Signal transduction, enzyme/electrode

Amperometric Transduction of Optical Signals Recorded by Photoisomerizable Enzyme Electrodes... 

Alfonta, L., Bardea, A., Khersonsky, O., Katz, E., Willner, I. (2001). Chronopotentiometry and faradaic impedance spectroscopy as signal transduction methods for the biocatalytic precipitation of an insoluble product on electrode supports routes for enzyme sensors, immunosensors and DNA sensors. Biosens Bioelectron 16, 675-687. 

The selectivity of enzyme electrodes can be improved by means of another coupling principle that is capable of filtering chemical signals by eliminating interferences of the enzyme or electrode reaction caused by constituents of the sample. Compounds that interfere with signal transduction, e.g., ascorbic acid with anodic oxidation of hydrogen peroxide, can be transformed into inert products by reaction with an eHminator or anti-interference enzyme (e.g., ascorbate oxidase). Since the conversion of analyte and interferent proceed in parallel, both the eliminator and the indicator enzyme may be co-im-mobilized in one membrane. On the other hand, constituents of the sample that are at the same time intermediates of coupled enzyme reactions can be eliminated before they reach the indicator enzyme layen For this purpose several different enzyme... 

Biosensors based on nanomaterials exploit many new signal transduction technologies in their manufacture [345], In molecular electronics and sensors, conducting polymers represent innovative systems for the immobilization of enzymes [346, 347], The entrapment of enzymes in polymeric films provides a controlled method to fasten biologically active molecules in a defined area on the electrodes. These examples show that conducting polymers in the area of bioanalytical sciences are of great interest since their biocompatibility opens up the possibility of using them as in vivo biosensors. 

Connecting an electrode with a redox enzyme and controlling the dynamics of the resulting system is an important and an actively pursued objective. It indeed allows the transduction of specific chemical events taking place at the prosthetic group of the enzyme into easy-to-use electric signals or, conversely, to trigger and control enzymatic reactions by easy-to-manipulate potential and current variables. Applications may concern biosensors and preparative-scale transformations [1-6]. 

It is beyond the scope of this chapter to attempt to describe the myriad combinations of biological and sensor elements possible, so only improvements in the design of amperometric biosensors, commonly referred to as enzyme-modified electrodes, wiU be discussed. The favored configuration for biosensors utilizes amperometry (measurement of electric current) for transduction of the chenfical signal into an electroinc signal [3]. Electrochemical instrumentation is simple and... 

Photostimulation of redox enzymes could transduce recorded optical signals as an amperometric response by their electrical interaction with electrode interfaces. For example, amperometric transduction of recorded optical signals was accomphshed using nitrospiropyran-modified glucose oxidase as photoswitchable material (Fig. 44) [14]. 

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