Graphene alone, in modified form or its composites had find their explicit position in the field of adsorption technology and hence assist in detection and removal of heavy metals like Cd (permissi...

An insight into Cadmium poisoning and its removal from aqueous sources by Graphene Adsorbents.

Sensitive imaging of microRNAs (miRNAs) in living cells is significant for accurate cancer clinical diagnosis and prognosis research studies, but it is challenged by inefficient intracellular delivery, instability of nucleic acid probes, and limited amplification efficiency. Herein, we engineered a DNAzyme-amplified cascade catalytic hairpin assembly (CHA)-based nanosystem (DCC) that overcomes these challenges and improves the imaging sensitivity. This enzyme-free amplification nanosystem is based on the sequential activation of DNAzyme amplification and CHA. MnO2 nanosheets were used as nanocarriers for the delivery of nucleic acid probes, which can resist the degradation by nucleases and supply Mn2+ for the DNAzyme reaction. After entering into living cells, the MnO2 nanosheets can be decomposed by intracellular glutathione (GSH) and release the loaded nucleic acid probes. In the presence of target miRNA, the locking strand (L) was hybridized with target miRNA, and the DNAzyme was released, which then cleaved the substrate hairpin (H1). This cleavage reaction resulted in the formation of a trigger sequence (TS) that can activate CHA and recover the fluorescence readout. Meanwhile, the DNAzyme was released from the cleaved H1 and bound to other H1 for new rounds of DNAzyme-based amplification. The TS was also released from CHA and involved in the new cycle of CHA. By this DCC nanosystem, low-abundance target miRNA can activate many DNAzyme and generate numerous TS for CHA, resulting in sensitive and selective analysis of miRNAs with a limit of detection of 5.4 pM, which is 18-fold lower than that of the traditional CHA system. This stable, sensitive, and selective nanosystem holds great potential for miRNA analysis, clinical diagnosis, and other related biomedical applications.

DNAzyme-Amplified Cascade Catalytic Hairpin Assembly Nanosystem for Sensitive MicroRNA Imaging in Living Cells.

Assembly of DNA triangular pyramid frustum for ultrasensitive quantification of exosomal miRNA.

DNA molecular probes have been increasingly used for biological imaging and tumor theranostics. In particular, live-cell imaging of low abundance microRNA (miRNA) with high accuracy and efficiency was extremely important for understanding functions and dynamics of miRNA. Herein, an easy-to-obtain DNA-nucleated spherical nucleic acid (DSNA) was constructed by one pair of hairpin probes “sticked” on self-assembled three-dimensional (3D) urchin-like DNA nanostructures (UDNs) to realize sensitive imaging of tumor-related miRNA in living cells. UDNs were prepared through four short single-stranded DNA by a simple “one-pot” annealing process that took only a few minutes. Moreover, sticking the reactants of hairpin probes on the UDNs not only sped up the reaction kinetic rate, but also improved the sensitivity and efficiency of miRNA-triggered hairpin cascade circuits. Compared with traditional AuNP-based spherical nucleic acid, the DSNA possessed superb biocompatibility and stability, excellent cell internalization capability and accessibility, which endowed them tremendous advantages for the monitoring of miRNA in living cells. Therefore, our developed strategy exhibited great potential in sensitive imaging of intracellular miRNA, offering a new avenue for early tumor diagnosis and related biomedical research. 

Hairpin cascade circuits on programmable DNA-Nucleated spherical nucleic acid for intracellular targeted MicroRNA imaging

Progress in the studies of RNA metabolism and function relies largely on molecular imaging systems, including those comprising a fluorogenic dye and an aptamer-based fluorescence-activating tag. G4 aptamers of Mango family, typically combined with a duplex/hairpin scaffold, activate fluorescence of a green-emitting dye TO1-biotin and hold great promise for intracellular RNA tracking. Here, we report a new Mango-based imaging platform. Its key advantages are tunability of spectral properties and applicability for visualization of small RNA molecules that require minimal tag size. The former advantage is due to an expanded (green-to-red-emitting) palette of TO1-inspired fluorogenic dyes, and the latter is ensured by the truncated duplex scaffold. To illustrate applicability of the improved platform, we tagged Mycobacterium tuberculosis sncRNA with the shortened aptamer-scaffold tag and visualized it in bacteria and bacteria-infected macrophages using the new red light-emitting Mango-activated dye.

/pdf/red-light-emitting-short-mango-based-system-enables-tracking-3tu1b2r8.pdf

Red light-emitting short Mango-based system enables tracking a mycobacterial small noncoding RNA in infected macrophages

Live cell dissection of microRNA activities is crucial for basic and translational medicine, but current hybridization-based strategies may fail to dissect surrounding-dependent activities. Here, we develop a genetically encoded miRNA-induced light-up RNA amplifier (iLAMP) that enables fast-activated, signal-amplified, fluorogenic imaging of miRNA activities in live cells. iLAMP responds to miRNA targets in the mode of "activation upon cleavage", in which the light-up RNA aptamer restores its fluorescence rapidly upon cleavage by the RNA-induced silencing complex. We demonstrate that iLAMP affords substantial signal amplification of ∼100-fold and high specificity in single nucleotide discrimination because of the miRNA-mediated cyclic cleavage. Combined with a Mango RNA aptamer reference module and a pseudoknot terminal stabilizer, iLAMP is shown for quantitative ratiometric imaging and dynamic monitoring of miRNA activities under exogenous stimulations. iLAMP is featured by a modular "plug and play" design and can be readily adapted to the detection of other miRNAs, highlighting its potential in tracking cell differentiation and screening miRNA therapeutics.

Genetically Encoded Light-Up RNA Amplifier Dissecting MicroRNA Activity in Live Cells.

Genetically encoded sensors afford powerful tools for studying small molecules and metabolites in live cells. However, genetically encoded sensors with a general design remain to be developed. Here we develop genetically encoded RNA sensors with a modular design for ratiometric and multiplexed imaging of small molecules in live cells. The sensor utilizes aptazyme as a recognition module and the light-up RNA aptamer as a signal reporter. The conformation of light-up aptamers is abrogated by a blocking sequence, and aptazyme-mediated cleavage restores the correct conformation, delivering activated fluorescence for small molecule imaging. We first developed a genetically encoded ratiometric sensor using Mango aptamer as a reference and SRB2 as a reporter. It is shown that the sensor allows quantitative imaging and detection of theophylline in live cells. The generality of the design is further demonstrated for imaging other small molecules by replacing the aptazymes. Its ability for multiplexed imaging of small molecules is further explored via the integration of different small-molecule responsive aptazymes and light-up RNA aptamers. This modular design could offer a versatile platform for imaging diverse molecules in living cells.

Genetically Encoded RNA Sensors for Ratiometric and Multiplexed Imaging of Small Molecules in Living Cells.

Application of Graphene as a Sorbent for Preconcentration and Determination of Trace Amounts of Cadmium in Water Samples

An enzyme-free fluorogenic RNA amplifier for small molecules detection and logic gates construction

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Genetically Encoded Light-Up RNA Amplifier Dissecting MicroRNA Activity in Live Cells.

Genetically Encoded RNA Sensors for Ratiometric and Multiplexed Imaging of Small Molecules in Living Cells.

Application of Graphene as a Sorbent for Preconcentration and Determination of Trace Amounts of Cadmium in Water Samples

An enzyme-free fluorogenic RNA amplifier for small molecules detection and logic gates construction