title: A label-free aptasensor for the sensitive and specific detection of cocaine using supramolecular aptamer fragments/target complex by electrochemical impedance spectroscopy.
abstract: A simple and label-free aptasensor for sensitive and specific detection of cocaine was developed by measuring the change in electrochemical impedance spectra (EIS), based on the formation of a supramolecular aptamer fragments/substrate complex. An anticocaine aptamer was divided into two fragments, Cx and Cy. Three different sensing interfaces, called Au/Cx5S/MCE, Au/Cy3S/MCE and Au/Cy5S/MCE, were fabricated by immobilizing Cx or Cy on a gold electrode through modifying their 5' or 3' end with a thiolated group followed by the treatment with mercaptoethanol (MCE). The formation of the corresponding supramolecular aptamer fragments/cocaine complex was investigated via monitoring electrochemical impedance spectra in the presence of [Fe(CN)(6)](3-/4-). The interfacial electron transfer resistance (R(et)) was found to depend strongly on the cocaine concentration. Since the supramolecular aptamer fragments/cocaine complex was formed on the electrode surface, the sensing interface strongly affected the sensitivity of the aptasensor. Au/Cx5S/MCE was shown to have good sensitivity within a cocaine detection range of 0.1-20 μM. Moreover, MCE was shown to improve the sensitivity of the aptasensor greatly. Even without the help of amplification or labeling, cocaine concentrations as low as 100 nM could be easily detected by the impedimetric aptasensor developed. The specificity and regeneration of the cocaine aptasensor were also investigated and satisfactory results were obtained. The developed aptasensor was successfully applied to detect the cocaine in biological fluids.
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Biochemistry and Molecular Engineering, College of Chemistry, Peking University, Beijing 100871, China.
authors.forename: De-Wen
authors.initials: DW
authors.lastname: Zhang
authors.forename: Fang-Ting
authors.initials: FT
authors.lastname: Zhang
authors.forename: Yi-Ran
authors.initials: YR
authors.lastname: Cui
authors.forename: Qin-Pei
authors.initials: QP
authors.lastname: Deng
authors.forename: Steffi
authors.initials: S
authors.lastname: Krause
authors.forename: Ying-Lin
authors.initials: YL
authors.lastname: Zhou
authors.forename: Xin-Xiang
authors.initials: XX
authors.lastname: Zhang
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry*; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D003042:Cocaine / Q000097:blood*; D058266:Dielectric Spectroscopy; D004566:Electrodes; D017743:Equipment Reuse; D005292:Ferricyanides / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D008623:Mercaptoethanol / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry; D012680:Sensitivity and Specificity
chemical_list: D052157:Aptamers, Nucleotide; D005292:Ferricyanides; D008623:Mercaptoethanol; D006046:Gold; D003042:Cocaine