THERMAL STAMPING OF LASER-REDUCED GRAPHENE OXIDE FOR DIRECT ELECTRON TRANSFER-TYPE BIOSENSORS

Direct electron transfer (DET) of dehydrogenase enzymes has attracted increasing attention in pure and applied bioelectrochemistry over the last decades. One of the most fascinating features of some dehydrogenases is their ability to interact with rationally nanostructured surfaces, resulting in the boosting of DET-event, without the needing for mediators, spacers, and cross-linkers. In this presentation, the DET-ability of Fructose Dehydrogenase (FDH) has been studied toward photo-reduced graphene oxide (rGO) transferred with a new smart approach onto different flexible supports. In detail, graphene oxide (GO) has been photo-reduced with a CO2 laser plotter, obtaining rGO transferable conductive nanostructured films. The rGO films were transferred onto three flexible substrates i.e. PET-EVA, PET, and PVC, by a here proposed “roll-to-roll thermal stamping” strategy, taking advantage of a simple office-grade thermal laminator. Initially, the electrochemical performances of the rGO-based surface have been deeply studied, and then, their ability to give DET with FDH has been carefully investigated using different concentrations of enzyme. To this aim, dose-response curves of FDH-rGO electrodes have been investigated in the presence of increasing amounts of FRU, ranging from 1 μM to 60 mM, via amperometry (+0.25 V). All the electrodes resulted able to give DET significantly superior to commercial transducers; the most fascinating finding was that, using lower enzyme amounts, the biocatalytic event resulted significantly boosted. The most performing DET-type biosensor was obtained by transferring rGO on PET, further modified with 15 mU of FDH; this biosensor returned excellent sensitivity (LOD = 0.25 μM) and reproducibility (RSD ≤ 4%, n= 3) for the fructose bioanalysis. Noteworthly, the used enzyme units are singifincantly lower (20-time less) compared to the commonly used in literature, while the obtained perfomances resulted superior to the majority of FDH-biosensors. Finally, the rGO-PET biosensor was tested to monitor the fructose evolution in bananas (Musa acuminata) during post-harvest ripening; satisfactory recoveries were achieved (109.5-90.3%, RSD < 7%, n= 3), and the selectivity was proved against several potential interfering species. Summing up, this work demonstrates how laser-obtained rGO can be transferred onto flexible substrates using a simple office machine, allowing to construct DET-type biosensors with unique and fascinating features.