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Herein, a novel fluorescent ionic covalent organic framework (BTTA–BDNP) based on a linked carbazole unit was constructed for the synchronous monitoring and capture of TcO4−/ReO4−. BTTA–BDNP has a fast fluorescence response time with a low detection limit (66.7 nM) for ReO4− (a non-radioactive substitute for TcO4−). Meanwhile, the high charge density and hydrophobic skeleton of BTTA–BDNP enable it to exhibit rapid and selective trapping of ReO4− in complex environments. [ABSTRACT FROM AUTHOR]

We demonstrate for the first time the utilization of fluorogenic RNA aptamers for label-free uracil-DNA glycosylase (UDG) assay. Through rationally engineering the transcription machine with dU substitution, this assay requires only a single probe to simultaneously sense and amplify the UDG signal, achieving a low detection limit of 6.3 × 10−6 U mL−1. Moreover, it can be applied for screening UDG inhibitors and measuring endogenous UDG activity in different cells. [ABSTRACT FROM AUTHOR]

We demonstrate the zirconium ion-mediated assembly of a single quantum dot (QD)-based nanosensor for accurate detection of protein kinases (PKA) and polynucleotide kinases (PNK). This nanosensor is very sensitive with a detection limit of 8.82 × 10−4 U mL−1 for PKA and 1.40 × 10−5 U mL−1 for PNK. Moreover, it can be used to analyze the enzyme kinetic parameters and screen the inhibitors of PKA and PNK, with potential applications in drug discovery and clinical diagnosis. [ABSTRACT FROM AUTHOR]

We demonstrate the development of a new fluorescent biosensor for sensitive DNA methylation assay by integrating single-molecule detection with endo IV-assisted signal amplification. This biosensor possesses the characteristics of good selectivity and high sensitivity with a detection limit of 7.3 × 10−17 M. It can distinguish as low as 0.01% methylation level, and can analyze genomic DNA methylation even in a single cancer cell. [ABSTRACT FROM AUTHOR]

We demonstrate for the first time the integration of a dumbbell probe with dual signal amplification for the simultaneous detection of multiple DNA methyltransferases (MTases). This method is very sensitive with a detection limit of 2.15 × 10−5 U mL−1 for DNA adenine methyltransferase (Dam) and 3.23 × 10−6 U mL−1 for CpG Methyltransferase (M.SssI), and it can be used to screen the enzyme inhibitors and simultaneously measure Dam and M.SssI in complex biological samples. [ABSTRACT FROM AUTHOR]

We develop a new fluorescence method for the sensitive detection of protein tyrosine phosphatase 1B (PTP1B) based on dephosphorylation-directed tricyclic DNA amplification cascades. This method exhibits good specificity and high sensitivity with a detection limit of 0.24 pM. Moreover, it can be applied for kinetics analysis, inhibitor screening, and the accurate detection of PTP1B in a variety of cancer cells. [ABSTRACT FROM AUTHOR]

A fluorometric method is described for the determination of thrombin. Polymer nanoparticles containing the luminol-terbium(III) complex (luminol-Tb) were prepared where luminol acts as the bridging ligand, and Tb(III) acts as the central metal ion. Thrombin possesses a large number of electrons donating groups that coordinate with luminol-Tb. Following coordination, the rigidity of the linker is increased, and this decreases the non-radiative decay rate and induces an increase in fluorescence intensity at 430 nm. Hence, thrombin can be fluorometrically determined. The detection limit of thrombin is as low as 3.5 pM (at an SNR of 3). This is about 10 times lower than assays using an aptamer. The method was applied in the determination of thrombin in human serum via the standard addition method and gave satisfying results. [ABSTRACT FROM AUTHOR]

The authors describe an electrochemical and an optical method for the determination of As(V) by using iron oxyhydroxide (FeOOH) nanorods that display peroxidase-mimicking activity. The nanorods catalyze the oxidation of substrate ABTS by H2O2 to form a green product with an absorption maximum at 418 nm. If, however, As(V) is electrostatically adsorbed on the nanorods, the oxidation is gradually inhibited. A colorimetric assay was worked out based on these findings. Response is linear in the 0 to 8 ppb and 8 to 200 ppb As(V) concentration range, and the detection limit is 0.1 ppb. Even higher sensitivity is achieved in an electrochemical method which is based on the excellent electrical conductivity of FeOOH nanorods. Electrochemical analysis of As(V) was achieved by first adsorbing As(V) on the nanorods. This inhibits the ABTS reduction current signal, best measured at a potential of 150 mV (vs. Ag/AgCl). The linear range extends from 0.04 to 200 ppb, and the detection limit is as low as 12 ppt. [ABSTRACT FROM AUTHOR]

Herein, a novel fluorescent ionic covalent organic framework (BTTA–BDNP) based on a linked carbazole unit was constructed for the synchronous monitoring and capture of TcO4−/ReO4−. BTTA–BDNP has a fast fluorescence response time with a low detection limit (66.7 nM) for ReO4− (a non-radioactive substitute for TcO4−). Meanwhile, the high charge density and hydrophobic skeleton of BTTA–BDNP enable it to exhibit rapid and selective trapping of ReO4− in complex environments. [ABSTRACT FROM AUTHOR]

Human single-stranded-selective monofunctional uracil glycosylase (hSMUG1) and alkyladenine glycosylase (hAAG) are important base-excision repair (BER) glycosylases responsible for deamination and alkylation repair. Their dysfunctional activities have strong association with various multifactorial diseases and cancers. Herein, by integrating three-dimensional (3D) DNA walker with single-molecule technique, we construct bidirectional strand displacement-driven 3D DNA walkers for single-molecule monitoring of multiple DNA glycosylases. In the presence of hSMUG1 and hAAG, the damaged U and I in bifunctional dumbbell probe are removed by APE1, activating bidirectional self-priming strand displacement amplification (SP-SDA) to produce two trigger DNAs. Trigger DNAs hybridize with Cy5/Alexa Fluor 488 signal probes and subsequently serve as the walker DNAs to induce cyclic APE1-powered cleavage of two signal probes, liberating abundant Cy5 and Alexa Fluor 488 from AuNPs. Due to high precision of intracellular BER mechanisms, high efficiency of bidirectional SP-SDA-directed 3D DNA walkers and ultrahigh signal-to-noise ratio of single-molecule imaging, this nanosensor exhibits a detection limit of 8.14 × 10−10 U/μL for hSMUG1 and 4.50 × 10−9 U/μL for hAAG. Importantly, it can measure kinetic parameters, identify potential inhibitors, discriminate cancer from normal cells, and quantify glycosylases activities in various cancer cells at single-cell level, with promising potentials in biomedical and clinical applications. • We construct bidirectional strand displacement-driven 3D DNA walkers. • This nanosensor enables single-molecule monitoring of multiple human glycosylases. • This nanosensor can measure kinetic parameters and screen potential inhibitors. • This nanosensor can discriminate cancer cells from normal cells. [ABSTRACT FROM AUTHOR]

Guanine is the most susceptible to oxidation among all the DNA bases, and 8-oxo-7,8-dihydroguanine (OG) is one of main oxidation products that can occur in any part of chromosomal DNA. OG in the telomere sequence is associated with telomere shortening, cell aging, and dysfunction, and it may induce cancers. The accurate detection of OG in telomeres is important to early clinical diagnosis and molecular research. Herein, we develop a simple and rapid method to sensitively measure 8-oxo-7,8-dihydroguanine (OG) in telomeres of cancer cells by using Bsu polymerase-mediated fluorescence coding. This method is very simple without the requirement for any nucleic acid amplification or specific restriction enzyme recognition reaction, and Bsu polymerase can selectively incorporate Cy5-dATP into the opposite site of OG, endowing this method with good specificity. Moreover, the introduction of single-molecule detection significantly improves the sensitivity. This method can detect OG within 70 min with a limit of detection (LOD) of 2.45 × 10−18 M, and it can detect OG in genomic DNA extracted from H 2 O 2 -treated HeLa cells with a LOD of 0.0094 ng, holding great potential in disease-specific gene damage research and early clinic diagnosis. We develop a simple and rapid method to sensitively measure 8-oxo-7,8-dihydroguanine (OG) in telomeres of cancer cells by using Bsu polymerase-mediated fluorescence coding. [Display omitted] • We develop a simple and rapid method to sensitively measure 8-oxo-7,8-dihydroguanine (OG) in telomeres of cancer cells. • This method is on the basis of Bsu polymerase-mediated fluorescence coding. • This method exhibits high sensitivity and good specificity. • This method can detect OG within 70 min. • This method can detect OG in genomic DNA extracted from H 2 O 2 -treated HeLa cells. [ABSTRACT FROM AUTHOR]

In this work, a sensitive electrochemiluminescence (ECL) biosensor was proposed to detect protein kinase activity utilizing the signal amplification of bull serum albumin-templated gold nanoclusters (BSA-Au NCs) for graphite-like carbon nitride material (g-C 3 N 4). In this system, g-C 3 N 4 was utilized as a cathodic ECL emitter, and BSA-AuNCs were anchored to the phosphorylated peptides modified g-C 3 N 4 /GCE by Au S bond in the presence of adenosine 5′-[γ-thio] triphosphate (ATP-s) and protein kinase A (PKA). Attributed to the outstanding catalytic activity of BSA-AuNCs in the ECL process, the ECL intensity of this system shows 4.5-fold enhancement than that without BSA-AuNCs. Such enhancement in combination with the intensity of ECL signal and protein kinase activity enables us to fabricate an ultrasensitive ECL biosensor to detect PKA with low background. The proposed ECL platform can be utilized to analyse PKA activity of biological sample quantitatively and screen kinase inhibition qualitatively. Unlabelled Image • ECL biosensor based on the interaction between g-C 3 N 4 and Au NCs has been designed. • Au NCs can act as a catalyst to efficiently magnify the ECL intensity of g-C 3 N 4. • It provided a highly sensitive strategy for PKA activity detecting with a low detection limit. • The method proved excellent performance on the kinase inhibitor assay. [ABSTRACT FROM AUTHOR]