Construction, catalytic sensors

In addition to these catalytic sensors, optical fibers also provide the prerequisites for the construction of affinity sensors. In the classical example, a glucose sensor [220], the lectin con-canavalin A, is covalently attached to the internal wall of a membrane stitched on the tip of the fiber, and it binds by affinity the fluorescein-labelled macromolecule dextran. The in-... 

Particularly attractive for numerous bioanalytical applications are colloidal metal (e.g., gold) and semiconductor quantum dot nanoparticles. The conductivity and catalytic properties of such systems have been employed for developing electrochemical gas sensors, electrochemical sensors based on molecular- or polymer-functionalized nanoparticle sensing interfaces, and for the construction of different biosensors including enzyme-based electrodes, immunosensors, and DNA sensors. Advances in the application of molecular and biomolecular functionalized metal, semiconductor, and magnetic particles for electroanalytical and bio-electroanalytical applications have been reviewed by Katz et al. [142]. 

The organic conductor properties of tetrathiaflulvalenetetracyanoquino-dimethane (TTF-TCNQ) as a material for constructing electrodes, viz. its catalytic response and resistance to passivation, are of special interest for the determination of biological compounds, which usually have slow electrode kinetics and a low sensitivity, and tend to foul electrode surfaces. The response of a TTF-TCNQ microarray sensor inserted in a flow system for... 

Sensing mechanism of the modified sensor. The sensing mechanism in this modified sensor should be essentially the same as that of the unmodified one. It is noteworthy that a stationary short circuit current was obtained in spite of such sensor construction that the counter electrode was covered with Epoxy resin. Since the sensing electrode is placed in the same situation as the unmodified sensor, this fact indicates that the cathodic reaction is allowed to take place stationarily at the counter electrode. The proton conductor membrane is as thin as 0.2 mm, so that the reactant 02 and the produced H20 will permeate the membrane as shown in Figure 11. A part of H2 will naturally also permeate through the membrane, but the transfered H2 will be consumed by the reaction with 02 electro-chemically or catalytically at the counter electrode. 

Katakis and Heller [21] also applied the redox hydrogel to construct L-lactate and L-a-glycerophosphate sensors, where they observed electro-catalytic oxidation of both lactate and glycerol-3-phosphate at electrodes coated with three-dimensional redox polymer epoxy cross-linked networks which incorporated the respective oxidases. 

New methods have been developed for the construction of artificial enzymes. A general method for obtaining new substrate-specific catalytic proteins is to develop antibodies towards transition states of the reaction in question by using molecules as antigens which simulate the transition state [33]. Although these catalytic antibodies would have the disadvantages implied for protein molecules, the host molecules mentioned before [41] and specifically functionalized host molecules [45] would imply the properties of a catalyst and hence be potentially suitable for chemical transduction in a sensor. 

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