Kyeong-Sik Shin

Single cell assay on cd-like lab chip using centrifugal single cell trap

This paper reports a single cell assay in compact disc (CD)-like lab chip with trapped single cells by centrifugal force. The main propose of this study was realization of cell assay on chip with the advantage of excluding the paracrine effect of adjacent cells. The channel in CD-like lab chip has many pitfalls at the outer side, in which cells were trapped respectively. The trap was able to fix each cell and the chemicals were treated by centrifugal pumping. Parameters that affects the trapping of a cell were the size of cells, the structure of micro-pattern, the magnitude of centrifugal force and the duration time. The trap ratio of cells was around 80% at optimal condition. Cytotoxicity and apoptosis test was done in CD and it was compared with conventional method to see the effect of single cell assay. Cytotoxicity was tested by the treatment of parformaldehyde and the apoptosis test was done by illumination UV light. The results of both assays indicated the overall trend of single assay in chip and conventional assay was same. However, apoptosis assay showed that the survival rate of single cell assay in chip was higher than that of conventional assay. Although it is still unclear that the result was caused by the effect of crowded cells, this single cell assay platform could be one of valuable tools in single cell assay.

Development of Novel Implantable Intraocular Pressure Sensors to Enhance the Performance in in vivo Tests

In this paper, we proposed a dual-mode intraocular pressure (IOP) sensor that has two separated diaphragms to conduct the changes of inductance and capacitance, and we compared the sensors performance with that of the conventional single variable capacitive sensor (single-mode sensor). Both mode sensors were used to monitor the pressure in in vitro tests with multiple media and in in vivo tests with rabbits. First, we demonstrated that the sensitivities of two types of sensors tended to be different for in vivo and in vitro tests. This was the first known attempt to show changes in the sensitivity and responsivity of IOP sensors in in vivo tests. The sensitivity and phase dip of the dual-mode sensor exceeded that of the single-mode sensor, irrespective of medium due to isolation of capacitive sensor from medium. In this paper, we have provided the equations that were used to evaluate the improvement in sensitivity, and we have shown the coincidence with in vitro and in vivo tests. Based on the results we achieved, we believe that the dual-mode sensor is more feasible for use as an IOP sensor in in vivo tests, because its responsivity and sensitivity are superior to those of the conventional sensors.

Parasitic Bipolar Junction Transistors in a Floating-Gate MOSFET for Fluorescence Detection

In this letter, we examined whether the parasitic bipolar junction transistors (BJTs) in the MOSFET fabricated by the standard CMOS process can play a role as a fluorescence detector. To suppress the action of two vertical parasitic BJTs, the gate and n-well were tied in the parasitic BJTs, and the body node was connected to the drain. The proposed device was compared with the inherent and the parasitic diodes in the MOSFET. It had 100 times higher photocurrents than the diodes in the MOSFET. In addition, it was applied for the detection of the fluorescent signal, and could detect near 10 nM of Alexa 546. Therefore, CMOS-process-compatible parasitic BJTs can be used as a photodetector in an integrated fluorescence detector.

Effects of inner materials on the sensitivity and phase depth of wireless inductive pressure sensors for monitoring intraocular pressure

In this research, we developed wireless, inductive, pressure sensors with high sensitivity and investigated the effects of the inner materials (copper or ferrite) on the performance of the sensors. The proposed sensor is comprised of two parts, i.e., the top and the bottom parts. The top part includes a micro coil and a capacitor for the wireless transfer of data, and the bottom part includes the inner materials and a thick or thin flexible membrane to induce changes in the inductance. An anchor is used to assemble the top and bottom parts. The behavior of the sensor with copper was based on the eddy current effect, and, as the pressure increased, its resonance frequency increased, while its phase depth decreased exponentially. The principle of the sensor with ferrite was related to the effective permeability between a ferrite and a coil, and its response was the opposite of that with copper, i.e., as the pressure increased, the resonance frequency decreased linearly, and the phase depth increased linearl...

A miniaturized fluorescence detection system with an integrated organic light emitting diode

The organic light emitting diode (OLED) is proposed as a novel source in the microchip because it has ideal merits (various wavelengths, thin-film structure and overall emitting) for the integration. In this paper, we fabricated finger-type PIN photodiodes for the fluorescence detection and an advanced microchip with an integrated OLED. The finger-type in the diode design extended the depletion region and its internal resistance was reduced about 32% than that of a rectangular-type. The photodiodes had 0.1 nA leakage current and 8,720 sensitivity (I/sub light//I/sub dark/) at -1 V bias. The interference filter with 32 layers (SiO/sub 2/, TiO/sub 2/) was directly deposited on the photodiode. Deposited OLEDs increased the excitation efficiency and extremely simplified the integration process. The monolithically integrated microchip had a high sensitivity of 0.256 nA//spl mu/M and the LOD (limit of detection, S/N =2) of 0.01 /spl mu/M.

Electrical Properties of Interfaces and Turn‐on Characteristics of TFEL Devices

A relationship between interface property of BaTa2O6(BTO) insulting later and operating characteristics of EL devices was experimentally examined. In order to obtain information on BTO. temperature-dependent-current characteristics of ITO-BTO-A1 has been investigated as a function of applied field for the both polarities. The turn-on voltage for TFRL devoces was lowered by the introduction of oxygen plasma exposure for the BTO film as well as top surface of ZnS. Luminance-transferred charge curves of TFELD revealed as more symmetric for the oxygen plasma treated device for both polarities. The experimental results suggest that via variation of surface of BTO via post-treatment of top-surface of lower insulator and top-surface of ZnS.

Novel detection platform for Alzheimer's amyloid-beta using magnetic beads in electrochemical impedance spectroscopy

In this paper, we proposed novel detection platform to detect Alzheimers amyloid-beta (Aβ) using pre-treated magnetic beads in Electrochemical Impedance Spectroscopy (EIS), for the first time. Without any immobilization on the electrodes of the EIS device, it shows ability to detect a few pg/ml of amyloid-beta oligomers and compared to the result of a conventional ELISA, which allows to simplify the measurement procedure, recycle the device by only changing magnet beads.

Highly sensitive detection of amyloid beta for Alzheimer’s disease diagnosis using bead-based impedance spectrometry

Background:Alzheimer’s disease (AD) is the most common neurodegenerative disease of dementia, and the development of early diagnosis platform is highly required for effective therapeutics. Recently, amyloid beta (Ab) has been considered as a major biomarker in AD diagnosis. Therefore, many researches have been studied in development of sensors to detect Ab of low concentration by using electrical methods such as field effect transistor and electrochemical impedance spectroscopy (EIS) to overcome the relatively high limit of detection in ELISA. All these devices required immobilization with antibody on the surface of sensing region in device itself. They showed LOD of a few pg/ml. So, we propose a new highly sensitive detection platform to quantify the concentration of Ab with immobilization of detection antibody not on the electrodes of EIS device but on the surface of magnetic beads. Methods:We designed a new detection platform including array of EIS device, fluidic channel and permanent magnet bar on/beneath a slide glass. EIS array device has individual hole on each working-counter electrode pair. The individual hole size is around 6 mm, and the bead size is around 2.8 mm. Therefore, each hole can capture 2 or 3 pre-treated beads that prepared by incubation with antibody. First pre-treated beads were injected into microfluidic channel, and these beads were located in each hole by the magnetic bar under a platform. Then, Ab monomer with different concentration was flown into device for 5 min, then non-specific Ab was removed by washing buffer. Finally, impedance measurement was measured with sweeping frequency. Results: We were able to detect Ab monomer below than 1 pg/ml with very small amount of sample (w4 ml), and total detection time was dramatically reduced to less than 10 minutes. The results were clearly distinguishable among the Ab samples with different concentration in impedance plot. Conclusions:Proposed novel detection method based on magnetic beads could be a feasible tool with high sensitivity for early diagnosis of AD. For further application of our platform, it needs more tests with Ab oligomer and blood samples of AD patients to confirm the usefulness in a diagnosis. P1-039 INHIBITORS OFAMYLOID BETA PEPTIDE

Development of Inductive and Capacitive Type Intraocular Pressure (IOP) Sensor to Improve Sensitivity and Minimize Size

Abstract We had presented an inductive type intraocular pressure sensor (L-sensor) in previous work. The distance between a micro coil anda ferrite on the membrane was modulated by pressure, and as a result the inductance and resonant frequency were changed. However,L-sensor has some problems to implant in eyes. First problem is low sensitivity. When L-sensor was implanted in rabbit’s eyes, resonantfrequency of L-sensor was very hard to detect. Second problem is biocompatibility. Size of L-sensor is 6×7×1.2 mm. When L-sensorwas implanted in the eyes, it caused the inflammation. Therefore, this study suggests an inductive and capacitive type IOP sensor (LC-sensor). The sensitivity of the LC-sensor 27.3 kHz/mmHg under 60 mmHg. It is much larger than 14 kHz/mmHg of the L-sensor. Andthe size of LC-sensor is 47% smaller than L-sensor. After 2 weeks from the implantation of LC-sensor into rabbit eyes, we measuredthe changes of resonant frequency of LC-sensor according to increased IOP by Balanced Salt Solution (BSS) injection. As a result, thesensitivity of LC-sensor in in vivo test is 25 kHz/mmHg. That is similar to the sensitivity of in vitro test.Keywords: Glaucoma, Intraocular pressure (IOP), IOP sensor, in vivo, Wireless, Implantable

Miniaturized Fluorescence Detection Chip for Queching Assay of Atrazine

This paper reports a miniaturized fluorescence detection chip with photodiode for quenching assay of atrazine, which effectively reduces the size of fluorescence detection system. The PIN photodiode with fluorescence filter was bonded with PDMS (polydimethylsiloxane) microfluidic chip and was placed just below the microfluidic channel. This detection chip has simple structure consisting of a microfluidic channel and a photodiode. The miniaturized fluorescence detection developed could detect 20 nM and it successfully detected the quenching of agricultural herbicide atrazine. The assay result was comparable to that of photomultiplier tube with a fluorescence microscope. This implies the miniaturized fluorescence detection system is applicable to the hand-held diagnostic device or portable environment monitoring system.