Mediators , amperometric biosensor systems

First immunosensor Ovalbumin on a platinum wire First fiber-optic pH sensor for in vivo blood gases First fiber-optic-based biosensor for glucose First surface plasmon resonance (SPR) immunosensor First mediated amperometric biosensor for the detection of glucose Launch of the MediSense ExacTech blood glucose biosensor SPR-based biosensor system i-STAT launches hand-held blood analyzer Glucocard launched... 

Tetrathiafulvalene containing polymeric electron transfer systems Tetrathiafulvalene (TTF) is another mediator many researchers have utilized as an electron mediator in constructing amperometric biosensors. Electrodes constructed of TTF efficiently oxidize glucose oxidase [118,119], lactate oxidase [120] and choline oxidase [121]. These sensors like those using viologen containing polymeric electron transfer systems have the... 

First ferrocene-mediated amperometric glucose biosensor by Cass et al. [135]. The work led to the development of the first electronic blood glucose measuring system which was commercialized by MediSense Inc. (later bought by Abbott Diagnostics) in 1987. 

Vidal, J.C., E. Garcia, and J.R. Castillo. 2002. Development of a platinized and ferrocene-mediated cholesterol amperometric biosensor based on electropolymerization of polypyrrole in a flow system. Anal Sci 18 (5) 537. 

As far as the use of ferrocene molecules as amperometric sensors is concerned, they have found wide use as redox mediators in the so-called enzymatic electrodes, or biosensors. These are systems able to determine, in a simple and rapid way, the concentration of substances of clinical and physiological interest. The methodology exploits the fact that, in the presence of enzyme-catalysed reactions, the electrode currents are considerably amplified.61 Essentially it is an application of the mechanism of catalytic regeneration of the reagent following a reversible charge transfer , examined in detail in Chapter 2, Section 1.4.2.5 ... 

The covalent attachment of electron transfer mediators to siloxane or ethylene oxide polymers produces highly efficient relay systems for use in amperometric sensors based on flavin-containing oxidases. It is clear from the response curves that the biosensors can be optimized through systematic changes in the polymeric backbone. The results discussed above, as well as those described previously (25-32), show that the mediating ability of these flexible polymers is quite general and that it is possible to systematically tailor these systems in order to enhance this mediating ability. 

The kinetic behaviour of electrochemical biosensors is most commonly characterized using the dependence of the steady-state amperometric current on the substrate concentration. This type of analysis has some limitations because it does not allow for a decoupling of the enzyme-mediator and enzyme-substrate reaction rates. The additional information required to complete the kinetic analysis can be extracted either from the potential dependence of the steady-state catalytic current or from the shift of the halfwave potential with substrate concentration [154]. Saveant and co-workers [155] have presented the theoretical analysis of an electrocatalytic system... 

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