Hexagonal Liquid Crystalline Phase Research Articles

Simple-by-design approach for production of stabilizer-free cubosomes from phosphatidylglycerol and docosahexaenoic acid monoacylglycerol

Docosahexaenoic acid monoacylglycerol represents a promising lipid constituent in the development of drug nanocarriers owing to its amphiphilicity and the beneficial health effects of this docosahexaenoic acid precursor in various disorders including cancer and inflammatory diseases. Here, we describe the formation and characterization of simple-by-design and stabilizer-free lamellar and non-lamellar crystalline nanoparticles (vesicles and cubosomes, respectively) from binary mixtures of docosahexaenoic acid monoacylglycerol and phosphatidylglycerol, which is a ubiquitous amphiphilic component present in biological systems. At the physiological temperature of 37 °C, these single amphiphilic components tend to exhibit inverse hexagonal and lamellar liquid crystalline phases, respectively, on exposure to excess water. They can also be combined and dispersed in excess water by employing a high-energy emulsification method (by means of ultrasonication) to produce through an electrostatic stabilization mechanism colloidally stable nanodispersions. A colloidal transformation from vesicles to cubosomes was detected with increasing MAG-DHA content. Through use of synchrotron small-angle X-ray scattering, cryo-transmission electron microscopy, and nanoparticle tracking analysis, we report on the structural and morphological features, and size characteristics of these nanodispersions. Depending on the lipid composition, their internal liquid crystalline architectures were spanning from a lamellar (Lα) phase to biphasic features of coexisting inverse bicontinuous (Q2) cubic Pn3m and Im3m phases. Thus, a direct colloidal vesicle-cubosome transformation was detected by augmenting the concentration of docosahexaenoic acid monoacylglycerol. The produced cubosomes were thermally stable within the investigated temperature range of 5–60 °C. Collectively, our findings contribute to understanding of the imperative steps for production of stabilizer-free cubosomes from biocompatible lipids through a simple-by-design approach. We also discuss the potential therapeutic use and future implications for development of next-generation of multifunctional vesicles and cubosomes for co-delivery of docosahexaenoic acid and drugs in treatment of diseases.

Study of self-organization and structural phase transitions in water /AOT / isopropyl myristate biocompatible system

This work reports preparation and characterization of biocompatible sodium bis(2-ethylhexyl) sulfosuccinate (AOT) / water/ isopropyl myristate (IPM) systems. We studied their ability to form various self-organized structures such as microemulsions and liquid crystal templates for producing nanoparticles such as drug delivery vehicles, which play an important role in delivery of various substances. We determined concentration and temperature conditions that allow for forming various structures in this system and characterized the structural phase transition from the microemulsion to liquid crystalline phase, which is important for delivery of bioactive compounds. The parameters of the liquid crystalline phase of the water/AOT/isopropyl myristate system were calculated for the first time in this work. The sizes of microemulsion droplets were determined. To describe molecular motions in the studied microemulsion, self-diffusion coefficients of each component were measured. The values of relative diffusion coefficients demonstrated that reverse microemulsions were observed at AOT concentrations up to 60 % wt. Further increase in surfactant concentration slows down their molecular mobility and results in formation of aggregates with a bimodal size distribution and a subsequent formation of the hexagonal liquid crystalline phase. Geometry of the mesophase and its structure were investigated by X-ray diffraction. The respective phase diagram was plotted and analyzed using the data of polarized light microscopy, dynamic light scattering, and NMR self-diffusion. In this diagram, the areas corresponding to the microemulsion, the liquid crystal phase, and the structural phase transition were identified.The study of the structural phase transition from the microemulsion to liquid crystal will offer a predictive power for characterizing incorporation of drugs and controlling their delivery to target cells. A deeper understanding of the structural changes is necessary to clearly determine the conditions of drug delivery.

Pluronic 123 Liquid Lyotropic Crystals for Transdermal Delivery of Caffeic Acid-Insights from Structural Studies and Drug Release.

This study aims to evaluate the percutaneous permeation profiles of caffeic acid (CA) from the cubic and hexagonal liquid crystalline phases of Pluronic P123/water mixtures. The resulting drug-loaded mesophases were subjected to characterisation through deuterium nuclear magnetic resonance spectroscopy and polarised optical microscopy observations. These analyses aimed to evaluate the structural changes that occurred in the mesophases loading with CA. Additionally, steady and dynamic rheology studies were conducted to further explore their mechanical properties and correlate them to the supramolecular structure. Finally, CA release experiments were carried out at two different temperatures to examine the behaviour of the structured systems in a physiological or hyperthermic state. As the concentration of the polymer increases, an increase in the viscosity of the gel is noted; however, the addition of caffeic acid increases microstructure fluidity. It is observed that the temperature effect conforms to expectations. The increase in temperature causes a decrease in viscosity and, consequently, an increase in the rate of permeation of caffeic acid. The CA permeation profile from the prepared formulations is mostly dependent on the structural organisation and temperature. Cubic mesophase LLC 30/CA showed greater skin permeation with good accumulation in the skin at both tested temperatures.

Effect of glycerol incorporation on the liquid crystal structure of sucrose fatty acid ester in aqueous solution

A series of homogeneous samples with high sugar-surfactant content (sucrose fatty acid ester/water and sucrose fatty acid ester/glycerol/water systems) were prepared with well-controlled processes and investigated by DSC, polarized microscopy, X-ray scattering and rheology. Meanwhile the accuracy of the preparation process is confirmed gas chromatography. The polarized microscopy indicates that the ordering degree of the network structure composed of the liquid crystals may be reduced by the glycerol addition. The results of DSC revealed that 50% glycerol solution could significantly inhibit the crystallization of sucrose fatty acid ester and resulted in a significant widening of the temperature interval for the transformation of the liquid crystal phase into the gel phase. In order to further evaluate the effect of glycerol molecules versus water molecules on the liquid crystal structure of sucrose fatty acid ester, we comparatively analyzed the X-ray scattering data from two perspectives: the mass fraction and molar fraction. It was found that 50% glycerol solution could inhibit the crystallization of sucrose fatty acid ester through changing the water-head group interaction of surfactant, facilitates the integration of sucrose fatty acid ester with different alkyl chain length and may reduce the regularity of liquid crystal, both from the perspective of surfactant mass and molar fraction. Furthermore, the addition of 50% glycerol (w/w) does not significantly impede the liquid crystal formation of sucrose fatty acid ester in aqueous solution. However, from the perspective of surfactant mass fraction, glycerol incorporation could reduce the effective cross-sectional areas of the hydrophilic part of sucrose fatty acid ester in aqueous solution and induce the phase transition of hexagonal liquid crystals to aggregates with less positive curvature, while an opposite tendency could be obtained from the perspective of surfactant molar fraction. The conclusions are also confirmed by subsequent rheological test. Moreover, the results of rheological measurements reveals that the interactions among cylindrical units of the hexagonal liquid crystalline phase become weaker and the surfactant molecules aggregate more loosely in the cylindrical unit with the glycerol incorporation. Moreover, the above-mentioned influence of glycerol on the liquid crystal structure of sucrose fatty acid ester in aqueous solution would be similar but more prominent from the perspective of the molar fraction.

Chemical deposition from a liquid crystal template: A highly active mesoporous nickel phosphate electrocatalyst for hydrogen green production via urea electro-oxidation in an alkaline solution

Recently the urea and urinated wastewater electrolysis process has shown promising technology for hydrogen fuel green production in addition to denitrification of wastewater. However, to make the process economically valuable, the electrocatalysts nanoarchitecture, nanometer size, shape, facets, and composition need to be engineered to boost the urea oxidation reaction (UOR). This work demonstrates a simple and novel approach to the synthesis of mesoporous nickel phosphate nanoparticles (meso-NiPO) via chemical deposition from a surfactant liquid crystal template. Typically, the nickel ions dissolved in the aqueous domain of the hexagonal liquid crystalline phase of the Brij®78 template were chemically reacted with the sodium phosphate solution to precipitate the mesoporous nickel phosphate nanoarchitecture after washing up the surfactant. The physicochemical characterizations show the meso-NiPO exhibits an amorphous highly mesoporous structure with a higher specific surface area (43.50 m2/g) compared to the bare nickel phosphate (bare-NiPO, 4.26 m2/g) prepared in the absence of surfactant. The electrochemical performance of meso-NiPO electrocatalyst for the urea oxidation reaction in alkaline solution exhibits superior activity including a lower oxidation onset potential (0.30 V vs. Ag/AgCl), charge transfer resistance (3.35 O) and mass activity of 700.7 mA/cm2 mg at the oxidation potential of 0.6 V vs. Ag/AgCl. Moreover, the meso-NiPO reveals long-term stability, and 97.5% of the steady-state oxidation current was maintained after the 3-hour urea electrolysis test. Using an H-shape urea electrolyzer, the corresponding cathodic hydrogen production rate reached 415 µmol/h and a Faradic efficiency of 96.8 % at an applied bias of 2.0 V. The electroactivity high performance of the mesoporous nickel phosphate is ascribed to the high specific surface area and mesoporous architecture that provide efficient charge transfer, as well as mass transport of the electroactive species. The chemical deposition from a surfactant liquid crystal template has the advantages of a one-pot template, applicable to the synthesis of a wide range of nanomaterials with various compositions and nanoarchitectures at room temperature for application in electrochemical energy production and storage systems.

Combinatorial Screening of Cationic Lipidoids Reveals How Molecular Conformation Affects Membrane-Targeting Antimicrobial Activity.

The search for next-generation antibacterial compounds that overcome the development of resistance can be facilitated by identifying how to target the cell membrane of bacteria. Understanding the key molecular features that enable interactions with lipids and lead to membrane disruption is therefore crucial. Here, we employ a library of lipid-like compounds (lipidoids) comprising modular structures with tunable hydrophobic and hydrophilic architecture to shed light on how the chemical functionality and molecular shape of synthetic amphiphilic compounds determine their activity against bacterial membranes. Synthesized from combinations of 8 different polyamines as headgroups and 13 acrylates as tails, 104 different lipidoids are tested for activity against a model Gram-positive bacterial strain (Bacillus subtilis). Results from the combinatorial screening assay show that lipidoids with the most potent antimicrobial properties (down to 2 μM) have intermediate tail hydrophobicity (i.e., c log P values between 3 and 4) and lower headgroup charge density (i.e., longer spacers between charged amines). However, the most important factor appeared to be the ability of a lipidoid to self-assemble into an inverse hexagonal liquid crystalline phase, as observed by small-angle X-ray scattering (SAXS) analysis. The lipidoids active at lowest concentrations, which induced the most significant membrane damage during propidium iodide (PI) permeabilization assays, were those that aggregated into highly curved inverse hexagonal liquid crystal phases. These observations suggest that the introduction of strong curvature stress into the membrane is one way to maximize membrane disruption and lipidoid antimicrobial activity. Lipidoids that demonstrated the ability to furnish this phase consisted of either (i) branched or linear headgroups with shorter linear tails or (ii) cyclic headgroups with 4 bulky nonlinear tails. On the contrary, lipidoids previously observed to adopt disc-like conformations that pack into bicontinuous cubic phases were significantly less effective against B. subtilis. The discovery of these structure-property relationships demonstrates that it is not simply a balance of hydrophobic and hydrophilic moieties that govern membrane-active antibacterial activity, but also their intrinsic curvature and collective behavior.

Hexagonal liquid crystalline system containing cinnamaldehyde for enhancement of skin permeation of sinomenine hydrochloride

Sinomenine hydrochloride (SH) is usually applied to treat rheumatoid arthritis (RA) with severe side effects due to oral administration. Cinnamaldehyde (CA) as essential oil possesses an anti-RA effect and can facilitate transdermal penetration. Hence, this study developed hexagonal liquid crystalline (HII) gels to deliver two components (SH and CA) across the skins. HII gels were prepared and characterized by polarized light microscopy (PLM), small-angle X-ray scattering (SAXS) and rheology. Moreover, in vitro drug release behavior and ex vivo skin permeation were investigated. Finally, Fourier transforms infrared spectral analysis (FTIR) and confocal laser scanning microscopy (CLSM) were used to explore the skin penetration mechanism. PLM and SAXS showed that the inner structure of the gels was HII phase. The addition of lipophilic or hydrophilic molecules slowed down one another’s release and the release model was dominated by Fickian diffusion (n < 0.43). Furthermore, in vitro permeation studies indicated that appropriate CA could improve the skin permeability of SH. FTIR and CLSM suggested that infiltration occurred due to disruption of the lipid bilayer structure and increased fluidity of the skin. In conclusion, HII gels and CA exhibited a penetration-promoting effect for transdermal applications in SH.

Synthesis and liquid crystalline behavior of hydrazide-functionalized triphenylenedicarboxyimides

ABSTRACT Seven hydrazide-functionalised triphenylenedicarboxyimides (TDIs) which contain a benzamide group bearing different polar substitutes connected to the imide N atom have been studied with the aim to establish the effect of hydrogen bonding and polar substituents on their mesomorphism properties. Six of seven hydrazides each form two types of hexagonal columnar liquid crystalline (LC) phase, including a low-temperature Colho phase and a high-temperature Colhd phase, which were confirmed by characteristic pseudo focal conic fan-shaped textures and XRD measurements. Temperature-dependent FT-IR studies indicated that hydrogen bonding is not strong enough to exist in the LC phases of these hydrazides and disfavours the stabilisation of the columnar mesophase. Nevertheless, dipole–dipole effects were found to favour the mesophase stabilities of these compounds, and the position of the lateral substituent attached to the end benzene ring has a significant impact on the self-assembly by affecting the overall dipole moment.

Ordered hexagonal columnar liquid crystalline self-assembly of mesogen-free sulfonylated side-chain chiral polyethers and their high dielectric property

To achieve large spontaneous polarization for ferroelectric liquid crystalline polymers, we have designed a series of mesogen-free isotactic polyethers with sulfonylated side chains. Different from prior studies using linear alkyl side chains, in this work a methyl branch was implemented in the alkyl side chains of the chiral polyethers. As a result of the continuous twist from the methyl branches and strong dipole-dipole interactions among neighboring sulfonyl groups, a helical chain conformation with tilted side chains was achieved. When the branched side chains were short (e.g., C5) and double chirality existed in both the main chain and side chains, a crystalline structure was obtained. When the branched side chains were long (e.g., ≥ C8) and single chirality existed in the main chain, an ordered hexagonal columnar liquid crystalline phase was induced. Their high-field dielectric property was studied by electric displacement-electric field (D-E) loop tests; however, no ferroelectric behavior was observed up to 200 MV/m. It was considered that the dipole-dipole interaction among neighboring sulfonyl groups in the helical chains was too strong to allow easy ferroelectric flipping.

Phase Behavior and Rheological Properties of Poly(vinyl alcohol)/AES/Water System.

In this work, the phase behavior of the poly(vinyl alcohol) (PVA)/alkyl ethoxysulfate (AES)/water ternary system is investigated at 25 °C. The PVA/AES/water ternary phase diagram is conducted which shows that there are two main phases corresponding to the solid phase and the hexagonal liquid crystalline phase (H) in the ternary system. Besides these two phases, a high-viscosity liquid phase (L2) and a micellar phase (L1) can also be found in the phase diagram, although they just occupy small areas. Polarizing optical microscopy and small-angle X-ray scattering are used to characterize the different lyotropic liquid crystal types. Moreover, the viscosity distribution and oscillation tests are also performed by means of the rheometer. High elastic modulus (G') and viscous modulus (G″) can be found in the H and the L2 phase, whereas both moduli are low in the L1 region. The PVA/AES/water ternary phase diagram provides a good guide for accelerating the selection of the detergent formula, whereas the rheological tests provide an application guidance for industrial operations. Beyond tis, the L1 region is considered to be a reasonable range for slurry making because of its good fluidity and low viscoelasticity. This research enriches the content of polymer-surfactant aggregates and promotes the development of solid detergent manufacturing industry.

Hexosome engineering for targeting of regional lymph nodes

Hexosomes are nanoparticles enveloping inverted discontinuous hexagonal (HII) liquid crystalline phases that offer exceptional physicochemical characteristics for drug encapsulation and targeted drug delivery. However, the fate of subcutaneously injected hexosomes has rarely been investigated. Here, we have followed the lymphatic fate of a technetium-99 m [99mTc]-labeled hexosome preparation on subcutaneous injection into the rat footpads with single-photon emission computed tomography (SPECT) in combination with CT. Hexosomes were composed of phytantriol and oleic acid and sterically stabilized with Pluronic F127. High tracer loading efficiency was achieved by chelating [99mTc]-pertechnetate to 1,12-diamino-3,6,9-triazadodecane-oleic acid conjugates incorporated within the ordered interior nanocompartments of hexosomes. The preparation was characterized by synchrotron small angle X-ray scattering, cryogenic transmission electron microscopy and nanoparticle tracking analysis. On footpad injection, hexosomes rapidly drained into the lymphatic microvessels and distributed not only to the sentinel (popliteal) lymph node, but also to wider lymph nodes (inguinal and iliac nodes) situated along the pathway of the lymph drainage. The observed hexosome drainage kinetics from the injection site and lymphatic distribution pattern is in line with previously established poly(ethylene oxide) configuration attributes of Pluronic F127 in minimizing nanoparticle aggregation at the injection site, and interaction with the ground substance of interstitium, without interfering with macrophage uptake. Accordingly, we discuss the potential utility of Pluronic F127-stabilized hexosomes for lymphatic targeting and future development of simple, yet effective multifunctional lymphotropic agents and theranostics.

Internal Lamellar and Inverse Hexagonal Liquid Crystalline Phases During the Digestion of Krill and Astaxanthin Oil-in-Water Emulsions.

Krill oil represents an important alternative natural source of omega-3 (ω-3) polyunsaturated fatty acids (PUFAs). Considering the beneficial health effects of these essential fatty acids, particularly in various disorders including cancer, cardiovascular, and inflammation diseases, it is of paramount importance to gain insight into the digestibility of krill oil. In this work, we study the fate of krill oil-in-water emulsion, stabilized by sodium caseinate, during lipolysis by coupling time-resolved synchrotron small-angle X-ray scattering (SAXS) to flow-through lipolysis model. For gaining further insight into the effect of ω-3 PUFA-containing oil type on the dynamic structural features occurring during lipolysis, two additional astaxanthin oil-in-water emulsions, stabilized using either sodium caseinate or citrem, were subjected to lipolysis under identical experimental conditions. In addition to the difference in lipid composition in both oils, ω-3 PUFAs in astaxanthin oil, similar to fish oil, exist in the form of triacylglycerols; whereas most of those in krill oil are bound to phospholipids. SAXS showed the formation of highly ordered nanostructures on exposure of these food emulsions to the lipolysis medium: the detection of a biphasic feature of coexisting inverse hexagonal (H2) and lamellar (Lα) liquid crystalline phases in the digested krill oil droplets' interiors, as compared to a neat Lα phase in the digested astaxanthin oil droplets. We discuss the dynamic phase behavior and describe the suggested important role of these phases in facilitating the delivery of nutrients throughout the body. In addition, the potential implication in the development of food and drug nanocarriers is briefly described.

Phase diagram and surface adsorption behavior of benzyl dimethyl hexadecyl ammonium bromide in a binary surfactant-water system

Phase diagram provides valuable information to describe the phase and aggregation behavior of surfactants. In this study, surface adsorption behavior of benzyl dimethyl hexadecyl ammonium bromide (BDHAB) surfactant in water and their phase formations have been explored. The formation of lyotropic liquid crystalline (LLC) phases in the binary surfactant–water system was analyzed by polarized light microscopy (PLM). A comprehensive phase diagram was established presenting the existence of LLC phases as a function of surfactant concentration and temperature. The observed PLM images reveal that the BDHAB–H2O system exhibits isotropic (L1), hexagonal liquid crystalline (H1), cubic (V1), and lamellar (L∞) phases in a sequential pattern with the increase of surfactant concentration. The recorded LLC phases for bi-tail BDHAB–H2O system have also been compared with the phase diagram of single tail cetyl trimethyl ammonium bromide (CTAB)–H2O system. The present study evidence that the surfactant morphology (i.e., alkyl chain length and surfactant head-group area) has a significant influence on the formation of micellar aggregates. In addition, surface tension measurements were also performed to observe the surface adsorption behavior of BDHAB surfactant. This study will be beneficial in understanding the micelle formation and solubilization behavior of bi-tailed quaternary ammonium cationic surfactants to optimize its colloidal formulations.

Lyotropic liquid crystalline nano templates for synthesis of ZnS cogwheels

Herein, we are reporting on the synthesis of zinc sulphide (ZnS) nano/microstructures via soft templating method. Hexagonal lyotropic liquid crystalline phases derived from binary mixtures of potassium soap and water (at different concentraions10:90, 30:70 and 50:50 wt%) are used as soft templates. Flower and hollow resilient cogwheels like (average diameter 100–500 nm) morphologies of ZnS have been obtained from10:90, 30:70 and 50:50 wt:wt% lyotropic templates as confirmed via SEM analysis. All the synthesized ZnS samples exhibit cubic zinc blende crystal structure as confirmed from the XRD measurements. Experimental finding and analysis infer that new kind of morphologies that are obtained for ZnS is not exactly resulted from the templated effect. Flower and cogwheel-like morphologies are results of orientational attachment of ZnS nuclei or coalescence of ZnS crystallite in the vicinity of the hexagonal lyotropic template. The mechanism responsible for such anisotropic growth has also been discussed. Comparing with all ZnS morphologies, cogwheel-like structures show best optical properties as they exhibit a lower band gap of 3.91 eV, low Urbach energy 0.66 eV and smaller dislocation density 16.83 nm−2.

Revisiting dispersible milk-drug tablets as a solid lipid formulation in the context of digestion

Oral delivery of dispersible tablets is a preferred route of administration for paediatrics due to ease of administration and dose control. Milk has gained interest as a drug delivery system due to its ability to dissolve poorly water-soluble drugs. There are no reports of milk tablet formulations being assessed in the context of lipid digestion, which is critical in influencing orally administered drug solubility and bioavailability. Milk-drug tablets were formulated by blending freeze-dried bovine milk or infant formula with the poorly water-soluble drug cinnarizine, which were directly compressed. Tablet strength, friability and dispersibility were quantified and synchrotron X-ray scattering was used to determine the lipid liquid crystalline phases formed during in vitro digestion of dispersed tablets and their effects on drug solubilisation. Tableting had a significant impact on the self-assembly of lipids in redispersed milk tablets whereas no effect was seen for infant formula tablets. Incorporation of the disintegrant poly(vinylpolypyrrolidone) to reduce tablet dispersion times promoted the formation of hexagonal liquid crystalline phases upon digestion but had minimal effect on drug solubilisation. These findings show that similar to the use of liquid milk, the formulation of milk-drug tablets can be used to improve solubilisation of poorly water-soluble drugs.

Columnar Liquid Crystals Self-Assembled by Minimalistic Peptides for Chiral Sensing and Synthesis of Ordered Mesoporous Silica

We report the spontaneous formation of lyotropic liquid crystals from the self-assembly of a series of minimalistic peptides. The highly charged peptides could self-assemble into rigid helical nanofilaments in water and spontaneously order into hexagonal liquid-crystalline phases with interfilament separations of ≤240 A. The formation of liquid crystals from the self-assembly of such simple peptides is dictated not only by the concentration and pH but also by the amino acid sequence of the peptides. Peptides containing the rigid Phe-Phe (FF) segment showed much higher propensities to form a liquid-crystalline phase with long-range order. Moreover, because of the intrinsic chirality of the peptides, the self-assembled birefringent liquid crystals could serve as sensing elements for the visual discrimination of chiral species and as templates for the biomimetic synthesis of mesoporous silica with ordered cavities. The results offer new opportunities for the design of peptide liquid crystals that are potenti...

Large Hexosomes from Emulsion Droplets: Particle Shape and Mesostructure Control.

Soft, rotationally symmetric particles of dispersed hexagonal liquid crystalline phase are produced using a method previously developed for cubosome microparticle production. The technique forms hexosome particles via removal of ethanol from emulsion droplets containing monoolein, water, and one of the various hydrophobic molecules: vitamin E, hexadecane, oleic acid, cyclohexane, or divinylbenzene. The unique rotational symmetry of the particles is characterized by optical microscopy and small-angle X-ray scattering to link particle phase, shape, and structure to composition. Rheology of the soft particles can be varied independently of shape, enabling control of transport, deformation, and biological response by controlling composition and molecular structure of the additives. The direct observations of formation, and the resultant hexosome shapes, link the particle-scale and mesoscale properties of these novel self-assembled particles and broaden their applications. The micron-scale hexosomes provide a route to understanding the effects of particle size, crystallization rate, and rheology on the production of soft particles with liquid crystalline structure and unique shape and symmetry.

The Twofold Role of 12-Hydroxyoctadecanoic Acid (12-HOA) in a Ternary Water-Surfactant-12-HOA System: Gelator and Co-Surfactant.

Gelled lyotropic liquid crystals can be formed by adding a gelator to a mixture of surfactant and solvent. If the gel network and the liquid-crystalline phase coexist without influencing each other, the self-assembly is called orthogonal. In this study, the influence of the organogelator 12-hydroxyoctadecanoic acid (12-HOA) on the lamellar and hexagonal liquid crystalline phases of the binary system H2O–C12E7 (heptaethylene glycol monododecyl ether) is investigated. More precisely, we added 12-HOA at mass fractions from 0.015 to 0.05 and studied the resulting phase diagram of the system H2O–C12E7 by visual observation of birefringence and by 2H NMR spectroscopy. In addition, the dynamic shear moduli of the samples were measured in order to examine their gel character. The results show that 12-HOA is partly acting as co-surfactant, manifested by the destabilization of the hexagonal phase and the stabilization of the lamellar phase. The higher the total surfactant concentration, the more 12-HOA is incorporated in the surfactant layer. Accordingly, its gelation capacity is substantially reduced in the surfactant solution compared to the system 12-HOA–n-decane, and large amounts of gelator are required for gels to form, especially in the lamellar phase.

Exceptional Catalytic Activities and Sensing Performance of Palladium Decorated Anisotropic Gold Nanoparticles

AbstractThe present perspective explores the effect of composition and morphology on the catalytic and surface enhanced Raman scattering (SERS) sensing applications of anisotropic bimetallic gold‐palladium (Au−Pd) nanoparticles. The morphology of the nanoparticles was controlled by a ‘soft’ templating approach by using a hexagonal lyotropic liquid crystalline phase. The mesophases comprised of toluene‐swollen surfactant cylinders, doped with the gold (Au) and palladium (Pd) precursors, stabilized by a monolayer of surfactant and co‐surfactant molecules, arranged in a hexagonal lattice in water as continuous medium. Anisotropic nanostructures of Au having very small Pd nanoparticles deposited on their surface were produced when hexagonal mesophases containing Au and Pd precursors were subjected to gamma irradiation. The synthesized nanomaterials were thoroughly characterized using X‐ray diffraction (XRD), transmission electron microscopy (TEM) and X‐ray photoemission spectroscopy (XPS). These nanomaterials showed exceptionally high catalytic activities for the reduction of 4‐nitrophenol with the normalized rate constant of the bimetallic Au−Pd catalyst being 1.5 times higher than the best catalyst that is reported in the literature. These bimetallic Au−Pd nanostructures also demonstrated very good enhancement for Raman signals of methylene blue by demonstrating an enhancement factor of the order of 106 and a detection limit as low as 0.1 nM.

Immune responses induced by nano-self-assembled lipid adjuvants based on a monomycoloyl glycerol analogue after vaccination with the Chlamydia trachomatis major outer membrane protein

Nanocarriers based on inverse hexagonal liquid crystalline phases (hexosomes) show promising potential as vaccine delivery systems. Their unique internal structure, composed of both lipophilic domains and water-containing channels, renders them capable of accommodating immunopotentiating compounds and antigens. However, their adjuvant properties are poorly understood. We hypothesized that the supramolecular structure of the lyotropic liquid crystalline phase influences the immunostimulatory activity of lipid-based nanocarriers. To test this, hexosomes were designed containing the lipid phytantriol (Phy) and the immunopotentiator monomycoloyl glycerol-1 (MMG-1). Self-assembly of Phy and MMG-1 into nanocarriers featuring an internal hexagonal phase was confirmed by small-angle X-ray scattering and cryogenic transmission electron microscopy. The effect of the nanostructure on the adjuvant activity was studied by comparing the immunogenicity of Phy/MMG-1 hexosomes with MMG-1-containing lamellar liquid crystalline nanoparticles (liposomes, CAF04). The quality and magnitude of the elicited immune responses were determined after vaccination of CB6/F1 mice using the Chlamydia trachomatis major outer membrane protein (MOMP) as antigen. MMG-1-based hexosomes potentiated significantly stronger MOMP-specific humoral responses than CAF04 liposomes. The liposome-based vaccine formulation induced a much stronger MOMP-specific cell-mediated immune response compared to hexosome-adjuvanted MOMP, which elicited minimal MOMP-specific T-cell stimulation after vaccination. Hence, our data demonstrates that hexosomal and liposomal adjuvants activate the immune system via different mechanisms. Our work provides valuable insights into the adjuvant potential of hexosomes and emphasizes that engineering of the supramolecular structure can be used to design adjuvants with customized immunological properties.