Electrografted Interfaces on Metal Oxide Electrodes for Enzyme Immobilization and Bioelectrocatalysis

In this work, we demonstrate that diazonium electrografting of biocompatible interfaces on transparent conducting oxide indium tin oxide (ITO) can be controlled and optimized to achieve low charge transfer resistance, allowing highly efficient electron transfer to an immobilized model enzyme, the oxygen-tolerant [NiFe]-hydrogenase from Ralstonia eutropha. The use of a radical scavenger enables control of the interface thickness, and thus facilitates maximization of direct electron transfer processes between the enzyme's active center and the electrode. Using this approach, amine and carboxylic acid functionalities were grafted on ITO, allowing enzyme immobilization both under moderate electrostatic control and covalently via amide bond formation. Despite an initial decrease in catalytic activity, covalent immobilization led to an improvement in current stability compared to just electrostatically immobilized enzyme. Given the superior stability of electrografted interfaces in comparison to adsorbed or self-assembled interfaces, we propose electrografting as an alternative approach for the functional immobilization of redox-active enzymes on transparent conducting oxide (TCO) electrodes in bioelectronic devices.

Automated summary

This work demonstrates the control and optimization of biocompatible interfaces on transparent conducting oxide indium tin oxide (ITO) using diazonium electrografting to achieve low charge transfer resistance and efficient electron transfer to immobilized enzymes. Radical scavenger enables interface thickness control, maximizing direct electron transfer processes. Electrografting is proposed as an alternative approach for the functional immobilization of redox-active enzymes on TCO electrodes.