Jongwon Park

Color Intensity Method for Hydrogel Oxygen Sensor Array

The oxygen imaging technique to obtain a 2-D distribution is a convenient method because it does not require individual addressing of each sensing element in a sensor array. Until recently, color charge coupled devices (CCDs) have rarely been used for oxygen imaging in spite of usefulness for analyzing the spectral content of images. In this work, a color CCD camera was used for luminescence intensity imaging. Two methods of color intensity analysis are investigated and compared. The first method is to analyze the total Red-Green-Blue (RGB) color intensity of the original color image. The second method involves extracting the red color element to enhance the sensitivity of oxygen measurement. Both commercial RedEye oxygen sensor patches and lab-made photopatterned hydrogel (polyethylene glycol) sensor arrays were used to verify these methods. The linearity and sensitivity of oxygen detection based on the red intensity analysis was improved to those of spectrometric measurement and total color intensity analysis. This method also has potential applications in lifetime imaging, multi-analyte detection, and simultaneous structural and functional imaging of biological systems.

Expression Analysis of Lily Type Lectin Isotypes in the Rock Bream, Oplegnathus fasciatus: in the Tissue, Developmental Stage and Viral Infection.

ABSTRACT Lectins belong to the pattern-recognition receptors (PRRs) class and play important roles in the recognition and elimination of pathogens via the innate immune system. Recently, it was reported that lily-type lectin-1 is involved when a pathogen attacks in the early immune response of fish. However, this study is limited to information that the lectin is involved in the innate immune response against viral infection. In the present study, the lily-type lectin-2 and -3 of Oplegnathus fasciatus (OfLTL-2 and 3) have been presented to be included B-lectin domain and two D-mannose binding sites in the amino acid sequence that an important feature for the fundamental structure. To investigate the functional properties of OfLTLs, the tissue distribution in the healthy rock bream and temporal expression during early developmental stage analysis are performed using quantitative real-time PCR. OfLTL-2 and 3 are predominantly expressed in the liver and skin, but rarely expressed in other organ. Also, the transcripts of OfLTLs are not expressed during the early developmental stage but its transcripts are increased after immune-related organs which are fully formed. In the challenge experiment with RBIV (rock bream iridovirus), the expression of OfLTLs was increased much more strongly in the late response than the early, unlike previously known. These results suggest that OfLTLs are specifically expressed in the immune-related tissues when those organs are fully formed and it can be inferred that the more intensively involved in the second half to the virus infection.

An Oxidase-Based Electrochemical Fluidic Sensor with High-Sensitivity and Low-Interference by On-Chip Oxygen Manipulation

Utilizing a simple fluidic structure, we demonstrate the improved performance of oxidase-based enzymatic biosensors. Electrolysis of water is utilized to generate bubbles to manipulate the oxygen microenvironment close to the biosensor in a fluidic channel. For the proper enzyme reactions to occur, a simple mechanical procedure of manipulating bubbles was developed to maximize the oxygen level while minimizing the pH change after electrolysis. The sensors show improved sensitivities based on the oxygen dependency of enzyme reaction. In addition, this oxygen-rich operation minimizes the ratio of electrochemical interference signal by ascorbic acid during sensor operation (i.e., amperometric detection of hydrogen peroxide). Although creatinine sensors have been used as the model system in this study, this method is applicable to many other biosensors that can use oxidase enzymes (e.g., glucose, alcohol, phenol, etc.) to implement a viable component for in-line fluidic sensor systems.

Versatile Optochemical Quantification with Optical Mouse

There is an ever increasing need for simple, low-cost instruments for ubiquitous medical and environmental measurements in conjunction with networks and Internet-of-things. This work demonstrates that the optical mouse, one of the most common optoelectronic computer peripherals, can be used for chemical quantification. Particularly, we explore the feasibility of using the preassembled optical platform of mouse for oxygen and pH quantification. The image sensor and the light-emitting diode (LED) serve as photodetector and excitation/illumination light source, respectively, while the preinstalled microoptics (e.g., lens and waveguide) provide a fixed optical arrangement convenient for sample analysis. This novel, cost-effective approach demonstrates the potential application of optical mouse for bioanalytical devices in conjunction with commercial sensor strips or simple microfluidic elements. This is one viable option for seamless integration of bioanalytical capability into existing personal computers and associate networks without significant additional hardware.

Expression Analysis of Interferon-Stimulated Gene 15 in the Rock Bream Oplegnathus fasciatus against Rock Bream Iridovirus (RSIV) Challenge

ABSTRACT Interferon-stimulated gene 15 (ISG15) is known to interfere with viral replication and infection by limiting the viral infection of cells. Interferon-stimulated gene 15 (ISG15) interferes with viral replication and infectivity by limiting viral infection in cells. It also plays an important role in the immune response. In this study, tissue-specific expression of ISG15 in healthy rock bream samples and spatial and temporal expression analysis of rock bream ISG15 (RbISG15) were performed following rock bream iridovirus (RSIV) infection. RbISG15 expression was significantly higher in the eye, gill, intestine, kidney, liver, muscle, spleen, and stomach, but low in the brain. There were particularly high levels of expression in the liver and muscle. RbISG15 expression was also examined in several tissues and at various times following RSIV infection. ISG15 expression increased within 3 h in the whole body and decreased at 24 h after infection. In addition, temporal expression of several tissues following RSIV infection showed a similar pattern in the muscle, kidney, and spleen, increasing at 3 h and decreasing at 72 h. These results suggest that ISG15 plays an important role in the immune response of rock bream. Overall, this study characterizes the response of RbISG15 following RSIV infection.

Optical mouse as pH analyzer

Optical sensor for chemical analysis is a growing technology since it offers many advantages. The goal of this research is to achieve pH sensing using low-cost optoelectronics devices such as optical mouse, which consist of photodetector, light source and pre-installed optics. Colorimetric pH measurements were done with the optical mouse utilizing commercial pH test strips. All images were taken with an built-in image sensor of optical mice and several factors for image acquisition such as optical filter, light source and gray scale image analysis were evaluated. pH evaluation with spectrophotometer was also conducted and compared with data obtained with mice in a pH range between 2-12 providing reliable results.

Optofluidic biosensors based on color imaging

A color CCD (charge-coupled device) camera is used as a chemical detector to quantify fluorescence emission intensities from two kinds of optofluidic device platforms. The fluorophores responsive to oxygen are immobilized in photo-patternable hydrogel matrices. The first device is a hydrogel sensor array formed within a commercial silicone elastomer imaging chamber. The second one involves a double-chamber fluidic device composed of a permeable membrane layer and dry film photoresist layers. The results suggest that digital color imagers, in combination with a simple color separation method, can serve as the high quality chemical detectors for fluidic biosensors and biological culture platforms.

A fluidic system for photometric dissolved oxygen measurements with enhanced sensitivity

A new method of color pixel intensity analysis to obtain an oxygen concentration is presented in this research. Until recently, color charge coupled devices (CCDs) have rarely been used for oxygen imaging in spite of its usefulness for analyzing the spectral content of images. The proposed new method involves extracting the red color element to enhance oxygen-related information and eliminate distorted green color information from the color images of the sensors. A commercial RedEyeTM oxygen sensor patch was used to verify this method. The linearity and sensitivity of oxygen detection based on the red intensity analysis was improved to those of spectrometric measurement and total color intensity analysis. This method also has potential applications in other luminescence sensors and simultaneous structural and functional imaging of biological systems.

Process development for waveguide chemical sensors with integrated polymeric sensitive layers

Due to the proper optical property and flexibility in the process development, an epoxy-based, high-aspect ratio photoresist SU-8 is now attracting attention in optical sensing applications. Manipulation of the surface properties of SU-8 waveguides is critical to attach functional films such as chemically-sensitive layers. We describe a new integration process to immobilize fluorescence molecules on SU-8 waveguide surface for application to intensity-based optical chemical sensors. We use two polymers for this application. Spin-on, hydrophobic, photopatternable silicone is a convenient material to contain fluorophore molecules and to pattern a photolithographically defined thin layer on the surface of SU-8. We use fumed silica powders as an additive to uniformly disperse the fluorophores in the silicone precursor. In general, additional processes are not critically required to promote the adhesion between the SU-8 and silicone. The other material is polyethylene glycol diacrylate (PEGDA). Recently we demonstrated a novel photografting method to modify the surface of SU-8 using a surface bound initiator to control its wettability. The activated surface is then coated with a monomer precursor solution. Polymerization follows when the sample is exposed to UV irradiation, resulting in a grafted PEGDA layer incorporating fluorophores within the hydrogel matrix. Since this method is based the UV-based photografting reaction, it is possible to grow off photolithographically defined hydrogel patterns on the waveguide structures. The resulting films will be viable integrated components in optical bioanalytical sensors. This is a promising technique for integrated chemical sensors both for planar type waveguide and vertical type waveguide chemical sensors.