Kuniharu Ijiro

Gold Nanoparticles as a Vaccine Platform: Influence of Size and Shape on Immunological Responses in Vitro and in Vivo

This paper demonstrates how the shape and size of gold nanoparticles (AuNPs) affect immunological responses in vivo and in vitro for the production of antibodies for West Nile virus (WNV). We prepared spherical (20 and 40 nm in diameter), rod (40 × 10 nm), and cubic (40 × 40 × 40 nm) AuNPs as adjuvants and coated them with WNV envelope (E) protein. We measured anti-WNVE antibodies after inoculation of these WNVE-coated AuNPs (AuNP-Es) into mice. The 40 nm spherical AuNP-Es (Sphere40-Es) induced the highest level of WNVE-specific antibodies, while rod AuNP-Es (Rod-Es) induced only 50% of that of Sphere40-E. To examine the mechanisms of the shape-dependent WNVE antibody production, we next measured the efficiency of cellular uptake of AuNP-Es into RAW264.7 macrophage cells and bone-marrow-derived dendritic cells (BMDCs) and the subsequent cytokine secretion from BMDCs. The uptake of Rod-Es into the cells proceeded more efficiently than those of Sphere-Es or cubic WNVE-coated AuNPs (Cube-Es), suggesting that antibody production was not dependent on the uptake efficiency of the different AuNP-Es. Cytokine production from BMDCs treated with the AuNP-Es revealed that only Rod-E-treated cells produced significant levels of interleukin-1β (IL-1β) and interleukin-18 (IL-18), indicating that Rod-Es activated inflammasome-dependent cytokine secretion. Meanwhile, Sphere40-Es and Cube-Es both significantly induced inflammatory cytokine production, including tumor necrosis factor-α (TNF-α), IL-6, IL-12, and granulocyte macrophage colony-stimulating factor (GM-CSF). These results suggested that AuNPs are effective vaccine adjuvants and enhance the immune response via different cytokine pathways depending on their sizes and shapes.

Mesoscopic patterns of molecular aggregates on solid substrates

Abstract A two-dimensional micron-sized honeycomb structure was formed when a chloroform solution of an amphiphilic polymer was cast on solid surfaces at high atmospheric humidity. This simple method is widely applicable for patterning of molecular aggregates on solid surfaces. Mesoscopic patterns are demonstrated to be formed spontaneously from a variety of amphiphilic polyion complexes, amphiphilic covalent polymers, and organic–inorganic hybrid materials. Size and structure of the patterns can be regulated by concentration, atmospheric humidity, etc.

Mesoscopic pattern formation of nanostructured polymer assemblies

Abstract Hierarchical mesoscopic structures of the nanoscopic supramolecular assemblies, which consist of polyelectrolytes and bilayer-forming amphiphiles, are prepared by a simple and new solvent-casting method. Submicron scale 2-D structures, e.g. regular dots, stripes, and networks, are formed when highly diluted organic solutions of polymer assemblies are cast on solid surfaces. Dynamic mesoscopic regular structures, the so-called ‘dissipative structures’, formed in the non-equilibrium processes of solvent-casting are fixed as hierarchically structured polymer assemblies.

Sub-100 nm Gold Nanoparticle Vesicles as a Drug Delivery Carrier enabling Rapid Drug Release upon Light Irradiation

Previously, we reported gold nanoparticles coated with semifluorinated ligands self-assembled into gold nanoparticle vesicles (AuNVs) with a sub-100 nm diameter in tetrahydrofuran (THF). (1) Although this size is potentially useful for in vivo use, the biomedical applications of AuNVs were limited, as the vesicular structure collapsed in water. In this paper, we demonstrate that the AuNVs can be dispersed in water by cross-linking each gold nanoparticle with thiol-terminated PEG so that the cross-linked vesicles can work as a drug delivery carrier enabling light-triggered release. Rhodamine dyes or anticancer drugs were encapsulated within the cross-linked vesicles by heating to 62.5 °C. At this temperature, the gaps between nanoparticles open, as confirmed by a blue shift in the plasmon peak and the more efficient encapsulation than that observed at room temperature. The cross-linked AuNVs released encapsulated drugs upon short-term laser irradiation (5 min, 532 nm) by again opening the nanogaps between each nanoparticle in the vesicle. On the contrary, when heating the solution to 70 °C, the release speed of encapsulated dyes was much lower (more than 2 h) than that triggered by laser irradiation, indicating that cross-linked AuNVs are highly responsive to light. The vesicles were efficiently internalized into cells compared to discrete gold nanoparticles and released anticancer drugs upon laser irradiation in cells. These results indicate that cross-linked AuNVs, sub-100 nm in size, could be a new type of light-responsive drug delivery carrier applicable to the biomedical field.

Spontaneous formation of polymer nanoparticles by good-solvent evaporation as a nonequilibrium process

In recent years, polymer nanoparticles have been investigated with great interest due to their potential applications in the fields of electronics, photonics, and biotechnology. Here, we report the spontaneous formation of polymer nanoparticles from a clear solution containing a nonvolatile poor solvent by slow evaporation of a volatile good solvent. During evaporation of the good solvent, the solution gradually turns turbid. After evaporation, polymer nanoparticles of homogeneous shape and size are dispersed in the poor solvent. Homogeneous nucleation and successive growth of polymer particles takes place during the dynamic nonequilibrium process of solvent evaporation. The size of the particles, ranging from tens of nanometers to micrometer scale, depends on both polymer concentration and the solvent mixing ratio. Because of the physical generality of the particle formation mechanism, this procedure is applicable to a wide variety of polymers with suitable combinations of solvents. Here, we also show unique features, surface structures and surface properties of polymer nanoparticles prepared by this method.

Gold Nanoparticles Coated with Semi-Fluorinated Oligo(ethylene glycol) Produce Sub-100 nm Nanoparticle Vesicles without Templates

Gold nanoparticles (NPs) with diameters of 5, 10, and 20 nm coated with semifluorinated oligo(ethylene glycol) ligands were formed into sub-100 nm hollow NP assemblies (NP vesicles) in THF without the use of a template. The NP vesicles maintained their structure even after the solvent was changed from THF to other solvents such as butanol or CH(2)Cl(2). NMR analyses indicated that the fluorinated ligands are bundled on the NPs and that the solvophobic feature of the fluorinated bundles is the driving force for NP assembly. The formed NP vesicles were surface-enhanced Raman scattering-active capsules.

Gold Nanoparticle Arrangement on Viral Particles through Carbohydrate Recognition: A Non-Cross-Linking Approach to Optical Virus Detection

We propose a new approach to optical virus detection based on the spatial assembly of gold nanoparticles on the surface of viruses. Since JC virus-like particles (VLPs) comprise a repeating viral capsid protein that binds to sialic acid, the conjugation of sialic acid-linked Au particles with VLPs enables the spatial arrangement of Au particles on the VLP surface. This structure produced a red shift in the absorption spectrum due to plasmon coupling between adjacent Au particles, leading to the construction of an optical virus detection system. Our system depends not on the simple cross-linking of VLPs and Au particles, but on an ordered Au structure covering the entire surface of the VLPs and can be applied to various virus detection systems using the inherent ligand recognition of animal viruses.

Interfacial tension governs the formation of self-organized honeycomb-patterned polymer films

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.

A DNA–lipid complex soluble in organic solvents

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.

Hydrophilic gold nanoparticles adaptable for hydrophobic solvents.

Surface ligand molecules enabling gold nanoparticles to disperse in both polar and nonpolar solvents through changes in conformation are presented. Gold nanoparticles coated with alkyl-head-capped PEG derivatives were initially well dispersed in water through exposure of the PEG residue (bent form). When chloroform was added to the aqueous solution of gold nanoparticles, the gold nanoparticles were transferred from an aqueous to a chloroform phase through exposure of the alkyl-head residue (straight form). The conformational change (bent to straight form) of immobilized ligands in response to the polarity of the solvents was supported by NMR analyses and water contact angles.