Characterization of oil-free and oil-loaded liquid-crystalline particles stabilized by negatively charged stabilizer citrem

Development of Sustained Release Formulations Based on Lipid-Liquid Crystal to Control the Release of Deoxycholate: In Vitro and In Vivo Assessment

Subcutaneous injections of phosphatidylcholine (PC), sodium deoxycholate (NADC), and a mixture of them were found to be an effective option for treating cellulite. However, it is noteworthy that the injection of NADC may result in inflammation as well as necrosis in the injection area. The preparation of a sustained release formulation based on lipid-liquid crystal that controls the release of NADC could be a potential solution to address the issue of inflammation and necrosis at the site of injection. To present a practical and validated approach for accurately determining the concentration of NADC in LLC formulations, spectrofluorimetry was used based on the International Council for Harmonization (ICH) Q2 guidelines. Based on the validation results, the fluorometric technique has been confirmed as a reliable, efficient, and economical analytical method for quantifying NADC concentrations. The method demonstrated favorable attributes of linearity, precision, and accuracy, with an r2 value of 0.999. Furthermore, it exhibited excellent interday and intraday repeatability, with RSD values below 4%. The recovery percentages ranged from 97 to 100%, indicating the method's ability to accurately measure NADC concentrations. The subcutaneous injection of the LLC-NADC demonstrated a reduction in inflammation and tissue necrosis in skin tissue, along with an increase in fat lysis within 30 days, when compared to the administration of only NADC solution. Moreover, the histopathological assessment confirmed that the use of the LLC formulation did not result in any detrimental side effects for kidney or heart tissue.

Lipid-liquid crystals for 2 months controlled risperidone release: In-vitro evaluation and pharmacokinetics in rabbits

In this study, a drug delivery system based on lipid liquid crystal (LLC) was developed for the long-term delivery of risperidone to improve psychological treatment. Optimal LLC formulation was achieved based on maximum release after 60 days with different ratios of phosphatidylcholine (PC) to sorbitol monooleate (PC: SMO), tween grade 80 (w/w %), and tocopherol acetate (TA) (w/w %) using the Box-Behnken method. In vitro and ex vivo studies, pharmacokinetics, and histopathological examination in rabbits were conducted to compare the optimal LLC with Risperdal CONSTA®. The optimum formulation containing the PC to SMO ratio of 58.6%, tween 0.82% w/w, and TA 3.6% w/w was selected because it had the highest drug release percentage (100%) during about two months. Polarized optical microscopy (POM) revealed H_II mesophase with a 2-dimensional structure. Cell culture also revealed moderate cytotoxicity for LLC-risperidone. Pharmacokinetic data displayed that the optimal LLC created a more consistent drug serum level within 60 days, and histopathology results demonstrated slight to moderate damage in rabbits' organs. Furthermore, the accelerated stability test confirmed optimum stability for LLC and risperidone. This study confirmed the better pharmacokinetic potentials of SMO-based LLC systems compared with Risperdal CONSTA®, which would promote patient compliance and obviate the difficulties of additional oral therapy.

Layer-by-Layer Cell Encapsulation for Drug Delivery: The History, Technique Basis, and Applications

The encapsulation of cells with various polyelectrolytes through layer-by-layer (LbL) has become a popular strategy in cellular function engineering. The technique sprang up in 1990s and obtained tremendous advances in multi-functionalized encapsulation of cells in recent years. This review comprehensively summarized the basis and applications in drug delivery by means of LbL cell encapsulation. To begin with, the concept and brief history of LbL and LbL cell encapsulation were introduced. Next, diverse types of materials, including naturally extracted and chemically synthesized, were exhibited, followed by a complicated basis of LbL assembly, such as interactions within multilayers, charge distribution, and films morphology. Furthermore, the review focused on the protective effects against adverse factors, and bioactive payloads incorporation could be realized via LbL cell encapsulation. Additionally, the payload delivery from cell encapsulation system could be adjusted by environment, redox, biological processes, and functional linkers to release payloads in controlled manners. In short, drug delivery via LbL cell encapsulation, which takes advantage of both cell grafts and drug activities, will be of great importance in basic research of cell science and biotherapy for various diseases.

Comparison of lipid liquid crystal formulation and Vivitrol® for sustained release of Naltrexone: In vitro evaluation and pharmacokinetics in rats

Camurus' FluidCrystal® injection depot is a lipid liquid crystal (LLC) phase formation-based method, comprising of glycerol dioleate (GDO) and soy phosphatidylcholine (SPC), together with minute quantities of N-methyl-2-pyrrolidone solvent (NMP). The present study aimed to develop a method for LLC using sorbitan monooleate (LLC-SMO) instead of GDO to prepare a one-month sustained-release formulation of naltrexone (NTX) that is applied for the treatment of autism and treating alcohol dependence. The optical characteristics of the LLC were assessed by polarizing light microscopy (PLM) to reveal the presence of lamellar, hexagonal, and cubic mesophases. Furthermore, in vitro release of NTX and NMP, degradation, pharmacokinetics, and histopathology of LLC-GDO and LLC-SMO in rats were evaluated and compared to those of Vivitrol®. The PLM images revealed that the structure of LLC-SMO is hexagonal, similar to LLC-GDO. The in vitro release of NTX and its pharmacokinetic results in rats indicted that the LLC-SMO system is more uniform than LLC-GDO and Vivitrol® during 35 days. Histopathological results of LLC-GDO and LLC-SMO confirmed the biocompatibility of our LLC delivery systems. Taken together these data demonstrate that the LLC-SMO-based method, was efficient enough to sustain the release of NTX in vitro and in vivo, confirming the biocompatible nature of this delivery system.

Cell medium-dependent dynamic modulation of size and structural transformations of binary phospholipid/ω-3 fatty acid liquid crystalline nano-self-assemblies: Implications in interpretation of cell uptake studies

Lyotropic non-lamellar liquid crystalline (LLC) nanoparticles, with their tunable structural features and capability of loading a wide range of drugs and reporter probes, are emerging as versatile injectable nanopharmaceuticals. Secondary emulsifiers, such as Pluronic block copolymers, are commonly used for colloidal stabilization of LLC nanoparticles, but their inclusion often compromises the biological safety (e.g., poor hemocompatibility and enhanced cytotoxicity) of the formulation. Here, we introduce a library of colloidally stable, structurally tunable, and pH-responsive lamellar and non-lamellar liquid crystalline nanoparticles from binary mixtures of a phospholipid (phosphatidylglycerol) and three types of omega-3 fatty acids (ω-3 PUFAs), prepared in the absence of a secondary emulsifier and organic solvents. We study formulation size distribution, morphological heterogeneity, and the arrangement of their internal self-assembled architectures by nanoparticle tracking analysis, synchrotron small-angle X-ray scattering, and cryo-transmission electron microscopy. The results show the influence of type and concentration of ω-3 PUFAs in nanoparticle structural transitions spanning from a lamellar (L_α) phase to inverse discontinuous (micellar) cubic Fd3m and hexagonal phase (H₂) phases, respectively. We further report on cell-culture medium-dependent dynamic fluctuations in nanoparticle size, number and morphology, and simultaneously monitor uptake kinetics in two human cell lines. We discuss the role of these multiparametric biophysical transformations on nanoparticle-cell interaction kinetics and internalization mechanisms. Collectively, our findings contribute to the understanding of fundamental steps that are imperative for improved engineering of LLC nanoparticles with necessary attributes for pharmaceutical development.

Continuous Microfluidic Production of Citrem-Phosphatidylcholine Nano-Self-Assemblies for Thymoquinone Delivery

Lamellar and non-lamellar liquid crystalline nanodispersions, including liposomes, cubosomes, and hexosomes are attractive platforms for drug delivery, bio-imaging, and related pharmaceutical applications. As compared to liposomes, there is a modest number of reports on the continuous production of cubosomes and hexosomes. Using a binary lipid mixture of citrem and soy phosphatidylcholine (SPC), we describe the continuous production of nanocarriers for delivering thymoquinone (TQ, a substance with various therapeutic potentials) by employing a commercial microfluidic hydrodynamic flow-focusing chip. In this study, nanoparticle tracking analysis (NTA) and synchrotron small-angle X-ray scattering (SAXS) were employed to characterize TQ-free and TQ-loaded citrem/SPC nanodispersions. Microfluidic synthesis led to formation of TQ-free and TQ-loaded nanoparticles with mean sizes around 115 and 124 nm, and NTA findings indicated comparable nanoparticle size distributions in these nanodispersions. Despite the attractiveness of the microfluidic chip for continuous production of citrem/SPC nano-self-assemblies, it was not efficient as comparable mean nanoparticle sizes were obtained on employing a batch (discontinuous) method based on low-energy emulsification method. SAXS results indicated the formation of a biphasic feature of swollen lamellar (Lα) phase in coexistence with an inverse bicontinuous cubic Pn3m phase in all continuously produced TQ-free and TQ-loaded nanodispersions. Further, a set of SAXS experiments were conducted on samples prepared using the batch method for gaining further insight into the effects of ethanol and TQ concentration on the structural features of citrem/SPC nano-self-assemblies. We discuss these effects and comment on the need to introduce efficient microfluidic platforms for producing nanocarriers for delivering TQ and other therapeutic agents.

Recent advances in drug delivery applications of cubosomes, hexosomes, and solid lipid nanoparticles

The use of lipid nanocarriers for drug delivery applications is an active research area, and a great interest has particularly been shown in the past two decades. Among different lipid nanocarriers, ISAsomes (Internally self-assembled somes or particles), including cubosomes and hexosomes, and solid lipid nanoparticles (SLNs) have unique structural features, making them attractive as nanocarriers for drug delivery. In this contribution, we focus exclusively on recent advances in formation and characterization of ISAsomes, mainly cubosomes and hexosomes, and their use as versatile nanocarriers for different drug delivery applications. Additionally, the advantages of SLNs and their application in oral and pulmonary drug delivery are discussed with focus on the biological fates of these lipid nanocarriers in vivo. Despite the demonstrated advantages in in vitro and in vivo evaluations including preclinical studies, further investigations on improved understanding of the interactions of these nanoparticles with biological fluids and tissues of the target sites is necessary for efficient designing of drug nanocarriers and exploring potential clinical applications.

A structurally diverse library of glycerol monooleate/oleic acid non-lamellar liquid crystalline nanodispersions stabilized with nonionic methoxypoly(ethylene glycol) (mPEG)-lipids showing variable complement activation properties

Pluronic F127-stabilized non-lamellar liquid crystalline aqueous nanodispersions are promising injectable platforms for drug and contrast agent delivery. These nanodispersions, however, trigger complement activation in the human blood, where the extent of complement activation and opsonization processes may compromise their biological performance and safety. Here, we introduce a broad family of nanodispersions from glycerol monooleate (GMO) and oleic acid (OA) in different weight ratios, and stabilized with a plethora of nonionic methoxypoly(ethylene glycol) (mPEG)-lipids of different PEG chain length and variable lipid moiety (monounsaturated or saturated diglycerides or D-α-tocopheryl succinate). Through an integrated biophysical approach involving dynamic light scattering, synchrotron small-angle scattering, and cryo-transmission electron microscopy, we examine the impact of nonionic mPEG-lipid stabilization on size, internal self-assembled architecture, and gross morphological characteristics of nanodispersions. The results show how the nonionic mPEG-lipid type and concentration, and dependent on GMO/OA weight ratio, can variably modulate the internal architectures of nanoparticles. Assessment of complement profiling from selected nanodispersions with diverse structural heterogeneity further suggests a variable modulatory role for the lipid type of the nonionic mPEG-lipid in the extent of complement activation, which span from no activation to moderate to high levels. We comment on plausible mechanisms driving the observed complement activation variability and discuss the potential utility of these nanodispersions for future development of injectable nanopharmaceuticals.

Internal Lamellar and Inverse Hexagonal Liquid Crystalline Phases During the Digestion of Krill and Astaxanthin Oil-in-Water Emulsions

Krill oil represents an important alternative natural source of omega-3 (ω-3) polyunsaturated fatty acids (PUFAs). Considering the beneficial health effects of these essential fatty acids, particularly in various disorders including cancer, cardiovascular, and inflammation diseases, it is of paramount importance to gain insight into the digestibility of krill oil. In this work, we study the fate of krill oil-in-water emulsion, stabilized by sodium caseinate, during lipolysis by coupling time-resolved synchrotron small-angle X-ray scattering (SAXS) to flow-through lipolysis model. For gaining further insight into the effect of ω-3 PUFA-containing oil type on the dynamic structural features occurring during lipolysis, two additional astaxanthin oil-in-water emulsions, stabilized using either sodium caseinate or citrem, were subjected to lipolysis under identical experimental conditions. In addition to the difference in lipid composition in both oils, ω-3 PUFAs in astaxanthin oil, similar to fish oil, exist in the form of triacylglycerols; whereas most of those in krill oil are bound to phospholipids. SAXS showed the formation of highly ordered nanostructures on exposure of these food emulsions to the lipolysis medium: the detection of a biphasic feature of coexisting inverse hexagonal (H₂) and lamellar (L_α) liquid crystalline phases in the digested krill oil droplets' interiors, as compared to a neat L_α phase in the digested astaxanthin oil droplets. We discuss the dynamic phase behavior and describe the suggested important role of these phases in facilitating the delivery of nutrients throughout the body. In addition, the potential implication in the development of food and drug nanocarriers is briefly described.

pH-Responsive Nano-Self-Assemblies of the Anticancer Drug 2-Hydroxyoleic Acid

pH-responsive lipid nanocarriers have the potential to selectively target the acidic extracellular pH environment of cancer tissues and may further improve the efficacy of chemotherapeutics by minimizing their toxic side-effects. Here, we present the design and characterization of pH-sensitive nano-self-assemblies of the poorly water-soluble anticancer drug 2-hydroxyoleic acid (2OHOA) with glycerol monooleate (GMO). pH-triggered nanostructural transformations from 2OHOA/GMO nanoparticles with an internal inverse hexagonal structure (hexosomes) at pH around 2.0-3.0, via nanocarriers with an internal inverse bicontinuous cubic structure (cubosomes) at pH 2.0-4.5, to vesicles at pH 4.5-7.4 were observed with synchrotron small-angle X-ray scattering, and cryogenic transmission electron microscopy. ζ-potential measurements highlight that the pH-driven deprotonation of the carboxylic group of 2OHOA, and the resulting charge-repulsions at the lipid-water interface account for these nanostructural alterations. The study provides detailed insight into the pH-dependent self-assembly of 2OHOA with GMO in excess buffer at physiologically relevant pH values, and discusses the effects of pH alterations on modulating their nanostructure. The results may guide the further development of pH-responsive anticancer nanocarriers for the targeted delivery of chemotherapeutics to the local microenvironment of tumor cells.

Nanomedicines for cancer therapy: current status, challenges and future prospects

The emergence of nanomedicine as an innovative and promising alternative technology shows many advantages over conventional cancer therapies and provides new opportunities for early detection, improved treatment, and diagnosis of cancer. Despite the cancer nanomedicines’ capability of delivering chemotherapeutic agents while providing lower systemic toxicity, it is paramount to consider the cancer complexity and dynamics for bridging the translational bench-to-bedside gap. It is important to conduct appropriate investigations for exploiting the tumor microenvironment, and achieving a more comprehensive understanding of the fundamental biological processes in cancer and their roles in modulating nanoparticle–protein interactions, blood circulation, and tumor penetration. This review provides an overview of the current cancer nanomedicines, the major challenges, and the future opportunities in this research area.

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.

Structural characterization of self-assemblies of new omega-3 lipids: docosahexaenoic acid and docosapentaenoic acid monoglycerides

The attractiveness of new omega-3 (ω-3) polyunsaturated fatty acid (PUFA) monoglycerides (MAGs) lies in the amphiphilic nature and the beneficial health effects as PUFA precursors in various disorders including cancer, pulmonary hypertension, and inflammatory diseases. For exploring the potential therapeutic applications of these new amphiphilic lipids, particularly as main lipid constituents in the development of nanocarriers for delivery of drugs and PUFAs, it is of paramount importance to gain insight into their self-assembly behavior on exposure to excess water. This work describes the structural characteristics of self-assemblies based on two newly synthesized MAGs, namely docosahexaenoic acid (MAG-DHA) and docosapentaenoic acid (MAG-DPA) monoglycerides, on exposure to excess water. We found that both lipids tend to form a dominant inverse hexagonal (H₂) phase in excess water at 25 °C and a temperature-triggered structural transition to an inverse micellar solution (L₂ phase) is detected similar to that recently reported (A. Yaghmur et al., Langmuir, 2017, 33, 14045-14057) for eicosapentaenoic acid monoglyceride (MAG-EPA). An experimental SAXS structural evaluation study on the temperature-dependent behavior of these new monoglycerides is provided, and the effects of unsaturation degree and fatty acyl chain length on the self-assembled structural features in excess water and on the H₂-L₂ phase transition temperature are discussed. In addition, hexosomes stabilized by using the triblock copolymer F127 and the food-grade emulsifier citrem were investigated to gain insights into the effects of stabilizer and temperature on the internal nanostructure. These nanoparticles are attractive for use in the development of nanocarriers for delivering drugs and/or nutritional compounds as the beneficial health effects of ω-3 PUFA monoglycerides can be combined with those of loaded therapeutic agents or nutraceuticals.

Cisplatin Encapsulation Generates Morphologically Different Multicompartments in the Internal Nanostructures of Nonlamellar Liquid-Crystalline Self-Assemblies

Cisplatin ( cis-diamminedichloroplatinum(II)) is among the most potent cytotoxic agents used in cancer chemotherapy. The encapsulation of cisplatin in lipid-based drug carriers has been challenging owing to its low solubility in both aqueous and lipid phases. Here, we investigated cisplatin encapsulation in nonlamellar liquid-crystalline (LC) nanodispersions formed from a ternary mixture of phytantriol (PHYT), vitamin E (Vit E), and an anionic phospholipid [either phosphatidylglycerol (DSPG) or phosphatidylserine (DPPS)]. We show an increase in cisplatin encapsulation efficiency (EE) in nanodispersions containing 1.5-4 wt % phospholipid. The EE was highest in DPPS-containing nanodispersions (53-98%) compared to DSPG-containing counterparts (25-40%) under similar experimental conditions. Through structural and morphological characterizations involving synchrotron small-angle X-ray scattering and cryogenic transmission electron microscopy, we further show that varying the phospholipid content of cisplatin-free nanodispersions triggers an internal phase transition from a neat hexagonal (H₂) phase to a biphasic phase (internal H₂ phase coexisting with the lamellar (L_α) phase). However, cisplatin encapsulation in both DPPS- and DSPG-containing nanodispersions generates the coexistence of morphologically different multicompartments in the internal nanostructures comprising vesicles as a core, enveloped by an inverted-type surface bicontinuous cubic Im3 m (primitive, Q_II^P) phase or H₂ phase. We discuss the biophysical basis of these drug-induced morphological alterations and provide insights into the potential development of inverted-type LC nanodispersions for cisplatin delivery.

Liquid Crystalline Nanostructures as PEGylated Reservoirs of Omega-3 Polyunsaturated Fatty Acids: Structural Insights toward Delivery Formulations against Neurodegenerative Disorders

Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) are bioactive lipids with considerable impact in medicine and nutrition. These compounds exert structuring effects on the cellular membrane organization, regulate the gene expression, and modulate various signaling cascades and metabolic processes. The purpose of the present work is to demonstrate the structural features of ω-3 PUFA-containing three-dimensional supramolecular lipid assemblies suitable for pharmaceutical applications that require soft porous carriers. We investigate the liquid crystalline structures formed upon mixing of eicosapentaenoic acid (EPA, 20:5) with the lyotropic nonlamellar lipid monoolein and the formation of multicompartment assemblies. Starting with the monoolein-based lipid cubic phase, double membrane vesicles, cubosome precursors, sponge-type particles (spongosomes), mixed intermediate nonlamellar structures, and multicompartment assemblies are obtained through self-assembly at different amphiphilic compositions. The dispersions containing spongosomes as well as nanocarriers with oil and vesicular compartments are stabilized by PEGylation of the lipid/water interfaces using a phospholipid with a poly(ethylene glycol) chain. The microstructures of the bulk mixtures were examined by cross-polarized light optical microscopy. The dispersed liquid crystalline structures and intermediate states were studied by small-angle X-ray scattering, cryogenic transmission electron microscopy, and quasielastic light scattering techniques. They established that PUFA influences the phase type and the sizes of the aqueous compartments of the liquid crystalline carriers. The resulting multicompartment systems and stealth nanosponges may serve as mesoporous reservoirs for coencapsulation of ω-3 PUFA (e.g., EPA) with water-insoluble drugs and hydrophilic macromolecules toward development of combination treatment strategies of neurodegenerative and other diseases.

Lyotropic liquid crystal engineering moving beyond binary compositional space - ordered nanostructured amphiphile self-assembly materials by design

Ordered amphiphile self-assembly materials with a tunable three-dimensional (3D) nanostructure are of fundamental interest, and crucial for progressing several biological and biomedical applications, including in meso membrane protein crystallization, as drug and medical contrast agent delivery vehicles, and as biosensors and biofuel cells. In binary systems consisting of an amphiphile and a solvent, the ability to tune the 3D cubic phase nanostructure, lipid bilayer properties and the lipid mesophase is limited. A move beyond the binary compositional space is therefore required for efficient engineering of the required material properties. In this critical review, the phase transitions upon encapsulation of more than 130 amphiphilic and soluble additives into the bicontinuous lipidic cubic phase under excess hydration are summarized. The data are interpreted using geometric considerations, interfacial curvature, electrostatic interactions, partition coefficients and miscibility of the alkyl chains. The obtained lyotropic liquid crystal engineering design rules can be used to enhance the formulation of self-assembly materials and provides a large library of these materials for use in biomedical applications (242 references).

Structural Investigation of Bulk and Dispersed Inverse Lyotropic Hexagonal Liquid Crystalline Phases of Eicosapentaenoic Acid Monoglyceride

Recent studies demonstrated the potential therapeutic use of newly synthesized omega-3 (ω-3) polyunsaturated fatty acid (PUFA) monoglycerides owing to their beneficial health effects in various disorders including cancer and inflammation diseases. To date, the research was mainly focused on exploring the biological effects of these functional lipids. However, to the best of our knowledge, there is no report on the hydration-mediated self assembly of these lipids that leads to the formation of nanostructures, which are attractive for use as vehicles for the delivery of drugs and functional foods. In the present study, we investigated the temperature-composition phase behaviour of eicosapentaenoic acid monoglyceride (MAG-EPA), which is one of the most investigated ω-3 PUFA monoglycerides, during a heating-cooling cycle in the temperature range of 5-60 °C. Experimental synchrotron small-angle X-ray scattering (SAXS) evidence on the formation of a dominant inverse hexagonal (H₂) lyotropic liquid crystalline phase and its temperature-induced transition to an inverse micellar solution (L₂ phase) is presented for the fully hydrated bulk MAG-EPA system and its corresponding dispersion. We produced colloidal MAG-EPA hexosomes with an internal inverse hexagonal (H₂) lyotropic crystalline phase in the presence of F127, a well-known polymeric stabilizer, or citrem, which is a negatively charged food-grade emulsifier. In this work, we report also on the formation of MAG-EPA hexosomes by vortexing MAG-EPA in excess aqueous medium containing F127 at room temperature. This low-energy emulsification method is different than most reported studies in the literature that have demonstrated the need for using a high-energy input during the emulsification step or adding an organic solvent for the formation of such colloidal nonlamellar liquid crystalline dispersions. The designed nanoparticles hold promise for future drug and functional food delivery applications due to their unique structural properties and the potential health-promoting effects of MAG-EPA.

Direct monitoring of lipid transfer on exposure of citrem nanoparticles to an ethanol solution containing soybean phospholipids by combining synchrotron SAXS with microfluidics

Lipid exchange among citrem nanoparticles and an ethanol micellar solution containing soy phosphatidylcholine was investigated in situ by coupling small angle X-ray scattering with a microfluidic device. The produced soy phosphatidylcholine/citrem nanoparticles have great potential in the development of hemocompatible nanocarriers for drug delivery.

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.

Phytantriol based smart nano-carriers for drug delivery applications

From the last couple of decades, lyotropic liquid crystals have garnered enormous attentions in medical and pharmaceutical sciences. Non-toxic, chemically stable, and biocompatible properties of these liquid crystal systems are contributing to their applications for drug delivery. Among a large variety of liquid crystal phases, inverse bicontinuous cubic and inverse hexagonal mesophases have been extensively investigated for their ability to encapsulate and controlled release of bioactive molecules of various sizes and polarity. The concept of changing the drug release rate in situ by simply changing the mesophase structure is much more fascinating. The encapsulation of bioactive compounds in mesophase systems of desirable features in sub-micron sized particles such as hexosomes and cubosomes, at ambient and high temperature is bringing innovation in the development of new drug applications. This review article outlines unique structural features of cubosomes and hexosomes, their methods of productions, factors affecting their formations and their potential utilization as smart nano-carriers for biopharmaceuticals in drug delivery applications.

Theranostic hexosomes for cancer treatments: an in vitro study

Targeted liquid crystalline nanoparticles with a reverse hexagonal inner structure as diagnostic and therapeutic tools in oncology.

Nano-Self-Assemblies Based on Synthetic Analogues of Mycobacterial Monomycoloyl Glycerol and DDA: Supramolecular Structure and Adjuvant Efficacy

The mycobacterial cell-wall lipid monomycoloyl glycerol (MMG) is a potent immunostimulator, and cationic liposomes composed of a shorter synthetic analogue (MMG-1) and dimethyldioctadecylammonium (DDA) bromide represent a promising adjuvant that induces strong antigen-specific Th1 and Th17 responses. In the present study, we investigated the supramolecular structure and in vivo adjuvant activity of dispersions based on binary mixtures of DDA and an array of synthetic MMG-1 analogues (MMG-2/3/5/6) displaying longer (MMG-2) or shorter (MMG-3) alkyl chain lengths, or variations in stereochemistry of the polar headgroup (MMG-5) or of the hydrophobic moiety (MMG-6). Synchrotron small-angle X-ray scattering experiments and cryo transmission electron microscopy revealed that DDA:MMG-1/2/5/6 dispersions consisted of unilamellar and multilamellar vesicles (ULVs/MLVs), whereas a coexistence of both ULVs and hexosomes was observed for DDA:MMG-3, depending on the DDA:MMG molar ratio. The studies also showed that ULVs were formed, regardless of the structural characteristics of the neat MMG analogues in excess buffer [lamellar (MMG-1/2/5) or inverse hexagonal (MMG-3/6) phases]. Immunization of mice with a chlamydia antigen surface-adsorbed to DDA:MMG-1/3/6 dispersions revealed that all tested adjuvants were immunoactive and induced strong Th1 and Th17 responses with a potential for a central effector memory profile. The MMG-1 and MMG-6 analogues were equally immunoactive in vivo upon incorporation into DDA liposomes, despite the reported highly different immunostimulatory properties of the neat analogues in vitro, which were attributed to the different nanostructural characteristics. This clearly demonstrates that optimal formulation and delivery of MMG analogues to the immune system is of major importance and challenges the use of in vitro screening assays with nondispersed compounds to identify potential new vaccine adjuvants.

Cubosomes and hexosomes as versatile platforms for drug delivery

Nonlamellar liquid crystalline phases are attractive platforms for drug solubilization and targeted delivery. The attractiveness of this formulation principle is linked to the nanostructural versatility, compatiblity, digestiblity and bioadhesive properties of their lipid constituents, and the capability of solubilizing and sustaining the release of amphiphilic, hydrophobic and hydrophilic drugs. Nonlamellar liquid crystalline phases offer two distinct promising strategies in the development of drug delivery systems. These comprise formation of ISAsomes (internally self-assembled ‘somes’ or particles) such as cubosomes and hexosomes, and in situ formation of parenteral dosage forms with tunable nanostructures at the site of administration. This review outlines the unique features of cubosomes and hexosomes and their potential utilization as promising platforms for drug delivery.

Amino Acid Induced Modification of Self-Assembled Monoglyceride-Based Nanostructures

Self-assembled phases based on monoglycerides are promising candidates for drug delivery systems. Alterations of these phases need to be performed by addition of substances which are biocompatible. Inverse bicontinuous cubic phases are altered by the addition of five amino acids, namely, glycine, phenylalanine, alanine, glutamine, and tryptophan. These natural molecules have a diversity of side chains which predicts their polarity and subsequently their interaction with the interfacial region. Whereas polar amino acids cause a slight shrinking of the fully hydrated phase, amino acids with a nonpolar side chain expand it. Tryptophan is also able to provoke a growth of inverse hexagonal, micellar cubic, and micellar structures. Amino acid concentrations in the aqueous phase, even above the amino acid's solubility, further affect all aforementioned structures and cause a significant enlargement of up to 26%. Besides the amino acids' impact on the structural sizes, they also affect the phase transition temperatures.

Modulatory effect of human plasma on the internal nanostructure and size characteristics of liquid-crystalline nanocarriers

The inverted-type liquid-crystalline dispersions comprising cubosomes and hexosomes hold much potential for drug solubilization and site-specific targeting on intravenous administration. Limited information, however, is available on the influence of plasma components on nanostructural and morphological features of cubosome and hexosome dispersions, which may modulate their stability in the blood and their overall biological performance. Through an integrated approach involving SAXS, cryo-TEM, and nanoparticle tracking analysis (NTA) we have studied the time-dependent effect of human plasma (and the plasma complement system) on the integrity of the internal nanostructure, morphology, and fluctuation in size distribution of phytantriol (PHYT)-based nonlamellar crystalline dispersions. The results indicate that in the presence of plasma the internal nanostructure undergoes a transition from the biphasic phase (a bicontinuous cubic phase with symmetry Pn3m coexisting with an inverted-type hexagonal (H2) phase) to a neat hexagonal (H2) phase, which decreases the median particle size. These observations were independent of a direct effect by serum albumin and dispersion-mediated complement activation. The implication of these observations in relation to soft nanocarrier design for intravenous drug delivery is discussed.

PEGylation of phytantriol-based lyotropic liquid crystalline particles--the effect of lipid composition, PEG chain length, and temperature on the internal nanostructure

Poly(ethylene glycol)-grafted 1,2-distearoyl-sn-glycero-3-phosphoethanolamines (DSPE-mPEGs) are a family of amphiphilic lipopolymers attractive in formulating injectable long-circulating nanoparticulate drug formulations. In addition to long circulating liposomes, there is an interest in developing injectable long-circulating drug nanocarriers based on cubosomes and hexosomes by shielding and coating the dispersed particles enveloping well-defined internal nonlamellar liquid crystalline nanostructures with hydrophilic PEG segments. The present study attempts to shed light on the possible PEGylation of these lipidic nonlamellar liquid crystalline particles by using DSPE-mPEGs with three different block lengths of the hydrophilic PEG segment. The effects of lipid composition, PEG chain length, and temperature on the morphology and internal nanostructure of these self-assembled lipidic aqueous dispersions based on phytantriol (PHYT) were investigated by means of synchrotron small-angle X-ray scattering and Transmission Electron Cryo-Microscopy. The results suggest that the used lipopolymers are incorporated into the water-PHYT interfacial area and induce a significant effect on the internal nanostructures of the dispersed submicrometer-sized particles. The hydrophilic domains of the internal liquid crystalline nanostructures of these aqueous dispersions are functionalized, i.e., the hydrophilic nanochannels of the internal cubic Pn3m and Im3m phases are significantly enlarged in the presence of relatively small amounts of the used DSPE-mPEGs. It is evident that the partial replacement of PHYT by these PEGylated lipids could be an attractive approach for the surface modification of cubosomal and hexosomal particles. These PEGylated nanocarriers are particularly attractive in designing injectable cubosomal and hexosomal nanocarriers for loading drugs and/or imaging probes.

SPECT/CT imaging of radiolabeled cubosomes and hexosomes for potential theranostic applications

We have developed a highly efficient method for the radiolabeling of phytantriol (PHYT)/oleic acid (OA)-based hexosomes based on the surface chelation of technetium-99m ((99m)Tc) to preformed hexosomes using the polyamine 1, 12-diamino-3, 6, 9-triazododecane (SpmTrien) as chelating agent. We also report on the unsuccessful labeling of cubosomes using the well-known chelating agent hexamethylpropyleneamine oxime (HMPAO). The (99m)Tc-labeled SpmTrien-hexosomes ((99m)Tc-SpmTrien-hexosomes) were synthesized with good radiolabeling (84%) and high radiochemical purity (>90%). The effect of radiolabeling on the internal nanostructure and the overall size of these aqueous dispersions was investigated by using synchrotron small angle X-ray scattering (SAXS), dynamic light scattering (DLS), and transmission electron cryo microscopy (cryo-TEM). Further, we show the utility of (99m)Tc-SpmTrien-hexosomes for the in vivo imaging of healthy mice using single photon emission computed tomography (SPECT) in combination with computed tomography (CT), i.e. SPECT/CT. SPECT/CT experiments of subcutaneously administered (99m)Tc-SpmTrien-hexosomes to the flank of mice showed a high stability in vivo allowing imaging of the distribution of the radiolabeled hexosomes for up to 24 h. These injected (99m)Tc-SpmTrien-hexosomes formed a deposit within the subcutaneous adipose tissue, displaying a high biodistribution of ≈ 343% injected dose/g tissue (%ID/g), with negligible uptake in other organs and tissues. The developed (99m)Tc labeling method for PHYT/OA-based hexosomes could further serve as a useful tool for investigating and imaging the in vivo performance of cubosomal and hexosomal drug nanocarriers.