A Microfluidic-Channel Regulated, Electrolyte-Gated Graphene FET Biosensor Array for Repeatable and Recalibrated Detection of Thrombin

Abstract

Field-effect graphene biosensors have in general relied on irreversible surface modification for the detection of biological entities. However, restoring a sensor to a pre-sensing-event state is highly desirable in securing sensor data integrity, especially in the case of an electrolyte-gated graphene FET which is prone to drift and degradation. We present a graphene FET biosensor array that mimics an SPR(surface plasmon resonance) system in its use of a microfluidic channel for restoration of the sensor equilibrium. A steady flow of PBS through a 20-micron wide channel provides calibration for FET conductance before and after introducing human Thrombin to the base flow, successfully isolating the protein-induced field-effect from permanent changes made to the graphene device. Graphene conductance shows exponential saturation and de-saturation curves as governed by the the Nernst Equation. The sensors show a sub-microMolar limit-of-detection which can be dynamically tuned by the flow rate. Sensor specificity is provided by electrophoretic functionalization of DNA aptamers onto the graphene surface. We confirm successful aptamer functionalization with fluorescence microscopy, amperometry, and scanning electron microscopy. The current method of sensor state restoration adds reliability to biosensor data without the necessity of a matching-device control group and also maximizes manufacturing efficiency through device recycling.