title: A cascade signal amplification strategy for sensitive and label-free DNA detection based on Exo III-catalyzed recycling coupled with rolling circle amplification.
abstract: A sensitive and label-free fluorescence assay for DNA detection has been developed based on cascade signal amplification combining exonuclease III (Exo III)-catalyzed recycling with rolling circle amplification. In this assay, probe DNA hybridized with template DNA was coupled onto magnetic nanoparticles to prepare a magnetic bead-probe (MNB-probe)-template complex. The complex could hybridize with the target DNA, which transformed the protruding 3' terminus of template DNA into a blunt end. Exo III could then digest template DNA, liberating the MNB-probe and target DNA. The intact target DNA then hybridized with other templates and released more MNB-probes. The liberated MNB-probe captured the primer, circular DNA and then initiated the rolling circle amplification (RCA) reaction, realizing a cascade signal amplification. Using this cascade amplification strategy, a sensitive DNA detection method was developed which was superior to many existing Exo III-based signal amplification methods. Moreover, N-methyl mesoporphyrin IX, which had a pronounced structural selectivity for the G-quadruplex, was used to combine with the G-quadruplex RCA products and generate a fluorescence signal, avoiding the need for any fluorophore-label probes. The spike and recovery experiments in a human serum sample indicated that our assay also had great potential for DNA detection in real biological samples.
authors.affiliation: Key Laboratory for Colloid and Interface Chemistry of Education Ministry, Department of Chemistry, Shandong University, Jinan, 250100, P. R. China. wjiang@sdu.edu.cn.
authors.forename: Xingti
authors.initials: X
authors.lastname: Liu
authors.forename: Qingwang
authors.initials: Q
authors.lastname: Xue
authors.forename: Yongshun
authors.initials: Y
authors.lastname: Ding
authors.forename: Jing
authors.initials: J
authors.lastname: Zhu
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
mesh_terms: D001483:Base Sequence; D002384:Catalysis; D004247:DNA / Q000032:analysis*; D005090:Exodeoxyribonucleases / Q000378:metabolism*; D054856:G-Quadruplexes; D013050:Spectrometry, Fluorescence
chemical_list: D004247:DNA; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III