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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...
A versatile and sensitive surface plasmon resonance (SPR) biosensor based on two layers of graphene oxide-gold nanoparticles (GO-AuNPs) composites was designed for the detection of microRNA (miRNA) and small molecule adenosine. The bottom layer, which acted as a functionalized substrate on the sensor chip, provided a high specific surface area convenient for the immobilization of capture DNA molecules...
Metastasis, which derived from a primary tumor, accounts for 90% of mortality caused by cancer. Early diagnosis of cancer metastasis may significantly improve cure rate of patients who are at high risk for developing metastasis. In this study, we successfully achieved metastatic cancer cell and tissue-specific fluorescence imaging by using a new aptamer developed by cell-based systematic evolution...
Deoxyribonuclease I (DNase I) is an important physiological indicator and diagnostic biomarker, but traditional methods for assessing its activity are time-consuming, laborious, and usually radioactive. Herein, by effectively combining the special functions of DNase I and terminal deoxynucleotidyl transferase (TdT), a simple, green, cost-effective, label-free and ultrasensitive assay for DNase I activity...
In this work, we developed a simple, rapid and mild strategy for synthesis of DNA-templated fluorescent gold nanoclusters (AuNCs) through association of gold ions to DNA templates and reduction with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES). After systematical investigation on the formation of fluorescent AuNCs by using different DNA templates, C5 DNA was found as the best template...
We have developed a new methodology for fluorescence turn-on detection of uracil DNA glycosylase (UDG) activity based on G-quadruplex formation using a thioflavin T probe. In the presence of UDG, it catalyzed the hydrolysis of the uracil bases in the duplex DNA, resulting in the dissociation of the duplex DNA owing to their low melting temperature. Then, the probe DNA can be recognized quickly by...
A new ratiometric nanosensor is developed for selective and ultrasensitive detection of melamine based on conjugated polyelectrolyte (CPE)-stabilized silver nanoparticles (P1-AgNPs) by perfectly combining the advantages of CPE and AgNPs. P1 featuring a π-delocalized backbone bearing pyridinyl groups can act as an excellent dual-emission fluorescent probe as well as a polymer localizer for AgNPs. In...
The detection of nucleic acids is fundamental for studying their functions and for the development of biological studies and medical diagnostics. Herein, we report a new strategy for nucleic acid amplified detection by combining target-catalyzed dynamic assembly with host–guest interaction between β-cyclodextrin polymer (β-CDP) and pyrene. In this strategy, a metastable pyrene-labeled hairpin DNA...
Owing to its diversified structures, high affinity, and specificity for binding a wide range of non-nucleic acid targets, aptamer is a useful molecular recognition tool for the design of various biosensors. Herein, we report a new signal-on electrochemical biosensing platform which is based on an aptamer/target binding-induced strand displacement and triple-helix forming. The biosensing platform is...
In this work, a simple and sensitive electrochemical strategy for arsenite detection based on the ability of arsenite bound to single-strand DNA (ssDNA) and the signal transduction of single wall carbon nanotubes (SWCNTs) is developed. To realize this purpose, the ssDNA/SWCNTs complexes were formed at first by making ssDNA wrapped around SWCNTs via π-stacking. In the presence of arsenite, the arsenite...
In this work, we synthesized a type of magnetic mesoporous silica nanoparticle (denoted as Fe3O4@MSN) with Fe3O4 as the core and mesoporous silica the shell. The superparamagnetic Fe3O4-core provides high peroxidase-mimic activity and makes the artificial enzymatic system easily recyclable. Furthermore, Fe3O4 nanoparticles are encapsulated in MSN shells to hinder the aggregation and keep them stable...
A new sensing system is developed for selective and ultrasensitive detection of iodide based on the inner filter effect (IFE) between conjugated polyelectrolyte-stabilized silver nanoparticles (P1–AgNPs) and 4-oxo-4-(pyren-1-ylmethoxy) butanoic acid (probe 1). P1–AgNPs are designed to be capable of functioning as a composite light-absorber. Meanwhile, probe 1 is selected as an ideal fluorophore because...
A sensitive and simple electrochemical strategy has been developed for assay of protein kinase A (PKA) activity and inhibition using gold nanoparticles/multi-walled carbon nanotubes (AuNPs/MWNTs) nanohybrids. Key features of this assay included intrinsic peroxidase-like activity of positively-charged gold nanoparticles (+AuNPs) and signal transduction and amplification of multi-walled carbon nanotubes...
A novel approach for highly sensitive and selective genotyping of single-nucleotide polymorphism (SNP) has been developed based on ligation-rolling circle amplification (L-RCA) and stemless molecular beacon. In this approach, two tailored DNA probes were involved. The stemless molecular beacon, formed through the inclusion interactions of γ-cyclodextrin (γ-CD) and bis-pyrene labeled DNA fragment,...
In this paper, we report a highly selective sandwich-type fluorescence resonance energy transfer (FRET) assay for ATP detection by combining the unique optical properties of silica coated photon upconverting NaYF 4 :Yb 3+ , Er 3+ nanoparticles (Si@UCNPs) with the high specific recognition ability of ATP aptamer. In the protocol, a single aptamer of ATP was split into two fragments...
We report here a highly sensitive electrochemical sensing platform for Ag + detection based on Ag + -induced conformational change of cytosine-rich single stranded DNA C-rich ssDNA probe and the controlled assembly of MWCNTs. In the protocol, the gold electrode was first modified with a dense 16-mercaptohexadecanoic acid self-assembled monolayer (MHA/SAM). The hydrophobic MHA/SAM isolated...
An electrochemical method for nicotinamide adenine dinucleotide (NAD + ) detection with high sensitivity and selectivity has been developed by using molecular beacon (MB)-like DNA and Escherichia coli DNA ligase. In this method, MB-like DNA labeled with 5′-SH and 3′-biotin was self-assembled onto a gold electrode in its duplex form by means of facile gold–thiol chemistry, which resulted in...
A novel electrochemical DNA sensor was developed here by using peroxidase-like G-quadruplex-based DNAzyme as a biocatalytic label. A hairpin structure including the G-quadruplex-based DNAzyme in a caged configuration and the target DNA probe were immobilized on Au-electrode surface. Upon hybridization with the target, the hairpin structure was opened, and the G-quadruplex-based DNAzyme was generated...
The influence of silver ions on Escherichia coli and Staphylococcus epidermidis has been investigated by atomic force microscopy (AFM). Both single cell and cell communities were visualized, and the nanoscale ultrastructure images of these two bacteria strains before and after stimulation of silver ions were obtained. The results showed that in the case of E. coli after treatment with silver ions,...
This report has described a convenient genotyping method capable of detecting point mutations directly in human genomic DNA based on the combination of ligase chain reaction (LCR) and microbead-enrichment technique. LCR primers, including a biotin-labeled common primer and two fluorescence-labeled allele-specific primers, are designed for two alleles of a mutated site. When genomic DNA carries the...
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