Electrochemical DNA biosensor with chitosan-Co3O4 nanorod-graphene composite for the sensitive detection of staphylococcus aureus nuc gene sequence

In this paper a novel nanocomposite material prepared by Co3O4 nanorods (nano-Co3O4), graphene (GR) and chitosan (CTS) was fabricated and further modified on carbon ionic liquid electrode (CILE), which was used as the substrate electrode to construct a new electrochemical DNA biosensor. The single-stranded DNA (ssDNA) probe was immobilized on the CTS-Co3O4-GR/CILE surface by electrostatic attraction, which could hybridize with the target ssDNA sequence under the selected conditions. By using methylene blue (MB) as the electrochemical indicator, the hybridization reactions were monitored with the reduction peak current. By combining the biocompatibility of Co3O4 nanorods, excellent electron transfer ability and big surface of GR, good film-forming ability of CTS and the high conductivity of CILE, the amount of ssDNA adsorbed on the electrode surface was increased and the electrochemical response of MB was accelerated. Under the optimal conditions differential pulse voltammetric responses of MB were in linear with the specific target ssDNA sequence in the concentration range from 1.0 x 10(-12) to 1.0 x 10(-6) M with the detection limit as 4.3 x 10(-13) M (3 sigma). Good discrimination ability to the one-base and three-base mismatched ssDNA sequences could be achieved and the polymerase chain reaction (PCR) amplification products of Staphylococcus aureus nuc gene sequence were detected with satisfactory results. (C) 2012 Elsevier B.V. All rights reserved.