Glucose oxidase deposition

Matsumoto N, Chen X, Wilson GS. Fundamental studies of glucose oxidase deposition on a Pt electrode. Analytical Chemistry 2002, 74, 362-367. 

Fimre 8. a) Schematical representation of an amperometric biosensor with a pyr- role-modified enzyme copolymerized with pyrrole, b) Comparison of calibration graphs for glucose obtained with electrodes based on 1) pyrrole-modified ucose oxidase copolymerized with pyrrole (d osition charge 184.2 pA s) and 2) conventionally polypyrrole-entrapped native glucose oxidase (deposition charge 184.6 pA s). 

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 12.5 (a) Layer-by-layer deposition of glucose oxidase and the polyallylamine Os3 +n + -polypyridine polyelectrolyte on the electrode, (b) Typical catalytic current responses for different glucose concentrations obtained by self-assembled nanostructured thin films based on different architectures (i) PAH/Os/GOx, (ii) cysteamine/GOx/PAH-Os, (iii) PAH/GOx/ -Os, and (iv) (PAH-Os)2/(GOx)i. All measurements were performed in 0.1 M tris buffer at pH 7.5. Part (b) Reproduced with permission from Ref. 34a. Copyright Wiley-VCH Verlag GmbH Co. KGaA. 

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.

Figure 8.12 Schematic illustration of the layer-by-layer deposition on an Au electrode initially with positively charged poly(diallydimethylammonium) chloride (PDDA) and negatively charged poly(sodium 4-styrenesulfonate). Subsequent depositions entailed (I) PDDA-modified Prussian blue nanoparticles (P-PB), followed by (II) negatively charged glucose oxidase (GOx).55 (Reprinted with permission from W. Zhao et al., Langmuir 2005, 21, 9630-9634. Copyright 2005 American Chemical Society.) (See color insert.)...

Film Fabrication. The platinum electrode (0.28 cm area) was fabricated and cleaned as previously described (19). Thin films of AQ-enzyme were prepared by dissolving an amount of the enzyme, as indicated below, in 10 il of 1.5% AQ polymers solution at room temperature. Two aliquots of 5 il were deposited atop the platinum electrode and the first aliquot was allowed to dry before the second addition. This procedure corresponds to the first protocol. In addition, for the second protocol, 10 il of the 0.5% Nafion solution was casted atop the dried AQ-enzyme film and the methanol was allowed to evaporate at room temperature. The third protocol consisted in the deposition of 10 il of a 1% of AQ solution containing the enzyme, atop the platinum electrode followed by heating in an oven at 50°C during 30 min. In each case, 2 U of glucose oxidase were used. 

Figure 1. Current-time curves of glucose biosensors prepared A) in depositing the mixture of glucose oxidase and AQ atop the platinum electrode and allowing the solvent to evaporate at room temperature, B) in covering this AQ-glucose oxidase film with a Nafion layer or C) in heating the AQ-glucose oxidase film at 50°C in an oven for 30 min. The assays were done with 20 mM of glucose at pH 7.

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. 

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