An Amperometric Biosensor for Glucose Based on Electrodeposited Redox Polymer/Glucose Oxidase Film on a Gold Electrode

Abstract

Since Clark and Lyons developed the first enzyme-based oxygen electrode, 1 enzyme-based biosensors have been used in an increasing number of clinical, environmental, agriculture, and biotechnological applications. [2][3][4][5] In response to the needs for frequent or continuous monitoring of glucose in diabetics, particularly in brittle diabetics, glucose sensors are, by far, the most widely employed, and therefore continue to drive research toward better sensors. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Since the redox centers (FAD/FADH2) of glucose oxidase (GOX) are prevented from transferring electrons to an electrode surface by an insulating glycoprotein shell, 6 the presence of a mediator is necessary to achieve direct electron-exchange between the electrode and the redox center of GOX. The pioneering work of Heller 7,8 demonstrated that it is possible to modify GOX with ferrocene derivatives and ruthenium pentaamimine, thus promoting relayed electron-transfer to the electrode.A further experimental and theoretical study 9 revealed that the rates of intramolecular electron-transfer are very sensitive to the particular ferrocene derivative employed, and also the distance between the flavin ring and the point of covalent attachment of the mediator. It is not necessary to have a large number of mediator molecules attached; they need instead to be in the "right" locations. Terathiafulvalence (TIF) and its derivatives are another group of redox molecules that can mediate the direct oxidation of GOX.10-12 However, hydrophobically incorporated TIF is slowly lost from the enzyme, presumably due to its slight solubility in aqueous solution and its enhanced solubility in the oxidized (TIF + ) form, which ultimately limits the use of this approach.Electrically "wired" enzymes by redox hydrogels were introduced by Heller's group, [13][14][15] and provided three-dimension electronic conductivity between enzymes and electrodes. Redox hydrogel films are unique in having adequate electron diffusion coefficients and in being permeable to water-soluble substrates and products of enzymatic reactions. 16 When a crosslinked redox polymer network electrically "wired" an enzyme covalently bound to it, the gel and the substrate electrode formed an enzyme electrode. Unlike enzyme electrodes based on diffusional mediators, they are potentially useful in a flow system and in vivo determination. Heller's group carried out a series of studies, [17][18][19][20][21][22][23] and employed the redox hydrogels for sensors implanted in the subcutaneous tissue of rats 19 and in the vascular bed. 23 It is reported that upon illumination, the redox polymer formed by coordinating [Os(bpy)2Cl + /Os(bpy)2Cl] 2+ to poly(4-vinyl-pyridine) exchanges its inner-sphere chloride with more strongly coordinating pyridine or imidazole groups on the polymer backbones. 24 The resulting films conduct electrons when they are hydrated, and their redox segments are mobile enough to collide, even though they are tethered to the crosslinked ...

Use of an Osmium Complex as a Universal Luminescent Probe for Enzymatic Reactions

“…The great importance of detecting low concentrations of glucose in body fluids has led to the development of many different and sophisticated methods in which GOx is frequently included. [22,23] By coupling the activity of GOx and horseradish peroxidase (HRP) in our fluorescence assay, we have been able to detect micromolar amounts of glucose. The mechanism of operation of this system is depicted in Fig ferent concentrations of H 2 O 2 and glucose, respectively.…”

Controlled electrophoretic deposition of multifunctional nanomodules for bioelectrochemical applications

“…Layer-by-layer electrodeposition of redox polymer/enzyme composition films on screen-printed carbon electrodes for fabrication of reagentless enzyme biosensors has been used for producing a very stable and rigid films (Gao and Yang, 2004). A glucose biosensor based on the one-step coelectrodeposition of an ORP and GOX on a Au electrode surface has been developed (Fei et al, 2003). Electrodeposition of hydrated redox polymers and co-electrodeposition of enzymes through coordinate crosslinking has been proved to produce stable enzymes films with excellent catalytic activity (Gao et al, 2002).…”

Gold electrodes with rough surfaces. The Golden Hedgehog Project

“…These porous gold structures have multiple applications in catalysis, medicine and as sensors [1][2][3][4][5][6][7][8]. Biocompatibility, high conductivity and chemical resistance make these Au films a perfect platform for building functional biosensors.…”