• Journal of Microbiology and Biotechnology
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• v.18 no.10
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• pp.1695-1700
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• 2008

An immunosensor based on surface plasmon resonance (SPR) with enhanced performance was developed through a mixed self-assembled monolayer. A mixture of 16-mercaptohexadecanic acid (16-MHA) and 1-undecanethiol with various molar ratios was self-assembled on gold (Au) surface and the carboxylic acid groups of 16-MHA were then coordinated to Zn ions by exposing the substrate to an ethanolic solution of $Zn(NO_3)_2\cdot 6H_2O$. The antibody was immobilized on the SPR surface by exposing the functionalized substrate to the desired solution of antibody in phosphate-buffered saline (PBS) molecules. The film formation in series was confirmed by SPR and atomic force microscopy (AFM). The functionalized surface was applied to develop an SPR immunosensor for detecting human serum albumin (HSA) and the estimated detection limit (DL) was 4.27 nM. The limit value concentration can be well measured between ill and healthy conditions.

• Journal of Sensor Science and Technology
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• v.29 no.2
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• pp.118-122
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• 2020

This paper proposes a specific sensor-design strategy and the possibility of improving the sensing performance, which can be obtained by replacing part of the existing plasmonic sensor based on the Kretschmann configuration method with an effective refractive-index layer. By replacing the metal layer with an effective refractive-index layer composed of gold and the material to be sensed, an improvement in the detection performance, accompanied by an increase in the sensed incident angle, is observed, and the gold-composition ratio that demonstrates the best result is presented. Subsequently, an increase in the sensed incident angle generated in the previous step can be suppressed by randomly etching a portion of the prism adjacent to the metal layer in a sub-wavelength scale. Finally, this study analyzes the optimization of the metal-layer thickness in a given sensor structure. An effective refractive thin-film surface plasmon resonance sensor design that can achieve optimal sensing performance is then proposed.

• Korean Journal of Materials Research
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• v.26 no.8
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• pp.417-421
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• 2016

We improve the energy conversion efficiency (ECE) of a dye sensitized solar cell (DSSC) by preparing a working electrode (WE) with localized surface plasmon resonance (LSPR) by inducing Au thin films with thickness of 0.0 to 5.0 nm, deposited via sputtering. Field emission scanning electron microscopy and atomic force microscopy were used to characterize the microstructure of the blocking layer (BL) of the Au thin films. Micro-Raman measurement was employed to confirm the LSPR effect, and a solar simulator and potentiostat were used to evaluate the photovoltaic properties, including the impedance and the I-V of the DSSC of the Au thin films. The results of the microstructural analysis confirmed that nano-sized Au agglomerates were present at certain thicknesses. The photovoltaic results show that the ECE reached a value of 5.34% with a 1-nm thick-Au thin film compared to the value of 5.15 % without the Au thin film. This improvement was a result of the increase in the LSPR of the $TiO_2$ layer that resulted from the Au thin film coating. Our results imply that the ECE of a DSSC may be improved by coating with a proper thickness of Au thin film on the BL.

• Journal of Sensor Science and Technology
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• v.28 no.6
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• pp.355-359
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• 2019

Exosomes, known as nanoscale extracellular vesicles in the range of 30-150 nm, are known to contain clinically significant information. However, there is still insufficient information on exosomal membrane proteins for cancer diagnosis. In this work, we investigated the characteristics of the membrane proteins of exosomes shed by cultured breast cancer cell lines using a surface plasmon resonance (SPR) spectroscopy and pre-activated alkanethiols modified sensor chips. The antibodies of breast cancer biomarkers such as MCU-16, EpCAM, CD24, ErbB2, and CA19-9 were immobilized on the pre-activated alkanethiols surfaces without any activation steps. The purified exosomes were loaded onto each antibody surface. The affinity rank of the antibody surfaces was decided by the relative capture efficiency factors for the exosomes. In addition, an antibody with a relative capture efficiency close to 100% was tested with exosome concentration levels of 10⁴/µl, 10⁵/µl, and 10⁶/µl for quantitative analysis.

• Journal of Microbiology and Biotechnology
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• v.17 no.7
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• pp.1191-1197
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• 2007

The detection and kinetics of mucosal pathogenic bacteria binding on polysaccharide ligands were studied using a surface plasmon resonance biosensor. The kinetic model applied curve-fitting to the experimental surface plasmon resonance sensorgrams to evaluate the binding interactions. The kinetic parameters for the mucosal pathogenic bacteria (Pseudomonas aeruginosa, Pseudomonas fluorescens, Serratia marcescens) with the alginate ligand were determined from a kinetic model. In addition, the binding interactions of the mucosal pathogenic bacteria with polysaccharide binding pairs (Pseudomonas aeruginosa/alginate, Streptococcus pneumoniae/pneumococcal polysaccharide, Staphylococcus aureus/pectin) were also compared with their kinetic parameters. The rate constants of association for Pseudomonas aeruginosa with the alginate ligand were higher than those for Pseudomonas fluorescens. Serratia marcescens had no detectable interaction with the alginate ligand. The adhesion affinity of Pseudomonas aeruginosa with alginate was higher than that for the other binding pairs. The binding affinities of the pathogenic bacteria with their own polysaccharide were higher than that of Staphylococcus aureus with pectin. Measuring the contact angle was found to be a feasible method for detecting binding interactions between analytes and ligands.

• Rapid Communication in Photoscience
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• v.2 no.2
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• pp.46-51
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• 2013

This study reports a fiber-optic sensor detecting biomolecule by simultaneously monitoring localized surface plasmon resonance (LSPR) from gold nanoparticles (Au NPs) of ca. $50{\pm}5$ nm attached on one end of optical fiber and surface enhanced Raman scattering (SERS) of the reporter molecules adsorbed on the gold surfaces as an additional sensing tool. The sensor was fabricated by immobilizing Au NPs on one end of an optical fiber by chemical reaction. LSPR and SERS signals of the sensor were measured using various refractive indices solutions. Finally, the sensor was applied to observe real-time LSPR sensor-gram and SERS spectra of the reporter molecule of 4-aminothiphenol during the antibody-antigen reaction of interferon-gamma (IFN-${\gamma}$) as a proof-concept experiment of biological applications.

• Journal of Sensor Science and Technology
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• v.26 no.6
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• pp.402-407
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• 2017

Characteristics of various material surface plasmon resonance (SPR) chips were investigated in angular interrogation mode and intensity interrogation mode. Among five metals, silver (Ag), gold (Au), copper (Cu), chromium (Cr) and titanium (Ti), three metals, Ag, Au and Cu were paid attention to since their characteristics can be easily analyzed in angular interrogation mode by investigating the change of their reflectance curves according to refractive index change from 1.331 to 1.335. Most of SPR chips with various configurations showed the similar property in angular interrogation mode. The application of the SPR chip made of Ag, Au and Cu or their combinations depends on their reflectance properties. In intensity interrogation mode, the operation range may be limited since the variation of the intensity was not linearly related to refractive index change ranging from 1.331 to 1.335. However, the SPR chip containing high ratio of Ag may be applicable to high sensitive detection due to their sharp reflectance curves in intensity interrogation mode.

• Journal of Biosystems Engineering
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• v.35 no.2
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• pp.116-123
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• 2010

Rapid detection of foodborne pathogens has been a major challenge for the food industry. Salmonella contamination is well known in all foods including pasteurised milk. The possibility of specific detection of Salmonella Enteritidis by surface plasmon resonance (SPR) biosensor was explored using a commercially available portable SPR sensor. Self assembly technique was adopted to immobilize anti-Salmonella antibodies on the gold sensing surface of the SPR sensor. The concentration of polyclonal antibody for use in the SPR biosensor was chosen to 1.0 mg/mL. Experiments were conducted at near real-time with results obtained for one SPR biosensor assay within 1 hour. The limit of detection for Salmonella Enteritidis was determined to be $10^6$ CFU/mL in both PBS buffer and milk samples. The assay sensitivity was not significantly affected by milk matrix. Our results showed that it would be possible for employing the SPR biosensor to detect Salmonella Enteritidis in near real-time.

• 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.

• Korean Journal of Veterinary Service
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• v.34 no.1
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• pp.1-4
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• 2011

A surface plasmon resonance imaging (SPRI) assay was developed for measuring porcine circovirus type 2 (PCV2) antibody using a recombinant capsid protein as an antigen. The diagnostic potential of SPRI for detecting antibodies to the PCV2 capsid protein was compared with that of a conventional enzyme-linked immunosorbent assay (ELISA) using 70 pig serum samples taken from 6 pig farms. There was a strong positive correlation between the SPRI and ELISA (n = 70, r = 0.911, P<0.01). Therefore, this recombinant capsid protein can be used as an antigen for serological studies, and the SPRI, a label-free and high-throughput method, is expected to be a valuable tool in the serodiagnosis of PCV2 infection.