Biomedical subjects

Yasuhiro Shirai

Publications and source records attributed to Yasuhiro Shirai.

9 recordsLinked to original sources

PubMed2006

Characterization of self-assembled monolayers of fullerene derivatives on gold surfaces: implications for device evaluations.

The widely employed approach to self-assembly of fullerene derivatives on gold can be complicated due to multilayer formations and head-to-tail assemblies resulting from the strong fullerene-fullerene and fullerene-gold interactions. These anomalies were not examined in detail in previous studies on fullerene self-assembled monolayers (SAMs) but were clearly detected in the present work using surface characterization techniques including ellipsometry, cyclic voltammetry (CV), and X-ray photoelectron spectroscopy (XPS). This is the first time that SAMs prepared from fullerene derivatives of thiols/thiol esters/disulfides have been analyzed in detail, and the complications due to multilayer formations and head-to-tail assemblies were revealed. Specifically, we designed and synthesized several fullerene derivatives based on thiols, thiol acetates, and disulfides to address the characterization requirements, and these are described and delineated. These studies specifically address the need to properly characterize and control fullerene-thiol assemblies on gold before evaluating subsequent device performances.

Journal Article↗

PubMed2006

Recent progress on nanovehicles.

Nanovehicles are a new class of molecular machines consisting of a molecular scale chassis, axles, and wheels, that can roll across solid surfaces with structurally defined directions making them of interest to synthetic chemists, surface scientists, chemical engineers, and the general car enthusiast. In this tutorial review, following a brief introduction to the development of nanomachines, our recent progress on the nanovehicle project is presented including the design, synthesis, and testing of a series of nanocars, nanotrucks, and motorized nanocars.

Journal Article↗

PubMed2006

En route to a motorized nanocar.

[structure: see text] With the eventual goal of demonstrating a motorized nanocar, the key structure has been synthesized which bears a light-activated unidirectional molecular motor and an oligo(phenylene ethynylene) chassis and axle system with four carboranes to serve as the wheels. Kinetics studies in solution show that the motor indeed rotates upon irradiation with 365 nm light, and the fullerene-free carborane wheel system is an essential design feature for motor operation.

Journal Article↗

PubMed2006

Surface-rolling molecules.

Design, syntheses, and testing of new, fullerene-wheeled single molecular nanomachines, namely, nanocars and nanotrucks, are presented. These nanovehicles are composed of three basic components that include spherical fullerene wheels, freely rotating alkynyl axles, and a molecular chassis. The use of spherical wheels based on C60 and freely rotating axles based on alkynes permits directed nanoscale rolling of the molecular structure on gold surfaces. The rolling motion observed by STM resembles the same motion performed by macroscopic entities in which rolling occurs perpendicular to the axles. A new synthesis methodology, in situ ethynylation of fullerenes, was developed for the realization of the fullerene-wheeled molecular machines. Four generations of the fullerene-wheeled structures were developed, and the latest fourth generation nanocar, 3b, along with three-wheeled triangular compounds, 4a and 4b, provided definitive evidence for fullerene-based wheel-like rolling motion, not stick-slip or sliding translation. The studies here underscore the ability to control directionality of motion in molecular-sized nanostructures through precise molecular design and synthesis.

Journal Article↗

PubMed2005

Synthesis, spectroscopic and nonlinear optical properties of multiple [60]fullerene-oligo(p-phenylene ethynylene) hybrids.

A series of multiple [60]fullerene terminated oligo(p-phenylene ethynylene) (OPE) hybrid compounds has been synthesized through a newly developed in situ ethynylation method. Structural and magnetic shielding properties of the highly unsaturated carbon-rich C(60) and OPE scaffolds were characterized by 1D and 2D NMR spectroscopic analyses. Electronic interactions between the [60]fullerenes and the OPE backbones were investigated by UV/Vis spectroscopic and cyclic voltammetry (CV) experiments. Our studies clearly show that although the multiple [60]fullerene groups are connected via pi-conjugated OPE frameworks, they present diminutive electronic interactions in the ground state, and the electronic behavior of the [60]fullerene cages are only affected by the OPE backbones through modest inductive effects. Interestingly, sizable third-order nonlinear optical (NLO) responses (gamma) and enhanced two-photon absorption (TPA) cross-sections (sigma((2))) were determined for the multifullerene-OPE hybrid 31 relative to its OPE precursor from differential optical Kerr effect (DOKE) experiments. Such enhanced NLO performance is presumably due to the occurrence of periconjugation and/or charge transfer effects in the excited state. In addition, comparatively strong excited-state absorption was observed and characterized for OPE pentamer 12. Thus, the use of such fullerene-derivatized conjugated oligomers aids the quest for molecules with large third-order NLO and TPA properties.

Fullerenes↗

PubMed2005

Directional control in thermally driven single-molecule nanocars.

With the hope of directing future bottom-up fabrication through bulk external stimuli (such as electric fields) on nanometer-sized transporters, we sought to study controlled molecular motion on surfaces through the rational design of surface-capable molecular structures called nanocars. Here we show that the observed movement of the nanocars is a new type of fullerene-based wheel-like rolling motion, not stick-slip or sliding translation, due to evidence including directional preference in both direct and indirect manipulation and studies of related molecular structures.

Journal Article↗

PubMed2005

[A case of advanced hepatocellular carcinoma with tumor thrombus treated by transarterial chemoembolization therapy using cisplatin (CDDP) with DSM and SAP-MS].

A 78-year-old woman with advanced HCC had been treated by transarterial chemoembolization with epirubicin, however, tumor progression was not controlled and a tumor thrombus was found in the portal vein trunk. A new treatment method for transarterial chemoembolization using CDDP with DSM and SAP-MS was introduced. Marked regression of hepatic lesions and portal vein tumor thrombus was observed after two sessions. No adverse effect was found. The patient has been controlled without tumor recurrence and elevation of tumor marker for 14 months. A new treatment protocol will be useful for patients with far advanced hepatocellular carcinoma with portal vein tumor thrombus.

Aged↗

PubMed2004

Facile synthesis of multifullerene-OPE hybrids via in situ ethynylation.

[reaction: see text] A series of fullerene-terminated oligo(phenylene ethynylene)s (OPEs) (1a-d and 2) have been synthesized and further characterized by cyclic voltammetry (CV) and UV-vis spectroscopy. The key step in the syntheses is an effective one-pot reaction that allows the attachment of C(60) to multiple terminal alkynes.

Journal Article↗

PubMed2002

Solitary necrotic nodule of the liver.

Solitary necrotic nodule of the liver is a rare benign lesion; only 22 cases have been reported to date. An unsolved problem in treating these lesions involves the difficulties in differential diagnosis; specific features of necrotic nodule of the liver in preoperative examinations have not been identified. Here, we report a patient with resected solitary necrotic nodule of the liver with preoperative features shown on ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) examinations. A 48-year-old woman was referred to our hospital on December 13, 1999 because a hypoechoic lesion in Couinaud's segment VIII of the liver had been incidentally detected on US. A CT scan confirmed the presence of a round hypodense lesion, measuring 2 cm in diameter. No significant enhancement was recognized on dynamic MRI study. T1-Weighted MRI examinations demonstrated a low intensity showing a triple-layered pattern with low-iso-low intensity in the lesion, while T2-weighted images demonstrated a slightly high intensity in the lesion. These features suggested fibrous tissue. Histological examinations following partial resection of the liver revealed a solitary necrotic nodule of the liver. Combination studies, including MRI examinations, would be useful for the preoperative diagnosis of a solitary necrotic nodule of the liver.

Female↗