Roll-to-roll thermal stamped laser-patterned rGO-films integrated into lab-made 3rd generation fructose biosensors with enhanced electron transfer efficiency

Laser photo-thermal reduction is a straightforward approach to form nanostructured conductive patterns with micrometric resolution, however, laser-induced nanomaterial formation needs solid support, which unfortunately limits the integration into more sophisticated biosensors. To the best of our knowledge, laser-produced conductive films have not been studied for direct electron transfer(DET)-based bioelectronics, despite their nanostructure and remarkable charge-transfer ability may suggest a huge potential for electrocatalysis-based applications. Herein, an easy approach to stamp conductive laser-produced reduced graphene oxide (rGO) films onto flexible polymeric substrates has been proposed, proving for the first time its effectiveness for direct bioelectrocatalysis; the strategy was named roll-to-roll thermal stamping. This straightforward, scalable, and low-cost approach allows to overcome the limits of the integration of laser-induced rGO-films in bioanalytical devices. Laser-produced rGO has been thermal-stamped (TS) onto different polymeric substrates (PET, PVC, and EVA) using a simple roll-laminator; TS-rGO films reveal how stamping changes the rGO native nature and the employed support affects the film features. Particular effort was also devoted to the investigation of TS-rGO sensors' DET-ability using fructose dehydrogenase (FDH) as model enzyme; DET-reaction between FDH and TS-rGO transducers has been investigated concerning the influence of the enzyme amount on the catalytic process. TS-rGOs were able to facilitate DET-reaction, showing enhanced (bio)electrocatalytic features. Among substrates, PET has emerged as the elective one to fabricate TS-rGO biosensors. TS-rGOPET demonstrated superior performance, thanks to its preserved rGO features and reduced capacitive current induced by the transferring process, with reproducible (RSD = 3%, n=3) and sensitive electro-analytical features (LOD = 0.2 µM) for the determination of D-fructose. Noteworthy, TS-rGOs-based biosensors allow relevant electrocatalysis using significantly lower FDH amount (15 mU) with respect to commercial electrodes. Eventually, TS-rGO-based 3rd generation complete enzymatic biosensors were fabricated via low-cost benchtop technologies and TS-rGOPET was successfully employed for the monitoring of D-fructose during banana fruit storage (Recoveries 110-90%, n=3), demonstrating its applicability as a point-of-need for food control (Relative Error -13/+1%), resulting an effective alternative, to the expensive, cumbersome, and slow colorimetric/fluorimetric kits for the determination of fructose. Summing up, an easy strategy to generate controlled and effective films of laser-induced graphene onto polymeric substrates is proposed, this approach needs just a simple roll laminator and allows enhancement of the electro-catalytic features of the native material, proving great potentiality for the development of efficient on-demand flexible (bio)electronics.