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Spatial branching processes are ubiquitous in nature, yet the mechanisms that drive their growth may vary significantly from one system to another. In soft matter physics, chiral nematic liquid crystals provide a controlled setting to study the emergence and growth dynamic of disordered branching patterns. Via an appropriate forcing, a cholesteric phase may nucleate in a chiral nematic liquid crystal, which self-organizes into an extended branching pattern. It is known that branching events take place when the rounded tips of cholesteric fingers swell, become unstable, and split into two new cholesteric tips. The origin of this interfacial instability and the mechanisms that drive the large-scale spatial organization of these cholesteric patterns remain unclear. In this work, we investigate experimentally the spatial and temporal organization of thermally driven branching patterns in chiral nematic liquid crystal cells. We describe the observations through a mean-field model and find that chirality is responsible for the creation of fingers, regulates their interactions, and controls the tip-splitting process. Furthermore, we show that the complex dynamics of the cholesteric pattern behaves as a probabilistic process of branching and inhibition of chiral tips that drives the large-scale topological organization. Our theoretical findings are in good agreement with the experimental observations.

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Liquid-crystalline systems are structures that represent an intermediate physical state between isotropic liquid and solid crystal. This particularity brings interesting characteristics of both states such as improved stability, molecular organization, high solubilization potential, diffusion control, and interaction with biological membranes, among others. This chapter describes the structure of liquid-crystalline systems, their classification according to the kind of molecular organization, the material that could be used for liquid crystal formation, the techniques that are applied for characterization, and the process of production. Moreover, the potential of nanostructured liquid-crystalline systems for the delivery of natural products, especially plant-based formulations, is discussed, highlighting the actual state of the art and examples from the literature. Finally, future prospectives for research and application of nanostructured liquid-crystalline systems as formulation of medicines and cosmetic products discussed.

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OBJECTIVE: Psoriasis is a chronic inflammatory skin disorder. Oral or subcutaneous methotrexate (MTX) is a first-line antipsoriatic treatment, whose adverse effects can be observed even at low doses. To minimize systemic side effects, antipsoriatic drugs should be administered topically, since they could permeate the stratum corneum. As liquid crystals with lamellar phase (LP) can be helpful in promoting skin permeation, this work evaluated two MTX-loaded LPs (C1CH and C1CHCE), based on stearic acid, cholesterol and ceramides, like topical treatments for mice with imiquimod-induced psoriasis. METHODS: C1CH and C1CHCE were topically administered to mice with imiquimod-induced psoriasis. Dexamethasone cream was used as positive treatment control. Skin histology and inflammation biomarkers were assessed. KEY FINDINGS: C1CH and C1CHCE exhibited marked immunomodulatory effects and induced extensive microstructural skin remodelling on the epidermis and dermis. These formulations increased keratinization score, epidermis thickness, inflammatory infiltrate, hair follicle hypertrophy and vascular congestion in the dermis. C1CH and C1CHCE also attenuated IL-10 upregulation and upregulated IL-1, IFN-γ, TNF-α and prostaglandin E2 levels, as well as myeloperoxidase, N-acetyl-ß-d-glucosaminidase and cyclooxygenase 2 activity compared with untreated psoriatic animals. CONCLUSION: Although liquid crystals have been reported as good options for carrying topical drugs, they need to be carefully assessed on a case-by-case basis.

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Peptiplexes are soft biomaterials formed through the noncovalent association between cell-penetrating peptides and nucleic acids. Although internalization often involves electrostatic anchoring followed by endocytosis, the mode of action of these transporters remains elusive in many cases, and proper understanding of mechanisms behind their penetrating capabilities necessarily entails structural data at the nanoscopic scale. In this chapter, we examine the structural landscape of peptiplexes, emphasizing the complex behavior of these polyelectrolyte self-assemblies and how supramolecular order impacts their translocation efficiency. We discuss experimental tools commonly used to investigate the structure of peptiplexes and pay special attention to small-angle X-ray scattering (SAXS) as a suitable method for unveiling their nanoscale organization. A roadmap for standard SAXS measurements in CPP/DNA samples is presented alongside a selection of observations from our own experience dealing with SAXS applied to the investigation of CPPs.

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Abstract Liquid crystalline systems of glyceryl monooleate/water are used as drug delivery systems due to their complex structure that controls drug diffusion. Mucoadhesive properties of glyceryl monooleate suggest it can be used for buccal delivery. Using additives is a strategy to modify physical and chemical properties of liquid crystalline systems and optimize their performance as a drug delivery system. However, the presence of additives can significantly alter properties such as phase behavior, swelling and mucoadhesion. Our aim is to investigate the influence of additives on swelling and mucoadhesion of glyceryl monooleate-based liquid crystals, intending them to be used as buccal drug delivery systems. The systems were characterized regarding their mesophases, swelling rate, and mucoadhesion. All the systems studied were able to absorb water and presented mucoadhesion, which is interesting for the development of buccal drug delivery systems. Additives induced phase transitions and affected the swelling performance, while mucoadhesive properties were poorly affected. Propylene glycol increased water uptake, while oleic acid induced the phase transition to the hexagonal phase and reduced the swelling rate. The association of oleic acid (5%) and propylene glycol (10%) resulted in a cubic phase system with strong mucoadhesive properties that can be a potential drug carrier for buccal delivery.

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Curcumin-mediated Photodynamic Inactivation (PDI) has shown great potential to disinfect specific sites on tooth enamel but may involve contact with restorative materials. Thus, before use in dentistry, it is necessary to investigate whether the PDI protocol causes undesirable changes in the surfaces of aesthetic restorative materials and dental enamel. This study investigated the effect of PDI mediated by curcumin (CUR) in a liquid crystal precursor system on color stability (ΔE), surface roughness (Ra), and microhardness (kgf) of three different composite resins and bovine dental enamel specimens. The microhardness and roughness readings were performed 60 days after the treatments while the color readings were performed immediately, 24, 48, and 72 h, 7, 14, 21, 30, and 60 days after the treatments. Results showed that CUR mediated-PDI does not seem to have the potential to promote any esthetic or mechanical changes to the surface of tooth enamel and can be applied safely in clinical practice. However, the results on color, roughness, and hardness obtained for composite resins show that some negative effects can be produced, depending on the type of restorative material; more experiments must be performed with different formulations and, perhaps, with lower concentrations of CUR.

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The properties of supramolecular aggregates cross several disciplines, embracing the sciences of nature and joining theory, experiment, and application. There are few articles centering on the problems of interdisciplinarity, and this paper gives an alternative approach, starting with scientific divulgation, bringing concepts from their origin, to facilitate the access of young scientists to the scientific content. Didactic examples are taken from the experience of the author in changing directions of research due to several circumstances of life (including maternity), starting from the view of a rigorous student of physics and evolving to several subjects in chemistry. The scientific part starts with concepts related to nuclear interactions, using the technique of neutron scattering in reactors, and evolves to research in molecular physics. Finally, it arrives at the academic context, with research in condensed matter physics, with X-ray and other techniques, starting with detergents forming nematic lyotropic liquid crystals and the phase transition sequence of isotropic to nematics to hexagonal. The scientific subjects evolved to biological and bio-inspired liquid crystals, including DNA and also specific lipids and phospholipids in biomimetic membranes. Special attention is given to the question of distribution of matter in these complex systems and the non-trivial connections between biochemistry, structures, auto-aggregation, and biology.

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Whereas their para homologs are not mesogenic, the disk-shaped triphenyltriazine meta-trialkylesters obtained via trimerization of 3-cyanobenzoic alkylester, which are configurationally more flexible, exhibit a monotropic nematic mesophase. Introduction of fluorine atoms into the alkyl chains or into the phenyl moieties leads to the appearance of an enantiotropic columnar mesophase. If fluorine is introduced both in the chains and in the phenyl moieties, only a monotropic mesophase remains. Fluorination of either the alkyl chains or the aromatic core, but not both, appears thus as a simple means of inducing or stabilizing columnar self-assembly in disk-shaped systems. As the homeotropically alignable columnar mesophase can thus be made to persist at room temperature, as energies higher than 3 eV of the first excited triplet state are computed in agreement with the value reported for the parent arene, and as they are not fluorescent themselves, these compounds are of promise as aligning host matrices for blue-emitting TADF devices with improved light outcoupling. Dilution of a columnar with a nonmesogenic homolog induces the nematic state, indicating that the nanoscopic make-up of both mesophases is closely related.

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In this work, we consider a ternary system formed by a surfactant with a lamellar phase (lecithin) that was doped with a solution of Laponite at 1% by volume. The inclusion of nanoparticles in the lamellar phase was investigated by the small-angle X-ray scattering (SAXS) technique, which revealed three types of structures according to the observed scattering pattern. The lamellar period increased linearly with hydration up to a certain limit; this type of behavior is not the same as that found for a similar system using AOT as a surfactant. In the region that corresponds to an isotropic phase, it was observed that the period corresponds to 60 Å, and in the lamellar system of pure lecithin, with the same volumetric fraction (1/φ = 0.66), the corresponding periodicity is 62 Å, indicating that the presence of Laponite nanoparticles increases the attractive interaction, reducing the lamellar period, causing the bilayer to become more rigid, that is, with less fluctuations. In the more diluted region, the periodicity reached a limit value of 64 Å, which is slightly higher than the lamellar system in the absence of Laponite particles, so there was an expansion of the lamellar phase due to the lack of consistency of Laponite nanoparticles. In the more concentrated lamellar phase (under strong confinement), it was observed that the distance between the bilayers decreased, establishing a long-range order.

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The properties of aqueous suspensions of cellulose nanocrystals (CNC) and their casted films are revised. The bio-nanoparticles are briefly introduced, including modifications of the crystals and the suspending media. The formation of CNC-derived liquid crystals (LC) and their resulting rheological behavior are presented. The effects of different variables are addressed: CNC aspect ratio, surface chemistry, concentration, time required for the appearance of an anisotropic phase and addition of other components to the suspension media. The changes on the structure induced by alignment, and by conditions of the drying process are also reported. The optical properties of the films are considered, and the effect of the above variables on the final transparency, iridescence and overall optical response of these bio-inspired photonic materials. Control of the reviewed variables is needed to achieve reliable materials in applications such as sensors, smart inks and papers, transparent flexible supports for electronics, decorative coatings and films.

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Administration of substances through the skin represents a promising alternative, in relation to other drug administration routes, due to its large body surface area, in order to offer ideal and multiple sites for drug administration. In addition, the administration of drugs through the skin avoids the first-pass metabolism, allowing an increase in the bioavailability of drugs, as well as reducing their side effects. However, the stratum corneum (SC) comprises the main barrier of protection against external agents, mainly due to its structure, composition and physicochemical properties, becoming the main limitation for the administration of substances through the skin. In view of the above, pharmaceutical technology has allowed the development of multiple drug delivery systems (DDS), which include liquid crystals (LC), cubosomes, liposomes, polymeric nanoparticles (PNP), nanoemulsions (NE), as well as cyclodextrins (CD) and dendrimers (DND). It appears that the DDS circumvents the problems of drug absorption through the SC layer of the skin, ensuring the release of the drug, as well as optimizing the therapeutic effect locally. This review aims to highlight the DDS that include LC, cubosomes, lipid systems, PNP, as well as CD and DND, to optimize topical skin therapies.

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Polar-terminated 3,5-diarylisoxazole liquid crystals (ILCs) were synthetized and characterized. ILCs are composed by rigid core 3,5-diarylisoxazol, alkyl chain and polar-terminated flexible spacer. Hydroxyl-, ketal- and 1,2-diol-terminated ILCs rendered smectic C and A mesophase, while bromine-terminated ILCs showed smectic A and B mesophase, for monosubstituted and linear ILCs. For branched alkyl chain monotropic SmA was detected and for disubstituted ILCs no mesophase was detected. Out-of-layer fluctuations (OLFs) are discussed based on X-ray diffraction date and textures. The OLFs are dependent on the bromine atom hardness, hydrogen bonding through collective actions and conformational effects at the interface between layers. Smectic translational order parameter (TOP) Σ was also obtained for orientated bromine- and hydroxyl-terminated ILCs and related it with OLFs. For 1,2-diol-terminated ILCs two SmC sublayers were founded, probably related to the intramolecular hydrogen bond favoring the 5-membered and 6-membered formation.

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Scaffolds based on bioconjugated hydrogels are attractive for tissue engineering because they can partly mimic human tissue characteristics. For example, they can further increase their bioactivity with cells. However, most of the hydrogels present problems related to their processability, consequently limiting their use in 3D printing to produce tailor-made scaffolds. The goal of this work is to develop bioconjugated hydrogel nanocomposite inks for 3D printed scaffold fabrication through a micro-extrusion process having improved both biocompatibility and processability. The hydrogel is based on a photocrosslinkable alginate bioconjugated with both gelatin and chondroitin sulfate in order to mimic the cartilage extracellular matrix, while the nanofiller is based on graphene oxide to enhance the printability and cell proliferation. Our results show that the incorporation of graphene oxide into the hydrogel inks considerably improved the shape fidelity and resolution of 3D printed scaffolds because of a faster viscosity recovery post extrusion of the ink. Moreover, the nanocomposite inks produce anisotropic threads after the 3D printing process because of the templating of the graphene oxide liquid crystal. The in vitro proliferation assay of human adipose tissue-derived mesenchymal stem cells (hADMSCs) shows that bioconjugated scaffolds present higher cell proliferation than pure alginate, with the nanocomposites presenting the highest values at long times. Live/Dead assay otherwise displays full viability of hADMSCs adhered on the different scaffolds at day 7. Notably, the scaffolds produced with nanocomposite hydrogel inks were able to guide the cell proliferation following the direction of the 3D printed threads. In addition, the bioconjugated alginate hydrogel matrix induced chondrogenic differentiation without exogenous pro-chondrogenesis factors as concluded from immunostaining after 28 days of culture. This high cytocompatibility and chondroinductive effect toward hADMSCs, together with the improved printability and anisotropic structures, makes these nanocomposite hydrogel inks a promising candidate for cartilage tissue engineering based on 3D printing.

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Hexagonal liquid crystals and supramolecular polymers from meglumine-based supra-amphiphiles were developed as drug delivery systems to be applied on the skin. The influence of fatty acid unsaturation on the structure and mechanical properties was evaluated. Moreover, we have investigated the system biocompatibility and how the type of water could influence its bioadhesive properties. Meglumine-oleic acid (MEG-OA) was arranged as hexagonal liquid crystals at 30-70 wt% water content, probably due to its curvature and increased water solubility. Meglumine-stearic acid (MEG-SA) at 10-80 wt% water content self-assembled as a lamellar polymeric network, which can be explained by the low mobility of MEG-SA in water due to hydrophobic interactions between fatty acid chains and H-bonds between meglumine and water molecules. Both systems have shown suitable mechanical parameters and biocompatibility, making them potential candidates to encapsulate therapeutic molecules for skin delivery. Moreover, a strong positive correlation between the amount of unfrozen bound water in meglumine-based systems and the bioadhesion properties was observed. This work shows that a better understanding of the physicochemical properties of a drug delivery system is extremely important for the correlation with the desired biological response and, thus, improve the product performance for biomedical applications.

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The mol-ecule of the title compound, C27H37NO3, was prepared by [3 + 2] 1,3-dipolar cyclo-addition of 4-n-octyl-phenyl-nitrile oxide and 4-tert-but-oxy-styrene, the latter compound being a very useful inter-mediate to the synthesis of liquid-crystalline materials. In the mol-ecule, the benzene rings of the n-octyloxyphenyl and tert-but-oxy-phenyl groups form dihedral angles of 2.83 (7) and 85.49 (3)°, respectively, with the mean plane of the isoxazoline ring. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen inter-actions into chains running parallel to the b axis.

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In this work we study the geometry of the elastic deformations of the uniaxial nematic liquid crystals at the bulk. We will show that, at this region of the sample, the elastic terms of the free energy can be separated as the sum of two kinds of elastic deformations, the first is proportional to the Gaussian curvature obtained from the director field of a three-dimensional nematic sample and the second is composed by those terms that cannot be expressed as resulting from this curvature. To achieve these results we will construct the metric of an unixial nematic sample using the fact that the director gives the direction of the anisotropy of the system. With this approach we will give analytical and geometrical arguments to show that the elastic terms determined by [Formula: see text], [Formula: see text] and [Formula: see text] are contained in a curvature term, while the terms fixed by the splay elastic term, [Formula: see text], and the bend elastic term, [Formula: see text], are not. The novelty here is that while [Formula: see text] and [Formula: see text] do not contribute the bulk elastic energy of a nematic sample, they have an important contribution to the curvature of the system.

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OBJECTIVE: The main purpose of this article is to show the valuable characteristics that liotropic liquid crystal systems possess to be employed as new drug delivery systems. SIGNIFICANCE: Colloidal aqueous dispersions of lyotropic liquid crystal mesophases such as the identified as cubosomes and hexosomes, and so on, have received considerable attention due to their unique nanostructures and their thermodynamic properties, which provide the potential as a sustained drug release matrix. Additionally, their large surface area and similarity with the liquid crystal structures of intercellular lipids of stratum corneum enhances the interaction with the skin and mucous, increasing the potential for topical drug delivery efficiency of biopharmaceutical class II drugs as the antifungal ketoconazole. METHODS: This article presents the results in morphological characteristics, particle size, ζ potential, flow, thermal behavior and drug release studies of hexosomes containing ketoconazole (LHLC-K) obtained with glycerol monooleate, propylene glycol monolaurate, poloxamer, and water mixtures. RESULTS: This colloidal system exhibits a Newtonian-type flow and a hexagonal nanostructure with a median particle size of 107 ± 20 nm and ζ potential of +4.45 ± 0.50 mV. Through differential scanning calorimetry studies, the LHLC-K demonstrated physical and chemical stability for more than six months and mesophasic thermal reversibility between 10 and 50 °C. Finally, LHLC-K releases ketoconazole following a kinetics described by the first order model. CONCLUSIONS: Physicochemical properties of the hexosomes containing ketoconazole are important for topical mycosis treatment administration, conditions of storage, and for its incorporation into the formulation of semi-solid dosage forms.

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We introduce a density-functional formalism based on the Parsons-Lee and the generalized van der Waals theories in order to describe the thermodynamics of anisotropic particle systems with steric interactions. For ellipsoids of revolution, the orientational distribution function is obtained by minimizing the free energy functional and the equations of state are determined. The system exhibits a nematic-isotropic discontinuous transition, characterized by a phase separation between nematic and isotropic phases at finite as well low packing fractions. The model presents a phase behavior which is in good agreement with Monte Carlo simulations for finite aspect ratios.

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Order-disorder phase transitions driven by temperature or light in soft matter materials exhibit complex dissipative structures. Here, we investigate the spatio-temporal phenomena induced by light in a dye-doped nematic liquid crystal layer. Experimentally, for planar anchoring of the nematic layer and high enough input power, photoisomerization processes induce a nematic-isotropic phase transition mediated by interface propagation between the two phases. In the case of a twisted nematic layer and for intermediate input power, the light induces a spatially modulated phase, which exhibits stripe patterns. The pattern originates as an instability mediated by interface propagation between the modulated and the homogeneous nematic states. Theoretically, the phase transition, emergence of stripe patterns and front dynamics are described on the basis of a proposed model for the dopant concentration coupled with the nematic order parameter. Numerical simulations show quite a fair agreement with the experimental observations.This article is part of the theme issue 'Dissipative structures in matter out of equilibrium: from chemistry, photonics and biology (part 2)'.

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Resveratrol (Res) is a common phytoalexin present in a few edible materials, such as grape skin, peanuts, and red wine. Evidence has shown the beneficial effects of Res on human health, which may be attributed to its anti-inflammatory activity. However, the poor aqueous solubility of Res limits its therapeutic effectiveness. Therefore, the use of nanostructured delivery systems for Res, such as liquid-crystalline systems, could be beneficial. In this study, we aimed to develop, characterize, and determine the in vivo effectiveness of Res-loaded liquid-crystalline systems. Systems containing copaiba balsam oil, polyethylene glycol-40 hydrogenated castor oil, and water were designed. Results of polarized light microscopy, small-angle X-ray scattering, texture-profile analysis, and flow-rheology analysis showed that the Res-loaded liquid-crystalline system had a lamellar structure, textural and mechanical (hardness, compressibility, and adhesiveness) properties, and behaved as a non-Newtonian fluid, showing pseudoplastic behavior upon skin application. Furthermore, all liquid-crystalline systems presented bioadhesive properties that may have assisted in maintaining the anti-inflammatory activity of Res, since the topical application of the Res-loaded lamellar mesophase liquid crystals resulted in edema inhibition in a carrageenan-induced paw-inflammation mouse model. Therefore, Res-loaded lamellar mesophases represent a promising new therapeutic approach for inhibition of skin inflammation.

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