Hyo-Yong Ahn

Changes in clinicopathological features and survival after gastrectomy for gastric cancer over a 20-year period.

The pattern of gastric cancer in the Western world is changing, with an increased proportion of tumours in the upper stomach. The aim of this study was to investigate changes in clinicopathological features and survival of patients with resected gastric cancer at a single institution, in an area of high incidence in the Far East.

Concave Rhombic Dodecahedral Au Nanocatalyst with Multiple High-Index Facets for CO2 Reduction

A concave rhombic dodecahedron (RD) gold nanoparticle was synthesized by adding 4-aminothiophenol (4-ATP) during growth from seeds. This shape is enclosed by stabilized facets of various high-indexes, such as (331), (221), and (553). Because it is driven thermodynamically and stabilized by 4-ATP ligands, the concave RD maintains its structure over a few months, even after rigorous electrochemical reactions. We discussed the mechanism of the shape evolution controlled by 4-ATP and found that both the binding energy of Au-S and the aromatic geometry of 4-ATP are major determinants of Au atom deposition during growth. As a possible application, we demonstrated that the concave RD exhibits superior electrocatalytic performance for the selective conversion of CO2 to CO in aqueous solution.

Amino-acid- and peptide-directed synthesis of chiral plasmonic gold nanoparticles

Understanding chirality, or handedness, in molecules is important because of the enantioselectivity that is observed in many biochemical reactions1, and because of the recent development of chiral metamaterials with exceptional light-manipulating capabilities, such as polarization control2–4, a negative refractive index5 and chiral sensing6. Chiral nanostructures have been produced using nanofabrication techniques such as lithography7 and molecular self-assembly8–11, but large-scale and simple fabrication methods for three-dimensional chiral structures remain a challenge. In this regard, chirality transfer represents a simpler and more efficient method for controlling chiral morphology12–18. Although a few studies18,19 have described the transfer of molecular chirality into micrometre-sized helical ceramic crystals, this technique has yet to be implemented for metal nanoparticles with sizes of hundreds of nanometres. Here we develop a strategy for synthesizing chiral gold nanoparticles that involves using amino acids and peptides to control the optical activity, handedness and chiral plasmonic resonance of the nanoparticles. The key requirement for achieving such chiral structures is the formation of high-Miller-index surfaces ({hkl}, h ≠ k ≠ l ≠ 0) that are intrinsically chiral, owing to the presence of ‘kink’ sites20–22 in the nanoparticles during growth. The presence of chiral components at the inorganic surface of the nanoparticles and in the amino acids and peptides results in enantioselective interactions at the interface between these elements; these interactions lead to asymmetric evolution of the nanoparticles and the formation of helicoid morphologies that consist of highly twisted chiral elements. The gold nanoparticles that we grow display strong chiral plasmonic optical activity (a dis-symmetry factor of 0.2), even when dispersed randomly in solution; this observation is supported by theoretical calculations and direct visualizations of macroscopic colour transformations. We anticipate that our strategy will aid in the rational design and fabrication of three-dimensional chiral nanostructures for use in plasmonic metamaterial applications.Chirality can be ‘encoded’ into gold nanoparticles by introducing chiral amino acids or peptides during the growth process, leading to the formation of helicoid morphologies.

Virus Templated Gold Nanocube Chain for SERS Nanoprobe

A M13 virus based SERS nanoprobe is presented. Gold nanocubes closely aligned into chains along the length of the virus intensify Raman signals of various reporter molecules serving as specific labels. An antibody is expressed at one end to detect the analyte. This new SERS nanoprobe holds promise for infinitesimal and multiplexed detection of any antigen.

Phase transformation from hydroxyapatite to the secondary bone mineral, whitlockite

Whitlockite (WH: Ca18Mg2(HPO4)2(PO4)12) is the second most abundant mineral in hard tissues, but its precipitation mechanism or role in the body system is poorly understood. Here, using a newly discovered synthetic method for WH, we investigated the kinetic mechanism for the precipitation of WH under physiologically similar conditions, excluding any effects of toxic ions. Based on systematically classified stages in the precipitation process of WH, we monitored the transformation of calcium phosphate phases from neutral pH to acidic pH with the addition of H3PO4. The study revealed that at 70 °C, hydroxyapatite (HAP: Ca10(PO4)6(OH)2) transforms into dicalcium phosphate dihydrate (DCPD: CaHPO4·2H2O) and then into WH in the presence of Mg2+ ions as the pH decreases. The transformation process involves multiple intermediates, the stability of which depends on the cation (Ca and Mg) activities and the solution pH. WH is the most stable calcium phosphate compound below pH 4.2, whereas HAP is the most stable around neutral pH. We also found that Mg2+ ions, which are known to block the growth of HAP, can play a key role in WH formation. This study provides a new insight into the interplay of biologically important calcium phosphate compounds.

Extended gold nano-morphology diagram: synthesis of rhombic dodecahedra using CTAB and ascorbic acid

The shape control of gold nanoparticles is still one of the most important challenges remaining to achieve geometry-dependent properties. Thus far, several strategies have been developed to control the shape of nanoparticles, such as adding capping agents and diverse additives or adjusting the temperature and pH. Here, we used an already established seed-mediated method which allowed us to focus on controlling the growth stage. Cetyltrimethylammonium bromide (CTAB) and ascorbic acid (AA) were used as the ligand and the reducing agent, respectively, without using any additional additives during the growth stage. We investigated how the relative ratio of CTAB and AA concentrations can be a major determinant of the nanoparticle shape over wide concentration ranges of CTAB (15 mM to 45 mM) and AA (3 mM to 71 mM). As a result, a morphology diagram was constructed experimentally which covers the growth conditions of rods, cuboctahedra, cubes and rhombic dodecahedra. The trends in the morphology diagram emphasize the importance of the interplay between CTAB and AA and can provide useful guidelines for designing various faceted geometries. Furthermore, we demonstrated the synthesis of rhombic dodecahedral gold nanocrystals in a CTAB and AA system for the first time.

Effect of neoadjuvant chemotherapy on postoperative morbidity and mortality in patients with locally advanced gastric cancer.

Neoadjuvant chemotherapy has been shown to improve the rate of complete (R0) resection and downstaging in patients with localized gastric cancer. There are few reports, however, regarding its impact on postoperative morbidity and mortality. The aims of this study were to analyse complication and mortality rates after neoadjuvant chemotherapy using a modified regimen of folinic acid, 5‐fluorouracil and oxaliplatin (mFOLFOX6) for locally advanced gastric cancer (AGC), compared with rates in patients who underwent surgery without neoadjuvant chemotherapy.

Double-Layer Graphene Outperforming Monolayer as Catalyst on Silicon Photocathode for Hydrogen Production.

Photoelectrochemical cells are used to split hydrogen and oxygen from water molecules to generate chemical fuels to satisfy our ever-increasing energy demands. However, it is a major challenge to design efficient catalysts to use in the photoelectochemical process. Recently, research has focused on carbon-based catalysts, as they are nonprecious and environmentally benign. Interesting advances have also been made in controlling nanostructure interfaces and in introducing new materials as catalysts in the photoelectrochemical cell. However, these catalysts have as yet unresolved issues involving kinetics and light-transmittance. In this work, we introduce high-transmittance graphene onto a planar p-Si photocathode to produce a hydrogen evolution reaction to dramatically enhance photon-to-current efficiency. Interestingly, double-layer graphene/Si exhibits noticeably improved photon-to-current efficiency and modifies the band structure of the graphene/Si photocathode. On the basis of in-depth electrochemical and electrical analyses, the band structure of graphene/Si was shown to result in a much lower work function than Si, accelerating the electron-to-hydrogen production potential. Specifically, plasma-treated double-layer graphene exhibited the best performance and the lowest work function. We electrochemically analyzed the mechanism at work in the graphene-assisted photoelectrode. Atomistic calculations based on the density functional theory were also carried out to more fully understand our experimental observations. We believe that investigation of the underlying mechanism in this high-performance electrode is an important contribution to efforts to develop high-efficiency metal-free carbon-based catalysts for photoelectrochemical cell hydrogen production.

Identifying peptide sequences that can control the assembly of gold nanostructures

This study is about how peptide sequences can control the assembly and growth of gold nanomaterials. Two cysteine-containing sequences, YYCYY and glutathione (GSH), have been newly identified as assembly motifs to control the resulting two-dimensional (2D) morphology. Cysteine interacts with gold ions and the gold surface to initiate nucleation and control growth. YYCYY forms a flat, 2D, gold-decorated film and GSH results in twisted, petal-like structures. By conducting a comparative study of these two sequences, the important role of peptide folding in the gold atom assembly process is investigated.

Plasmon Enhanced Fluorescence Based on Porphyrin–Peptoid Hybridized Gold Nanoparticle Platform

A porphyrin-peptoid-hybridized silica-coated gold nanoparticle is developed, which is inspired by the protein-chlorophyll ensemble found in photosynthetic antenna. In the natural antenna, chlorophylls are integrated into dense assemblies that are supported by frameworks of proteins, which ensure optimal pigment arrangement for effective light harvesting. In the subject platform, porphyrins are conjugated to the peptoid helix scaffold in a structurally well-defined alignments and subsequently immobilized on the surface of nanoparticles. This prevents intermolecular aggregation among porphyrins and allows high resolution analysis of the effect of porphyrin configuration on the optical properties of the system. Interestingly, under the influence of plasmon from the gold nanoparticle core, the fluorescence of porphyrin is enhanced up to 24-fold at the wavelength where the plasmon resonance matches the porphyrin excitation wavelength. In addition, differences in porphyrin configuration result in spectral modification of their fluorescence emissions. Particularly, the peptoid bearing two porphyrins at a distance of 6 Å shows the most significant alteration in fluorescence. The platform can facilitate extensive studies on the relationship between porphyrin arrangement design and their photophysical interaction in antenna complexes.