Amplified Detection of
DNA through the Enzyme-Free
Autonomous Assembly of Hemin/G-Quadruplex DNAzyme Nanowires
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Abstract
An enzyme-free amplified detection platform is described
using
the horseradish peroxidase (HRP)-mimicking DNAzyme as an amplifying
label. Two hairpin structures that include three-fourths and one-fourth
of the HRP-mimicking DNAzyme in caged, inactive configurations are
used as functional elements for the amplified detection of the target
DNA. In the presence of the analyte DNA, one of the hairpins is opened,
and this triggers the autonomous cross-opening of the two hairpins
using the strand displacement principle. This leads to the formation
of nanowires consisting of the HRP-mimicking DNAzyme. The resulting
DNA nanowires act as catalytic labels for the colorimetric or chemiluminescent
readout of the sensing processes (the term “enzyme-free”
refers to a protein-free catalyst). The analytical platform allows
the sensing of the analyte DNA with a detection limit corresponding
to 1 × 10<sup>–13</sup> M. The optimized system acts as
a versatile sensing platform, and by coaddition of a “helper”
hairpin structure any DNA sequence may be analyzed by the system.
This is exemplified with the detection of the BRCA1 oncogene with
a detection limit of 1 × 10<sup>–13</sup> M