Chiyoung Park

Enzyme Responsive Nanocontainers with Cyclodextrin Gatekeepers and Synergistic Effects in Release of Guests

The cyclodextrin covered porous silica nanoparticles (Si-MPs) exhibited enzyme responsive characteristics. The cyclodextrin gatekeepers on the surface of Si-MPs can be hydrolyzed by a-amylase to release guest molecules from the porous reservoir. The ester linkage in the stalk part of the cyclodextrin gatekeeper can also be cleaved by lipase to release guests from the channel. Our approach would provide a unique methodology for controlled delivery systems.

Glutathione‐Induced Intracellular Release of Guests from Mesoporous Silica Nanocontainers with Cyclodextrin Gatekeepers

Mesoporous silica nanoparticles (Si-MPs) have been demonstrated to be excellent hosts for molecules of various sizes, shapes, and functionalities. [ 5 ] The organically functionalized Si-MPs have unique structural features such as environmentally stable mesoporous structures, large surface area, tunable pore size, and well-defi ned surface properties. [ 3 ] In particular, the facile surface functionalization of Si-MPs and their effi cient internalization into cells provided Si-MPs with unique properties for stimuli-responsive controlled delivery applications. [ 2 , 4 ]

A highly efficient organic sensitizer for dye-sensitized solar cells

We have synthesized a highly efficient organic dye for a dye-sensitized solar cell; the overall solar-to-energy conversion efficiency was 9.1% at AM 1.5 illumination (100 mW cm(-2)): short-circuit current density (J(sc)) = 18.1 mA cm(-2), open circuit photovoltage (V(oc)) = 743 mV and fill factor (ff) = 0.675.

Cyclodextrin-covered gold nanoparticles for targeted delivery of an anti-cancer drug

We report on the therapeutic ability of a novel cyclodextrin-covered gold nanoparticle (AuNP) carrier for noncovalent encapsulation of an anti-cancer drug. The surface of the AuNPs was functionalized with cyclodextrin as a drug pocket, anti-epidermal growth factor receptor (anti-EGFR) antibody as a targeting moiety, and poly(ethyleneglycol) (PEG) as an anti-fouling shell. β-Lapachone, an anti-cancer drug, was efficiently encapsulated into the hydrophobic cavity of cyclodextrin on the surface of the AuNP carriers (AuNP-1). The glutathione-mediated release of β-lapachone from the surface of AuNP-1 was demonstrated by an experiment with MCF-7 (low glutathione concentration) and A549 cells (high glutathione concentration). We also show that the introduction of an anti-EGFR antibody onto the AuNP carriers (AuNP-2) increased the intracellular uptake of AuNP carriers as compared with AuNP-1, which does not contain a targeting ligand. In the in vitro cytotoxicity study, AuNP-2 with β-lapachone exhibited a higher apoptosis effect than that caused by AuNP-1 with β-lapachone. This work suggests that AuNPs covered with cyclodextrin and tumor-targeting ligands may find useful applications for the development of nanoparticles with therapeutic and diagnostic modalities.

Carbon Nanotubes/Heteroatom‐Doped Carbon Core–Sheath Nanostructures as Highly Active, Metal‐Free Oxygen Reduction Electrocatalysts for Alkaline Fuel Cells

A facile, scalable route to new nanocomposites that are based on carbon nanotubes/heteroatom-doped carbon (CNT/HDC) core-sheath nanostructures is reported. These nanostructures were prepared by the adsorption of heteroatom-containing ionic liquids on the walls of CNTs, followed by carbonization. The design of the CNT/HDC composite allows for combining the electrical conductivity of the CNTs with the catalytic activity of the heteroatom-containing HDC sheath layers. The CNT/HDC nanostructures are highly active electrocatalysts for the oxygen reduction reaction and displayed one of the best performances among heteroatom-doped nanocarbon catalysts in terms of half-wave potential and kinetic current density. The four-electron selectivity and the exchange current density of the CNT/HDC nanostructures are comparable with those of a Pt/C catalyst, and the CNT/HDC composites were superior to Pt/C in terms of long-term durability and poison tolerance. Furthermore, an alkaline fuel cell that employs a CNT/HDC nanostructure as the cathode catalyst shows very high current and power densities, which sheds light on the practical applicability of these new nanocomposites.

Cyclodextrin-covered organic nanotubes derived from self-assembly of dendrons and their supramolecular transformation

The dendritic building blocks with a focal pyrene unit self-organize into vesicles in aqueous phase. The in situ inclusion of the focal pyrene units into the cavity of β- or γ-cyclodextrin (CD) induces self-assembled organic nanotubes with an average outer diameter of ≈45 nm and inner diameter of 22 nm. The surface of the nanotube is covered with CD. Therefore, the functional group on the surface of the nanotube is controlled simply by modifying the functionality of CD. The removal of CD from the nanotube with poly(propylene glycol) reversibly generates vesicles. This work provides an efficient methodology not only to create an additional class of CD-covered organic nanotubes but also to exhibit reversible transformation of nanotubes and vesicles triggered by the motifs of dendron self-assembly, CD inclusion, and pseudorotaxane formation.

Photoinduced Release of Guest Molecules by Supramolecular Transformation of Self-Assembled Aggregates Derived from Dendrons**

Self-assembly provides a unique way to create supramolecular functional materials. Since a variety of supramolecules have been reported to date, the control of architectures and functions triggered by external stimuli has always been a challenging subject. Dendrimers and dendrons have been of great interest in a variety of scientific fields because of their unique assembly characteristics and functional performances. Recently, we investigated the self-assembly characteristics of amide dendrons and revealed that the dendrons can self-assemble into hierachical nanostructures under various conditions. The supramolecular structure of the amide dendrons can be controlled by tuning the focal functionality of the dendrons. For example, photoisomerizable or photocleavable units introduced at the focal moiety could be utilized to control the photoresponsive functions of dendron-based supramolecular materials. In this regard, we envisioned that the incorporation of stimuli-responsive functional groups in the amide dendrons would be an effective approach toward the construction of well-defined stimuli-responsive nanomaterials (Scheme 1). The formation of the dendritic architecture is one of the important factors for the self-organization of the amide dendrons. Thus, the self-assembly of amphiphilic dendrons would provide opportunities not only for structural versatility but also for functional modulation of the stimuliresponsive materials. Herein we describe the rational design of dendritic building blocks with a photocleavable unit that can selfassemble into a vesicular structure and can undergo a structural transformation on application of a external photostimulus (Figure 1a,b). Furthermore, the introduction of a photoisomerizable chemical modulator at the focal moiety of the dendron would provide a tool to control the photoactivated release of guest molecules from the supramolecular aggregates of the dendrons (Figure 1c,d). Thus, we have investigated the photoresponsive release behaviors not only

Colloidal inverse bicontinuous cubic membranes of block copolymers with tunable surface functional groups.

Analogous to the complex membranes found in cellular organelles, such as the endoplasmic reticulum, the inverse cubic mesophases of lipids and their colloidal forms (cubosomes) possess internal networks of water channels arranged in crystalline order, which provide a unique nanospace for membrane-protein crystallization and guest encapsulation. Polymeric analogues of cubosomes formed by the direct self-assembly of block copolymers in solution could provide new polymeric mesoporous materials with a three-dimensionally organized internal maze of large water channels. Here we report the self-assembly of amphiphilic dendritic-linear block copolymers into polymer cubosomes in aqueous solution. The presence of precisely defined bulky dendritic blocks drives the block copolymers to form spontaneously highly curved bilayers in aqueous solution. This results in the formation of colloidal inverse bicontinuous cubic mesophases. The internal networks of water channels provide a high surface area with tunable surface functional groups that can serve as anchoring points for large guests such as proteins and enzymes.

Acute Renal Failure Due to Acute Tubular Necrosis Caused by Direct Invasion of Orientia tsutsugamushi

ABSTRACT We describe a scrub typhus patient with acute renal failure for whom a diagnosis was made based on serology as well as immunohistochemical (IHC) staining and an electron microscopic examination (EM) of a renal biopsy specimen. For our case, we demonstrated by IHC staining and EM that renal failure was caused by acute tubular necrosis due to a direct invasion of Orientia tsutsugamushi.

Controlling volume shrinkage in soft lithography through heat-induced cross-linking of patterned nanofibers.

When poly(isopropylidene diallylmalonate) rich in threo-disyndiotactic sequences (st(rich)-2) was utilized as a cross-linkable ink for microcontact printing, the resultant submicrometer-scale patterns featuring 700 and 300 nm wide stripes were successfully insolubilized while maintaining their high dimensional integrity by heat-induced cross-linking with elimination of CO(2) and acetone. In sharp contrast, although the thermal properties and reactivities of a polymer rich in threo-diisotactic sequences (it(rich)-2) and a polymer having low stereoregularity (2(low)) are little different from those of st(rich)-2, the patterns printed with these reference polymers collapsed considerably upon heating as a result of a volume shrinkage effect. The striking difference between st(rich)-2 and the other two polymers most likely arises from the nanofiber-forming character of st(rich)-2, where the printed stripes are porous and much less affected by the volume shrinkage of individual nanofibers.