Covalent Attachment of Osmium Complexes to Glucose Oxidase and the Application of the Resulting Modified Enzyme in an Enzyme Switch Responsive to Glucose

Abstract

Pyridine-based osmium complexes bearing either a carboxylate or aldehyde group were covalently attached to glucose oxidase and were shown to work as mediators for the reoxidation of the enzyme. For the complex containing the carboxylate group, the binding was made through carbodiimide coupling to the amine residues in the protein. For the complex containing the aldehyde group, the reductive coupling was carried out by condensation with the amino groups on the protein in the presence of sodium cyanoborohydride. Electrochemical studies show evidence for both intramolecular and intermolecular redox mediation for the electrochemical reoxidation of the modified glucose oxidases in the presence of glucose. The modified enzymes adsorbed on glassy carbon and platinum show different electrochemical responses for the two electrode materials, suggesting that orientation of the adsorbed enzyme is induced due to the interaction of the osmium complex with the different surfaces. Construction of enzyme switches based on these modified enzymes was carried out, and their responses were compared with those obtained using native glucose oxidase and a soluble redox mediator.

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

“…These characteristic absorbance spectra corresponding to the oxidised and reduced forms were also observed in other similar osmium complexes. [20,21] However, very little is known about the fluorescence properties of osmium complexes with other pyridinederived ligands than bipyridine. Figure 1B shows the emission spectra of the osmium complex in its reduced and oxidised form.…”

One‐Step Electrochemically Deposited Nanocomposite Film of CS‐Fc/MWNTs/GOD for Glucose Biosensor Application

“…In the case of amperometric biosensor, the effective immobilization of an enzyme on an electrode surface with a high retention of its biological activity is a crucial point for the commercial development of biosensors [5,6]. To improve the immobilization efficiency, many immobilization methods, including physical adsorption [7], covalent or cross-linking [8], self-assembly [9], and electrodeposition [10] have been developed. Compared with traditional process, electrodeposition method is simple and suitable for selective deposition of films with controllable thickness [11,12], and moreover, other substances such as carbon nanotubes (CNTs) [13] and even enzymes [14] can be effectively incorporated into the film to form biocomposites.…”

Direct Electron Transfer of Glucose Oxidase Molecules Adsorbed onto Carbon Nanotube Powder Microelectrode

“…4 Although some groups have employed mediators to impose electron contact between the redox enzymes and electrodes, 5,6 direct electron transfer is more attractive because it could help us not only to understand the intrinsic redox behaviors of enzymes, but also to develop the mediatorless biosensors. 7,8 Various methods have been used to achieve this goal: modifying the electrode surface with promoters, 9 modifying the redox protein with electron replay, 10 immobilizing the enzyme in redox polymer matrixes 11 and adsorbing the enzyme on an electrode surface, 12 for example.…”