title: Label-free cascade amplification strategy for sensitive visual detection of thrombin based on target-triggered hybridization chain reaction-mediated in situ generation of DNAzymes and Pt nanochains.
abstract: A new magnetic bead-based cascade amplification strategy for highly sensitive visual detection of proteins (thrombin as a model analyte) was developed by coupling target-triggered hybridization chain reaction (HCR) with the synergistic catalysis of DNA concatemer-mediated hemin/G-quadruplex DNAzymes and Pt nanozymes. Initially, the biotinylated primer DNA (P-DNA) was complementary with aptamer to form dsDNA which was further linked to streptavidin-coated magnetic bead (MB), thereby fabricating the expected MB-based aptasensor. In the presence of target TB, the aptamer was taken away from the aptasensor, and the free P-DNA immediately triggered HCR to spontaneously form DNA concatemer-directed nanochains with numerous DNAzymes and Pt nanoclusters (PtNCs) to achieve cascades signal amplification. The dual peroxidase mimetics catalyzed the H2O2-mediated oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) into the colored TMB oxides (oxTMB), causing intensified color change of the chromogenic solution for the highly sensitive naked-eye detection of as low as 100.0 pM TB. In this strategy, the employment of magnetic separation and exonuclease III (Exo III)-assisted digestion of residual dsDNA minimized the background noise and avoided the false positive results, greatly improving the detection accuracy and sensitivity with a low limit of detection (LOD=15.0 pM). The proposed visual platform has promise for detecting various types of proteins with careful DNA sequence designs.
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China; College of Chemistry and Pharmaceutical Engineering, Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, Sichuan University of Science and Engineering, Zigong 643000, PR China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China; College of Chemistry and Pharmaceutical Engineering, Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, Sichuan University of Science and Engineering, Zigong 643000, PR China.
authors.forename: Wang
authors.initials: W
authors.lastname: Ren
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China. Electronic address: luohq@swu.edu.cn.
authors.forename: Hong Qun
authors.initials: HQ
authors.lastname: Luo
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China. Electronic address: linb@swu.edu.cn.
authors.forename: Nian Bing
authors.initials: NB
authors.lastname: Li
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry; D015374:Biosensing Techniques; D021881:DNA, Catalytic / Q000737:chemistry; D054856:G-Quadruplexes; D006427:Hemin / Q000737:chemistry; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry; D021141:Nucleic Acid Amplification Techniques; D010984:Platinum / Q000737:chemistry; D013917:Thrombin / Q000302:isolation & purification*
chemical_list: D052157:Aptamers, Nucleotide; D021881:DNA, Catalytic; D010984:Platinum; D006427:Hemin; D006861:Hydrogen Peroxide; D013917:Thrombin
keywords: Aptasensor; Cascade amplification; DNAzymes; Pt nanochains; Visual detection