Graphene oxide functionalization via epoxide ring opening in bioconjugation compatible conditions

•Graphene oxide fixation on glass beads helps to quantify the functional groups load.•Epoxy groups density in the graphene oxide structure was found to be as high as 1 nm−2.•Graphene oxide epoxy groups are stable in its colloidal aqueous solution for months.•Graphene oxide epoxy groups react with amines in biocompatible conditions.•Epoxy-driven amine-GO adducts survive under hydrazine reduction.