Flow-through optical biosensors

Flow-through optical sensors bearing one or more immobilized enzymes at their sensing microzone can be classified according to the type of physical relationship between the microzone and the detection system or instrument used into those using fibre optics (photometric and luminemetric) and those integrating a biochemical reaction and detection (usually photometric). 

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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. 

Zhu L, Li YX, Zhu GY (2002) A novel flow through optical fiber biosensor for glucose based on luminol electrochemiluminescence. Sens Actuators, B 86(2-3) 209-214. doi 10.1016/s0925-4005(02)00173-9... 

Figure 5.5 — Flow-through biosensor for the determination of L-glutamate. (A) Flow injection manifold. (B) Sensing microzone of the probe sensor (optrode), incorporated in the flow-cell (FTC). P pump IV injection valve MC mixing chamber AD air damper BFB bifurcated fibre bimdle LS light source PMT photomultiplier R recorder GLU L-glutamate 0-Glu 2-oxoglutarate E enzyme layer I optical insulator S sensing layer PS polyester support. For details, see text. (Adapted from [6] with permission of Elsevier Science Publishers).

Nanduri, V., Kim, G., Morgan, M., Ess, D., Flahm, B. K., Kothapalli, A., Valadez, A., Geng, T., and Bhunia, A. K. (2006). Antibody immobilization on waveguides using a flow-through system shows improved Listeria monocytogenes detection in an automated fiber optic biosensor RAPTOR. Sensors 6, 808-822. 

A DNA optical sensor system was proposed by Cass and co-workers [35] based on the combination of sandwich solution hybridization, magnetic bead capture, flow injection and chemiluminescence for the rapid detection of DNA hybridization. Sandwich solution hybridization uses two sets of DNA probes, one labelled with biotin, the other with an enzyme marker and hybridization is performed in solution where the mobility is greater and the hybridization process is faster, rather than on a surface. The hybrids were bound to the streptavidin-coated magnetic beads through biotin-streptavidin binding reaction. A chemiluminescence fibre-optic biosensor for the detection of hybridization of horseradish peroxidase-labelled complementary DNA to covalent immobilized DNA probes was developed by Zhou and co-workers [36]. 

A large field for optical biosensor modules is their use in analytical flow systems, either with special optical cells within the instrument or with optical fibers for remote measurement. An optoelectronic biosensor , proposed by Lowe and Goldfinch [224], is a flow-through cell mounted in a compact device between a light source and a photodiode, containing enzyme-indicator membranes (eg, with penicillinase and bromocresol green). The linear response of this flow sensor is between O.S and 5 mM substrate. 

The immobilization can be performed with a modality different from that of the reactor filled with the immobilized enzyme. The spectrophotometric control of hemodialysis treatment is based on an optical flow-through biosensor based on Prussian Blue film with chemically linked urease forming a monomo-lecular layer of the enzyme. This pH-enzyme opt-rode-FIA system has been used for the selective determination of postdialyzate urea in real clinical samples. 

De Castro MDL, Fernandez Romero JM (1995) Development of an optical flow-through biosensor for the determination of sulphite in environmental samples. Anal Chim Acta... 

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