Third‐generation Sulfite Biosensor Based on Sulfite Oxidase Immobilized on Aminopropyltriethoxysilane Modified Indium Tin Oxide

Abstract

In this paper we report a sulfite biosensor based on immobilization and bioelectrocatalysis of human sulfite oxidase (hSO) on indium tin oxide (ITO). Stable immobilization of catalytically active enzyme in a direct electron transfer configuration was achieved after modification of ITO with aminopropyltriethoxysilane (APTES). The electrochemical characteristics of the hSO modified electrode have been investigated by cyclic voltammetry for various pretreatment and binding conditions. Amperometry was utilized to demonstrate the current responses of the sulfite sensor toward sodium sulfite in an aqueous solution under the optimized conditions. The proposed sulfite sensor exhibits a fast response and high sulfite sensitivity with a linear range of 0.5 to 2 μM. An additional polyvinyl alcohol (PVA) cover membrane was applied to extend the linear working range. As a result, the upper concentration in the linear range for the sulfite sensor was extended from 2 μM to 20 μM for 5 % PVA. In addition, the sulfite sensor with PVA has improved storage stability when kept in 0.5 mM Tris‐buffer, pH 7.0 at 4 °C.

Direct Electron Transfer of Enzymes Facilitated by Cytochromes

“…Power densities of 1 and 8 μW cm −2 were achieved at different polarization potentials. A third‐generation sulfite biosensor was developed based on human sulfite oxidase on indium tin oxide, which exhibited a sensitivity of 35 nA mM −1 and a linear range between 0.5–20 μM . Another sulfite biosensor was developed using bacterial sulfite dehydrogenase, cytochrome c as mediator and a self‐assembled monolayer of 11‐mercaptoundecanol cast on a gold electrode …”

Transient Catalytic Voltammetry of Sulfite Oxidase Reveals Rate Limiting Conformational Changes

“…Sulfite oxidase and the closely related bacterial sulfite dehydrogenases have been immobilized on pyrolytic graphite edge electrodes 19,20 , gold electrodes modified with thiols 21 or nanoparticles [22][23][24] , and silver electrodes 25 , either to gain mechanistic information, or in the perspective of constructing sulfite biosensors 26 or the anodes of sulfite-based biofuel cells 27 .…”

Direct Electrochemistry of Molybdenum and Tungsten Enzymes

“…Zeng and coworkers were able to further improve this assembly by fine-tuning the coating of the nanoparticles, leading to improved rates of interfacial electron transfer between the heme and the electrode [65]. They also explored the possibility of making a sulfite/oxygen fuel cell using nanostructured gold electrodes [66], and wiring sulfite oxidase to quantum-dots modified indium tin oxide electrodes, in order to catalyze the photo-oxidation of sulfite [67]; a similar configuration was also recently used by Saengdee and coworkers to develop a sulfite biosensor [68].…”