Direct Bioelectrocatalysis of PQQ‐Dependent Glucose Dehydrogenase

Abstract

The direct bioelectrocatalysis was demonstrated for pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-dependent GDH) covalently attached to single-walled carbon nanotubes (SWNTs). The homogeneous ink-like SWNT suspension was used for both creating the SWNT network on the microelectrode carbon surface and for enzyme immobilization. Functionalization of the SWNT surface by forming active ester groups was found to considerably enhance SWNT solubility in water with a range from 0.1 to 1.0 mg/mL. The PQQ-dependent GDH immobilized on the surface of the SWNTs exhibited fast heterogeneous electron transfer with a rate constant of 3.6 s À1 . Moreover, the immobilized PQQ-dependent GDH retained its enzymatic activity for glucose oxidation. A fusion of PQQ-dependent GDH with SWNTs has a great potential for the development of low-cost and reagentless glucose sensors and biofuel cells.

Starch‐Powered Biofuel Cell Activated by Logically Processed Biomolecular Signals

“…[9,10] PQQ-GDH and laccase enzymes are known for their direct electron transfer with an electrode support composed of CNTs. [32] Characterization of the enzymemodified electrodes (cyclic voltammetry, enzyme content, etc.) has been described in detail elsewhere.…”

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“…These include but are not limited to the development of various techniques for sufficient enzyme immobilization trough physical adsorption [8], covalent attachment [9], physical entrapment and tethering of enzymes [10]. Mediators have been used to enhance electron transfer rate [6,9,11] and carbon or mesoporous materials with diameters comparable to the size of the enzyme were explored for enhanced enzyme-electrode interactions [12]. The following approaches provide proper enzyme orientation: specific covalent attachment of enzymes to the electrode surface [13,14]; protein engineering …”

Enzymatic Glucose Biofuel Cell and its Application

“…Another major advancement was described by Heller [10], where an osmium-based redox hydrogel was employed to immobilize both GOx and copper oxidase on the bioanode and biocathode, respectively. This enabled the communication between the enzyme and the current collector and resulted in a high open circuit voltage of 0.8 V. Moreover, the development of stable and continuous enzymatic biofuel cells designed to catalyze the oxidation of fuel continues to be limited by low power densities [10,29,45,46]. Ivnitski et al [45] employed SingleWalled Carbon Nanotube (SWCNT) anodic substrate modified with Pyroloquinoline Quinone Glucose Dehydrogenase (PQQ-GDH) in the implementation to enhance the power densities generated.…”

“…This enabled the communication between the enzyme and the current collector and resulted in a high open circuit voltage of 0.8 V. Moreover, the development of stable and continuous enzymatic biofuel cells designed to catalyze the oxidation of fuel continues to be limited by low power densities [10,29,45,46]. Ivnitski et al [45] employed SingleWalled Carbon Nanotube (SWCNT) anodic substrate modified with Pyroloquinoline Quinone Glucose Dehydrogenase (PQQ-GDH) in the implementation to enhance the power densities generated. The use of SWCNT as the bioanode substrate material in half-cell electrochemistry, for the first time, demonstrated DET between the active sites of PQQ-GDH and SWNT as characterized by cyclic voltammetry.…”