors based on ChE into marketable products, respectively.

Animals↗

PubMedDate not supplied

Surface plasmon resonance biosensors for detection of pathogenic microorganisms: strategies to secure food and environmental safety.

This review describes the exploitation of exclusively optical surface plasmon resonance (SPR) biosensors for the direct and indirect detection of pathogenic microorganisms in food chains and the environment. Direct detection is, in most cases, facilitated by the use of defined monoclonal or polyclonal antibodies raised against (a part of) the target pathogenic microorganisms. The antibodies were immobilized to a solid phase of the sensor to capture the microbe from the sample. Alternatively, antibodies were used in an inhibition-like assay involving incubation with the target organism prior to analysis of nonbound antibodies. The free immunoglobins were screened on a sensor surface coated with either purified antigens or with Fc or Fab binding antibodies. Discussed examples of these approaches are the determination of Escherichia coli O1 57:H7, Salmonella spp., and Listeria monocytogenes. Another direct detection strategy involved SPR analysis of polymerase chain reaction products of Shiga toxin-2 genes reporting the presence of E. coli O157:H7 in human stool. Metabolic products have been exploited as biomarkers for the presence of a microbial agent, such as enterotoxin B and a virulence factor for the occurrence of Staphylococcus aureus and Streptococcus suis, respectively. Indirect detection, on the other hand, is performed by analysis of a humoral immune response of the infected animal or human. By immobilization of specific antigenic structures, infections with Herpes simplex and human immunodeficiency viruses, Salmonella and Treponema pallidum bacteria, and Schistosoma spp. parasites were revealed using human, avian, and porcine sera and avian eggs. Bound antibodies were easily isotyped using an SPR biosensor to reveal the infection history of the individual. Discussed studies show the recent recognition of the suitability of this type of instrument for (rapid) detection of health-threatening microbes to food and environmental microbial safety.

Biosensing Techniques↗

PubMed2006

[Surface plasmon resonance biosensor technology and its application in biomedicine].

Surface plasmon resonance (SPR) biosensors have become an advanced method for measuring biological molecular interaction. This article is focused on the principle and advantages of SPR biosensor chip technology, and its new applications in biomedical research fields. Its application prospects are also discussed.

Clinical Laboratory Techniques↗

PubMed1991

Development of biosensors for immunoassays.

Biosensors represent a new generation of analytical instruments incorporating a biological sensing element in contact with a physical transducer and an output device. The biological element may be a whole organism, an organelle, an enzyme, an antibody, cell receptors or nucleic acids. The transducer converts the interaction between the biological component and the sample into a measurable signal which could be an electrical charge, an optical signal, a heat exchanger or some other quantifiable event. In recent years, electrochemical sensors based on continuous potentiometric or amperometric detection of enzyme reaction products have been favoured in the development of biosensors. This is because electrochemical transducers are cheap, rapid to use and portable.

Biosensing Techniques↗

PubMed1991

[Biosensors and clinical analysis].

The determination of organic compounds in blood is important in clinical analysis. Most analysis of organic compounds are based on spectrometric methods. However, these methods involve complicated procedures and require a long time for the reaction to occur. Bioelectrochemical sensors employing immobilized biocatalysts have definite advantages. For medical purposes, miniaturization of enzyme sensors is essential. Miniaturized and highly selective enzyme sensors have been developed by combining enzyme immobilization techniques with silicon technologies. Glucose measurement in blood is the most important and essential assay in the clinical field. For this purpose, we have developed various micro biosensors for glucose measurements. Generally, enzymatic determination of glucose is based on the following reaction (s); (formula; see text) According to the above equation, 4 different micro-glucose sensors were developed; 1) a sensor based on the measurement of produced hydrogen peroxide, 2) a sensor based on the measurement of consumed oxygen, 3) a sensor based on the measurement of enthalpy change during the enzymatic reaction, 4) a sensor based on the measurement of the amount of proton produced, and 5) a sensor based on the measurement of the light emission during enzymatic reaction. For these purposes, various kinds of transducers were used. A micro-hydrogen peroxide electrode, a micro-oxygen electrode, a thermistor, an ISFET (ion selective field effect transistor), and a photon counter. The determination of antibodies, or antigens is also very important in clinical analysis. Several types of immuno-sensors have been developed for these purposes. Considering the integration of immuno-sensors, the miniaturization of immuno-sensors is also required. This review deals with our current study on micro-biosensors for clinical analysis.

Biosensing Techniques↗

PubMedDate not supplied

[Biosensors and their applications (review of the literature)].

Different biosensors (potentiometric, voltampermetric, thermometric, optoelectronic, acoustoelectronic) are reviewed, and the main principles of their operation are discussed. Data on biosensor applications are systematized.

Biosensing Techniques↗

PubMed1987

Review of medical biosensors and associated materials problems.

Developers of biosensors as medical devices are using emerging technologies that incorporate chemical assays with fiber optics and semiconductors. These biosensors will eventually become indwelling catheters for monitoring blood analyte concentrations as well as functioning as controlled feedback elements for artificial organs. Materials used in these devices are subject to problems of manufacture and reliability as well as those induced by the human body's response to these "foreign agents." The Division of Mechanics and Materials Science in the Center for Devices and Radiological Health at the Food and Drug Administration has initiated a program to investigate factors that effect sensitivity, selectivity and reliability of sensors used in biological applications. Our group's principle focus is on sensors of chemical processes. This article is an outgrowth of our research efforts and is a review of some of the technologies that are currently available or becoming available for these applications. The goal of our research is to identify factors that will have an impact on the reliability of long-term implanted medical devices with particular attention to sensors used in feedback-controlled therapeutic systems.

Artificial Organs↗

PubMedDate not supplied

Fiberoptic biosensors in artificial organs.

A large variety of assay methods based on optical principles can be miniaturized and adapted for use as in vivo monitors with the currently available optical fiber technology. Especially exciting is the capability of adapting the selectivity of immunoassays to continuous on-line biosensors by the use of hollow dialysis fibers. Thus, one can envision biosensors that could have many different applications in artificial organ development, from passive systemic monitoring to active feedback control devices for drug delivery.

Artificial Organs↗

PubMedDate not supplied

[Tissue and cell biosensors (possibilities of clinical use)].

The paper provides a review of the data available in the literature on biosensors based on plant and animal tissues. It presents the enzymes contained in the tissues, by describing the respective biochemical reactions underlying these sensors operation. It also gives basic characteristics of the biosensors in question.

Animals↗

PubMedDate not supplied

[Amperometric enzyme biosensor with a glucose oxidase-polyaniline membrane].

An amperometric glucose biosensor was made by electrochemical polymerization of aniline onto the gold electrodes in presence of the enzyme glucose oxidase in the phosphate buffer solution with pH 7.0. Aniline is easily polymerized forming a thin film, which adheres tightly on the electrodes surface. During the electropolymerization process glucose oxidase was entrapped into polyaniline film which then became the catalyst of the enzyme reaction of glucose hydrolysis. Experiments were performed to determine optimal conditions of polyaniline-glucose oxidase film preparation. Glucose was amperometrically determined with the electrochemically fabricated biosensor in the concentration range 10(-4) M to 2 x 10(-2) M. The linearity of the enzyme electrode response ranged from 2 x 10(-4) M to 6 x 10(-3) M. The electrochemical synthesis of a polyaniline-enzyme thin film a high-technologic one and this permits fabricating various microbiosensors and multisensors in the continuous technological cycle.

Aniline Compounds↗

PubMedDate not supplied

Glucose biosensors with enzyme entrapped in polymer coating.

The pursuit of reliable biosensors for measuring glucose levels has been ongoing for decades. Their importance lies partly in the development of the implantable artificial pancrease, which can be used to deliver insulin to diabetics without the need to test glucose levels externally, with automatic delivery based on physiologic demand. Glucose sensors can also be used in short-term monitoring of glucose levels in hospitals and clinical laboratories. Three types of glucose biosensors were studied. All were based on a two-electrode system: an insulated platinum wire as a hydrogen peroxide electrode, and a silver wire twisted around the platinum wire as both a reference and a counter electrode. Each was coated with the enzyme glucose oxidase entrapped in a polymer matrix of cellulose acetate (CA) or poly 2-hydroxyethyl methacrylate (HEMA), then dip-coated by an additional polymer coating of polyvinylchloride (PVC), polyurethane (PU), or HEMA. The experiments were designed mainly to study the effectiveness of polymer coatings as diffusion-limiting membranes. The effect of each coating on the linear response to glucose concentration was examined. It was shown that additional (multiple) coatings can increase the linearity of the sensor response. The best results were obtained when the sensor was PVC-dip-coated three times. This preparation had a linear response up to 600 mg/DL glucose concentration. The sensors coated with PU and HEMA have linearity up to 280 and 240 mg/DL glucose concentrations, respectively. It was also shown that the coatings reduce interference from certain body chemicals.

Biocompatible Materials↗

PubMed1994

[Long-functioning beta-D-glucose and L-lactate biosensors for continuous flow-through measurements for "fouling"-resistant and selectivity-optimized serum- and hemoanalysis].

Bioelectrochemical membrane-electrodes for O2-sensitive enzymatic flow-through analysis of beta-D-glucose and L-lactate are described. The enzyme-membranes of the biosensors consist of glucose-oxidase or lactate-oxidase molecules cross-linked with glutardialdehyde between two dialysis membranes. The accuracy of the biosensors is demonstrated by electroanalysis of diluted control serum and compared with redox-mediator-free H2O2 detection and photometric methods. Continuous haemoanalysis of uncoagulated blood was carried out, using an intermediate carrier stream with additive systems. Tangential streaming to the miniaturized dialysis chamber with a circular channel minimizes blockage of the pores of the dialysis membrane by erythrocytes, leukocytes or protein. An oxygenator pump for the exchange of gases between the buffered solution of the intermediate carrier and the surrounding atmosphere guarantees a constant oxygen partial pressure within the carrier stream. The pulsations produced by the oxygenator pump are dampened by a miniature pressure balance chamber with an unsignificant dead space volume for protecting the enzyme membrane of the sensor. Glutardialdehyde inhibits growth of microorganisms and any resulting oxygen consumption, so that even in protein-containing measuring solutions enzyme electrodes can be used without interference from microbial contamination. The bioelectrochemical measuring system can therefore also be employed for the electroanalysis of fermentation solutions. For continuous flow-through measurements, it is necessary to change the glucose-oxidase membranes after 100-150 days, and the lactate-oxidase membranes after 3-6 weeks.

Biosensing Techniques↗

PubMed1994

[Biosensors in the clinical chemistry laboratory and in clinical medicine].

Biosensors are up to date analytical instruments that make use of high sensitivity and specificity of biological receptors with physical or physico-chemical method of detection. The paper deals with following sensors: thermal, mass, surface plasmon resonators, optical sensors and biosensors, CHEMFETs, ISFETs, electrochemical sensors. Their principles and examples of use in investigation for biological and medical purposes are mentioned.

Biosensing Techniques↗

PubMed1993

Introducing a biosensor based technology for real-time biospecific interaction analysis.

This report describes a system for real-time biospecific interaction analysis, using biosensor technology based on the optical phenomenon surface plasmon resonance. The biospecific interface is a sensor chip consisting of a thin gold film deposited on a glass support and covered with a hydrogel matrix. One component of the interaction being studied is attached covalently to the hydrogel, and other interactants are passed over the chip in solution. The interaction is followed in real time in terms of changes in the mass concentration of biomolecules at the sensor surface. Surface concentrations down to 10 pg/mm2 can be measured. The technique does not require molecular labels such as isotopes or spectroscopic markers, and purification of interacting components can often be avoided. Repeated analyses can be performed on the same sensor chip. With this system, the same general procedure can be used for a wide range of different applications, including concentration determination, kinetic measurements and multi-site binding studies. The sensitivity of the technique can be adjusted by choice of reagents and experimental procedure: determination of specific proteins in serum down to 20 ng/ml and macromolecular association constants from 10(7) M-1 up to 4 x 10(11) M-1 are documentated examples. No other single analytical system has the same versatility and general applicability to biospecific interaction analysis. The system is developed and marketed by Pharmacia Biosensor AB, Sweden.

Biosensing Techniques↗

PubMed1995

Study of cellulose acetate membrane-based glucose biosensors.

A new immobilization procedure was designed to covalently immobilize enzymes onto a cellulose acetate membrane that was simple and easy to handle. The resultant enzyme membrane was very stable, with high specific activity. A glucose oxidase membrane was prepared by using this method, which was combined either with an oxygen electrode or with a hydrogen peroxide electrode to construct a glucose biosensor. The response characteristics of both biosensors were compared.

Biosensing Techniques↗

PubMedDate not supplied

A glucose biosensor based on an oxygen electrode: in-vitro performances in model buffer solution and in blood plasma.

An implantable biosensor for continuous monitoring of glucose levels in diabetic patients was developed. The biosensor is based on an amperometric oxygen electrode and glucose oxidase immobilized on carbon powder held in the form of a liquid suspension. The enzyme material can be replaced (the sensor recharged) without sensor disassembly. Sensors with polycarbonate glucose-diffusion membranes coated with silastic were studied. Calibration curves of the sensors in phosphate buffer solution and in undiluted blood plasma at body temperature were obtained and compared. Sensors were tested for long-term performance in vitro in model phosphate buffer solution and in blood plasma at room and at body temperature. Reproducibility of the sensor responses in plasma at body temperature was demonstrated. During continuous operation at body temperature, the sensors have a lifetime of at least six weeks.

Biomedical Engineering↗

PubMedDate not supplied

[Miniature thin layer biosensors which are sensitive to glutamate and glutamine].

Integrated thin film biosensors for simultaneous measurement of L-glutamine and L-glutamate in a micro-flow cell were developed. Due to a novel glutaminase with an activity optimum in the neutral pH range a direct monitoring of glutamine in mammalian cell culture medium could be performed. The glutamine bienzyme sensor was prepared by coimmobilization of glutaminase with glutamate oxidase within a photo patterned poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel membrane. The sensor response is linear in the concentration range of 55 mmol to 10 mmol glutamine/l. Additionally a glutamate biosensor is integrated on the sensor chip for difference measurement of possible glutamate interferences. The sensor chip can be used for at least 300 measurements without any alteration in the performance of its sensors. A new sensor chip with an integrated flow cell provides the possibility of simultaneous measurement of four different parameters at a cell volumina of 1 ml. Completing the microsystem a battery operated surface mounted device (SMD) potentiostat was developed to get a "lab on chip".

Biosensing Techniques↗

PubMed1998

Rapid detection of D-dimer using a fiber optic biosensor.

We describe a rapid and sensitive method for detection and quantification of D-dimer and other crosslinked fibrin degradation products (XL-FDPs), which are present in elevated concentrations in patients with sepsis and thrombotic disorders. The method utilizes a sandwich fluoroimmunoassay immobilized in the sensing region of an evanescent wave biosensor. Physiological concentrations of D-dimer and high molecular weight XL-FDP could be determined in buffer and plasma samples on calibrated fibers in 11 min. Samples from septic patients were assayed using ELISA and the fiber optic method; concentrations determined by fiber optic assay were strongly correlated with those determined by ELISA (r = 0.918); intra- and inter-assay errors were comparable to those from ELISAs. Given its accuracy and rapid response time, this fiber optic biosensor shows great potential for development as a diagnostic tool.

Biosensing Techniques↗