|
Abstract
|
With the great advances in DNA nanotechnology, scientists have shown interest in developing dynamic nanostructures
for theranostic applications, analyte sensing and cargo delivery. Here, we present a specific enzymefree
ultrasensitive platform based on a multilayer coupled signal amplification strategy to quantify miR-21
molecule. The biosensor was integrated based on three signal amplification gadgets, namely a translatormediated
catalytic hairpin assembly (CHA), a multilayer DNA concatemer on the surface of gold decorated
magnetic nanoparticle (GMNP), and a DNAzyme-mediated catalytic signal amplification. MiR-21 mediates the
release of a DNA translator from an immobilized duplex to engage in a CHA reaction using three hairpins,
including a GMNP-conjugated hairpin 1 (H1), biotin-labeled hairpin 2 (H2) and a GMNP-conjugated hairpin 3
(H3) to form a three-way junction (3WJ). Meanwhile, a plenty of initiator strand 0 (S0) on GMNPs – each of
which has been bifunctionalized with S0/H1 or S0/H3 – drive several multilayer peroxidase-mimicking
DNAzyme concatemers in the presence of two accessory oligonucleotides; strand 1 (S1) and strand 2 (S2). Since a
G-rich sequence was attached at the 5′-end of S1 strand, in the presence of hemin cofactor, an active G-quadruplex
DNAzyme with peroxidase activity was formed. The concatemers on the surface of GMNPs can convert a
colorless substrate to a green product. The biosensor can detect as low as 1 aM of miR-21 and provide an
excellent capability to discriminate single-base mismatches. The required time for the formulation of the assay
reagents is about three days and the reaction time for the detection of miR-21 takes place in less than four hours.
|