Enzymatic Biosensors Based on the Electrochemical Functionalization of Graphene Field-Effect Transistors with Conducting Polymers

Abstract

This chapter discusses the utilization of conducting polymer films based on poly(3-amino-benzylamine-co-aniline) (PABA) as platforms for creating enzymatic graphene field-effect transistor (GFET) biosensors. The electropolymerization of PABA films onto graphene transistors allows a precise control of the film nature and thickness. The chemical richness of the PABA films improves the pH response of the transistors, making them suitable for biosensing applications. In addition, enzymes such as acetylcholinesterase (AchE) and glucose oxidase (GOx) can be successfully immobilized on the PABA-modified surfaces without compromising their functionality, and the amount of immobilized enzyme can be quantified using surface plasmon resonance (SPR) measurements. The AchE-PABA-modified GFETs exhibit a shift in the Dirac point in response to acetylcholine (Ach) hydrolysis, allowing real-time sensing of Ach in a flow configuration with excellent selectivity, fast response time, and good reproducibility. The GOx-PABA-modified GFETs allow the real-time sensing of glucose with a wide detection range and low limit of detection (LOD). The developed biosensors exhibit superior performance compared to previous GFET-based sensors, with the ability to operate at small gate-source and drain-source potentials and endowing the detection of both analytes in diluted urine samples. These examples show that the electropolymerization of PABA films allows the precise tuning of GFET surface features, making it a promising approach for the fabrication of highly sensitive biosensing devices with potential for the further integration of enzymes, biorecognition elements, or nanomaterials.