Direct electron transfer of glucose oxidase on carbon nanotubes

Abstract

In this report, exploitation of the unique properties of single-walled carbon nanotubes (SWNT) leads to the achievement of direct electron transfer with the redox active centres of adsorbed oxidoreductase enzymes. Flavin adenine dinucleotide (FAD), the redox active prosthetic group of flavoenzymes that catalyses important biological redox reactions and the flavoenzyme glucose oxidase (GOx), were both found to spontaneously adsorb onto carbon nanotube bundles. Both FAD and GOx were found to spontaneously adsorb to unannealed carbon nanotubes that were cast onto glassy carbon electrodes and to display quasi-reversible one-electron transfer. Similarly, GOx was found to spontaneously adsorb to annealed, single-walled carbon nanotube paper and to display quasi-reversible one-electron transfer. In particular, GOx immobilized in this way was shown, in the presence of glucose, to maintain its substrate-specific enzyme activity. It is believed that the tubular fibrils become positioned within tunnelling distance of the cofactors with little consequence to denaturation. The combination of SWNT with redox active enzymes would appear to offer an excellent and convenient platform for a fundamental understanding of biological redox reactions as well as the development of reagentless biosensors and nanobiosensors.

Carbon Nanotubes for Electronic and Electrochemical Detection of Biomolecules

“…[111] Carbon nanotubes can be used as electrodes in conventional electrochemical cells, and can overcome the direct electron transfer barrier for glucose oxidase. [27,112] This has propelled carbon nanotubes into novel and highly sensitive bioamplification strategies. [30,31] Another area in which bioelectrochemistry has made excellent progress is in DNA hybridization sensors for diagnosing genetic diseases.…”

“…[128] Guiseppi-Elie and co-workers were first to report direct electron exchange between adsorbed GOx and FAD onto unoriented SWNT mats. [112] High temperature annealing (450 °C) of SWNTs was utilized to clean them from various surfactants and promote a more intimate physisorption of GOx onto SWNTs, achieving an electron transfer rate of 1.7 s −1 . [112] The covalent linking of GOx onto the tips of vertically aligned MWNT forests further enhanced the electron turnover rate to 1500 s −1 .…”

“…[112] High temperature annealing (450 °C) of SWNTs was utilized to clean them from various surfactants and promote a more intimate physisorption of GOx onto SWNTs, achieving an electron transfer rate of 1.7 s −1 . [112] The covalent linking of GOx onto the tips of vertically aligned MWNT forests further enhanced the electron turnover rate to 1500 s −1 . [129] In a more recent study, Willner et al [27] were able to further increase the electron turnover rate to 4100 s −1 by covalently linking the FAD cofactors to the tips of a SWNT forest.…”

“…Such devices will be readily adaptable to modern biomedical areas such as genomics, proteomics, cancer diagnostics, and metabolomics. Promising milestones include the 3-transistor arrays developed by Lieber et al, [93] and nanotube forests [112] and mats [139] reported on gold arrays.…”

Carbon nanotube-based transducers for immunoassays

“…Good electrochemical communication between multi-walled carbon nanotubes (MWNTs) and redox proteins have been observed both at the protein surface in the case of horse radish peroxidase (HRP) [5,6], cytochrome C [7] and azurin [8], and deep within the protein macrostructure e.g. glucose oxidase [9]. Azamian et al [10] observed adsorption of ferritin protein onto SWNTs which resulted in the solubilisation of SWNTs in water.…”