Biomedical subjects

Youn Sang Kim

Publications and source records attributed to Youn Sang Kim.

6 recordsLinked to original sources

PubMed2006

Hydrophilic composite elastomeric mold for high-resolution soft lithography.

Here, we introduce a nanopatternable hydrophilic composite elastomer highly desirable for both nanostructure patterning via solvent-assisted micromolding (SAMIM) and microcontact printing of polar inks. This composite precursor is prepared by blending two UV-curable materials, Norland Optical Adhesives (NOA) 63 and poly(ethylene glycol) diacrylate (PEGDA), in an appropriate ratio; upon UV polymerization, a nanopatternable elastomer with preferential permeability both to aqueous and organic solvent is fabricated. Using this composite mold, nanoscale SAMIM of poly(4-vinylpyridine) (P4VP) and microcontact printing of a polar biomolecule, bovine serum albumin (BSA), was successfully demonstrated, paving the way for facile and efficient reproduction of various nanopatterns and a biomolecule-printed array platform.

Elastomers↗

PubMed2006

Multilayer transfer printing on microreservoir-patterned substrate employing hydrophilic composite mold for selective immobilization of biomolecules.

In this study, we introduce a hydrophilic composite mold with elasticity and moderate water permeability, suitable for transferring water-soluble polar molecules such as polyelectrolyte multilayer. This composite mold is constructed from two UV-curable polymers-Norland Optical Adhesives (NOA) 63, a urethane-related polymer, and poly(ethylene glycol) diacrylate (PEGDA). The mixture of inherently hard NOA 63 and hydrogel precursor, PEGDA, resulted in an optically transparent mold with some degree of elasticity and enhanced water permeability upon UV polymerization. Employing the NOA 63-PEGDA composite mold, a polyelectrolyte multilayer comprising alternate thin layers of poly(acrylic acid) (PAA) and poly(acrylamide) (PAAm) was transfer-printed onto arrays of microreservoir-patterned substrate to selectively prevent unwanted adsorption of biomolecules on the protruding surface. Antibody was immobilized selectively inside the microreservoirs where multilayer was not transferred, and a specific antibody binding reaction was detected inside the microreservoirs. Furthermore, the potential of this composite mold as a convenient tool for constructing a biosensor for detecting Escherichia coli (E. coli) O157:H7 was explored.

Antibodies↗

PubMed2006

Nonheme iron(II) complexes of macrocyclic ligands in the generation of oxoiron(IV) complexes and the catalytic epoxidation of olefins.

Mononuclear nonheme oxoiron(IV) complexes bearing 15-membered macrocyclic ligands were generated from the reactions of their corresponding iron(II) complexes and iodosylbenzene (PhIO) in CH(3)CN. The oxoiron(IV) species were characterized with various spectroscopic techniques such as UV-vis spectrophotometer, electron paramagnetic resonance, electrospray ionization mass spectrometer, and resonance Raman spectroscopy. The oxoiron(IV) complexes were inactive in olefin epoxidation. In contrast, when iron(II) or oxoiron(IV) complexes were combined with PhIO in the presence of olefins, high yields of epoxide products were obtained. These results indicate that in addition to the oxoiron(IV) species, there must be at least one more active oxidant (e.g., Fe(IV)-OIPh adduct or oxoiron(V) species) that effects the olefin epoxidation. We have also demonstrated that the ligand environment of iron catalysts is an important factor in controlling the catalytic activity as well as the product selectivity in the epoxidation of olefins by PhIO.

Alkenes↗

PubMed2005

Selective patterning and immobilization of biomolecules within precisely-defined micro-reservoirs.

Herein, we present the fabrication of well-defined micro-reservoirs and a simple strategy to immobilize biomolecules selectively inside the reservoirs. The micro-reservoirs are fabricated using a photocurable prepolymer, which enables the formation of concrete structures with high-fidelity, so that the reservoirs are spatially-segregated from each other by rigid physical barriers. For the directed binding of the protein, two steps are involved. First, poly(ethylene glycol) (PEG) is contact-printed on those areas where the protein binding is not desired, and next, protein binding is promoted where desired via carbodiimide chemistry. Fluorescein-tagged albumin is successfully immobilized inside the micro-reservoirs and microchannel arrays with high sensitivity, regardless of the sizes of the reservoirs and channels. The proposed system can be used for constructing multi-functional biosensors by immobilizing individual bioorganisms specifically in each micro-reservoir or microchannel.

Albumins↗

PubMed2005

Highly effective fluorescent and colorimetric sensors for pyrophosphate over H2PO4- in 100% aqueous solution.

[Structure: see text]. This study demonstrated that Zinpyr-1*Zn2+ acts as a fluorescent and colorimetric sensor for pyrophosphate at pH 7.4. In addition, Zinpyr-1*Cu2+ and DIARB-1*Cu2+ complexes were found to act as selective fluorescent sensors for pyrophosphate. Furthermore, the chemosensors Zinpyr-1*Zn2+ and Zinpyr-1*Cu2+ show highly selective and ratiometric fluorescence changes for pyrophosphate compared with H2PO4-.

Biosensing Techniques↗

PubMed2005

Chemically nanopatterned surfaces using polyelectrolytes and ultraviolet-cured hard molds.

Polymer transfer printing of poly(acrylic acid) onto a polyelectrolyte multilayer platform resulted in chemically nanopatterned surfaces with well-defined structures and both positive and negative surface functionalities. A commercially available urethane-related photopolymer cured by ultraviolet light was used to make stamps for contact printing with a range of submicrometer down to 80 nm features because of its outstanding mechanical stability and inherent softening transition above 48 degrees C.

Acrylic Resins↗