Jun-ichi Kikuchi

Photoelectrochemical sensor with porphyrin-deposited electrodes for determination of nucleotides in water.

A 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP)-deposited ITO electrode as a sensor of nucleotides using photocurrent change was prepared. The TPyP-deposited ITO electrode could repeatedly detect nucleotides having concentrations of the microM order by a decrease in the photocurrent.

Solubilisation of [60]fullerenes using block copolymers and evaluation of their photodynamic activities

Unmodified [60]fullerenes (C60) were solubilised with high stability using various type of poly(ethylene glycol) (PEG) based block copolymer micelles. Block copolymer micelle-incorporated C60 fullerenes were studied in cultures for biological activities using human cervical cancer HeLa cells. As a result, the cationic block copolymer micelles delivered C60 into the cells depending on their surface densities and showed cytotoxicity under photoirradiation.

Preparation and surface modification of novel vesicular nano-particle Cerasome with liposomal bilayer and silicate surface

A novel class of nano-hybrid materials, “Cerasome,” bearing a liposomal bilayer structure and a ceramic surface, has been developed by a sol-gel reaction of a double-chain proamphiphile having an trialkoxysilane in the head moiety and followed self-assembling. In the present work, we developed new methods for preparation of the Cerasomes forming under various pH conditions and their surface modification by employing appropriate alkoxysilane compounds. When the proamphiphilic alkoxysilane was hydrolyzed in an acidic ethanol and then injected into an aqueous media at various pH, the morphologically stable Cerasomes were obtained in a wide pH range. On the other hand, an acid treatment of the proamphiphile in ethanol in the presence of tetraethoxysilane gave the Cerasome with highly developed siloxane networks on its vesicular surface. Surface modification of the Cerasome with amino groups was readily achieved in the similar manner by replacing tetraethoxysilane to 3-aminopropyltriethoxysilane. The Cerasomes thus prepared were characterized by means of dynamic light scattering and zeta potential measurements.

Cerasome as an infusible and cell-friendly gene carrier: synthesis of cerasome-forming lipids and transfection using cerasome.

Sonication of a pre-agitated aqueous solution of cationic lipid having a (EtO)3SiCH2CH2CH2 group on the quarternized ammonium nitrogen results in partially silica- or ceramic-coated liposome (cerasome), which can be used as an excellent transfection agent. Non-silylated reference lipid, which may represent cationic lipids that are used in conventional lipofection experiments, form a compact liposome, which undergoes DNA-induced fusion to provide transfection-irrelevant and larger (100–300 nm), more toxic particles. The surface-rigidified cerasome is infusible and the monomeric cerasome complex of DNA is of viral size (∼70 nm) and exhibits a remarkable transfection performance with a 102–103-fold higher efficiency (relative to the non-silylated reference lipid), minimized cytotoxicity and serum compatibility. The cerasome lipid is obtained by the reaction of 3-bromopropyltriethoxysilane with a tertiary amine derivative of the lipid. Preparation of an aqueous cerasome solution takes 1–2 h. The cerasome–DNA complex and the transfection takes about 3 d to complete.

Stable vesicular nanoparticle 'Cerasome' as an organic-inorganic hybrid formed with organoalkoxysilane lipids having a hydrogen-bonding unit

Abstract Cerasomes, liposomal membranes covered with ceramic surface, were prepared from double-chain organoalkoxysilane lipids with a hydrogen-bonding unit by using ethanol sol injection method. The Cerasomes thus prepared were characterized by means of various physical measurements such as scanning and transmission electron microscopy, light scattering and differential scanning calorimetry. As compared with liposomes formed with a lipid having a quaternary ammonium head in place of the inorganic moiety, the Cerasomes were more stable to maintain their vesicular structures even in the presence of excessive amounts of a surfactant, in which the conventional liposomes were completely dissolved. Potential of the Cerasome as an organic–inorganic hybrid material for nano-device fabrications were discussed.

Host–guest complexation effect of 2,3,6-tri-O-methyl-β-cyclodextrin on a C60–porphyrin light-to-photocurrent conversion system

Abstract In a light-to-photocurrent conversion system based on a C60–porphyrin bilayer prepared by electrostatic alternate adsorption, porphyrin units in a porphyrin polymer have been isolated by cyclodextrin utilizing the host–guest interaction. In this system, a high quantum yield was achieved by suppression of self-quenching of porphyrin units.

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 Highly Photosensitizing Liposomes with Fullerene-Doped Lipid Bilayer Using Dispersion-Controllable Molecular Exchange Reactions

Fullerene-containing liposomes with high photosensitization ability were prepared. Disaggregated fullerenes were efficiently injected into the bilayer of liposomes by a phototriggered molecular exchange reaction. These liposomes showed far higher photoreactivity than liposomes thermally produced by heating and microwave irradiation. This result indicates that control of self-aggregation of fullerene leads to a high quantum yield for the photoreaction because of the suppression of self-quenching of photoexcited fullerenes.

Purification and Properties of a Low-Molecular-Weight Phytase from Cladosporium sp. FP-1

A fungus producing high levels of phytase was isolated from air and identified as Cladosporium sp. The phytase production was stimulated by phytate in the medium used. The maximum production of phytase (108 U/ml) occurred in a medium containing 1.0 g of phytate per 100 ml. The phytase was purified to electrophoretic homogeneity by ion-exchange chromatography and gel filtration. Based on SDS-PAGE analysis, the molecular weight of the purified phytase was calculated to be approximately 32.6 kDa, and the narrow protein band indicated that this phytase is not glycosylated. The phytase has an optimum pH of 3.5, and an optimum temperature of 40 degrees C. The phytase activity was stimulated by 2-mercaptoethanol and dithiothreitol, and inhibited by Ba2+, Pb2+, iodoacetate, p-chloromercuribenzoate and phenylmethylsulfonyl fluoride. The phytase displayed high affinity for phytate and the Km was 15.2+/-3.1 microM. NMR analyses (1D and 2D) indicated that the end hydrolysis product of phytate was myo-inositol 1,2,5-triphosphate.

Efficient fluorescence resonance energy transfer in highly stable liposomal nanohybrid cerasome

Highly stable and freestanding nanohybrid cerasome with non-covalently linked two J-aggregates of cyanine dyes was constructed as a model to advance conceptual understanding of excitation energy transfer and energy trapping in connection with photobiological processes.