Seong-Soo Kim

A highly sensitive plasma-based amyloid-β detection system through medium-changing and noise cancellation system for early diagnosis of the Alzheimer's disease

We developed an interdigitated microelectrode (IME) sensor system for blood-based Alzheimer’s disease (AD) diagnosis based on impedimetric detection of amyloid-β (Aβ) protein, which is a representative candidate biomarker for AD. The IME sensing device was fabricated using a surface micromachining process. For highly sensitive detection of several tens to hundreds of picogram/mL of Aβ in blood, medium change from plasma to PBS buffer was utilized with signal cancellation and amplification processing (SCAP) system. The system demonstrated approximately 100-folds higher sensitivity according to the concentrations. A robust antibody-immobilization process was used for stability during medium change. Selectivity of the reaction due to the affinity of Aβ to the antibody and the sensitivity according to the concentration of Aβ were also demonstrated. Considering these basic characteristics of the IME sensor system, the medium change was optimized in relation to the absolute value of impedance change and differentiated impedance changes for real plasma based Aβ detection. Finally, the detection of Aβ levels in transgenic and wild-type mouse plasma samples was accomplished with the designed sensor system and the medium-changing method. The results confirmed the potential of this system to discriminate between patients and healthy controls, which would enable blood-based AD diagnosis.

Processing and Reducing Factors of Difenoconazole during Ginseng Processing

This study was performed to acquire processing and reducing factors of difenoconazole during ginseng processing, and to establish the maximum residue limits of ginseng and its commodities. Difenoconazole was used in two fields (Wonju and Icheon) containing 6 year old ginseng plants. The amount of residue at Wonju and Icheon were

Ultra-selective detection of Fe2+ ion by redox mechanism based on fluorescent polymerized dopamine derivatives

Polydopamine (PDA) is considered as a fluorescent molecule, however, the molecular structure and degree of polymerization that yield the most efficient fluorescence have yet to be identified. Here, we first present the fluorescence origin of polymerized dopamine derivatives (pDA) and their extraordinary behavior on the ultra-selective recognition of Fe2+ ions. Dopamine molecules are polymerized to 5,6-dihydroxyindole-rich pDA in basic conditions, followed by readily oxidizing to indole-5,6-quinone-rich pDA by dropping the pH to strongly acidic conditions. It was clearly demonstrated that oligomeric dopamine molecules were water-soluble with intense fluorescence (F-ODA, n = 3–4), while polymeric dopamine molecules were water-insoluble without fluorescence (PDA, n > 5). Also, F-ODA was dramatically selective to Fe2+ ions contradicting previous studies, and their unique binding mechanism was described through the redox potential analysis.

A phase-reversible Pd containing sphere-to-bridge-shaped peptide nanostructure for cross-coupling reactions

A sphere-to-bridge-shaped peptide nanostructure was constructed from a tyrosine-rich peptide (H-YYACAYY-OH) via mediating Pd2+ ions as well as changing temperature. This novel assembly technique provided a recyclable Pd nano-catalyst with a function of reversible thermal phase transition between the homogeneous and heterogeneous states for cross-coupling reactions.