Jae Sup Shin

Amperometric Cholesterol Biosensor Using Layer-by-Layer Adsorption Technique on Polyaniline-coated Polyester Films

An amperometric cholesterol biosensor was fabricated using polyaniline-coated polyester films. Polyaniline was dissolved in chloroform with camphorsulfonic acid, and polystyrene was added to this solution. Using this mixed solution, the coating was placed onto polyester films. Cholesterol oxidase was immobilized onto these films using an electrostatic layer-by-layer adsorption technique. Poly(diallyldimethylammonium chloride) was used as the counter ion source. The level of adsorption was examined and evidence of layer-by-layer adsorption was investigated using a quartz crystal microbalance (QCM). A cholesterol biosensor was fabricated from these films as a working electrode, and it was used to measure the cholesterol concentration.

Sensing Capability of Molecularly Imprinted Self-Assembled Monolayer Using Terphenylpropanethiol

A molecularly imprinted self-assembled monolayer (SAM) was fabricated on a gold plate by forming a monolayer with both thiol compound and the template molecule, and removing the template molecules by solvent extraction. 1-Dodecanethiol (DDT), 1-hexadecanethiol (HDT), [1,1′:4′,1′′-terphenyl]-4-thiol (TPT), and [1,1′:4′,1′′-terphenyl]-4-propanethiol (TPPT) were used as the thiol compounds. Cholesterol was used as the template molecule, and cholesterol, cholic acid, and deoxycholic acid were used as the substrate molecules. Cyclic voltammograms were obtained using these imprinted gold plates as a working electrode, with Ag/AgCl reference electrode and Pt counter-electrode. Potassium ferricyanide was used as a background material for oxidation and reduction. These imprinted monolayers were capable of discriminating cholesterol that had been imprinted. The order of sensing capability of the thiol compounds was TPPT > HDT > TPT > DDT.

Recognizing Amino Acid Chirality with Surface-Imprinted Polymers Prepared in W/O Emulsions

A molecularly imprinted polymer was prepared by a surface molecular imprinting technique in water-in-oil (W/O) emulsion. In this technique, the solid polymer, which is molecularly imprinted at the internal cavity surface, is prepared by polymerizing W/O emulsions consisting of a water-soluble imprinted molecule, a functional host molecule, an emulsion stabilizer, and a crosslinking agent. Dioleoyl phosphate was used as an emulsion stabilizer, and this compound also acted as a monomer and a host functional group in the imprinted cavity. Divinylbenzene was used as a crosslinker. Tryptophan methyl ester and phenylalanine methyl ester were used as the target template materials. These imprinted polymers exhibited enantiomeric selectivity in absorption experiments, and the maximum separation factor was 1.58. The enantiomeric selectivity with tryptophan methyl ester was higher than that with phenylalanine methyl ester.

Latent imidazole curing agents by microencapsulation with copolymers

ABSTRACT The encapsulation of imidazoles was conducted to prepare the latent imidazole curing agents by using the copolymers as the wall materials. The latent imidazole curing agents are essential to manufacturing anisotropic conducting films (ACFs). The copolymers, which were used for the encapsulation, were the copolymers of methacrylic acid (MAA) and octadecyl methacrylate (ODMA). The method for encapsulation was the spray-drying method. The curing behaviors of the microcapsules to epoxy resin were investigated using a differential scanning calorimeter (DSC). Using the encapsulated microcapsules, the curing reaction to epoxy resin was conducted at 150°C and 180°C, and the curing time was measured. The fabricated microcapsules using the copolymers showed an improved latent character compared with the previously reported results.

Cytochrome c assembly on fullerene nanohybrid metal oxide ultrathin films

The immobilization of Cyt. c (cytochrome c) on C60 (fullerene) nanohybrid TiO2 (titanium dioxide) gel films assembled with C60, Ti(O–nBu)4 and Cyt. c was realized by a surface sol–gel process. Interestingly, C60 was used without any surface modification of the film formation and exhibited good electrochemical performance. Additionally, the surface morphologies of the TiO2 and TiO2/C60 nanocomposite thin films showed remarkable uniformity over a wide area, however, the surface morphology depends on the deposition of Cyt. c, which densely covers the surface with adsorbed Cyt. c molecules. The cyclic voltammetry of the outer-most fullerene films revealed high stability, as well as, a pair of current peaks characteristic of a weak redox system with anodic and cathodic peak potentials at 0.262 V and 0.137 V. The electrochemical properties of thin films can be attributed to the redox system of the C60 layer deposited on the TiO2 gel layer. A pair of well-defined quasi-reversible redox peaks generated by Cyt. c are easily achieved because of the efficient assembly on the C60-modified electrode. In this work, we suggest the efficient introduction of C60 into a TiO2 gel matrix, evaluating the electrochemical characteristics of Cyt. c assembly.

One-component epoxy adhesive for repair of cell phone board

Abstract The development of a one-component epoxy adhesive for cell phone board repair was described. The most important goal of this study is to obtain long storage stability in conjunction with the curing reaction process at a relatively low temperature of 95 °C. Bisphenol-A type, bisphenol-F type, and NBR-based epoxy resins were used as the basic resins. Dicyandiamide (DICY) was used as a curing agent, and 2-methylimidazole (2MI) was used as an accelerator. 2MI was encapsulated using a copolymer of methacrylic acid and dodecyl methacrylate to achieve latent curing performance. After mixing the epoxy resin with DICY and encapsulated 2MI, this curing system showed excellent storage stability with almost no viscosity increase for 2 months at 20 °C, and full curing was achieved at 95 °C for 50 min. We determined the optimum formulation of the epoxy adhesive for adhesion of a cell phone board after the measurement of physical properties.

Pectin-Coated Curcumin-Chitosan Microparticles Crosslinked with Mg2+ for Delayed Drug Release in the Digestive System

Curcumin-loaded chitosan-pectin microparticles based on polymeric microencapsulation were prepared by two methods to delay the release of curcumin in the digestive system, employing Mg2+ as a pectin-crosslinking agent for the first time. Pectin-coated curcumin-chitosan microparticles (C-g-PMg) and curcumin-loaded chitosan-pectin composite microparticles (C-PMg-g) were formulated, and their release profiles at pH 1.2 and at pH 6.8 were tested. The former (C-g-PMg) showed slower curcumin release profiles than the latter (C-PMg-g) because the C-g-PMg are composed of two layers, a chitosan-glutaraldehyde layer and a pectin-Mg2+ layer, which together hold the curcumin for a longer duration. Of the pectin-coated microparticles, those crosslinked with Mg2+ showed a slower release rate than those crosslinked with Ca2+, but the former showed a faster release rate at pH 6.8 in the presence of pectinase, acting as a promising drug delivery carrier for treating a colonic disease. The pectin layer and the pectin-crosslinking agent play a vital role in prolonging the release of curcumin until pectin is degraded by pectinase.

Polymerizable ultraviolet stabilizers for unsaturated polyester-based bulk molding compounds

Monomeric compounds that protect against ultraviolet (UV) exposure, e.g. 2-hydroxy-4-acryloyloxybenzophenone (HABP), 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl methacrylate (BTEM), and 4-acryloyloxy-1,2,2,6,6-pentamethylpiperidine (APMP), were used as UV stabilizers for unsaturated polyester-based bulk molding compounds (BMCs). HABP and APMP were synthesized by reacting acryloyl chloride with 2,4-dihydro-xybenzophenone and 1,2,2,6,6-pentamethyl-4-piperidinol, respectively. The molded BMC samples were obtained using actual formulations containing these UV stabilizers, and the UV stability of the samples was estimated using a color difference meter. The results showed that HABP and BTEM afforded good protection against UV light, and these compounds showed a synergistic effect. APMP also showed a synergistic effect, but only when a small amount of the compound was used. These results were compared with the results obtained when copolymers of HABP and BTEM were used as UV stabilizers. The results showed that the polymerizable UV stabilizers demonstrated better protection against UV exposure, when they were added directly to the formulation of BMC, compared to the addition of copolymers as UV stabilizers.