In biomembranes, the functional molecules such as peptides, proteins and polysaccharides are distributed heterogeneously in a sea of phospholipid bilayer and the fluidity of the lipid bilayer governs cell functions through the transport of the functional molecules. Therefore, membrane viscosity which is a measure of the fluidity has been investigated extensively, however, the landscape of the biomembrane viscosity is still unclear due to the complex structure of biomembranes and difficulties of measuring membrane viscosity. Recently, we have succeeded in developing a simple technique to measure membrane viscosity of heterogeneous liposomes from the flow pattern. When we apply a point force on the liposome by microinjection, a pair of vortices is produced on the liposome membrane and the position of the vortex center depends on the membrane viscosity. Using this method, we measured the membrane viscosity of a giant liposome composed of saturated lipid DPPC, unsaturated lipid DOPC, and cholesterol. This ternary system is well known to exhibit a heterogeneous structure due to phase separation into liquid ordered phase (Lo) and liquid disordered phase (Ld). We measured the membrane viscosity of the ternary liposome with various compositions, and found that the membrane viscosity varied more than three orders of magnitude depending on the composition. This method enables us to measure the membrane viscosity of heterogeneous membranes over a wide range. Although we need further basic fluid dynamics studies on model membrane systems, this approach has high potential to elucidate the role of the membrane fluidity in cell functions.

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Substrate supported lipid bilayers (SLBs) are highly attractive as a model of the biological membrane and as a platform for developing devices that utilize membrane functions. We have developed a patterned SLB composed of polymerized and natural (fluid) lipid bilayers. The polymeric bilayer acts as a framework to define the geometry of the fluid bilayers and enhance their stability. The patterned SLBs can be combined with a nanometric space that can reduce the background noise, enabling highly sensitive detection (e.g. single molecule tracking). Patterned SLBs in combination with a nanometric confinement provide promising platforms for biophysical studies as well as a wide range of biomedical applications.

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Polyaniline in its conductive emeraldine salt form (PANI–ES) has good dispersibility in water phase, thermal and radiation stability. The enzymatic oxidation of aniline or aniline dimer ( p–aminodiphenylamine, PADPA), in the presence of dispersed anionic soft–interfaces– also called “templates”– in slightly acidic aqueous solution is expected as environmentally–friendly process for PANI–ES production. Without templates, these products do not form. Laccase/O2–catalized synthesis of PANI–ES in the presence of sodium bis(2–ethylhexyl)sulfosuccinate (AOT) vesicles as templates is advantageous in its simple procedure, and low concentration of required enzyme. The effect of four different templates under their respective optimal conditions was investigated and compared in a systematic way. The templates used were sulfonated polystyrene (SPS), micelles from sodium dodecylbenzenesulfonate (SDBS), vesicles from SDBS/decanoic acid (DA) and vesicles from AOT. Although all four templates carry a sulfonate group and yield PANI–ES–type products, there are clear differences in the properties of the product mixtures obtained. AOT vesicles performed as the best template in the viewpoint of produced amount and chemical stability of polarons (radical cations) in PANI–ES–like products.

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Enzymes immobilized in carrier materials are useful to control chemical reactions. Phospholipid vesicles (liposomes) possess compartmentalized aqueous phase and lipid bilayer membranes in which different enzyme molecules can be confined for various biotechnological applications. In this review, characteristic features of the preparation methods of liposomes being encapsulated or chemically conjugated with the enzyme molecules are described. Then, applications of the liposomal systems are described with respect to the stabilization of thermally denatured enzymes and a catalytic cascade reaction. Current progress and perspective of relevant researches are briefly mentioned.

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Lipid vesicle (also called liposome) is a molecular aggregate consisting of closed lipid bilayers formed by mainly phospholipids in aqueous solutions. They can be utilized as carriers for drug delivery systems as well as encapsulation materials of other functional compounds. Recently a novel method for preparing lipid vesicles using water–in– oil–in–water (W/O/W) type multiple emulsions has been developed by the authors. Lipid vesicle formation in this method is achieved via two processes: multiple emulsification and solvent evaporation processes. The multiple emulsification process consists of two–step emulsification involving primary emulsification for obtaining water–in–oil emulsion followed by secondary emulsification for obtaining W/O/W multiple emulsion. In the solvent evaporation process, organic solvent is removed from the W/O/W multiple emulsions by evaporation, and then lipid vesicles are formed and dispersed in the aqueous phase. By this method, lipid vesicles with high encapsulation efficiency for hydrophilic molecules and controlled diameter can be obtained. In this review, the outline of this method for obtaining lipid vesicles is overviewed, and a possible mechanism of lipid vesicle formation and the effects of the type and concentration of water–soluble emulsifiers on encapsulation efficiency are discussed based on the authors’ studies.

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Transdermal drug delivery, in which drugs are administered through the skin, has been attracting much attention because it can bypass the first–pass effect in the liver, maintain the effective drug concentration in blood, avoid the pain and the risks of accidents in injection. Since the skin plays an important role as a barrier preventing the entry of foreign substances from the outside, a special technique is required to achieve the effective transdermal delivery of drugs. In this review, we introduce the latest transdermal drug delivery systems using emulsions. The use of emulsions enables to deliver high–molecular–weight drugs, which are usually difficult to permeate through the skin. Emulsions combined with a skin enhancer or ionic liquids are found to be useful for the effective transdermal delivery of biomolecules such as peptides or proteins.

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Membrane filtration techniques for water purification have been recently applied to lower–quality raw water and larger–scale treatment plants in Japan. In response to the need for the technological capabilities corresponding to such a wide variety of the situations, Swing group provides the three types of membrane filtration systems, that is, large– and middle– scale submerged PVDF membrane, small–scale submerged PE membrane and pressurized membrane at the moment. In this article, our membrane systems and pre– and post– treatments of those are summarized, introducing the five cases of installation.

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