Phytantriol and glyceryl monooleate cubic liquid crystalline phases as sustained-release oral drug delivery systems for poorly water soluble drugs I. Phase behaviour in physiologically-relevant media

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.

The Addition of Resveratrol-Loaded Emulsions to Yogurts: Physicochemical Characterization, In Vitro Bioaccessibility and NMR-Based Nutritional Profiles

In this study, resveratrol-loaded nano-emulsions were added to yogurts, improving the physicochemical properties and functional factors and realizing the development of nutrient-fortified yogurt. Yogurts added with free resveratrol (Y-R), resveratrol-loaded emulsions stabilized by sodium caseinate (Y-NN), decaglycerol monooleate (Y-DN), and sodium caseinate-decaglycerol monooleate (Y-DND) were evaluated for their physicochemical properties, including pH, titratable acidity, syneresis, and textural parameters, with 5-day intervals for 15-day storage. The resveratrol retention rate was analyzed in the Y-R, Y-NN, Y-DN, and Y-NDN groups during 15 days of storage. The dynamic bioaccessibility of resveratrol and the NMR-based nutritional profile of yogurt in the Y-R, Y-NN, Y-DN, and the Y-NDN group were investigated after in vitro digestion. The results demonstrated that the addition of resveratrol emulsion decreased the hardness of yogurt while evaluating its titratable acidity and water-holding capacity, which were characterized by high stability. The stability of resveratrol added in the form of an emulsion was significantly higher than that of the free form. Compared with the other groups, the yogurt formulated with sodium caseinate/decaglycerol monooleate (NaCas/DGMO) emulsion showed the highest resveratrol retention rate, about 70%. In vitro digestion showed that encapsulation effectively and persistently improved the dynamic bioaccessibility of resveratrol. Additionally, NMR-based nutritional profile analysis before and after in vitro digestion demonstrated that resveratrol emulsion nutritional fortification promoted the release of nutrients, improving the nutritional value of yogurt. These findings offered theoretical guidance and technical support for the use of resveratrol nano-emulsions in yogurt.

Lyophilized Lipid Liquid Crystalline Nanoparticles as an Antimicrobial Delivery System

Lipid liquid crystalline nanoparticles (LCNPs) are unique nanocarriers that efficiently deliver antimicrobials through biological barriers. Yet, their wide application as an antimicrobial delivery system is hindered by their poor stability in aqueous dispersions. The production of dried LCNP powder via lyophilization is a promising approach to promote the stability of LCNPs. However, the impact of the process on the functionality of the loaded hydrophobic cargoes has not been reported yet. Herein, we investigated the potential of lyophilization to produce dispersible dry LCNPs loaded with a hydrophobic antimicrobial compound, gallium protoporphyrin (GaPP). The effect of lyophilization on the physicochemical characteristics and the antimicrobial activity of rehydrated GaPP-LCNPs was studied. The rehydrated GaPP-LCNPs retained the liquid crystalline structure and were monodisperse (PDI: 0.27 ± 0.02), with no significant change in nanoparticle concentration despite the minor increase in hydrodynamic diameter (193 ± 6.5 compared to 173 ± 4.2 prior to freeze-drying). Most importantly, the efficacy of the loaded GaPP as an antimicrobial agent and a photosensitizer was not affected as similar MIC values were obtained against S. aureus (0.125 µg/mL), with a singlet oxygen quantum yield of 0.72. These findings indicate the suitability of lyophilization to produce a dry form of LCNPs and pave the way for future studies to promote the application of LCNPs as an antimicrobial delivery system.

Bicontinuous Cubic Liquid Crystals as Potential Matrices for Non-Invasive Topical Sampling of Low-Molecular-Weight Biomarkers

Many skin disorders, including cancer, have inflammatory components. The non-invasive detection of related biomarkers could therefore be highly valuable for both diagnosis and follow up on the effect of treatment. This study targets the extraction of tryptophan (Trp) and its metabolite kynurenine (Kyn), two compounds associated with several inflammatory skin disorders. We furthermore hypothesize that lipid-based bicontinuous cubic liquid crystals could be efficient extraction matrices. They comprise a large interfacial area separating interconnected polar and apolar domains, allowing them to accommodate solutes with various properties. We concluded, using the extensively studied GMO-water system as test-platform, that the hydrophilic Kyn and Trp favored the cubic phase over water and revealed a preference for locating at the lipid-water interface. The interfacial area per unit volume of the matrix, as well as the incorporation of ionic molecules at the lipid-water interface, can be used to optimize the extraction of solutes with specific physicochemical characteristics. We also observed that the cubic phases formed at rather extreme water activities (>0.9) and that wearing them resulted in efficient hydration and increased permeability of the skin. Evidently, bicontinuous cubic liquid crystals constitute a promising and versatile platform for non-invasive extraction of biomarkers through skin, as well as for transdermal drug delivery.

Lipidic lyotropic liquid crystals: Insights on biomedical applications

Liquid crystals (LCs) possess unique physicochemical properties, translatable into a wide range of applications. To date, lipidic lyotropic LCs (LLCs) have been extensively explored in drug delivery and imaging owing to the capability to encapsulate and release payloads with different characteristics. The current landscape of lipidic LLCs in biomedical applications is provided in this review. Initially, the main properties, types, methods of fabrication and applications of LCs are showcased. Then, a comprehensive discussion of the main biomedical applications of lipidic LLCs accordingly to the application (drug and biomacromolecule delivery, tissue engineering and molecular imaging) and route of administration is examined. Further discussion of the main limitations and perspectives of lipidic LLCs in biomedical applications are also provided. STATEMENT OF SIGNIFICANCE: Liquid crystals (LCs) are those systems between a solid and liquid state that possess unique morphological and physicochemical properties, translatable into a wide range of biomedical applications. A short description of the properties of LCs, their types and manufacturing procedures is given to serve as a background to the topic. Then, the latest and most innovative research in the field of biomedicine is examined, specifically the areas of drug and biomacromolecule delivery, tissue engineering and molecular imaging. Finally, prospects of LCs in biomedicine are discussed to show future trends and perspectives that might be utilized. This article is an ampliation, improvement and actualization of our previous short forum article "Bringing lipidic lyotropic liquid crystal technology into biomedicine" published in TIPS.

Monoolein-based nanodispersions for cutaneous co-delivery of methylene blue and metformin: Thermal and structural characterization and effects on the cutaneous barrier, skin penetration and cytotoxicity

This study evaluated the potential of monoolein (MO)-based nanodispersions to promote the cutaneous co-delivery of metformin (MET) and methylene blue (MB) for the treatment of non-melanoma skin cancer. MO-based nanodispersions were obtained using Kolliphor® P407 (KP) and/or sodium cholate (CH), and characterized concerning the structure, thermal stability, ability to disrupt the skin barrier, cutaneous permeation and retention of MB and MET. Additionally, the cytotoxic effect of MO nanodispersions-mediated combination therapy using MET and MB in A431 cells was evaluated. The nanodispersions exhibited nanometric size (<200 nm) and thermal and physical stability. Small angle X-ray scattering studies revealed multiple structures depending on composition. They were able to interact with stratum corneum lipid structure, increasing its fluidity. The effect of MO-nanodispersions on topical/transdermal delivery of MB and MET was composition-dependent. Nanodispersions with low MO content (5 %) and stabilized with KP and CH (0.05-0.10 %) were the most promising, enhancing the cutaneous delivery of MB and MET by 1.9 to 2.2-fold and 1.4 to 1.7-fold, respectively, compared to control. Cytotoxic studies revealed that the most promising MO nanodispersion-mediated combination therapy using MET and MB (1:1) reduced the IC₅₀ by 24-fold, compared to MB solution, and a further reduction (1.5-fold) was observed by MB photoactivation.

Enhancing the photoluminescence and cellular uptake of fluorescent carbon nanodots via cubosome lipid nanocarriers

Carbon nanodots (C-dots) have attracted much attention for their use in the fields of bioimaging, drug delivery, and sensing due to their excellent fluorescent and photoluminescent properties, photostability, biocompatibility, and amenability to surface modification. Herein, we report a nanocomposite formulation of C-dots (<5 nm) encapsulated in lipid-based lyotropic liquid crystalline nanoparticles (∼250 nm) via either passive diffusion or electrostatic mechanisms. The physicochemical properties of the nanocomposite formulation including particle size, surface charge, internal cubic nanostructures, and pH-dependent fluorescent properties were characterised. Upon loading of C-dots into lipid nanoparticles, the highly ordered inverse bicontinuous cubic mesophase existed in the internal phase of the nanoparticles, demonstrated by synchrotron small angle X-ray scattering, molecular dynamic simulation and cryogenic transmission electron microscopy. The pH-dependent fluorescent property of the C-dots was modified via electrostatic interaction between the C-dots and cationic lipid nanoparticles, which further enhanced the brightness of C-dots through self-quenching prevention. The cytotoxicity and cellular uptake efficiency of the developed nanocomposites were also examined in an epithelial gastric adenocarcinoma cell line (AGS) and a macrophage cell line (stimulated THP-1). Compared to free C-dots, the uptake and cell imaging potential of the C-dot nanocomposites was significantly improved, by several orders of magnitude as demonstrated by cytoplasmic fluorescent intensities using confocal microscopy. Loading C-dots into mesoporous lipid nanocarriers presents a new way of modifying C-dot physicochemical and fluorescent properties, alternative to direct chemical surface modification, and advances the bioimaging potential of C-dots by enhancing cellular uptake efficiency and converging C-dot light emission.

Tuning Nanostructured Lyotropic Liquid Crystalline Mesophases in Lipid Nanoparticles with Protic Ionic Liquids

We herein report 13 protic ionic liquids (PILs) as tunable solvation media to regulate the internal lyotropic liquid crystalline mesophase of monoolein-based nanoparticles. A range of nanostructures, including inverse bicontinuous cubic, inverse hexagonal, and sponge/lamellar mesophases, were produced and verified by synchrotron small-angle X-ray scattering. Notably, manipulating the cation/anion structures of the PILs can alter the monoolein packing behavior and cause a sequential phase transition (hexagonal → cubic → lamellar) in the nanoparticles. The solvent channels inside the nanoparticles were enlarged up to 40% under certain PIL-water conditions, making these materials prospective for encapsulation of large molecules. Finally, a freeze-drying study demonstrated the ability of PILs to preserve nanostructure upon reconstitution of the nanoparticles compared to that in pure water. This study opens a new route for fine-tuning lyotropic liquid crystalline structures using PILs, which circumvents issues encountered using conventional salts.

Differential Effects of TPM, A Phosphorylated Tocopherol Mixture, and Other Tocopherol Derivatives as Excipients for Enhancing the Solubilization of Co-Enzyme Q10 as a Lipophilic Drug During Digestion of Lipid- Based Formulations

BACKGROUND

The tocopherol-based excipient, TPM, when incorporated into a medium-chain triglyceride (MCT)-based lipid formulation, has been previously shown to improve the solubilization of Coenzyme Q10 (CoQ10) during in vitro digestion which is strongly correlated with enhanced exposure in vivo.

METHODS

The current study aimed to gain further understanding of the MCT + TPM co-formulation, by assessing the formulation performance under fasted and fed in vitro digestion conditions, with different drug and excipient loading levels. Natural and synthetic-derived TPM were equivalent, and with d-α- tocopherol polyethylene glycol 1000 succinate (TPGS) outperformed other derivatives in enhancing the solubilisation of CoQ10 during digestion.

RESULT

Fed conditions significantly improved the solubility of CoQ10 during in vitro digestion of the formulation in comparison with fasted conditions. The addition of TPM at 10% (w/w) of the total MCT + TPM provided optimal performance in terms of CoQ10 solubilization during digestion.

CONCLUSION

The results further highlights the potential of TPM as an additive in lipid formulations to improve the solubilization and oral bioavailability of poorly water-soluble compounds.

Non-Lamellar Lyotropic Liquid Crystalline Lipid Nanoparticles for the Next Generation of Nanomedicine

Nonlamellar lyotropic liquid crystalline (LLC) lipid nanomaterials have emerged as a promising class of advanced materials for the next generation of nanomedicine, comprising mainly of amphiphilic lipids and functional additives self-assembling into two- and three-dimensional, inverse hexagonal, and cubic nanostructures. In particular, the lyotropic liquid crystalline lipid nanoparticles (LCNPs) have received great interest as nanocarriers for a variety of hydrophobic and hydrophilic small molecule drugs, peptides, proteins, siRNAs, DNAs, and imaging agents. Within this space, there has been a tremendous amount of effort over the last two decades elucidating the self-assembly behavior and structure-function relationship of natural and synthetic lipid-based drug delivery vehicles in vitro, yet successful clinical translation remains sparse due to the lack of understanding of these materials in biological bodies. This review provides an overview of (1) the benefits and advantages of using LCNPs as drug delivery nanocarriers, (2) design principles for making LCNPs with desirable functionalities for drug delivery applications, (3) current understanding of the LLC material-biology interface illustrated by more than 50 in vivo, preclinical studies, and (4) current patenting and translation activities in a pharmaceutical context. Together with our perspectives and expert opinions, we anticipate that this review will guide future studies in developing LCNP-based drug delivery nanocarriers with the objective of translating them into a key player among nanoparticle platforms comprising the next generation of nanomedicine for disease therapy and diagnosis.

Colloidal aspects of dispersion and digestion of self-dispersing lipid-based formulations for poorly water-soluble drugs

Self-dispersing lipid-based formulations, particularly self-microemulsifying drug delivery systems (SMEDDS) have gained an increased interest in recent times as a means to enhance the oral bioavailability of poorly water-soluble lipophilic drugs. Upon dilution, SMEDDS self-emulsify in an aqueous fluid and usually form a kinetically stable oil-in-water emulsion or in some rare cases a true thermodynamically stable microemulsion. The digestion of the formulation leads to the production of amphiphilic digestion products that interact with endogenous amphiphilic components and form self-assembled colloidal phases in the aqueous environment of the intestine. The formed colloidal phases play a pivotal role in maintaining the lipophilic drug in the solubilised state during gastrointestinal transit prior to absorption. Thus, this review describes the structural characterisation techniques employed for SMEDDS and the recent literature studies that elucidated the colloidal aspects during dispersion and digestion of SMEDDS and solid SMEDDS. Possible future studies are proposed to gain better understanding on the colloidal aspects of SMEDDS and solid SMEDDS.

Cubosomes with surface cross-linked chitosan exhibit sustained release and bioavailability enhancement for vinpocetine

Cubosomes with surface cross-linked chitosan exhibit anti-digestion effect, sustained drug release behavior, and significantly enhanced oral bioavailability of vinpocetine.

Bile Salts Caught in the Act: From Emulsification to Nanostructural Reorganization of Lipid Self-Assemblies

Bile salts (BSs) are important for the digestion and absorption of fats and fat-soluble vitamins in the small intestine. In this work, we scrutinized, with small-angle X-ray scattering (SAXS), the crucial functions of bile salts beyond their capacity for the interfacial stabilization of submicrometer-sized lipid particles. By studying a wide compositional range of BS-lipid dispersions using two widely applied lipids for drug-delivery systems (one a monoglyceride being stabilizer-sensitive and the other an aliphatic alcohol being relatively stabilizer-insensitive), we identified the necessary BS to lipid ratios to guarantee full emulsification. A novel ad hoc developed global small-angle-X-ray scattering analysis method revealed that the addition of BS hardly changes the bilayer thicknesses in bicontinuous phases, while significant membrane thinning is observed in the coexisting fluid lamellar phase. Furthermore, we show that a BS strongly decreases the average critical packing parameter. At increasing BS concentration, the order of phases formed is (i) the bicontinuous diamond cubic ( Pn3 m), (ii) the bicontinuous primitive cubic ( Im3 m), and (iii) the fluid lamellar phase ( L_α). These distinctive findings on BS-driven "emulsification" and "membrane curvature reduction" provide new molecular-scale insights for the understanding of the interfacial action of bile salts on lipid assemblies.

Deuterated phytantriol - A versatile compound for probing material distribution in liquid crystalline lipid phases using neutron scattering

Phytantriol is an interfacially-active lipid that is chemically robust, non-digestible and forms particles with internal bicontinuous cubic phase structures (cubosomes) when dispersed with non-ionic surfactants at ambient and physiological temperatures. The liquid crystalline internal structure of phytantriol-based cubosomes can be changed to alter the interfacial contact area/topology with the aqueous dispersant to trigger bioactive payload release or to alter the local membrane curvature around bound or embedded proteins. To enable the study of payload distribution, structure and transformation kinetics within phytantriol particles by neutron scattering techniques it is desirable to have access to a deuterated version of this molecule but to date a synthetic route has not been available. The first successful synthesis of phytantriol-d₃₉ is presented here alongside a preliminary physical characterisation of related particle structures when phytantriol-d₃₉ is dispersed using two non-ionic surfactants, Tween® 80 and Pluronic® F127. Synchrotron small angle X-ray scattering (SAXS) was used to confirm that phytantriol-d₃₉-based nanoparticles in D₂O form similar liquid crystalline structures to those of their natural isotopic abundance (phytantriol/H₂O) counterparts as a function of temperature. Finally, small angle neutron scattering (SANS) with solvent contrast to match out the phytantriol-d₃₉ structuring was used to show that the spatial correlations between the Tween® and Pluronic® non-ionic surfactant molecules are different within dispersed phytantriol-d₃₉ particles with different liquid crystalline structures in D₂O. The surfactant molecules in phytantriol-d₃₉/Tween® 80 particles with Im3m cubic structures were found to follow a self-avoiding walk, whereas in phytantriol-d₃₉/Pluronic® F127 particles with Pn3m cubic structures they were found to follow a more rod-like packing arrangement.

Polymer-free cubosomes for simultaneous bioimaging and photodynamic action of photosensitizers in melanoma skin cancer cells

We designed novel polymer-free cubic bicontinuous liquid crystalline dispersions (cubosomes) using monoolein as molecular building block, phospholipids as stabilizers, propylene glycol as hydrotrope. Their kinetic stability was evaluated by analysing the backscattering profiles upon ageing, and the most stable formulation was chosen as potential photosensitizers delivery vehicle for photodynamic therapy (PDT) of human skin melanoma cells. Morphological and topological features of such formulation alternatively loaded with Chlorin e6 or meso-Tetraphenylporphine-Mn(III) chloride photosensitizing dyes were investigated by cryo-TEM, DLS, and SAXS. Bioimaging studies demonstrated that Me45 and MeWo cell lines effectively internalized these cubosomes formulations. Particularly, photodynamic activity experiments proved both the very low cytotoxicity of the cubosomes formulation loaded with Chlorin e6 dye in the "dark" condition, and its significant cytotoxic effect after photoirradiation. The toxic effect recorded when the photosensitizer was encapsulated within the cubosomes was shown to be one order of magnitude higher than that caused by the free photosensitizer. This is the first report of biocompatible polymer-free cubosomes for potential application in both PDT and bioimaging of skin malignant melanoma.

Solubilisation behaviour of poorly water-soluble drugs during digestion of solid SMEDDS

Lipid based-formulations can enhance the bioavailability of poorly water-soluble lipophilic drugs through enhanced solubilisation of drugs in the gastrointestinal (GI) tract during digestion. This study investigates the solubilisation behaviour of poorly water-soluble drugs upon digestion of solid self-microemulsifying drug delivery system (S-SMEDDS). The S-SMEDDS were prepared using two different core lipids, Gelucire® 44/14 (GEL) or glyceryl monooleate (GMO), and were loaded with two model drugs, fenofibrate (FEN) and cinnarizine (CINN). S-SMEDDS formulations were characterized using wide-angle X-ray scattering (WAXS) and Raman spectroscopy, and their structural behaviour and drug solubilisation behaviour were monitored using drug-related diffraction peaks during digestion under fasted and fed simulated intestinal conditions using time-resolved small and wide-angle X-ray scattering (SAXS/WAXS). The concentrations of FEN and CINN released into the aqueous phase (AP) during digestion were quantified using high-performance liquid chromatography (HPLC). Both model drugs, FEN and CINN, had greater solubility in the GMO-based S-SMEDDS formulations and were partially solubilised into lipid matrix and uniformly distributed in solid formulations. The extent of digestion was greater for the GEL-based systems (92-94%) than GMO-based systems (65-75%) as was the rate of digestion. GEL-based S-SMEDDS formulations formed a lamellar phase during digestion in the fasted state and formed mixed micelles in the fed state. In contrast, the GMO-based system formed the mixed micelles in both intestinal conditions. The time-resolved SAXS profiles revealed solubilisation of crystalline drugs into the lipolysis products. Synchrotron SAXS results were in correlation with the HPLC measurements, confirming the ability of the SAXS technique to monitor drug behaviour and showing that the digestion of S-SMEDDS can enhance drug solubilisation.

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).

Liquid crystalline drug delivery vehicles for oral and IV/subcutaneous administration of poorly soluble (and soluble) drugs

Poorly soluble drug molecules often have low bioavailability issues and absorption problems in the clinical setting. As the number of poorly soluble drugs increases from discovery, developing technologies to enhance their solubility, while also controlling their release is one of the many challenges facing the pharmaceutical industry today. Liquid crystalline systems, nanoparticulate or macro-matrix, self-assemble in the presence of an aqueous environment and can provide a solubility enhancement, while also controlling the drug release rate. This review examines the fundamentals of liquid crystalline systems through the representative literature, concluding with examples of liquid crystalline systems in clinical trials development. The review focus is on the potential of utilizing liquid crystalline systems for poorly soluble drugs, in the areas of oral delivery and IV/subcutaneous, followed by water soluble molecules. Key considerations in utilizing liquid crystalline systems advantages while also discussing potential areas of key research that may be needed will be highlighted.

Factors affecting the structure of lyotropic liquid crystals and the correlation between structure and drug diffusion

Lyotropic liquid crystals (LLCs) formed by the self-assembly of amphiphilic molecules in a solvent (usually water) have attracted increasingly greater attention in the last few decades, especially the lamellar phase (L_α), the reversed bicontinuous cubic phase (Q₂) and the reversed hexagonal phase (H₂). Such phases offer promising prospects for encapsulation of a wide range of target molecules with various sizes and polarities owing to the unique internal structures. Also, different structures of mesophases can give rise to different diffusion coefficients. The bicontinuous cubic phase and the hexagonal phase have been demonstrated to control and sustain the release of active molecules. Furthermore, the structures are susceptible to many factors such as water content, temperature, pH, the presence of additives etc. Many researchers have been studying these influencing factors in order to accurately fabricate the desired phase. In this paper, we give a review of the characteristics of different structures of liquid crystalline phases, the influencing factors on the phase transition of liquid crystals and the relationship between structures of LLC and drug diffusion. We hope our review will provide some insights into how to manipulate in a controlled manner the rate of incorporating and transferring molecules by altering the structure of lyotropic mesophases.

Factors such as amphiphilic molecules , water content, temperature, pressure, light and magnetic field on the structures of LLCs.

Self-Assembled Lipid Cubic Phase and Cubosomes for the Delivery of Aspirin as a Model Drug

Three-dimensionally organized lipid cubic self-assemblies and derived oil-in-water emulsions called "cubosomes" are attractive for various biotechnological applications due to their ability to be loaded with functional molecules and their associated sustained release properties. Here, we employed both of these lipid-based systems for the delivery of a model drug, aspirin, under comparable conditions. Studies were performed by varying drug-to-lipid ratio and the type of release medium, water and phosphate buffer saline (PBS). Release rates were determined using UV-vis spectroscopy, and small-angle X-ray scattering was used to confirm the type of self-assembled nanostructures formed in these lipid systems. The release from the bulk lipid cubic phase was sustained as compared to that of dispersed cubosomes, and the release in PBS was more efficient than in water. The tortuosity of the architecture, length of the diffusion pathway, type of nanostructure, and physicochemical interaction with the release media evidently contribute to these observations. This work is particularly important as it is the first report where both of these nanostructured lipid systems have been studied together under similar conditions. This work provides important insights into understanding and therefore controlling the release behavior of lipid-based drug nanocarriers.

Responsive self-assembled nanostructured lipid systems for drug delivery and diagnostics

While stimuli-responsive polymers have received a huge amount of attention in the literature, responsive lipid-based mesophase systems offer unique opportunities in biomedical applications such as drug delivery and biosensing. The different mesophase equilibrium structures enables dynamic switching between nanostructures to facilitate drug release or as a transducer for recognition events. In drug delivery, this behavior offers researchers the means to deliver a therapeutic payload at a specific rate and time i.e. 'on-demand'. This review summarizes the distinctive features of these multifaceted materials and aggregates the current state of the art research from our groups and others into the use of these materials as bulk gels and nanostructured dispersions for drug delivery, biosensing and diagnostics.

Fabrication of novel GMO/Eudragit E100 nanostructures for enhancing oral bioavailability of carvedilol

In the present work, novel nanostructures comprising of glyceryl monooleate (GMO) and Eudragit E100 were prepared using high intensity ultrasonic homogenization. 3(2) Factorial design approach was used for optimization of nanostructures. Results of regression analysis revealed that the amount of GMO and Eudragit E100 had a drastic effect on particle size and percent entrapment efficiency. Optimized carvedilol-loaded nanostructures (Car-NS) were characterized by FTIR, TEM, DSC, in vitro drug release study. Pharmacokinetic parameters such as Cmax, Tmax, Ke, Ka, Vd and AUC were estimated for Car-NS upon its oral administration in Sprague-Dawley rats. Particle size of Car-NS was found to be 183 ± 2.43 nm with an entrapment efficiency of 81.4 ± 0.512%. FTIR studies revealed loading and chemical compatibility of carvedilol with the components of nanostructures. DSC thermograms did not show endothermic peak for melting of carvedilol which could be attributed to solubilization of carvedilol in molten GMO during DSC run. The prepared Car-NS released carvedilol in sustained manner over a period of 10 h as suggested by in vitro drug release study. The pharmacokinetic study of Car-NS showed significant improvement in Cmax (two fold, p < 0.001) and AUC (four folds, p < 0.001) of carvedilol when compared to carvedilol suspension. Car-NS were found to be stable for a period of 3 months. Thus, a stable, floating, multiparticulate GMO/Eudragit E100 nanostructures having ability to release the drug in sustained manner with enhanced oral bioavailability can prove to be a promising carrier system for poorly water soluble drugs.

Phytantriol based liquid crystal provide sustained release of anticancer drug as a novel embolic agent

Phytantriol has received increasing amount of attention in drug delivery system, however, the ability of the phytantriol based liquid crystal as a novel embolic agent to provide a sustained release delivery system is yet to be comprehensively demonstrated. The purpose of this study was to prepare a phytantriol-based cubic phase precursor solution loaded with anticancer drug hydroxycamptothecine (HCPT) and evaluate its embolization properties, in vitro drug release and cytotoxicity. Phase behavior of the phytantriol-solvent-water system was investigated by visual inspection and polarized light microscopy, and no phase transition was observed in the presence of HCPT within the studied dose range. Water uptake by the phytantriol matrices was determined gravimetrically, suggesting that the swelling complied with the second order kinetics. In vitro evaluation of embolic efficacy indicated that the isotropic solution displayed a satisfactory embolization effect. In vitro drug release results showed a sustained-release up to 30 days and the release behavior was affected by the initial composition and drug loading. Moreover, the in vitro cytotoxicity and anticancer activity were evaluated by MTT assay. No appreciable mortality was observed for NIH 3T3 cells after 48 h exposure to blank formulations, and the anticancer activity of HCPT-loaded formulations to HepG2 and SMMC7721 cells was strongly dependent on the drug loading and treatment time. Taken together, these results indicate that phytantriol-based cubic phase embolic gelling solution is a promising potential carrier for HCPT delivery to achieve a sustained drug release by vascular embolization, and this technology may be potential for clinical applications.

Nanostructured reverse hexagonal liquid crystals sustain plasma concentrations for a poorly water-soluble drug after oral administration

Reverse hexagonal (H2) liquid crystals formed from selachyl alcohol were demonstrated to sustain the absorption of the poorly water-soluble drug cinnarizine (CZ) after oral administration to rats. When CZ was administered as a bolus lipid solution in selachyl alcohol, the T max was observed to be 23.5 ± 5.9 h, significantly longer than the control suspension (1 h). Administration of selachyl alcohol as dispersed nanoparticles (hexosomes) also resulted in a sustained plasma profile, with drug concentrations maintained from 20 to 40 ng/mL over the first 24 h after administration. Sustained absorption of CZ from the selachyl alcohol hexosomes led to a significant enhancement (p < 0.05) in oral bioavailability (F% = 17%) compared to the control CZ suspension (9%). Analysis of selachyl alcohol hexosomes using small-angle x-ray scattering indicated that neither the presence of CZ (7 mg/g) nor simulated intestinal fluid altered the H2 nanostructure. Selachyl alcohol is not susceptible to digestion. Prolonged absorption from the selachyl alcohol-based H2 systems was attributed to the non-digestible nature of the lipid, similar to non-digestible phytantriol cubic (V2) systems previously reported. Furthermore, the likely presence of non-sink conditions in the gastric compartment provides a drug reservoir requiring gastric emptying to stimulate drug release from the formulation. This study highlights the potential use of non-digestible liquid crystalline systems generally and nanostructured liquid crystalline particles in particular as novel sustained oral drug delivery systems.

Epidermal growth factor receptor-targeted lipid nanoparticles retain self-assembled nanostructures and provide high specificity

Next generation drug delivery utilising nanoparticles incorporates active targeting to specific sites. In this work, we combined targeting with the inherent advantages of self-assembled lipid nanoparticles containing internal nano-structures. Epidermal growth factor receptor (EGFR)-targeting, PEGylated lipid nanoparticles using phytantriol and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-PEG-maleimide amphiphiles were created. The self-assembled lipid nanoparticles presented here have internal lyotropic liquid crystalline nano-structures, verified by synchrotron small angle X-ray scattering and cryo-transmission electron microscopy, that offer the potential of high drug loading and enhanced cell penetration. Anti-EGFR Fab' fragments were conjugated to the surface of nanoparticles via a maleimide-thiol reaction at a high conjugation efficiency and retained specificity following conjugation to the nanoparticles. The conjugated nanoparticles were demonstrated to have high affinity for an EGFR target in a ligand binding assay.

Carbon nanotubes for stabilization of nanostructured lipid particles

Carbon nanotubes (CNTs) are increasingly studied for innovative biotechnological applications particularly where they are combined with essential biological materials like lipids. Lipids have been used earlier for enhancing the dispersibility of CNTs in aqueous solutions. Here we report a novel application of CNTs for stabilization of internally self-assembled nanostructured lipid particles of 2-5 μm size. Single-walled (pristine) as well as -OH and -COOH functionalized multi-walled CNTs were employed to produce nanostructured emulsions which stayed stable for months and could be re-dispersed after complete dehydration. Concentrations of CNTs employed for stabilization were very low; moreover CNTs were well-decorated with lipid molecules. These features contribute towards reducing their toxicity and improving biocompatibility for biomedical and pharmaceutical applications. Our approach paves the way for future development of combination therapies employing both CNTs and nanostructured lipid self-assembly together as carriers of different drugs.

An in vitro digestion test that reflects rat intestinal conditions to probe the importance of formulation digestion vs first pass metabolism in Danazol bioavailability from lipid based formulations

The impact of gastrointestinal (GI) processing and first pass metabolism on danazol oral bioavailability (BA) was evaluated after administration of self-emulsifying drug delivery systems (SEDDS) in the rat. Danazol absolute BA was determined following oral and intraduodenal (ID) administration of LFCS class IIIA medium chain (MC) formulations at high (SEDDSH-III) and low (SEDDSL-III) drug loading and a lipid free LFCS class IV formulation (SEDDS-IV). Experiments were conducted in the presence and absence of ABT (1-aminobenzotriazole) to evaluate the effect of first pass metabolism. A series of modified in vitro lipolysis tests were developed to better understand the in vivo processing of SEDDS in the rat. Danazol BA was low (<13%) following oral and ID administration of either SEDDS. Increasing drug loading, ID rather than oral administration, and administration of SEDDS-IV rather than SEDDS-III led to higher oral BA. After pretreatment with ABT, however, danazol oral BA significantly increased (e.g., 60% compared to 2% after administration of SEDDSL-III), no effect was observed on increasing drug loading, and differences between SEDDS-III and -IV were minimal. In vitro digestion models based on the lower enzyme activity and lower dilution conditions expected in the rat resulted in significantly reduced danazol precipitation from SEDDS-III or SEDDS-IV on initiation of digestion. At the doses administered here (4-8 mg/kg), the primary limitation to danazol oral BA in the rat was first pass metabolism, and the fraction absorbed was >45% after oral administration of SEDDS-III or SEDDS-IV. In contrast, previous studies in dogs suggest that danazol BA is less dependent on first pass metabolism and more sensitive to changes in formulation processing. In vitro digestion models based on likely rat GI conditions suggest less drug precipitation on formulation digestion when compared to equivalent dog models, consistent with the increases in in vivo exposure (fraction absorbed) seen here in ABT-pretreated rats.

From self-assembly fundamental knowledge to nanomedicine developments

This review highlights the key role of NMR techniques in demonstrating the molecular aspects of the self-assembly of surfactant molecules that nowadays constitute the basic knowledge which modern nanoscience relies on. The aim is to provide a tutorial overview. The story of a rigorous scientific approach to understand self-assembly in surfactant systems and biological membranes starts in the early seventies when the progresses of SAXRD and NMR technological facilities allowed to demonstrate the existence of ordered soft matter, and the validity of Tanford approach concerning self-assembly at a molecular level. Particularly, NMR quadrupolar splittings, NMR chemical shift anisotropy, and NMR relaxation of dipolar and quadrupolar nuclei in micellar solutions, microemulsions, and liquid crystals proved the existence of an ordered polar-apolar interface, on the NMR time scale. NMR data, rationalized in terms of the two-step model of relaxation, allowed to quantify the dynamic aspects of the supramolecular aggregates in different soft matter systems. In addition, NMR techniques allowed to obtain important information on counterion binding as well as on size of the aggregate through molecular self-diffusion. Indeed NMR self-diffusion proved without any doubt the existence of bicontinuous microemulsions and bicontinuous cubic liquid crystals, suggested by pioneering and brilliant interpretation of SAXRD investigations. Moreover, NMR self-diffusion played a fundamental role in the understanding of microemulsion and emulsion nanostructures, phase transitions in phase diagrams, and particularly percolation phenomena in microemulsions. Since the nineties, globalization of the knowledge along with many other technical facilities such as electron microscopy, particularly cryo-EM, produced huge progresses in surfactant and colloid science. Actually we refer to nanoscience: bottom up/top down strategies allow to build nanodevices with applications spanning from ICT to food technology. Developments in the applied fields have also been addressed by important progresses in theoretical skills aimed to understand intermolecular forces, and specific ion interactions. Nevertheless, this is still an open question. Our predictive ability has however increased, hence more ambitious targets can be planned. Nanomedicine represents a major challenging field with its main aims: targeted drug delivery, diagnostic, theranostics, tissue engineering, and personalized medicine. Few recent examples will be mentioned. Although the real applications of these systems still need major work, nevertheless new challenges are open, and perspectives based on integrated multidisciplinary approaches would enable both a deeper basic knowledge and the expected advances in biomedical field.

Formation of highly organized nanostructures during the digestion of milk

Nature's own emulsion, milk, consists of nutrients such as proteins, vitamins, salts, and milk fat with primarily triglycerides. The digestion of milk fats is the key to the survival of mammal species, yet it is surprising how little we understand this process. The lipase-catalyzed hydrolysis of dietary fats into fatty acids and monoglyceride is essential for efficient absorption of the fat by the enterocytes. Here we report the discovery of highly ordered geometric nanostructures during the digestion of dairy milk. Transitions from normal emulsion through a variety of differently ordered nanostructures were observed using time-resolved small-angle X-ray scattering on a high-intensity synchrotron source and visualized by cryogenic transmission electron microscopy. Water and hydrophilic molecules are transferred into the lipid phase of the milk particle, turning the lipid core gradually into a more hydrophilic environment. The formation of highly ordered lipid particles with substantial internal surface area, particularly in low-bile conditions, may indicate a compensating mechanism for maintenance of lipid absorption under compromised lipolysis conditions.

Lipid transfer in oil-in-water isasome emulsions: influence of arrested dynamics of the emulsion droplets entrapped in a hydrogel

The transfer kinetics of lipids between internally self-assembled droplets of O/W emulsions is studied. The droplets (isasomes) consist of various liquid-crystalline phases or W/O microemulsions stabilized by a polymeric stabilizer F127. The various internal phases were identified by the relative peak positions in the small-angle X-ray scattering (SAXS) curves. An arrested system composed of isasomes embedded in a gel matrix actually provides an additional possibility to control these systems in terms of the release of various host molecules. These experiments have been applied to examine the kinetics of the internal phase reorganization imposed by the lipids' release and uptake by the droplets embedded in a κ-carrageenan (KC) hydrogel network. Increasing the concentration of the gelling agent slows down the transfer from one droplet to the other through the aqueous phase. We examined the region where the free diffusion is stopped. i.e., the point where the system changes from the ergodic to the nonergodic state and the kinetics is essentially slowed down. This effect can be balanced by the addition of small amounts of free polymeric stabilizer, which speeds up the kinetics. This is even possible in the case of highly arrested dynamics of the emulsion droplets, as found for the highest KC hydrogel concentrations forming nonergodic systems.

Bicontinuous cubic liquid crystalline nanoparticles for oral delivery of Doxorubicin: implications on bioavailability, therapeutic efficacy, and cardiotoxicity

PURPOSE

The present study explores the potential of bicontinous cubic liquid crystalline nanoparticles (LCNPs) for improving therapeutic potential of doxorubicin.

METHODS

Phytantriol based Dox-LCNPs were prepared using hydrotrope method, optimized for various formulation components, process variables and lyophilized. Structural elucidation of the reconstituted formulation was performed using HR-TEM and SAXS analysis. The developed formulation was subjected to exhaustive cell culture experiments for delivery potential (Caco-2 cells) and efficacy (MCF-7 cells). Finally, in vivo pharmacokinetics, pharmacodynamic studies in DMBA induced breast cancer model and cardiotoxicity were also evaluated.

RESULTS

The reconstituted formulation exhibited Pn3m type cubic structure, evident by SAXS and posed stability in simulated gastrointestinal fluids and at accelerated stability conditions for 6 months. Dox-LCNPs revealed significantly higher cell cytotoxicity (16.23-fold) against MCF-7 cell lines as compared to free drug owing to its preferential localization in the vicinity of nucleus. Furthermore, Caco-2 cell experiments revealed formation of reversible "virtual pathways" in the cell membrane for Dox-LCNPs and hence posed significantly higher relative oral bioavailability (17.74-fold). Subsequently, Single dose of Dox-LCNPs (per oral) led to significant reduction in % tumor burden (~42%) as compared that of ~31% observed in case of Adriamycin® (i.v.) when evaluated in DMBA induced breast cancer model. Moreover, Dox induced cardiotoxicity was also found to be significantly lower in case of Dox-LCNPs as compared to clinical formulations (Adriamycin® and Lipodox®).

CONCLUSION

Incorporation of Dox in the novel LCNPs demonstrated improved antitumor efficacy and safety profile and can be a viable option for oral chemotherapy.

Paclitaxel loaded PEGylated gleceryl monooleate based nanoparticulate carriers in chemotherapy

A PEGylated drug delivery system of paclitaxel (PTX), based on glyceryl monooleate (GMO) was prepared by optimizing various parameters to explore its potential in anticancer therapy. The prepared system was characterized through polarized light microscopy, TEM, AFM and SAXS to reveal its liquid crystalline nature. As GMO based LCNPs exhibit high hemolytic toxicity and faster release of entrapped drug (66.2 ± 2.5% in 24 h), PEGylation strategy was utilized to increase the hemocompatibility (reduction in hemolysis from 60.3 ± 10.2 to 4.4 ± 1.3%) and control the release of PTX (43.6 ± 3.2% released in 24 h). The cytotoxic potential and cellular uptake was assessed in MCF-7 cell lines. Further, biodistribution studies were carried out in EAT (Ehrlich Ascites tumor) bearing mice using (99m)Tc-(Technetium radionuclide) labeled formulations and an enhanced circulation time and tumor accumulation (14 and 8 times, respectively) were observed with PEGylated carriers over plain ones, at 24 h. Finally, tumor growth inhibition experiment was performed and after 15 days, control group exhibited 15 times enhancement in tumor volume, while plain and PEGylated systems exhibited only 8 and 4 times enhancement, respectively, as compared to initial tumor volume. The results suggest that PEGylation enhances the hemocompatibility and efficacy of GMO based system that may serve as an efficient i.v. delivery vehicle for paclitaxel.

Structural characterization of lipidic systems under nonequilibrium conditions

This review covers recent studies on the characterization of the dynamics of lipidic nanostructures formed via self-assembly processes. The focus is placed on two main topics: First, an overview of advanced experimental small-angle X-ray scattering (SAXS) setups combined with various sample manipulation techniques including, for instance, stop-flow mixing or rapid temperature-jump perturbation is given. Second, our recent synchrotron SAXS findings on the dynamic structural response of gold nanoparticle-loaded vesicles upon exposure to an ultraviolet light source, the impact of rapidly mixing negatively charged vesicles with calcium ions, and in situ hydration-induced formation of inverted-type liquid-crystalline phases loaded with the local anesthetic bupivacaine are summarized. These in situ time-resolved experiments allow real-time monitoring of the dynamics of the structural changes and the possible formation of intermediate states in the millisecond to second range. The need for investigating self-assembled systems, mainly stimuli-responsive drug nanocarriers, under nonequilibrium conditions is discussed. For pharmaceutically relevant applications, it is essential to combine these investigations with appropriate in vitro and in vivo studies.

Immobilization of nanostructured lipid particles in polysaccharide films

Lipid-based equilibrium self-assemblies and their hierarchically ordered forms have been known since the last few decades. Related progress in colloids and interface science led the development of oil-in-water type internally self-assembled lipid particles, known as Isasomes, which have aroused great interest in biotechnological applications. These submicrometer-sized lipid particles are internally nanostructured in a form of various liquid-crystalline or microemulsion phases, which facilitate their loading with hydrophilic, hydrophobic, and amphiphilic molecules. Their internal nanostructure can also be finely tuned. Recently, it has been shown that Isasomes can be entrapped in thermoreversible polysaccharide hydrogels. Herein, we report on the immobilization of Isasomes in solid polysaccharide films prepared by drying particle-loaded κ-carrageenan and methyl cellulose-based hydrogels. These rather simple but elegant media facilitate the storage of these functional particles and their subsequent release by simple resolubilization in water and/or thermal transitions. Systematic rehydration studies of such Isasome-loaded films have shown that the Isasomes can be remobilized and/or recovered after resolubilization of loaded films, even after several months.

Real time evolution of liquid crystalline nanostructure during the digestion of formulation lipids using synchrotron small-angle X-ray scattering

The role of the digestion of lipids in facilitating absorption of poorly water-soluble compounds, such as vitamins, is not only an important nutritional issue but is increasingly being recognized as an important determinant in the effectiveness of lipid-based drug formulations. It has been known for some time that lipids often form complex liquid crystalline structures during digestion and that this may impact drug solubilization and absorption. However, until recently we have been unable to detect and characterize those structures in real time and have been limited in establishing the interplay between composition, digestion, and nanostructure. Here, we establish the use of an in vitro lipid digestion model used in conjunction with synchrotron small-angle X-ray scattering by first confirming its validity using known, nondigestible liquid crystalline systems, and then extend the model to study the real time evolution of nanostructure during the digestion of common formulation lipids. The formation of liquid crystalline structures from unstructured liquid formulations is discovered, and the kinetics of formation and dependence on composition is investigated.