Juyeon Jung

Nuclease-resistant DNA aptamer on gold nanoparticles for the simultaneous detection of Pb2+ and Hg2+ in human serum.

There has been great progress in the development of functional DNA-based sensors for the detection of metal ions. However, many functional DNAs are vulnerable to hydrolysis by nucleases in human blood. In addition, the detection methods that are based on DNA often exhibit interference due to the high blood concentrations of other ions, such as K(+) and Na(+). Therefore, we selected highly Pb(2+)-specific DNA-aptamer sequences based on CD spectroscopy of 4 G-rich DNA sequences and Hg(2+)-specific T-rich DNA sequences and immobilized them on gold nanoparticles for the simultaneous detection of Pb(2+) and Hg(2+) in human serum. We used gold nanoparticles because these have a superior fluorescence-quenching efficiency over a broad range of wavelengths compared with other organic quenchers. In addition, gold nanoparticles have a stabilizing effect on the immobilized DNA, which makes it more resistant to degradation by nucleases than free DNA. As a result, even in the presence of DNase, we were able to simultaneously detect Pb(2+) and Hg(2+) in serum at concentrations as low as 128 pM and 121 pM, respectively, within 10 min. These detection limits for Pb(2+) and Hg(2+) were 39-fold and 26.4-fold lower, respectively, than the detection limits that were obtained using free DNAs. Given the multi-color-fluorescence quenching capability of the gold nanoparticles and the possibility of developing functional nucleic acids for the detection of other metal ions, this study extends the application of oligonucleotides to a point-of-care detection system for the detection of multiple harmful metal ions in body fluids.

Enhancement of glucose oxidase production in batch cultivation of recombinant Saccharomyces cerevisiae: optimization of oxygen transfer condition.

A. KAPAT, J.‐K. JUNG AND Y.‐H. PARK. 2001.

Color-tunable photoluminescent fullerene nanoparticles.

Highly water-soluble and color-tunable photoluminescent fullerene nanoparticles are synthesized by using tetraethylene glycol (TEG) and lithium hydroxide as a catalyst. The maximum PL emission changes depend on the contents of the remaining π-conjugation in oxidized C(60), which is partially covalently conjugated with TEG. The PL behavior is attributed to an electronic transition change due to the distortion of symmetrical C(60).

Influence of agitation speed on production of curdlan by Agrobacterium species

Abstract Influence of dissolved oxygen level on production of curdlan by Agrobacterium species was investigated. Preliminary shake flask experiments showed that both cell growth and curdlan production were higher at a smaller volume of medium (50–100 ml in 500 ml flasks). As culture volume increased from 100 ml to 300 ml, both cell concentration and curdlan production decreased, indicating that higher oxygen transfer is required for a higher production of curdlan. Time profiles of cell concentration and curdlan production in a 5-liter jar fermentation at different agitation speeds, ranging from 300 rpm to 700 rpm, supported the fact of higher production of curdlan at higher oxygen transfer rate observed in shake flask cultures. At a higher agitation speed (600 rpm), the highest curdlan production (64.4 g/l) was obtained in 120 h of a batch fermentation. However, curdlan production was not improved at the higher agitation speed (700 rpm). For the mass production of curdlan, fermentation was performed in a 300-liter fermenter under the condition where the same volumetric oxygen transfer coefficient was obtained as in 5-liter jar fermentation. As high as 9.28 kg of curdlan with a final concentration of 58 g/l was obtained in 120 h batch cultivation, enlarging the potential in the industrial production of curdlan.

A simple, fast and highly sensitive assay for the detection of telomerase activity

A highly sensitive and rapid PCR-free telomerase activity assay has been developed that uses SYBR Green intercalation into the G-quadruplex structures in the presence of K(+).

Bifunctional Nanoparticles Constructed Using One‐Pot Encapsulation of a Fluorescent Polymer and Magnetic (Fe3O4) Nanoparticles in a Silica Shell

Integration of biocompatible silica with a fluorescent polymer (PDDF) and superparamagnetic iron oxide nanoparticles (Fe3 O4 ) to form uniform core-shell nanostructures has the great potential to form particles for use in multimodal bioimaging applications. Core-shell nanoparticles (PDDF/Fe3 O4 @SiO2 ) exhibit fluorescent and magnetic properties that are favorable for their use in magnetic separation and guiding applications, as well as optical and magnetic resonance (MR) imaging capabilities. With the biological analysis in an in vitro intracellular permeation and cytotoxicity test, chemical conjugation of the surface using folic acid (FA) molecules can provide the nanoparticles with cell-targeting properties, localizing the nanoparticles to folate receptors (FRs) on target KB cells that over-express the FRs.

A novel fluorescent nanoparticle composed of fluorene copolymer core and silica shell with enhanced photostability.

A variety of fluorescent nanoparticles have been developed for demanding applications such as optical biosensing and fluorescence imaging in live cells. Silica-based fluorescent nanoparticles offer diverse advantages for biological applications. For example, they can be used as labeling probes due to their low toxicity, high sensitivity, resolution, and stability. In this research, a new class of highly fluorescent, efficient nanoparticles composed of a newly synthesized poly[di(2-methoxy-5-(2-ethylhexyloxy))-2,7-(9,9-dioctyl-9H-fluorene)] (PDDF) core and a silica shell (designated as PDDF@SiO(2)) were prepared using a simple reverse micelle method, and their fluorescent properties were evaluated using methods such as single-dot photoluminescence measurements. The enhanced photostability of the particles and their potential applications for bioanalysis are discussed in this article. The morphology, size, and fluorescent properties for prepared PDDF@SiO(2) nanoparticles were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and photoluminescence spectroscopy. The prepared particles size, which was approximately 60 nm, resulted in an excellent colloidal stability in a physiological environment. The photobleaching dynamics, total numbers of emitted photons (TNEP) and statistical measurements of individual nanoparticles were observed using laser scanning fluorescence microscopy to assess the structure and photostability of PDDF@SiO(2) nanoparticles. Additionally, PDDF@SiO(2) nanoparticles were used in cell toxicity and permeation tests for biological analyses, demonstrating a great potential for use as powerful, novel materials within the emerging fields of biosensing and biomedical engineering.

Bimodal perfluorocarbon nanoemulsions for nasopharyngeal carcinoma targeting.

PurposeThe aim of this study was to perform the detection of folate receptor (FR)-positive tumors with a bimodal imaging contrast agent, a perfluorocarbon (PFC)/rhodamine nanoemulsion, providing both 19F-based magnetic resonance imaging (MRI) and fluorescence imaging capabilities.ProceduresThe PFC/rhodamine nanoemulsion was further infused with phospholipid-anchored folate to improve the ability to target FR-expressing tumors. The preferential accumulation of the FR-targeted bimodal nanoemulsion in FR-positive tumor sites was monitored by both 19F-MRI and optical imaging.ResultsThe FR-targeted PFC nanoemulsion had no significant effect on cell viability, and the size and fluorescence signal of PFC nanoemulsion were very stable. These nanoprobes were successfully delivered into FR-positive tumor xenograft models and showed significantly enhanced signal intensities of 19F-MRI and fluorescence imaging in the tumor area.ConclusionsThe folate-PFC/rhodamine nanoemulsion has a great potential to serve as a useful optical and 19F-MRI agent for the diagnosis and targeting of FR-positive tumor.

Effects of agitation and aeration on the production of extracellular glucose oxidase from a recombinant Saccharomycescerevisiae

Abstract A recombinant strain of Saccharomyces cerevisiae, GAL-GO2, was developed to facilitate the production of extracellular glucose oxidase (GOD). The recombinant strain secreted 85% (8.7 U/ml) of the total GOD (10.3 U/ml) produced in shake flask culture. For further enhancement of GOD production, optimization of the speed of agitation and the rate of aeration in a stirred tank fermentor was carried out. Response surface methodology with appropriate statistical experimental design was employed for this purpose. The maximal level of extracellular GOD was achieved when the speed of agitation and the rate of aeration were 420 rpm and 0.25 vvm, respectively. The enzyme production was increased by 74% compared to the level obtained under unoptimized conditions.

The cell adhesion molecule L1 promotes gallbladder carcinoma progression in vitro and in vivo

Recent studies have demonstrated that the cell adhesion molecule, L1, is expressed in several malignant tumor types and its expression correlates with tumor progression and metastasis. However, the role of L1 in gallbladder carcinoma (GBC) remains unclear. Here, we demonstrate that L1 is expressed in GBC cells and plays an important role in the growth, motility, invasiveness, and adhesiveness of GBC cells. Specific depletion or overexpression of L1 in the GBC cell lines JCRB1033 and SNU-308, respectively, was achieved by lentivirus-mediated transduction and expression of an L1 mRNA-specific short hairpin RNA or full-length human L1. Stable depletion of L1 led to a significant decrease in GBC cell proliferation, migration and invasion, as well as decreased intracellular signaling through AKT and FAK. Overexpression of L1 in GBC cells enhanced these cellular activities. In a GBC xenograft nude mouse model, suppression of L1 markedly reduced tumor growth and increased the survival of tumor-bearing mice whereas L1 overexpression stimulated tumorigenicity. Taken together, these results suggest that L1 plays a crucial role in GBC progression and may be a novel therapeutic target in GBC treatment.