Advances in structural design of lipid-based nanoparticle carriers for delivery of macromolecular drugs, phytochemicals and anti-tumor agents

Protein-Eye View of the in Meso Crystallization Mechanism

For evolving biological and biomedical applications of hybrid protein?lipid materials, understanding the behavior of the protein within the lipid mesophase is crucial. After more than two decades since the invention of the in meso crystallization method, a protein-eye view of its mechanism is still lacking. Numerous structural studies have suggested that integral membrane proteins preferentially partition at localized flat points on the bilayer surface of the cubic phase with crystal growth occurring from a local fluid lamellar L_? phase conduit. However, studies to date have, by necessity, focused on structural transitions occurring in the lipid mesophase. Here, we demonstrate using small-angle neutron scattering that the lipid bilayer of monoolein (the most commonly used lipid for in meso crystallization) can be contrast-matched using deuteration, allowing us to isolate scattering from encapsulated peptides during the crystal growth process for the first time. During in meso crystallization, a clear decrease in form factor scattering intensity of the peptides was observed and directly correlated with crystal growth. A transient fluid lamellar L_? phase was observed, providing direct evidence for the proposed mechanism for this technique. This suggests that the peptide passes through a transition from the cubic Q_II phase, via an L_? phase to the lamellar crystalline L_c phase with similar layered spacing. When high protein loading was possible, the lamellar crystalline L_c phase of the peptide in the single crystals was observed. These findings show the mechanism of in meso crystallization for the first time from the perspective of integral membrane proteins.

A hydrodynamic flow focusing microfluidic device for the continuous production of hexosomes based on docosahexaenoic acid monoglyceride

Cubosomes and hexosomes are emerging platforms for drug and nutraceutical delivery applications. In addition to common high- and low-energy batch emulsification methods for the preparation of these nano-self-assemblies, it is important to introduce suitable microfluidic devices with a precision control of the flow parameters for their continuous production. Microfluidics has several advantages including cost effectiveness, short-production time, and control of the nanoparticle size and size distribution. In the present study, a hydrodynamic flow focusing polyimide microfluidic device was employed for the continuous production of hexosomes based on docosahexaenoic acid monoglyceride (MAG-DHA), in the presence of the stabilizer Pluronic F127. The size, structural, morphological and size characterizations of the continuously produced MAG-DHA nanodispersions were investigated through an integrated approach involving synchrotron small angle X-ray scattering, dynamic light scattering, and cryogenic transmission electron microscopy. We report on a simple process for the microfluidic synthesis of hexosomes with sizes ranging from 108 to 138 nm and relatively narrow size distributions as the polydispersity indices were in the range of 0.14-0.22. At the applied total volumetric flow rates (TFRs) ranging of 50-150 μL min^-1 and flow rate ratios (FRRs) of 10-30, it was evident from SAXS findings that ethanol has only a slight effect on the lattice parameter of the internal inverse hexagonal (H₂) phase of the produced hexosomes. In addition to hexosomes, cryo-TEM observations indicated the coexistence of vesicular structures and smaller nano-objects. The formation of these nano-objects that are most likely normal micelles was also confirmed by SAXS, particularly on increasing FRR from 10 to 20 or 30 at TFR of 150 μL min^-1. Taking into account the reported positive health effects of MAG-DHA, which is a long-chain omega-3 (ω-3) polyunsaturated fatty acid (PUFA) monoglyceride, in various disorders including cancer, the produced hexosomes are attractive for the delivery of ω-3 PUFAs, drugs, nutraceuticals, and their combinations.

Lipidic Liquid Crystalline Cubic Phases and Magnetocubosomes as Methotrexate Carriers

The release profiles of methotrexate, an anticancer drug, from the monoolein liquid crystalline cubic phases were studied. The cubic phases were used either in the form of a lipidic film deposited onto a glassy carbon electrode surface or in the dispersed form of magnetocubosomes, which are considered a prospective hybrid drug delivery system. Commonly, cubosomes or liposomes are employed, but not in the case of toxic methotrexate, known to block the receptors responsible for folate transport into the cells. The release profiles of the drug from the lipidic films were monitored electrochemically and described using the Higuchi model. They were also modified via changes in temperature; the release was faster, although it deviated from the model when the temperature was increased. Cubic phase nanoparticles (magnetocubosomes) containing hydrophobic magnetic nanoparticles placed in an alternating magnetic field of low frequency and amplitude, stimulated drug release from the suspension, which was monitored spectroscopically. These new biocompatible hybrid nanomaterials in the dispersed form allow to control the release of the drug at the appropriate sites, can be easily separated or relocated under external magnetic field and await further investigations of their in vitro cytotoxicity and in vivo biodistribution.

Lipid-Based Nanoparticles: Application and Recent Advances in Cancer Treatment

Many therapeutically active molecules are non-soluble in aqueous systems, chemically and biologically fragile or present severe side effects. Lipid-based nanoparticle (LBNP) systems represent one of the most promising colloidal carriers for bioactive organic molecules. Their current application in oncology has revolutionized cancer treatment by improving the antitumor activity of several chemotherapeutic agents. LBNPs advantages include high temporal and thermal stability, high loading capacity, ease of preparation, low production costs, and large-scale industrial production since they can be prepared from natural sources. Moreover, the association of chemotherapeutic agents with lipid nanoparticles reduces active therapeutic dose and toxicity, decreases drug resistance and increases drug levels in tumor tissue by decreasing them in healthy tissue. LBNPs have been extensively assayed in in vitro cancer therapy but also in vivo, with promising results in some clinical trials. This review summarizes the types of LBNPs that have been developed in recent years and the main results when applied in cancer treatment, including essential assays in patients.

Application of Solid Lipid Nanoparticles to Improve the Efficiency of Anticancer Drugs

Drug delivery systems have opened new avenues to improve the therapeutic effects of already-efficient molecules. Particularly, Solid Lipid Nanoparticles (SLNs) have emerged as promising nanocarriers in cancer therapy. SLNs offer remarkable advantages such as low toxicity, high bioavailability of drugs, versatility of incorporation of hydrophilic and lipophilic drugs, and feasibility of large-scale production. Their molecular structure is crucial to obtain high quality SLN preparations and it is determined by the relationship between the composition and preparation method. Additionally, SLNs allow overcoming several physiological barriers that hinder drug delivery to tumors and are also able to escape multidrug resistance mechanisms, characteristic of cancer cells. Focusing on cell delivery, SLNs can improve drug delivery to target cells by different mechanisms, such as passive mechanisms that take advantage of the tumor microenvironment, active mechanisms by surface modification of SLNs, and codelivery mechanisms. SLNs can incorporate many different drugs and have proven to be effective in different types of tumors (i.e., breast, lung, colon, liver, and brain), corroborating their potential. Finally, it has to be taken into account that there are still some challenges to face in the application of SLNs in anticancer treatments but their possibilities seem to be high.

Cubosomes: The Next Generation of Smart Lipid Nanoparticles?

Cubosomes are highly stable nanoparticles formed from the lipid cubic phase and stabilized by a polymer based outer corona. Bicontinuous lipid cubic phases consist of a single lipid bilayer that forms a continuous periodic membrane lattice structure with pores formed by two interwoven water channels. Cubosome composition can be tuned to engineer pore sizes or include bioactive lipids, the polymer outer corona can be used for targeting and they are highly stable under physiological conditions. Compared to liposomes, the structure provides a significantly higher membrane surface area for loading of membrane proteins and small drug molecules. Owing to recent advances, they can be engineered in vitro in both bulk and nanoparticle formats with applications including drug delivery, membrane bioreactors, artificial cells, and biosensors. This review outlines recent advances in cubosome technology enabling their application and provides guidelines for the rational design of new systems for biomedical applications.

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.

Advances of nanosystems containing cyclodextrins and their applications in pharmaceuticals

For many years, researchers have worked with supramolecular structures involving inclusion complexes with cyclodextrins. These studies have resulted in new commercially available drugs which have been of great benefit. More recently, studies using nanoparticles, including nanosystems containing cyclodextrins, have become a focus of academic research due to the versatility of the systems and their remarkable therapeutic potential. This review focuses on studies published between 2002 and 2018 involving nanosystems containing cyclodextrins. We consider the type of nanosystems, their importance in a health context, the physicochemical techniques used to show the quality of these systems and their potential for the development of novel pharmaceutical formulations. These have been developed in recent studies which have mainly been focusing on basic science with no clinical trials as yet being performed. This is important to note because it means that the studies do not include any toxicity tests. Despite this limitation, the characterization assays performed suggest that these new formulations may have therapeutic potential. However, more research is required to assess the efficacy and safety of these nanosystems.

From Structure to Function: pH-Switchable Antimicrobial Nano-Self-Assemblies

Stimuli-responsive nanocarriers based on lipid self-assemblies have the potential to provide targeted delivery of antimicrobial peptides, limiting their side effects while protecting them from degradation in the biological environments. In the present study, we design and characterize a simple pH-responsive antimicrobial nanomaterial, formed through the self-assembly of oleic acid (OA) with the human cathelicidin LL-37 as a model for an amphiphilic antimicrobial peptide. Colloidal transformations from core-shell cylindrical micelles with a cross-sectional diameter of ∼5.5 nm and a length of ∼23 nm at pH 7.0 to aggregates of branched threadlike micelles at pH 5.0 were detected using synchrotron small-angle X-ray scattering, cryogenic transmission electron microscopy, and dynamic light scattering. Biological in vitro assays using an Escherichia coli bacteria strain showed high antimicrobial activity of the positively charged LL-37/OA aggregates at pH 5.0, which was not caused by the pH conditions themselves. Contrary to that, negligible antimicrobial activity was observed at pH 7.0 for the negatively charged cylindrical micelles. The nanocarrier's ability to switch its biological activity "on" and "off" in response to changes in pH could be used to focus the antimicrobial peptides' action to areas of specific pH in the body. The presented findings contribute to the fundamental understanding of lipid-peptide self-assembly and may open up a promising strategy for designing simple pH-responsive delivery systems for antimicrobial peptides.

Antiadhesion effect of the C17 glycerin ester of isoprenoid-type lipid forming a nonlamellar liquid crystal

Postoperative adhesion is a relevant clinical problem that causes a variety of clinical complications after abdominal surgery. The objective of this study is to develop a liquid-type antiadhesion agent and evaluate its efficacy in preventing tissue adhesion in a rat peritoneal adhesion model. The liquid-type agent was prepared by submicron-sized emulsification of C17 glycerin ester (C17GE), squalene, pluronic F127, ethanol, and water with a high-pressure homogenizer. The primary component was C17GE, which is an amphiphilic lipid of one isoprenoid-type hydrophobic chain and can form two phases of self-assembly nonlamellar liquid crystals. The C17GE agent consisted of nanoparticles with an internal inverted hexagonal phase when evaluated by small-angle X-ray scattering (SAXS) and cryo-transmission electron microscopy (cryo-TEM). Upon contact with the biological tissue, this agent formed a thin membrane with a bioadhesive property. After this agent was applied to a sidewall injury of rats, it showed a percentage average of adhesion significantly less than that obtained with the Seprafilm® antiadhesion membrane in a rat model. Additionally, the retention of the agent prolonged at the applied site in the peritoneal cavity of rats. In conclusion, the C17GE agent is promising as an antiadhesion material. STATEMENT OF SIGNIFICANCE: Postoperative adhesion remains a common adverse effect. Although various materials have been investigated, there are few products commercially available to prevent adhesion. For the sheet-type agent, it is inconvenient to be applied through small laparotomy, especially in laparoscopic surgery. Additionally, the liquid-type agent currently used requires a complicated procedure to spray at the targeted site. Our liquid-type antiadhesion agent can form liquid crystals and act as a thin membrane-like physical barrier between the peritoneum and tissues to prevent adhesion. Indeed, the antiadhesion agent used in our present study significantly prevents adhesion compared with the antiadhesion membrane most used clinically. Moreover, our agent is highly stable by itself and easy to use in laparoscopic surgery, thus leading to a promising new candidate as an antiadhesion material.

Preparation of Messenger RNA Nanomicelles via Non-Cytotoxic PEG-Polyamine Nanocomplex for Intracerebroventicular Delivery: A Proof-of-Concept Study in Mouse Models

The specific delivery of messenger RNA (mRNA) is an excellent alternative to plasmid DNA, due to the latter’s potential risk for random integration into the host genome. In this study, we propose the use of specially tailored polyplex nanomicelles for the intravenous delivery of mRNA into the brain of mice. In brief, along the backbone of a polyaspartamide polymer that is terminated with a 42k Polyethylene glycol chain (PEG), aminoethylene-repeating groups (two, three, and four units, respectively) were conjugated to side-chains to promote electrostatic interactions with mRNA. This structural configuration would ultimately condense into a polyplex nanomicelle ranging between 24 and 34 nm, as was confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) while the chemistry of the synthesis was validated through NMR analysis. Subsequently, we hypothesized an important correlation pertaining to the role of hydrogen bonding between the interaction of polyamine and mRNA in due course. As a proof of concept, we encapsulated the luciferase (Luc2) mRNA as a reporter gene through in vitro transcription (IVT) and subsequently infused the polyplex nanomicelles into mouse brains via an intracerebroventricular (ICV) injection to bypass the blood–brain barriers (BBB). Data revealed that PEGylated polyplex nanomicelles possessing four repeating units of aminoethylene groups had exhibited the best Luc2 mRNA delivery efficiency with no significant immune response registered.

Citrem–phosphatidylcholine nano-self-assemblies: solubilization of bupivacaine and its role in triggering a colloidal transition from vesicles to cubosomes and hexosomes

In concentration- and lipid composition-dependent manners, bupivacaine triggers lamellar–nonlamellar phase transitions in citrem/soy phosphatidylcholine nanodispersions.

Vesicular self-assembly of a natural ursane-type dihydroxy-triterpenoid corosolic acid

Corosolic acid, a natural ursane-type 6-6-6-6-6 pentacyclic dihydroxy triterpenic acid, is a well known antidiabetic compound extractable from leaves of Psidium guajava. In this manuscript we have reported the self-assembly properties of corosolic acid in different liquids. The compound undergoes self-assembly to give vesicular morphology in different aqueous organic liquids. Supramolecular gels were also obtained in some aqueous binary liquids such as ethanol–water and dimethyl formamide–water. The morphology of the self-assemblies of corosolic acid were characterized by using different microscopic techniques like optical microscopy, field emission scanning electron microscopy, transmission electron microscopy, atomic force microscopy as well as XRD and FTIR studies. We also demonstrated the application of vesicular self-assemblies for the entrapment and release of fluorophores including an anticancer drug.

Corosolic acid, a natural ursane-type 6-6-6-6-6 pentacyclic dihydroxy triterpenic acid, self-assembled in binary liquid mixtures yielding vesicles.

Phenylboronic acid-modified polyamidoamine-mediated delivery of short GC rich DNA for hepatocarcinoma gene therapy

Phenylboronic acid was introduced on the surface of polyamidoamine to construct a derivative PP, which was further used as a tumor-targeting carrier for realizing the delivery of short GC rich DNA (GCD).

Cubosomes for topical delivery of the antimicrobial peptide LL-37

In this study, the use of cubosomes for topical delivery of the antimicrobial peptide (AMP) LL-37 was investigated. Topical delivery of AMPs is of great interest for treatment of skin infections caused by bacteria, such as Staphylococcus aureus. AMP containing cubosomes were produced by three different preparation protocols and compared: (i) pre-loading, where LL-37 was incorporated into a liquid crystalline gel, which thereafter was dispersed into nanoparticles, (ii) post-loading, where LL-37 was let to adsorb onto pre-formed cubosomes, and (iii) hydrotrope-loading, where LL-37 was incorporated during the spontaneously formed cubosomes in an ethanol/glycerol monooleate mixture. Particle size and size distribution were analyzed using dynamic light scattering (DLS), liquid crystalline structure by small angle x-ray scattering (SAXS) and release of LL-37 by a fluorescamine assay. Proteolytic protection of LL-37 as well as bactericidal effect after enzyme exposure was investigated. The skin irritation potential of cubosomes was examined by an in vitro epidermis model. Finally, the bacterial killing property of the cubosomes was examined by an ex vivo pig skin wound infection model with Staphylococcus aureus. Data showed that a high loading of LL-37 induced formation of vesicles in case of cubosomes prepared by sonication (pre-loading). No release of LL-37 was observed from the cubosomes, indicating strong association of the peptide to the particles. Proteolysis studies showed that LL-37 was fully protected against enzymatic attacks while associated with the cubosomes, also denoting strong association of the peptide to the particles. As a consequence, bactericidal effect after enzyme exposure remained, compared to pure LL-37 which was subjected to proteolysis. No skin irritation potential of the cubosomes was found, thus enabling for topical administration. The ex vivo wound infection model showed that LL-37 in pre-loaded cubosomes killed bacteria most efficient.

Recent progress in the engineering of multifunctional colloidal nanoparticles for enhanced photodynamic therapy and bioimaging

This up-to-date review summarizes the design and current fabrication strategies that have been employed in the area of mono- and multifunctional colloidal nanoparticles - nanocarriers well suited for photodynamic therapy (PDT) and diagnostic purposes. Rationally engineered photosensitizer (PS)-loaded nanoparticles may be achieved via either noncovalent (i.e., self-aggregation, interfacial deposition, interfacial polymerization, or core-shell entrapment along with physical adsorption) or covalent (chemical immobilization or conjugation) processes. These PS loading approaches should provide chemical and physical stability to PS payloads. Their hydrophilic surfaces, capable of appreciable surface interactions with biological systems, can be further modified using functional groups (stealth effect) to achieve prolonged circulation in the body after administration and/or grafted by targeting agents (such as ligands, which bind to specific receptors uniquely expressed on the cell surface) or stimuli (e.g., pH, temperature, and light)-responsive moieties to improve their action and targeting efficiency. These attempts may in principle permit efficacious PDT, combination therapies, molecular diagnosis, and - in the case of nanotheranostics - simultaneous monitoring and treatment. Nanophotosensitizers (nano-PSs) should possess appropriate morphologies, sizes, unimodal distributions and surface processes to be successfully delivered to the place of action after systemic administration and should be accumulated in certain tumors by passive and/or active targeting. Additionally, physically facilitating drug delivery systems emerge as a promising approach to enhancing drug delivery, especially for the non-invasive treatment of deep-seated malignant tissues. Recent advances in nano-PSs are scrutinized, with an emphasis on design principles, via the promising use of colloid chemistry and nanotechnology.

Effect of Piperine on Skin Permeation of Curcumin from a Bacterially Derived Cellulose-Composite Double-Layer Membrane for Transdermal Curcumin Delivery

Curcumin is a naturally occurring substance with various pharmacological activities. It has not been developed as a drug because of its low bioavailability due to its low solubility and absorption. Piperine is a natural enhancer that is popularly used to increase the absorption of curcumin in oral applications; however, it has not been applied for transdermal curcumin delivery. This study aims to develop a transdermal curcumin delivery system using piperine as a skin permeation enhancer in the form of composite double-layer membrane; the upper layer consisted of curcumin and the lower layer consisted of piperine. The amount of curcumin was fixed, but the amount of piperine varied at three levels from 1.96% to 7.41%. The composite membrane had moderate mechanical strength (15⁻22 MPa) with a good swelling degree (~435%). From an in vitro skin permeation study, piperine had the effect to increase the permeation of curcumin. The permeation rate was related to the amount of piperine. The composite membrane containing piperine at 7.41% could increase the permeation rate of curcumin by about 1.89 times compared with non-piperine contained membrane. Bacterially-derived cellulose containing curcumin and piperine may have the potential for transdermal curcumin delivery in order to improve curcumin's bioavailability.

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.

In situ phase transition of microemulsions for parenteral injection yielding lyotropic liquid crystalline carriers of the antitumor drug bufalin

In this work, we used the small angle X-ray scattering (SAXS) method for controlled preparation of in situ forming sustained-release carriers for the antitumor drug bufalin (BUF), which has very poor solubility and a considerable cardiotoxicity in a non-encapsulated state. To that aim, we exploited the pseudo-ternary phase diagram of an oil(O)/surfactant(S)/water(W) system containing medium chain capric/caprylic triglycerides (MCT) and a co-surfactant blend of Macrogol (15)-hydroxystearate (Solutol HS 15) and sorbitan monooleate (Span 80). Two compositions with different oil contents (sample B and C) were selected from the microemulsion region of the phase diagram in order to study the effect of the aqueous environment on their structural behavior. A phase transition from a microemulsion (ME) to a liquid crystalline phase (LC) was established by SAXS upon progressive dilution. The drug bufalin (BUF) was encapsulated in the microemulsions with low viscosity, whereas the release of the drug occurred from the in situ generated lamellar liquid crystalline structures. The formulations were characterized by SAXS, dynamic light scattering (DLS), cryogenic transmission electron microscopy (Cryo-TEM), rheology, drug loading and encapsulation efficiency, and in vitro release profiles. A correlation was suggested between the structures of the in situ phase-transition formed LCME formulations, the differences in their viscosities and drug release profiles. The performed cytotoxicity, cell apoptosis and pharmacokinetic experiments showed an enhanced bioavailability of BUF after encapsulation. These results suggest potential clinical applications for the obtained safe in situ phase-transition sustained-release formulations of BUF.

Cubic lyotropic liquid crystals as drug delivery carriers: Physicochemical and morphological studies

The self-assembly process of amphiphilic molecules into solvents results in different mesophases, such as inverse cubic and hexagonal that both belong to the wider category of lyotropic liquid crystals. The above mesophases can be further exploited upon the formation of liquid crystalline nanoparticles, cubosomes and hexosomes respectively, which may be utilized as drug delivery nanosystems, exhibiting major advantages. In the present study, liquid crystalline nanoparticles were prepared and evaluated in terms of morphology and physicochemical behavior. The goal of this study is to examine the effect of the different formulation parameters, as well as the effect of the different microenvironmental factors (temperature, ionic strength, pH, serum proteins presence) on their behavior. The physicochemical behavior and the morphology of the systems were investigated by X-Ray Diffraction (XRD), cryogenic-Transmission Electron Microscopy (cryo-TEM), fluorescence spectroscopy and a gamut of light scattering techniques. The formulation process was proved to influence strictly the physicochemical behavior of the prepared nanosystems. They presented colloidal stability over time and upon ionic strength increase, but they were affected by the presence of proteins and presented reversible structure alterations upon temperature increase. Their morphological structure and internal microenvironment, reflected by micropolarity and microfluidity, were also influenced by the formulation parameters.

Paclitaxel-Loaded Self-Assembled Lipid Nanoparticles as Targeted Drug Delivery Systems for the Treatment of Aggressive Ovarian Cancer

Chemotherapy using cytotoxic agents, such as paclitaxel (PTX), is one of the most effective treatments for advanced ovarian cancer. However, due to nonspecific targeting of the drug and the presence of toxic solvents required for dissolving PTX prior to injection, there are several serious side effects associated with this treatment. In this study, we explored self-assembled lipid-based nanoparticles as PTX carriers, which were able to improve its antitumour efficacy against ovarian cancer. The nanoparticles were also functionalized with epidermal growth factor receptor (EGFR) antibody fragments to explore the benefit of tumor active targeting. The formulated bicontinuous cubic- and sponge-phase nanoparticles, which were stabilized by Pluronic F127 and a lipid poly(ethylene glycol) stabilizer, showed a high capacity of PTX loading. These PTX-loaded nanoparticles also showed significantly higher cytotoxicity than a free drug formulation against HEY ovarian cancer cell lines in vitro. More importantly, the nanoparticle-based PTX treatments, with or without EGFR targeting, reduced the tumor burden by 50% compared to PTX or nondrug control in an ovarian cancer mouse xenograft model. In addition, the PTX-loaded nanoparticles were able to extend the survival of the treatment groups by up to 10 days compared to groups receiving free PTX or nondrug control. This proof-of-concept study has demonstrated the potential of these self-assembled lipid nanomaterials as effective drug delivery nanocarriers for poorly soluble chemotherapeutics, such as PTX.

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.

Rheology of Ultraswollen Bicontinuous Lipidic Cubic Phases

Rheological studies of liquid crystalline systems based on monopalmitolein and 5 or 8% of 1,2 distearoylphosphatidylglycerol are reported. Such cubic phases have been shown to possess unusually large water channels because of their ability of accommodating up to 80 wt % of water, a feature that renders these systems suitable for crystallizing membrane proteins with large extracellular domains. Their mechanical properties are supposed to be substantially different from those of traditional cubic phases. Rheological measurements were carried out on cubic phases of both Pn3 m and Ia3 d symmetries. It was verified that these ultraswollen cubic phases are less rigid than the normal cubic phases, with the Pn3 m being softer that the Ia3 d ones. Furthermore, for the Pn3 m case, the longest relaxation time is shown to decrease logarithmically with increasing surface area per unit volume, proving the critical role of the density of interfaces in establishing the macroscopic viscoelastic properties of the bicontinuous cubic phases.

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.

Synthesis, Self-Assembly, and Drug-Release Properties of New Amphipathic Liquid Crystal Polycarbonates

New amphiphilic liquid crystal (LC) polycarbonate block copolymers containing side-chain cholesteryl units were synthesized. Their structure, thermal stability, and LC phase behavior were characterized with Fourier transform infrared (FT-IR) spectrum, ¹H NMR, gel permeation chromatographic (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), polarizing optical microscope (POM), and XRD methods. The results demonstrated that the LC copolymers showed a double molecular arrangement of a smectic A phase at room temperature. With the elevating of LC unit content in such LC copolymers, the corresponding properties including decomposition temperature (T_d), glass temperature (T_g), and isotropic temperature (T_i) increased. The LC copolymers showed pH-responsive self-assembly behavior under the weakly acidic condition, and with more side-chain LC units, the self-assembly process was faster, and the formed particle size was smaller. It indicated that the self-assembly driving force was derived from the orientational ability of LC. The particle size and morphologies of self-assembled microspheres loaded with doxorubicin (DOX), together with drug release tracking, were evaluated by dynamic light scattering (DLS), SEM, and UV–vis spectroscopy. The results showed that DOX could be quickly released in a weakly acidic environment due to the pH response of the self-assembled microspheres. This would offer a new strategy for drug delivery in clinic applications.

Freeze-dried and re-hydrated liquid crystalline nanoparticles stabilized with disaccharides for drug-delivery of the plectasin derivative AP114 antimicrobial peptide

Liquid crystalline nanoparticles (LCNPs), e.g. cubosomes and hexosomes, are receiving more and more attraction as drug delivery vehicles. Dry powder formulation that forms LCNPs upon hydration can be advantageous to make new routes of administration accessible. In this work, we investigate use of three disaccharides (lactose, trehalose and sucrose) as protective matrices for glycerol monooleate based LCNP forming powders produced by freeze-drying. Phase behavior, particle size and size distributions at the different preparation steps were monitored by small angle x-ray scattering (SAXS) and dynamic light scattering (DLS). Particle appearance was imaged by cryogenic transmission electron microscopy (cryo-TEM). Moreover, the therapeutic relevant antimicrobial peptide AP114 (plectasin derivative) was incorporated in the formulations. Peptide encapsulation and release as well as in vitro antibacterial effect were investigated. Results showed that all freeze-dried powders did form particles with liquid crystalline structure upon hydration. However, a phase transition from the bicontinuous cubic Pn3m to the reversed hexagonal was observed, as a consequence of sugar addition and the freeze-drying procedure. Data indicates that trehalose is the preferred choice of lyo-protectant in order to maintain a mono-modal particle size distribution. In addition, antimicrobial activity of AP114-containing formulations was found to be highest for the formulation containing trehalose. The release kinetics of AP114 from the nanoparticles was strongly affected by the dimensions of the hexagonal phase. Larger dimension of the hexagonal phase, significantly improved the release of AP114 and antimicrobial activity of the formulation.

Towards clinical translation of ligand-functionalized liposomes in targeted cancer therapy: Challenges and opportunities

The development of therapeutic resistance to targeted anticancer therapies remains a significant clinical problem, with intratumoral heterogeneity playing a key role. In this context, improving the therapeutic outcome through simultaneous targeting of multiple tumor cell subtypes within a heterogeneous tumor is a promising approach. Liposomes have emerged as useful drug carriers that can reduce systemic toxicity and increase drug delivery to the tumor site. While clinically used liposomal drug formulations show marked therapeutic advantages over free drug formulations, ligand-functionalized liposomes that can target multiple tumor cell subtypes may further improve the therapeutic efficacy by facilitating drug delivery to a broader population of tumor cells making up the heterogeneous tumor tissue. Ligand-directed liposomes enable the so-called active targeting of cell receptors via surface-attached ligands that direct drug uptake into tumor cells or tumor-associated stromal cells, and so can increase the selectivity of drug delivery. Despite promising preclinical results demonstrating improved targeting and anti-tumor effects of ligand-directed liposomes, there has been limited translation of this approach to the clinic. Key challenges for translation include the lack of established methods to scale up production and comprehensively characterize ligand-functionalized liposome formulations, as well as the inadequate recapitulation of in vivo tumors in the preclinical models currently used to evaluate their performance. Herein, we discuss the utility of recent ligand-directed liposome approaches, with a focus on dual-ligand liposomes, for the treatment of solid tumors and examine the drawbacks limiting their progression to clinical adoption.

Multidisciplinary Approach to the Transfection of Plasmid DNA by a Nonviral Nanocarrier Based on a Gemini-Bolaamphiphilic Hybrid Lipid

A multidisciplinary strategy, including both biochemical and biophysical studies, was proposed here to evaluate the potential of lipid nanoaggregates consisting of a mixture of a gemini-bolaamphiphilic lipid (C6C22C6) and the well-known helper lipid 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE) to transfect plasmid DNA into living cells in an efficient and safe way. For that purpose, several experimental techniques were employed, such as zeta potential (phase analysis light scattering methodology), agarose gel electrophoresis (pDNA compaction and pDNA protection assays), small-angle X-ray scattering, cryo-transmission electron microscopy, atomic force microscopy, fluorescence-assisted cell sorting, luminometry, and cytotoxicity assays. The results revealed that the cationic lipid and plasmid offer only 70 and 30% of their nominal positive () and negative charges (), respectively. Upon mixing with DOPE, they form lipoplexes that self-aggregate in typical multilamellar Lα lyotropic liquid-crystal nanostructures with sizes in the range of 100-200 nm and low polydispersities, very suitably fitted to remain in the bloodstream and cross the cell membrane. Interestingly, these nanoaggregates were able to compact, protect (from the degrading effect of DNase I), and transfect two DNA plasmids (pEGFP-C3, encoding the green fluorescent protein, and pCMV-Luc, encoding luciferase) into COS-7 cells, with an efficiency equal or even superior to that of the universal control Lipo2000*, as long as the effective +/- charge ratio was maintained higher than 1 but reasonably close to electroneutrality. Moreover, this transfection process was not cytotoxic because the viability of COS-7 cells remained at high levels, greater than 80%. All of these features make the C6C22C6/DOPE nanosystem an optimal nonviral gene nanocarrier in vitro and a potentially interesting candidate for future in vivo experiments.

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.

Lyotropic Liquid-Crystalline Nanosystems as Drug Delivery Agents for 5-Fluorouracil: Structure and Cytotoxicity

Lyotropic cubic liquid-crystalline systems have received increasing attention due to their unique microstructural and physicochemical properties as efficient nanocarriers for drug delivery. We report the preparation and characterization of bulk phases and cubosome dispersions of phytantriol loaded with the anticancer drug 5-fluorouracil, in neutral and anionic forms. In both cases, a Pn3m cubic phase was observed. The phytantriol phase behavior can be influenced by the addition of ionic agents, and, to this purpose, a positively charged lipid, such as N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride salt (DOTAP), was included in the studied formulations. It was found to induce a variation of the spontaneous membrane curvature of the phytantriol lipid bilayer, generating a transition from the Pn3m to the Im3m cubic phase. When 5-fluorouracil, in its anionic form (5-FUs), was encapsulated in these latter systems, a further transition to the H_II hexagonal phase was observed as a consequence of the formation of a complex phytantriol/DOTAP/5-FUs. The physicochemical characterization was performed with various complementary techniques including synchrotron small-angle X-ray scattering, dynamic light scattering, and attenuated total reflection Fourier transform infrared and UV resonance Raman spectroscopies. Encapsulation of 5-fluorouracil in the corresponding nanodispersions was evaluated, and their in vitro cytotoxicity was assessed in MDA-MB-231 cell line. Phytantriol cubosomes containing 5-fluorouracil showed a higher toxicity compared with the bare drug solution, and hence they represent potential nanocarriers in the delivery of 5-fluorouracil for cancer therapy.

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.

Nanoscale clustering of the neurotrophin receptor TrkB revealed by super-resolution STED microscopy

The nanoscale organization of the tropomyosin-related kinase receptor type B (TrkB), a promising therapeutic target for severe neurodegenerative and psychiatric disorders, is examined by stimulated emission depletion (STED) microscopy using the deconvoluted gated STED option. The performed immunofluorescence nanoscopic subdiffraction imaging of the membrane receptor localization reveals that clusters of oligomeric TrkB states and randomly organized nanodomains are formed in the membranes of differentiated human neuroblastoma SH-SY5Y cells, which are studied as an in vitro model of neurodegeneration. Despite that the monomeric (isolated) states of the receptor cannot be distinguished from its dimeric forms in such images, TrkB receptor dimers (or couple of individual monomers) are visualized at super-resolution as single pixels in the magnified Huygens-deconvoluted gated STED images. The clusters of higher-order TrkB oligomers are of dynamic nature rather than of a fixed stoichiometry. The propensity for membrane protein clustering as well as the dissociation of the TrkB receptors nanodomains can be modulated by neurotherapeutic formulations containing ω-3 polyunsaturated docosahexaenoic acid (DHA). Nanomolar concentrations of DHA change the receptor topology and lead to disruption of the cluster phases. This result is of therapeutic importance for TrkB receptor availability upon ligand binding as DHA favours the mobility and the dynamic distribution of the protein populations in the cell membranes.