Early detection of Alzheimer's disease using a biosensor based on electrochemically-reduced graphene oxide and gold nanowires for the quantification of serum microRNA-137

Alzheimer's disease (AD) is the most common form of dementia, and its early detection using reliable molecular biomarkers is believed to be best approach to controlling and even curing it. Herein, we develop an ultrasensitive electrochemical nanobiosensor to quantify serum miR-137 as a validated biomarker of AD. Electrochemically-reduced graphene oxide (ERGO) and gold nanowires (AuNWs) are used to modify the surface of a screen-printed carbon electrode (SPCE) with the application of an intercalated label, doxorubicin (Dox). The fabrication steps are analysed via field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS), as well as two reliable electrochemical methods, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that the linear range of the nanobiosensor is from 5.0 to 750.0 fM and its limit of detection is 1.7 fM. In addition, the nanobiosensor shows a great performance in specificity experiments and is able to discriminate between target oligos versus non-specific oligos (one-base mismatch target; three-base mismatch target, non-specific miR-21 and miR-155) very well. The evaluation of the sensing mechanism of the developed nanobiosensor in actual human serum reveals its potential clinical applications for the early detection of AD in the future.