Magnetic-field-induced orientation of fructose dehydrogenase on iron oxide nanoparticles for enhanced direct electron transfer

Carbon-Encapsulated Iron Nanoparticles as a Magnetic Modifier of Bioanode and Biocathode in a Biofuel Cell and Biobattery

This work demonstrates the application of magnetic carbon-encapsulated iron nanoparticles (CEINs) for the construction of bioelectrodes in a biobattery and a biofuel cell. It has been shown that carbon-encapsulated iron nanoparticles are a suitable material for the immobilization of laccase (Lc) and 1,4-naphthoquinone (NQ) and fructose dehydrogenase (FDH). The system is stable; no leaching of the enzyme and mediator from the surface of the modified electrode was observed. The onset of the catalytic reduction of oxygen to water was at 0.55 V, and catalytic fructose oxidation started at −0.15 V. A biobattery was developed in which a zinc plate served as the anode, and the cathode was a glassy carbon electrode modified with carbon-encapsulated iron nanoparticles, laccase in the Nafion (Nf) layer. The maximum power of the cell was ca. 7 mW/cm2 at 0.71 V and under external resistance of 1 kΩ. The open-circuit voltage (OCV) for this system was 1.51 V. In the biofuel cell, magnetic nanoparticles were used both on the bioanode and biocathode to immobilize the enzymes. The glassy carbon bioanode was coated with carbon-encapsulated iron nanoparticles, 1,4-naphthoquinone, fructose dehydrogenase, and Nafion. The cathode was modified with carbon-encapsulated magnetic nanoparticles and laccase in the Nafion layer. The biofuel cell parameters were as follows: maximum power of 78 µW/cm2 at the voltage of 0.33 V and under 20 kΩ resistance, and the open-circuit voltage was 0.49 V. These enzymes worked effectively in the biofuel cell, and laccase also effectively worked in the biobattery.

Recent Progress in Applications of Enzymatic Bioelectrocatalysis

Bioelectrocatalysis has become one of the most important research fields in electrochemistry and provided a firm base for the application of important technology in various bioelectrochemical devices, such as biosensors, biofuel cells, and biosupercapacitors. The understanding and technology of bioelectrocatalysis have greatly improved with the introduction of nanostructured electrode materials and protein-engineering methods over the last few decades. Recently, the electroenzymatic production of renewable energy resources and useful organic compounds (bioelectrosynthesis) has attracted worldwide attention. In this review, we summarize recent progress in the applications of enzymatic bioelectrocatalysis.

Direct electron transfer-type bioelectrocatalysis of FAD-dependent glucose dehydrogenase using porous gold electrodes and enzymatically implanted platinum nanoclusters

The direct electron transfer (DET)-type bioelectrocatalysis of flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase (GDH) from Aspergillus terreus (AtGDH) was carried out using porous gold (Au) electrodes and enzymatically implanted platinum nanoclusters (PtNCs). The porous Au electrodes were prepared by anodization of planar Au electrodes in a phosphate buffer containing glucose as a reductant. Moreover, PtNCs were generated into AtGDH by an enzymatic reduction of hexachloroplatinate (IV) ion. The modification was confirmed by native polyacrylamide gel electrophoresis and sodium dodecyl sulfate polyacrylamide gel electrophoresis analyses. The AtGDH-adsorbed porous Au electrode showed a DET-type bioelectrocatalytic wave both in the presence and absence of PtNCs; however, the current density with PtNCs (~1 mA cm^-2 at 0 V vs. Ag|AgCl|sat. KCl) was considerably higher than that without PtNCs. The kinetic and thermodynamic analysis of the steady-state catalytic wave indicated that inner PtNCs shortened the distance between the catalytic center of AtGDH (=FAD) and the conductive material, and improved the heterogeneous electron transfer kinetics between them.

The influence of the shape of Au nanoparticles on the catalytic current of fructose dehydrogenase

Graphite electrodes were modified with triangular (AuNTrs) or spherical (AuNPs) nanoparticles and further modified with fructose dehydrogenase (FDH). The present study reports the effect of the shape of these nanoparticles (NPs) on the catalytic current of immobilized FDH pointing out the different contributions on the mass transfer-limited and kinetically limited currents. The influence of the shape of the NPs on the mass transfer-limited and the kinetically limited current has been proved by using two different methods: a rotating disk electrode (RDE) and an electrode mounted in a wall jet flow-through electrochemical cell attached to a flow system. The advantages of using the wall jet flow system compared with the RDE system for kinetic investigations are as follows: no need to account for substrate consumption, especially in the case of desorption of enzyme, and studies of product-inhibited enzymes. The comparison reveals that virtually identical results can be obtained using either of the two techniques. The heterogeneous electron transfer (ET) rate constants (k_S) were found to be 3.8 ± 0.3 s^-1 and 0.9 ± 0.1 s^-1, for triangular and spherical NPs, respectively. The improvement observed for the electrode modified with AuNTrs suggests a more effective enzyme-NP interaction, which can allocate a higher number of enzyme molecules on the electrode surface. Graphical abstract The shape of gold nanoparticles has a crucial effect on the catalytic current related to the oxidation of D-(-)-fructose to 5-keto-D-(-)-fructose occurring at the FDH-modified electrode surface. In particular, AuNTrs have a higher effect compared with the spherical one.

Bioelectrocatalytic performance of d-fructose dehydrogenase

This review summarizes the bioelectrocatalytic properties of d-fructose dehydrogenase (FDH), while taking into consideration its enzymatic characteristics. FDH is a membrane-bound flavohemo-protein with a molecular mass of 138 kDa, and it catalyzes the oxidation of d-fructose to 5-keto-d-fructose. The characteristic feature of FDH is its strong direct-electron-transfer (DET)-type bioelectrocatalytic activity. The pathway of the DET-type reaction is discussed. An overview of the application of FDH-based bioelectrocatalysis to biosensors and biofuel cells is also presented, and the benefits and problems associated with it are extensively discussed.