Biomedical subjects

Ho Sup Jung

Publications and source records attributed to Ho Sup Jung.

5 recordsLinked to original sources

PubMed2006

Electrochemical detection of 17beta-estradiol using DNA aptamer immobilized gold electrode chip.

An electrochemical detection method for chemical sensing has been developed using a DNA aptamer immobilized gold electrode chip. DNA aptamers specifically binding to 17beta-estradiol were selected by the SELEX (Systematic Evolution of Ligands by EXponential enrichment) process from a random ssDNA library, composed of approximately 7.2 x 10(14) DNA molecules. Gold electrode chips were employed to evaluate the electrochemical signals generated from interactions between the aptamers and the target molecules. The DNA aptamer immobilization on the gold electrode was based on the avidin-biotin interaction. The cyclic voltametry (CV) and square wave voltametry (SWV) values were measured to evaluate the chemical binding to aptamer. When 17beta-estradiol interacted with the DNA aptamer, the current decreased due to the interference of bound 17beta-estradiol with the electron flow produced by a redox reaction between ferrocyanide and ferricyanide. In the negative control experiments, the current decreased only mildly due to the presence of other chemicals.

Aptamers, Nucleotide↗

PubMed2005

Soft lithographic patterning of supported lipid bilayers onto a surface and inside microfluidic channels.

We present simple soft lithographic methods for patterning supported lipid bilayer (SLB) membranes onto a surface and inside microfluidic channels. Micropatterns of polyethylene glycol (PEG)-based polymers were fabricated on glass substrates by microcontact printing or capillary moulding. The patterned PEG surfaces have shown 97 +/- 0.5% reduction in lipid adsorption onto two dimensional surfaces and 95 +/- 1.2% reduction inside microfluidic channels in comparison to glass control. Atomic force microscopy measurements indicated that the deposition of lipid vesicles led to the formation of SLB membranes by vesicle fusion due to hydrophilic interactions with the exposed substrate. Furthermore, the functionality of the patterned SLBs was tested by measuring the binding interactions between biotin (ligand)-labeled lipid bilayer and streptavidin (receptor). SLB arrays were fabricated with spatial resolution down to approximately 500 nm on flat substrate and approximately 1 microm inside microfluidic channels, respectively.

Dimethylpolysiloxanes↗

PubMed2005

Amperometric immunosensor for direct detection based upon functional lipid vesicles immobilized on nanowell array electrode.

An original electrochemical immunosensor has now been developed that is based upon the spontaneous immobilization of biotinylated, functional lipid vesicles (FLVs) on a polymeric resist layer. An electrode was fabricated utilizing a form of electron-beam (e-beam) that has been used to fabricate 200 nm (nanoscale) wells in the resist layer covering of the gold electrode. The stability of adhered FLVs upon the nanowell (NW) electrode was observed by atomic force microscopy (AFM). From these observations, we were able to determine that the assembled FLVs primarily adhered as individual molecules, that is, without the aggregation or fusion noted in earlier designs. Additionally, these immobilized FLVs demonstrated clearly defined redox activity in electrochemical measurements. Streptavidin, biotinylated capture antibody, and target proteins were consequently injected in order to set up the immunoassay environment. Electrochemical immunoassay experimentation was performed on the NW array electrode with model proteins, such as human serum albumin (HSA) and carbonic anhydrase from bovine (CAB). We observed a notable current decrease, following the redox path, interrupted by the target HSA, indicating the binding of the capture antibody with the target antigen. On the basis of these results, we propose a new type of immunosensor incorporating this mechanism of spontaneous immobilization of FLVs.

Electrochemistry↗

PubMed2005

Spontaneous immobilization of liposomes on electron-beam exposed resist surfaces.

We have found an interesting immobilization technique of liposomes on electron-beam exposed resist surfaces. The immobilized liposomes have been visualized by the atomic force microscope and have shown well-organized three-dimensional physical structures, in which the liposomes maintain their shapes and sizes similar to those of the original design in prepared solution. The immobilization is based on a strong static charge interaction between the resist surface and the liposomes. Further experiments show that very strong charge in the surfaces produces the firm immobilization of the liposome. We believe these findings can be related to various liposome applications such as drug delivery system, electrochemical or biosensors, and nanoscale membrane function studies.

Liposomes↗

PubMed2005

Heat-enhanced production of chitosanase from Streptomyces griseus in the presence of liposome.

The effects of heat stress and liposome treatment on the growth of Streptomyces griseus cells and chitosanase production were investigated on the basis of using the designed strategy of a stress-mediated bioprocess. The effective conditions for increasing the interaction between chitosanase and the 1-palmitoyl-2-oleoyl-3-phosphocholine (POPC) liposome under heat stress condition were determined on the basis of the results of circular dichroism (CD) and dielectric dispersion analysis (DDA). Under these effective conditions, S. griseus cells were cultivated for the effective production of chitosanase. The results obtained from both CD spectra and DDA showed that heat stress enhances the interaction of the POPC liposomes and chitosanase. The strongest interaction between them could be obtained in the specific temperature range of 40-45 degrees C. The enhancement of the target chitosanase production was conducted under heat stress at 41 degrees C in the presence and absence of the POPC liposomes. The growth rates of S. griseus cells in the cases of heat (41 degrees C) and heat (41 degrees C)/POPC treatments were respectively 1.2 and 1.4 times higher than that obtained under the control condition. In the heat (41 degrees C) and heat (41 degrees C)/POPC treatments, chitosanase activity increased to 1.8 and 2 times, respectively, higher than that obtained under the control condition. Heat stress and the addition of the POPC liposomes could therefore be utilized to induce the potential functions of bacterial cells for the enhancement of the final target production.

Culture Media↗