• Food Engineering Progress
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• v.14 no.1
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• pp.21-26
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• 2010

C-Reactive protein (CRP), which is an 118 kDa pentameric protein, was secreted by the liver is an important biomarker for coronary disease, hypertension and inflammation. In this study, a method for CRP detection exploiting quantum dot (Qdot)-antibody conjugate was developed according to an indirect-competitive immunosensing protocol. For this purpose, a streptavidin-bound $Qdot_{605}$ was linked with a separately prepared biotinylated monoclonal antirat CRP antibody to produce a Qdot-antibody conjugate. The immunosensing was performed at 0.1 and 20 nM of the coating antigen and conjugate, respectively. The current method was found very sensitive in CRP detection, judging from the concentration-dependent fluorescence emission.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.61-61
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• 2003

• Journal of Electrochemical Science and Technology
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• v.14 no.1
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• pp.51-58
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• 2023

The effective detection of human chorionic gonadotropin (HCG) is considerably important for the clinical diagnosis of both of early pregnancy and nonpregnancy-related diseases. In this work, a simple and sensitive electrochemical sandwich-type immunosensing platform was designed by synthesizing b-cyclodextrin (CD) functionalized graphene (CD/GN) hybrid as simultaneously sensing platform and signal transducer coupled with rhodamine b (RhB) as probe. In brief, GN offers large surface area and high conductivity, while CD exhibits superior host-guest recognition capability, thus the primary antibody (Ab1) of HCG can be bound into the cavities of CD/GN to form stable Ab1/CD/GN inclusion complex; meanwhile, the secondary antibody (Ab2) and RhB can also enter into the cavities, producing RhB/Ab2/CD/GN complex. Then, by using Ab1/CD/GN as sensing platform and RhB/Ab2/CD/GN as signal transducer (in which RhB was signal probe), a simple sandwich-type immunosensor was constructed. Under the optimum parameters, the designed immunosensor exhibited a considerable low analytical detection of 1.0 pg mL^-1 and a wide linearity of 0.002 to 10.0 ng mL^-1 for HCG, revealing the developed sandwich-type electrochemical immunosensing platform offered potential real applications for the determination of HCG.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.762-763
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• 2005

• 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.

• KSBB Journal
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• v.20 no.2 s.91
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• pp.123-128
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• 2005

We have addressed two important issues of immunosensing biochips, including the construction of antibody functionalized suface for efficient affinity reactions and the development of a signal registration strategy that converts biospecific reactions into highly quantifiable electrochemical and/or optical signals. The developed immunoassay reaction is an integrated version of enzyme-mediated immunoprecipitaion reaction, which is widely used in immunohistochemistry, and electrochemical signaling reaction. For the evaluation of analytical performance of fabricated immunosensing biochips, signaling for mouse IgG in antiserum was conducted. Applications of the developed strategy have been found for the evaluation of histology chemicals and for the signal amplification for array-type biochip analysis.

• Journal of Microbiology and Biotechnology
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• v.17 no.6
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• pp.1031-1035
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• 2007

Prostate specific $antigen-{\alpha}_1-antichymotrypsin$ was detected by a double-enhancement strategy involving the exploitation of both colloidal gold nanoparticles (AuNPs) and precipitation of an insoluble product formed by HRP-biocatalyzed oxidation. The AuNPs were synthesized and conjugated with horse-radish peroxidase-PSA polyclonal antibody by physisorption. Using the protein-colloid for SPR-based detection of the PSPJACT complex showed their enhancement as being consistent with other previous studies with regard to AuNPs enhancement, while the enzyme precipitation using DAB substrate was applied for the first time and greatly amplified the signal. The limit of detection was found at as low as 0.027 ng/ml of the PSA/ACT complex (or 300 fM), which is much higher than that of previous reports. This study indicates another way to enhance SPR measurement, and it is generally applicable to other SPR-based immunoassays.

• Bulletin of the Korean Chemical Society
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• v.28 no.10
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• pp.1792-1796
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• 2007

Insulating effects on Au electrode according to the thickness and density of coated materials are well-known. To do electrochemical immunoassay reproducibly the glod electrode would be coated with self-assembled monolayers and antobodies. To get reproducibility, the antobody monolayer should be packed at highest density so that the amount of immobilized antibody at defined area should be the same. The calix[4]crown-5 SAMs could provide the basis for the antibodies to be immobilized reproducibly and at highest density. But the insulating effect would be highest too. We proved that the compactly packed protein monolayers on SAMs inhibited the electron transfer by block the free shuttling of redox molecules. The inhibition was minimized by inserting redox molecules in between the proteins during immobilization process. In this paper, we demonstrated that the calix[4]crown-5 SAMs would provide the protein monolayers with highest density and new method to minimize the insulating effect by inserted redox molecules in between the compactly packed protein monolayers.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3103-3108
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• 2010

Conducting polymers (CPs) are widely used as matrixes for the entrapment of enzymes in analytical chemistry and biosensing devices. However, enzyme-catalyzed polymerization of CPs is rarely used for immunosensing due to the difficulties involved in the quantitative analysis of colloidal CPs in solution phase. In this study, an enzyme-amplified electrocatalytic immunosensor employing a CP as a redox marker has been developed. A polyanionic polymer matrix, $\alpha$-amino-$\omega$-thiol terminated poly(acrylic acid), was employed for precipitation of CP. The acrylic acid group acts as a polyanionic template. The thiol terminus of the polymer was used to produce self-assembled monolayers (SAMs) on Au electrodes and the amine terminus was employed for immobilization of biomolecules. In an enzymeamplified sandwich type immunosensor, the polyaniline (PANI) produced enzymatically is attracted by the electrostatic force of the matrix polymer. The precipitated PANI was characterized by electrochemical methods.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.2905-2908
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• 2009

Immuno-sensing for high accurate and selective sensing was performed by fluorescence spectroscopy and surface plasmon resonance (SPR), respectively. Engineered assembly of two fluorescent quantum dots (QDs) with bovine serum albumin (BSA) and anti-BSA was fabricated in PBS buffer for fluorescence analysis of fluorescence resonance energy transfer (FRET). Furthermore, the same bio-moieties were immobilized on Au plates for SPR analysis. Naturally-driven binding affinity of immuno-moieties induced FRET and plasmon resonance angle shift in the nanoscale sensing system. Interestingly, the sensing ranges were uniquely different in two systems: e.g., SPR spectroscopy was suitable for highly accurate analysis to measure in the range of 10$^{-15{\sim}-10$ng/mL while the QD fluorescent sensing system was relatively lower sensing ranges in 10$^{-10{\sim}-6$ng/mL. However, the QD sensing system was larger than the SPR sensing system in terms of sensing capacity per one specimen. It is, therefore, suggested that a mutual assistance of FRET and SPR combined sensing system would be a potentially promising candidate for high accuracy and reliable in situ sensing system of immune-related diseases.