Biosensors detection system based

There is increasing interest in the use of specific sensor or biosensor detection systems with the FIA technique (Galensa, 1998). Tsafack et al. (2000) described an electrochemiluminescence-based fibre optic biosensor for choline with flow-injection analysis and Su et al. (1998) reported a flow-injection determination of sulphite in wines and fruit juices using a bulk acoustic wave impedance sensor coupled to a membrane separation technique. Prodromidis et al. (1997) also coupled a biosensor with an FIA system for analysis of citric acid in juices, fruits and sports beverages and Okawa et al. (1998) reported a procedure for the simultaneous determination of ascorbic acid and glucose in soft drinks with an electrochemical filter/biosensor FIA system. 

Zuzuarregui, A., Souto, D., Perez-Lorenzo, E., Arizti, R, Sanchez-Gomez, S., Martmez de Tejada, G., Brandenburg, K., Arana, S., Mujika, M., 2015. Novel integrated and portable endotoxin detection system based on an electrochemical biosensor. Analyst 140, 654—660. 

Fibre optic-based flow-through optical biosensors The dramatic advances in fibre optic development in die last decade have promoted construction of sensors where radiation, whether emitted, transmitted or reflected, is conducted fi-om the sample to the detection system. The wide variety of available optical waveguide types (solid rods, hollow cylinders, micro-planar geometries) has been used with varying success in sensor development. 

Our research group recently approached the problem of radical determination starting from the determination of oxygen free radicals, in particular superoxide radical, and assembling several new kinds of electrochemical sensors and biosensors suitable for this purpose [21-24]. Firstly, a voltammetric system based on the detection of reduced cytochrome c this system was also applied to develop a... 

Another sensor based on a fiber-optic-based spectroelectrochemical probe uses a DNA/ethidium bromide system to take advantage of the biological recognition processes [92]. The concept of immobilizing electrochemical reagents on the end of an optical fibre is a useful addition to the field of bioanalytical sensors. Before this development, optical and electrochemical detection of DNA were performed separately. Optical and electrochemical detection of DNA are suitable for a DNA detection system [93, 94] and these techniques will enable a production of a cheap DNA biosensor with a rapid and quantitative response. 

The detection system utilized in commercially available Biacore biosensors (Biacore, Sweden) is also based on SPR, an optical phenomenon that arises when... 

Several implanted biosensors have been developed and evaluated in both animals and humans (see Chapter 4). Detection systems are based on enzymes, electrodes, or fluorescence. The most widely studied method is an electrochemical sensor that uses glucose oxidase. This sensor can be implanted intravenously or subcutaneously. Intravenous implantation in dogs for up to 3 months has demonstrated the feasibility of this approach. Alternatives to enzymes are being developed, including artificial glucose receptors. Less success has been achieved with subcutaneous implants. Implantation of a needle type of sensor into the subcutaneous tissue induces a host of inflammatory responses that alters the sensitivity of the device. Microdialysis with hoUow fibers or ultrafiltration with biologically inert material can decrease this problem. 

The system was first applied for development of chemosensors for gaseous hydrogen chloride. Polyaniline, and its copolymers with different derivates of aniline were used. Then a similar approach was tested in the author s group for optimization of amperometric biosensors for glucose based on electrocatalytical detection of hydrogen peroxide. A pigment Prussian blue was used as an electrocatalyst for decomposition of this product of enzymatic oxidation of... 

Biosensors based on a Clark oxygen electrode, coupled to tyrosinase immobilized by three different methods, were investigated for the determination of phenol in real matrices, such as water of various natural sources, industrial wastes and oil press. The feasibility study included direct use of the biosensors and in situ analysis. An integrated system, incorporating SPE, desorption, fractionation and biosensor detection, was validated for screening phenolic compounds in water. Two types of electrode were tested, solid graphite and CPE incorporating tyrosinase. Correct analyses were found for river water samples spiked with phenol (10 p.gL ), p-cresol (25 p.gL ) and catechol (1 A mul-... 

Electrochemical biosensors have some advantages over other analytical transducing systems, such as the possibility to operate in turbid media, comparable instrumental sensitivity, and possibility of miniaturization. As a consequence of miniaturization, small sample volume can be required. Modern electroanalytical techniques (i.e., square wave voltammetry, chronopotentiometry, chronoamperometry, differential pulse voltammetry) have very low detection limit (1(T7-10 9 M). In-situ or on-line measurements are both allowed. Furthermore, the equipments required for electrochemical analysis are simple and cheap when compared with most other analytical techniques (2). Basically electrochemical biosensor can be based on amperometric and potentiometric transducers, even if some examples of conductimetric as well as impedimetric biosensor are reported in literature (3-5). 

Direct detection biosensors utilize direct measurement of the biological interaction. Such detectors typically measure physical changes (e.g., changes in optical, mechanical, or electrical properties) induced by the biological interaction, and they do not require labeling (i.e., label free) for detection. Direct biosensors can also be used in an indirect mode, typically to increase their sensitivity. Direct detection systems include optical-based systems (most common being surface plasmon resonance) and mechanical systems such as quartz crystal resonators. 

For enzyme-based biosensors the mode of detection is based on the catalytic activity and/or binding capacity. Because of the protein nature of almost all enzymes, the catalytic activity depends on the conformation. Exceptions are catalytic ribonucleic acids called DNA biosensors or genosensors. DNA fragments are used as probes for detecting low concentrations of DNA in large samples (see also Part I, Chapters 2 and 3). Because of the highly diluted DNA concentration, microelectromechanical systems which are able of performing PCRs are employed. 

PSII-based biosensors should evenmally serve as sensitive, low cost detection systems that are capable of detecting specific pollutants. The arising need to comply with EU and EPA directives and standards for environmental monitoring makes such a system increasingly attractive. 

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