Redox enzymes adsorbed

In this chapter, we review the recent progress in the development of different metal oxide nanoparticles with various shapes and size for fabrication of biosensors. The development of metal oxide nanomaterials surface film for direct electron exchange between electrodes and redox enzymes and proteins will be summarizing. The electrochemical properties, stability and biocatalytic activity of the proposed biosensors will be discussed. The biocompatibility of the metal oxide nanomaterials for enzymes and biomolecules will be evaluated. We will briefly describe some techniques for the investigation of proteins and enzymes when adsorbed to the electrode surfaces. Cyclic voltammetry, impedance spectroscopy, UV-visible spectroscopy and surface imaging techniques were used for surface characterization and bioactivity measuring. 

Figure 1.5 Schematic representation of biosensor architectures based on direct ET (a) via an oriented adsorbed redox enzyme (b) via a redox enzyme coupled to a self-assembled monolayer (SAM).

The discovery of new materials such as nanoparticles and nanotubes has led to their use in electrochemical sensors in combination with ferrocene mediators and redox enzymes. Davis and co-workers modified single-wall carbon nanotubes (SWCNTs) by adsorbing glucose oxidase to them and then used a soluble ferrocene derivative as a... 

Figure 15 illustrates a schematic model of an expected electron flow from the substrate to the electrode through the redox centers in the enzyme adsorbed on the electrode surface the heme group (denoted as B in Fig. 15) is functioning as a built-in mediator to... 

Many redox enzymes can be denatured if the pH of the solution is taken too far from neutral or if nonaqueous solvents are used. It is therefore desirable, although not always essential, to use neutral aqueous solutions in the electropolymerization process, thus restricting the choice of monomers that can be used. One way to overcome this problem is to incorporate, or immobilize, the enzyme after deposition of the polymer film. This allows a much wider choice of deposition conditions. In addition to adsorbing the enzyme onto preformed poly(pyrrole) films, " GOx has also been covalently immobilized onto a wide range of preformed 3- and N-derivatized pyrrole carboxylates or onto N-amino-substituted pyrroles. This technique may increase current densities at a given glucose concentration by as much as twentyfold when compared to the best results obtained elsewhere. The authors make no claims for direct electron transfer between enzyme... 

The hydrophobic nature of membrane-bound redox enzymes, such as this fructose dehydrogenase, provides an obvious route to gentle, stabilizing immobilization in hydrophobic adsorbed layers on electrodes which mimic the cell... 

For enzymes adsorbed on an electrode, both nonturnover and catalytic studies can be carried out. Nonturnover measurements are essentially the same as mentioned earlier, and focus on the active site redox transitions occurring in the absence of substrate. Addition of the substrate to the electrolyte results in catalytic... 

---