Seung-Mo Ha

On-chip immunoassay using surface-enhanced Raman scattering of hollow gold nanospheres.

A surface-enhanced Raman scattering (SERS)-based gradient optofluidic sensor has been developed for a fast and sensitive immunoassay. In this work, a novel microfluidic sensor with functional internal structures has been designed and fabricated. This sensor is composed of three compartments consisting of the gradient channel that serially dilutes the target marker, the injection and mixing area of antibody-conjugated hollow gold nanospheres and magnetic beads, and the trapping area of sandwich immunocomplexes using multiple solenoids. Quantitative analysis of a specific target marker is performed by analyzing its characteristic SERS signals. This SERS-based gradient optofluidic sensor can replace the set of microwells or microtubes used in manual serial dilutions that have been traditionally used in enzyme-linked immunosorbent assay (ELISA)-type assays. The limit of detection for rabbit immunoglobin (IgG) is estimated to be 1-10 ng/mL. This novel SERS-based optofluidic immunoassay system is expected to be a powerful clinical tool for the fast and sensitive medical diagnosis of a disease.

Separation-Type Multiplex Polymerase Chain Reaction Chip for Detecting Male Infertility

A novel polymerase chain reaction (PCR) biochip is presented in this paper. In this PCR chip, the glass substrate integrated with the microheater and microsensor is separable from the reaction chamber where the sample is injected, which now makes repeated reuse of the glass substrate possible. The heat transfer efficiency and target gene amplification of the proposed separable PCR chip was compared with that of the conventional united PCR chip. The results showed that the sex-determining Y chromosome (SRY) gene PCR for detecting male infertility was successfully performed in the separable chip. However, repeated multiplex PCR was successful for only two genes, SPGY1 and SRY, but not for gene SY586. Future work is needed for a multiplex PCR with more than three genes.

Development of microbiochip for detection of metalloproteinase 7 using fluorescence resonance energy transfer

A protease is any enzyme that catalyzes the hydrolysis of proteins into smaller peptide fragments and amino acids, a process known as proteolysis. They are involved in a multitude of normal biological processes as well as in diseases, including cancer, stroke and infections. Here we present a microfluidicbased assay system to detect proteolytic activity using fluorescence resonance energy transfer (FRET) by quantum dot (QD)-peptide conjugates immobilized on microbeads. As an energy donor, QD was immobilized on the microbead surface by the avidin-biotin interaction. As an energy acceptor, the fluorophorelabeled peptide was then associated with QD, thus quenching the photoluminescence (PL) of the QD. The functionalized microbeads were introduced into the microbiochip and captured by a micropillar in the reaction chamber. In the presence of matrix metalloprotease-7 (MMP-7) as a model protease, the PL of QD quenched by fluorophore was recovered due to the proteolytic activity of MMP-7 in the fabricated microbiochip. Moreover, the FRET efficiency induced by MMP-7 was linearly dependent on the logarithmic concentration of MMP-7. This technology is not limited to sensing MMP-7, but could be used to monitor other protease activities (Schematic diagram).

Separation type multiplex PCR chip for detecting male infertility

PDMS-glass based multiplex PCR chip was developed for the diagnosis of the male infertility. The PCR chip was improved to the disposable by enabling the sensor and heater to be separable from the reactor of the chip. Multiplex PCR was successfully performed for two genes of SPGY1 and SY158, but was not succeeded repeatedly for three genes of SPGY1, SY586, and SY158.

Study on Microbiochip for Buccal Cell Lysis and DNA Purification

This paper describes a separable microfluidic device fabricated with PDMS (polydimethylsiloxane) and glass. The device is used for sample preparation involving cell lysis and the DNA purification process. The cell lysis was performed for 2 min at 80°C in a serpentine-type microreactor (20 l) using a Au microheater that was integrated with μ a thermal microsensor on a glass substrate. The DNA that was mixed with other residual products during the cell lysis process was then filtered through a new filtration system composed of microbeads (diameter: 50 m) and PDMS pillars. μ Since the entire process (sample loading, cell lysis reaction, DNA purification, and sample extraction) was performed within 5 min in a microchip, we could reduce the sample preparation time in comparison with that for the conventional methods used in biochemistry laboratories. Finally, we verified the performance of the sample preparation chip by conducting PCR (polymerase chain reaction) analysis of the chip product.

Surface Modification of Micromolds by Fluorocarbon Films

CVD fluorocarbon (FC) thin films were deposited on mold surfaces such as silicon and SU-8 to reduce the adhesion of surfaces with PDMS during molding processes. FC films coated silicon and SU-8 mold surface showed no degradation of PDMS surfaces and good nanotribological characteristics.