Graphene-based field effect transistor enzymatic glucose biosensor using silk protein for enzyme immobilization and device substrate

A silk fibroin-encapsulated graphene field effect transistor (FET) enzymatic biosensor that utilizes silk protein as both device substrate and enzyme immobilization material was developed for glucose detection. This biosensor detected glucose levels by measuring the differential drain-source current and the Dirac point shift of the graphene transistor as the glucose is oxidized by glucose oxidase that was immobilized in silk fibroin film on the graphene FET. The fabricated biosensors showed 0.1-10 mM large linear detection range, which covers the reference range of medical examination for diabetes diagnostics. The detection limit of the fabricated biosensors was approximately 0.1 mM (S/N = 3) with excellent selectivity, and the average sensitivity was 2.5 μA/mM measured at V_ds = 100 mV and V_g = 0 V. Because this fibroin-encapsulated graphene FET enzymatic biosensor is biocompatible, flexible, and long-term stable, it holds a great promise for portable, wearable, and implantable continuous glucose monitoring applications.