• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.2
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• pp.86-90
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• 2011

The effects of cations are very important in field-effect transistors (FETs) type DNA sensors detecting the intrinsic negative charge between single-stranded DNA and double-stranded DNA without labeling, because the intrinsic negative charge of DNA is neutralized by cations in electrolyte solution. We consider the Debye length, which depends on the concentration of cations in solution, to detect DNA hybridization based on the intrinsic negative charge of DNA. The Debye length is longer in buffer solution with a lower concentration of NaCl and the intrinsic negative charge of DNA is more effective on the channel surface in longer Debye length solution. The shifts in the gate voltage by DNA hybridization with complementary target DNA are 21 mV in 1 mM NaCl buffer solution, 7.2 mV in 10 mM NaCl buffer solution, and 5.1 mV in 100 mM NaCl buffer solution. The sensitivity of FETs to detect DNA hybridization based on charge detection without labeling depends on the Debye length.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.71-73
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• 2006

This research aims to develop a multiple channel electrochemical DNA chip using micro- fabrication technology. At first, we fabricated a high integrated type DNA chip array by lithography technology. Several probe DNAs consisting of thiol group at their 5-end were immobilized on the gold electrodes. Then target DNAs were hybridized by an electrical force. Redox peak of cyclic-voltammogram showed a difference between target DNA and mismatched DNA in the anodic peak current. Therefore. it is able to detect a various genes electrochemically after immobilization of a various probe DNA and hybridization of label-free DNA on the electrodes simultaneously. It suggested that this DNA chip could recognize the sequence specific genes.

• Journal of Microbiology and Biotechnology
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• v.27 no.1
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• pp.72-76
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• 2017

Detection of exon 19 deletion mutation in the epidermal growth factor receptor (EGFR) gene, which results in increased and sustained phosphorylation of EGFR, is important for diagnosis and treatment guidelines in non-small-cell lung cancer. Here, we have developed a simple and convenient detection system using the interaction between G-quadruplex and fluorophore thioflavin T (ThT) for discriminating EGFR exon 19 deletion mutant DNA from wild type without a label and quencher. In the presence of exon 19 deletion mutant DNA, the probe DNAs annealed to the target sequences were transformed into G-quadruplex structure. Subsequent intercalation of ThT into the G-quadruplex resulted in a light-up fluorescence signal, which reflects the amount of mutant DNA. Due to stark differences in fluorescence intensity between mutant and wild-type DNA, we suggest that the induced G-quadruplex structure in the probe DNA can report the presence of cancer-causing deletion mutant DNAs with high sensitivity.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.549-549
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• 2012

Early detection of cancer biomarkers in the blood is of vital importance for reducing the mortality and morbidity in a number of cancers. From this point of view, immunosensors based on nanowire (NW) and carbon nanotube (CNT) field-effect transistors (FETs) that allow the ultra-sensitive, highly specific, and label-free electrical detection of biomarkers received much attention. Nevertheless 1D nano-FET biosensors showed high performance, several challenges remain to be resolved for the uncomplicated, reproducible, low-cost and high-throughput nanofabrication. Recently, two-dimensional (2D) graphene and reduced GO (RGO) nanosheets or films find widespread applications such as clean energy storage and conversion devices, optical detector, field-effect transistors, electromechanical resonators, and chemical & biological sensors. In particular, the graphene- and RGO-FETs devices are very promising for sensing applications because of advantages including large detection area, low noise level in solution, ease of fabrication, and the high sensitivity to ions and biomolecules comparable to 1D nano-FETs. Even though a limited number of biosensor applications including chemical vapor deposition (CVD) grown graphene film for DNA detection, single-layer graphene for protein detection and single-layer graphene or solution-processed RGO film for cell monitoring have been reported, development of facile fabrication methods and full understanding of sensing mechanism are still lacking. Furthermore, there have been no reports on demonstration of ultrasensitive electrical detection of a cancer biomarker using the graphene- or RGO-FET. Here we describe scalable and facile fabrication of reduced graphene oxide FET (RGO-FET) with the capability of label-free, ultrasensitive electrical detection of a cancer biomarker, prostate specific antigen/${\alpha}$ 1-antichymotrypsin (PSA-ACT) complex, in which the ultrathin RGO channel was formed by a uniform self-assembly of two-dimensional RGO nanosheets, and also we will discuss about the immunosensing mechanism.

• Journal of Microbiology and Biotechnology
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• v.28 no.9
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• pp.1467-1472
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• 2018

In this study, DNA-templated copper nanoclusters (DNA-CuNCs) were used to detect exonuclease III (Exo III) activity, which is important for the diagnosis and therapy of several diseases. The results of this study showed that Exo III was affected by the concentrations of magnesium ions and sodium ions, and its optimal conditions for cleavage were $5mM\;Mg^{2+}$ and less than $25mM\;Na^+$. With a blunt-end DNA, more than 98% of DNA was digested by Exo III. As expected, with two or four cytosines in the terminal position of a 4-base overhanging DNA such as 5'-GGCC-3' and 5'-CCCC-3', there was little cleavage by Exo III compared with a blunt-end DNA.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.51-53
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• 2002

This research aims to develop a multiple channel electrochemical DNA chip using micro-fabrication technology. At first, we fabricated a high integrated type DNA chip array by lithography technology. Several probe DNAs consisting of thiol group at their 5-end were immobilized on the sold electrodes. Then target DNAs were hybridized by an electrical force. Redox peak of cyclic-voltammogram showed a difference between target DNA and mismatched DNA in the anodic peak current. Therefore, it is able to detect a various genes electrochemically after immobilization of a various probe DNA and hybridization of label-free DNA on the electrodes simultaneously. It suggested that this DNA chip could recognize the sequence specific genes.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.943-947
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• 2008

A phosphate-specific and fluorescent probe was prepared for label-free phosphatase assays based on fluorescence polarization. By using the probe, dephosphorylation reactions of DNA and protein substrates by calf intestinal alkaline phosphatase (CIP) could effectively be monitored in real-time. Since this assay method does not require additional materials such as labeled substrates and phosphospecific antibodies to obtain fluorescence polarization signals, it is simple, cost-effective, and expected to be useful not only for measuring activity of phosphatases but also for high-throughput screening of phosphatase inhibitors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.358-360
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• 2014

For the several decades, various nanomaterials are broadly used in industry and research. With the growth of nanotechnology, the study of nanotoxicity is being accelerated. Particularly, mercury ion is widely used in real life. Because the mercury is representative high toxic material, it is highly recommended to detect the mercury ion. In previous reported work, thymine-thymine mismatches (T-T) capture mercury ion and create very stable base pair ($T-Hg^{2+}-T$). Here, we performed the high sensitive sensing method for direct label free detection of mercury ions and DNA binding using Kelvin Probe Force Microscope (KPFM). In this method, 30 base pairs of thymine (T-30) is used for mercury specific DNA binding ($T-Hg^{2+}-T$). KPFM is able to detect the mercury ion because there is difference between bare T-30 DNA and mercury mediated DNA ($T-Hg^{2+}-T$).

• Analytical Science and Technology
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• v.27 no.3
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• pp.121-139
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• 2014

In this review, we will discuss aptamer technologies including in vitro selection, signal transduction mechanisms, and designing aptamers and aptazyme for label-free biosensors and catalysts. Dye-displacement, a typical label-less method, is described here which allows avoiding relatively complex labeling steps and extending this application to any aptamers without specific conformational changes, in a more simple, sensitive and cost effective way. We will also describe most recent and advanced technologies of signaling aptamer and aptazyme for the various analytical and clinical applications. Quantum dot biosensor (QDB) is explained in detail covering designing and adaptations for multiplexed protein detection. Application to aptamer array utilizing self-assembled signaling aptamer DNA tile and the novel methods that can directly select smart aptamer or aptazyme experimentally and computationally will also be finally discussed, respectively.

• Preventive Nutrition and Food Science
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• v.4 no.4
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• pp.276-282
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• 1999

Ionizing radiation is considered to be an efficient technology to improve food safety and to extend food shelf-life in the food industry, and it has been used in food processing with a number of attributes. Food labeling should be established to enable the consumer to choose food freely, based on label information. A variety of methodologies to determine the physical, chemical, microbiological, and biological changes due to irradiation has been investigated in order to discriminate the irradiated and unirradiated food products for the consumer's free choice in food selection. However, no satisfactory method has been developed so far. In this review, various approaches based on DNA, immunochemical, and biological methods are addressed.