PubMed Health⌕ Search

Biomedical subjects

Tokuji Miyashita

Publications and source records attributed to Tokuji Miyashita.

5 recordsLinked to original sources
PubMed2005

Fabrication of polymer Langmuir-Blodgett films containing regioregular poly(3-hexylthiophene) for application to field-effect transistor.

Semiconducting thin films consisting of regioregular poly(3-hexylthiophene) (RR-PHT) and poly(N-dodecylacrylamide) (pDDA) were constructed by the Langmuir-Blodgett (LB) technique. A mixture of RR-PHT and pDDA spread from a chloroform solution on a water surface forms a stable monolayer, which can be transferred onto solid substrates by the LB method, yielding a well-defined polymer LB film. Surface morphology studies of the LB film indicate that the RR-PHT is dispersed uniformly throughout the surface. The polymer thin film was chemically doped by contacting with FeCl3 acetonitrile solution, and a conductivity of 5.6 S/cm was achieved. Further, the LB film was utilized as the semiconducting film in the field-effect transistor (FET), and mobilities of 2.2 x 10(-4) and 4.4 x 10(-4) cm2 V(-1) s(-1) were obtained by analyzing the saturated and linear regions of the current-voltage characteristic, respectively.

Journal Article↗
PubMed2004

Molecular optical gating devices based on polymer nanosheets assemblies.

We describe here a polymer nanosheet assembly that serves as a molecular photoswitching and optical exclusive OR (EXOR) logic gate. Separate polymer nanosheets (monolayers) containing phenanthrene, anthracene, and dinitrobenzene chromophore were prepared by the Langmuir-Blodgett technique (LB films). A bilayer-couple, consisting of phenanthrene (sensitizer) monolayer and dinitrobenzene (acceptor) monolayer, and the other couple, of anthracene monolayer and dinitrobenzene monolayer, were confirmed to function as a photodiode showing current rectification on light irradiation. The two photodiodes are connected as each photocurrent direction becomes opposite. In the polymer photodiode array (LB films), anodic photocurrent was observed when the anthracene was selectively excited. On the other hand, cathodic photocurrent was observed by selective excitation of the phenanthrene. Moreover, the output photocurrent displayed a very small value when the phenanthrene and anthracene were excited simultaneously. The performance is discussed for this gate's application to an optical EXOR logic gate.

Journal Article↗
PubMed2004

Preparation of lactose-silk fibroin conjugates and their application as a scaffold for hepatocyte attachment.

We prepared glycoconjugates (Lac-CY-SF) by the homogeneous chemical modification of solubilized silk fibroin (SF) with lactose bearing the galactose residue using cyanuric chloride (CY) as a coupling spacer and examined the usefulness of their application as a scaffold for hepatocyte attachment. The covalent immobilization of lactose into SF was assessed by several criteria including 1H-NMR measurements and reactions with lectins such as Ricinus communis agglutinin (RCA(120)) and fluorescein isothiocyanate-labeled RCA(120) (FITC-RCA(120)). The 1H-NMR spectrum of Lac-CY-SF showed new broad peaks attributed to methine and methylene protons of lactose, and by the integrated intensities of the peaks the weight ratio of lactose to SF in Lac-CY-SF was determined to be 0.20. Addition of RCA(120) to Lac-CY-SF solution caused an increase in the turbidity of the Lac-CY-SF solution. Incubation of Lac-CY-SF films with FITC-RCA(120) showed that the fluorescence emitted from the whole surface of Lac-CY-SF films. Furthermore, we examined the effect of the Lac-CY-SF conjugate-coating onto polystyrene culture dishes on the attachment of rat hepatocytes and their morphology. Attachment of hepatocytes onto the 0.1% (w/v) conjugate-coated dishes showed about an 8-fold increase as compared with that on uncoated dishes, being comparable to that on collagen-coated dishes, whereas the attachment on the SF-coated dishes was lower than that on uncoated dishes. Hepatocytes cultured onto the conjugate-coated dishes for 2.5 h showed smaller round-shaped morphology compared to those on collagen-coated dishes. After 2 days of culture in medium containing 100 nM insulin and 100 nM dexamethasone, hepatocytes on the conjugate-coated dishes formed monolayer islands with a slightly dispersed morphology, while hepatocytes cultured on collagen-coated dishes were uniformly spread flat. These results indicate that the Lac-CY-SF conjugates are useful as a scaffold for hepatocyte attachment, but the morphology of hepatocytes cultured on the conjugate-coated dishes is different from that on collagen-coated dishes.

Animals↗
PubMed2002

Photocurrent amplification by an energy/electron transfer cascade in polymer Langmuir-Blodgett films.

Effective photocurrent generation by visible light irradiation on hetero-deposited polymer Langmuir-Blodgett (LB) films containing tris(bipyridine) ruthenium(II) (Ru(bpy)3(2+)) and anthracene derivatives was observed. The photocurrent amplification was found to be assisted by the photoinduced energy/electron transfer cascade, which consists of the interlayer triplet-triplet energy transfer process from photoexcited Ru(bpy)3(2+) to anthracene, and then electron transfer processes from the triplet anthracene to a viologen acceptor, from Ru(bpy)3(2+) to the oxidized anthracene and from the electrode to Ru(bpy)3(3+).

Journal Article↗