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

•A new electrochemical immunosensor was developed for MGMT gene methylation.•Antibodies have dual functions of both specific recognition and direct capture of target DNA.•The method has good sensitivity with a LOD of 0.0825 pM because of the redox recycling of Ru(NH3)63+.•The method can also be adjusted for detection of other methylation modifications, such as N6-methyladenosine in RNA.