▎ 摘　　要

In the present study, the voltammetric and impidimetric detection of microRNA-21, mir-21 from cell lysates was investigated for the first time by using graphene modified disposable pencil graphite electrodes (GME). The surface characterization of GME was performed via electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Upon passive adsorption of inosine substituted antimicroRNA-21, antimir-21 probe, InP, onto the surface of GME and then solid phase hybridization of InP with mir-21, the target, the electrochemical detection was performed by using Differential Pulse Voltammetry (DPV) and EIS techniques. This developed biosensor, GME has presented a 2.77 times lower detection limit of 2.09 mg/mL (3.12 pmol) with respect to unmodified pencil graphite electrode (GE). Moreover it is capable of analyzing mir-21 in the cell lysates of mir-21 positive breast cancer cell line (MCF-7) contrast to mir-21 negative hepatoma cell line (HUH-7). The proposed electrochemical yes-no system does not require any purification and/or amplification step prior to fast detection of mir-21 from real samples.