• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2651-2654
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• 2009

In borohydride-protected nanosilvers in laponite sol, the silver particles aggregate to form short chains and a dumbbell shape. The $^{1}H$ NMR measurements in this study represent, to our knowledge, the first observation of proton resonances of borohydride-protected nanosilvers in aqueous solution. Borohydride on nanosilver can be exchanged with 11-mercaptoundecanoic acid (MUA) or trioctylphosphine (TOP). Transmission electron microscopy and UV-Vis spectroscopy data show that the number of aggregated silver nanoparticles decreases upon addition of aforementioned ligands due to the formation of silver MPCs (monolayer-protected clusters). Adsorption of MUA or TOP on nanosilver is confirmed through the observation of broad proton resonances of MPCs in $^{1}H$ NMR spectra.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.97-102
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• 2003

Multi-channel images of 11-MUA(11-Mercaptoundecanoic acid) and 11-MUOH(11-Mercaptoundecanol) self-assembled monolayers were obtained by using two-dimensional surface plasmon resonance (SPR) absorption. The patterning process was simplified by exploiting direct photo-oxidation of thiol bonding (photolysis) instead of conventional photolithography. Sharper images were resolved by using a white light source in combination with a narrow bandpass filter in the visible region, minimizing the diffraction patterns on the images. The line profile calibration of the image contrast caused by different resonance conditions at each point on the sensor surface (at a fixed incident angle) enables us to discriminate the monolayer thickness in nanometer scale. Furthermore, there is no signal degradation such as photo bleaching or quenching, which are common in the detection methods based on fluorescence.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.4
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• pp.227-232
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• 2003

A self-assembled monolayer of protein G was fabricated to develop an immunosensor based on surface plasmon resonance (SPR), thereby improving the performance of the antibodybased biosensor through immobilizing the antibody molecules (lgG). As such, 11-mercaptoundecanoic acid (11-MUA) was adsorbed on a gold (Au) support, while the non-reactive hydrophilic surface was changed through substituting the carboxylic acid group (-COOH) in the 11-MUA molecule using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrocholide (EDAC). The formation of the self-assembled protein G layer on the Au substrate and binding of the antibody and antigen were investigated using SPR spectroscopy, while the surface topographies of the fabricated thin films were analyzed using atomic force microscopy (AFM). A fabricated monoclonal antibody (Mab) layer was applied for detecting E. coli O157:H7. As a result, a linear relationship was achieved between the pathogen concentration and the SPR angle shift, plus the detection limit was enhanced up to 10$^2$ CFU/mL.

• Journal of Microbiology and Biotechnology
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• v.16 no.8
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• pp.1169-1173
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• 2006

Imaging ellipsometry (IE) for detection of binding of Escherichia coli O157:H7 (E. coli O157:H7) to an immunosensor is reported. A protein G layer, chemically bound to a self-assembled layer of 11-mercaptoundecanoic acid (11-MUA), was adopted for immobilization of monoclonal antibody against E. coli O157:H7 (Mab). The immobilization of antibody was investigated using surface plasmon resonance. To fabricate antibody spots on a gold surface, protein G solution was spotted onto the gold surface modified with an 11-MUA layer, followed by immobilizing Mab on the protein G spot. Ellipsometric images of the protein G spot, the Mab spot, and Mab spots with binding of E. coli O157:H7 in various concentrations were acquired using the IE system. The change of mean optical intensity of the Mab spots in the ellipsometric images indicated that the lowest detection limit was $10^3$CFU/ml for E. coli O157:H7. Thus, IE can be applied to an immunosensor for detection of E. coli O157:H7 as a detection method with the advantages of allowing label-free detection, high sensitivity, and operational simplicity.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.2
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• pp.112-116
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• 2003

An immunosensor based on surface plasmon resonance (SPR) onto a protein G layer by Self-assembly technique was developed for detection of Legionella pneumophila. The protein G layer by self-assembly technique was fabricated on a gold (Au) surface by adsorbing the 11-mercaptoundecanoic acid (MUA) and an activation process for the chemical binding of the free amino (-NH$_2$) of protein G and 11-(MUA) using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDAC) in series. The formation of the protein G layer by self-assembly technique on the Au Substrate and the binding of the antibody and antigen in series were confirmed by SPR spectroscopy. The Surface topographies of the fabricated thin films on an Au substrate were also analyzed by using an atomic force microscope (AFM). Consequently, an immunosensor for the detection of L. pneumophila using SPR was developed with a detection limit of up to 10$^2$CFU per mL.

• Journal of Microbiology and Biotechnology
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• v.12 no.5
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• pp.780-786
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• 2002

An immunosensor based on surface plasmon resonance (SPR) with a self-assembled protein G layer was developed for the detection of Escherichia coli O157:H7. A self-assembled protein C layer on a gold (Au) surface was fabricated by adsorbing the mixture of 11-mercaptoundecanoic acid (MUA) and hexanethiol at various molar ratios and by activating chemical binding between free amine (-$NH_2$) of protein G and 11-(MUA) using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC) in series. The formation of a self-assembled protein G layer on an Au substrate and the binding of the antibody and antigen in series were confirmed by SPR spectroscopy. The surface morphology analyses of the self-assembled protein G layer on the Au substrate, monoclonal antibody (Mab) against E. coli O157:H7 which was immobilized on protein G, and bound E. coli O157:H7 extracts on Immobilized Mab against E. coii O157:H7 were performed by atomic force microscopy (AFM). The detection limit of the SPR-based immunosensor for E. coli O157:H7 was found to be about $10^4$ cells/ml.