Recent Advances in the Direct Electron Transfer-Enabled Enzymatic Fuel Cells

Abstract

Direct electron transfer (DET), which requires no mediator to shuttle electrons from enzyme active site to the electrode surface, minimizes complexity caused by the mediator and can further enable miniaturization for biocompatible and implantable devices. However, because the redox cofactors are typically deeply embedded in the protein matrix of the enzymes, electrons generated from oxidation reaction cannot easily transfer to the electrode surface. In this review, methods to improve the DET rate for enhancement of enzymatic fuel cell performances are summarized, with a focus on the more recent works (past 10 years). Finally, progress on the application of DET-enabled EFC to some biomedical and implantable devices are reported.

Keywords: biocatalyst; direct electron transfer; enzymatic fuel cell; glucose oxidase; nanostructure.

Figure 1

Schematic of possible DET route between FAD-GDH and debundled SWNT. (A) and (B) show possible location of debundled SWNT in the indentation of FAD-GDH; (C) compares the locations of MWNT, graphene, and debundled SWNT with respect to the FAD-GDH; (D) visualizes the reduced distance for electrons to travel from the FAD cofactor to the debundled SWNT (Muguruma et al., 2017).

Figure 2

Schematic representing direct bioelectrocatalysis of pyrene-modified laccase immobilized by β-cyclodextrin-modified gold nanoparticles bound to carbon nanotube (Lalaoui et al., 2016b).

Figure 3

Schematic of proposed route of DET for GOx physisorbed with multi-walled carbon nanotubes (Liu et al., 2018) (https://pubs.acs.org/doi/full/10.1021/acsomega.7b01633. Further permissions related to the material should be directed to ACS).

Figure 4

Schematic of (A) fabrication of various GOx-functionalized electrodes and their mechanism of immobilization; (B) comparison between native GOx and GOx/PCA composite (Christwardana et al., 2017).

Figure 5

Schematic of five-enzyme cascade system for hydrolysis of cellulose and glucose oxidation. Adapted from Chen et al. (2017).

Figure 6

Schematics showing (A) curvature effect (B) edge effect (C) electrostatic effect that are taken into account for meso- and microporous structures (Sakai et al., 2018).

Figure 7

Schematic of enzymatic fuel cell using live snail. Figures are from work by Halámková et al. (2012).