Single-walled carbon nanotubes-carboxyl-functionalized graphene oxide-based electrochemical DNA biosensor for thermolabile hemolysin gene detection

A sensitive electrochemical DNA biosensor, based on carboxyl-functionalized graphene oxide (CFGO), a single-walled carbon nanotubes (SWCNTs) sensing platform and differential pulse voltammetry (DPV) detection, was constructed in this study. CFGO was prepared via a ring-opening reaction catalyzed by hydrobromic acid and an esterification reaction with oxalic acid, and used as a mediator for probe DNA (pDNA) immobilization. DNA labeled at 5'-end using amino (NH2-pDNA) was immobilized on the electrode surface through covalent interaction between amino and carboxyl groups on CFGO. Moreover, single-walled carbon nanotubes (SWCNTs) were employed to improve the electrochemical performance of the biosensor. Based on the different electrochemical responses of [Fe(CN)(6)](3-/4-) toward pDNA versus double-stranded DNA after hybridization, the thermolabile hemolysin gene sequence could be detected in a concentration range from 1 x 10(-6) to 1 x 10(-13) mol L-1 with a low detection limit of 7.21 x 10(-14) mol L-1 (at a signal-to-noise ratio of 3). Furthermore, the biosensor also displayed high selectivity for the differentiation of DNA oligonucleotides from one-base mismatch to noncomplementary. All the reasonable electrochemical performance of the proposed sensing platform indicated that it could be used for the sensitive and accurate determination of other nucleic acids.