Electrochemical Fine-Tuning of the Chemoresponsiveness of Langmuir-Blodgett Graphene Oxide Films

Graphene oxide has been widely deployed in electricalsensors formonitoring physical, chemical, and biological processes. The presenceof abundant oxygen functional groups makes it an ideal substrate forintegrating biological functional units to assemblies. However, theintroduction of this type of defects on the surface of graphene hasa deleterious effect on its electrical properties. Therefore, adjustingthe surface chemistry of graphene oxide is of utmost relevance foraddressing the immobilization of biomolecules, while preserving itselectrochemical integrity. Herein, we describe the direct immobilizationof glucose oxidase onto graphene oxide-based electrodes prepared byLangmuir-Blodgett assembly. Electrochemical reduction of grapheneoxide allowed to control its surface chemistry and, by this, regulatethe nature and density of binding sites for the enzyme and the overallresponsiveness of the Langmuir-Blodgett biofilm. X-ray photoelectronspectroscopy, surface plasmon resonance, and electrochemical measurementswere used to characterize the compositional and functional featuresof these biointerfaces. Covalent binding between amine groups on glucoseoxidase and epoxy and carbonyl groups on the surface of graphene oxidewas successfully used to build up stable and active enzymatic assemblies.This approach constitutes a simple, quick, and efficient route tolocally address functional proteins at interfaces without the needfor additives or complex modifiers to direct the adsorption process.