Role of Endogenous Ingredients in Meibum and Film Structures on Stability of the Tear Film Lipid Layer against Lateral Compression.

The property and structure of spread films of meibum extruded from rabbit eyelids and its fractions were investigated using the Langmuir film balance technique and Brewster angle microscopy in order to understand the influence of endogenous ingredients in meibum on the structure and stability of the tear film lipid layer against mechanical stimulus. Surface pressure (?)?film area ( A) isotherms for meibum were measured upon repetitive high-speed compression?expansion cycles and were found almost identical to each other with very small hysteresis, indicating the high stability of the meibum film. Brewster angle microcopy observation implied the spontaneous formation of condensed-phase network structures which consist primarily of wax esters and cholesteryl esters as nonpolar ingredients, coexisting with a monolayer phase of polar lipids two-dimensionally confined by the networks, which were spontaneously formed in the meibum film. The networks were gathered densely and deformed when the film was laterally compressed with barriers of Langmuir trough, but returned to the dispersed networks when expanded. The influence of temperature and salts dissolved in an aqueous subphase was also investigated. The results indicated that the temperature change (20 and 35 ?C) induced a difference of surface pressure at the same film areas in rather compressed films, and the presence of salts in the subphase expanded the films. However, the features of isotherm and surface morphology of the film, including their reversibility, were maintained. Phospholipid-removed meibum also formed a stable film, but slight changes were found in the hysteresis and film morphology compared to those in the meibum film. In contrast, in a film of phospholipid- and cholesterol-removed meibum, three-dimensional aggregates grew upon the first compression and not redispersed by the subsequent expansion, giving noticeable hysteresis between the isotherms. It is considered that high deformability upon compression and resilience upon expansion of the networks as well as reversible collapse and spreading property of the confined monolayer phase would hold the stability of the meibum film against repeated compressions.

Fabrication of paper-based analytical devices by a laminating method with thermal ink ribbons, sticky notes, and office appliances.

A stencil printing method utilizing sticky notes, a thermal transfer ink ribbon, and office appliances for paper-based analytical device (PAD) fabrication was proposed. A sticky note was attached to a filter paper, and a mask pattern was cut using a cutting machine. A commercially available thermal ink ribbon was then placed over the mask and laminated. We have characterized the fabricated devices. This approach could be used for the fast and mass prototyping of PADs using simple office appliances with no need for a wax printer.

Phase Transfer of AMIET-functionalized Gold Nanoparticles from Aqueous to Organic Solvents.

This paper presents a feasible and reliable phase transfer protocol for polyoxyethylene alkyl amine surfactant (AMIET)-coated gold nanoparticles (AuNPs) in aqueous media to chloroform using a pH-triggered method, through the liquid-liquid interface. In the initial stage, the colloidal aqueous dispersion is destabilized by pH adjustment towards the isoelectric pH of the nanoparticle, which promotes the separation of the particles from water. We further explored a mechanistic view of this phase transfer phenomenon, considering the orientation of hydrophilic and hydrophobic moieties depending on the nature of the surrounding solvent. It was proposed that the AMIET molecules bound to the AuNPs undergo conformational changes through phase transfer. Ultraviolet visible absorption spectra before and after the phase transfer reveal that the original morphology and dispersion states of the particles were preserved.

Compression-induced Phase Transition in Adsorbed Monolayers of Alkylgalactosides at the Air/Water Interface.

Compression-induced formation of condensed-phase domains in adsorbed monolayers of alkylgalactosides (AGs) at the air/water interface was observed. When an aqueous solution of AGs was poured into a Langmuir trough, the AG molecules were spontaneously adsorbed from the solution at the air/water interface to form the adsorbed or Gibbs monolayer in an expanded, liquid-like phase at equilibrium. The monolayer was subsequently laterally compressed by the barriers of the trough, while simultaneously observing the system using a Brewster angle microscope (BAM). The surface pressure-film area isotherm upon compression showed a kink at a surface pressure (πkink) comparable to or several mN・m-1 higher than the surface pressure at the critical micelle concentration (πCMC), followed by a plateau region. BAM observations revealed that condensed-phase domains were formed in the homogeneous expanded phase at the plateau. Hence, the plateau corresponds to a first-order phase transition from the expanded phase to the condensed phase. As expected, the compressed adsorbed monolayer was in a metastable state because the surface pressure decreased with time, and the condensed-phase domains disappeared when compression was discontinued. The transient formation of a quasi-stable condensed phase may originate from the combined effect of the lower solubility of AG molecules in water, moderately strong attractive intermolecular interactions between AG molecules at the air/water interface, and high-rate compression.

Interactions of l-arginine with Langmuir monolayers of common phospholipids at the air-water interface.

The interactions of l-arginine (l-arg) with Langmuir monolayers of three most common phospholipids, which are sodium salt of dipalmitoylphosphatidylglycerol (DPPG), dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine (DPPE), have been investigated at the air-water interface. The surface pressure-area (π-A) isotherms of these monolayers have been measured with a film balance and monolayer morphology has been observed by a Brewster angle microscopy (BAM). The DPPG monolayers on pure water do not show any phase transition but show irregular shaped condensed phases formed just after evaporation of the solvent at 20 °C. However, this monolayer on l-arg solution subphase indicates a first-order phase transition from liquid expanded to liquid condensed (LE-LC) phases and forms LC domains at the same temperature. With an increase in the l-arg concentration in the subphase up to 5.0 × 10-4 M, the π-A shows an overall increasingly greater expansion in the molecular area. All of the π-A isotherms recorded on ≥5.0 × 10-4 M l-arg solution subphases almost coincide with each other. These changes in the phase behavior have been explained by the fact that l-arg having guanidinium cationic group undergoes strong hydrogen bonding interaction with the anionic phosphatidylglycerol (PG-) head group. The bonding between two molecules is further strengthened by electrostatic attraction between cationic l-arg and anionic PG- ions. The BAM observation of the monolayer morphology supports this explanation. On the other hand, a very negligible interaction has been observed between l-arg and DPPC or DPPE monolayers. The π-A isotherms in the presence of l-arg for both the amphiphiles show a very little expansion only in the LE phase region, but coincide in the so called solid phase region. The monolayer morphology of both the monolayers also supports these results. This little effect of expansion in the LE region may be explained by the ion-pair formation between cationic l-arg and anionic head groups in the monolayers at lower pressures. However, due to compression at high pressure, the l-arg molecules are squeezed out from the amphiphile head groups.

Effect of Mineral-Oil Addition on Film Stability of Polar Lipid Constituents Derived from Meibum.

We studied the effects of mineral oil (MO) on the properties and structure of a spread monolayer of polar lipid constituents in meibum, by performing cyclic lateral compression-expansion experiments using a Langmuir trough. A meibum sample without nonpolar lipids (meibumΔnonpolar-lipid) was prepared by removing the nonpolar lipids from biological meibum extruded from rabbit eyelids and spread on a water surface for measuring the cyclic surface pressure (π)-film area (A) isotherms with in situ observation of the film morphology using a Brewster angle microscope. The meibumΔnonpolar-lipid formed a homogeneous fluid monolayer and underwent collapse upon compression. The π-A isotherm shifted to a smaller area upon repeating the compression-expansion cycles. These observations contrasted those obtained for meibum previously, which may have resulted from the absence of nonpolar lipids. The recovery of the film stability against the lateral compression-expansion cycles was analyzed by adding MO as a nonpolar compound to the film system. A spread film of 1:1 mixture (by weight) could recover the high reversibility of the π-A isotherms during the repeated compression and expansion processes.

Effective quorum quenching with a conformation-stable recombinant lactonase possessing a hydrophilic polymeric shell fabricated via electrospinning.

Quorum sensing (QS) in Gram-negative bacteria is frequently regulated by the diffusible signal N-acylhomoserine lactone (AHL) along with the production of virulence factors in pathogens. To inhibit QS, we fabricated heat-resistant, long-term-stable AHL-lactonase AiiM by electrospinning (ES) aqueous polyvinyl alcohol (PVA) solution containing genetically engineered AiiM with a maltose-binding protein (MBP) tag. MBP-AiiM was immobilized via its inclusion within a dense PVA shell formed during the drying process of ES, followed by cross-linking between hydroxyl groups on PVA. Secondary structure analysis via circular dichroism suggested no conformational change in the MBP-AiiM during ES. Even after pre-heating of MBP-AiiM/PVA fiber mats at 70 °C for 24 h, QS-dependent prodigiosin production in the model pathogen Serratia marcescens AS-1 was effectively inhibited to 0.13% that of the control. Additionally, relative prodigiosin production was reduced to ~20% that of the control after 5-month storage in buffer solution. These results suggest that a shear-thinning process using an entangled PVA aggregate during elongational changes to fibrous domains and a drying process during ES contributes not to enzymatic inactivation caused by conformational changes, but rather to the fabrication of a dense PVA shell around the MBP-AiiM molecules to protect them from disruptors including heating. The developed quorum-quenching enzyme has high potential to inhibit AHL-mediated QS frequently appearing in various Gram-negative bacteria.

Temperature and compression rate independent domain shape in Langmuir monolayers of di-n-dodecyl hydrogen phosphate at the air-water interface.

Thermodynamic and morphological properties of Langmuir monolayers of di-n-dodecyl hydrogen phosphate (DDP) have been studied by film balance and Brewster angle microscopy (BAM) over a wide range of temperature between 5 and 40 degrees C. From pi-A isotherms, a generalized phase diagram consisting of gas (G), liquid expanded (LE) and liquid condensed (LC) phases is constructed for the DDP monolayers. The BAM images show the formation of gas bubble in the bright background of LE phase during G-LE phase transitions and fingering LC domains during LE-LC phase transitions. The shapes of these domains are independent of temperature, showing a sharp contrast to the temperature-dependent monolayer morphologies of amphiphilic systems where the shape of the LC domains changes either from compact circular to fingering or from irregular or spiral to compact patterns with increasing temperature. In addition, the domains do not show any change in their shapes with decreasing the compression rate. Since the two-alkyl chains are directly attached by covalent bonds to the phosphate group, the rearrangement of the molecules needs to move the whole molecules including the hydration sphere. The difficulty related to such a movement of the molecules causes the fingering domains, which are independent of external variables. Although the domains are formed in a fingering shape, the equilibrium shape can be attained by about 120 min at 15 degrees C indicating a rather slow relaxation rate.

How many phases and phase transitions do exist in Gibbs adsorption layers at the air-water interface?

Four different phases and four different first-order phase transitions have been shown to exist in Gibbs adsorption layers of mixtures containing n-hexadecyl dihydrogen phosphate (n-HDP) and L-arginine (L-arg) at a molar ratio of 1:2. These conclusions have been made from surface pressure-time (pi-t) adsorption isotherms measured with a film balance and from monolayer morphology observed with a Brewster angle microscopy (BAM). The observed four phases are gas (G), liquid expanded (LE), liquid condensed (LC) and LC' phases. Three first-order phase transitions are G-LE, LE-LC and LC-LC'. However, the thermodynamically allowed G-LC phase transition in a 1.2 x 10(-4) M mixture at 2 degrees C, which is below the so-called triple point, is kinetically separated into the G-LE and LE-LC phase transitions. The most interesting observation is that the homogeneous LC phase shows a new first-order phase transition named as LC-LC' at 2 or 5 degrees C. The LE and LC phases represent circular and fractal shaped domains, respectively, whereas the LC' phase shows very bright, anisotropic and characteristic shaped domains.

Novel quorum quenching enzymes identified from draft genome of Roseomonas sp. TAS13.

Roseomonas sp. strain TAS13 isolated from an activated sludge sample degrades N-acylhomoserine lactones (AHLs) that are widely utilized as a signal in bacterial quorum sensing systems. The draft genome of Roseomonas sp. TAS13 contains 816 contigs (total 5,078,941 bp) which carries 4760 protein-coding genes and 52 tRNA genes (DDBJ/EMBL/GenBank accession numbers BDLP01000001 through BDLP01000816).

Weak first-order tilting transition in monolayers of mono- and bipolar docosanol derivatives.

A systematic analysis of pressure-area isotherms and grazing incidence X-ray diffraction (GIXD) data of 22-methoxydocosan-1-ol (H3C-O-(CH2)22-OH, MDO), docosan-1-ol (H3C-(CH2)21-OH, DO), and docosyl methyl ether (H3C-(CH2)21-O-CH3, DME) monolayers on pure water between 10 and 35 degrees C is presented. All monolayers form fully condensed phases in the investigated temperature region. The GIXD data reveal that the monolayers exhibit the phase sequence -S at lower temperature and -LS at higher temperature. Phase diagrams have been established. Inserting a second hydrophilic group at the opposite end of the molecule (bipolar MDO) shifts the S/LS boundary to higher temperatures. All monolayers exhibit herringbone (HB) packing at lower temperatures. The "kink" in the isotherms observed at lower temperatures is replaced by a very small plateau region at higher temperatures. The entropy changes connected with this weak first-order tilting transition are much smaller compared with the first-order transition from liquid-expanded (LE) to condensed (LC). Additionally, this transition is endothermic in contrast to the LE/LC transition. The reason for the endothermic transition is the weaker positional correlation in the nontilted state compared with the tilted one. The appearance of the weak first-order endothermic transition can be connected with the changed phase sequence. X-ray photoelectron spectroscopy (XPS) measurements provide information about the polar group orientation. Considerations based on GIXD and XPS data as well as adhesion energy of the different terminal end groups lead to the conclusion that the hydroxyl group of the bipolar MDO is attached to the water surface while the methoxy group is in contact with air. The presented results show that the second hydrophilic group influences the monolayer properties in a mild way.

Effect of temperature on the surface phase behavior of n-hexadecyl dihydrogen phosphate in adsorption layers at the air-water interface.

We present the adsorption kinetics and the surface phase behavior of n-hexadecyl dihydrogen phosphate (n-HDP) at the air-water interface by film balance and Brewster angle microscopy (BAM). A phase diagram, which shows a triple point at about 25.8 degrees C, is constructed by measuring the surface pressure (pi)-time (t) adsorption isotherms. Below 25.8 degrees C, each of the pi-t curves shows a plateau at about zero surface pressure indicating the existence of a first-order phase transition. The BAM observation confirms the order of this phase transition by presenting two-surface phases during this plateau. However, the BAM observation also shows clearly another second-order phase transition from an isotropic phase to a mosaic-textured liquid condensed (LC) phase. The initial phase is a gas (G) phase. Considering the peculiarity of the middle phase, we suggest this phase as an intermediate (I) phase. Above the triple point, the pi-t curves predict the existence of two-step first-order phase transitions. Similar to the results at lower temperatures, the BAM images show two-surface phases during these first-order phase transitions together with a second-order phase transition from an isotropic phase to an LC phase. These transitions are classified as a first-order G-LE (liquid expanded) phase transition, which is followed by another first-order LE-I phase transition. The second-order phase transition is an I-LC phase transition. Contrary to these results, at 36 degrees C both the pi-t measurements and the BAM observation present only two first-order phase transitions, which are G-LE at zero surface pressure and LE-LC transition at higher surface pressure. The shape of the domains during the main transitions shows a peculiar change from a circular at 20 degrees C to an elongated at 24 degrees C and finally to a circular shape at 36 degrees C. Such a change in the domain shapes has been explained considering the dehydration effect at higher temperatures as well as the nature of phases.

Interactions of L-arginine with Langmuir monolayers of di-n-dodecyl hydrogen phosphate at the air-water interface.

The surface phase behavior of di-n-dodecyl hydrogen phosphate (DDP) in Langmuir monolayer and its interactions with L-arginine (L-arg) have been investigated by measuring pi-A isotherms with a film balance and observing monolayer morphology with a Brewster angle microscopy (BAM). The DDP monolayers on pure water show a first-order liquid expanded-liquid condensed (LE-LC) phase transition and form fingering LC domains having uniform brightness at different temperatures. At 15 degrees C, the pi-A isotherms on pure water and on different concentration solutions of L-arg show a limiting molecular area at approximately 0.50 nm(2)/molecule. With increasing the subphase concentration of L-arg up to 4.0 x 10(-4)M, the LE and the LE-LC coexistence regions shift to larger molecular areas and higher surface pressures, respectively. With a further increase in the concentration of L-arg beyond this critical concentration, these isotherms show little or no more expansion. These results have been explained by considering the fact that the L-arg undergoes complexation with the DDP to form L-arg-DDP that remains in equilibrium with the components at the air-water interface. As the concentration of L-arg in the subphase increases, the equilibrium shifts towards the complex. At a concentration of L-arg > or =4.0 x 10(-4)M, the DDP monolayers get saturated and show the characteristics of the new amphiphile, L-arg-DDP. BAM is applied to confirm the above results. When the concentration of the L-arg is <4.0 x 10(-4)M, domains always start forming at an area of approximately 0.64 nm(2)/molecule, which is the critical molecular area for the phase transition in the DDP monolayers on pure water. In contrast, when the monolayers are formed on a solution containing > or =4.0 x 10(-4)M L-arg, comparatively smaller size domains are formed after the appearance of a new cusp point at approximately 0.55 nm(2)/molecule. With an increase in the concentration of L-arg in the subphase, the size of the domains decreases indicating that the fraction of the DDP gradually decreases, whereas the fraction of the complex gradually increases. In addition, a very simple procedure for determination of the stability constant, which is 2.6 x 10(4)M(-1) at 15 degrees C, has been suggested.

Surface phase behavior of di-n-tetradecyl hydrogen phosphate in Langmuir monolayers at the air-water interface.

Surface phase behavior of di-n-tetradecyl hydrogen phosphate, DTP, has been studied by measuring pi-A isotherms with a film balance and observing monolayer morphology with a Brewster angle microscopy (BAM) at different temperatures. A generalized phase diagram, which shows a triple point for gas (G), liquid-expanded (LE) and liquid-condensed (LC) phases at about 32 degrees C, is constructed for the amphiphile. Below the triple point, a first-order G-LC phase transition has been shown to occur, whereas a first-order G-LE phase transition followed by another first-order LE-LC transition has been found to take place at a temperature above the triple point. The amphiphile shows the fingering LC domains with uniform brightness indicating the presence of untilted molecules. The domain shapes are independent of the change in temperature and compression rate. The existence of similar fingering domains over a wide range of temperature is rather uncommon in the monolayer systems and is considered to be due to the restricted movement of the molecules incorporating into the LC phase. Because the two-alkyl chains are directly attached to two covalent bonds of the phosphate head group, the rearrangement of the molecules, which is an essential condition for the circular domain formation, needs the movement of the whole molecules including the hydration sphere. The difficulty related to such a movement of the molecules causes fingering domains, which are independent of external variables.

Self-assembly and crystallization behavior of mesoporous, crystalline HfO2 thin films: a model system for the generation of mesostructured transition-metal oxides.

Mesoporous thin films of crystalline hafnium oxide were fabricated by evaporation-induced self-assembly in combination with sol-gel processing, followed by a suitable post heat-treatment procedure to initiate the crystallization. A novel type of block-copolymer template was used as structure-directing agent, which generated a distorted cubic arrangement of spherical mesopores, the size of which could be quantified by suitable techniques, such as ellipsometry-porosimetry, small-angle X-ray scattering, and atomic force microscopy. Detailed insights into the nature of the crystallization process of mesostructured hafnium oxide were obtained by temperature-dependent, in situ X-ray scattering experiments. These investigations revealed that crystallization takes place, within the confinement of the mesostructure, as a solid-solid transition from a dehydrated, amorphous form of hafnium oxide. The study suggests that one main benefit of the novel template results from the ability of the polymer to stabilize the mesostructure of amorphous hafnium oxide up to 400-450 degrees C.

Adsorption of dimethyl silicone onto hair-surface models prepared with micro-phase separated monolayers.

The adsorption of dimethylsilicone (DMS) from its emulsion onto hair-surface models was investigated. The model surfaces were prepared on silicon wafers by utilizing a micro-phase separation in mixed Langmuir monolayers with a chemically adsorptive organosilane, n-octadecyltriethoxysilane (ODTES), as one component. The resulting surfaces consisted of hydrophobic micro-domains of polymerized ODTES and a surrounding hydrophilic surface silanol (SiOH) region of the silicon wafer, corresponding to the healthy and damaged regions of the hair surface, respectively, in terms of surface wettability. DMS preferentially adsorbed onto the high surface energy hydrophilic region of the model surface when the hydrophobic micro-domains were composed of fully condensed alkyl chains. The surface energy of the micro-domains could be controlled by using palmitic acid (PA) as the second component to form the micro-domains in the phase-separated Langmuir monolayers. The increase in the surface energy of the micro-domains induced the adsorption of DMS onto the intrinsically hydrophobic domain surface.

Kinetic appearance of first-order gas-liquid expanded and liquid expanded-liquid condensed phase transitions below the triple point.

Phase diagram of Gibbs monolayers of mixtures containing n-hexadecyl phosphate (n-HDP) and L-arginine (L-arg) at a molar ratio of 1:2 has been constructed by measuring surface-pressure-time (pi-t) isotherms with film balance and by observing monolayer morphology with Brewster angle microscopy (BAM). This phase diagram shows a triple point for gas (G), liquid expanded (LE), and liquid condensed (LC) phases at around 6.7 degrees C. Above this triple point, a first-order G-LE phase transition occurring at 0 surface pressure is followed by another first-order LE-LC phase transition taking place at a certain higher surface pressure that depends upon temperature. The BAM observation supports these results. Below the triple point, the pi-t measurements show only one first-order phase transition that should be G-LC. All of these findings are in agreement with the general phase diagram of the spread monolayers. However, the BAM observation at a temperature below the triple point shows that the thermodynamically allowed G-LC phase transition is, in fact, a combination of the G-LE and LE-LC phase transitions. The latter two-phase transitions are separated by time and not by the surface pressure, indicating that the G-LC phase transition is kinetically separated into these two-phase transitions. The position of the LE phase below the triple point in the phase diagram is along the phase boundary between the G and LC phases.

Determination of a merocyanine J-aggregate structure and the significant contribution of the electric dipole interaction to the exciton band wavelength.

The molecular alignment of a merocyanine (MC) J-aggregate monolayer at the air-water interface was determined by a grazing incidence x-ray diffraction method. The obtained molecular arrangement apparently shows that the conventional formula, which accounts only for the transition dipole interaction, is not sufficient to figure out the exciton band wavelength, suggesting the importance of the electric dipole (ED) interaction. We derived a simple formula for the ED interaction energy under an extended dipole approximation and clarified the ED contribution in the MC J aggregate.