When the target biorecognition-triggered assembly of
two Mg2+-dependent DNAzymes (MNAzymes) is employed for
dually catalytic
release of peroxidase-mimicking G-quadruplex DNAzymes (G-DNAzymes),
this work develops a novel homogeneous colorimetric method for an
ultrasensitive bioassay of platelet-derived growth factor-BB (PDGF-BB).
The first MNAzyme assembly is realized through a highly specific aptamer
biorecognition-driven proximity ligation reaction. Its catalytic cleavage
toward the two designed hairpin substrates not only releases a large
amount of G-DNAzymes for colorimetric signal transduction but also
enables the spontaneous assembly of another MNAzyme for signal amplification.
This leads to the successful detection of PDGF-BB in a wide linear
range from 2.0 pg mL–1 to 20 ng mL–1 with a very low detection down to 0.088 pg mL–1. As the whole reactions including aptamer biorecognitions, DNA hybridizations,
and catalytic cleavages of MNAzymes are conducted in a homogeneous
solution, this method has very simple manipulations and also has high
repeatability. In addition, the high specificity of the aptamer biorecognition-triggered
signal transduction decides the excellent selectivity of the method.
This bioassay does not require an expensive instrument and nucleic
acid labeling for signal readout or any nanomaterial, enzyme, or nuclease
for signal amplification. Thus, it displays an extensive potential
for clinical diagnostic applications.
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