Biomedical subjects

Masaya Ishida

Publications and source records attributed to Masaya Ishida.

3 recordsLinked to original sources

PubMed2006

Soft-UV photolithography using self-assembled monolayers.

We report thiol-on-gold self-assembled monolayers (SAMs) that can be photodeprotected using soft UV irradiation (lambda = 365 nm) to yield CO(2)H functionalized surfaces complementing those reported previously, which yielded NH(2) functionalized surfaces. The photolysis of these SAMs were monitored using a combination of surface sensitive techniques. In the SAM environment the photodeprotection yields are lower than those obtained for equivalent reactions in dilute solution. The protected carboxylic acids SAMs are shown to have a low yield approximately 50% due to competing photoreduction reactions of the nitro group. The results from infrared studies show that, as the photolysis progresses, the long chain protected residues reorganize and shield the functional COOH groups, thereby reducing the hydrophilic character of the surface.

Journal Article↗

PubMed2006

Polymorphic transformation of indomethacin under high pressures.

To study the effect of pressure on polymorphic transformation, intact powder, and ethanol slurry of alpha, gamma, and amorphous forms of indomethacin (IMC) were compressed under high pressures. A quantifying method for the percentages of these three constituents in sample powder was established. Using this method, analysis of compressed samples revealed that alpha form, which is difficult to prepare in stable form under atmospheric pressure, was easily obtained in stable form from the ethanol slurry of the amorphous IMC, which does not include any specific crystalline forms. In the ethanol slurry of gamma form, transformation to alpha form was observed: a reciprocal phenomenon under atmospheric pressure. These results can be rationally explained as follows: alpha form is more easily crystallized than gamma form in the ethanol solution, the more closely-packed crystal structure of alpha form is thermodynamically predominant over gamma form under high pressure, and pressure-induced amorphization occurs. This study indicates that crystallization experiments from the slurry of amorphous samples under various pressures can be useful in screening polymorphic or other solid states.

Calorimetry, Differential Scanning↗

PubMed2005

A mild photoactivated hydrophilic/hydrophobic switch.

Surface modification using light is one of the most powerful methods for controlling the physical and chemical properties offunctionalized surfaces. In this paper, we report on systems where soft UV irradiation (lambda = 365 nm) converts a "low" activity fluorocarbon to a "high" activity amine-functionalized surface. An amine-functionalized SAM (self-assembled monolayer) is first masked using a tertiary amine catalyzed reaction with an N-hydroxysuccinimidyl carbonyl reagent. This mild, room-temperature reaction introduces a hydrophobic photocleavable nitrobenzyl "protecting group" terminated with a fluorocarbon end-chain. UV irradiation (lambda = 365 nm) of this hydrophobic/fluorocarbon surface cleaves the nitrobenzyl residue, returning the surface to the original hydrophilic/amine-functionalized state. This provides a mild, generic method of producing surfaces with hydrophilic/hydrophobic patterns or patterned with amine functional residues. Two different protecting groups, one terminated with a single and the other with three fluorocarbon end chains, are compared. In the case of the more bulky protecting group, only a small proportion of the amine residues react, but the surface is equally hydrophobic and the amine residues equally well shielded from further reaction. Surfaces are characterized by X-ray photoelectron spectroscopy, ellipsometry, surface potential, and contact angle measurements. Images of the photopatterned SAMs were obtained using scanning electron microscopy.

Journal Article↗