• BioChip Journal
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• v.12 no.4
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• pp.309-316
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• 2018

Microneedles (MNs) are being developed to overcome the limitations of the conventional hypodermic needle, e.g. the injection pain. In this study, we conducted an analysis of clinical pain and bleeding at the site of MN insertion and evaluated the insulin pharmacodynamic profile compared with parameters obtained with a conventional pen needle. MN insertion into the skin of 25 healthy adults or 15 patients with type 2 diabetes (T2D) revealed significantly less pain relative to a conventional hypodermic pen needle, thus reducing pain scores from $2.1{\pm}1.9$ to $21.3{\pm}1.4$ ($mean{\pm}standard$ deviation [SD]). Besides, no bleeding was observed when the MN was used. In the insulin pharmacodynamic assay, no significant differences were observed in the blood glucose-lowering effect between the pen needle and MN. Based on these results, the MN is expected to be a good substitute for conventional hypodermic pen needles and improve the quality of life of patients by significantly reducing the pain associated with insulin treatment.

• BioChip Journal
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• v.12 no.4
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• pp.340-347
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• 2018

$F{\ddot{o}}rster$ resonance energy transfer (FRET) is extremely sensitive to the separation distance between the donor and the acceptor which is ideal for probing such biological phenomena. Also, FRET-based probes have been developing for detecting an unamplified, low-abundance of target DNA. Here we describe the development of FRET based DNA sensor based on an accumulated QD system for detecting KRAS G12D mutation which is the most common mutation in cancer. The accumulated QD system consists of the polystyrene beads which surface is modified with carboxyl modified QDs. The QDs are sandwich-hybridized with DNA of a capture probe, a reporter probe with Texas-red, and a target DNA by EDC-NHS coupling. Because the carboxyl modified QDs are located closely to each other in the accumulated QDs, these neighboring QDs are enough to transfer the energy to the acceptor dyes. Therefore the FRET factor in the bead system is enhancing by the additional increase of 29.2% as compared to that in a single QD system. These results suggest that the accumulated nanobead probe with conjugated QDs can be used as ultrasensitive DNA nanosensors detecting the mutation in the various cancers.

• BioChip Journal
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• v.12 no.4
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• pp.294-303
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• 2018

Shear stress occurs in flowing liquids, especially at the interface of a flowing liquid and a stationary solid phase. Thus, it occurs inside the artery system of the human body, where it is responsible for a number of biological functions. The shear stress level generally remains less than $70dyne/cm^2$ in the whole circulatory system, but in the stenotic arteries, which are constricted by 95%, a shear stress greater than $1,000dyne/cm^2$ can be reached. Methods of researching the effects of shear stress on cells are of large interest to understand these processes. Here, we show the development of a microfluidic device for generating shear stress gradients. The performance of the shear stress gradient generator was theoretically simulated prior to experiments. Through simple manipulations of the liquid flow, the shape and magnitude of the shear stress gradients can be manipulated. Our microfluidic device consisted of five portions divided by arrays of micropillars. The generated shear stress gradient has five distinct levels at 8.38, 6.55, 4.42, 2.97, and $2.24dyne/cm^2$. Thereafter, an application of the microfluidic device was demonstrated testing the effect of shear stress on human umbilical vein endothelial cells.

• BioChip Journal
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• v.12 no.4
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• pp.326-331
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• 2018

Contamination by pesticides is an everincreasing problem associated with fields of environmental management and healthcare. Accordingly, appropriate treatments are in demand. Pesticide detection methods have been researched extensively, aimed at making the detection convenient, fast, cost-effective, and easy to use. Among the various detecting strategies, paper-based assay is potent for real-time pesticide sensing due to its unique advantages including disposability, light weight, and low cost. In this study, a paper-based sensor for chlorpyrifos, an organophosphate pesticide, has been developed by layering three sheets of patterned plates. In colorimetric quantification of pesticides, the blue color produced by the interaction between acetylcholinesterase and indoxyl acetate is inhibited by the pesticide molecules present in the sample solutions. With the optimized paper-based sensor, the pesticide is sensitively detected (limit of detection =8.60 ppm) within 5min. Furthermore, the shelf life of the device is enhanced to 14 days after from the fabrication, by treating trehalose solution onto the deposited reagents. We expect the paper-based device to be utilized as a first-screening analytic device for water quality monitoring and food analysis.

• Journal of the Korean Chemical Society
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• v.57 no.1
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• pp.81-87
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• 2013

Staphylococcus aureus is the most important pathogen in nosocomial infections, including bloodstream infections. Prompt identification of S. aureus from blood cultures and detection of methicillin resistance are essential in cases of suspected sepsis. We have studied a new method for the sequence-specific visual detection of minute amounts of nucleic acids using intercalating reaction by addition of SYBR Green to amplicons of LAMP, and it's a unique gene amplification method in which DNA can be isothermally amplified using only one enzyme. Staphylococcus-LAMP, which targets the spa gene, encoding S.aureus-specific protein A, and the mecA gene, encoding penicillin-binding protein-2' for methicillin resistance, detected MRSA and MRSE. In this study, by using LAMP assay, I detected for Staphylococcus aureus and Staphylococcus epidermidis concentration in the clinical sample. The detection of Staphylococcus aureus and Staphylococcus epidermidis was tested by using serial 10-fold dilutions standard solution. I have accurate detected the limit of detection, sensitity, specificity and reproducibility of the assay. The Bio-chip based LAMP assay allowed easy, rapid, accurate and sensitive detection of infection with Staphylococcus and especially applicable in a resource-limited situation.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.7
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• pp.45-51
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• 2000

지난 세기부터 MEMS 제작 기술을 이용하여 만들어진 시스템들을 의학이나 생물학적인 용도로 응용하기 위한 많은 연구가 활발히 이루어져 왔다. 기술적인 측면에서 이러한 연구들은 MEMS 분야의 초창기에 강조되어 온 표면 및 몸체 미세 가공 기술(surface ＆ bulk micromachining)과 같은 미세 구조물 제작 기술의 발전에 힘입은 바 크다. 그러나 MEMS 기술이 점차 발전되어 오면서, 가공 기술이 고도화되고 미세 시스템의 구조가 점차 복잡해짐에 따라, 많은 연구들이 단순한 가공기술을 넘어 미세 시스템을 조립하고 집적화할 수 있는 기술, 접합 (bonding) 기술, 패키징 (packaging) 기술, 3차원 형상의 제작 기술, 실리콘(silicon)이나 유리(glass)가 아닌 다른 재료를 이용한 미세 가공 기술 등의 개발을 중심으로 이루어지고 있다.(중략)

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.237-240
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• 2005

The demand of micro electrical mechanical system (MEMS) bio/chemical sensor is rapidly increasing. To prevent the contamination of sensing area, a filtration system is required in on-chip total analyzing MEMS bio/chemical sensor. A nano-filter was mainly applied in some application detecting submicron feature size bio/chemical products such as bacteria, fungi and so on. We suggested a simple nano-filter fabrication process based on replication process. The mother pattern was fabricated by holographic lithography and reactive ion etching process, and the replication process was carried out using polymer mold and UV-imprinting process. Finally the nano-filter is obtained after removing the replicated part of metal deposited replica. In this study, as a practical example of the suggested process, a nano-dot array was replicated to fabricate nano-filter fur bacteria sensor application.

• Applied Science and Convergence Technology
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• v.25 no.3
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• pp.61-65
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• 2016

Here, the rapid detection of Salmonella typhimurium by a portable surface plasmon resonance (SPR) biosensor in which the beam from a diode laser is modulated by a rotating mirror is reported. Using this system, immunoassay based on lipopolysaccharides (LPS)-specific monoclonal anti-Salmonella antibody was performed. For the purpose of orientation-controlled immobilization of antibodies on the SPR chip surface, the cysteine-mediated immobilization method, which is based on interaction between a gold surface and a thiol group (-SH) of cysteine, was adopted. As a result, using the portable SPR-based immunoassay, we detected S. typhimurium in the range from 10^7 CFU/mL to 10^9 CFU/mL within 1 hour. The results indicate that the portable SPR system could be potentially applied for general laboratory detection as well as on-site monitoring of foodborne, clinical, and environmental agents of interest.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.87-92
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• 2007

A $CaAl_{12}O_{19}:Mn^{4+}$ red phosphor showed the highest emission intensity at a concentration of 0.02mole $Mn^{4+}$ and the high crystallinity and luminescent properties were obtained at $1600^{\circ}C$ firing temperature for 3hr. The synthesized phosphor showed a broad emission band at 658nm wavelength. Red light-emitting diodes(LEDs) were fabricated through the integration of on InGaN UV bare chip and a 1:3 ratio of $CaAl_{12}O_{19}:Mn^{4+}$ and epoxy resin in a single package. This coated LED can be applicable to make White LEDs under excitation energy of UV LED.

• BioChip Journal
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• v.12 no.4
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• pp.332-339
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• 2018

The future neuro-prosthetic devices would be required spikes data monitoring through sub-nanoscale transistors that enables to neuroscientists and clinicals for scalable, wireless and implantable applications. This research investigates the spikes monitoring through integrated CNT front-end amplifier for neuro-prosthetic diagnosis. The proposed carbon nanotube-based architecture consists of front-end amplifier (FEA), integrate fire neuron and pseudo resistor technique that observed high electrical performance through neural activity. A pseudo resistor technique ensures large input impedance for integrated FEA by compensating the input leakage current. While carbon nanotube based FEA provides low-voltage operation with directly impacts on the power consumption and also give detector size that demonstrates fidelity of the neural signals. The observed neural activity shows amplitude of spiking in terms of action potential up to $80{\mu}V$ while local field potentials up to 40 mV by using proposed architecture. This fully integrated architecture is implemented in Analog cadence virtuoso using design kit of CNT process. The fabricated chip consumes less power consumption of $2{\mu}W$ under the supply voltage of 0.7 V. The experimental and simulated results of the integrated FEA achieves $60G{\Omega}$ of input impedance and input referred noise of $8.5nv/{\sqrt{Hz}}$ over the wide bandwidth. Moreover, measured gain of the amplifier achieves 75 dB midband from range of 1 KHz to 35 KHz. The proposed research provides refreshing neural recording data through nanotube integrated circuit and which could be beneficial for the next generation neuroscientists.