Ryoko M. Uda

Morphological Changes in Vesicles and Release of an Encapsulated Compound Triggered by a Photoresponsive Malachite Green Leuconitrile Derivative

Photoinduced morphological changes in phosphatidylcholine vesicles are triggered by a Malachite Green leuconitrile derivative dissolved in the lipidic membrane, and are observed at Malachite Green derivative/lipid ratios <5 mol %. This Malachite Green derivative is a photoresponsive compound that undergoes ionization to afford a positive charge on the molecule by UV irradiation. The Malachite Green derivative exhibits amphiphilicity when ionized photochemically, whereas it behaves as a lipophilic compound under dark conditions. Cryo-transmission electron microscopy was used to determine vesicle morphology. The effects of the Malachite Green derivative on vesicles were studied by dynamic light scattering and fluorescence resonance energy transfer. Irradiation of vesicles containing the Malachite Green derivative induces nonspherical vesicle morphology, fusion of vesicles, and membrane solubilization, depending on conditions. Furthermore, irradiation of the Malachite Green derivative induces the release of a vesicle-encapsulated compound.

Water‐Processable, Air‐Stable Organic Nanoparticle–Carbon Nanotube Nanocomposites Exhibiting n‐Type Thermoelectric Properties

Water-dispersed organic base nanoparticles are utilized for the highly stable n-type doping of single-walled carbon nanotubes in aqueous dispersion. Long-term stability is often a critical challenge in the application of n-type organic conductors. The present n-type organic materials exhibit almost no degradation in the thermoelectric properties over months, in air.

Photoinduced micelle-to-vesicle transition and encapsulation of glucose by photoresponsive Malachite Green leuconitrile derivative

UV irradiation on a Malachite Green leuconitrile derivative afforded a cationic surfactant in aqueous solutions of sodium bis(2-ethylhexyl) sulfosuccinate. The result involved a micelle-to-vesicle transition and encapsulation which have been investigated by trapping experiment. Transmission electron microscopy was applied for direct observation of vesicle formation. The micellar solution was studied under dark conditions with pyrene emission spectra.

Specific behavior of crowned crystal violet in cation complexation and photochromism

Abstract Absorption-spectral changes of a Crystal Violet derivative carrying a tris(monoaza-15-crown-5) structure in the presence of alkali metal ions were investigated under dark and UV-irradiated conditions. The absorption, 1 H NMR, and mass spectra indicate a dramatic conformational change of triscrowned Crystal Violet on its cesium–ion complexation under dark condition. In-situ photoirradiation measurement shows that the complexation decelerates the photochemical reaction of the triscrowned Crystal Violet.

Disruption of reverse micelles and release of trapped ribonuclease A photochemically induced by Malachite Green leuconitrile derivative

Photoinduced disruption of a sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelle is triggered by a Malachite Green leuconitrile derivative (MGL). UV irradiation of MGL solubilized in an AOT-water-chloroform mixture creates a cationic surfactant that interacts electrostatically with the anionic AOT. We investigated the disruption of the reverse micelle by using proton nuclear magnetic resonance spectroscopy and found that UV irradiation of MGL decreases the number of water molecules solubilized in the interior of the AOT reverse micelles. Furthermore, the photoinduced disruption of the reverse micelle is shown to release ribonuclease A, which is trapped in the water in the interior of the AOT reverse micelle. This photoinduced release may offer a desirable transport system of biopolymers.

Photo-triggered release from liposomes without membrane solubilization, based on binding to poly(vinyl alcohol) carrying a malachite green moiety

When working with liposomes analogous to cell membranes, it is important to develop substrates that can regulate interactions with the liposome surface in response to light. We achieved a photo-triggered release from liposomes by using a copolymer of poly(vinyl alcohol) carrying a malachite green moiety (PVAMG). Although PVAMG is a neutral polymer under dark conditions, it is photoionized upon exposure to UV light, resulting in the formation of a cationic site for binding to liposomes with a negatively charged surface. Under UV irradiation, PVAMG showed effective interaction with liposomes, releasing the encapsulated compound; however, this release was negligible under dark conditions. The poly(vinyl alcohol) moiety of PVAMG played an important role in the photo-triggered release. This release was caused by membrane destabilization without lipid solubilization. We also investigated different aspects of liposome/PVAMG interactions, including PVAMG-induced fusion between the liposomes and the change in the liposome morphologies.

Efficient photochemical switching of metal-ion complexation by malachite green leuconitrile derivatives carrying bis(crown ether)

Abstract A Malachite Green derivative incorporating a bis(monoazacrown ether) structure enables efficient photocontrol of metal ion complexation. Its photochromism in the presence of alkali metal ions is examined by kinetics measurements and molecular-orbital (MO) calculation.

Irradiation-induced fusion between giant vesicles and photoresponsive large unilamellar vesicles containing malachite green derivative

Light-initiated fusion between vesicles has attracted much attention in the research community. In particular, fusion between photoresponsive and non-photoresponsive vesicles has been of much interest in the development of systems for the delivery of therapeutic agents to cells. We have performed fusion between giant vesicles (GVs) and photoresponsive smaller vesicles containing malachite green (MG) derivative, which undergoes ionization to afford a positive charge on the molecule by irradiation. The fusion proceeds as the concentration of GV lipid increases toward equimolarity with the lipid of the smaller vesicle. It is also dependent on the molar percentage of photoionized MG in the lipid of the smaller vesicle. On the other hand, the fusion is hardly affected by the anionic component of the GV. The photoinduced fusion was characterized by two methods, involving the mixing of lipid membranes and of aqueous contents. Fluorescence microscopy revealed that irradiation triggered the fusion of a single GV with the smaller vesicles containing MG.

Photochemically triggered reaction of glucose oxidase in a fused vesicle containing Malachite Green leuconitrile derivative.

Glucose oxidase (GOD) was encapsulated in vesicles containing a photoionizable Malachite Green leuconitrile derivative (MGL). Subsequent UV irradiation of MGL afforded the fusion of GOD- and glucose-encapsulating vesicles and thus decreased the concentration of glucose in the vesicles. The time dependence of the vesicle fusion was studied using fluorescent probe molecules. This phototriggered fusion could be instrumental in the development of a system for the production of nanometer-sized bioreactors.

Photoinduced Potential Change by Crowned Triphenylmethane Dye Derivatives in Poly(vinyl chloride)-Based Liquid Membranes

ABSTRACT Photoirradiation effect on potential response to sodium ion concentrations and photoinduced potential change were investigated with plasticized poly(vinyl chloride) membranes based on triphenylmethane dye derivatives carrying a bis(monoaza-15-crown-5) moiety and a tris(monoaza-15-crown-5) moiety. A drastic photoinduced switching in potential response to sodium ion concentrations was realized by membranes containing crowned triphenylmethane dye derivatives. The photoinduced potential change was affected by complexing species such as a multinuclear complex.