In thin films of rod–shaped molecules such as pentacene, in addition to the single crystal structure, crystalline phases unique to thin films, the so–called thin–film phases, are formed. These crystalline polymorphs can be easily identified using X–ray diffraction techniques. Nevertheless, the crystalline polymorphs of dinaphthothienothiophene (DNTT), which is classified as a rod–shaped molecule, has not been reported. Previous studies have concluded that the thin film structure of DNTT is identical to that of single crystals. In this study, high–resolution X–ray diffraction measurements are performed for more precise analysis. The results reveal for the first time the existence of the thin–film phase of DNTT. Thus, this study significantly revises the conventional schematic of DNTT thin film growth.
My research career started with the high–pressure phase behavior of the DPPC bilayer, and I have clarified the effects of hydrocarbon chain–length, asymmetry, and mode of linkage between the glycerol backbone and each of the two hydrocarbon chains. The study has now been extended to cover the phase behavior of acidic phospholipids, non–natural lipids, and cationic double–chain surfactants. Through my research to date, I would like to emphasize that high pressure is the torch for exploring macroscopic lipid–bilayer research.
Lipid nanoparticles, which have been actively studied in recent years under the influence of the COVID–19 vaccine, are diverse in their structure and properties. Due to the complexity of their structure, their physicochemical properties are still difficult to elucidate. One possible solution is to extend the analytical methods that have been used for lipid membrane systems. We have developed a method for fluorescence analysis of lipid membranes with the aim of applying it to a wider range of targets, including a variety of lipid nanoparticles. Here, the methodology is presented along with examples of the evaluation of lipid nanoparticles using multiple analytical tools based on our knowledge of membrane analysis.
Nanoparticle has attracted much attention for diagnostic applications. However, delivery of nanoparticles into targeted sites is often prevent by membrane barriers in living environment, which hampers their translation into clinical practice. Recent studies have revealed that physicochemical property of nanoparticles, including size, shape, and surface chemistry, significantly affect their interaction with biological environment. Therefore, optimization of the physicochemical property is expected to improve their delivery efficiency to targeted sites. In this review, we introduce our research on the precise control of the physicochemical property of photo–functional nanoparticles and its subsequent optimization for overcoming membrane barriers in living environment. Use of mathematical model has been proposed as a promising tool to achieve this aim.
Extracellular vesicles (EVs) are biogenic lipidic nanoparticles with a diameter of 30 ～ 200 nm that are secreted from almost all cells including bacterial cells. They have attracted an attention as important targets in not only biological but also medical science fields because they contain biomarkers and signaling molecules involved in diverse human diseases and bacterial pathogenesis. We have used curvature–sensing peptides to develop a simple and rapid method for in–situ vesicle detection in cultured media without EV–purification steps. The curvature–sensing peptides are now used as novel tools for marker–independent EV detection techniques. Currently, we investigated structural factors governing binding of curvature–sensing peptides to bacterial EVs covered with hydrophilic polysaccharide chains. The structurally flexible peptides, which underwent dynamic conformational changes from the random coil to α– helix, could bind to vesicles with similar binding affinities regardless of the membrane surface covered with hydrophilic polysaccharide chains or not. In contrast, structurally restricted peptides, which had less structural conversion, showed different binding affinities for vesicles depending on their surface condition. This is probably because curvature–sensing peptides must pass through the layer of hydrophilic polysaccharide chains prior to binding to the hydrophobic membrane surface. Therefore, we concluded that the structural flexibility of curvature–sensing peptides is a key factor for governing the highly sensitive detection of bacterial EVs.
Polydiacetylene (PDA) is synthesized from the self–assembly of polymerizable lipids (e.g., 10,12–pentacosadiynoic acid (PCDA)). Since the structure of PDA vesicle is regarded as lipid bilayer, the colorimetric response of PDA could be understood as the disruption of bilayer membrane. To utilize PDA as stimuli–responsive membrane, a design strategy of PDA–incorporated nanocomposite is herein reviewed.
Steam is popular heat medium used in industry. Here, steam recovery via vapor permeation (VP) technology was reviewed from water and heat utilization point of view. Initially, VP is compared with other steam recovery technologies, including heat exchanger, desiccant, membrane condenser and transport membrane condenser. Subsequently, VP membrane materials for steam/gas separation at temperature exceeding 150 ℃ are summarized. The review concludes with an introduction of potential applications of VP steam recovery.
This time, the development of membrane formation and membrane application processes will be discussed. During the biotechnology boom of the 1980s, we developed processes that combined enzyme reactions and membranes, and ethanol fermentation and membranes. Ethanol selective permeation membrane is necessary for ethanol fermentation membrane reactor, and membrane distillation method, 1–(Trimethylsilyl)–1–propyne (PTMSP) membrane and silicalite membrane were investigated. In particular, excellent results were obtained with the silicalite membrane. In the 1980s, when the integrated circuit industry was activated and a large amount of trihalomethanes were used, environmental pollution became a problem. Therefore, we developed a separation membrane for trihalomethanes. The developed membrane is a membrane in which a polymer that selectively permeates trihalomethanes is grafted in the pores of a porous support membrane. It was named plasma filling polymerized membrane and a membrane with a new concept. This method later led to a series of membranes that became gate membranes by changing the graft polymer to temperature–responsive polymer of N–Isopropylacrylamide (NIPAM), molecular recognition crown ether–introduced polymer, ethanol recognition polymer, and so on. Furthermore, we introduced this technique to porous microcapsules and developed environment–responsive microcapsules. In principle, particle classification is possible with microfiltration membranes, but in practice even particles smaller than the membrane pores do not permeate the membrane. This is thought to be due to the formation of a particle cake layer, but it was technically difficult to prevent the formation of the cake layer. We took on this challenge and enabled particle classification while preventing cake layer formation. The operating conditions that prevent cake layer formation were also quantified. The final research topic is the development of anti–fouling membranes. Based on research in the biomaterials field, anti–fouling polymers, such as betaine–based polycarboxymethyl betaine (PCMB) and polymethoxyethyl acrylate (PMEA) are used. Membranes were prepared by dynamic membrane method, plasma graft polymerization method, Atom Transfer Radical Polymerization (ATRP) method and Nonsolvent Induced Phase Separation (NIPS) method. The membrane with anti-fouling performance could be created. We also calculated the membrane permeation behavior by molecular dynamics.
Emissions of greenhouse gases, including carbon dioxide, contribute to the climate crisis. Therefore, it is necessary to reduce carbon dioxide emissions and develop utilization technology. The conversion of carbon dioxide into microalgae is one of the utilization technologies and attracts attention. However, the conventional method of supplying carbon dioxide to microalgae culture has a problem of low supply efficiency. We tried development of carbon dioxide supply technology for microalgae culture using gas permeation membrane.