Lyotropic liquid crystal emulsions of LAVR-289: Influence of internal mesophase structure on cytotoxicity and in-vitro antiviral activity.

Emerging and reemerging viruses pose significant public health threats, underscoring the urgent need for new antiviral drugs. Recently, a novel family of antiviral acyclic nucleoside phosphonates (ANP) composed of a 4-(2,4-diaminopyrimidin-6-yl)oxy-but-2-enyl phosphonic acid skeleton (O-DAPy nucleobase) has shown promise. Among these, LAVR-289 stands out for its potent inhibitory effects against various DNA viruses. Despite its efficacy, LAVR-289s poor water solubility hampers effective drug delivery. To address this, innovative delivery systems utilizing lipidic derivatives have been explored for various administration routes. Submicron lyotropic liquid crystals (LLCs) are particularly promising drug carriers for the encapsulation, protection, and delivery of lipophilic drugs like LAVR-289. This study focuses on developing submicron-sized lipid mesophase dispersions, including emulsified L2 phase, cubosomes, and hexosomes, by adjusting lipidic compounds such as Dimodan® U/J, Lecithins E80, and Miglyol® 812 N. These formulations aim to enhance the solubility and bioavailability of LAVR-289. In vitro evaluations demonstrated that LAVR-289-loaded LLCs at a concentration of 1 µM efficiently inhibited vaccinia virus in infected human cells, with no observed cytotoxicity. Notably, hexosomes exhibited the most favorable antiviral outcomes, suggesting that the internal mesophase structure plays a critical role in optimizing the therapeutic efficacy of this drug class.

Influence of γ-Lactones on Monolinolein/Water Bulk and Emulsified Mesophases.

The emulsification of two flavor compounds of the γ-lactone type with monolinolein liquid crystalline submicron particles is reported. The stabilization is ensured by the copolymer F127. γ-Nonalactone can be loaded in bicontinuous cubic monolinolein particles at a larger level (up to 20 wt %) than γ-decalactone (less than 15 wt %). The phase behavior of the ternary monolinolein/water/γ-nonalactone system was studied. The large γ-nonalactone content solubilized into cubosomes was corroborated by the observation of a wide cubic V2 range in the ternary phase diagram. Surprisingly, no inverted hexagonal phase was found in the system. On the contrary, the incorporation of γ-decalactone in the lipid particles gave rise to a dispersion of inverted hexagonal phase, which corresponds to a classical behavior of an oily additive. We finally determined the internal phase of particles including 10 wt % of γ-nonalactone upon increasing the F127 content. We thus found that γ-nonalactone restricts very significantly the interaction of the emulsifier with the cubosomes' interior.

Nanostructured monolinolein miniemulsions as delivery systems: Role of the internal mesophase on cytotoxicity and cell internalization.

Recent advances in nanoparticle systems for improved drug delivery display a great potential for the administration of active molecules. Here, lipid miniemulsions with various internal nanostructures were loaded with the chemotherapeutic agent Paclitaxel. The goal is to assess the impact of internal structures on their efficiency. Previously the structure, the stability and the physico-chemical properties of those carriers were characterized. Modalities of action were addressed by the evaluation of their effects on the tumor cells viability, their cellular uptake by flow cytometry and confocal microscopy detection of fluorescently labeled nanostructured miniemulsions. Nanostructured miniemulsions showed variations in the cell internalization process likely due to differences in the internal structure. All paclitaxel-loaded emulsions were active reservoirs from which Paclitaxel could be released, however bicontinuous cubosomes showed the best efficiency. Considering the fact that these delivery systems can offer a new life to bioactive compounds previously abandoned due to a low aqueous solubility, these data may represent an important step towards the development of new clinical therapeutic strategies against cancers.

Interface tuning and stabilization of monoglyceride mesophase dispersions: Food emulsifiers and mixtures efficiency.

Several food surfactants were examined as possible efficient emulsifiers for liquid crystalline monolinolein-based particles and as alternative choices to the non-food-grade emulsifier conventionally used Pluronic® F127. We described a food emulsifiers' toolbox, investigating their ability to emulsify mesophases (stabilization capacity, particle size, zeta potential) and their impact on internal nanostructures (from swelling to drastic modifications). Among the selected surfactants, sucrose stearate (S1670) was found to be the best candidate for replacing in a long term F127 as an efficient stabilizer of lipid particles. The emulsification performed by mixing F127 with S1670 or sodium caseinate (NaCas), and S1670/NaCas helped to discriminate their respective role in the particles and so their efficiency for the stabilization. In case of S1670 as co-emulsifier no strong structural modification was observed, while using F127 (25wt% NaCas) an unexpected hexagonal mesophase was highlighted in self-assemblies. The evolution of zeta potentials by varying the mesophase and the emulsifier also informed about the distribution of co-surfactants in the particles. We thus reported submicronic nanostructured systems (from 100 to 350nm) that were fully food-grade and possibly contained limonene, with a surface charge from -70 to -5mV.

Biological Activity of Polynesian Calophyllum inophyllum Oil Extract on Human Skin Cells.

Oil from the nuts of Calophyllum inophyllum, locally called "Tamanu oil" in French Polynesia, was traditionally used for wound healing and to cure various skin problems and ailments. The skin-active effect of "Tamanu oil emulsion" was investigated on human skin cells (keratinocytes and dermal fibroblasts) and showed cell proliferation, glycosaminoglycan and collagen production, and wound healing activity. Transcriptomic analysis of the treated cells revealed gene expression modulation including genes involved in the metabolic process implied in O-glycan biosynthesis, cell adhesion, and cell proliferation. The presence of neoflavonoids as bioactive constituents in Tamanu oil emulsion may contribute to these biological activities. Altogether, consistent data related to targeted histological and cellular functions brought new highlights on the mechanisms involved in these biological processes induced by Tamanu oil effects in skin cells.

Influence of the stabilizer concentration on the internal liquid crystalline order and the size of oil-loaded monolinolein-based dispersions.

The internal phase of monolinolein-based dispersions loaded with tetradecane or (R)-(+)-limonene was investigated as a function of the stabilizer content by small-angle X-ray scattering. Phase transitions at the colloidal scale were found in some of nanostructured aqueous dispersions by increasing the stabilizer content. For particles containing a bicontinuous cubic phase, a large increase of the stabilizer concentration promoted a liquid crystalline phase transition from the Pn3m to the Im3m cubic symmetry. The coexistence of both phases is observed in an intermediate stabilizer concentration range. For particles with an internal micellar cubic Fd3m symmetry, the internal structure changes in the isotropic fluid L(2) phase. In case of particles with an internal hexagonal phase (H(2) symmetry), the increasing amount of stabilizer did not alter the lattice parameter but decreased the size of the nanostructured domain. Moreover, we showed for hexagonal and emulsified micellar phase particles that the increase of the stabilizer content induced a strong decrease of the mean hydrodynamic size of the particles, allowing producing nanostructured lipid-based liquid crystalline particles down to a radius of 70 nm at the same energy input.

Internally self-assembled thermoreversible gelling emulsions: ISAsomes in methylcellulose, kappa-carrageenan, and mixed hydrogels.

Self-assembled thermo-gelling emulsions were developed by blending internally self-assembled particles (ISAsomes) with thermoreversible polysaccharide hydrogels of methylcellulose (MC), kappa-carrageenan (KC), and their 1:1 mixture. In this way, the hierarchical structure of ISAsome samples was successfully promoted. The gelified polymer network corresponds to the highest level of the hierarchical structure and as such represents the capturing matrix for the medium structural level, i.e., dispersed emulsion particles, which are further internally structured as the lowest level of structure. Utilizing small-angle X-ray scattering, differential scanning calorimetry, dynamic light scattering, and oscillatory rheological experiments in the temperature regime from 20 to 70 degrees C, we were able to show that the ISAsomes stay practically intact during such embedment into a hydrogel matrix retaining its internal self-assembled structure and its functionality. The characteristic sol-gel and gel-sol transition temperatures of the ISAsome-loaded hydrogel samples showed a slight shift in comparison to the unloaded hydrogel samples. Furthermore, we found that MC is actually able to stabilize the ISAsomes at higher temperatures (tests were conducted up to 90 degrees C). Gels made from MC and KC show quite different features in terms of rheology and differential scanning calorimetry. However, the most interesting results were obtained for the ISAsome-loaded MC-KC (1:1) gelifying system, which behaves as a low- and high-temperature gel with a narrow intermediate temperature window where it is a sol. This specific thermal behavior allows for easy temperature tuning of the system's aggregate state as well as the internal self-assembled structure. As such, this system is suggested to be further tested as the potential media for a temperature-controlled burst/sustained release media of various hydrophilic, hydrophobic, or amphiphilic guest functional molecules.

Internally structured pickering emulsions stabilized by clay mineral particles.

The present study aims to describe emulsion particles containing a dispersed phase composed of nanostructured lipid mesophases and stabilized by montmorillonite and/or Laponite clay platelets. The size distributions of these emulsion particles were found independent of the clay mineral content and of the initial internal composition that determines the internal structure. The stabilization of the droplets by a shell of smectite layers was found possible even by montmorillonite which has a length of the same order or more than the droplets to stabilize. The clay platelets give a local flatness to the droplets that may influence the internal structure. In this paper, we describe the conditions to obtain such soft particles of about 220 nm, and we show by direct visualization the internal mesophase complexity and the shape of the particles. In particular, TEM analysis showed elongated particles with bent-back channels at their center but a different morphology at the periphery due to flat border conditions imposed by the presence of the clay minerals.

Ordered structures in carboxymethylcellulose-cationic surfactants-copper ions precipitated phases: in situ formation of copper nanoparticles.

Small-angle X-ray scattering has been used to investigate the nanostructures in precipitated phases of carboxymethylcellulose/oppositely charged C(n)TAB surfactants mixtures in interaction with bivalent copper ions. In copper-free precipitates, a transition from a 2D hexagonal phase H(I) to a micellar cubic surfactant structure Pm3n was found on increasing the polymer concentration (n = 14, 16). By addition of small amounts of copper ions, the internal structure also changes from H(I) to Pm3n cubic and finally turns into a less-ordered phase. The concentration at which this transition occurs strongly depends on the surfactant tail length. The presence of copper ions in the precipitated phase leads at the same time to a disorganization of the surfactant micelles' order and to the formation of a lamellar ordering, revealed by the presence of additional diffraction peaks above 10 mM copper. We used the polymer/surfactant networks as template systems, controlled by the copper ion content, for preparing embedded copper nanoparticles via in situ reduction of copper sulfate by sodium borohydride. The zerovalent copper particles formed in the cubic lattice are well-defined in size (less than 10 nm) and have a homogeneous distribution, whereas they are very polydisperse when the reduction is performed in the unorganized phase because the lack of order in the matrix does not protect them from aggregation.

Internally self-assembled particles entrapped in thermoreversible hydrogels.

The present study describes the development of thermogelling emulsions by the entrapment of internally self-assembled emulsion droplets (ISAsomes) within a thermoreversible hydrogel made of kappa-carrageenan. The droplets are emulsified mesophases of cubic or hexagonal order, or emulsified micro-emulsions. Above 60 degrees C, the system was fluid and composed of a mixture of internally nanostructured small droplets and polymer chains dispersed in water. Below 60 degrees C, a physical gel with entrapped droplets was formed. A tuning of the temperature in order to switch between the gel and solution state did not affect the particles in terms of size. The thermoreversible behavior of the loaded polymer network and the effects on the internal structure of cubosomes, hexosomes and emulsified micro-emulsions was investigated by SAXS. We showed that the phase borders may be shifted due to the presence of the kappa-carrageenan network, which alter the internal nanostructure of the droplets. This can induce a transformation from emulsified micro-emulsions to micellar cubosomes. In the hexagonal case, the lattice parameters of the hexosomes are slightly modified.

Confinement of DNA in water-in-oil microemulsions.

The study of systems that allow DNA condensation in confined environments is an important task in producing cell-mimicking microreactors capable of biochemical activities. The water droplets formed in water-in-oil emulsions are potentially good candidates for such microcompartments. The anionic surfactant AOT was used here to stabilize the droplets. We have studied in detail the DNA distribution and the structural modifications of these microemulsion drops by varying the concentration and molecular weight of DNA and using various techniques such as light, X-ray, and neutron scattering, electrical conductivity, and surface tension. DNA induces the formation of large drops into which it is internalized. The size of these drops depends on the amount of DNA dissolved in water as well as on its molecular weight. The local DNA concentration is very high (>100 mg/mL). The large drops coexist with small empty drops (not containing DNA), similar to those found in the DNA-free microemulsion.

Preparation of highly concentrated nanostructured dispersions of controlled size.

This article presents the use of a shearing procedure for the preparation of stable nanostructured dispersions of lipid mesophases. This new application of the shearing technique is compared with the well-established ultrasonication method for the emulsification of these mesophases in water in terms of particle size, particle size distribution and available concentration range. With a laboratory-built shear device based on a Couette cell, it was possible to produce high quantities of internally self-assembled emulsion particles of controlled size at concentrated hydrophobic phase contents (phi(o)) of up to 70 wt%. The concentration limit of 70 wt% could be reached however, the maximum attainable concentration depended on the internal structure type of the particles. The limit was thus easily attained for emulsified microemulsions (EME) as well as for the emulsified inverse hexagonal phase (H(2)), whereas it was found to be lower for emulsified discontinuous (Fd3m) and bicontinuous (Pn3m) cubic phases. Moreover, by shearing, it was possible to keep the size of the particles relatively constant when increasing phi(o), whereas the particle size significantly increased with phi(o) when ultrasonication was employed. By means of ultrasonication, the hydrodynamic radius of the particles could be tuned linearly between 85 to 180 nm as a function of phi(o) up to a maximum of 20 to 30 wt%. Below the maximum concentration limit, particles displayed a well-controlled size.

Carbon nanotubes as structural nanofibers for hyaluronic acid hydrogel scaffolds.

We have successfully dispersed functionalized single-walled carbon nanotubes (SWNTs) within hyaluronic acid-water solutions. Hybrid hyaluronic acid (HA) hydrogels with SWNTs were then formed by cross-linking with divinyl sulfone. We have found a considerable change in the morphology of the lyophilized hybrid hydrogels compared to HA hydrogels. The high water uptake capacity, an important property of HA hydrogels, remained almost unchanged after 2 wt % SWNT (vs HA) incorporation, despite a dramatic enhancement in the dynamic mechanical properties of the hybrid hydrogels compared to native ones. We have found a 300% enhancement in the storage modulus of hybrid hydrogel with only 2 wt % of SWNTs vs HA (0.06 wt % vs total weight including water content). This apparent contradiction can be explained by a networking effect between SWNTs, mediated by HA chains. As in biological tissue, HA plays a dual role of matrix and linker for the rigid reinforcing nanofibers.

X-ray diffraction study of the structure of carboxymethylcellulose-cationic surfactant complexes.

We have investigated dilute aqueous solutions of an anionic polymer (carboxymethylcellulose) mixed with cationic surfactants of different chain lengths (dodecyl to octadecyl trimethylammonium bromides: DTAB, TTAB, CTAB and OTAB). The structures of the concentrated phases formed above the precipitation threshold were studied by X-ray diffraction. Different body-centred cubic structures with space groups Pm3n were observed in the presence of surfactant with a short aliphatic chain (DTAB), despite the fact that the polymer persistence length is comparable to the repeat distance of the structure (5 nm). For larger surfactant chain lengths (TTAB and CTAB), the structure of the precipitates can be either cubic (Pm3n) or 2D hexagonal depending on the initial surfactant and polymer concentrations. For still larger chain length (OTAB), the structure becomes lamellar. This structural evolution from micellar cubic towards 2D hexagonal and lamellar is attributed to the decrease of the local curvature of the surfactant aggregates, as observed for flexible synthetic polymers and short DNA fragments under similar conditions. Furthermore, the structure of the bulk complexes formed just below the precipitation threshold anticipates the structure seen in the precipitated phases.

Structural and rheological investigation of Fd3m inverse micellar cubic phases.

In the present study we demonstrate that a bulk inverse micellar cubic phase of Fd3m structure can be obtained by adding a hydrophobic component, such as the food-grade limonene, to the binary system monolinolein/water in a well-defined composition. The Fd3m structure studied in this work had a very slow kinetics of formation, as a consequence of partitioning of water into two types of micelle populations with different sizes. The Fd3m structure formed at a ratio of limonene oil to total lipids of alpha = 0.4 is stable in the bulk up to a maximum hydration of 12.68 wt % water, beyond which it starts to coexist with dispersed water. At full hydration, by combining small-angle X-ray scattering and available topological models, the inverse micellar cubic phase of Fd3m structure was shown to be formed by 16 small micelles and 8 larger micelles per cubic lattice cell (Q227 group), with radii of the micellar polar cores ranging between 1 and 3 nm and 149-168 monolinolein molecules per micelle depending on the water content. The temperature dependence of the structural and rheological properties of the Fd3m mesophase was investigated using SAXS, rheology, and turbidimetry. It appeared that the Fd3m phase underwent crystallization below 18 degrees C and began melting in an inverse microemulsion (L2 phase) coexisting with water above 28.5 degrees C with complete melting obtained at 40-45 degrees C, as evidenced by SAXS and rheology. Macroscopic phase separation between the L2 phase and excess water was observed with time at higher temperatures. The investigation of the viscoelastic properties of the Fd3m inverse discrete micellar cubic phase revealed a rheological signature similar to that of the bicontinuous cubic phases Pn3m and Ia3d observed in homologous binary systems. However, the Fd3m phase presented a complex set of slower relaxation mechanisms leading to a shift by 1 order of magnitude of the dominant relaxation times and whole relaxation spectrum, as compared to those of inverse bicontinuous cubic phases. These findings have been tentatively explained by (i) the multiple relaxation of micelles upon deformation, (ii) the small hydration level of the Fd3m phase, and (iii) the low temperature at which this phase can be observed.

Determination of water content in internally self-assembled monoglyceride-based dispersions from the bulk phase.

We determined the water intake of internally structured oil-loaded monoglyceride-based dispersions. This was possible through small-angle X-ray scattering (SAXS) experiments on the corresponding bulk mesophases because the structural parameters in full hydration conditions are identical to those of the dispersed particles. From low water contents to full hydration, the bulk phases depend strongly on the amount of oil. At room temperature in excess water and with increasing oil concentration, successive bicontinuous cubic, reverse hexagonal, micellar cubic, and inverse micellar-type isotropic fluid phases are found. The solubilized water is determined as a function of the oil content for each phase, and it is found to range from 5-33 wt %.

Critical aggregation concentration in mixed solutions of anionic polyelectrolytes and cationic surfactants.

We have examined the polymer/surfactant interaction in mixed aqueous solutions of cationic surfactants and anionic polyelectrolytes combining various techniques: tensiometry, potentiometry with surfactant-selective electrodes, and viscosimetry. We have investigated the role of varying polymer charge density, polymer concentration, surfactant chain length, polymer backbone rigidity, and molecular weight on the critical aggregation concentration (Cac) of mixed polymer/surfactant systems. The Cac of these systems, estimated from tensiometry and potentiometry, is found to be in close agreement. Different Cac variations with polymer charge density and surfactant chain length were observed with polymers having persistence lengths either smaller or larger than surfactant micelle size, which might reflect a different type of molecular organization in the polymer/surfactant complexes. The surfactant concentration at which the viscosity starts to decrease sharply is different from the Cac and probably reflects the polymer chain shrinkage due to surfactant binding.