Joon-Ho Maeng

Hanyang University, Ansan, Gyeonggi, South Korea

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Publications (8)13.53 Total impact

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    ABSTRACT: This paper reports the development of a disposable, integrated biochip for DNA sample preparation and polymerase chain reaction (PCR). The hybrid biochip (25mm X 45mm) is composed of a disposable polydimethylsiloxane (PDMS) layer with a microchannel chamber and a reusable glass substrate integrated with a microheater and thermal microsensor. Lysis, purification, and PCR can be performed sequentially on this microfluidic device. Cell lysis is achieved by heat and purification is performed by mechanical filtration. Passive check valves are integrated to enable sample preparation and PCR in a fixed sequence. Reactor temperature needed to lysis and PCR reaction is controlled within ±1°C by PID controller of LabVIEW software. Buccal epithelial cell lysis, DNA purification, and SY158 gene PCR amplification were successfully performed on this novel chip. Our experiments confirm that the entire process, except the off-chip gel electrophoresis, requires only approximately 1 hour for completion. This disposable microfluidic chip for sample preparation and PCR can be easily united with other technologies to realize a fully integrated DNA-chip. This article is protected by copyright. All rights reserved.
    Electrophoresis 06/2013; · 3.26 Impact Factor
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    ABSTRACT: We present a novel method for the separation of progressive motile sperm from non-progressive motile and immotile sperm. This separation was accomplished by inducing chemotaxis along a longitudinal chemical gradient in a microchip composed of a biocompatible polydimethysiloxane layer and a glass substrate. In a preliminary experiment using fluorescent rhodamine B as a marker, we verified that a chemical gradient was generated by diffusion within the microchannel. We used acetylcholine as a chemoattractant to evaluate the chemotactic response of sperm. We tested the response to a 1/2 to 1/64 dilution series of acetylcholine. The results of a mouse sperm chemotaxis assay showed that progressive motile sperm swam predominantly toward the outlet at an optimal chemical gradient of 0.625 (mg/ml)/mm of acetylcholine. This device provides a convenient, disposable, and high-throughput platform that could function as a progressive motile sperm sorter for potential use in intracytoplasmic sperm injection.
    Analytical Sciences 01/2012; 28(1):27-32. · 1.57 Impact Factor
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    ABSTRACT: A novel PDMS and glass-based microfluidic device consisting of a micromixer and microreactor for DNA ligation is described in this article. The new passive type planar micromixer is 10.33mm long and composed of a straight channel integrated with nozzles and pillars, and the microreactor is composed of a serpentine channel. Mixing was enhanced by convective diffusion facilitated by the nozzles and pillars. The performance of the micromixer was analytically simulated and experimentally evaluated. The micromixer showed a good mixing efficiency of 87.7% at a 500μL/min flow rate (Re=66.5). DNA ligation was successfully performed using the new microfluidic device, and ligation time was shortened from 4h to 5min. When used for on-chip ligation, this new micromixer offers advantages of disposability and portability.
    Sensors and Actuators B-chemical - SENSOR ACTUATOR B-CHEM. 01/2011; 157(2):735-741.
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    ABSTRACT: Microfluidic-based microchips have become the focus of research interest for immunoassays and biomarker diagnostics. This is due to their aptitude for high-throughput processing, small sample volume, and short analysis times. In this paper, we describe the development of a microchip-based multiplex electro-immunosensing system for simultaneous detection of cancer biomarkers using gold nanoparticles and silver enhancer. Our microchip is composed of biocompatible poly(PDMS) and glass substrates. To fix the antibody-immobilized microbeads, we used pillar-type microfilters within a reaction chamber. An immunogold silver staining (IGSS) method was used to amplify the electrical signal that corresponded to the immune complex. To demonstrate this approach, we simultaneously assayed three cancer biomarkers, alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), and prostate-specific antigen (PSA) on the microchip. The electrical signal generated from the result of the immunoreaction was measured and monitored by a PC-based system. The overall assay time was reduced from 3-8 h to about 55 min when compared to conventional immunoassays. The working range of the proposed microchip was from 10(-3) to 10(-1) microg/mL of the target antigen.
    Electrophoresis 08/2008; 29(16):3466-76. · 3.26 Impact Factor
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    ABSTRACT: Conventional immunoassays are labor intensive, expensive and time consuming and require large pieces of equipment for detection. Therefore, we have developed and characterized a novel immunoassay methodology comprised of microbeads and microbiochips. In this method, microbeads are used to filter and immobilize antibodies and an immuno-gold silver staining (IGSS) method is then used to amplify electrical signals that correspond to the bound antibodies. The chip used for this system is composed of an inexpensive and biocompatible polydimethylsiloxane (PDMS) layer over a Pyrex glass substrate that contains a platinum (Pt) microelectrode, which is used to detect the electrical signal in this system, the microelectrode is fabricated on the substrate and a microchannel and pillar-type microfilter is formed in the PDMS layer. A sandwich immunoassay approach was applied to detect alpha-fetoprotein (AFP), a cancer biomarker, using this system. The results of this study showed that the time required for a complete assay was reduced by 1h and a detection limit as low as 1 ng/mL was attained when this system used, which indicates that similar bead-based electrical detection systems could be used for the diagnosis of many forms of cancer.
    Biosensors and Bioelectronics 05/2008; 23(9):1319-25. · 5.44 Impact Factor
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    ABSTRACT: This paper presents a new microchip which can separate motile sperm by chemotaxis. The microchip was developed to create longitudinal concentration gradient in the microchannel due to diffusion. Linearly good concentration gradient of chemoattractant was generated without any fluid control devices. In sperm separation experiment with the developed microchip, mouse sperm was used as sample and acetylcholine was selected as chemoattractant. Human tubal fluid (HTF), buffer solution, was introduced into the microchannel of the microchip and attractants diluted in ratio of 1, 1/2, 1/4, 1/8, 1/16, 1/32 and 1/64 including control (DI water) were dropped in each outlet by volume with micropippet. After 5min, sperm solution was dropped into inlet of the chip. After 10 min, when sperms reached to the outlet by chemotaxis, we counted sperms in each outlet by using microscopy. Consequently, we could separate progressive motile sperm with the new microchip. In the experiment, the most sperms were isolated at the outlet dropped with 1/16 diluted solution. The optimal concentration gradient to induce chemotaxis was about 0.625 mg/ml/mm.
    Transactions of the Korean Society of Mechanical Engineers A 01/2008; 32(12):1115-1122.
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    ABSTRACT: This paper presents the development of a PDMS–glass hybrid electro-immunosensing chip for real-time measurement of an antigen–antibody reaction through an electrical signal. Using a microfilter and microbeads, the antigen was easily immobilized in the detection zone where the microelectrodes were located. The immuno-reaction was detected by measuring the electrical resistance between microelectrodes using gold nanoparticles with silver enhancement. An immunoassay test with the developed chip was performed for the antigen of protein A, the specific first antibody of anti-protein A, the nonspecific first antibody of HBsAg monoclonal IgG, and the second antibody anti-rabbit IgG. The electro-immunosensing chip reduced the antigen–antibody reaction time to 10 min, thus reducing the overall assay time to about 1 h. The electrical resistance varied according to the concentration of the specific first antibody, the detection limit of which was 10 ng/ml. Compared to conventional enzyme-linked immunosorbent assays (ELISAs), the process of performing an immunoassay using the electro-immunosensing chip was relatively simple and required less time to complete. In addition, the electro-immunosensing chip required less sample volume.
    Sensors and Actuators B: Chemical. 01/2008;
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    ABSTRACT: This study presents the characterization of an integrated portable microfluidic electrical detection system for fast and low volume immunoassay using polystyrene microbead, which are used as immobilization surfaces. In our chip, a filtration method using the microbead was adopted for sample immobilization and immunogold silver staining(IGSS) was used to increase the electrical signal. The chip is composed of an inexpensive and biocompatible Polydimethylsiloxane(PDMS) layer and Pyrex glass substrate. Platinum microelectrodes for electric signal detection were fabricated on the substrate and microchannel and pillar-type microfilters were formed in the PDMS layer. With a fabricated chip, we reacted antigen and antibody according to the procedures. Then, silver enhancer was injected to increase the size of nanogold particles tagged with the second antibody. As a result, microbeads were connected to each other and formed an electrical bridge between microelectrodes. Resistance measured through the electrodes showed a difference of two orders of magnitude between specific and nonspecific immuno-reactions. The detection limit was 10 ng/ml. The developed immunoassay chip reduced the total analysis time from 3 hours to 50 min. Fast and low-volume biochemical analysis has been successfully achieved with the developed microfilter and immuno-sensor chip, which is integrated to the microfluidic system.
    KSBB Journal. 01/2006; 21(5).