Comparison of Direct and Mediated Electron Transfer in Electrodes with Novel Fungal Flavin Adenine Dinucleotide Glucose Dehydrogenase

Abstract

Direct and mediated electron transfer (DET and MET) in enzyme electrodes with a novel flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) from fungi are compared for the first time. DET is achieved by placing a single-walled carbon nanotube (CNT) between GDH and a flat gold electrode where the CNT is close to FAD within the distance for DET. MET is induced by using a free electron transfer mediator, potassium hexacyanoferrate, and shuttles electrons from FAD to the gold electrode. Cyclic voltammetry shows that the onset potential for glucose response current in DET is smaller than in MET, and that the distinct redox current peak pairs in MET are observed whereas no peaks are found in DET. The chronoamperometry with respect to a glucose biosensor shows that (i) the response in DET is more rapid than in MET; (ii) the current at more than +0.45V in DET is larger than the current at the current-peak potential in MET; (iii) a DET electrode covers the glucose concentration range for clinical requirements and is not susceptible to interfering agents at +0.45 V; and (iv) a DET electrode with the novel fungal FAD-GDH does not affect sensing accuracy in the presence of up to 5 mM xylose, while it often shows a similar response level to glucose with other conventionally used fungus-derived FAD-GDHs. It is concluded that our DET system overcomes the disadvantage of MET.

Diameter dependence of single-walled carbon nanotubes with flavin adenine dinucleotide glucose dehydrogenase for direct electron transfer bioanodes

“…Given this, we adopt +0.35 V in DET because it is the optimum potential which surpasses the current-peak potential (+0.35 V) in the MET system where potassium hexacyanoferrate(III) {K 3 [Fe(CN) 6 ]} is often used as an electron transfer mediator (instead of SWCNTs). 3,5) The fact that DET electrodes with SWCNTs show better performance than a MET electrode is remarkable. DET is a so-called mediatorless approach and overcomes the disadvantages of MET partly because the electron at FAD does not come via a mediator having a specific redox potential but is sent directly to the electrode.…”

“…Flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) has been the subject of an increasing number of reports on biosensors [1][2][3][4][5][6][7] and biofuel cells. 2,3,[8][9][10] The advantage of FAD-GDH is that it is (i) oxygeninsensitive, unlike FAD-dependent glucose oxidase, and (ii) highly selective, unlike pyrroloquinoline quinone-dependent GDH.…”

“…Flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) has been the subject of an increasing number of reports on biosensors [1][2][3][4][5][6][7] and biofuel cells. 2,3,[8][9][10] The advantage of FAD-GDH is that it is (i) oxygeninsensitive, unlike FAD-dependent glucose oxidase, and (ii) highly selective, unlike pyrroloquinoline quinone-dependent GDH. The main issue of FAD-GDH for biosensor and biofuel cell applications is the construction of an electron transfer configuration between an electron collector (electrode) and a FAD cofactor which is buried deep (∼1.4 nm) below the protein surface.…”

“…11) Our groups have already reported a direct electron transfer (DET) between FAD-GDH and a single-walled carbon nanotube (SWCNT). [1][2][3] A nanometer-scale SWCNT can be brought close to a FAD cofactor of GDH deeply embedded in a structurally rigid glycoprotein shell within the distance for DET.…”

“…However, our previous work addressed only one kind of SWCNT. [1][2][3] The characteristics of SWCNTs such as their diameter, length, distribution, chirality, purity, and residual materials are strongly influenced by the manufacturing method. This research aims to address the diameter of SWCNTs because it is thought to affect DET performance.…”