title: Label-free and sequence-specific DNA detection down to a picomolar level with carbon nanotubes as support for probe DNA.
abstract: This study describes a simple and label-free electrochemical impedance spectroscopic (EIS) method for sequence-specific detection of DNA by using single-walled carbon nanotubes (SWNTs) as the support for probe DNA. SWNTs are confined onto gold electrodes with mixed self-assembly monolayers of thioethanol and cysteamine. Single-stranded DNA (ssDNA) probe is anchored onto the SWNT support through covalent binding between carboxyl groups at the nanotubes and amino groups at 5' ends of ssDNA. Hybridization of target DNA with the anchored probe DNA greatly increases the interfacial electron-transfer resistance (R(et)) at the double-stranded DNA (dsDNA)-modified electrodes for the redox couple of Fe(CN)(6)(3-/4-), which could be used for label-free and sequence-specific DNA detection. EIS results demonstrate that the utilization of SWNTs as the support for probe DNA substantially increases the surface loading of probe DNA onto electrode surface and thus remarkably lowers the detection limit for target DNA. Under the conditions employed here, R(et) is linear with the concentration of target DNA within a concentration range from 1 to 10 pM with a detection limit down to 0.8 pM (S/N=3). This study may offer a novel and label-free electrochemical approach to sensitive sequence-specific DNA detection.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Ningning
authors.initials: N
authors.lastname: Zhu
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Lin
authors.forename: Ping
authors.initials: P
authors.lastname: Yu
authors.forename: Lei
authors.initials: L
authors.lastname: Su
authors.forename: Lanqun
authors.initials: L
authors.lastname: Mao
mesh_terms: D004247:DNA / Q000032:analysis*; D015342:DNA Probes / Q000737:chemistry*; D004277:DNA, Single-Stranded / Q000737:chemistry; D017097:Electric Impedance; D055664:Electrochemical Techniques / Q000379:methods*; D004566:Electrodes; D006046:Gold / Q000737:chemistry; D037742:Nanotubes, Carbon / Q000737:chemistry*; D009693:Nucleic Acid Hybridization / Q000379:methods*
chemical_list: D015342:DNA Probes; D004277:DNA, Single-Stranded; D037742:Nanotubes, Carbon; D006046:Gold; D004247:DNA