Biomedical subjects

Jeong-Gun Lee

Publications and source records attributed to Jeong-Gun Lee.

6 recordsLinked to original sources

PubMed2006

DNA biosensor based on the electrochemiluminescence of Ru(bpy)3(2+) with DNA-binding intercalators.

This paper reports a novel detection method for DNA hybridization based on the electrochemiluminescence (ECL) of Ru(bpy)(3)(2+) with a DNA-binding intercalator as a reductant of Ru(bpy)(3)(3+). Some ECL-inducible intercalators have been screened in this study using electrochemical methods combined with a chemiluminescent technique. The double-stranded DNA intercalated by doxorubicin, daunorubicin, or 4',6-diamidino-2-phenylindole (DAPI) shows a good ECL with Ru(bpy)(3)(2+) at +1.19 V (versus Ag/AgCl), while the non-intercalated single-stranded DNA does not. In order to stabilize the self-assembled DNA molecules during ECL reaction, we constructed the ECL DNA biosensor separating the ECL working electrode with an immobilized DNA probe. A gold electrode array on a plastic plate was assembled with a thru-hole array where oligonucleotide probes were immobilized in the side wall of thru-hole array. The fabricated ECL DNA biosensor was used to detect several pathogens using ECL technique. A good specificity of single point mutations for hepatitis disease was obtained by using the DAPI-intercalated Ru(bpy)(3)(2+) ECL.

Biosensing Techniques↗

PubMed2006

Control of particle-deposition pattern in a sessile droplet by using radial electroosmotic flow.

In this technical note, we report an experimental investigation of radial electroosmotic flow (EOF) as an effective means for controlling particle-deposition pattern inside an evaporating droplet, which has a potential application to biochemistry and analytical chemistry especially for sample preparation steps. Using the microelectrode, which consists of the circular electrode around the rim of droplet and the point electrode at the center of the droplet, we generate the radial electric field at the bottom of the electrolyte droplet. The electric field developed between the center electrode and the circular electrode causes a radial EOF in the vicinity of the bottom of the droplet. By changing the applied voltage, the strengths and directions of the radial EOF are controlled at one's own discretion, and thus, we can modify the solute distribution inside the droplet during evaporation. When the radial EOF compensates the natural outward flow at a suitable choice of electrical voltage, the particles are uniformly distributed at the entire droplet spot. Moreover, with strong radial EOF, all the particles are deposited at the center rather than at the rim. We also carry out a simple theoretical investigation of flow field inside the droplet with Smoluchowski slip velocity condition to show how the particles travel during evaporation.

Electroosmosis↗

PubMed2006

Drop formation via breakup of a liquid bridge in an AC electric field.

Experimental results are presented for the study of drop formation mechanism in a newly proposed electrohydrodynamic (EHD) method of drop generation in an AC electric field. In the method, a small drop is generated in two stages. A pendant drop is elongated with large oscillation by an electric force in the first stage. Then, it undergoes formation and breakup of a liquid bridge between the upper nozzle and the insulator-coated lower flat plate in the second stage. It is found that there exists a resonant frequency for maximum oscillation, which leads to an efficient drop formation in the latter stage. It is also found that breakup of liquid bridge is accelerated by the electrowetting tension acting on the drop perimeter contacting the insulator-coated flat plate. Thus the whole procedure of drop formation depends heavily on the frequency of AC field and the properties of the insulator such as hydrophilicity, thickness, and the dielectric constant. It is demonstrated that a wide range of drop size, from picoliter to nanoliter, can be obtained by controlling such key parameters without changing the nozzle diameter.

DNA↗

PubMed2006

Microchip-based one step DNA extraction and real-time PCR in one chamber for rapid pathogen identification.

Optimal detection of a pathogen present in biological samples depends on the ability to extract DNA molecules rapidly and efficiently. In this paper, we report a novel method for efficient DNA extraction and subsequent real-time detection in a single microchip by combining laser irradiation and magnetic beads. By using a 808 nm laser and carboxyl-terminated magnetic beads, we demonstrate that a single pulse of 40 seconds lysed pathogens including E. coli and Gram-positive bacterial cells as well as the hepatitis B virus mixed with human serum. We further demonstrate that the real-time pathogen detection was performed with pre-mixed PCR reagents in a real-time PCR machine using the same microchip, after laser irradiation in a hand-held device equipped with a small laser diode. These results suggest that the new sample preparation method is well suited to be integrated into lab-on-a-chip application of the pathogen detection system.

DNA, Bacterial↗

PubMed2006

DNA chip replication for a personalized DNA chip.

We report the replication technology of DNA chip using by sequence specific localization of nucleic acids via hybridization and electric transfer of the nucleic acids onto a new substrate without losing their array information. The denatured DNA fragments are first spotted and UV-cross-linked on a nylon membrane. The membrane is then immersed and hybridized in a DNA mixture solution that contains all complementary sequences of the nucleic acids to be hybridized with the DNA fragments on the membrane. The hybridized DNA fragments are transferred to another membrane at the denatured condition. After separating two membranes, the transferred membrane contains a complementary array of DNA fragments. This method can be used for the replication of the same copy of DNA chip repeatedly and moreover could be applied for a personalized DNA chip fabrication, where specific information of each spot of DNA chip is originated from the genetic information of a personal sample.

Carbocyanines↗

PubMed2005

Electrohydrodynamic (EHD) dispensing of nanoliter DNA droplets for microarrays.

In the present paper, we first demonstrated the possibility of electrohydrodynamic (EHD) dispensing method for preparing nanoliter probe DNA droplets on surfaces in DNA microarrays. To study the effect of an electric field on the dynamic behavior of pendent DNA droplet, visualization experiments with three kinds of electrode shapes are performed. In the early stage of droplet dispensing, it is shown that applied electric field assists a gravitational force exerted on DNA droplet. The pendent droplet is elongated in the parallel direction of applied electric field. However, after making fluid bridge between electrodes, it is shown that the electric force accelerates the capillary breaking of droplet by assisting a surface tension force exerted on droplet surface. Specifically, nanoliter dispensing volume (2 nL) is obtained in the needle-type electrode configuration. In addition, for the case of hydrophobic electrode surface, it is shown that the dispensing volume and spot size are remarkably decreased. Under the high relative humidity condition, it is observed that spot size is rapidly increased because of reduction in evaporation rate on droplet surface during the dispensing procedure. On the other hand, it is obtained that the spot size is not changed significantly in the wide range of DNA concentration from 1 to 10,000 nM. To monitor the influence of high electric voltage on DNA stability, we prepared a silicon-based chip with five capture probes for pathogens related with respiratory infectious diseases by EHD dispensing method. From the examination, it is clearly confirmed that pathogens are detected and the effective signal levels of pathogenic bacteria after hybridization are retained. Consequently, it is found that EHD dispensing method can be used to make cost-effective DNA microarrays with no thermal and electrical influences on DNA properties.

DNA↗