Graphene oxide (GO) has been proven as an outstanding fluorescence anisotropy (FA) amplifier. Yet the traditional GO amplified FA assays lack high sensitivity because of the 1:1 binding ratio between target and dye-modified probe. Herein, we report a new target-catalyzed hairpin assembly (CHA), an enzyme-free DNA circuit, assisted GO amplified FA strategy for microRNA-21 (miRNA-21) detection. In the presence of miRNA-21, the CHA was initiated and plenty of H1-H2 duplexes were produced continuously. The obtained H1-H2 duplex could induce the formation of a H1-H2-probe DNA (pDNA) complex by the toehold-mediated strand exchange reaction, which led the dye-modified pDNA to leave away from the GO surface, resulting in a decreased FA of the system. By monitoring the decrease of FA, miRNA-21 could be detected in the range of 0-16 nM. The limit of detection (LOD, 3σ) was 47 pM, which was 194 times lower than that without CHA. In addition, the selectivity of this method has also been enhanced greatly as compared to that without CHA. Our method has great potential to be applied for detecting different types of targets and monitoring diverse molecular interactions by adapting the corresponding nucleotide sequence.
In
this work, we propose a three-layer hierarchical hybridization
chain reaction (3L hHCR) composed of 1stHCR, 2ndHCR, and 3rdHCR to achieve robust signal amplification
efficiency and broaden the applied range of HCR-based systems. In
principle, the execution of superior HCR generates the formation of
the initiator (named as 2ndI or 3rdI) of the
subordinate HCR that relies on the introduction of the target sequence
(1stI). To avoid the high background signal of the 3L hHCR
system, a strategy of “splitting reconstruction” was
adopted. The initiator of the subordinate HCR was designed as two
separate fragments (splitting) that are obtained together (reconstruction)
for the motivation of the subordinate HCR after the completion of
the superior HCR. The implementation of the entire 3L hHCR system
generates significant fluorescence recovery that derives from the
impediment of Förster resonance energy transfer between fluorophore
and quencher; thus, ultrasensitive detection of 1stI in
the range of 50 pM to 10 nM can be achieved. Surprisingly, when the
concentration of 1stI is lower than 1 nM, the 3L hHCR shows
excellent ability to discriminate against various concentrations of 1stI, which is better than that of the 2L hHCR I system. Due
to the hierarchical self-assembly mechanism, the 3L hHCR can also
be reliably operated as a cascade AND logic gate with a high specificity
and molecular keypad lock with a prompt error-reporting function.
Furthermore, the 3L hHCR-based molecular keypad lock also shows potential
application in the accurate diagnosis of cancer. The 3 L hHCR shows
visionary prospects in biosensing and the fabrication of advanced
biocomputing networks.
Accurate
detection and imaging of tumor-related microRNA (miRNA)
in living cells hold great promise for early cancer diagnosis and
prognosis. One of the challenges is to develop methods that enable
the identification of multiple miRNAs simultaneously to further improve
the detection accuracy. Herein, a simultaneous detection and imaging
method of two miRNAs was established by using a programmable designed
DNA tetrahedron nanostructure (DTN) probe that includes a nucleolin
aptamer (AS1411), two miRNA capture strands, and two pairs of metastable
catalytic hairpins at different vertexes. The DTN probe exhibited
enhanced tumor cell recognition ability, excellent stability and biocompatibility,
and fast miRNA recognition and reaction kinetics. It was found that
the DTN probe could specifically enter tumor cells, in which the capture
strand could hybridize with miRNAs and initiate the catalytic hairpin
assembly (CHA) only when the overexpressed miR-21 and miR-155 existed
simultaneously, resulting in a distinct fluorescence resonance energy
transfer signal and demonstrating the feasibility of this method for
tumor diagnosis.
The as-prepared CDs–RTA conjugates exhibit enhanced internalization, improved stability against enzymatic digestion and an increased location rate of RTA to the ER, and thus much more RTA could translocate to the cytosol and ribosome to exert toxic effects.
Here we report a chirality transfer of cysteine, which at first was to the plasmonic resonance region of gold nanobipyramids and then to that of Ag nanoshell with the growth...
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