Liquid micellar discontinuous cubic mesophase from ternary monoolein/ethanol/water mixtures

Self-nanoemulsifying drug delivery system (SNEDDS) as nano-carrier framework for permeability modulating approaches of BCS class III drug

The purpose of this review is to focus on the Self-Nanoemulsifying Drug Delivery System (SNEDDS) as an effective nanocarrier framework for permeability modulating approaches (PMA) of BCS class-III drugs and its challenges. Present review updates the recent trends in the SNEDDS research where it was employed as a cargo carrier for PMA and challenges. Patient compliance, ease of administration and non-invasiveness mode are non-trivial aspects in the oral administration of drugs. However, low aqueous solubility and impaired permeability are two prominent challenges resulting poor absorption of a drug. SNEDDS emerged as a dual nano-carrier system to enable nanodispersion of PMA via e.g. ion-pairing, phospholipid-complex, surfactant-drug interaction, loading of non-ionizable, free drug bases etc. These PMAs are embedded within the lipid phase of SNEDDS to produce nanosizing, enhancing nano-dispersibility via micellization/solubilization mechanism owing to its ternary components. Review highlights different PMAs employed in bioavailability enhancement of BCS class-III. It covers excipients employed in SNEDDS-loaded PMA, strategies for the hydrophobic transformation of water-soluble drugs for BCS class-III drugs. SNEDDS as a nano-cargo system for PMAs significantly modifies the bioavailability of BCS class-III drugs. SNEDDS is an isotropic-mixture of oil, surfactant:co-surfactant offers multipoint access to PMA loading and produces nano-dispersion in aqueous-medium.

Perspective use of bio-adhesive liquid crystals as ophthalmic drug delivery systems

The success of many drugs in ophthalmic treatments is hindered by their physico-chemical properties and the limited precorneal retention time. Here, lyotropic liquid crystals are proposed as a new ophthalmic drug delivery system. Acyclovir was chosen as model drug for its solubility and its controlled release from cubic phase was achieved. We demonstrated the effortless application of lamellar phase on corneal surface and its ability to convert itself in cubic phase in situ. While the complex viscosity of lamellar phase was affected by temperature (5.1 ± 1.4 kPa·s at 25 °C and 0.12 ± 0.001 Pa·s at 35 °C, respectively), the cubic phase shown no changes in viscosity values and shear thinning behaviour at both temperatures and even in presence of the drug The degradation kinetic of drug-loaded cubic phase was slightly slower than the empty formulation, recording 27.92 ± 1.43% and 33.30 ± 3.11% of weight loss after 8 h. Ex vivo studies conducted on porcine eyeballs and isolated cornea confirmed the instantaneous transition to cubic phase, its ability to resist to gravity force, and forced dripping of simulated tear fluid. Histopathological investigation showed how treated cornea did not report changes in epithelial and stroma structures. In summary, lyotropic liquid crystals could represent an advantageous ophthalmic drug delivery system.

Spatially and time-resolved SAXS for monitoring dynamic structural transitions during in situ generation of non-lamellar liquid crystalline phases in biologically relevant media

Formation of high viscous inverse lyotropic liquid crystalline phases in situ upon exposure of low viscous drug-loaded lipid preformulations to synovial fluid provides a promising approach for design of depot formulations for intra-articular drug delivery. Rational formulation design relies on a fundamental understanding of the synovial fluid-mediated dynamic structural transitions occurring at the administration site. At conditions mimicking the in vivo situation, we investigated in real-time such transitions at multiple positions by synchrotron small-angle X-ray scattering (SAXS) combined with an injection-cell. An injectable diclofenac-loaded quaternary preformulation consisting of 72/8/10/10% (w/w) glycerol monooleate/1,2-dioleoyl-glycero-3-phospho-rac-(1-glycerol)/ethanol/water was injected into hyaluronic acid solution or synovial fluid. A fast generation of a coherent drug depot of inverse bicontinuous Im3m and Pn3m cubic phases was observed. Through construction of 2D spatial maps from measurements performed 60 min after injection of the preformulation, it was possible to differentiate liquid crystalline rich- and excess hyaluronic acid solution- or synovial fluid-rich regimes. Synchrotron SAXS findings confirmed that the exposure of the preformulation to the media leads to alterations in structural features in position- and time-dependent manners. Effects of biologically relevant medium composition on the structural features, and implications for development of formulations with sustained drug release properties are highlighted.

Innovative Mucoadhesive Precursor of Liquid Crystalline System Loading Anti-Gellatinolytic Peptide for Topical Treatment of Oral Cancer

Current researches report an actual benefit of a treatment for oral cancer via inhibition of proteolytic matrix metallopro-teinases (MPP) with a peptide drug, called CTT1. However, peptides present poor oral bioavailability. Topical administration on oral mucosa avoids its passage through the gastrointestinal tract and the first-pass liver metabolism, but the barrier function of the oral mucosa can impair the permeation and retention of CTT1. The objective of this study is to incorporate CTT1 into a mucoadhesive precursor of liquid crystalline system (PLCS) as an interesting strategy for the topical treatment of oral cancer. PLCS consisting of oleic acid, ethoxylated 20 and propoxylated cetyl alcohol 5, polyethyleneimine (P)-associated chitosan (C) dispersion and CTT1 (FPC-CTT1) was developed and characterized by polarized light microscopy (PLM) and small-angle X-ray scattering (SAXS). In vitro permeation and retention across esophageal mucosa, In vitro cytotoxicity towards tongue squamous cell carcinoma cells, and in vivo evaluation of vascular changes using the chick embryo chorioallantoic membrane (CAM) model were performed. PLM and SAXS showed that FPC-CTT1acted as PLCS, because it formed a lamellar liquid crystalline system after the addition of artificial saliva. FPC-CTT1increased approximately 2-fold the flux of permeation and 3-fold the retention of CTT1 on the porcine esophageal mucosa. CTT1 does not affect cell viability. CAM tests showed that FPC preserved the blood vessels and it can be a safe formulation. These findings encourage the use of the FPC-CTT1 for topical treatment of oral cancer.

Kinetics of active water/ethanol Janus droplets

Droplets made of a water/ethanol mixture spontaneously self-propel in an oil/surfactant solution and, depending on the initial ethanol concentration at the time of production, may evolve in up to three stages. Upon self-propulsion the droplets absorb surfactant molecules during their continuous motion in the oily phase. In combination with the continuous loss of ethanol this mass exchange with the ambient phase may lead to a spontaneous phase separation of the water/ethanol mixture, and eventually to the formation of characteristic Janus droplets. Supported by experimental evidence, we propose a simple model that is able to explain the propulsion velocity and its scaling with the droplet radius in the last stage of the droplet evolution.

Transdermal metformin hydrochloride-loaded cubic phases: in silico formulation optimization, preparation, properties, and application for local treatment of melanoma

Metformin hydrochloride (Met) is commonly used for antidiabetic therapy though its antimelanoma action is also reported. Conventional oral administration method of Met is not appropriate for therapy of melanoma because of large dose, adverse reactions, and low efficiency. Here, a transdermal Met-loaded cubic phase was developed for local treatment of melanoma. In silico formulation optimization of the cubic phases was done, and the corresponding formulations were prepared and characterized. The optimized formulations were screened based on the stable microstructure and proper fluidity. Highly efficient mouse skin permeability of Met was found with the cubic phases compared to Met solutions. High antimelanoma effect of transdermal Met-loaded cubic phases also was shown by the significant decrease of tumor volume and the improvement of melanoma cell apoptosis on the B16 melanoma mice. Met-loaded cubic phases are a promising topically applied medication for local therapies of melanoma.

A liquid crystalline precursor incorporating chlorhexidine acetate and silver nanoparticles for root canal disinfection

Lyotropic liquid crystals (LLC) have received increasing attention as a drug delivery system. In this study, a novel intra-canal disinfectant based on the glycerol monooleate (GMO) LLC precursor incorporation with chlorhexidine (CHX) and silver nanoparticles (Ag-NPs) was designed and evaluated. The LLC precursor with excellent fluidity was able to penetrate deeply into the complex tiny collateral branch root canals. The transformation of cubic LLC in root canals upon coming into contact with water provided long-lasting disinfection against multidrug-resistant bacteria to avoid the endodontic reinfection and follow-up visits. The GMO-ethanol-water (48% : 12% : 40%, w/w) formulation containing 0.5% CHX and 0.02% Ag-NPs was selected for further studies. The low viscosity of the precursor presented excellent injectability and flowabilities. From the in vitro release test, the release behaviours were found to be influenced by CHX and Ag-NP contents, allowing the optimized precursor to obtain a 28-day release profile. The CHX-Ag-NP containing LLC precursor exhibited an excellent and sustained sterilization effect on Enterococcus faecalis for more than one month with a bacterial inactivation rate of ≥98.5%, which was far more than the minimum clinical requirement (7 days). Furthermore, no in vitro toxicity was observed in the cytotoxicity evaluation. The CHX-Ag-NP containing LLC precursor was proved to be a promising intra-canal disinfectant in our study.

Polyethyleneimine and Chitosan Polymer-Based Mucoadhesive Liquid Crystalline Systems Intended for Buccal Drug Delivery

The buccal mucosa is accessible, shows rapid repair, has an excellent blood supply, and shows the absence of the first-pass effect, which makes it a very attractive drug delivery route. However, this route has limitations, mainly due to the continuous secretion of saliva (0.5 to 2 L/day), which may lead to dilution, possible ingestion, and unintentional removal of the active drug. Nanotechnology-based drug delivery systems, such as liquid crystalline systems (LCSs), can increase drug permeation through the mucosa and thereby improve drug delivery. This study aimed at developing and characterizing the mechanical, rheological, and mucoadhesive properties of four liquid crystalline precursor systems (LCPSs) composed of four different aqueous phases (i) water (FW), (ii) chitosan (FC), (iii) polyethyleneimine (FP), or (iv) both polymers (FPC); oleic acid was used as the oil phase, and ethoxylated and propoxylated cetyl alcohol was used as the surfactant. Polarized light microscopy and small-angle X-ray scattering indicated that all LCPSs formed liquid crystalline states after incorporation of saliva. Rheological, texture, and mucoadhesive assays showed that FPC had the most suitable characteristics for buccal application. In vitro release study showed that FPC could act as a controlled drug delivery system. Finally, based on in vitro cytotoxicity data, FPC is a safe buccal drug delivery system for the treatment of several buccal diseases.

Lipid polymorphism in lyotropic liquid crystals for triggered release of bioactives

In this review we present recent progress on lyotropic liquid crystals (LLC) as delivery vehicles for cosmetoceuticals, nutraceuticals, and drugs. LLC have been known for decades and their potential as delivery vehicles is well recognized. Yet, the two major mesophases, reverse hexagonal (H(II)) and bicontinuous cubic (primitive, gyroid, and diamond), are relatively hard gels with very slow release kinetics of the bioactives. In recent years a discontinuous cubic micellar mesophase (Q(L)) was characterized and studied, showing significant potential as a delivery vehicle. In addition, the H(II) mesophase formed could be much more fluid and produced at room temperature. Recent studies concentrated on establishing methods to evaluate solubilization capacity and relationship between the diameter and length of the cylinders and the nature of the solubilizates. Special attention was given to finding methods to target the vehicles to the lumen and to trigger the release of the bioactives. This review summarizes the efforts of our group along with work by numerous other scientists in this area. All these efforts suggest that the lyotropic mesophases and the corresponding dispersed soft particles (cubosomes, hexosomes, micellosomes) are now more than ever ready to become drug delivery vehicles for transport across the skin and the gut.

Food volatile compounds facilitating HII mesophase formation: solubilization and stability

Four lipophilic food volatile molecules of different chemical characteristics, phenylacetaldehyde, 2,6-dimethyl-5-heptenal, linalool, and trans-4-decenal, were solubilized into binary mixtures of monoolein/water, facilitating the formation of reverse hexagonal (H(II)) mesophases at room temperature without the need of solvents or triglycerides. Some of the flavor compounds are important building blocks of the hexagonal mesostructure, preventing phase transition with aging. The solubilization loads were relatively high: 12.6, 10.0, 12.6, and 10.0 wt % for phenylacetaldehyde, 2,6-dimethyl-5-heptenal, linalool, and trans-4-decenal, respectively. Phenylacetaldehyde formed mixtures of lamellar and cubic phases. Linalool, 2,6-dimethyl-5-heptenal, and trans-4-decenal induced structural shift from lamellar directly to H(II) mesophase, remaining stable at room temperature. Lattice parameters were found to increase with water content and to decrease with temperature and/or food volatile content. trans-4-Decenal produces more stable H(II) mesophase compared to linalool-loaded mesophase. At 40-60 °C, depending on the chemical structure and on the solubilization location of the food volatile compounds, the H(II) mesophase transforms to isotropic micellar phase, facilitating the release of the food volatile compounds. Molecular interactions suggest the existence of two consecutive stages in the solubilization process.

Solubilization of hydrophobic guest molecules in the monoolein discontinuous QL cubic mesophase and its soft nanoparticles

Hydrophobic bioactive guest molecules were solubilized in the discontinuous cubic mesophase (QL) of monoolein. Their effects on the mesophase structure and thermal behavior, and on the formation of soft nanoparticles upon dispersion of the bulk mesophase were studied. Four additives were analyzed. They were classified into two types based on their presumed location within the lipid bilayer and their influence on the phase behavior and structure. Differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), polarized light microscopy, cryogenic-transmission electron microscopy (cryo-TEM), and dynamic light scattering (DLS) were used for the analysis. We found that carbamazepine and cholesterol (type I molecules) likely localize in the hydrophobic domains, but close to the hydrophobic-hydrophilic region. They induce strong perturbation to the mesophase packing by influencing both the order of the lipid acyl chains and interactions between lipid headgroups. This results in significant reduction of the phase transition enthalpy, and phase separation into lamellar and cubic mesophases above the maximum loading capacity. The inclusion of type I molecules in the mesophase also prevents the formation of soft nanoparticles with long-range internal order upon dispersion. In their presence, only vesicles or sponge-like nanoparticles form. Phytosterols and coenzyme Q10 (type II molecules) present only moderate effects. These molecules reside in the hydrophobic domains, where they cannot alter the lipid curvature or transform the QL mesophase into another phase. Therefore, above maximum loading, excess solubilizate precipitates in crystal forms. Moreover, when type II-loaded QL is dispersed, nanoparticles with long-range order and cubic symmetry (i.e., cubosomes) do form. A model for the growth of the ordered nanoparticles was developed from a series of intermediate structures identified by cryo-TEM. It proposes the development of the internal structure by fusion events between bilayer segments.

Effect of sodium diclofenac loads on mesophase components and structure

We studied the effect of a model electrolytic drug on intermolecular interactions, conformational changes, and phase transitions in structured discontinuous cubic QL lyotropic liquid crystals. These changes were due to competition with hydration of the lipid headgroups. Structural changes of the phase induced by solubilization loads of sodium diclofenac (Na-DFC) were investigated by directly observing the water, ethanol, and Na-DFC components of the resulting phases using 2H and 23Na NMR. Na-DFC interacted with the surfactant glycerol monoolein (GMO) at the interface while interfering with the mesophase curvature and also competed with hydration of the surfactant headgroups. Increasing quantities of solubilized Na-DFC promoted phase transitions from cubic phase (discontinuous (QL) and bicontinuous (Q)) into lamellar structures and subsequently into a disordered lamellar phase. Quadrupolar coupling of deuterated ethanol by 2H NMR showed that it is located near the headgroups of the lipid and apparently is hydrogen bonded to the GMO headgroups. A phase transition between two lamellar phases (L alpha to L alpha*) was seen by 23Na NMR of Na-DFC at a concentration where the characteristics of the drug change from kosmotropic to chaotropic. These findings show that loads of solubilized drug may affect the structure of its vehicle and, as a result, its transport across skin-blood barriers. The structural changes of the mesophase may also aid controlled drug delivery.