Methodologies for “Wiring” Redox Proteins/Enzymes to Electrode Surfaces

Abstract

The immobilization of redox proteins or enzymes onto conductive surfaces has application in the analysis of biological processes, the fabrication of biosensors, and in the development of green technologies and biochemical synthetic approaches. This review evaluates the methods through which redox proteins can be attached to electrode surfaces in a “wired” configuration, that is, one that facilitates direct electron transfer. The feasibility of simple electroactive adsorption onto a range of electrode surfaces is illustrated, with a highlight on the recent advances that have been achieved in biotechnological device construction using carbon materials and metal oxides. The covalent crosslinking strategies commonly used for the modification and biofunctionalization of electrode surfaces are also evaluated. Recent innovations in harnessing chemical biology methods for electrically wiring redox biology to surfaces are emphasized.

Efficiency of Site‐Specific Clicked Laccase–Carbon Nanotubes Biocathodes towards O2 Reduction

“…To gain control on the immobilization and wiring of MCOs, strategies involving a surface modification have been developed. Most reported attempts rely on a chemical modification of the surface of the electrode . For example, Armstrong and co‐workers have taken advantage of the hydrophobicity of several amino acids nearby the T1 copper center of a laccase from Trametes versicolor to obtain its self‐immobilization on a pyrolytic graphite electrode surface modified with polycyclic aromatics as substrate mimics .…”

“…Most reporteda ttempts rely on ac hemical modification of the surfaceo ft he electrode. [8,16] For example, Armstrong and co-workershave taken advantage of the hydrophobicity of several amino acids nearbyt he T1 copperc entero falaccase from Trametes versicolor to obtain its self-immobilizationo na pyrolytic graphite electrode surfacem odified with polycyclic aromatics as substrate mimics. [17,18] Similar strategies have been successfully exploited to immobilize enzymes at the surface of gold nanoparticles, carbon nanotubes (CNTs) and graphene sheets.…”

Recent Enzymatic Electrochemistry for Reductive Reactions

“…In order to couple an oxidoreductase enzyme with an electrode, however, aspects such as the stability and activity of the enzyme(s) within an electrochemical system must be considered. Perhaps the most pertinent design issue for enzymatic electrochemistry however, concerns the transfer of electrons between an electrode and an enzyme . More specifically, electron transfer between an enzyme's redox cofactor(s) and an electrode (or electron mediator) must be efficient.…”

“…However, considerable controversy surrounds DET of GOx and this has been dealt with extensively elsewhere . On the other hand, the multi‐copper oxidases laccase and bilirubin oxidase as well as hydrogenases (H 2 ases, among others) have been extensively studied by DET‐type enzymatic electrochemistry . Electrostatic orientation has often been utilized to aid in establishing DET, whereby regions of a proteins’ surface charges are analyzed from its X‐ray crystal structure and electrodes are subsequently modified to facilitate a charge‐specific orientation of the enzyme for DET (thereby minimizing expected electron transfer distances from an electrode to a cofactor(s)) .…”

“…Usually, the following described systems used additional semi‐conductor components to modify the electrodes which can mimic natural photosynthetic light‐harvesting pigments. N‐type metal oxide semiconductors such as TiO 2 (transparent) and indium tin oxide (ITO) have highly tunable porous structures and a negatively charged surface at neutral pH, therefore facilitating protein adsorption (depending on the isoelectric point of the protein, or localized areas of charge) . Examples have been reported using semiconductor based nanoparticles but in the limited examples cited here after, only systems using electrodes will be presented.…”