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...

Nonalcoholic fatty liver disease (NAFLD) can progress gradually to liver failure, early warning of which is critical for improving the cure rate of NAFLD. In situ imaging and monitoring of overexpressed miR-21 is an advanced strategy for NAFLD diagnosis. However, this strategy usually suffers from the high background imaging in living cells owing to the complexity of the biological system. To overcome this problem, herein, we have developed a one-donor–two-acceptor nanoprobe by assembling gold nanoparticles (AuNPs) coupled with BHQ2 (AuBHQ) and quantum dots (QDs) through DNA hybridization for imaging of miR-21 in living cells. The fluorescence of QDs was quenched up to 82.8% simultaneously by the AuNPs and the BHQ2 via nanometal surface energy transfer and fluorescence resonance energy transfer, reducing the background signals for target imaging. This low background fluorescent nanoprobe was successfully applied for imaging the target miR-21 in nonalcoholic fatty liver cells by catalyzing the disassembly of QDs with the AuBHQ and the fluorescence recovery of QDs. In addition, the sensitivity of this nanoprobe has also been enhanced toward detecting miR-21 in the range of 2.0–15.0 nM with the detection limit (LOD, 3σ) of 0.22 nM, which was 13.5 times lower than that without BHQ2. The proposed approach provides a new way for early warning, treatments, and prognosis of NAFLD.

A novel liposome amplification strategy is developed for ricin B-chain (RTB) detection by using g-C3N4-MnO2 sandwich nanocomposite as a low background signal platform.

No abstract