Bulk and dispersed aqueous behaviour of an endogenous lipid, selachyl alcohol: Effect of Tween 80 and Pluronic F127 on nanostructure

Formulating plant-based hexosomes for the sustained delivery of food proteins

Hexosomes (HEXs) are nanoparticles formed by dispersing a lipid reverse hexagonal phase in water. Although they have attracted a great interest in the development of delivery systems, few lipids have been employed in their production. Galactolipids, especially monogalactosyldiacylglycerol (MGDG), are the main lipid constituents of plants and can be obtained from vegetal biomass, making them good candidates for the obtention of HEXs. In this work, the aqueous phase behavior of MGDG from sweet potato leaves was investigated and the resulting hexagonal phase was downsized into HEXs with the aid of stabilizer decaglycerol monooleate (DGMO), a food-grade emulsifier from vegetable oils. The nanoparticles presented enhanced long-term colloidal stability in different storage conditions and their inner liquid crystalline structure could be tuned by the amount of DGMO employed. Moreover, by adding sodium oleate (NaO) HEXs displayed enhanced loading efficiency of lysozyme, an edible protein with biological properties. Finally, the sustained release of incorporated protein could be finely tuned by changing HEXs composition. Collectively, the results demonstrate, for the first time, the viability of producing biobased, renewable sourced galactolipid hexosomes with potential applications in the development of functional foods, also contributing to a sustainable management of biomass waste.

Compartmentalised enzyme-induced phase transformations in self-assembling lipid systems

HYPOTHESIS

Understanding the digestion of lipid-based pharmaceutical formulations and food systems is necessary for optimising drug and nutrient delivery and has been extensively studied in bulk emulsion systems using the pH-stat method [1]. However, this approach is not suitable for investigation of individual lipid droplets, in particular the interface where the lipase acts. Microfluidic approaches to study digestion at lipid-water interfaces using droplet trapping have been proposed, however the aqueous phase in that case washes over the interface presenting uncertainty over the stoichiometry of interactions [2]. The internal interface of a Janus-like droplet, containing distinct aqueous and lipid compartments, mimics the interface of a lipid droplet in aqueous solution with controlled stoichiometry [3]. Hence, it was hypothesised that the internal interface of Janus droplets can offer a precise way to study the enzymatic digestion of lipids formulations.

EXPERIMENTS

Using microfluidic methods, Janus-like droplets were formed by coalescing emulsion droplets containing lipid formulation and pancreatic lipase. Polarised light microscopy (PLM) and in-situ small-angle X-ray scattering (SAXS) were used to investigate the droplets.

FINDINGS

PLM revealed the growth of an aligned inverse hexagonal phase (H2), and with SAXS showed that this phase transformation and alignment resulted from enzymatic digestion. A subsequent partial transformation from H2 to inverse bicontinuous cubic phase occurred when simulated intestinal fluid was used instead of Tris buffer. Suggesting that phospholipids and bile salts could diffuse across the internal interface to locally affect their surroundings.

Vilazodone-phospholipid mixed micelles for enhancing oral bioavailability and reducing pharmacokinetic variability between fed and fasted states

Despite the effectiveness and high tolerability of vilazodone (VLZ) as an antidepressant, its use is still limited due to its poor solubility and food dependent absorption. This study aims to load VLZ-phospholipid complex into self-assembled micelles forming VLZ-PL mixed micelles (VLZ-PL-MM), that can enhance VLZ solubility, improve its bioavailability and reduce the pharmacokinetic variability between the fed and fasting conditions. The effect of the surfactant type and concentration was assessed using four different non-ionic surfactants (Brij 58, Tween 80, Labrasol and Pluronic F127) in four different weight ratios between the drug-complex and surfactant (1:0.5, 1:1, 1:2 and 1:3 w/w). Two VLZ-PL-MM formulae prepared using Brij 58 and Labrasol in 1:3 w/w ratio were selected as optimised ones since they have the highest encapsulation efficiency (100.83 and 93.87%, respectively), a particle size below 250 nm (206.73 and 221.33 nm, respectively) and negative zeta potential values (-29.63, -17.20 mV, respectively). Lyophilisation of these formulations using 3% sucrose was successful with no statistical changes in particle size and zeta potential upon rehydration. Both formulations elicited faster and higher in-vitro drug release profiles compared to the pure drug and the marketed tablet. In addition, both selected formulae improved ex-vivo permeation across rabbit intestinal membrane compared to the pure drug and the marketed tablet, with marked superiority of the one prepared using Brij 58. The results of the in vivo study in male albino rabbits revealed similar AUC_0-24 values after the oral administration of the best achieved VLZ-PL-MM system under fed and fasting conditions (769.89 and 741.55 ng.h mL^-1, respectively). On the other hand, the marketed product showed significantly lower values of the AUC_0-24 relative to the VLZ-PL-MM system and there was a marked enhancement of absorption of drug from the marketed product in presence of food (244.24 and 174.96 ng.h mL^-1 under fed and fasting conditions, respectively. In addition, VLZ concentrations in the brain after 24 hours obtained from the selected VLZ-PL-MM were significantly higher than those obtained from marketed tablet under fed and fasting conditions. Thus, the phospholipid mixed micelle formulation enhances the oral bioavailability of the poorly soluble drug and reduces the pharmacokinetic variability between fasting and fed conditions.

Cubosomes as an emerging platform for drug delivery: a state-of-the-art review

Lipid-based drug delivery nanoparticles, including non-lamellar type, mesophasic nanostructured materials of lyotropic liquid crystals (LLCs), have been a topic of interest for researchers for their applications in encapsulation of drugs...

"Plurethosome" as Vesicular System for Cutaneous Administration of Mangiferin: Formulative Study and 3D Skin Tissue Evaluation

Human skin is dramatically exposed to toxic pollutants such as ozone. To counteract the skin disorders induced by the air pollution, natural antioxidants such as mangiferin could be employed. A formulative study for the development of vesicular systems for mangiferin based on phosphatidylcholine and the block copolymer pluronic is described. Plurethosomes were designed for mangiferin transdermal administration and compared to ethosome and transethosome. Particularly, the effect of vesicle composition was investigated on size distribution, inner and outer morphology by photon correlation spectroscopy, small angle X-ray diffraction, and transmission electron microscopy. The potential of selected formulations as vehicles for mangiferin was studied, evaluating encapsulation efficiency and in vitro diffusion parameters by Franz cells. The mangiferin antioxidant capacity was verified by the 2,2-diphenyl-1-picrylhydrazyl assay. Vesicle size spanned between 200 and 550 nm, being influenced by phosphatidylcholine concentration and by the presence of polysorbate or pluronic. The vesicle supramolecular structure was multilamellar in the case of ethosome or plurethosome and unilamellar in the case of transethosome. A linear diffusion of mangiferin in the case of ethosome and transethosomes and a biphasic profile in the case of plurethosomes indicated the capability of multilamellar vesicles to retain the drug more efficaciously than the unilamellar ones. The antioxidant and anti-inflammatory potential effect of mangiferin against pollutants was evaluated on 3D human skin models exposed to O3. The protective effect exerted by plurethosomes and transethosomes suggests their possible application to enhance the cutaneous antioxidant defense status.

Comparison of cubosomes and hexosomes for the delivery of phenytoin to the brain

The ability to formulate cubosomes and hexosomes with a single lipid by changing only the colloidal stabiliser presents a unique opportunity to directly compare the biological performance of these uniquely structured nanoparticles. This was explored here via the encapsulation and brain delivery of a model anti-seizure drug, phenytoin, in selachyl alcohol cubosomes and hexosomes. Nanoparticles were prepared with Pluronic® F127 or Tween 80® as the stabiliser and characterised. The internal nanostructure of nanoparticles shifted from hexosomes when using Pluronic® F127 as the stabiliser to cubosomes when using Tween 80® and was conserved following loading of phenytoin, with high encapsulation efficiencies (>97%) in both particle type. Cytotoxicity towards brain endothelial cells using the hCMEC/D3 line was comparable regardless of stabiliser type. Finally, in vivo brain delivery of phenytoin encapsulated in cubosomes and hexosomes after intravenous administration to rats was studied over a period of 60 min, showing cubosomes to be superior to hexosomes, both in terms of brain concentrations and brain to plasma ratio. While the role of stabiliser and/or internal nanostructure remains to be conclusively determined, this study is the first in vivo comparison of cubosomes and hexosomes for the delivery of a therapeutic drug molecule across the BBB and into the brain.

Cubosomes enhance drug permeability across the blood-brain barrier in zebrafish

The potential of cubosomes to improve delivery of incorporated cargo to the brain was explored in zebrafish. Cubosomes were formulated with one of three stabilisers, Pluronic F68, Pluronic F127 or Tween 80, with the hypothesis that coating with Tween 80 will enable brain targeting of cubosomes as has been previously shown for polymeric nanoparticles. The physiochemical properties and the ability of the cubosomes to facilitate delivery of the model drug lissamine rhodamine (RhoB) into the brain was investigated. Distribution of cubosomes in the midbrain was also investigated by ultrastructural analysis via incorporation of octanethiol-functionalized gold nanoparticles. Cubosomes were typically 165-195 nm in size with a Pn3m (Pluronics) or Im3m (Tween 80) cubic phase internal structure. Cubosomes were injected intravenously into zebrafish larvae (12-14 days post fertilization) and the concentration of RhoB in the midbrain was determined by quantifying its fluorescence intensity. Uptake of RhoB was significantly greater in larvae injected with Tween 80 stabilized cubosomes as compared to a control suspension of RhoB or cubosomes stabilized with Pluronics. Collectively, we show for the first time that cubosomes can be functionalized to deliver drug across the BBB, offering new opportunities to overcome drug delivery issues across this formidable biological barrier.

Development of a Liquid Crystal Formulation that Can Penetrate the Stratum Corneum for Intradermal Delivery of Small Interfering RNA

Topical delivery of small interfering RNA (siRNA) can be an attractive method for the treatment of skin diseases and improving the quality of life of patients. However, it is difficult for siRNA to pass through the two major barriers of the skin: the stratum corneum (SC) and tight junctions. We have previously reported that atopic dermatitis of skin without the SC can be efficiently treated by the intradermal administration of trans-activator of transcription (Tat) peptide and AT1002 (tight junction opening peptide). However, novel drug delivery systems are needed for effective SC penetration. Therefore, in the present study, we aimed to develop a lyotropic liquid crystalline (LC) system containing Tat and AT1002 for effective siRNA penetration through the SC. An LC formulation was prepared using selachyl alcohol and purified water, and its skin penetration ability was evaluated. No fluorescence was observed in mouse skin treated with a siRNA solution, as there was no intradermal localization of siRNA from naked siRNA. However, intradermal delivery of siRNA was remarkable and extensive with the LC formulation containing both Tat and AT1002. Semiquantitative analysis by brightness measurement revealed that the LC formulation containing both Tat and AT1002 had significantly enhanced intact skin permeability than other formulations. These results show that the functional peptides in the LC formulation increased SC penetration and intradermal delivery in the healthy skin. Therefore, this novel LC system may be useful in the treatment of various skin diseases.

Hexosomes as Efficient Platforms for Possible Fluoxetine Hydrochloride Repurposing with Improved Cytotoxicity against HepG2 Cells

The aim of this study was to investigate the feasibility of hexosomes (HEXs) as competent platforms for fluoxetine hydrochloride (FH) repurposing against HepG2 hepatocellular carcinoma. Different FH-loaded HEX formulations were prepared and optimized by the hot emulsification method. The HEX features such as particle size, ζ potential, and drug entrapment efficiency (EE%) can be tailored by tuning HEX components and fabrication conditions. The composition of the optimized FH hexosome (OFH-HEX) was composed of 3.1, 1.4, 0.5, 0.2, and 94.8% for glyceryl monooleate, oleic acid, pluronic F127, FH, and deionized water, respectively. The anionic OFH-HEX with a particle size of 145.5 ± 2.5 nm and drug EE% of 45.4 ± 1.2% was able to prolong the in vitro FH release, where only 19.5 ± 2.3% released in phosphate-buffered saline (PBS) pH 7.4 after 24 h. Contrarily, HEX rapidly released FH in acetate buffer pH 5.5 and achieved a 90.5 ± 4.7% release after 24 h. The obtained HEX showed an improved cellular internalization in a time-dependent manner and enhanced the cytotoxicity (2-fold higher than FH solution). The current study suggests the potential of FH-HEX as a possible anticancer agent against hepatocellular carcinoma.

Sustained absorption of delamanid from lipid-based formulations as a path to reduced frequency of administration

Delamanid is a poorly water-soluble drug currently being used for the treatment of tuberculosis. The high frequency of dosing leads to poor adherence for patients who live in lower economic and nomadic populations. Non-digestible self-assembling lipids as a formulation approach for poorly water-soluble drugs have previously been shown to extend the window of absorption through gastric retention. We hypothesise that this approach could lead to the reduction of dosing frequency for delamanid and thereby has potential to improve adherence. Formulations of delamanid were prepared in selachyl alcohol and phytantriol as non-digestible self-assembling lipid vehicles, and their behaviour was compared with reconstituted milk powder, as a digestible lipid-based formulation, and an aqueous suspension. The self-assembly of selachyl alcohol and phytantriol in aqueous media in the presence of delamanid was studied using small angle X-ray scattering and produced the inverse hexagonal (H₂) and inverse bicontinuous cubic (V₂) liquid crystal structures, respectively. The times at which maximum delamanid levels in plasma were observed (T_max) after oral administration of the phytantriol, selachyl alcohol and reconstituted milk powder formulations of delamanid to rats were 27 ± 3, 20 ± 4 and 6.5 ± 1.0 h, respectively, compared with the aqueous suspension formulation with a T_max of 3.4 ± 1 h, which confirms the hypothesis of an extended duration of absorption after administration in non-digestible self-assembling lipids. The digestion products of the triglycerides in the milk formulation increased the solubilisation of delamanid in the gastrointestinal tract, leading to an increase in exposure compared with the aqueous suspension formulation but did not significantly extend T_max. Overall, the non-digestible nanostructured lipid formulations extended the duration of absorption of delamanid well beyond that from milk or suspension formulations.

Steric stabilisers govern the colloidal and chemical stability but not in vitro cellular toxicity of linoleoylethanolamide cubosomes

Linoleoylethanolamide (LEA) is an endogenous lipid with remarkable neuromodulatory properties. However, its therapeutic potential is limited by rapid clearance in vivo, targetability and solubility. This study aimed to formulate LEA into liquid crystalline nanoparticles (cubosomes) as a strategy to address the aforementioned challenges. The influence of three different steric stabilisers: Tween 80 and Pluronic F68, both of which have the potential to interact with receptors expressed at the blood-brain barrier and Pluronic F127 as a control, on colloidal stability, internal structure, chemical stability and cytotoxicity of the dispersions were investigated. We found that for effective stabilization of LEA dispersions, a higher concentration of Tween 80 was required compared to Pluronics. Freshly prepared dispersions showed mean particle size of <250 nm and low PDIs (<0.2), with an Im3m type cubic structure but with different lattice parameters. Upon storage at ambient temperature for a week, increased mean particle size and PDI, with a significant reduction in the concentration of LEA was observed in Tween 80-stabilised dispersions. Greater than 80% cell viability was observed at concentrations of up to 20 μg/mL LEA in the presence of all three stabilisers. Collectively, our results suggest that the stabiliser type influences colloidal and chemical stability but not cytotoxicity of LEA cubosomes. This study highlights the potential of endogenous bioactive lipids to be utilized as core cubosome forming lipids with the view to improving their solubility, rapid clearance and targetability to enable delivery of these bioactive molecules to the brain.

Preparation and characterization of β-casein stabilized lipopeptide lyotropic liquid crystal nanoparticles for delivery of doxorubicin

A kind of lyotropic liquid crystal nanoparticle (LLC NPs) has been designed and prepared. LLC NPs are dSMO/OA/β-casein/water quaternary systems, and their cubic or hexagonal microstructures have been characterized by cryogenic transmission electron microscopy (cryo-TEM) and small angle X-ray scattering (SAXS). The phase transition of LLC NPs takes place with ratio and pH adjustments. The properties, such as cytotoxicity, stability, drug encapsulation and release ability, have been investigated with MTT assay, cryo-TEM and UV-Vis spectroscopy. The results showed that LLC NPs were nontoxic to cells and stable to enzymatic degradation. Hydrophilic drug doxorubicin hydrochloride (DOX·HCl) could be effectively encapsulated in LLC NPs and its release rate could be regulated by pH. It was concluded that LLC NPs are potential nanocarriers in nanomedicine technologies. We hope that this work provides new guidelines for the rational design of LLC NP systems with lipopeptides for biomedical applications.

Interfacial properties of lipid sponge-like nanoparticles and the role of stabilizer on particle structure and surface interactions

The advantage of using nonlamellar lipid liquid crystalline phases has been demonstrated in many applications, such as drug delivery, protein encapsulation and crystallisation. We have recently reported that a mixture of mono- and diglycerides is able to form sponge-like nanoparticles (L3-NPs) with large enough aqueous pores to encapsulate macromolecules such as proteins. Here we use small angle neutron scattering (SANS) to reveal morphology, structural and chemical composition of these polysorbate 80 (P80) stabilized sponge phase nanoparticles, not previously known. Our results suggest that L3-NPs have a core-shell sphere structure, with a shell rich in P80. It was also found that even if P80 is mostly located on the surface, it also contributes to the formation of the inner sponge phase structure. An important aspect for the application and colloidal stability of these particles is their interfacial properties. Therefore, the interfacial behaviour of the nanoparticles on hydrophilic silica was revealed by Quartz crystal microbalance with dissipation (QCM-D) and neutron reflectivity (NR). Adsorption experiments reveal the formation of a thin lipid layer, with the dimension corresponding to a lipid bilayer after L3-NPs are in contact with hydrophilic silica. This suggests that the diglycerol monoleate/Capmul GMO-50/P80 particles reorganize themselves on this surface, probably due to interactions between P80 head group and SiO2.