Glucose oxidase electrochemical deposition

Entrapment of biochemically reactive molecules into conductive polymer substrates is being used to develop electrochemical biosensors (212). This has proven especially useful for the incorporation of enzymes that retain their specific chemical reactivity. Electropolymerization of pyrrole in an aqueous solution containing glucose oxidase (GO) leads to a polypyrrole in which the GO enzyme is co-deposited with the polymer. These polymer-entrapped GO electrodes have been used as glucose sensors. A direct relationship is seen between the electrode response and the glucose concentration in the solution which was analyzed with a typical measurement taking between 20 to 40 s. 

Figure 1.2 Electrochemical deposition of glucose oxidase (GOx) followed by electropolymerization of the polyphenol interference layer. Reprinted with permission from Ref. 40. Copyright 2002 American Chemical Society.

Plasma polymerized N-vinyl-2-pyrrolidone films were deposited onto a poly(etherurethaneurea). Active sites for the immobilization were obtained via reduction with sodium borohydride followed by activation with l-cyano-4-dimethyl-aminopyridinium tetrafluoroborate. A colorometric activity determination indicated that 2.4 cm2 of modified poly(etherurethaneurea) film had an activity approximately equal to that of 13.4 nM glucose oxidase in 50 mM sodium acetate with a specific activity of 32.0 U/mg at pH 5.1 and room temperature. Using cyclic voltammetry of gold in thin-layer electrochemical cells, the specific activity of 13.4 nM glucose oxidase in 0.2 M aqueous sodium phosphate, pH 5.2, was calculated to be 4.34 U/mg at room temperature. Under the same experimental conditions, qualitative detection of the activity of a modified film was demonstrated by placing it inside the thin-layer cell. 

All electrodes react with their environment via the surfaces in ways which will determine their electrochemical performance. Properly selected surface modification can effectively enhance the electrode heterogeneous catalysis property, especially selectivity and activity. The bulk materials can be chosen to provide mechanical, chemical, electrical, and structural integrity. In this part, several surface modification methods will be introduced in terms of metal film deposition, metal ion implantation, electrochemical activation, organic surface coating, nanoparticle deposition, glucose oxidase (GOx) enzyme-modified electrode, and DNA-modified electrode. 

Sol-gel films can be used to immobilize biomolecules. For example, Dong etal. developed thin sol-gel films on electrodes in which enzymes horseradish peroxidase (HRP) and glucose oxidase (GOD) were used to determine enzyme substrates [12]. A vapor-deposition sol-gel process [13] featuring a thin film of aqueous HRP solution into which titanium isopropoxide vapor was diffused to form a Ti02 sol-gel film incorporating HRP prevented denaturation of the enzyme. Surfactants were used in preparation of sol-gel films incorporating redox proteins on electrodes to improve porosity and electrochemical and catalytic performance [14]. 

Two methods for the spatially controlled deposition of proteins on microelectrodes are described. The first technique involves the entrapment of glucose oxidase in photopolymerized polyHK. The second uses electrochemically aid adsorption to deposit urease and to co-deposit glucose oxidase with bovine serum albumin. Both techniques were found to lead to active deposits and the properties and optimisation of the deposition procedures will be described. Further, to facilitate glucose measurement in complex medi the depointion of a thin film of polypyrrole following that of the protdns is described. The properties of s film with respect to two model interferents and complex yeast extract medium will be reported. 

Hoshi T, Hiwatashi Y, Anzai JI (2004) Electrochemical deposition of avidin with ascorbate oxidase on the surface of platinum electrodes for amperometric glucose sensors. ITE Lett Batt New Technol Med 5(6) 552-555... 

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