Lamellar Lyotropic Liquid Crystal Phase Research Articles

Automation of liquid crystal phase analysis for SAXS, including the rapid production of novel phase diagrams for SDS-water-PIL systems.

Lyotropic liquid crystal phases (LCPs) are widely studied for diverse applications, including protein crystallization and drug delivery. The structure and properties of LCPs vary widely depending on the composition, concentration, temperature, pH, and pressure. High-throughput structural characterization approaches, such as small-angle x-ray scattering (SAXS), are important to cover meaningfully large compositional spaces. However, high-throughput LCP phase analysis for SAXS data is currently lacking, particularly for patterns of multiphase mixtures. In this paper, we develop semi-automated software for high throughput LCP phase identification from SAXS data. We validate the accuracy and time-savings of this software on a total of 668 SAXS patterns for the LCPs of the amphiphile hexadecyltrimethylammonium bromide (CTAB) in 53 acidic or basic ionic liquid derived solvents, within a temperature range of 25-75 °C. The solvents were derived from stoichiometric ethylammonium nitrate (EAN) or ethanolammonium nitrate (EtAN) by adding water to vary the ionicity, and adding precursor ions of ethylamine, ethanolamine, and nitric acid to vary the pH. The thermal stability ranges and lattice parameters for CTAB-based LCPs obtained from the semi-automated analysis showed equivalent accuracy to manual analysis, the results of which were previously published. A time comparison of 40 CTAB systems demonstrated that the automated phase identification procedure was more than 20 times faster than manual analysis. Moreover, the high throughput identification procedure was also applied to 300 unpublished scattering patterns of sodium dodecyl-sulfate in the same EAN and EtAN based solvents in this study, to construct phase diagrams that exhibit phase transitions from micellar, to hexagonal, cubic, and lamellar LCPs. The accuracy and significantly low analysis time of the high throughput identification procedure validates a new, rapid, unrestricted analytical method for the determination of LCPs.

Mesomorphic Polymer Hydrogel Stabilizing Ionic Surfactant Self-Assembly for Fuel Cells

Lyotropic self-assembly of ionic surfactants benefits the construction of ion-conductive pathways but suffers from poor mechanical stability owing to the intrinsic fluidity. Here, a novel mesomorphic polymer hydrogel, featuring a porous network of the cross-linked polymer trapping lyotropic self-assembly of ionic surfactants, is presented for fuel cells. The mesomorphic hydrogel, which is facilely derived from radical polymerization of an acrylamide monomer and a cross-linker in an aqueous solution of 1-tetradecyl-3-methylimidazolium hydrogen sulfate, exhibits not only a lamellar lyotropic liquid crystal phase but also reversible tensile, compressive, and shear deformations. Macroscopic alignment of the mesomorphic hydrogel is achieved by low-frequency shear, and ionic conductivity is promoted to 166 mS cm–1 by virtue of the aligned ion-conductive channels. A hydrogen fuel cell is fabricated from the mesomorphic polymer hydrogel, and a peak power density of 48 mW cm–2 is achieved. Overall, this work provides a strategy to endow functional lyotropic self-assembly with mechanical strengths for diverse electrochemical applications.

Lamellar Lyotropic Liquid Crystal Phases as a Carrier for Skin Delivery of <i>Morus alba</i> Stem Extract

Morus alba stem extract possesses several biological activities. However, skin delivery of the extract is limited by the stratum corneum. In this study, lamellar lyotropic liquid crystal (LLC) was investigated for the potential application in the skin delivery of M. alba stem extract. The four formulations were developed and incorporated with M. alba stem extract at 3% w/w. These formulations were stored at room temperature in light-protected containers for 3 months. The optical pattern under polarized light microscope, viscosity and remaining of the extract were determined. The skin penetration enhancing property of the formulations was investigated using excised porcine ear skin model. The results showed that all formulations remained stable after 3-month storage. The two formulations exhibiting good penetration enhancing properties were F3 consisting of PEG-7 glyceryl cocoate/n-Dodecane/Water/extract (55.29/19.40/22.31/3.00 %w/w) and F4 consisting of mixed Surfactant/n-Dodecane/Water/extract (48.50/4.85/43.65/3.00 %w/w). The mixed surfactant composed of PEG-7 glyceryl cocoate/PEG-40 hydrogenated castor oil/Glyceryl oleate (40/33.24/26.76 %w/w). It can be concluded that the lamellar LLC formulations developed in this study can be used as a carrier for delivering of M. alba stem extract. The components of the formulations which play important roles are the oil and the surfactant.

Self-assembly of an imidazolium surfactant in aprotic ionic liquids. 2. More than solvents.

As tailorable solvents, the physiochemical properties of ionic liquids can be tuned by the structure of ions. Herein, we investigate the structural effects of ILs on the self-assembly of surfactants. It has been confirmed that the cationic surfactant 1-hexadecyl-3-methylimidazolium bromide (C16mimBr) can self-assemble into micellar and lamellar lyotropic liquid crystal phases in the aprotic ionic liquid (AIL) 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim]BF4). In this work, we explore the aggregation behaviours in AILs with different alkyl chains on the imidazolium group, i.e., 1-propyl-3-methylimidazolium tetrafluoroborate ([Pmim]BF4), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4), 1-hexyl-3-methylimidazolium tetrafluoroborate ([Hmim]BF4) and 1-octyl-3-methylimidazolium tetrafluoroborate ([Omim]BF4). With the increase of the cation chain length, AILs have better solubility of the solvophobic part of the surfactants and hence a weaker driving force for self-assembly. Therefore, the critical micellization concentration of C16mimBr in AILs increases as confirmed by the surface tension and small angle X-ray scattering characterizations. More interesting things happen to the phase behaviours. Besides the micellar and lamellar lyotropic liquid crystal phases, a hexagonal lyotropic liquid crystal phase is formed in [Pmim]BF4 while hexagonal and bicontinuous cubic lyotropic liquid crystal phases are formed in [Bmim]BF4, [Hmim]BF4 and [Omim]BF4. It is surprising to observe richer phase behaviours in solvents of lower cohesive energy. The detailed structural information of various aggregates has been obtained by small-angle X-ray scattering. It is demonstrated that AILs work as not only solvents but also co-surfactants.

Protein Expression Knockdown in Cancer Cells Induced by a Gemini Cationic Lipid Nanovector with Histidine-Based Polar Heads

A histidine-based gemini cationic lipid, which had already demonstrated its efficiency as a plasmid DNA (pDNA) nanocarrier, has been used in this work to transfect a small interfering RNA (siRNA) into cancer cells. In combination with the helper lipid monoolein glycerol (MOG), the cationic lipid was used as an antiGFP-siRNA nanovector in a multidisciplinary study. Initially, a biophysical characterization by zeta potential (ζ) and agarose gel electrophoresis experiments was performed to determine the lipid effective charge and confirm siRNA compaction. The lipoplexes formed were arranged in Lα lamellar lyotropic liquid crystal phases with a cluster-type morphology, as cryo-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS) studies revealed. Additionally, in vitro experiments confirmed the high gene knockdown efficiency of the lipid-based nanovehicle as detected by flow cytometry (FC) and epifluorescence microscopy, even better than that of Lipofectamine2000*, the transfecting reagent commonly used as a positive control. Cytotoxicity assays indicated that the nanovector is non-toxic to cells. Finally, using nano-liquid chromatography tandem mass spectrometry (nanoLC-MS/MS), apolipoprotein A-I and A-II followed by serum albumin were identified as the proteins with higher affinity for the surface of the lipoplexes. This fact could be beyond the remarkable silencing activity of the histidine-based lipid nanocarrier herein presented.

Transfection of plasmid DNA by nanocarriers containing a gemini cationic lipid with an aromatic spacer or its monomeric counterpart

This study performed a biophysical characterization (electrochemistry, structure and morphology) and assessment of the biological activity and cell biocompatibility of GCL/DOPE-pDNA lipoplexes comprised of plasmid DNA and a mixed lipid formed by a DOPE zwitterionic lipid and a gemini cationic lipid N-N′-(1,3-phenylene bis (methylene)) bis (N,N-dimethyl-N-(1-dodecyl) ammonium dibromide (12PH12) containing an aromatic spacer or its monomeric counterpart surfactant, N-benzyl-N,N-dimethyl-N-(1-dodecyl) ammonium bromide (12PH). Electrochemical results reveal that i) the gemini cationic lipid (12PH12) and the plasmid pDNA yield effective charges less than their nominal charges (+2 and −2/bp, respectively) and that ii) both vectors (12PH12/DOPE and 12PH/DOPE) could compact pDNA and protect it from DNase I degradation. SAXS and cryo-TEM experiments indicate the presence of a lamellar lyotropic liquid crystal phase represented as alternating layers of mixed lipid and plasmid. Transfection efficiency (by FACS and luminometry) and cell viability assay in COS-7 cells, performed with two plasmid DNAs (pEGFP-C3 and pCMV-Luc VR1216), confirm the goodness of the proposed formulations (12PH12/DOPE and 12PH/DOPE) to transport genetic material, with efficiencies and biocompatibilities comparable to or better than those exhibited by the control Lipofectamine 2000*. In conclusion, although major attention has been paid to gemini cationic lipids in the literature, due to the large variety of modifications that their structures may support to improve the biological activity of the resulting lipoplexes, it is remarkable that the monomeric counterpart surfactant with an aromatic group analyzed in the present work also exhibits good biological activity. The in vitro results reported here indicate that the optimum formulations of the gene vectors studied in this work efficiently transfect plasmid DNA with very low toxicity levels and, thus, may be used in forthcoming in vivo experiments.

A Lyotropic Liquid‐Crystal‐Based Assembly Avenue toward Highly Oriented Vanadium Pentoxide/Graphene Films for Flexible Energy Storage

A novel lyotropic liquid‐crystal (LC) based assembly strategy is developed for the first time, to fabricate composite films of vanadium pentoxide (V2O5) nanobelts and graphene oxide (GO) sheets, with highly oriented layered structures. It is found that similar lamellar LC phases can be simply established by V2O5 nanobelts alone or by a mixture of V2O5 nanobelts and GO nanosheets in their aqueous dispersions. More importantly, the LC phases can be retained with any proportion of V2O5 nanobelts and GO, which allows facile optimization of the ratio of each component in the resulting films. Named VrGO, composite films manifest high electrical conductivity, good mechanical stability, and excellent flexibility, which allow them to be utilized as high performance electrodes in flexible energy storage devices. As demonstrated in this work, the VrGO films containing 67 wt% V2O5 exhibit excellent capacitance of 166 F g−1 at 10 A g−1; superior to those of the previously reported composites of V2O5 and nanocarbon. Moreover, the VrGO film in flexible lithium ion batteries delivers a high capacity of 215 mAh g−1 at 0.1 A g−1; comparable to the best V2O5 based cathode materials.

Lyotropic liquid crystal-assisted synthesis of micro- and nanoparticles of silver

ABSTRACTA simple, one-step approach for the synthesis of micro- and nanoparticles of silver by employing a lyotropic liquid crystal (LLC) template is described. Anisotropic silver particles are synthesised by reducing an appropriate amount of precursor silver nitrate using a mild reducing agent ascorbic acid in presence of a hexagonal LLC medium, without the aid of any external stabilising agents. In this synthesis, precursor concentration, type of the reducing agent and LLC phase are found to significantly influence the particle size and morphology. Either a decrease in the concentration of silver nitrate or a change in the reducing agent, from ascorbic acid to sodium borohydride in the same reaction medium, yielded quasi-spherical nanoparticles. Besides, replacing the hexagonal LLC medium with a lamellar phase during the synthesis using ascorbic acid also resulted in the formation of spherical particles in nanometre scale. As a comparison, gold nanoparticle synthesis is carried out in hexagonal and lamellar LLC phases. Similar to the observations made in the silver particle synthesis, branched anisotropic particles are formed in the hexagonal phase and quasi-spherical particles are produced in the lamellar phase. A possible growth mechanism for the formation of these particles based on the phase structure of the LLC medium is discussed.

Formulation of lyotropic liquid crystal containing mulberry stem extract: influences of formulation ingredients on the formation and the nanostructure

This study focused on the formulation of lamellar lyotropic liquid crystal (LLC) loaded with mulberry stem extract (MSE). The LLC formulation tested used two oils: n-dodecane or tridecyl salicylate, a co-solvent (propylene glycol) and a single (PEG-7 glyceryl cocoate) or mixed surfactant system. The mixed surfactant was PEG-7 glyceryl cocoate/PEG-40 hydrogenated castor oil/glyceryl monooleate. The LLC formation and phase behaviour were observed by polarized optical microscopy (POM) before and after MSE loading. Nanostructure determinations on these formulations following MSE loading used small angle X-ray scattering (SAXS) at 25-40°C. Lamellar LLCs are formed more easily with n-dodecane than tridecyl salicylate. Propylene glycol, in the aqueous phase (1 : 1), failed to form LLC due to suboptimal critical packing parameter (CPP) value. A single or mixed surfactant system also influenced the formation of lamellar LLC according to the chemical structure of both oils and especially the surfactants used. The four lamellar LLC formulations selected for MSE loading were PEG-7 glyceryl cocoate/tridecyl salicylate/water; mixed surfactant/tridecyl salicylate/water; PEG-7 glyceryl cocoate/n-dodecane/water and mixed surfactant/n-dodecane/water, named F1, F2, F3 and F4, respectively. MSE in F1 and F3 did not affect the lamellar structure, while MSE in F2 and F4 enlarged the lamellar structure. The SAXS data confirmed that the LLC formulations obtained were lamellar and the structure persisted with MSE. These lamellar formulations should find widespread application for MSE and perhaps other similar herbal cosmetics.

Lyotropic liquid crystal phases of lithium perfluorinated fatty acid salts in aqueous solutions and molecular dynamics study of the lamellar phase

Anisotropic lyotropic liquid crystal (LLC) of lithium perfluorinated fatty acid salts with long fluorocarbon chains (PFL-Li and PFM-Li, denotes lithium perfluorolaurate and perfluoromyristate, respectively) were prepared in aqueous solutions, and characterized by a variety of techniques in detail. Results of small-angle X-ray scattering (SAXS) study indicate that PFL/M-Li molecules are arranged to form lamellar liquid crystal in water, which were determined by freeze-fracture transmission electron microscopy (FF-TEM) images. Differential scanning calorimetry (DSC) measurements showed that, with the increase of the concentration of lithium perfluorolauric (PFL-Li), the temperature-dependent transition of LLC phases to micelle phases increases. However, LLC phases of lithium perfluoromyristate (PFM-Li), which is not temperature-sensitive, can not be transferred to micelle solution below 100°C. Based on the SAXS measurements, constant volume and temperature (NVT) molecular dynamics (MD) simulation have been carried out to investigate the mechanism for the formation of lamellar LLC phases and their properties.

PH-Sensitive Vesicles and Rheological Properties of PFLA/NaOH/H2O and PFLA/LiOH/H2O Systems

The formation of pH-sensitive vesicles and the rheological properties of the mixtures of perfluorolauric acid (PFLA) and its salts (PFL-Na and PFL-Li) neutralized via NaOH or LiOH were investigated in aqueous solution. When the right mixing ratios of the ionized to nonionzed PFLA molecules with a very high Krafft point are established, vesicles can spontaneously form at room temperature. The vesicles spontaneously formed in the PFLA/PFL-Na/H(2)O system with the rigid fluorocarbon chains were determined by atomic force microscopy images. Compared to those of hydrocarbon amphiphiles, these vesicle samples, which can be kept for 2 years at room temperature, are more stable. The phase transition from the vesicle phase to the lamellar lyotropic liquid crystal phase with the increase of pH was determined by freeze-fracture transmission electron microscopy images in the PFLA/PFL-Li/H(2)O system. The system of perfluoro fatty acid vesicles exhibits much more interesting rheological properties, compared to hydrocarbon fatty acid vesicles. The perfluoro fatty acid vesicle solutions display a much higher yield stress and viscoelastic properties, which depend on two factors: (i) the fluorinated alkyl chains of PFL(-), which are in the crystalline state at room temperature because of their rigid chains compared to analogous hydrocarbon chains, and (ii) the packing of the vesicles, which is very dense. This is the first time that pH-sensitive vesicles exhibiting birefringence were constructed through ionizing perfluoro fatty acid, which may direct primarily toward acquiring an understanding of the mechanism of vesicles depending on the right mixing ratios of the ionized to the nonionzed perfluoro fatty acid molecules with a very high Krafft point and secondarily to expand the development of fluorinated surfactants in both fundamental research and practical applications.

Electrolyte Effects on the Stability of Nematic and Lamellar Lyotropic Liquid Crystal Phases: Colligative and Ion-Specific Aspects

We investigated the electrolyte effects on the stability of nematic and lamellar lyotropic liquid crystalline (LLC) phases formed by the simple anionic surfactant cesium pentadecafluorooctanoate (CsPFO) in water. To the lyotropic guest phase, at the constant CsPFO-mass fraction of 0.55, the series of electrolytes LiCl, NaCl, KCl, CsCl, CsI, and Cs(2)SO(4), respectively, was added at concentrations ranging from 0.5 to 2.5 mol %. With increasing electrolyte concentration two substantially different effects were observed. At low concentrations all added electrolytes caused an increase of the thermal stability of the LLC phases, favoring the lamellar phase over the nematic phase. This behavior is, at least qualitatively, understood within the packing parameter model. The extent of the stabilization clearly depends on the chemical nature of the added cation. For a given cation, however, the effect is colligative, i.e., independent of the chemical nature of the added anion. At higher salt concentrations a salting-out-like phase separation was induced. This effect is clearly ion-specific as the salting-out concentration varied for each cation following the order of the Hofmeister series for cations.

Ordering effects on the photopolymerization of a lyotropic liquid crystal

The synthesis of polymers bearing the highly ordered nanostructure of lyotropic liquid crystal (LLC) phases has recently been of great interest. This work describes the polymerization behavior and structural evolution of a cationic amphiphile in various LLC phases. The type and degree of LLC phases formed from this monomer depend strongly on the composition and temperature. By adding a nonpolymerizable surfactant a variety of LLC phases are formed including hexagonal, bicontinuous cubic, and lamellar morphologies while maintaining a constant monomer concentration. The highly ordered lamellar LLC phase exhibits the fastest polymerization rate with the slowest occurring in the hexagonal phase. The polymerization rates of the bicontinuous morphology were intermediate to the lamellar and hexagonal phases. The faster polymerization kinetics is due to diffusional limitations imposed on the propagating polymer by the highly ordered lamellar LLC phase. Also, the order of this LLC system has a strong dependence on temperature. At higher temperatures, the degree of LLC order and correspondingly the polymerization rate decrease. The original LLC phase morphology appears to be retained to the greatest extent in the faster polymerizing lamellar phase. The original nanostructure is also retained in the hexagonal and cubic LLC phases but with some slight changes in structure. This LLC structure is preserved at temperatures well exceeding the thermal phase transitions of the unpolymerized LLC samples.

Domain Structure in an Unoriented Lamellar Lyotropic Liquid Crystal Phase Studied by2H NMR

The spatial variation of the phase director in an unoriented lamellar lyotropic liquid crystal is investigated by 2H two-dimensional and one-dimensional exchange and PGSE NMR. Exchange NMR probes the single-particle orientational correlation function of D2O molecules that diffuse among regions with different director orientations. The obtained correlation time and the water diffusion coefficient, measured by 2H PGSE NMR, provide the persistence length of director orientation that is defined as domain size. The nature of spatial variation is revealed by the decay of the 2H stimulated echo signal recorded with different evolution times. The persistence length of the director is found to be strongly dependent on the rate of cooling the sample from its isotropic phase.