Lamellar Liquid Crystalline Phase Research Articles

Phase Behavior and Rheology of the Sucrose Laurate/Sorbitan Mono-laurate (Span 20)/Water Pseudo-ternary System

In order to develop a lamellar liquid crystal system consisting of temperature-insensitive and mild non-ionic surfactants, we construct the phase diagram of sucrose laurate (L1695)/sorbitan monolaurate (Span 20)/water pseudo-ternary systems at 25 ℃ based on the direct visual inspection and polarized microscopy. In contrast to the phase diagrams of polyoxyethylene alkyl ethers and co-surfactant mixtures reported in relevant studies, the single-phase region of the liquid crystalline phase in sucrose laurate (L1695)/sorbitan monolaurate (Span 20)/water pseudo-ternary systems is shown to be narrower. Moreover, the liquid crystal phase behaviors of the sucrose laurate/sorbitan mono-laurate (Span 20)/water pseudo-ternary systems are examined in depth applying cryo-SEM, X-ray scattering measurements, rheological test and low field NMR experiments. In the abovementioned aqueous systems with a L1695 to Span 20 mass ratio (between 53.9: 46.1 and 43.3:56.7), sucrose mono-laurate combines with a certain number of sorbitan monolaurate molecules to form a single lamellar liquid crystalline phase. Furthermore, the present experimental results as well as their analysis could give the quantitative playground for the interaction between sugar-based surfactants in aqueous system, which has rarely been investigated compared with the phase behavior of polyoxyethylene alkyl ethers in aqueous solution.

Luminescent and photoconductive liquid crystalline lamellar and helical network phases of achiral polycatenars

Lamellar and helical network phases of achiral polycatenars. Functional achiral triple chain π-conjugated rod-like molecules were investigated for their photoconductivity, photoluminescence, phosphorescence, and electroluminescence properties.

Topical delivery of seriniquinone for treatment of skin cancer and fungal infections is enabled by a liquid crystalline lamellar phase

Seriniquinone (SQ) was initially described by our group as an antimelanoma drug candidate and now also as an antifungal drug candidate. Despite its promising in vitro effects, SQ translation has been hindered by poor water-solubility. In this paper, we described the challenging nanoformulation process of SQ, which culminated in the selection of a phosphatidylcholine-based lamellar phase (PLP1). Liposomes and nanostructured lipid carriers were also evaluated but failed to encapsulate the compound. SQ-loaded PLP1 (PLP1-SQ) was characterized for the presence of sedimented or non-dissolved SQ, rheological and thermal behavior, and irritation potential with hen's egg test on the chorioallantoic membrane (HET-CAM). PLP1 influence on transepidermal water loss (TEWL) and skin penetration of SQ was assessed in a porcine ear skin model, while biological activity was evaluated against melanoma cell lines (SK-MEL-28 and SK-MEL-147) and C. albicans SC5314. Despite the presence of few particles of non-dissolved SQ (observed under the microscope 2 days after formulation obtainment), PLP1 tripled SQ retention in viable skin layers compared to SQ solution at 12 h. This effect did not seem to relate to formulation-induced changes on the barrier function, as no increases in TEWL were observed. No sign of vascular toxicity in the HET-CAM model was observed after cutaneous treatment with PLP1. SQ activity was maintained on melanoma cells after 48 h-treatment (IC50 values of 0.59–0.98 µM) whereas the minimum inhibitory concentration (MIC) against C. albicans after 24 h-treatment was 32-fold higher. These results suggest that a safe formulation for SQ topical administration was developed, enabling further in vivo studies.

Effects of different degumming processes on the molecular species and microstructures of phospholipids recovered from crude vegetable oils

Phospholipids (PLs), as natural additives and nutritional supplements, are recovered from the gum phase during the degumming process of crude vegetable oils. The molecular species of phospholipids recovered from crude soybean (SO), flaxseed (FO) and peanut oil (PO) by different degumming processes, including water (WD), acid (AD), PLA1(EDA), PLC (EDC) and PLA1-PLC (EDAC) were investigated. According to the PLS-DA model, a total of 30, 38 and 21 characteristic markers were identified using UPLC-Q-TOF-MS in the phospholipids recovered from SO, FO and PO by different degumming processes, respectively. PC (18:2/18:2) and PE (18:2/18:2) were the main phospholipids for WD and AD, LPC (18:2) and LPE (18:2) were the main phospholipids for EDA and EDAC, and PI (16:0/18:2) and PI (16:0/18:1) were served as characteristic phospholipids for EDC. In addition, a lamellar liquid-crystalline phase was observed in the recovered phospholipids, which indicated that the microstructure of phospholipids recovered from crude vegetable oils were significantly influenced by different degumming processes. These differential molecular species of phospholipid products provide useful information to facilitate the potential utilization of phospholipid products as emulsifiers in food and as ingredients in the pharmaceutical industries.

Effect of Flexible Spacer and Alkyl Tail Length on the Liquid Crystalline Phase Behavior of Fullerene Block Molecules.

Here the supramolecular liquid crystalline (LC) phase behavior of a series of fullerene block molecules was investigated regarding spacer length, alkyl tail length and temperature. These compounds exhibit several lamellar LC phases with different packings of self-organized fullerene two-dimensional (2D) crystals. With a short hexamethylene spacer, they form sandwich-like structures with triple or quadruple fullerene layers. By increasing the spacer length to 10 or 12 carbons, a composite layers-in-lamella superlattice structure with alternating soft hydrocarbon single layers and fullerene single or double layers was obtained. As the molecular configurational freedom between incompatible moieties was enhanced by the elongated spacer, the required cross-sectional fullerene-to-hydrocarbon ratio for the superlattice could be achieved despite of different volume fractions of the blocks. The superlattice phase range is efficiently widened by the design principle of constructing LC molecules with a long spacer, which also provides a facile way to tailor novel superstructures.

Novel O/W Emulsions by Utilizing a Vesicle/Disc Transformation of Polyether Modified Silicone.

Emulsification is an important technology in the field of cosmetics and household products. Emulsions are in non-equilibrium state; therefore, the products vary depending on the preparation process, and their state changes with time. Furthermore, it is known empirically that different types of oils have different emulsification properties (preparation and stability). For these reasons, the variables in emulsification research are numerous and complicated to analyze. As a result, many industrial applications have had to rely on empirical rules. In this study, emulsions with a lamellar liquid crystalline phase as an adsorption layer at the emulsion interface were investigated. The characteristics of O/W emulsions formed with the excess solvent phases (aqueous and oil phases) separated from the lamellar liquid crystalline phase were investigated based on the phase equilibrium of the ternary system.As a result, it was found that by agitating the aqueous phase containing dispersed vesicles of emulsifier (polyether modified silicone) together with the oil phase, an emulsion with a uniform interfacial membrane of lamellar liquid crystalline phase could be obtained. The emulsions prepared by this method were found to have good stability against coalescence. The process of transformation from vesicles to the uniform liquid crystal interfacial membrane during the emulsification process was clarified by a freeze-fracture transmission electron micrograph and the calculation of interfacial membrane thickness based on precise particle size analysis. Furthermore, the emulsification properties of polyether-modified silicones were clarified using polar oils and silicone oils, which are a combination of high/low and low/high compatibility with hydrophilic (polyethylene glycol) and lipophilic (polydimethylsiloxane) groups of polyether modified silicone, respectively. It is expected that this research will lead to the evolution of various functionalities in products in the fields of cosmetics, household products, food, pharmaceuticals, paint and others.

Crystalline restacking of 2D-materials from their nanosheets suspensions.

We report here the highly ordered restacking of the layered phosphatoantimonic dielectric materials H3(1-x)M3xSb3P2O14, (where M = Li, Na, K, Rb, Cs and 0 ≤ x ≤ 1), from their nanosheets dispersed in colloidal suspension, induced by a simple pH change using alkaline bases. H3Sb3P2O14 aqueous suspensions are some of the rare examples of colloidal suspensions based on 2D materials exhibiting a lamellar liquid crystalline phase. Because the lamellar period can reach several hundred nanometers, the suspensions show vivid structural colors and because these colors are sensitive to various chemicals, the suspensions can be used as sensors. The structures of the lamellar liquid crystalline phase and the restacked phase have been studied by X-ray scattering (small and wide angle), which has followed the dependence of the lamellar/restacked phase equilibrium on the cation exchange rate, x. The X-ray diffraction pattern of the restacked phase is almost identical to that of the M3Sb3P2O14 crystalline phase, showing that the restacking is highly accurate and avoids the turbostratic disorder of the nanosheets classically observed in nanosheet stacking of other 2D materials. Strikingly, the restacking process exhibits features highly reminiscent of a first-order phase transition, with the existence of a phase coexistence region where both ∼1 nm (interlayer spacing of the restacked phase) and ∼120 nm lamellar periods can be observed simultaneously. Furthermore, this first-order phase transition is well described theoretically by incorporating a Lennard-Jones-type lamellar interaction potential into an entropy-based statistical physics model of the lamellar phase of nanosheets. Our work shows that the precise cation exchange produced at room temperature by a classical neutralization reaction using alkaline bases leads to a crystal-like restacking of the exfoliated free Sb3P2O143- nanosheets from suspension, avoiding the turbostratic disorder typical of van der Waals 2D materials, which is detrimental to the controlled deposition of nanosheets into complex integrated electronic, spintronic, photonic or quantum structures.

Graphene quantum dot doped viscoelastic lyotropic liquid crystal nanocolloids for antibacterial applications.

Graphene quantum dots (GQDs) are prepared and characterized via X-ray diffraction (XRD), UV-Visible spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence (PL). GQDs are doped (5 mg and 10 mg) in the lyotropic liquid crystalline (LLC) lamellar and hexagonal phases to prepare GQD/LLC nanocolloids. Polarizing optical microscopy and X-ray diffraction measurement reveals that GQDs do not affect the lamellar and hexagonal LLC structures and may organize on their interface. Pure LLC phases and nanocolloids are studied for steady and dynamic rheological behavior. LLC phases and GQD/LLC nanocolloids possess shear thinning and frequency dependent liquid viscoelastic behavior. A complex moduli study of LLCs and GQD/LLC nanocolloids is carried out which indicates the gel to viscous transition in LLCs and GQD/LLC nanocolloids as a function of frequency. LLC phases and GQD/LLC nanocolloids are tested for antibacterial activity against Listeria ivanovii. The effect of surfactant concentration, LLC phase geometry and GQD concentration has been studied and discussed. A probable mechanism for the strong antimicrobial activity of LLCs and GQD/LLC nanocolloids is presented considering intermolecular interactions. The viscoelastic behavior and strong antibacterial activity (inhibition zone 49.2 mm) of LLCs and GQD/LLC nanocolloids make them valuable candidates for lubrication, cleaning, cosmetics and pharmaceutical applications.

Doping of γ -Fe3O4 magnetic nanoparticles in Pluronic F127/ DMF LLCs phases to tune the structural transitions and rheological behavior

ABSTRACT A new rapid microwave-assisted approach has been employed to prepare the γ-Fe3O4 magnetic nanoparticles (γ-Fe3O4 MNPs). The formation of spherical γ-Fe3O4 MNPs with an average size of 45 nm and bandgap of 2.3 eV is confirmed by FESEM and UV–Visible spectroscopy. γ-Fe3O4 is doped (0.01 wt% and 0.02 wt%) in the lyotropic liquid crystalline (LLC) lamellar phases of Pluronic F127/N,N dimethylformamide (DMF) to prepare the LLC nanocolloids. Polarizing optical microscopy measurement reveals that γ-Fe3O4 doping does not affect the lamellar LLC structures except 0.02 wt% at 10:90 wt%:wt% system where lamellar to nematic LLC phase transition is observed. Pure LLC phases and nanocolloids are studied for steady and dynamic rheological behavior. LLC phases and LLC nanocolloids possess shear thinning and solid viscoelastic behavior. A complex moduli study of LLCs and LLC nanocolloids is done which indicates the highly elastic strength-based lamellar and nematic phases. Shear-thinning and highly viscoelastic nature of LLCs and LLC nanocolloids have future applications in lubrication, cleaning, cosmetics, and pharmaceutical.

Studying KcsA Channel Clustering Using Single Channel Voltage-Clamp Fluorescence Imaging.

Oligomerization and complex formation play a key role for many membrane proteins and has been described to influence ion channel function in both neurons and the heart. In this study, we observed clustering of single KcsA channels in planar lipid bilayer using single molecule fluorescence, while simultaneously measuring single channel currents. Clustering coincided with cooperative opening of KcsA. We demonstrate that clustering was not caused by direct protein-protein interactions or hydrophobic mismatch with the lipid environment, as suggested earlier, but was mediated via microdomains induced by the channel in the lipid matrix. We found that single channel activity of KcsA requires conically-shaped lipids in the lamellar liquid-crystalline (Lα) phase, and the need for a negative spontaneous curvature seem to lead to the deformations in the membrane that cause the clustering. The method introduced here will be applicable to follow oligomerization of a wide range of membrane proteins.

Neutron Reflectometry & Simultaneous Measurements of Rheology and Small Angle Neutron Scattering Studies for Polyether Modified Silicone Vesicle Systems.

Polyethyleneglycol 12 mol / polydimethylsiloxane co-polymer (PEG-12 dimethicone) is a type of polyether modified silicone (PEMS), which can form a lamellar liquid crystalline phase, and is widely used in cosmetics. The structural changes of PEG-12 dimethicone caused by water contents as well as shear flow were evaluated using simultaneous measurements of rheology and small angle neutron scattering (Rheo-SANS) and neutron reflectometry (NR). At high PEG-12 dimethicone concentrations (≥ 36 wt%), a reorientation of plate-like lamellar structures were observed and the neutral orientation was the most favorable. However, lamella-to-vesicle transitions were hardly observed. PEG-12 dimethicone turned out to form a bi-layer on a hydrophilized Si-wafer in a similar manner to that in bulk though the structure had a certain level of roughness.

Polymer Dispersed Liquid Crystal Film as a Functional and Aesthetic Second Skin Barrier

Polymer films, which reproduce the functional properties of human skin, are emerging as innovative solutions to many skin problems. These films, referred to as second skins, not only serve as a physical barrier to environmental insults but also impart an aesthetic appearance to the skin. Despite being essential components in the cutaneous barrier, lipids have never been included in the second skin films. Here we show that wearable and transparent second skin can be prepared as a polymer dispersed liquid crystal (PDLC) film, where lipid materials are contained as a lamellar liquid crystalline (LC) phase. The lipid materials are mixtures of phytosterol, stearic acid, and lecithin or ceramide, which can be dispersed as lyotropic LC microdroplets in a polymer matrix. The PDLC film can be topically applied as a cosmetic cream (PDLC emulsion), and consequently forms on human skin as a substrate. Structural (X-ray diffraction, XRD), thermal (differential scanning calorimetry, DSC), and surface (atomic force microscopy, AFM) characterizations reveal that our PDLC film has human skin-like features. Notably, the PDLC film can act as an effective barrier against evaporative water loss and carbon pollutants. In a human study (n=10), we have demonstrated that the hydration, adhesion, mechanical, and aesthetic properties of the PDLC film are superior to those of control polymer films. We mainly attribute this in vivo performance to a unique hydration mechanism, whereby the lamellar LC dispersion generates a water concentration gradient and regulates the water content in the PDLC film. Taken together, our beauty film prepared by the PDLC approach is a highly functional cosmetic and potentially serves as a second skin barrier.

Deconstruction of technical grade diglycerol isostearate enables the controlled preparation of hexosomes and liposomes

Glycerol-based technical grade surfactants of industrial interest generally contain a mixture of components with diverse composition. Consequently, their use cannot be generalized since the properties or the technical grade product will likely depend on batches and source. Herein, we address this issue by deconvoluting the role of individual components and pondering their influence on the phase behavior of mixtures. Technical grade diglycerol-monoisostearate (C41) was separated into different fractions based on polarity differences. Three fractions are obtained, which contain mainly unreacted diglycerol, the monoester and higher esterification degree amphiphiles. The formation of a single-phase reverse hexagonal liquid crystal (H2) in the water/C41 system is hindered by the presence of unreacted diglycerol, which dehydrates the hydrophilic channels of the H2 phase. On the other hand, the neat monoester forms a thermotropic lamellar liquid crystalline phase that melts at c.a. 40 °C, as confirmed by X-ray scattering (SAXS) and differential calorimetry (DSC). The formation of the lamellar phase in the neat monoester is ascribed to branching in the alkyl chain. The monoester also forms lamellar liquid crystals mixed with water and remains stable up to high water contents. Moreover, the addition of the higher esterification degree amphiphiles to the monoester/water mixtures promotes a transition from the lamellar phase to a reverse hexagonal one, confirmed by polarized optical microscopy and SAXS. Such transitions can be somehow predicted by calculations of the molecular packing parameters of mixtures. Similar to the lamellar phase, the reverse hexagonal liquid crystal remains stable in excess water. Finally, the coexistence between lamellar or hexagonal phases in excess water is harnessed to produce unilamellar vesicles and hexosomes, as confirmed by dynamic light scattering, SAXS, and cryo-electron microscopy.

Preparation and structural characterization of shear-aligned films in a high proton conductive alkyl-sulfonated polyimide with lyotropic liquid crystallinity

Molecular-organized structures of polymer electrolytes have been extensively studied in recent years. Recently, we demonstrated that alkyl-sulfonated polyimide (ASPI) forms a lyotropic lamellar liquid crystalline (LC) phase under humid conditions and exhibits a high proton conductivity of 10−1 S cm−1 in the in-plane lamella direction at 95% relative humidity. In this work, we conducted precise structural evaluations of the lyotropic LC ASPI for in-plane aligned films prepared by a bar-coating method with a concentrated solution. The ASPI concentrated solution exhibited a birefringent feature and lyotropic LC properties. Humidity-controlled in situ polarized infrared spectroscopy confirmed the in-plane anisotropic structure of the aligned film with clear dichroism, and the dichroism did not change under humidification. Humidity-controlled in situ grazing-incidence X-ray scattering measurement revealed the hierarchical LC structure with main-chain smectic ordering in the lyotropic lamella structure of the shear aligned ASPI film.

Lateral Growth of Uniformly Thin Gold Nanosheets Facilitated by Two-Dimensional Precursor Supply.

The nanosheets of highly symmetric materials with a face-centered cubic lattice such as gold have been synthesized by adsorbing the precursors on a flat surface, whose chemical specificity induces the anisotropy of growth rates. We have succeeded in the fabrication of gold nanosheets in a hydrophilic space inside highly separated bilayers, which work as two-dimensional hydrophilic reactors, in a hyperswollen lamellar liquid crystalline phase of an amphiphile solution. One of the physical properties, amphiphilicity, confines the ingredients therein. The nanosheets can only grow in the in-plane direction due to the inhibition of the out-of-plane growth rather than the anisotropy of growth rates probably. Thus, the synthesis can be accelerated; the particles can be completed within 15 min. As not relying on chemical specificity, silver nanosheets could also be synthesized in the same way. The suspension of gold and silver nanosheets without any amphiphiles could be obtained, and the solvent is replaceable. We found that the width of the obtained gold nanosheets is proportional to the Reynolds number of the solution because the area of the bilayer in the hyperswollen lamellar phase depends on shear stress. This implies that the areas of gold nanosheets depend on the areas of the bilayers, and it can be controlled by changing the Reynolds number. This method could be widely used to continuously obtain large-area nanosheets of various materials in a roll-to-roll manufacturing process.

Design of Roll‐In Margarine Analogous by Partial Drying of Monoglyceride‐Structured Emulsions

AbstractA novel process is proposed to turn soft gelled emulsions containing saturated monoglyceride (MG), sunflower oil, and water into a fat material with the typical water content (20 g/100 g) and rheological properties of roll‐in margarine. A gentle drying procedure at 30 °C is proposed to allow partial water removal from the emulsions, without causing phase separation. Upon water removal, the soft emulsion, initially stabilized by a highly hydrated liquid crystalline lamellar phase of MG, converts into a high internal phase oil–water emulsion (HIPE) stabilized thanks to the presence of MG crystals around gelled oil particles, which are interconnected via polar groups of MG. HIPE at the highest MG content (13.7 g/100 g) shows rheological properties (Gʹ = 4.6 × 105 Pa, critical stress = 634 Pa) comparable to those of commercial roll‐in margarine and is successfully used in baking trials of puff pastry.Practical Applications: The last years have seen an increasing demand for strategies for the nutritional improvement of lipid‐containing foods, due to the emerging health concern related to the consumption of unbalanced saturate/unsaturated fats. Moreover, sustainability issues have arisen due to the abundant use of tropical fats in foods. However, the unique technological and sensory properties of fats make this task very challenging, especially considering the production of laminated products requiring the use of plastic fat materials with peculiar rheological properties. The results obtained in this study are very promising, as they show that the novel fat can be used as an alternative to traditional laminating margarine.

Plasmalogen-Based Liquid Crystalline Multiphase Structures Involving Docosapentaenoyl Derivatives Inspired by Biological Cubic Membranes.

Structural properties of plasmenyl-glycerophospholipids (plasmalogens) have been scarcely studied for plasmalogens with long polyunsaturated fatty acid (PUFA) chains, despite of their significance for the organization and functions of the cellular membranes. Elaboration of supramolecular assemblies involving PUFA-chain plasmalogens in nanostructured mixtures with lyotropic lipids may accelerate the development of nanomedicines for certain severe pathologies (e.g., peroxisomal disorders, cardiometabolic impairments, and neurodegenerative Alzheimer’s and Parkinson’s diseases). Here, we investigate the spontaneous self-assembly of bioinspired, custom-produced docosapentaenoyl (DPA) plasmenyl (ether) and ester phospholipids in aqueous environment (pH 7) by synchrotron small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM). A coexistence of a liquid crystalline primitive cubic Im3m phase and an inverted hexagonal (HII) phase is observed for the DPA-ethanolamine plasmalogen (C16:1p-22:5n6 PE) derivative. A double-diamond cubic Pn3m phase is formed in mixed assemblies of the phosphoethanolamine plasmalogen (C16:1p-22:5n6 PE) and monoolein (MO), whereas a coexistence of cubic and lamellar liquid crystalline phases is established for the DPA-plasmenyl phosphocholine (C16:1p-22:5n6 PC)/MO mixture at ambient temperature. The DPA-diacyl phosphoinositol (22:5n6-22:5n6 PI) ester lipid displays a propensity for a lamellar phase formation. Double membrane vesicles and multilamellar onion topologies with inhomogeneous distribution of interfacial curvature are formed upon incorporation of the phosphoethanolamine plasmalogen (C16:1p-22:5n6 PE) into dioleoylphosphocholine (DOPC) bilayers. Nanoparticulate formulations of plasmalogen-loaded cubosomes, hexosomes, and various multiphase cubosome- and hexosome-derived architectures and mixed type nano-objects (e.g., oil droplet-embedding vesicles or core–shell particles with soft corona) are produced with PUFA-chain phospholipids and lipophilic antioxidant-containing membrane compositions that are characterized by synchrotron SAXS and cryo-TEM imaging. The obtained multiphase nanostructures reflect the changes in the membrane curvature induced by the inclusion of DPA-based PE and PC plasmalogens, as well as DPA-PI ester derivative, and open new opportunities for exploration of these bioinspired nanoassemblies.

Fine tuning the structural colours of photonic nanosheet suspensions by polymer doping.

Aqueous suspensions of nanosheets are readily obtained by exfoliating low-dimensional mineral compounds like H3Sb3P2O14. The nanosheets self-organize, at low concentration, into a periodic stack of membranes, i.e. a lamellar liquid-crystalline phase. Due to the dilution, this stack has a large period of a few hundred nanometres, it behaves as a 1-dimensional photonic material and displays structural colours. We experimentally investigated the dependence of the period on the nanosheet concentration. We theoretically showed that it cannot be explained by the usual DLVO interaction between uniform lamellae but that the particulate nature of nanosheet-laden membranes must be considered. Moreover, we observed that adding small amounts of 100 kDa poly(ethylene oxide) (PEO) decreases the period and allows tuning the colour throughout the visible range. PEO adsorbs on the nanosheets, inducing a strong reduction of the nanosheet charge. This is probably due to the Lewis-base character of the EO units of PEO that become protonated at the low pH of the system, an interpretation supported by theoretical modeling. Oddly enough, adding small amounts of 1 MDa PEO has the opposite effect of increasing the period, suggesting the presence of an additional intermembrane repulsion not yet identified. From an applied perspective, our work shows how the colours of these 1-dimensional photonic materials can easily be tuned not only by varying the nanosheet concentration (which might entail a phase transition) but also by adding PEO. From a theoretical perspective, our approach represents a necessary step towards establishing the phase diagram of aqueous suspensions of charged nanosheets.

Stabilization of vitamin C in emulsions of liquid crystalline structures

Emulsified systems are widely used for topical delivery with the aim of optimizing cutaneous absorption and offering a pleasant sensory. They also may provide a protection of the active molecule against oxidation and/or degradation. The oil phase of o/w emulsions may consist of liquid crystalline structures, especially lamellar structures which are similar to those found in the stratum corneum lipids. In the present work, o/w emulsions containing liquid crystals of mixed cetyl alcohol and Polysorbate 60 were developed for topical delivery of vitamin C, a potent antioxidant with several applications in the cosmetic and pharmaceutical fields. In addition to the well-documented lipid supplementation of the stratum corneum, the liquid crystal emulsions provide a significant chemical stabilization of vitamin C against its degradation. Emulsions were characterized by X-ray diffraction, polarized optical microscopy, and transmission electron microscopy. The stability of vitamin C in the formulations was evaluated upon storage in different conditions of temperature. The emulsions contain a complex colloidal structure, consisting of lamellar liquid crystalline (Lα) and crystalline lamellar gel (Lβ) phases, that provide a very efficient protection of vitamin C against its degradation.

Thermal Behavior of Anhydrous Ascorbic Acid 6‐Palmitate with Trace of Decomposition

AbstractAscorbic acid 6‐palmitate (AsP) is an industrially utilized antioxidant and amphiphilic lipid, which forms a liquid crystalline (LC) phase. Herein, we describe the basic thermal behavior of AsP under anhydrous condition. Grazing‐incidence wide‐angle X‐ray‐diffraction (GI‐WAXD) measurements using a two‐dimensional detector (2D‐GI‐WAXD) and perpendicularly aligned AsP films, together with thermal analysis, showed that the AsP forms only a lamellar LC phase above its melting point (Tm); however, when the LC phase was cooled to facilitate annealing and recrystallization, crystals (Cr) formed with a low degree of crystallinity. Furthermore, a composite system, consisting of the Cr phase and LC phase of AsP, was obtained upon reheating. These anomalous phenomena were likely caused by trace dimerization and decomposition of AsP at a temperature just above Tm, although thermal decomposition accompanied by weight reduction occurred at a much higher temperature in the isotropic phase (IL). Thus, the basic thermal behavior of AsP, which is essential for its use, was unveiled.