Abstract
A fluorometric method is described for nucleic acid signal amplification through target-induced catalytic hairpin assembly with DNA-templated copper nanoparticles (Cu NPs). The toehold-mediated self-assembly of three metastable hairpins is triggered in presence of target DNA. This leads to the formation of a three-way junction structure with protruding mononucleotides at the 3' terminus. The target DNA is released from the formed branched structure and triggers another assembly cycle. As a result, plenty of branched DNA becomes available for the synthesis of Cu NPs which have fluorescence excitation/emission maxima at 340/590nm. At the same time, the branched structure protects the Cu NPs from digestion by exonuclease III. The unreacted hairpins are digested by exonuclease III, and this warrants a lower background signal. The method can detect ssDNA (24nt) at low concentration (44 pM) and is selective over single-nucleotide polymorphism. On addition of an aptamer, the strategy can also beapplied to the quantitation of thrombin at levels as low as 0.9nM. Graphical abstractSchematic representation of target-induced catalytic hairpin assembly to form branched DNA template for the in situ synthesis of fluorescent Cu nanoparticles.
Published Version
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