Biorecognition elements

Novel glycerol and formaldehyde selective sensors based on pEI-Sensitive Field Effect Transistors as transducers and Glycerol Dehydrogenase and Formaldehyde Dehydrogenase as biorecognition elements have been developed. The main analytical parameters of the sensors have been investigated and will be discussed. 

L-lactate-cytochrome c-oxidoreductase (flavocytochrome was isolated for the first time from the thermo-tolerant yeast H. polymorpha. The mentioned above enzyme preparations were used for construction of the biorecognition elements of electrochemical sensors. 

Fig. 4 Schematic representation of a generic biosensor with the essential components (biorecognition element, transducer, and electronic part involved in data processing and display)...

Figure 2 Examples of coiled-coils used as engineering materials—transplantable oligomerization module (a) [24,25,27], epitope-displaying scaffold (b) [26], biorecognition element (c) [28], allosteric switch (d) [29], and self-replicating peptide (e) [30]. 

This biosensor consists of two surface-tethered components. The biorecognition element can be an antibody (Section 19-5), DNA, RNA, or carbohydrate with specific affinity for analyte. A structural analog of the analyte is bound to a flexible arm adjacent to the recognition element. In the absence of analyte, the tethered analog binds to the recognition element. 

When analyte is added, it displaces the tethered analog from this biorecognition element. The higher the concentration of analyte, the more displacement occurs. When the analog is displaced from the binding site, and 4P are no longer close enough for... 

The choline oxidase biosensor was constructed using disposable SPEs. The working electrode was modified with Prussian blue (PB) catalyst and with the biorecognition element (choline oxidase). 

The main advantages of immobilizing whole cells over the isolated enzymes are (i) cells are more resistant to changes in pH or temperature and (ii) a single cell can contain all the enzymes and cofactors needed for bioconversion of the analyte [82], Most of the whole cell-based optical biosensors used in toxicity or bioremediation studies [83,84] employ microorganisms [85— 87], animal [88], plant tissues [89,90] or cell receptors [91] as biorecognition elements. 

Electrochemical DNA biosensors are based on the use of nucleic acids or analogues as biorecognition element and electrochemical techniques for the transduction of the physical chemical signal. Two aspects are essential in the development of hybridization biosensors, sensitivity and selectivity. Traditional methods for detecting the hybridization event are too slow and require special preparation. Therefore, there is an enormous interest in developing new hybridization biosensors, and the electrochemical represent a very good alternative [108]. 

A different approach of site-specific polymerization and thus immobilization of a biorecognition element was shown by several research groups by utilizing electropolymerization [74-76]. In combination with microelectrodes in microchannel systems, a site directed simple immobilization of the biorecognition element could be achieved. Patterns can also be created by... 

As a flnal example, it should be pointed out that it is also possible to circumvent the need of immobilization of the biorecognition element in the microchannel system. Instead, it can be immobilized on superparamagnetic beads, silica beads, latex particles, etc. [79-81]. These beads are applied together with the sample into the microchannel system and can be collected on or near the transducer via magnetic or membrane separation. 

In spite of large research activity in the use of these biorecognition elements, it is still mostly a proof-of-principle or demonstration phase, and not close to extensive or commercial use outside of academia.120 The exception can be for instance biochemical oxygen demand (BOD) sensors employing omnivorous yeast,121 and produced commercially. 

Though a biological recognihon reaction is typically very selective, interferences may occur due to substances other than the analyte of interest. Such interferences can be converted by the biorecognition element or at the transducer surface and... 

Pohanka, M. (2009) MonodonaJ and polyclonaJ antibodies production-preparation of potent biorecognition element. Journal of Applied Biomedicine, 7 (3), 115-121. 

Fig. 1 Descriptive scheme of the experimental setups for dengue virus detection. (A) Photon counting unit. (Al) Hamamatsu HC135-01 PMT Sensor Module. (A2) PMT fixation ring. (A3) Manual shutter (71430, Oriel). (A4) Fiber holder that prevents the movement of the fiber inside the photon counting unit. (A5) Fiber optic. (A6) Connection wire of PMT to computer. (A7) Electricity cable. (B) The outside handle of manual shutter that enables light access to the PMT. (C) Immobilization unit. (Cl) Fiber optic. (C2) lOOpl pipette tip. (C3) Conical tube cup. (C4) Point of fixation of fiber. (C5) Optical fiber core. (C6) Biorecognition elements according to MAC-ELISA chemiluminescent OFIS (Alias et al. 2009). (C7) Test samples. (E) Connection to computer...

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