Enzyme-Based Biosensors: Tackling Electron Transfer Issues

Abstract

This review summarizes the fundamentals of the phenomenon of electron transfer (ET) reactions occurring in redox enzymes that were widely employed for the development of electroanalytical devices, like biosensors, and enzymatic fuel cells (EFCs). A brief introduction on the ET observed in proteins/enzymes and its paradigms (e.g., classification of ET mechanisms, maximal distance at which is observed direct electron transfer, etc.) are given. Moreover, the theoretical aspects related to direct electron transfer (DET) are resumed as a guideline for newcomers to the field. Snapshots on the ET theory formulated by Rudolph A. Marcus and on the mathematical model used to calculate the ET rate constant formulated by Laviron are provided. Particular attention is devoted to the case of glucose oxidase (GOx) that has been erroneously classified as an enzyme able to transfer electrons directly. Thereafter, all tools available to investigate ET issues are reported addressing the discussions toward the development of new methodology to tackle ET issues. In conclusion, the trends toward upcoming practical applications are suggested as well as some directions in fundamental studies of bioelectrochemistry.

MXenes-Based Bioanalytical Sensors: Design, Characterization, and Applications

“…Despite progress, enzymes can lose their bioactivity when directly immobilized onto electrode surfaces. Moreover, due to the deeply rooted location of redox-active centers in enzymes, the direct electron transfer (DET) between these biomolecules and the electrode surface is generally difficult and has been the subject of extensive investigations as reviewed in a recent work [ 65 ]. Therefore, the use of nanomaterials has been found beneficial to facilitate the electron transfer along with promoting retention of the bioactivity of immobilized enzymes.…”

Development Perspective of Bioelectrocatalysis-Based Biosensors

“…Thus, DET-type bioelectrocatalysis is often improved by using mesoporous electrode materials on which enzymes adsorb in increased probability of orientations favorable for DET-type reactions. Suitable modification of the electrode surface with chemical substances leads to electrostatic or specific attractive interaction between the electrode surface and the enzyme surface close to the electrode-active site [ 14 , 30 ].…”

“…The coupling of redox enzymatic reactions with electrochemical reactions has received worldwide medical and scientific interests [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. The coupled reaction is called bioelectrocatalysis.…”

“…On the other hand, it is known that some metal-containing enzymes and flavoenzymes can directly exchange electrons with electrodes in the absence of any mediators in the catalytic reaction. Such reactions are referred to as direct electron transfer (DET)-type bioelectrocatalysis [ 14 , 27 , 28 , 29 , 30 , 31 ]. In theory, DET-type bioelectrocatalysis can simplify the fabrication process of bioelectrodes and can minimize the thermodynamic overpotential in a coupled reaction.…”

Development Perspective of Bioelectrocatalysis-based Biosensors

“…The coupling of redox enzymatic reactions with electrochemical reactions has received worldwide medical and scientific interests [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The coupled reaction is called bioelectrocatalysis.…”