Inkjet-Printed Liquid Gated Graphene Field Effect Transistor for the Detection of Interleukin-6

Interleukin-6 (IL-6) is an inflammatory cytokine that serves as an important prognostic biomarker for chronic diseases such as cancer and coronavirus disease. Label-free sensors that can conveniently detect IL-6 are essential for health monitoring purposes. Here, we present an aptamer-modified liquid-gated graphene field effect transistor (GFET) biosensor fabricated using inkjet printing techniques that can detect IL-6 levels. In this work, graphene ink suitable for inkjet printing was synthesized and formulated using the ultrasonic liquid exfoliation method. Exfoliated graphene was redispersed into a cyclohexanone/terpineol solvent system and optimized to achieve jettable ink with a Z-number of 13.7. The formulated graphene ink was then used to fabricate the GFET device, which in turn was decorated with IL-6 aptamer using organic linkers. The sensor response of the GFET was measured using the shift in the transistor current-voltage (I-V) transfer curves upon specific binding of the IL-6 with the aptameric GFET. The experimental results showed that the device can sensitively and selectively detect IL-6 in a 1xPBS background with a limit of detection of 372 pM. The fabricated GFET is on a flexible substrate that may be suitably incorporated into a face mask covering that could potentially sample IL-6 from collected saliva.