A biofunctionalized graphene nanohybrid was prepared by simultaneously sonicating graphene and riboflavin 5'-monophosphate sodium salt (FMNS). FMNS, as a biodispersant, showed an efficient stabilization for obtaining highly dispersed graphene nanosheets in an aqueous solution. Due to the superior dispersion of graphene and the excellent electrochemical redox activity of FMNS, a direct electrochemical DNA sensor was fabricated by adopting the inherent electrochemical redox activity of graphene-FMNS (Gr-FMNS). The comparison between using traditional electrochemical indicator ([Fe(CN)6]3-/4-) and using the self-signal of Gr-FMNS was fully conducted to study the DNA-sensing performance. The results indicate that the proposed DNA-sensing platform displays fine selectivity, high sensitivity, good stability, and reproducibility using either [Fe(CN)6]3-/4- probe or the self-signal of Gr-FMNS. The two methods display the same level of detection limit: 7.4 × 10-17 M (using [Fe(CN)6]3-/4-) and 8.3 × 10-17 M (using self-signal), respectively, and the latter exhibits higher sensitivity. Furthermore, the sensing platform also can be applied for the DNA determination in real samples.
Keywords: DNA sensing; flavin mononucleotide; graphene; graphene aqueous dispersion; self-signal.