Silk fibroin hydrogel encapsulated graphene filed-effect transistors as enzyme-based biosensors

Graphene field-effect transistor (GFET) is a useful device which could be designed as an ultrasensitive and high-throughput biosensor in biological sensing. However, bioprobes like enzymes are easy to lose activity after immobilizing on the graphene. In addition, measurement of biomarkers in aqueous solutions with high ionic concentration and multiple interfering components is still a challenge. Here, the enzymatic cross-linked silk fibroin (SF) hydrogel is selected as a carrier for glucose oxidase and horseradish peroxidase to encapsulate GFET biosensor functionally, in order to detect glucose in a physiological buffer solution. The SF hydrogel showed the effects of prolonging the lifetime of these enzymes and enabled the reduction of nonspecific adsorption of the GFET. The SF hydrogel encapsulated GFET exhibited high sensitivity for glucose sensing with a wide detection range of 1 mu M to 10 mM and a limit of detection (LOD) down 200 nM, as well as a high specificity over other carbohydrates such as sucrose and trehalose. Moreover, the biosensor has exhibited renewability, which main-tained a consistent sensing response after 10 times of regenerative cycles, with a variation less than 4.9%. These results demonstrate that the strategy for encapsulating GFET using the SF hydrogel is valid, suggesting the potential application of the SF hydrogel in biosensors.