Direct electron transfer chemistry of redox-active enzymes: applications in biosensor development

The direct electron transfer (DET) process, which does not require a mediator, is highly advantageous and holds significant potential for application in biosensors. Enzyme-based biosensors are simple, cost-efficient, and easy to use. This review highlights key enzymes with redox-active sites that are suitable for DET processes using various modified electrodes and their applications in biosensors. The review discusses enzyme classification, distinguishing between single-cofactor and multi-cofactor enzymes according to their number of prosthetic groups, with a focus on internal electron transfer processes and the role of redox-active centers. Methods for enzyme immobilization on electrodes are explored with an emphasis on their impact on electron transfer rates in biosensors. A comparison of sensitivity, electron transfer rates, and the linear detection range of molecules (e.g., glucose and lactose) is provided to illustrate the impact of different immobilization techniques on biosensor performance. © 2025 Society of Industrial Chemistry and John Wiley & Sons Ltd.