Seongnam, South Korea
Seongnam, South Korea

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Shah P.,Copenhagen University | Cho S.K.,Copenhagen University | Thulstrup P.W.,Copenhagen University | Bhang Y.-J.,SeouLin Bioscience Co. | And 4 more authors.
Nanotechnology | Year: 2014

MicroRNAs (miRNAs) are small regulatory RNAs (size ∼21 nt to ∼25 nt) which regulate a variety of important cellular events in plants, animals and single cell eukaryotes. Especially because of their use in diagnostics of human diseases, efforts have been directed towards the invention of a rapid, simple and sequence selective detection method for miRNAs. Recently, we reported an innovative method for the determination of miRNA levels using the red fluorescent properties of DNA/silver nanoclusters (DNA/AgNCs). Our method is based on monitoring the emission drop of a DNA/AgNCs probe in the presence of its specific target miRNA. Accordingly, the accuracy and efficiency of the method relies on the sensitivity of hybridization between the probe and target. To gain specific and robust hybridization between probe and target, we investigated a range of diverse salts, organic solvents, and buffer to optimize target sensing conditions. Under the newly adjusted conditions, the target sensitivity and the formation of emissive DNA/AgNCs probes were significantly improved. Also, fortification of the Tris-acetate buffer with inorganic salts or organic solvents improved the sensitivity of the DNA/AgNC probes. On the basis of these optimizations, the versatility of the DNA/AgNCs-based miRNA detection method can be expanded. © 2014 IOP Publishing Ltd.

Lee H.-Y.,University of Seoul | Lee T.,University of Seoul | Lee T.,SeouLin Bioscience Co. | Lee N.,University of Seoul | And 7 more authors.
Carcinogenesis | Year: 2011

Hypoxia-Inducible Factor (HIF)-1α/β heterodimer is a master transcription factor for several genes involved in angiogenesis, glycolysis, pH balance and metastasis. These HIF-1 target genes help tumors to overcome forthcoming metabolic obstacles as they grow. Under normoxic condition, the HIF-1α subunit is hydroxylated by its specific prolyl-4 hydroxylase 2, given the acronym PHD2. Hydroxylated HIF-1α becomes a target for von Hippel- Lindau (VHL), which functions as an E3 ubiquitin ligase. Src prevents hydroxylation-dependent ubiquitinylation of HIF-1α, thus stabilizing it under normoxic conditions. We found that active Src does not directly phosphorylate any tyrosine residue of PHD2. In vitro hydroxylation reaction showed that the presence of the purified active Src protein does not inhibit the hydroxylation activity of the purified PHD2 enzymes. Instead of directly inhibiting PHD2, Src recruits several downstream-signaling pathways to intercept hydroxylation-dependent ubiquitinylation of HIF-1α. Using biochemical and genetic inhibition, we demonstrated that Src requires reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase/Rac complex for stabilization of HIF-1α. We found that excess vitamin C treatment attenuates Src-induced HIF-1α activation. HIF-1a-hydroxylation-dependent VHL pull-down assay showed that Src inhibits cellular PHD2 activity by inducing ROS production in a mechanism involving Rac1-dependent NADPH oxidase. Src-induced ROS reduces cellular vitamin C, which is required for the activity of PHD2, thus Src can block VHL recruitment of HIF-1a, leading to stabilization of HIF-1α. © The Author 2011. Published by Oxford University Press. All rights reserved.

Shah P.,Copenhagen University | Choi S.W.,Seoulin Bioscience Co. | Kim H.-J.,Seoulin Bioscience Co. | Cho S.K.,Copenhagen University | And 5 more authors.
Analyst | Year: 2015

In recent years microRNAs (miRNAs) have been established as important biomarkers in a variety of diseases including cancer, diabetes, cardiovascular disease, aging, Alzheimer's disease, asthma, autoimmune disease and liver diseases. As a consequence, a variety of monitoring methods for miRNAs have been developed, including a fast and simple method for miRNA detection by exploitation of the unique photoluminescence of DNA-templated silver nanoclusters (DNA/AgNCs). To increase the versatility of the AgNC-based method, we have adopted DNA/RNA chimera templates for AgNC-based probes, allowing response from several human miRNAs which are hardly detectable with DNA-based probes. Here, we demonstrate in detail the power of DNA/RNA chimera/AgNC probes in detecting two human miRNAs, let-7a and miR-200c. The DNA/RNA chimera-based probes are highly efficient to determine the level of miRNAs in several human cell lines. © 2015 The Royal Society of Chemistry.

The present invention provides a silver nanocluster probe which comprises a silver nanoparticle binding region and a specific nucleotide sequence region that specifically binds to a target polynucleotide, wherein the silver nanocluster probe is configured such that it will emit detectable light when silver nanoparticles bind to the silver nanoparticle binding region to form a silver nanocluster, but light emission from the silver nanocluster probe will decrease or decay when the target polynucleotide binds to the specific nucleotide sequence region. According to the present invention, either the presence of a target polynucleotide in a sample or a mutation in the target polynucleotide can be detected in a rapid and convenient manner by determining whether light emission decreases or decays when the target polynucleotide binds to the specific nucleotide sequence region of the silver nanocluster probe that emits detectable light.

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