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A testing method is disclosed. The testing method includes: providing a mixture solution of a gelling agent and a microbe to a gelling device; solidifying the mixture solution to form a solid thin film in which the microbe is immobilized; supplying a bioactive agent to the solid thin film and allowing the bioactive agent to diffuse into the solid thin film; and imaging the individual responses of the single microbial cells to the bioactive agent, and determining the minimum inhibitory concentration (MIC) of the bioactive agent based on the analysis of the images to obtain AST results.

Kim J.,Seoul National University | Kim E.-G.,Seoul National University | Kim E.-G.,QuantaMatrix Inc. | Bae S.,Seoul National University | And 3 more authors.
Analytical Chemistry | Year: 2013

The parallelization of microfluidic cytometry is expected to lead to considerably enhanced throughput enabling point-of-care diagnosis. In this article, the development of a microfluidic potentiometric multichannel cytometer is presented. Parallelized microfluidic channels sharing a fluid path inevitably suffer from interchannel signal crosstalk that results from electrical coupling within the microfluidic channel network. By employing three planar electrodes within a single detection channel, we electrically decoupled each channel unit, thereby enabling parallel analysis by using a single cytometer microchip with multiple microfluidic channels. The triple-electrode configuration is validated by analyzing the size and concentration of polystyrene microbeads (diameters: 1.99, 2.58, 3, and 3.68 μm; concentration range: ∼2 × 105 mL-1 to ∼1 × 10 7 mL-1) and bacterial microdispersion samples (Bacillus subtilis, concentration range: ∼4 × 105 CFU mL-1 to ∼3 × 106 CFU mL-1). Crosstalk-free parallelized analysis is then demonstrated using a 16-channel potentiometric cytometer (maximum cross-correlation coefficients |r|: < 0.13 in all channel combinations). A detection throughput of ∼48 000 s-1 was achieved; the throughout can be easily increased with the degree of parallelism of a single microchip without additional technical complexities. Therefore, this methodology should enable high-throughput and low-cost cytometry. © 2012 American Chemical Society.

Choi J.,Seoul National University | Yoo J.,QuantaMatrix Inc. | Lee M.,QuantaMatrix Inc. | Kim E.-G.,QuantaMatrix Inc. | And 10 more authors.
2015 Transducers - 2015 18th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS 2015 | Year: 2015

A rapid antibiotic susceptibility test (AST) is desperately needed in clinical settings for fast and appropriate antibiotic administration. Traditional ASTs, which rely on cell culture, are not suitable for urgent cases of bacterial infection and antibiotic resistance owing to their relatively long test times. Here, we describe a novel AST called single-cell morphological analysis (SCMA) that can determine antimicrobial susceptibility by automatically analyzing and categorizing morphological changes in single bacterial cells under various antimicrobial conditions. The SCMA was tested with four Clinical and Laboratory Standards Institute standard bacterial strains and 189 clinical samples from hospitals. The results were compared with the gold standard broth microdilution test. The SCMA results were obtained in less than 4 hours with 91.5% categorical agreement and 6.51% minor, 2.56% major, and 1.49% very major discrepancies. Thus, SCMA provides rapid and accurate antimicrobial susceptibility data. © 2015 IEEE.

Jang J.,Seoul National University | Jang J.,Seoul Semiconductor | Han S.,Seoul National University | Han S.,Seoul Semiconductor | And 7 more authors.
Microelectronic Engineering | Year: 2014

We introduce a conformal phosphor coating technique for white light-emitting diodes (LEDs) using image-processing-based maskless lithography (IP-ML). The use of IP-ML allows real-time recognition of LEDs, which enables the generation of photo-patterning masks on a spatial light modulator by means of image processing, making the process suitable for a chip-level conformal phosphor coating with contact openings. This automated photolithographic chip array coating process enables phosphor coating onto chips with a consistent thickness, and the chips treated using this method show a narrow color distribution in which the chromaticity is controllable by varying phosphor thickness and concentration. © 2014 Elsevier B.V. All rights reserved.

Choi J.,Seoul National University | Choi J.,Korea University | Jung Y.-G.,QuantaMatrix Inc. | Na H.,Seoul National University | And 8 more authors.
Proceedings of the 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2012 | Year: 2012

These days the most widely used methods for Antibiotics Susceptibility Test (AST) are the micro-dilution method for liquid condition and the disk diffusion method for solid condition. Using the micro-dilution method, automated AST systems have been developed. The system consume relatively large amount of bacteria and test time because it measures optical density (OD) for bacterial growth to determine the minimal inhibitory concentrations (MICs) of relevant antibiotics. We have invented a new microfluidic channel system for AST to reduce both amount of bacteria and test time dramatically. The agarose based microfulidic channel system fixes bacterial cell and tracks single cell growth to reduce AST assay time and to determine MICs of antibiotics. In this system, the conventional laboratory bacteria and four standard bacteria of Clinical and Laboratory Standard Institute (CLSI) were tested with several kinds of antibiotics to determine the MIC values. The obtained MIC values were confirmed using the conventional method (micro-dilution method) and also compared with the MIC data from CLSI. As a result, this system showed no different MIC values from conventional systems and innovatively reduced assay time and amounts of medium, antibiotics and bacterial cells for MIC determination.

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