title: Fluorescence aptameric sensor for strand displacement amplification detection of cocaine.
abstract: A new fluorescence method based on aptamer-target interactions has been developed for cocaine detection with target-induced strand displacement. Here we describe new probes, the hairpin-probe and the single strand-probe (ss-probe), that possess two recognition sequences of cocaine aptamer. In the presence of cocaine, both probes would associate with the target to form a tripartite complex. The conformational change in the hairpin-probe causes the opening of a hairpin structure and the hybridization to primer. With polymerase and the dNTPs, the replication of the single-stranded domain of hairpin-probe triggers the process of primer extension. When the hairpin-probe is converted into a fully double-stranded form, the ss-probe and cocaine are displaced to bind another hairpin-probe and initiate new amplification cycles. Fluorescence signal generation would be observed upon SYBR Green I intercalating into the new DNA double helix. The new protocol design permits detection of as low as 2 nM cocaine in a closed tube, offering a convenient approach for a homogeneous assay. Compared with previously reported cocaine aptameric sensors, our new method is highly sensitive, selective, and economical.
authors.affiliation: State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, P. R. China.
authors.forename: Jing-Lin
authors.initials: JL
authors.lastname: He
authors.forename: Zai-Sheng
authors.initials: ZS
authors.lastname: Wu
authors.forename: Hui
authors.initials: H
authors.lastname: Zhou
authors.forename: Hong-Qi
authors.initials: HQ
authors.lastname: Wang
authors.forename: Jian-Hui
authors.initials: JH
authors.lastname: Jiang
authors.forename: Guo-Li
authors.initials: GL
authors.lastname: Shen
authors.forename: Ru-Qin
authors.initials: RQ
authors.lastname: Yu
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D015374:Biosensing Techniques / Q000379:methods*; D003042:Cocaine / Q000032:analysis* / Q000737:chemistry; D017931:DNA Primers / Q000235:genetics; D015342:DNA Probes / Q000737:chemistry / Q000235:genetics; D004261:DNA Replication; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000235:genetics; D004586:Electrophoresis; D006801:Humans; D055029:Inverted Repeat Sequences; D008969:Molecular Sequence Data; D021141:Nucleic Acid Amplification Techniques; D013050:Spectrometry, Fluorescence; D013997:Time Factors
chemical_list: D052157:Aptamers, Nucleotide; D017931:DNA Primers; D015342:DNA Probes; D004277:DNA, Single-Stranded; D003042:Cocaine