Electrochemical sensing of glucose by chitosan modified graphene oxide

Graphene oxide (GO) coated electrodes provide an excellent platform for enzymatic glucose sensing, induced by the presence of glucose oxidase and an electrochemical transduction. Here, we show that the sensitivity ofGOlayers for glucose detection redoubles upon blendingGOwith chitosan (GO +Ch) and increases up to eight times if covalent binding of chitosan toGO(GO−Ch) is exploited. In addition, the conductivity of the composite materialGO−Ch is suitable for electrochemical applications without the need ofGOreduction, which is generally required forGObased coatings. Covalent modification ofGOis achieved by a standard carboxylic activation/amidation approach by exploiting the abundant amino pendants of chitosan. Successful functionalization is proved by comparison with an ad-hoc synthesized control sample realized by using non-activatedGOas precursor. The compositeGO−Ch was deposited on standard screen-printed electrodes by a dropcasting approach. Comparison with a chitosan-GO blend and with pristineGOdemonstrated the superior reliability and efficiency of the electrochemical response for glucose as a consequence of the high number of enzyme binding sites and of the partial reduction ofGOduring the carboxylic activation synthetic step.