Kiyofumi Katagiri

Magnetoresponsive Smart Capsules Formed with Polyelectrolytes, Lipid Bilayers and Magnetic Nanoparticles

Magnetoresponsive smart capsules formed with polyelectrolytes, lipid bilayers and magnetic nanoparticles were fabricated by a colloid-templating technique. Melamine-formaldehyde core particles with polyelectrolyte multilayer shell were prepared by layer-by-layer assembly. Magnetite (Fe(3)O(4)) nanoparticles were selectively deposited on the capsular surface by aqueous solution deposition using Pd catalysts. Hollow capsules were obtained by the removal of the melamine formaldehyde core particles. Vibrating sample magnetometer (VSM) measurement of the capsules revealed the ferromagnetic behavior of deposited Fe(3)O(4) nanoparticles. Alternating magnetic field irradiation generates heat in the capsular dispersion. Additional lipid bilayer coating was carried out on the obtained hollow capsules. Dye molecules were loaded by exploiting the temperature-dependence of the lipid membrane permeability. An encapsulated dye was released on-demand by irradiation with an alternating magnetic field, due to a phase transition in the lipid membrane, induced by heating of the magnetic nanoparticles. The magnetically induced release is attributed to the phase transition of the lipid membrane, caused by heat of Fe(3)O(4) nanoparticles under magnetic stimuli, and not to rupture of the capsules.

Magnetoresponsive On‐Demand Release of Hybrid Liposomes Formed from Fe3O4 Nanoparticles and Thermosensitive Block Copolymers

A new approach to control the release of encapsulated materials from liposomes by using thermosensitive block copolymers and magnetic nanoparticles is reported. Hydrophobized Fe(3) O(4) nanoparticles are synthesized via the hydrothermal process, and can be incorporated into liposomal membranes by hydrophobic interactions. Thermosensitive block copolymers of (2-ethoxy)ethoxyethyl vinyl ether (EOEOVE) and octadecyl vinyl ether (ODVE) are synthesized by living cationic polymerization. The poly(EOEOVE) block acts as a temperature-sensitive moiety, and the poly(ODVE) block acts as an anchor unit. Hybrid liposomes encapsulating pyranine, a water-soluble fluorescent dye, are prepared from mixtures of phospholipids, the hydrophobized Fe(3) O(4) nanoparticles, and the copolymer. While the hybrid liposomes released negligible amounts of pyranine under static conditions, the release of pyranine is drastically enhanced by alternating magnetic field irradiation. The magnetically induced release is attributed to the transition of the thermosensitive segment of the copolymer, which is caused by the release of localized heat from the Fe(3) O(4) nanoparticles under magnetic stimuli, rather than the rupture of the capsules. The release rate of the hybrid capsules is controlled by varying the amount of Fe(3) O(4) nanoparticles embedded into the liposomes.

Photodynamic Activity of C70 Caged within Surface‐Cross‐Linked Liposomes

[70]Fullerene (C(70)) encapsulated into a surface-cross-linked liposome, a so-called cerasome, was prepared by an exchange reaction incorporating C(70)gamma-cyclodextrin complexes into lipid membranes. Fullerene exchange in a cerasome-incorporated C(70) (CIC(70)), as well as in a lipid-membrane-incorporated C(70) (LMIC(70)), was completed within 1 min with stirring at 25 degrees C. CIC(70) was more resistant to lysis than LMIC(70) towards lysing agents such as surfactants. Furthermore, the photodynamic activity of CIC(70) in HeLa cells was similar to that of LMIC(70), indicating that C(70) can act as a photosensitizing drug (PS) without release from cerasome membranes. Thus, in contrast with general drug-delivery systems (DDSs), which require the drug to be released from the interior of liposomes, carriers for PSs for use in photodynamic therapy (PDT) do not necessarily need to release the drug. These results indicate that DDSs with high morphological stability can increase the residence time in blood and achieves tumor-selective drug delivery by the enhanced permeability and retention (EPR) effect.

Preparation of hybrid hollow capsules formed with Fe3O4 and polyelectrolytes via the layer-by-layer assembly and the aqueous solution process.

Well-defined magnetic hybrid hollow capsules formed with magnetite (Fe(3)O(4)) and polyelectrolyte-multilayer films were successfully prepared through colloidal templating with layer-by-layer assembly of polyelectrolytes, followed by aqueous solution deposition of Fe(3)O(4). Pd catalyst nanoparticles played an important role in the deposition of Fe(3)O(4). Pd nanoparticles favorably adsorbed onto the polyelectrolyte layer with positively charged amino groups. Hollow capsules were obtained by the removal of the melamine-formaldehyde core particles. Although the processes were performed in aqueous solutions at temperatures less than 60 degrees C, X-ray diffraction patterns revealed that the deposited Fe(3)O(4) was highly crystallized. The hollow capsules were stably dispersed in water; however, the capsules rapidly congregated around a locally applied magnet.

Light-induced saturation change in the angle-independent structural coloration of colloidal amorphous arrays

Light-induced saturation changes in the angle-independent structural coloration of a colloidal amorphous array mainly composed of submicron-sized fine spherical silica particles including a tiny amount of titanium oxide nanoparticles were investigated using a photoelectrochemical reaction of the Ag/Ag+ system, which can exhibit a change in the brightness of the black color.

Variable on-demand release function of magnetoresponsive hybrid capsules

Magnetoresponsive hybrid capsules formed with polyelectrolytes, amphiphile bilayers and Fe(3)O(4) nanoparticles were fabricated by a colloid-templating technique. Melamine-formaldehyde (MF) core particles with polyelectrolyte multilayer shell were prepared by layer-by-layer assembly. Fe(3)O(4) nanoparticles were additionally deposited on the capsular surface. Hollow capsules were obtained by the removal of the MF core particles. Amphiphile bilayer was finally coated on the obtained hollow capsules. The deposition amount of the Fe(3)O(4) nanoparticles is variable by changing the concentration of Fe(3)O(4) dispersion using for preparation of capsules. Encapsulated dyes were released on-demand by irradiation with an alternating magnetic field, due to a phase transition in the amphiphile membrane, induced by heating of the magnetic nanoparticles. The release rate of the hybrid capsules was controllable through controlling the deposition amount of Fe(3)O(4) nanoparticles on the capsules.

An amorphous array of poly(N-isopropylacrylamide) brush-coated silica particles for thermally tunable angle-independent photonic band gap materials

We precisely prepared thermo-responsive fine core–shell particles consisting of submicron sized silica particles as cores and high-density polymer brushes of thermo-responsive poly(N-isopropylacrylamide) (PNIPA) as shells. The shells were grown by atom transfer radical polymerisation from the initiator that was modified on the surface of the cores. These core–shell particles tend to aggregate in water, even at lower temperatures than the lower critical solution temperature of linear PNIPA. Nevertheless, along with PNIPA in water, changes in the particle size are dependent on water temperature. In accordance with these properties, the amorphous array of the core–shell particles exhibits temperature-reversible changes in the position and the strength of the photonic band gap that does not depend on angle.

Magnetically Guided Protein Transduction by Hybrid Nanogel Chaperones with Iron Oxide Nanoparticles

Protein pharmaceuticals show great therapeutic promise, but effective intracellular delivery remains challenging. To address the need for efficient protein transduction systems, we used a magnetic nanogel chaperone (MC): a hybrid of a polysaccharide nanogel, a protein carrier with molecular chaperone-like properties, and iron oxide nanoparticles, enabling magnetically guided delivery. The MC complexed with model proteins, such as BSA and insulin, and was not cytotoxic. Cargo proteins were delivered to the target HeLa cell cytosol using a magnetic field to promote movement of the protein complex toward the cells. Delivery was confirmed by fluorescence microscopy and flow cytometry. Delivered β-galactosidase, inactive within the MC complex, became enzymatically active within cells to convert a prodrug. Thus, cargo proteins were released from MC complexes through exchange interactions with cytosolic proteins. The MC is a promising tool for realizing the therapeutic potential of proteins.

Robust Infrared-Shielding Coating Films Prepared Using Perhydropolysilazane and Hydrophobized Indium Tin Oxide Nanoparticles with Tuned Surface Plasmon Resonance

Robust infrared (IR)-shielding coating films were prepared by dispersing indium tin oxide (ITO) nanoparticles (NPs) in a silica matrix. Hydrophobized ITO NPs were synthesized via a liquid phase process. The surface plasmon resonance (SPR) absorption of the ITO NPs could be tuned by varying the concentration of Sn doping from 3 to 30 mol %. The shortest SPR wavelength and strongest SPR absorption were obtained for the ITO NPs doped with 10% Sn because they possessed the highest electron carrier density. Coating films composed of a continuous silica matrix homogeneously dispersed with ITO NPs were obtained using perhydropolysilazane (PHPS) as a precursor. PHPS was completely converted to silica by exposure to the vapor from aqueous ammonia at 50 °C. The prepared coating films can efficiently shield IR radiation even though they are more than 80% transparent in the visible range. The coating film with the greatest IR-shielding ability completely blocked IR light at wavelengths longer than 1400 nm. The pencil hardness of this coating film was 9H at a load of 750 g, which is sufficiently robust for applications such as automotive glass.

Molecular selective photocatalytic decomposition of alkylanilines by crystalline TiO2 particles and their nanocomposites with mesoporous silica

Molecular selective photocatalytic decomposition of alkylanilines in water was investigated by using crystalline TiO2 particles (P-25) and their nanocomposites with mesoporous silica. In the nanocomposites, pre-formed TiO2 particles were embedded into surfactant-templated mesoporous silica with tuned pore sizes (1.4–5.3 nm) as described in our previous reports (Chem. Commun. 2005, 2131–2133; J. Mater. Chem. 2011, 21, 12117–12125). Contrary to the generally accepted knowledge of TiO2 photocatalysts, pristine TiO2 particles showed molecule selective photocatalysis: decomposition of 4-n-heptylaniline (NHA) was much faster than that of 4-n-butylaniline (NBA) or p-toluidine (4-methylaniline, PT) in a mixed aqueous solution. After NHA had almost disappeared, decomposition of NBA accelerated. When the TiO2 particles were surrounded by mesoporous silica, the molecular selectivity was strongly modified: the nanocomposites showed high molecular selectivity for NBA decomposition and the reaction of PT was considerably suppressed. The origin of molecular selectivity can basically be ascribed to preferential molecular adsorption, and the difference in selectivity between alkylanilines and alkylphenols is discussed in terms of the interaction of the molecules with the nanocomposite surfaces.