Lab-made fructose amperometric third-generation biosensors based on laser-patterned reduced graphene oxide films

In this presentation, a strategy to transfer laser-produced reduced graphene oxide (rGO) onto flexible polymers is proposed, proving for the first time its effectiveness for direct bioelectrocatalysis. Laser-patterned rGO films were transferred onto three flexible polymeric substrates (PET, PVC, and EVA) by a here-proposed strategy named “roll-to-roll thermal stamping”, taking advantage of a simple office-grade thermal laminator. The obtained films were compared with the native rGO (untransferred) via depth morpho-chemical and electrochemical characterizations. The rGO transferred onto plastic substrates presents morphology and chemical characteristics similar to native laser-produced rGO. Given these properties, the rGO-films were coupled to the enzyme fructose dehydrogenase (FDH) and their ability to give direct electron transfer (DET) has been carefully investigated. Particularly, the DET reaction between FDH and rGO-based transducers was investigated evaluating the influence of the enzyme unit amount on the catalytic process. The most performing DET-type biosensor was obtained by transferring rGO on PET, further modified with 15 mU of FDH. This biosensor demonstrated superior performance, thanks to its preserved rGO features and reduced capacitive current, proving reproducible (RSD = 3%, n=3) and competitive electro-analytical features (LOD = 0.2 µM) for the determination of D-fructose. Noteworthy, the enzyme units required to reach the highest catalytic currents resulted significantly lower (20-times less) compared to biosensors based on commercial electrodes, while the obtained performances resulted superior to the majority of FDH-biosensors. Eventually, the proposed biosensor was successfully used to monitor fructose evolution in bananas during post-harvest ripening (recoveries 109-90 %; RSD ≤ 7%, n= 3). This work demonstrates how laser-obtained rGO films can be transferred onto different flexible substrates using simple equipment, allowing the manufacturing of complete biosensors with fascinating features.