Young-Soo Sohn

Detection of Amyloid-β42 Using a Waveguide-Coupled Bimetallic Surface Plasmon Resonance Sensor Chip in the Intensity Measurement Mode

The waveguide-coupled bimetallic (WcBiM) surface plasmon resonance (SPR) chip had been utilized in the intensity interrogation detection mode to detect amyloid-β42 (Aβ42), a biomarker of the Alzheimer disease. The SPR reflectance curve of the WcBiM chip has the narrower full-width-at-half-maximum (FWHM) compared with the SPR reflectance curve of the conventional gold (Au) chip, resulting in the steeper gradient. For the enhancement of resolution, the light source was fixed at an angle where the slope of the reflectance curve is the steepest, and the change in the reflectance was monitored. For the detection of Aβ42, the antibody of Aβ42 (anti-Aβ42) was immobilized on the WcBiM SPR chip using the self-assembled monolayer. The SPR responses, the average changes in the reflectance to the Aβ42 at the concentrations of 100 pg/ml, 250 pg/ml, 500 pg/ml, 750 pg/ml, 1,000 pg/ml, and 2,000 pg/ml were 0.0111%, 0.0305%, 0.0867%, 0.1712%, 0.3021%, and 0.5577%, respectively, for the three replicates. From linear regression analysis, the calibration curve indicated that the SPR response had a linear relation with Aβ42 with the concentration in the range of 100 pg/ml to 2,000 pg/ml. A control experiment showed the anti-Aβ42-modified surface of the WcBiM chip had a high specificity to Aβ42. Thus, the enhanced resolution by utilizing the WcBiM SPR chip in the intensity interrogation detection mode aids the diagnosis of the Alzheimer disease by detecting the Aβ42 around the criteria concentration (500 pg/ml) without any labeling.

Site-directed immobilization of antibody using EDC-NHS-activated protein A on a bimetallic-based surface plasmon resonance chip

Abstract. The characteristics of a waveguide-coupled bimetallic surface plasmon resonance (WcBiM SPR) sensor using (3-dimethylaminopropyl)-3-ethylcarbodiimide(EDC)-N-hydroxysuccinimide(NHS)-activated protein A was investigated, and the detection of IgG using the EDC-NHS-activated protein A was studied in comparison with protein A and a self-assembled monolayer (SAM). The WcBiM sensor, which has a narrower full width at half maximum (FWHM) and a steeper slope, was selected since it leads to a larger change in the reflectance in the intensity detection mode. A preparation of the EDC-NHS-activated protein A for site-directed immobilization of antibodies was relative easily compared to the engineered protein G and A. In antigen–antibody interactions, the response to IgG at the concentrations of 50, 100, and 150  ng/ml was investigated. The results showed that the sensitivity of the WcBiM sensor using the EDC-NHS-activated protein A, protein A, and SAM was 0.0185 [%/(ng/ml)], 0.0065 [%/(ng/ml)], and 0.0101 [%/(ng/ml)], respectively. The lowest detectable concentrations of IgG with the EDC-NHS-activated protein A, protein A, and SAM were 4.27, 12.83, and 8.24  ng/ml, respectively. Therefore, the increased sensitivity and lower detection capability of the WcBiM SPR chip with the EDC-NHS-activated protein A suggests that it could be used in early diagnosis where the trace level concentrations of biomolecules should be detected.

Enhancing performance of a miniaturized surface plasmon resonance sensor in the reflectance detection mode using a waveguide-coupled bimetallic chip

The characteristics of a waveguide-coupled bimetallic (WcBiM) chip in a miniaturized surface plasmon resonance (SPR) sensor and its detection capability for a low molecular weight biomolecule were investigated. The configuration of the WcBiM chip was gold (Au)/waveguide (ZnS-SiO2)/silver (Ag). In the intensity measurement mode, the sensitivity could be improved by reducing the full width at half maximum (FWHM) of the reflectance curve. The FWHM of the WcBiM chip is narrower than that of the Au chip, which suggests that the slope of the reflectance curve for the WcBiM chip is steeper. In order to generate enhanced resolution, the reflectance should be monitored at the specific angle where the slope is the steepest in the reflectance curve. For the detection of biotin that is a low molecular weight biomolecule, streptavidin was formed on the SPR sensor chip surface. The response of the SPR to biotin at various concentrations was then acquired. The sensitivities of the WcBiM chip and the Au chip were 0.0052%/(ng/ml) and 0.0021%/(ng/ml), respectively. The limit of detection of the biotin concentration for both the WcBiM and Au chips was calculated. The values were 2.87 ng/ml for the WcBiM chip and 16.63 ng/ml for the Au chip. Enhancement of the sensitivity in the intensity detection mode was achieved using the WcBiM chip compared with the Au chip. Therefore, sufficient sensitivity for the detection of a disease-related biomarker is attainable with the WcBiM chip in the intensity measurement mode using a miniaturized SPR sensor.

Correlation between blood glucose and hematocrit: A new estimation methodology

The estimation of hematocrit in the enzyme and mediator configured blood glucose monitoring electrochemical strips is proposed conceptualizing an innovative data mining methodology. This methodology demonstrate assimilating the peak current (IP), and time (tP) to achieve the peak current of the amperometry; as a coordinate point in the indigenously nomenclated HMM (Hematocrit Monitoring Method) IP-tP Array. The array consists of constructing a matrix (9× 7 matrix) that could be extended to a matrix of appreciable size within the computational limitations. The computational results of hematocrit estimation are precise in the experimental range of 10–50% hematocrit volume. A mathematical model for the transient current emanating from an electrochemical strip is also formulated corroborating our experimental results.

Enhancing resolution of a miniaturized surface plasmon resonance sensor using bimetallic-based chip

In this study, a performance of a waveguide coupled bimetallic (WCBiM) chip in a miniaturized surface plasmon resonance (SPR) sensor in a reflectance detection mode was investigated by comparison with a conventional gold (Au) chip. The WCBiM chip makes sharper slope in the SPR curve than conventional Au chip. The detection abilities of both sensor chips were tested by monitoring an interaction between streptavidin and biotin (very low molecular weight). Firstly, an incident light was fixed at an angle which was steepest slope in the scanned the SPR curve; then, the output signal was measured at fixed angle. The streptavidin diluted to 50 μg/ml in the phosphate buffered saline (PBS) was injected into a fluidic module of the SPR sensor. Next, the biotin diluted to 50 ng/ml, 100 ng/ml, 150 ng/ml and 200 ng/ml in the PBS were injected into the sensor. In results, the reflectance increments of the lowest concentration of the biotin (50 ng/ml) using the WCBiM chip and Au chip were 0.11 % and 0.04 %, respectively. Experimental results showed that detection ability of the WCBiM chip was about three times larger than that of conventional Au chip. In conclusion, the miniaturized SPR sensor in the reflectance detection mode using the WCBiM chip was expected to detect the biomolecules at trace level concentration or low molecular weight with high resolution.

The growth of patterned carbon nanotube arrays on Si pillar arrays

ABSTRACT Vertically aligned carbon nanotube (CNT) arrays were prepared using dc plasma-enhanced chemical vapor deposition (DC-PECVD). For uniform growth of the vertically aligned CNTs in the patterned array, the conventional photolithography technique and oblique angle deposition technique were utilized. The pattern of the CNTs was defined by the silicon pillar configuration fabricated by the conventional photolithography. The characteristics of the vertically aligned CNTs were dependent on conditions of catalyst metals using the oblique angle deposition technique. Using the conventional photolithography and oblique angle deposition techniques, the well-defined and well-separated CNT pattern arrays were successfully grown. In order to improve the electrical properties of the grown CNTs, nitrogen (N) was doped using NH3. This low-cost and simplified fabricating method would be an effective growth process for the CNT array which can be used in field emitter applications.

Effects of Annealing Temperature on Parylene-C Films Formed by Chemical Vapor Condensation Method

In this study, parylene-C films were deposited using vertically aligned-chemical vapor condensation (CVC) method and effects of post-annealing were investigated. The comparison results for as-deposited and post-annealed samples showed that the structural properties changed gradually with varying annealing temperature, while optical properties and surface morphology of the films seldom changed. The crystallinity, crystallite size, and d-spacing were changed from 60 to 87.2%, from 6.83 to 15.6 nm, and from 6.41 to 6.26 Å, respectively. The value of oxygen transmission rate (OTR) for the films was changed gradually from 3.22 to 1.53 cc/m2•day after annealing process. However, the values of transmittance and surface roughness were 90% in the visible-near IR region and 5 nm without reference to annealing temperature. Consequently, the crystallization of parylene-C films was one of major effects without the change of optical properties and surface morphology after annealing process, and we believed that the enhancement of crystallinity caused to improve the property of OTR for parylene-C films.

Directional immobilization of antibody in a SPR sensor using EDC-activated protein A

The EDC-activated protein A has been utilized to directionally immobilize anti-IgG in a miniaturized SPR sensor to enhance IgG detection capability. The SPR sensor chips modified by a self-assembled monolayer (SAM), protein A and the EDC-activated protein A as the linkage layer were compared by the SPR sensor. The SAM was formed on the Au (gold) surface sensor chip by immersing it in the SAM solution. The protein A was formed by injecting their solution to the Au chip. Thirdly, for the EDC-activated protein A, chemical procedure was carried out for the reactable surface of the Au chip. Anti-IgG, bovine serum albumin (BSA) and IgG (50 ng/ml, 100 ng/ml, 150 ng/ml) had been sequently injected into the SPR sensor. In results, the signal of the anti-IgG immobilized by the SAM was the largest increment among three linkage layers. However, the SPR sensor chip modified by EDC-activated protein A showed the highest sensitivity to IgG. From these results, we concluded that the SPR sensor using the EDC-activated protein A can be used to detect biomolecules with trace level concentration for early diagnosis of disease.

Modeling and Design Consideration of a Simple Hybrid Solar Energy Conversion System

Modeling of a simple hybrid photovoltaic-thermoelectric system has been presented to find optimum condition for higher conversion efficiency of solar energy. In this modeling, not only reflectance but also thermal radiation loss at the front side of the photovoltaic cell was taken into account. The efficiency of the thermoelectric generator was never higher than that of the photovoltaic cell. The influence of the material properties of the hybrid system on the overall efficiency was investigated. For practical use it should bear in mind that the heat sink should maintain low temperature on the cold side of the thermoelectric generator.

Characterization of a-Si:H TFTs with Various Phosphorus Concentrations in a-SiN:H Layer

Characteristics of hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) with various phosphorus doping concentrations in a-SiN:H layer have been investigated. The a-Si:H TFTs with a heterostructure of the phosphorus-contained a-SiN:H and intrinsic a-Si:H layers have been fabricated by a plasma enhanced chemical vapor deposition using SiH4, PH3, and NH3 gases. The mobility, the threshold and the surface roughness of the devices have been investigated and compared with the conventional amorphous silicon thin film transistors.