Biocatalytic anodes

In this section, the enzymes, and associated substrates, used as biocatalysts in anodes are presented. For the development of biocatalytic anodes, there is a wide range of fuels available for use as substrates, such as alcohols, lactate, hydrogen, fructose, sucrose, all of which can be oxidized by biocatalysts. The fuel that is the most widely considered, however, in the context of an implantable biocatalytic fuel cell is glucose. We shall focus our attention on this fuel, but will mention briefly research on the use of some other fuels in biocatalytic anodes. 

Palmore et al. [91] have reported on a graphite plate biocatalytic anode that uses solution-phase dehydrogenases to catalyse the successive oxidation of methanol to C02. 

Simon et al. [92] investigated a biocatalytic anode based on lactate oxidation by lactate dehydrogenase (LDH). The anodic current is generated by the oxidation of NADH (produced by NAD+ and substrate) while LDH catalyzes the electro-oxidation of lactate into pyruvate. As previously mentioned, the oxidation of NADH at bare electrodes requires a large overpotential, so these authors used poly(aniline) films doped with polyanions to catalyze NADH oxidation. Subsequent research by this group focused on targeting mutants of LDH that are amenable to immobilization on the polyaniline surface [93],... 

Figure 24. (A) Schematic configuration of a noncompartmentalized biofuel cell employing glucose and O as fuel and oxidizer, and using PQQ- FAD/GOx- and Cyt c/COx-functionalized electrodes as biocatalytic anode and cathode, respectively. (B) Current-voltage behavior of the biofuel cell at different external loads. Inset electrical power extracted from the biofuel cell at different external...

Co-immobihzation of mediator and enzyme may be achieved using a novel reconstitution approach. For example, Katz et al. [15] have developed a biocatalytic anode functionahzed by a surface reconstitution of apo-GOx onto FAD that was previously coupled to a pyrrolo-quinohne quinine (PQQ) relay conjugated to a self-assembled monolayer of cysteamine on gold. The CV study of this assembly in the presence of glucose yields an electrocatalytic current for glucose oxidation commencing at... 

Vaze, A., Hussain, N., Tang, C., Leech, D., Rusling, J. Biocatalytic anode for glucose oxidation utilizing carbon nanotubes for direct electron transfer with glucose oxidase Electrochem. Comm. 11(10), 2004-2007 (2009). doi 10.1016/j.elecom.2009.08.039... 

FIGURE 18.18 Magnetically controlled biological fuel cell with the biocatalytic anode based on the reconstituted NAD -dependent LDH and biocatalytic cathode based on the reconstituted COx/Cyt c system. Vector B shows the direction of the applied magnetic field. (Adapted with permission from Ref. [120]. Copyright 2005, American Chemical Society.)... 

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