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This paper reports an improved catalytic molecular beacon. Addition of the target oligonucleotide activates a DNA enzyme (DNAzyme), which, in turn, activates multiple copies of molecular beacons (MB) and gives rise to a strong fluorescence signal. In a previous design, the activated DNAzyme could oligomerize, especially dimerize, and result in inactivation of the DNAzyme. The current design avoids...
The peroxidase activities of the complexes of hemin and intermolecular four-stranded G-quadruplexes formed by short-stranded X n G m X p sequences (X=A, T or C), especially T n G m T p sequences, were compared. The results, combining with those of circular dichroism (CD) spectra and acid–base transition study for DNA–hemin complexes, provide some important...
A novel label-free and sensitive fluorescent aptasensor for the detection of potassium ion (K + ) was developed based on the horseradish peroxidase–mimicking DNAzyme (HRP–DNAzyme). In this work, we selected a K + -stabilized single stranded DNA (ssDNA) with G-rich sequence as the recognition element. In the presence of K + , the G-rich DNA folded into the G-quadruplex structure,...
A selective, colorimetric assay for detection of glucose in urine was developed by transducing oxidation of glucose into the color change of 10-acetyl-3,7-dihydroxy phenoxazine (ADHP) using hemin-G quadruplex DNAzyme. Oligonucleotide 5′-ATTGGGAGGGATTGGGTGGGCAC-3′ was used to form a stable G-quadruplex structure. After binding with hemin, the complex of G-quadruplex and hemin acted as a horseradish...
We report a new label-free colorimetric aptasensor based on DNAzyme–aptamer conjugate for rapid and high-throughput detection of Ochratoxin A (OTA, a possible human carcinogen, group 2B) in wine. Two oligonucleotides were designed for this detection. One is N1 for biorecognition, which includes two adjacent sequences: the OTA-specific aptamer sequence and the horseradish peroxidase (HRP)-mimicking...
A portable, rapid and cost-effective DNAzyme based sensor for lead ions detection in water samples has been developed using an optical fiber sensor platform. The presence of Pb 2+ cleaves the DNAzymes and releases the fluorescent labeled fragments, which further hybridize with the complementary strands immobilized on the optic fiber sensor surface. Subsequent fluorescent signals of the hybridized...
This paper reports the development of an ultra-sensitive colorimetric method for the detection of trace mercury ions involving DNAzymes, Au nanoparticle aggregation, magnetic nanoparticles and an endonuclease. DNAzyme-sensing elements are conjugated to the surface of Au nanoparticle-2, which can crosslink with the T-rich strands coated on Au nanoparticle-1 to form Au nanoparticle aggregation. Other...
A functional nucleic acid-based amplification machine was designed for simple and label-free ultrasensitive colorimetric biosensing of microRNA (miRNA). The amplification machine was composed of a complex of trigger template and C-rich DNA modified molecular beacon (MB) and G-rich DNA (GDNA) as the probe, polymerase and nicking enzyme, and a dumbbell-shaped amplification template. The presence of...
DNAzyme-based catalytic beacons have been widely studied for both in vivo and in vitro molecular detection. However, only a few label-free catalytic beacons with excellent analytical performance have been reported so far. In this work, by combining a catalytic DNAzyme for amplified sensing through enzymatic turnover with cleavage-induced G-quadruplex formation, a label-free DNAzyme biosensor was developed...
Aptamers are analogous to antibodies in their range of target recognition. G-quadruplex DNAzymes exhibit peroxidase-like activity toward certain specific reactions. Despite aptazyme sensors, based on aptarmer and DNAzyme conjugates, have the potential to replace many conventional immune-biosensors; the mechanism concerning high background interference has scarcely been discussed. In this work, by...
A novel signal amplification strategy based on Cu2+-dependent DNAzyme was developed for sensing Cu2+ ion by combining hybridization chain reaction (HCR) with fluorescence resonance energy transfer (FRET) technique. In the presence of Cu2+ ion, the substrate strands of Cu2+-dependent DNAzyme immobilized on magnetic beads were specifically cleaved and released. The released strands initiated the HCR...
Recently a covalent peroxidase-mimicking DNAzyme (cPMDNAzyme) with the improved catalytic activity was prepared. Here we demonstrate that hydrogen peroxide, the oxidant substrate of cPMDNAzyme is an inactivating agent of this catalyst. Presence of the reductant substrate, 2,2′-azino-bis(3-ethylbenthothiazoline-6-sulfonic acid (ABTS) prevents the inactivation of cPMDNAzyme. The experimental conditions...
A novel label-free electrochemical biosensor for the detection of Hg2+ based on ligase mediated creation of G-quadruplex-hemin DNAzyme has been developed. Firstly, Cp probe was immobilized on the gold electrode surface through Au–SH bond. In the presence of Hg2+, Cp and Ap probes were partly hybridized with the LJ probe respectively through the specific T–Hg2+–T interaction. Then, the adjacent 3′-OH...
Highly sensitive detection of Pb2+ is very necessary for water quality control, clinical toxicology, and industrial monitoring. In this work, a simple and novel DNAzyme-based SERS quadratic amplification method is developed for the detection of Pb2+. This strategy possesses some remarkable features compared to the conventional DNAzyme-based SERS methods, which are as follows: (i) Coupled DNAzyme-activated...
A new simple and highly sensitive electrochemical method for pyrophosphatase (PPase) activity detection was developed based on the peroxidase-like activity of G-quadruplex-Cu2+ DNAzyme. In the absence of PPase, Cu2+ could coordinate with pyrophosphate (PPi) to form Cu2+-PPi compound. While in the presence of PPase, it could destroy the coordinate compound because PPase catalyzed the hydrolysis of...
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