Photoswitchable Conjugated Oligoelectrolytes for a Light-Induced Change of Membrane Morphology

The synthesis of a new conjugated oligoelectrolyte (COE), namely DSAzB, is described, which contains a conjugated core bearing a diazene moiety in the center of its electronically delocalized structure. Similar to structurally related phenylenevinylene-based COEs, DSAzB readily intercalates into model and natural lipid bilayer membranes. Photoinduced isomerization transforms the linear trans COE into a bent or C-shape form. It is thereby possible to introduce DSAzB into the bilayer of a cell and disrupt its integrity by irradiation with light. This leads to controlled permeabilization of membranes, as demonstrated by the release of calcein from DMPG/DMPC vesicles and by propidium iodide influx experiments on S. epidermidis. Both experiments support that the permeabilization is selective for the light stimulus, highly efficient, and repeatable. Target-selective and photoinduced actions demonstrated by DSAzB may have broad applications in biocatalysis and related biotechnologies.

Suppression of Gold Nanoparticle Aggregation on Lipid Membranes Using Nanosized Liposomes To Increase Steric Hindrance

Suppression of nanoparticle aggregation on a plasma membrane surface may lead to better understanding of the causes of various diseases and development of new drug delivery systems. In this study, we inhibited the aggregation of gold nanoparticles on a lipid membrane in a fluidic liquid-crystalline phase by using nanosized liposomes to increase steric hindrance. Adsorption of liposomes on gold nanoparticles was confirmed by transmission electron microscopy and ultraviolet-visible absorption spectroscopy. The ability of the liposomes to suppress gold nanoparticle aggregation strongly depended on the concentration of liposomes providing steric hindrance. The fluidity or rigidity of the liposome membrane also strongly influenced the ability of the liposomes to suppress gold nanoparticle aggregation.

Photodynamic Activity of Fullerene Derivatives Solubilized in Water by Natural-Product-Based Solubilizing Agents

Water-soluble fullerenes prepared by using solubilizing agents based on natural products are promising photosensitizers for photodynamic therapy. Cyclodextrin, β-1,3-glucan, lysozyme, and liposomes can stably solubilize not only C₆₀ and C₇₀ , but also some C₆₀ derivatives in water. To improve the solubilities of fullerenes, specific methods have been developed for each solubilizing agent. Water-soluble C₆₀ and C₇₀ exhibit photoinduced cytotoxicity under near-ultraviolet irradiation, but not at wavelengths over 600 nm, which are the appropriate wavelengths for photodynamic therapy. However, dyad complexes of solubilized C₆₀ derivatives combined with light-harvesting antenna molecules improve the photoinduced cytotoxicities at wavelengths over 600 nm. Furthermore, controlling the fullerene and antenna molecule positions within the solubilizing agents affects the performance of the photosensitizer.

Incorporation of large guest molecules into liposomes via chemical reactions in lipid membranes

The incorporation of hydrophobic guest molecules into lipid membranes by the exchange of the guest molecule from a cyclodextrin (CDx) complex to a liposome is limited to guest molecules that can be included in CDxs. To solve this problem, large guest molecules were incorporated into liposomes by chemical reactions of guest molecules in lipid membranes. Stable lipid-membrane-incorporated fullerene derivatives with large substituent(s) were prepared by Diels-Alder reactions in lipid membranes.

Lipid-membrane-incorporated arylboronate esters as agents for boron neutron capture therapy

An arylboronate ester bearing a methyl group at both of its ortho positions was stably incorporated into lipid membranes at high concentrations without hydrolysis.

Formation of lipid membrane-incorporated small π-molecules bearing hydrophilic groups

Lipid membrane-incorporated π-conjugated guest molecules (LMIGs) have been classified into four categories, including stable LMIGs, the precipitation or dissolution of some of the guest molecules from the LMIGs and the formation of small aggregates.

Lipid-membrane-incorporated hydrophobic photochromic molecules prepared by the exchange method using cyclodextrins

It was found that the exchange method for the preparation of lipid-membrane-incorporated guest molecules was applicable to not only fullerenes but also other hydrophobic molecules such as azobenzene and stilbene.

Porphyrin-uptake in liposomes and living cells using an exchange method with cyclodextrin

A preparation of a lipid-membrane-incorporated tetraphenylporphyrin was achieved from the corresponding tetraphenylporphyrin·cyclodextrin complexes using an exchange method in both liposomes and cells.