Biomedical subjects

Sang Kyung Kim

Publications and source records attributed to Sang Kyung Kim.

4 recordsLinked to original sources

PubMed2004

Fabrication of comb interdigitated electrodes array (IDA) for a microbead-based electrochemical assay system.

This research is directed towards developing a more sensitive and rapid electrochemical sensor for enzyme labeled immunoassays by coupling redox cycling at interdigitated electrode arrays (IDA) with the enzyme label beta-galactosidase. Coplanar and comb IDA electrodes with a 2.4 microm gap were fabricated and their redox cycling currents were measured. ANSYS was used to model steady state currents for electrodes with different geometries. Comb IDA electrodes enhanced the signal about three times more than the coplanar IDAs, which agreed with the results of the simulation. Magnetic microbead-based enzyme assay, as a typical example of biochemical detection, was done using the comb and coplanar IDAs. The enzymes could be placed close to the sensing electrodes (approximately 10 microm for the comb IDAs) and detection took less than 1 min with a limit of detection of 70 amol of beta-galactosidase. We conclude that faster and more sensitive assays can be achieved with the comb IDA.

Biosensing Techniques↗

PubMed2004

Microbead-based electrochemical immunoassay with interdigitated array electrodes.

The objective of this study was to develop a sensitive and miniaturized immunoassay by coupling a microbead-based immunoassay with an interdigitated array (IDA) electrode. An IDA electrode amplifies the signal by recycling an electrochemically redox-reversible molecule. The microfabricated platinum electrodes had 25 pairs of electrodes with 1.6-microm gaps and 2.4-microm widths. An enzyme-labeled sandwich immunoassay on paramagnetic microbeads with mouse IgG as the analyte and beta-galactosidase as the enzyme label was used as the model system. beta-Galactosidase converted p-aminophenyl beta-D-galactopyranoside to p-aminophenol (PAP). This enzyme reaction was measured continuously by positioning the microbeads near the electrode surface with a magnet. Electrochemical recycling occurred with PAP oxidation to p-quinone imine (PQI) at +290 mV followed by PQI reduction to PAP at -300 mV vs Ag/AgCl. Dual-electrode detection amplified the signal fourfold compared to single-electrode detection, and the recycling efficiency reached 87%. A calibration curve of PAP concentration vs anodic current was linear between 10(-4) and 10(-6)M. A signal from 1000 beads in a 20-microL drop was detectable and the immunoassay was complete within 10 min with a detection limit of 3.5x10(-15)mol mouse IgG.

Aminophenols↗

PubMed2004

Bead-based electrochemical immunoassay for bacteriophage MS2.

Viruses are one of four classes of biothreat agents, and bacteriophage MS2 has been used as a simulant for biothreat viruses, such as smallpox. A paramagnetic bead-based electrochemical immunoassay has been developed for detecting bacteriophage MS2. The immunoassay sandwich was made by attaching a biotinylated rabbit anti-MS2 IgG to a streptavidin-coated bead, capturing the virus, and then attaching a rabbit anti-MS2 IgG-beta-galactosidase conjugate to another site on the virus. beta-Galactosidase converts p-aminophenyl galactopyranoside (PAPG) to p-aminophenol (PAP). PAPG is electroinactive at the potential at which PAP is oxidized to p-quinone imine (PQI), so the current resulting from the oxidation of PAP to PQI is directly proportional to the concentration of antigen in the sample. The immunoassay was detected with rotating disk electrode (RDE) amperometry and an interdigitated array (IDA) electrode. With an applied potential of +290 mV vs Ag/AgCl and a rotation rate of 3000 rpm, the detection limit was 200 ng/mL MS2 or 3.2 x 10(10) viral particles/mL with RDE amperometry. A trench IDA electrode was incorporated into a poly(dimethyl siloxane) channel, within which beads were collected, incubated with PAPG, and PAP generation was detected. The two working electrodes were held at +290 and -300 mV vs Ag/AgCl, and electrochemical recycling of the PAP/PQI couple by the IDA electrode lowered the limit of detection to 90 ng/mL MS2, or 1.5 x 10(10) MS2 particles/mL.

Aminophenols↗

PubMed2003

Nitric oxide mediates epinephrine-induced apoptotic cell death of trabecular meshwork cells in vitro.

To evaluate the effect of epinephrine on the cellular proliferation and production of nitric oxide (NO) in trabecular meshwork (TM) cells, cultured porcine TM cells were exposed to epinephrine at various concentrations, with and without its NO inhibitor, N(omega)-Nitro-L-arginine methyl ester (L-NAME). The proliferation of TM cells and the production of NO were quantified by rapid colorimetric assays. Acridine orange/Hoechest 33342 staining and flow cytometry were done to evaluate apoptosis. Epinephrine inhibited the proliferation of cultured TM cells and produced NO at significant levels in a dose-dependent manner. However, the antiproliferative effect of epinephrine was abolished by L-NAME. Fluorescent microscopy and flow cytometric analysis revealed that epinephrine induced apoptotic cell death, which was suppressed by L-NAME. The current results suggest that the inhibitory effect of epinephrine on TM cell survival is associated with NO production. NO-mediated apoptosis may be involved in this epinephrine-induced antiproliferative effect on TM cells.

Animals↗