α-Tocopherol: New Perspectives and Challenges for Achieving the Sustainable Development Goals (SDG) Target.

Vitamin E (VE) is a lipophilic vitamin, and Evans and Bishop demonstrated the existence of a hitherto unrecognized dietary factor essential for normal reproduction in rat. During 100 years after the discovery, α-tocopherol (α-Toc) has been the representative species in VE homologues, and both naturally occurring and synthetically prepared α-Toc have been widely used and studied. Although it is indicated by a single-word VE, research on VE involves various chemical species. It is important to understand the fine structure and accurate characteristics of individual VE species when using VE. Each VE sample has compositional and/or isomer issues, and furthermore, the usability greatly varies depending on the modified species of esterification. The VE industry involves many interdisciplinary fields. Improvements in formulation technology and confirmation of the novel biological activity of VE greatly owns its utility and opens up new applications. As the interim period between the start and end of the agenda for Sustainable Development Goals (SDGs), in this minireview, the recent trends and future guidelines of VE, especially α- Toc, in relation to the SDGs have been demonstrated.

Dramatic morphological changes in liposomes induced by peptide nanofibers reversibly polymerized and depolymerized by the photoisomerization of spiropyran.

Cytoskeletons such as microtubules and actin filaments are natural protein assemblies, which dynamically control cellular morphology by reversible polymerization/depolymerization. Recently, the control of polymerization/depolymerization of fibrous protein/peptide assemblies by external stimuli has attracted significant attention. However, as far as we know, the creation of an "artificial cytoskeleton" that reversibly controls the polymerization/depolymerization of peptide nanofiber in giant unilamellar vesicles (GUVs) has not been reported. Here, we developed peptide nanofiber self-assembled from spiropyran (SP)-modified ß-sheet-forming peptides, which can be reversibly polymerized/depolymerized by light. The reversible photoisomerization of the SP-modified peptide (FKFECSPKFE) to the merocyanine-peptide (FKFECMCKFE) by ultraviolet (UV) and visible light irradiation was confirmed by UV-visible spectroscopy. Confocal laser scanning microscopy with thioflavin T staining and transmission electron microscopy of the peptides showed that the SP-peptide formed ß-sheet nanofibers, whereas the photoisomerization to the merocyanine-peptide almost completely dissociated the nanofibers. The merocyanine peptide was encapsulated in spherical GUVs comprising of phospholipids as artificial cell models. Interestingly, the morphology of GUV encapsulating the merocyanine-peptide dramatically changed into worm-like vesicles by the photoisomerization to the SP-modified peptide, and then reversibly changed into spherical GUV by the photoisomerization to the MC-modified peptide. These dynamic morphological changes in GUVs by light can be applied as components of a molecular robot with artificially controlled cellular functions.

Aqueous Sugar-Based Amphiphile Systems: Recent Advances in Phase Behavior and Nanoarchitectonics.

Currently, numerous fascinating molecular assemblies are used in food, cosmetics, and pharmaceuticals. Sugar-based amphiphiles are representative constituents of these molecular assemblies. Despite numerous studies on these generic compounds, many aspects remain unexplored even in aqueous systems. In this review, molecular assembly studies of sugar-based amphiphiles in aqueous systems are summarized. First, recent advances in molecular assembly studies, including the glassy state of lyotropic and thermotropic liquid crystalline (LC) phases, modulated crystal phases, and coagels consisting of nanofibers of alkyl ß-D-glycosides, are presented. Second, research on thermotropic LC phases under desiccated conditions of trehalose fatty acid monoesters to clarify the fundamental behaviors of the glassy state and their use as stabilizers of glass-forming surfactants for pharmaceutical applications are discussed. Several effective X-ray analytical approaches are included to identify or clarify these phenomena, unknown or unsolved for a long time. Third, a comprehensive analysis of vitamin E (tocopherol)-cyclodextrin in aqueous systems is presented. Along with these topics, the importance of investigating stabilizer-free functional components, considered minor components, is highlighted. These unveiled phenomena or concepts will contribute to the development of nanoarchitectonics covering the self-assembly and selforganization of soft molecules.

Reversible Photocontrol of Microtubule Stability by Spiropyran-Conjugated Tau-Derived Peptides.

Spatiotemporal modulation of microtubules by light has become an important aspect of the biological and nanotechnological applications of microtubules. We previously developed a Tau-derived peptide as a binding unit to the inside of microtubules. Here, we conjugated the Tau-derived peptide to spiropyran, which is reversibly converted to merocyanine by light, as a reversible photocontrol system to stabilize microtubules. Among the synthesized peptides with spiropyran/merocyanine at different positions, several peptides were bound to the inside of microtubules and stabilized the structures of microtubules. The peptide with spiropyran at the N-terminus induced polymerization and stabilization of microtubules, whereas the same peptide with the merocyanine form did not exert these effects. Reversible formation of microtubules/tubulin aggregates was achieved using the peptide with spiropyran conjugated at the N-terminus and irradiation with UV and visible light. Spiropyran-conjugated Tau-derived peptides would be useful for spatiotemporal modulation of microtubule stability through reversible photocontrol of binding.

Stabilizer-free Vitamin E Nanovehicle for Biological Research.

In molecular biology research, a vitamin E (VE) vehicle (VE dissolved in organic solvent) is often added to water media without a stabilizer. However, the detailed behavior of VE colloids in water media is unclear. In this study, we reveal that VE nanoemulsion readily forms in water-based media through the existing protocol. The colloid size was changed from 39 nm to the submicron scale by adjusting the initial concentration of the VE solution and adding a buffer. The radical scavenging effect of the dispersed nanosized VEs is comparable to that of the water-soluble antioxidant Trolox, providing excellent antioxidant performance in colloid form. The cytoprotection effect of the VE colloids under a lipid oxidation condition largely depends on the size of the nanodispersion. Smaller dispersed particles are more efficient radical scavengers than larger particles for a constant VE amount owing to sophisticated uptake behavior of cell. This unveiled fundamental knowledge pave the way for a preparative protocol of stabilizer-free VE vehicles, which are expected to become widely used in molecular biology research.

Short-Chain Mono-Alkyl ß-D-Glucoside Crystals-Do They Form a Cubic Crystal Structure?

Three-dimensional liquid crystal (LC) phases, cubic LC phases, have been extensively studied as fascinating molecular assembled systems formed by amphiphilic compounds. However, similar structures have only been seen in rare instances in lipid crystal states in glycolipid crystal studies. In this study, we prepared short-chain n-alkyl ß-D-glucosides (CnG) with an alkyl chain length n ranging from 4 to 6 and investigated their crystal structures. First, differential thermal analysis (DTA) and thermogravimetric analysis (TG) measurements showed the formation of hydrated crystals for C4G and C5G, respectively. Second, the crystal structures of CnG (n = 4, 5, 6) in both anhydrous and hydrated states were examined using a temperature-controlled powder X-ray diffraction (PXRD) measurement. Both hydrate and anhydrous crystals of C4G and C5G with critical packing parameters (CPPs) less than 0.33 formed cubic crystal phases. Bilayer lengths, calculated from the main diffraction peaks in each PXRD profile, depended on crystalline moisture for C5G, but no significant change was confirmed for C4G, indicating that the properties of each hydrophilic layer differ. However, C6G with a CPP of 0.42 formed a crystal structure with a modulated lamellar structure similar to C7G and C8G with similar CPP values. Thus, a glycolipid motif concept with a cubic crystal structure was demonstrated.

Clarification of the Complexation Behaviour of 2,6-di-O-Methylated ß-Cyclodextrin and Vitamin E and Radical Scavenging Ability of the Complex in Aqueous Solution.

The precise understanding of the behaviour of vitamin E (α-tocopherol; Toc) complexed with cyclodextrin (CD) additives in aqueous solution is a fundamental issue for further development of their aqua-related biological applications. In this study, the solubilisation and complexation behaviours of Toc with methyl-substituted CD derivatives and the radical scavenging ability of the resulting complexes were precisely investigated in water media. Several problems were encountered upon pre-dissolving Toc in an organic solvent prior to the addition to the water media, such as enhancement of the dispersibility and decrease in the complexation capacity. Additionally, dispersions were obtained in some cases when mixing CD and Toc even in the absence of an organic solvent; therefore, to perform the measurements, a transparent solution was prepared via filtration with a nanopore filter. Consequently, unexpectedly, the addition of certain CD methylated derivatives did not always enhance the solubility of Toc significantly. However, 2,6-di-O-methylated ß-CD (2,6-DMCD) formed a water-soluble inclusion complex with Toc, effectively enhancing its solubility. A phase solubility study indicated the formation of 1:2 or 1:3 Toc/CD inclusion complexes, and the interaction of 2,6-DMCD with both the chromanol head and the phytol chain of Toc was revealed by 2D ROESY nuclear magnetic resonance analysis. The interaction between 2,6-DMCD and the chromanol head was also confirmed for a 2,6-DMCD-2,2,5,7,8-pentamethyl-6-chromanol inclusion complex. Additionally, a rapid scavenging effect for molecularly dissolved Toc was demonstrated even in a system comprising a chromanol head directly encapsulated by CD. Hence, this work elucidated the precise complexation and radical scavenging ability of 2,6-DMCD-Toc in an aqueous solution, which paves the way for its biological applications.

Dual mechanoluminescence system comprising a solid-state di-copper(I) complex containing N-heterocyclic carbene ligands.

A simple N-heterocyclic carbene (NHC) ligand linked to a flexible propylene linker allows the formation of "Cu-Cu"- and "2 Cu"-type geometries inside a molecular framework. The incorporation of two Cu(i) ions in close proximity was observed in the Cu-Cu-type geometry but not in the 2 Cu-type geometry. In this study, the ground-state geometries of solid-state di-copper(i) complexes containing NHC ligands with ethyl substituents were modulated by external stimuli. A crystal with the 2 Cu-type geometry was obtained by the mechanical grinding and heating of a crystal with the Cu-Cu-type geometry, as confirmed by the disappearance of the absorption peak attributed to cuprophilic interaction in the diffuse reflection spectrum. The mechanical grinding of both crystals afforded composite states comprising small crystallites of the corresponding crystalline phases and an amorphous domain. This structural transition was accompanied by tribochromism and chronochromism. The results suggest that these di-copper(i) complexes show promise for the development of stimuli-responsive photoluminescent Cu(i) complexes.

Facile Preparation of Purified Sinapate Ethyl Ester from Rapeseed Meal Extracts Using Cation-exchange Resin in Dual Role as Adsorber and Catalyst.

In this study, cation-exchange resin was used to prepare an esterified antioxidant, sinapate ethyl ester (SE), using ethanolic extracts from rapeseed. A concentration of sinapic acid using the cation-exchange resin in 80% ethanol (aq) and subsequent interesterification of the extract in ethanol using the same resin afforded a product with a purity of 64 wt% and 100% of SE yield. Moreover, after purification using preparative thin-layer chromatography, almost 100 wt% purity was obtained. In an auto-oxidation test, purified SE conferred a much higher antioxidative effect on the bulk oil, emphasising the effectiveness of the protocol using cation-exchange resin for the purification.

Development of Water-Insoluble Vehicle Comprising Natural Cyclodextrin-Vitamin E Complex.

Development of a novel antioxidant-delivery vehicle exerting biosafety has been attracting a great deal of interest. In this study, a vehicle comprising a natural composite consisting of vitamin E (α-tocopherol; Toc) and cyclodextrin (CD) additives was developed, directed toward aqua-related biological applications. Not only ß-CD, but also γ-CD, tended to form a water-insoluble aggregate with Toc in aqueous media. The aggregated vehicle, in particular the γ-CD-added system, showed a remarkable sustained effect because of slow dynamics. Furthermore, a prominent cytoprotective effect by the γ-CD-Toc vehicle under the oxidative stress condition was confirmed. Thus, the novel vitamin E vehicle motif using γ-CD as a stabilizer was proposed, widening the usability of Toc for biological applications.

The Enzymatic Preparation of Human Milk Fat Substitute Intermediate Rich in Palmitic Acid at sn-2 Position and Low-Unsaturated Fatty Acids at sn-1(3) Positions from Palm Oil Substrate.

The lipid products that consist of structured lipids rich in palmitic acid (16:0) at the sn-2 position of triacylglycerol (TAG) and rich in low-unsaturated fatty acids (FAs) (LUFAs), such as oleic acid; 18:1 and linoleic acid; 18:2 at the sn-1(3) positions, are useful intermediates for manufacturing human milk fat substitute (HMFS), which contains functional lipid components. In this study, the HMFS intermediate (HMFS-IM) was enzymatically prepared from palm oil without using other oil sources. First, the amount of 16:0 at the sn-2 position of TAG substrate was enhanced from 18.9% to more 34.5% via a random esterification reaction using a non-stereospecific lipase, Novozym® 435, to produce a random-palm substrate. Consequently, 2-monoacylglycerol (2-MAG) rich in 16:0 at the sn-2 position over 88%, together with the FA ethyl ester substrates rich in LUFAs, such as 18:1-Et and 18:2-Et above 93.5% was prepared through ethanolysis reaction using the same lipase from the random-palm substrate and by purification with urea complexation, respectively. As the preferred modified method, a continuous use of the same lipase to these reactions were achieved while reducing the usage of enzyme to half. Finally, an HMFS-IM rich in 16:0 at the sn-2 position more than 60% and LUFA at sn-1(3) positions was prepared using these palm oil-based products, including random-palm, palm-Et, and 2-MAG, via the interesterification reaction using a 1,3-stereospecific lipase, Lipozyme® RM-IM. Thus, HMFS-IM was successfully prepared by palm oil materials with a 65 wt% usage ratio. The concept described in this study will be useful for HMFS manufacturing from a single natural oil substrate, which is not initially rich in 16:0 at the sn-2 position.

Enzymatic Preparation and Oxidative Stability of Human Milk Fat Substitute Containing Polyunsaturated Fatty Acid Located at sn-2 Position.

The development of human milk fat substitutes (HMFSs), rich in palmitic acid (16:0) at the sn-2 position of triacylglycerol (TAG) and rich in unsaturated fatty acids (FAs) (oleic acid, 18:1 and linoleic acid, 18:2) at the sn-1(3) positions, has gained popularity. In this study, HMFSs containing polyunsaturated fatty acids (PUFAs) predominantly at the sn-2 position were prepared, and their oxidation stabilities were compared. First, a non-PUFA-containing HMFS (NP-HMFS) was produced by enzymatic reactions using Novozyme® 435 and Lipozyme® RM-IM as the enzymes and lard as the raw material. Second, HMFSs, containing 10 % PUFA at the sn-2 or sn-1(3) position, were individually prepared by enzymatic reactions using lard and fish oil as raw materials. Here, sn-2-PUFA-monoacylglycerol (MAG) was extracted from the reaction solution using a mixture of hexane and ethanol/water (70:30, v/v) to produce high-purity sn-2-PUFA-MAG with 78.1 % yield. For the PUFA-containing HMFS substrates, comparable oxidation stability was confirmed by an auto-oxidation test. Finally, HMFSs containing 10 % or 2 % sn-1,3-18:1-sn-2-PUFA-TAG species were prepared by enzymatic reactions and subsequent physical blending. The oxidative stability of sn-1,3-18:1-sn-2-PUFA-HMFS was two-fold higher than that of 1/2/3-PUFA-HMFS in which each PUFA was located without stereospecific limitations in TAG. The removal of PUFA-TAG molecular species with higher concentrations of unsaturated units had a significant effect. In addition, the oxidation stability increased with the addition of tocopherol as an antioxidant. Thus, the combined use of two strategies, that is, the removal of PUFA-TAG molecular species with high concentrations of unsaturated units and the addition of antioxidants, would provide a PUFA-containing HMFS substrate with high oxidative stability.

Unveiling the Uniqueness of Crystal Structure and Crystalline Phase Behavior of Anhydrous Octyl ß-D-Glucoside Using Aligned Assembly on a Surface.

Although the anomalous low crystallinity of octyl ß-D-glucoside (ß-OGlu) was first proposed more than 30 years ago, many fundamental aspects of its crystal structure and of the crystalline phase behavior of the pure substance have remained uncertain. In this paper, we employ grazing-incidence wide-angle X-ray-diffraction measurements using a two-dimensional detector (2D-GI-WAXD) and perpendicularly aligned crystalline films to demonstrate that ß-OGlu forms crystal structures consisting of an intermediate phase-like a ripple phase with two large crystal-lattice constants, a and c, comparable to the lengths of its bilayer structures. Furthermore, solid-to-solid phase transitions accompanied by latent heat confirm the existence of a solid-solution-like phase consisting of a crystalline and a liquid-crystal (LC) phase, which persists over a 20 °C temperature range, in a single-component system. In addition, the system forms a superlattice, accompanied by a change in packing of the component sugars in the partial-melting state; this shift is different from the gel-crystal transition observed for a typical lipid system. These facts indicate that even in the crystalline phase formed from a single component, each individual ß-OGlu molecule in a single-component phase plays a versatile role in the crystallisation and melting processes. These findings must somewhat explain the specific co-assembling features with proteins of ß-OGlu, which has long been used empirically in biochemistry.

Factors determining the reaction temperature of the solvent-free enzymatic synthesis of trehalose esters.

Solvent-free synthesis encourages the design of processes and products that reduce the use and generation of hazardous chemicals. Given the importance of developing greener methodologies, we sought to determine the factors influencing the reaction temperature required for solvent-free, enzymatic synthesis of sugar esters such as trehalose (TRE) esters, using Novozyme 435 as the enzyme catalyst. The use of lauric acid (La) and ethyl laurate (LaEt) as acyl donors did not affect the activation temperature for the generation of trehalose diesters (TDEs), despite the differences in corresponding by-products (water and ethanol). However, when glucose (GLU) and La were employed as reaction substrates as a comparison, glucose monoester (GME) generation readily occurred at much lower temperatures than with the TRE esters, even without a water collection device. Moreover, when the glass transition temperature (Tg) of the sugar substrates increased, a higher reaction temperature was required. These results suggest that while the activation temperature of the reaction did not correlate with the boiling point of the by-product, it did correlate with the glass transition temperature (Tg) of the trehalose substrates. Thus, our work demonstrates the importance of the physical state of amorphous matrices in determining the optimal reaction temperature of a solvent-free sugar synthesis.

Physicochemical characterization of 6-O-acyl trehalose fatty acid monoesters in desiccated system.

The understanding of the basic physicochemical properties of trehalose lipid is indispensable to extending their availability. In this study, the hydrate crystal (Cr), the liquid crystalline (LC) phase and the glassy state formations of 6-O-acyl trehalose fatty acid monoester (TREn) were examined under in a desiccated system. TREn (n = 10, 12, 14, 16) formed monohydrate Cr and showed the hydrate Cr-glassy fluid lamellar LC (Lα) phase transition via dehydration in the heating process. Here, Lα phase for TRE10 and TRE12 was kinetically formed by the dehydration below the glass transition temperature (Tg). On the dehydration temperature (Tdeh), Tgs, and heat capacity changes (ΔCps) at these Tgs, no distinct effects by the difference of the acyl chain length were recognized, possibly because the core structure of containing sugar hydrate Cr or sugar moieties should be similar regardless of the acyl chain length. Besides, TRE10 having a relatively high hydrophilic/hydrophobic balance (HLB) afforded to form the cubic LC (Q) phase and the corresponding glassy phase, while TRE14 and TRE16 having low HLB afforded the Lα phase as well as the corresponding glassy phases above Tg. TRE12 having middle HLB afforded both LCs and the corresponding glassy phase by controlling the kinetics of LC-LC phase transition between Lα and Q phases. Furthermore, the anomalous reversible phase transition during both the heating and cooling processes was also ascertained in the glassy phase for TRE16, which was considered the phase transition between glassy Lα and glassy lamellar gel (Lß) phase. It greatly empathizes the two-dimensional trehalose glass layer and fluid hydrocarbon chains in the TREn glassy phase. Thus, in this study, it was demonstrated that TREn as the simplest trehalose lipid exhibited the glassy formation performance as well as the hydrate Cr formation, which showed less chain length dependence, together with the LC formation and the phase transition between glassy Lα and glassy Lß phase, which depended on chain length greatly.

Dry Thermotropic Glycolipid Self-Assembly:A Review.

Also recognized as carbohydrate liquid crystals, glycolipids are amphiphiles whose basic unit comprises of a sugar group attached to an alkyl chain. Glycolipids are amphitropic, which means these materials form liquid crystal self-assemblies when dry (thermotropic) as well as when dissolved in solvents (lyotropic/surfactants) such as water. Many glycolipids are also naturally derived since these can be found in cell membranes. Their membrane and surfactant functions are largely understood through their lyotropic properties. While glycolipids are expected to play major roles as eco-friendly surfactants in the global surfactant market, their usefulness as thermotropic liquid crystal material is, to date, unknown, due to relatively lack of research performed and data reported in the literature. Understandably since glycolipids are hygroscopic with many hydroxy groups, removing the last trace water is very challenging. In recent time, with careful lyophilization and more consistent characterization technique, some researchers have attempted serious studies into "dry" or anhydrous glycolipids. Motivated by possible developments of novel thermotropic applications, some results from these studies also provide surprising new understanding to support conventional wisdom of the lyotropic systems. Here we review the dry state of glycosides, a family of glycolipids whose sugar headgroup is linked to the lipid chain via a glycosidic oxygen linker. The structure property relationship of both linear and anhydrous Guerbet glycosides will be examined. In particular, how the variation of sugar stereochemistry (e.g. anomer vs. epimer), the chain length and chain branching affect the formation of thermotropic liquid crystals phases, which not only located under equilibrium but also far from equilibrium conditions (glassy phase) are scrutinized. The dry glycolipid assembly has been subjected to electric and magnetic fields and the results show interesting behaviors including a possible transient current generation.

Effect of Freeze-Thaw Treatment on the Precipitation of Octyl ß-D-Galactoside Hemihydrate Crystal from the Aqueous Solution.

Cryogenic treatment, like the freeze-thaw process, has been reported to be effective in modifying the physicochemical properties of polymeric hydrogels. However, not much attention has been paid to this process in terms of the precipitation of surfactant-water systems. In this study, two effective cryogenic methodologies were successfully reported to alter the physicochemical properties of a precipitate of an octyl ß-D-galactoside (Oct-Gal)-water system. First, hyperrapid cooling (i.e., cooling at 30°C/min) was found to be an effective type of cryogenic treatment: the phase transition temperature (TK) and enthalpy at the phase transition (∆HK) between the crystal-dispersed phase and the sol (micelle) phase significantly decreased. In addition, cryogenic treatment in the presence of electrolytes, such as NaCl, NaBr, and CsCl, was effective even in the absence of the hyperrapid cooling condition. The hyperrapid cooling or the addition of certain electrolytes was considered to prevent the precipitation of the Oct-Gal hemihydrate crystals prior to the complete freezing of ice and the electrolyte/ice eutectic. Hence, the size of the aggregated crystals prepared by the above-mentioned effective cryogenic treatments seemed to be decreased compared with that of the normal precipitated crystals, thereby changing TK and ∆HK. Thus, two basic methodologies for the modification of the physicochemical properties of the crystal-dispersed phase of surfactant-water systems are discussed.

Structural Insights into Solid-to-Solid Phase Transition and Modulated Crystal Formation in Octyl-ß-d-Galactoside Crystals.

Despite the significance of synthetic monotailed ß-linked galactolipids, for a detailed understanding of natural galactolipids, many aspects of these ß-linked galactolipids' crystal structures such as temperature-dependence and hydration characteristics remain inadequately understood. In this manuscript, we demonstrated detailed insight of crystal characteristics of one of the simplest monotailed galactolipids, octyl-ß-d-galactoside (MOß-Gal), using thermal analyses, Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD) measurements and grazing-incidence wide-angle X-ray diffraction (GI-WAXD) analysis. As a result, it was revealed that the MOß-Gal anhydrous crystal showed a continuous structural change from the high-symmetry structure to low-symmetry crystal lattice via the strengthened hydrogen bonding interaction as the temperature decreased. In addition, the hemihydrate crystal was found to be in the modulated "ribbon phase". These insights strongly suggest that ß-linked galactolipids possess intrinsic characteristics necessary to form a modulated structure even in the crystal state and demonstrate the importance of the presence of tiny amounts of water as cushioning media for preventing order parameter evolution.

Oligosaccharide-based Surfactant/Citric Acid Buffer System Stabilizes Lactate Dehydrogenase during Freeze-drying and Storage without the Addition of Natural Sugar.

Experiments were conducted to assess the maintenance effects of oligosaccharide-based surfactants on the enzymatic activity of a model protein, lactate dehydrogenase (LDH), during freeze-drying and room temperature storage using the citric acid buffer system. Oligosaccharide-based surfactants, which exhibit a high glass transition temperature (Tg), promoted the eminent retention of enzymatic activity during these protocols, whereas monosaccharide-based surfactants with a low Tg displayed poor performance at high concentration, albeit much better than that of Tween 80 at middle concentration. The increase in the alkyl chain length did not exert positive effects as observed for the maintenance effect during freeze-thawing, but an amphiphilic nature and a glass forming ability were crucial for the effective stabilization at a low excipient concentration during freeze-drying. Even a low oligosaccharide-based surfactant content (0.1 mg mL(-1)) could maintain LDH activity during freeze-drying, but a high surfactant content (1.0 mg mL(-1)) was required to prevent buffer precipitation and retain high LDH activity on storage. Regarding storage, glass formation restricted molecular mobility in the lyophilized matrix, and LDH activity was effectively retained. The present results describe a strategy based on the glass-forming ability of surfactant-type excipients that affords a natural sugar-free formulation or an alternative use for polysorbate-type surfactants.

Lyotropic behavior of a mono-tailed glycolipid assembly during solidification and melting of electrolyte/ice eutectic systems.

The properties of low molecular weight glycolipids at subzero temperatures have been paid much attention due to their great potential for applications in cryopreservation. In this study, the ability of glycolipids to maintain their lyotropic properties was investigated by analyzing the aggregation behavior of octyl-ß-D-glucoside (ß-OGlu) during solidification and melting of electrolyte/ice eutectic mixtures using a simultaneous X-ray diffraction-differential scanning calorimetry measurement and cryomicroscopic observation. During the freezing process, eutectic formation increased the concentration of the ß-OGlu micelle solution in the unfrozen phase, leading to ordering of the molecular assembly. The molecular assembly exhibited a reversible phase transformation between liquid crystalline phases (e.g., lamellar (Lα) and hexagonal (H) phases) and an isotropic micelle solution (I), depending on the degree of eutectic formation, which was regulated by temperature. Because the coexistence of electrolyte/ice eutectic often induces the dehydration of lipids, the persistence of lyotropic properties under such arid conditions demonstrates an attractive performance of glycolipids for use in low temperature applications, such as the cryopreservation of poorly water-soluble drugs or proteins.