Supramolecular electrode assemblies for bioelectrochemistry

Abstract

For more than three decades, the field of bioelectrochemistry has provided novel insights into the catalytic mechanisms of enzymes, the principles that govern biological electron transfer, and has elucidated the basic principles for bioelectrocatalytic systems. Progress in biochemistry, bionanotechnology, and our ever increasing ability to control the chemistry and structure of electrode surfaces has enabled the study of ever more complex systems with bioelectrochemistry. This feature article highlights developments over the last decade, where supramolecular approaches have been employed to develop electrode assemblies that increase enzyme loading on the electrode or create more biocompatible environments for membrane enzymes. Two approaches are particularly highlighted: the use of layer-by-layer assembly, and the modification of electrodes with planar lipid membranes.

Fig. 1. Schematic representation of three layer-by-layer assemblies in bioelectrochemistry. (A) Layer-by-layer assemblies of polyanions and a positively charged redox protein. (B) Layer-by-layer assemblies of a cationic amphiphile forming bilayers and positively charged redox proteins. (C) Layer-by-layer assemblies of negatively charged nanoparticles and positively charged redox proteins. Although examples are given for positively charged redox proteins (i.e., systems where the pH < pI of the protein), similar assemblies can be proposed where the charges are reversed.

Fig. 2. (A) Schematic representation of the glucose responsive supramolecular assembly that consists of redox-active ConA, horseradish peroxidase (HRP), ConA, dextran and glucose oxidase (GOx). (B-a) Simplified schematic representation for the data shown in this panel. (B-b) Chronoamperometry with increasing amounts of glucose. (B-c) Bioelectrocatalytic currents as a function of glucose concentration on this assembly with dextran (orange symbols) and without dextran (blue symbols). Reproduced as a composite from ref. 45 with permission from The Royal Society of Chemistry.

Fig. 3. Schematic representations of the four basic membrane-modified electrodes in bioelectrochemistry. A redox-active integral membrane protein is graphically depicted as a rectangular box, with the redox-active cofactors as circles over filled black lines within the box: (A) a hybrid bilayer lipid membrane (hBLM); (B) a solid supported bilayer lipid membrane (sBLM); (C) a tethered bilayer lipid membrane (tBLM); and (D) a protein-tethered bilayer lipid membrane (ptBLM).

Fig. 4. (A) Schematic representation of the [NiFeSe]-hydrogenase/F₁F₀-ATPase supramolecular ptBLM assembly on a gold electrode. (B) Cyclic voltammograms at a scan rate of 10 mV s^–1 of the [NiFeSe]-hydrogenase/F₁F₀-ATPase ptBLM before (under N₂) and after activation (under H₂) of the [NiFeSe]-hydrogenase. (C) ATP production at 150 mV vs. SCE and 1 atm of H₂ of a ptBLM that contained either both enzymes (black solid circles), only [NiFeSe]-hydrogenase (Hase; grey open circles), or only F₁F₀-ATPase (ATPase; grey solid circles). Reproduced as a composite from ref. 60.

Fig. 5. (A) Schematic representation of the electron transport chain metabolon incorporated in a tethered lipid bilayer membrane on a gold electrode. (B) Cyclic voltammograms at a scan rate of 5 mV s^–1 of the metabolon with oxidised cytochrome c (solid line); complex IV electrodes with reduced cytochrome c (dotted line); and only cytochrome c containing control bilayers (dash-dotted line). (C) Cyclic voltammograms at a scan rate of 5 mV s^–1 of the metabolon with increasing amounts of oxidised cytochrome c (0–5 μM). Reproduced as a composite with permission from ref. 70. Copyright 2016 American Chemical Society.

Theodoros Laftsoglou (left) and Dr Lars Jeuken (right)