▎ 摘　　要

The detection of methylation level in O-6-methylguanine-DNA methyltransferase (MGMT) gene is of great significance for diagnosis, prognosis and treatment of glioblastoma. Herein, we proposed an electrochemical immunosensor for detection of MGMT gene methylation. Graphene oxide-magnetic nanoparticles-beta-cyclodextrin (GO-Fe3O4-beta-CD) nanocomposite was covered on electrode, and then anti-5-methylcytosine (5mC) antibody was immobilized on modified electrode via host-guest interaction with beta-CD. The immobilized antibody specifically recognized and directly captured 5mC on DNA containing MGMT promoter sequence (MGMT-DNA). The methylation level in MGMT-DNA could be evaluated using Ru(NH3)(6)(3+) as an electrochemical signal indicator. The redox recycling of Ru(NH3)(6)(3+) was triggered by Fe(CN)(6)(3-) and further amplified current response. A detection limit as low as 0.0825 pM was obtained. Finally, this electrochemical method was successfully applied to analysis of methylated MGMT-DNA in biological sample and detection of other methylation modifications, such as N6-methyladenosine in RNA.