Catalyzed
hairpin assembly (CHA) is an important DNA engineering
tool for a variety of applications such as DNA nanotechnology and
biosensing. Here we report a hairpin-type of both-end-blocked DNAzyme
to improve the signal-to-background ratio during the CHA process.
In the design, the DNAzyme activity can be blocked efficiently via
locking both ends of the G-rich DNAzyme sequence in the loop and stem
(blocking efficiency = 96%) and can be easily recovered during the
CHA process (activation efficiency = 94%). The both-end-blocked DNAzyme
is by far the most sensitive optical detection mode for monitoring
the CHA process that can be used for determination of 0.05 fmol miRNA-21.
The fabricated CHA-DNAzyme sensing system was also able to discriminate
miRNA-21 from single-/three-base mismatch miRNA-21. The feasibility
of real application was also tested via detection of miRNA-21 levels
in tumor cell samples. Therefore, the sensing system with the advantages
of convenience, high sensitivity, and selectivity is an appealing
strategy for miRNA detection
