A three-dimensional packed vesicular assembly was successfully prepared by using an organic-inorganic hybrid, the Cerasome. This assembly was achieved by using an alternate layer-by-layer adsorption technique with the anionic and the cationic Cerasome derived from corresponding organoalkoxysilane amphiphiles. Adsorption quantities of each Cerasome layer were evaluated by employing a quartz crystal microbalance. The surface structure of the Cerasome paving on a substrate obtained in this way was observed by atomic force microscopy. The Cerasome particles closely packed like a stone pavement were clearly observed in both layers. In addition, the difference in the particle size for each layer indicates the cationic and anionic Cerasomes undoubtedly formed the layer-by-layer assembly. The layered paving of the vesicular nanoparticles was seen in every layer at least up to ten adsorption steps.

This paper provides an overview of our recent work in the area of bioinspired colloidal particles. We highlight how modifying the basic polyelectrolyte multilayer shell with materials such as light-absorbing gold nanoparticles, lipid bilayer membranes, and targeting ligands can functionalize colloids prepared via the layer-by-layer assembly technique. These nanoengineered colloids are expected to show promise in areas ranging from drug and gene delivery to cell membrane modeling.

A novel class of organic-inorganic hybrids, the so-called cerasomes, which have a bilayer vesicular structure and a silicate surface, has been synthesized by combination of sol-gel reaction and self-assembly of organoalkoxysilanes with a molecular structure analogous to lipids. We have synthesized two cerasome-forming organoalkoxysilanes, N-[N-(3-triethoxysilyl)propylsuccinamoyl]dihexadecylamine (1) and N,N-dihexadecyl-N (alpha)-[6-[(3-triethoxysilyl)propyldimethylammonio]hexanoyl]glycinamide bromide (2), and investigated the synthetic conditions of the cerasomes and their structural characteristics. For the proamphiphilic 1, the cerasome was obtained under restricted pH conditions where acid-catalyzed hydrolysis of the triethoxysilyl moiety proceeded without disturbing the vesicle formation. In contrast, the amphiphilic 2, additionally having a hydrophilic quaternary ammonium group, formed stable dispersions of the cerasome in a wide pH range. The hydrolysis behavior of the triethoxysilyl groups was monitored by (1)H NMR spectroscopy. Morphology of the cerasomes having the liposomal vesicular structure was confirmed by TEM observations. Extent of the development of siloxane networks through condensation among the silanol groups on the cerasome surface was evaluated by using MALDI-TOF-MS spectrometry. Formation of oligomers of the cerasome-forming lipids in the vesicle was clearly confirmed. Due to the siloxane network formation, the cerasome showed remarkably high morphological stability compared with a reference liposome, as evaluated by surfactant dissolution measurements.

It is desirable to fabricate colorful coatings that have nonfading properties and are environmentally friendly. In this study, a novel approach for creating structural color coatings from monodisperse silica particles is presented. The structural color coating films, formed from an array of silica particles with a small amount of black additive, are easily prepared by a simple electrophoretic deposition (EPD) technique. The arrangement of the particle array is controlled by varying the applied voltage and deposition time. The iridescence, that is, the angular dependence, of the structural color dramatically changes with the arrangement of the particle array. A variety of colored coatings can be produced by changing the size of the particles. Structural color coatings on materials with curved surfaces and complicated shapes are also achieved by the EPD method.

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.

An artificial lipid bearing a triethoxysilyl head and a dialkyl tail has been synthesized in order to prepare a novel type of organic-inorganic hybrid, “Cerasome”, which can form siloxane network on its vesicular surface. The Cerasomes were obtained upon vortex mixing of aqueous dispersion of the lipid followed by acid hydrolysis of the head moiety.

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.

No abstract