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Hierarchical plasmonic nanostructures that embed multiple shape-discrete domains and thereby unique plasmon resonance have implications in detection, diagnostics, and photovoltaics. Despite great progress in self-assembly of gold nanostructures, direct synthesis of hierarchical Au nanostructures that afford dense and steady intrinsic hotspots has remained less explored. This is partially because nanocrystal growth principally yields symmetrical nanocrystals with simple morphologies in monometallic systems. We report on the seeded synthesis of “Au nanograsses” on Au nanoplates that comprise an array of bent Au nanowire and exhibit total light absorption and intrinsically coupled plasmon resonance. The growth of Au nanograsses is achieved through competition between Au deposition and surface ligand passivation, which restricts the deposition of upcoming Au atoms onto the freshly deposited Au surfaces that have not been passivated. By controlling reaction kinetics and ligand passivation, the secondary nanostructures can be tuned from nanowires to nanotubes and near-spherical islands. Theoretical simulations indicate a stronger near-field electromagnetic field and a denser distribution of built-in hotspots of the Au nanograss than the near-spherical nanoisland array. Application of the Au nanograss in single-particle surface-enhanced Raman scattering (SERS) reveals a greatly elevated enhancement effect of the Au nanograss compared to the nanoisland array by nearly one order-of-magnitude.

Active plasmonic tuning is an attractive but challenging research subject, leading to various promising applications. As one of the approaches, nanostructures are placed in or on soft matter, such as elastomers and gels, and their gap distances are tuned by the mechanical extension or volume change of the supporting matrices. As hydrogels possess various types of stimuli- responsiveness with large volume change and biocompatibility, they are good candidates as supporting materials for active nanostructure tuning. However, it remains unclear how accurately we can control their nanogap distance changes using polymer gels with a low deviation due to major difficulties in the precise observation of nanostructures on the gels. Here, we prepared gold arrays with sub- 100 nm dots on silicon substrates by electron beam lithography and transferred them onto the hydrogel surface. Then, their nanopattern was actively tuned by the changes in gel size in water and their structural changes were confirmed by optical microscopy, microspectroscopy, and atomic force microscopy ( AFM). Further, we successfully prepared ionic liquid ( IL) gels with various degrees of swelling via solvent exchange. Scanning electron microscopy ( SEM) observation of the IL gels provided clear pictures at nanoscale resolution. Finally, we calculated the plasmonic spectra using a finite difference time domain ( FDTD) simulation based on the SEM images and compared them with the measured spectra. The results in this study totally support the notion that active changes in plasmonic nanodot patterns via volume changes in the hydrogel are quite homogenous on a several nanometer scale, making them ideal for precise active surface plasmon tuning.

We communicate an unconventional synthesis of Au nanoplates with high yield and excellent reproducibility through polyvinylpyrrolidone (PVP)-assisted H2O2 reduction. Unlike the ones prepared using halide-based surfactants, the PVP-capped Au nanoplates are found to afford fairly easy bio-functionalization, suggesting a vastly expanded spectrum of applications in bio-related fields.

The nuclear pores located on the nuclear envelope work as a selective barrier to nuclear import. The transport of large cargo molecules (larger than ∼40 kD) into the nucleus generally requires the aid of nuclear transport proteins, such as importins, which bind to nuclear localization signal (NLS) sequences in the cargo molecules and transport these molecules into the nucleus through the nuclear pore. In our previous paper, we showed that maltotriose(Glc3)-displaying quantum dots (QDs) can pass through the nuclear pore in digitonin-treated HeLa cells. The aim of this study is to clarify the mechanism of the nuclear import of maltooligosaccharide-displaying QDs (maltooligo-QDs). We prepared maltopentaose(Glc5) and maltoheptaose(Glc7)-QDs in addition to Glc3-QDs. The effect of the number of glucose units in the maltooligosaccharide on the rate of nuclear import of QDs has been explored by confocal laser scanning microscopy (CLSM). Further, we analyzed that the direct interactions of maltooligo-QDs to an internal protein in the nuclear pore (Nucleoporin62) using a surface plasmon resonance (SPR) system. We found that maltooligo-QDs with more than three glucose units (Glc3, Glc5 and Glc7-QDs) rapidly entered the cellular nucleus, and had a higher affinity to nucleoporin62 than those of PEG and Glc1-QDs. These data indicate that the interaction between nuclear pores and carbohydrates is the driving force behind the nuclear import of maltooligo-QDs.

Biomolecular motors have cooperative functions that facilitate various important cellular functions such as signaling and deformation. However, the multiple-molecular behavior is poorly understood when compared with the well-studied behavior of single molecules. Kinesin and microtubules (MTs) are a combination of motor and rail proteins that have been reported to show cooperativity in moving patterns. Here, we report that cross-linking of isotropic MTs enhances the movement of the local network temporally, which can elicit the effective conveyance of 5 μm diameter silica microbeads. The average velocity of the beads reached 143 nm s−1 for over 15 min, which is 2.7 times higher than the beads on kinesin-driven MTs without cross-links. Although the velocity of the beads fluctuated over the time course, the maximum velocity calculated from 5 s displacement reached 1.2 μm s−1, which was ca. 3-fold higher than the intrinsic driving velocity of kinesins, i.e., the sliding velocity of the MTs without cross-links. This technique provides such an enhanced movement by simply cross-linking the isotropic MTs, but without specific control or alignment over network polarity. The enhancement in the local motion of the MTs is discussed in terms of the “mechanochemical” effect coupled between dynamically stored elastic energies in the MT network and the collective motion of MTs driven by an ATP-fueled kinesin motor.

A DNA–lipid complex is readily prepared by mixing aqueous solutions of anionic DNA and cationic dialkyl amphiphiles, which thus forms a double helical structure and exhibits intercalation of dyes in chloroform solution.

Silver halide (AgX, X = Cl, Br, I)-based materials represent an emerging class of heterogeneous photocatalysts. Despite progress in the synthesis of carrier-separated AgX-based photocatalysts, a number of issues remain unaddressed, including complicated synthesis, unfavorably large size and therefore poor photocatalytic performance of the resultant structures. Here we show the one-step DNA-programmable synthesis of Ag/AgCl nanostructures that takes only approximately 1 min for photocatalytic application. The optimal DNA-encapsulated structures show DNA sequence-specific sizes down to less than 40 nm with a Ag/AgCl composition ratio of 2 : 1, affording a vastly increased surface area and higher photocatalytic activity than any Ag/AgX nanostructures reported previously by over two orders of magnitude. From a physical standpoint, importantly, the plasmonic nanostructured silver in Ag/AgCl accelerates the photocatalytic reaction in terms of fast electron injection to AgCl, leading to enhanced hole-electron separation and high-performance photocatalysis under visible light. To test the effect of DNA encapsulation on the Ag/AgCl nanostructures, both positively and negatively charged organic compounds serve as the model pollutants to assess their photocatalytic selectivity. Our results show that the photodecomposition of the positively charged compounds obeys a first-order rate law, whereas the negatively charged compound is decomposed with zero-order kinetics. This comparison offers a mechanistic insight into reaction kinetics on the DNA-encapsulated photocatalyst. We further find that the DNA-encapsulated Ag/AgCl photocatalysts are robust and can be recycled. To extend the applicability of the Ag/AgCl nanostructures, their use in the efficient photocatalytic inactivation of cancer cells is also demonstrated for the first time, opening up a new avenue to daylight-based theranostics.

The efficient delivery of hydrophobic drugs into target cells without the use of organic solvents or chemical linkage to delivery carriers is an important theme in the biomedical and pharmaceutical field. In this study, we synthesized virus-like particles (VLPs) coupled with cyclodextrins (CDs) as hydrophobic pockets through disulfide bonds inside the VLPs, where hydrophobic drugs can be incorporated. We report here the intracellular delivery of hydrophobic dyes or drugs encapsulated in VLPs through CDs with high efficiency and their subsequent release in cells in response to glutathione. As a model anticancer drug, paclitaxel (PTX)-CD complexes were encapsulated inside VLPs and the cytotoxic drug activity of PTX loaded VLPs against NIH3T3 cells was evaluated by CCK-8 assay. PTX-loaded VLPs exhibited a dose-dependent cytotoxic effect with a 20-fold smaller IC(50) than that of free PTX dissolved in DMSO. These results indicate that VLPs with removable CDs afford highly promising carriers of hydrophobic drugs without chemical modification of drugs.

The rapid development of DNA nanotechnology over the past decade has enabled the self-assembly of conducting building blocks towards the construction of conductive nanowires with potential applications in electronic nanodevices. To date, however, construction of nanostructures with novel electrical properties via DNA templating remains poorly explored. Here, we show that DNA can be used as a guiding template for the fabrication of polyaniline nanowires and gold nanoparticle (AuNP)–polyaniline-alternated hybrid nanowires, both of which exhibit novel electrical properties as characterized by point-contact current imaging atomic force microscopy (PCI-AFM). Specifically, the DNA-templated polyaniline nanowires exhibit Schottky emission-dominated conduction as well as a rectification effect, while the current–voltage (I–V) behaviours of the DNA-templated AuNP–polyaniline hybrid nanowires were found to be attributable to Coulomb blockade effects, probably due to the fact that the configuration of the hybrid nanowires resembles that of a one-dimensional array of multiple tunnel junctions. Given the facile and low-cost self-assembly technique, the present work is of fundamental and technological importance to the fabrication of one-dimensional nanodevices capable of novel charge transport.

We demonstrate a facile approach for converting AgCl to functional silver nanoparticles (AgNPs) via photoreduction in the presence of DNA. The resulting AgNPs are biofunctionalized, and exhibit photostable luminescence and DNA-specific Raman signatures, showing high potential for use in DNA-directed recognition and advanced bioimaging.

In our previous paper, secondary-amine appended cationic polymer 1 was used as a scaffold to display artificial receptors on a cell surface (R. Kamitani et al., ChemBioChem, 2009, 10, 230). This polymer can be retained on the cell surface for more than 30 min before being slowly internalized into the cells. In this study, our aim is to achieve the efficient internalization of quantum dots (QDs) into target cells via artificial receptors on the polymer. As a receptor molecule, N-acetylglucosamine (GlcNAc) moieties were introduced into the polymer, and GlcNAc binding protein-displaying QDs were used as a ligand. We found that ligand-presenting QDs could be internalized effectively into cells via polymer-mediated endocytosis, whereas QDs were not internalized into untreated cells. These data suggest that our method based on cell-surface engineering using polymers affords a new approach to the delivery of various poorly permeable nanoparticles into cells.

We demonstrate here a creation of a novel biomimetic bi-functional surface by using dry etching of silicon with a self-organized porous polymer. The novel silicon structures with hierarchical nanospike-array structures covered with fluorocarbons were fabricated by dry etching of silicon through the porous polymer masks. The anti-reflection and superhydrophobic properties were realized due to their large surface areas and low surface energies. These masks and silicon substrates offer great advantages and are suitable for various practical applications, including high efficiency solar cells.

Hexagonally packed water droplets condensed on a polymer solution are potential templates for the formation of honeycomb-patterned porous polymer films. A small number of surface-active molecules is indispensable for the stabilization of water droplets during solvent evaporation. Biocompatible surfactants; e.g., phospholipids, are required for the fabrication of biodegradable honeycomb-patterned polymer films, which can be used as novel biomedical materials, mainly in vivo. Among various kinds of phospholipids, dioleoylphosphatidylethanolamine (DOPE) has been reported to be the most suitable surfactant for the formation of honeycomb-patterned PLA films. Interfacial tension between a water droplet and the polymer solution is largely dependent on the chemical structure of the phospholipids. DOPE shows high interfacial tension, resulting in the stabilization of water droplets during solvent evaporation. Dierucoylphosphatidylcholine (DEPC) and dierucoylphosphatidylethanolamine (DEPE), both of which display high interfacial tension, were also found to be suitable biocompatible surfactants.

Platinum metal was sequence-specifically deposited on the DNA block copolymer synthesized by the Klenow fragment of E. coli DNA polymerase I (3'-5' exonuclease deficient).

Thermolysin (TLN) was covalently immobilized onto a large, ultrathin nylon capsule membrane grafted with poly-[p-(aminomethyl)styrene] using glutaraldehyde. When the TLN-immobilized capsule containing a buffer solution (pH 7) in the inner aqueous phase was immersed in a chloroform solution of N-benzyloxycarbonyl-L-aspartic acid (Z-L-Asp) and L-phenylalanine methyl ester (L-PheOMe) with shaking at 40 °C, the dipeptide (Z-L-Asp-L-PheOMe) was produced efficiently in the outer chloroform solution. From the Lineweaver–Burk plot, condensation in the aqueous–organic solvent involves initial binding of Z-L-Asp to the enzyme to form the Z-L-Asp–enzyme complex and then attack by L-PheOMe on the complex as the rate-determining step to form the peptide linkage. The TLN–capsule system can be used repeatedly without denaturation of protein structures by organic solvents because the enzyme on the capsule membrane is protected by buffer solutions coming from the inside. The enzyme-immobilized capsule membrane is a new bioreactor in aqueous–organic heterophases.

Lipid-coated enzyme (lipase) was prepared by mixing aqueous solutions of enzyme and synthetic dialkyl amphiphiles; it was insoluble in water but soluble in most organic solvents and showed a high activity for the synthesis of di- and tri-glycerides from monoglycerides and aliphatic acids in non-aqueous and homogeneous organic solvents.