Graphene-based enzyme-modified field-effect transistor biosensor for monitoring drug effects in Alzheimer's disease treatment

A reduced graphene oxide-based enzyme-modified field-effect transistor (RGO-EnFET) was fabricated to study the enzymatic kinetics between acetylcholinesterase (AChE) and acetylcholine (ACh), which are related to the progression and treatment of Alzheimer's disease (AD). The RGO-EnFET exhibited typical ambipolar transfer characteristics with a charge neutrality point (the Dirac point, VDirac) in an aqueous environment, and biological events occurring on the RGO surface were evaluated by observing the Dirac point shift (ΔVDirac) according to reactions. First, the pH sensitivity of the RGO-EnFET was measured to be 24.12 mV pH−1 for a pH range of 4-10 with excellent repeatability. Then, ACh quantification in the concentration range of 1 μM-10 mM was evaluated, with a linear slope of 13.9 mV dec−1 being obtained between ΔVDirac and the ACh concentration on a logarithmic scale. The effects of AChE inhibitors (donepezil and rivastigmine) on the AChE enzymatic activity were also investigated. The distinguishable inhibition rates were acquired for donepezil and rivastigmine at saturation levels of 90% and 75%, respectively. These results indicate that the RGO-EnFET biosensor was successfully exploited as an in vitro analytical tool and has potential of future application in the study of enzymatic kinetics and drug screening for therapeutic purposes.