Novel electrochemical immunosensor for O6-methylguanine-DNA methyltransferase gene methylation based on graphene oxide-magnetic nanoparticles-β-cyclodextrin nanocomposite

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-β-cyclodextrin (GO-Fe 3 O 4 -β-CD) nanocomposite was covered on electrode, and then anti-5-methylcytosine (5mC) antibody was immobilized on modified electrode via host–guest interaction with β-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(NH 3 ) 6 3+ as an electrochemical signal indicator. The redox recycling of Ru(NH 3 ) 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.