Amphiphilic brush polymers produced using the RAFT polymerisation method stabilise and reduce the cell cytotoxicity of lipid lyotropic liquid crystalline nanoparticles

Revolutionizing transdermal drug delivery: unveiling the potential of cubosomes and ethosomes

The area of drug delivery systems has witnessed significant advancements in recent years, with a particular focus on improving efficacy, stability, and patient compliance. Transdermal drug delivery offers numerous benefits compared to conventional methods of drug administration through the skin. It helps in avoiding gastric irritation, hepatic first-pass metabolism, and gastric degradation of the drug. It bypasses the gastrointestinal tract, eliminating the risk of first-pass metabolism and allowing drugs to be administered without being affected by pH, enzymes, or intestinal bacteria. Additionally, it allows for sustained release of the drug, is noninvasive, and enhances patient adherence to the treatment regimen. The transdermal drug delivery system (TDDS) can serve as an alternative route for drug administration in individuals who cannot tolerate oral medications, experience nausea, or are unconscious. When compared to intravenous, hypodermic, and other parenteral routes, TDDS stands out due to its ability to eliminate pain, reduce the risk of infection, and prevent disease transmission associated with needle reuse. Consequently, the overall patient compliance is significantly improved with the utilization of TDDS. Among the noteworthy developments are cubosomes and ethosomes, two distinct yet promising carriers that have garnered attention for their unique properties. In conclusion, this review synthesizes the current knowledge on cubosomes and ethosomes, shedding light on their individual strengths and potential synergies. The exploration of their application in various therapeutic areas underscores their versatility and establishes them as key players in the evolving landscape of drug delivery systems.

pH-Dependent Lyotropic Liquid Crystalline Mesophase and Ionization Behavior of Phytantriol-Based Ionizable Lipid Nanoparticles

Self-assembled lipid nanoparticles (LNPs), serving as essential nanocarriers in recent COVID-19 mRNA vaccines, provide a stable and versatile platform for delivering a wide range of biological materials. Notably, LNPs with unique inverse mesostructures, such as cubosomes and hexosomes, are recognized as fusogenic nanocarriers in the drug delivery field. This study delves into the physicochemical properties, including size, lyotropic liquid crystalline mesophase, and apparent pKa of LNPs with various lipid components, consisting of two ionizable lipids (ALC-0315 and SM-102) used in commercial COVID-19 mRNA vaccines and a well-known inverse mesophase structure-forming helper lipid, phytantriol (PT). Two partial mesophase diagrams are generated for both ALC-0315/PT LNPs and SM-102/PT LNPs as a function of two factors, ionizable lipid ratio (α, 0-100 mol%) and pH condition (pH 3-11). Furthermore, the impact of different LNP stabilizers (Pluronic F127, Pluronic F108, and Tween 80) on their pH-dependent phase behavior is evaluated. The findings offer insights into the self-assembled mesostructure and ionization state of the studied LNPs with potentially enhanced endosomal escape ability. This research is relevant to developing innovative next-generation LNP systems for delivering various therapeutics.

Regulating the structural polymorphism and protein corona composition of phytantriol-based lipid nanoparticles using choline ionic liquids

Lipid-based lyotropic liquid crystalline nanoparticles (LCNPs) face stability challenges in biological fluids during clinical translation. Ionic Liquids (ILs) have emerged as effective solvent additives for tuning the structure of LCNP's and enhancing their stability. We investigated the effect of a library of 21 choline-based biocompatible ILs with 9 amino acid anions as well as 10 other organic/inorganic anions during the preparation of phytantriol (PHY)-based LCNPs, followed by incubation in human serum and serum proteins. Small angle X-ray scattering (SAXS) results show that the phase behaviour of the LCNPs depends on the IL concentration and anion structure. Incubation with human serum led to a phase transition from the inverse bicontinuous cubic (Q2) to the inverse hexagonal (H2) mesophase, influenced by the specific IL present. Liquid chromatography-mass spectrometry (LC-MS) and proteomics analysis of selected samples, including PHY control and those with choline glutamate, choline hexanoate, and choline geranate, identified abundant proteins in the protein corona, including albumin, apolipoproteins, and serotransferrin. The composition of the protein corona varied among samples, shedding light on the intricate interplay between ILs, internal structure and surface chemistry of LCNPs, and biological fluids.

A Clinically-Achievable Injectable and Sprayable in Situ Lyotropic Liquid Crystalline Platform in Treating Hormone-Sensitive and Castration-Resistant Prostate Cancer

When it comes to long-acting injections, lyotropic liquid crystals (LLCs) are considered as an effective and powerful drug delivery technology due to their low manufacturing and injection difficulty, consistent releasing behaviors with low burst, as well as broadly applicable drug loading capacity. However, monoolein and phytantriol, as two widely used LLC-forming materials, may give rise to tissue cytotoxicity and undesired immunological responses, which may hinder the wide application of this technology. In this study, we opted for two ingredients, phosphatidylcholine and α-tocopherol, as carriers on account of their nature-obtainable and biocompatible qualities. By changing the ratios between them, we conducted research on crystalline types, nanosized structures, viscoelastic differences, characteristics of releasing behaviors, and in vivo safety. To fully exploit this in situ LLC platform with both injectability and sprayability, we focused on the treatment of both hormone-sensitive (HSPC) and castration-resistant prostate cancer (CRPC). For HSPC, we found that spraying leuprolide and a cabazitaxel-loaded LLC platform on the tumor bed after resection greatly reduced tumor metastatic rate and prolonged the survival time. Besides, for CRPC, our results demonstrated that although leuprolide (a kind of drug for castration) alone could hardly limit the progression of CRPC with low MHC-I expression, its combination with cabazitaxel in our LLC platform achieved a significantly better tumor-inhibiting and anti-recurrent efficacy than single cabazitaxel-loaded LLC platform, owing to enhanced CD4⁺ T cell infiltration in tumors and immune-potentiating cytokines. In conclusion, our dual-functional and clinically achievable strategy might provide a treating solution toward both HSPC and CRPC.

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.

Paclitaxel-loaded cubosome lipid nanocarriers stabilised with pH and hydrogen peroxide-responsive steric stabilisers as drug delivery vehicles

Responsive nanoparticle delivery systems hold great potential for next-generation chemotherapeutic treatment with reduced off-target side effects. In this work, we formulated responsive lipid-based cubosomes loaded with paclitaxel (PTX) as a model drug and stabilised by novel amphiphilic block copolymers (ABCs) containing the pH-responsive poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and/or the hydrogen peroxide (H₂O₂)-responsive poly(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl acrylate) (PTBA) blocks. The results showed that these cubosomes with a particle size of around 250 nm exhibited excellent PTX encapsulation efficiency of up to 60% and had the ability to control the release rate of the drug in response to pH and H₂O₂ changes. Specifically, compared to the physiological pH of 7.4, PTX was released faster from the cubosome carriers when exposed to pH 5.5 and/or 50 mM H₂O₂ conditions, which are pathological conditions found in a tumour microenvironment. In vitro cytotoxicity and cell uptake studies further investigated the cellular interactions of these cubosomes. It was found that cubosomes containing PTX had more toxic effects than the control free PTX sample. Compared to cubosomes stabilised by the non-responsive block copolymer Pluronic® F127, the ABC-stabilised cubosomes also had higher cell internalisation efficiency demonstrated by the cytoplasmic fluorescence intensities using confocal microscopy. These results demonstrated that ABCs containing responsive moieties can stabilise lipid cubosomes and enhance controlled release of poorly soluble chemotherapeutics and cellular uptake.

A Versatile Nanocarrier—Cubosomes, Characterization, and Applications

The impact of nanotechnology on the exponential growth of several research areas, particularly nanomedicine, is undeniable. The ability to deliver active molecules to the desired site could significantly improve the efficiency of medical treatments. One of the nanocarriers developed which has drawn researchers’ attention are cubosomes, which are nanosized dispersions of lipid bicontinuous cubic phases in water, consisting of a lipidic interior and aqueous domains folded in a cubic lattice. They stand out due to their ability to incorporate hydrophobic, hydrophilic, and amphiphilic compounds, their tortuous internal configuration that provides a sustained release, and the capacity to protect and safely deliver molecules. Several approaches can be taken to prepare this structure, as well as different lipids like monoolein or phytantriol. This review paper describes the different methods to prepare nanocarriers. As it is known, the physicochemical properties of nanocarriers are very important, as they influence their pharmacokinetics and their ability to incorporate and deliver active molecules. Therefore, an extensive characterization is essential to obtain the desired effect. As a result, we have extensively described the most common techniques to characterize cubosomes, particularly nanocarriers. The exceptional properties of the cubosomes make them suitable to be used in several applications in the biomedical field, from cancer therapeutics to imaging, which will be described. Taking in consideration the outstanding properties of cubosomes, their application in several research fields is envisaged.

Brush-like Polymer Prodrug with Aggregation-Induced Emission Features for Precise Intracellular Drug Tracking

In this study, a brush-like polymer with aggregation-induced emission (AIE) features was synthesized for drug delivery and intracellular drug tracking. The polymer consisting of tetraphenylethene (TPE) chain-end as well as oligo-poly (ethylene glycol) (PEG) and hydrazine functionalities was successfully synthesized through copper (0)-mediated reversible-deactivation radical polymerization (Cu0-mediated RDRP). Anticancer drug doxorubicin (DOX) was conjugated to the polymer and formed a prodrug named TPE-PEGA-Hyd-DOX, which contains 11% DOX. The hydrazone between DOX and polymer backbone is a pH-sensitive linkage that can control the release of DOX in slightly acidic conditions, which can precisely control the DOX release rate. The drug release of 10% after 96 h in normal cell environments compared with about 40% after 24 h in cancer cell environments confirmed the influence of the hydrazone bond. The ratiometric design of fluorescent intensities with peaks at 410 nm (emission due to AIE feature of TPE) and 600 nm (emission due to ACQ feature of DOX) provides an excellent opportunity for this product as a precise intracellular drug tracker. Cancer cells confocal microscopy showed negligible DOX solution uptake, but an intense green emission originated from prodrug uptake. Moreover, a severe red emission in the DOX channel confirmed a promising level of drug release from the prodrug in the cytoplasm. The merged images of cancer cells confirmed the high performance of the TPE-PEGA-Hyd-DOX compound in the viewpoints of cellular uptake and drug release. This polymer prodrug successfully demonstrates low cytotoxicity in healthy cells and high performance in killing cancer cells.

Cubosomes and Hexosomes as Novel Nanocarriers for Bioactive Compounds

Cubosomes and hexosomes are nanostructured liquid crystalline particles, known as biocompatible nanocarriers for drug delivery. In recent years, there has been good interest in using cubosomes and hexosomes for the delivery of bioactive compounds in functional foods. These systems feature thermodynamic stability, encapsulate both hydrophobic and hydrophilic substances, and have a high tolerance to environmental stresses and potential for controlled release. This review outlines the recent advances in cubosomes and hexosomes in the food industry, focusing on their structure, composition, formation mechanisms, and factors influencing phase transformation between cubosomes and hexosomes. The potential applications especially for the bioactive delivery are presented. The integration of cubosomes and hexosomes with other emerging encapsulation technologies such as surface coating, gelation, and incorporation of polymers are also discussed.

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

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

The Influence of Hydrophobic Blocks of PEO-Containing Copolymers on Glyceryl Monooleate Lyotropic Liquid Crystalline Nanoparticles for Drug Delivery

The investigation of properties of amphiphilic block copolymers as stabilizers for non-lamellar lyotropic liquid crystalline nanoparticles represents a fundamental issue for the formation, stability and upgraded functionality of these nanosystems. The aim of this work is to use amphiphilic block copolymers, not studied before, as stabilizers of glyceryl monooleate 1-(cis-9-octadecenoyl)-rac-glycerol (GMO) colloidal dispersions. Nanosystems were prepared with the use of poly(ethylene oxide)-b-poly(lactic acid) (PEO-b-PLA) and poly(ethylene oxide)-b-poly(5-methyl-5-ethyloxycarbonyl-1,3-dioxan-2-one) (PEO-b-PMEC) block copolymers. Different GMO:polymer molar ratios lead to formulation of nanoparticles with different size and internal organization, depending on the type of hydrophobic block. Resveratrol was loaded into the nanosystems as a model hydrophobic drug. The physicochemical and morphological characteristics of the prepared nanosystems were investigated by dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM), fast Fourier transform (FFT) analysis and X-ray diffraction (XRD). The studies allowed the description of the lyotropic liquid crystalline nanoparticles and evaluation of impact of copolymer composition on these nanosystems. The structures formed in GMO:block copolymer colloidal dispersions were compared with those discussed previously. The investigations broaden the toolbox of polymeric stabilizers for the development of this type of hybrid polymer/lipid nanostructures.

Novel Amphiphilic Block Copolymers for the Formation of Stimuli-Responsive Non-Lamellar Lipid Nanoparticles

Non-lamellar lyotropic liquid crystalline (LLC) lipid nanoparticles contain internal multidimensional nanostructures such as the inverse bicontinuous cubic and the inverse hexagonal mesophases, which can respond to external stimuli and have the potential of controlling drug release. To date, the internal LLC mesophase responsiveness of these lipid nanoparticles is largely achieved by adding ionizable small molecules to the parent lipid such as monoolein (MO), the mixture of which is then dispersed into nanoparticle suspensions by commercially available poly(ethylene oxide)-poly(propylene oxide) block copolymers. In this study, the Reversible Addition-Fragmentation chain Transfer (RAFT) technique was used to synthesize a series of novel amphiphilic block copolymers (ABCs) containing a hydrophilic poly(ethylene glycol) (PEG) block, a hydrophobic block and one or two responsive blocks, i.e., poly(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl acrylate) (PTBA) and/or poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA). High throughput small angle X-ray scattering studies demonstrated that the synthesized ABCs could simultaneously stabilize a range of LLC MO nanoparticles (vesicles, cubosomes, hexosomes, inverse micelles) and provide internal particle nanostructure responsiveness to changes of hydrogen peroxide (H2O2) concentrations, pH and temperature. It was found that the novel functional ABCs can substitute for the commercial polymer stabilizer and the ionizable additive in the formation of next generation non-lamellar lipid nanoparticles. These novel formulations have the potential to control drug release in the tumor microenvironment with endogenous H2O2 and acidic pH conditions.

Microfluidic technologies for the synthesis and manipulation of biomimetic membranous nano-assemblies

Microfluidics has been proposed as an attractive alternative to conventional bulk methods used in the generation of self-assembled biomimetic structures, particularly where there is a desire for more scalable production. The approach also allows for greater control over the self-assembly process, and parameters such as particle architecture, size, and composition can be finely tuned. Microfluidic techniques used in the generation of microscale assemblies (giant vesicles and higher-order multi-compartment assemblies) are fairly well established. These tend to rely on microdroplet templation, and the resulting structures have found use as comparmentalised motifs in artificial cells. Challenges in generating sub-micron droplets have meant that reconfiguring this approach to form nano-scale structures is not straightforward. This is beginning to change however, and recent technological advances have instigated the manufacture and manipulation of an increasingly diverse repertoire of biomimetic nano-assemblies, including liposomes, polymersomes, hybrid particles, multi-lamellar structures, cubosomes, hexosomes, nanodiscs, and virus-like particles. The following review will discuss these higher-order self-assembled nanostructures, including their biochemical and industrial applications, and techniques used in their production and analysis. We suggest ways in which existing technologies could be repurposed for the enhanced design, manufacture, and exploitation of these structures and discuss potential challenges and future research directions. By compiling recent advances in this area, it is hoped we will inspire future efforts toward establishing scalable microfluidic platforms for the generation of biomimetic nanoparticles of enhanced architectural and functional complexity.

Cuboplex-Mediated Nonviral Delivery of Functional siRNA to Chinese Hamster Ovary (CHO) Cells

Lipid nanoparticles of internal cubic symmetry, termed cuboplexes, are potential nonviral delivery vehicles for gene therapy due to their "topologically active" nature, which may enhance endosomal escape and improve delivery outcomes. In this study, we have used cationic cuboplexes, based on monoolein (MO) doped with a cationic lipid, for the encapsulation and delivery of antisense green fluorescent protein (GFP)-small interfering RNA (siRNA) into Chinese Hamster Ovary (CHO)-GFP cells. Agarose gel electrophoresis has confirmed the successful encapsulation of siRNA within cationic cubosomes, while synchrotron small-angle X-ray scattering (SAXS) demonstrated that the underlying cubic nanostructure of the particles was retained following encapsulation. The cationic cubosomes were shown to be reasonably nontoxic against the CHO-GFP cell line. Fluorescence-activated cell sorting (FACS) provided evidence of the successful transfection to CHO-GFP cells. Knockdown efficiency was strongly linked to the type of cationic lipid used, although all cubosomes had essentially the same internal nanostructure. The gene knockdown efficiency for some cationic cubosomes was shown to be higher than lipofectamine, which is a commercially available liposome-based formulation, while the controlled release of the siRNA from the cubosomes over a 72 h period was observed using confocal microscopy. This combination exemplifies the potential of cationic cuboplexes as a novel, nonviral, controlled-release delivery vector for siRNA.

Synthetic ionizable aminolipids induce a pH dependent inverse hexagonal to bicontinuous cubic lyotropic liquid crystalline phase transition in monoolein nanoparticles

A prospective class of materials for drug delivery is lyotropic liquid crystalline (LLC) nanoparticles, such as cubosomes and hexosomes. Efforts are being made to generate a pH dependent system, which exhibits slow release hexosomes (H₂) at physiological pH and relatively fast release cubosomes (Q₂) at acidic disease sites such as in various cancers and bacterial infection (pH ~ 5.5-6.5). Herein, we report the synthesis of nine ionizable aminolipids, which were doped into monoolein (MO) lipid nanoparticles. Using high throughput formulation and synchrotron small angle X-ray scattering (SAXS), the effects of aminolipid structure and concentration on the mesophase of MO nanoparticles at various pHs were determined. As the pH changed from neutral to acidic, mesophases, could be formed in an order L₂ (inverse micelles) → H₂ → Q₂. Specifically, systems with heterocyclic oleates exhibited the H₂ to Q₂ transition at pH 5.5-6.5. Furthermore, the phase transition pH could be fine-tuned by incorporating two aminolipids into the nanoparticles. Nanoparticles with a pH dependent phase transition as described in this study may be useful as drug delivery carriers for the treatment of cancers and certain bacterial infection.

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

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

Cubosomes stabilized by a polyphosphoester-analog of Pluronic F127 with reduced cytotoxicity

Lyotropic liquid crystalline nanoparticles with bicontinuous cubic internal nanostructure, known as cubosomes, have been proposed as nanocarriers in various medical applications. However, as these nanoparticles show a certain degree of cytotoxicity, particularly against erythrocytes, their application in systemic administrations is limited to date. Intending to produce a more biocompatible formulation, we prepared cubosomes for the first time stabilized with a biodegradable polyphosphoester-analog of the commonly used Pluronic F127. The ABA-triblock copolymer poly(methyl ethylene phosphate)-block-poly(propylene oxide)-block-poly(methyl ethylene phosphate) (PMEP-b-PPO-b-PMEP) was prepared by organocatalyzed ring-opening polymerization of MEP. The cytotoxic features of the resulting formulation were investigated against two different cell lines (HEK-293 and HUVEC) and human red blood cells. The response of the complement system was also evaluated. Results proved the poly(phosphoester)-based formulation was significantly less toxic than that prepared using Pluronic F127 with respect to all the tested cell lines and, more importantly, hemolysis assay and complement system activation tests demonstrated its very high hemocompatibility. The potentially biodegradable poly(phosphoester)-based cubosomes represent a new and versatile platform for preparation of functional and smart nanocarriers.

Multifunctional cubic liquid crystalline nanoparticles for chemo- and photodynamic synergistic cancer therapy

With the aim of engineering multifunctional nanoparticles useful for cancer therapy, a diketopyrrolopyrrole-porphyrin based photosensitizer was here conjugated to a block copolymer (Pluronic F108), and used to stabilize in water lipidic cubic liquid crystalline nanoparticles (cubosomes), also loaded with the antineoplastic agent docetaxel. The physicochemical characterization by SAXS, DLS, and cryo-TEM demonstrated that the formulation consisted of cubosomes, about 150 nm in size, possessing a bicontinuous cubic structure (space group Pn3m). The cellular imaging experiments proved that these nanoparticles localized in lysosomes and mitochondria, while cytotoxicity tests evidenced a slight but significant synergistic effect which, after irradiation, increased the toxicity induced by docetaxel alone, allowing further reduction of cell viability.

Monocytic Cell-Induced Phase Transformation of Circulating Lipid-Based Liquid Crystalline Nanosystems

Both lamellar and non-lamellar configurations are naturally present in bio-membranes, and the synthetic lipid-based liquid crystalline nano-assemblies, mimicking these unique structures, (including liposomes, cubosomes and hexosomes) are applicable in the controlled delivery of bioactives. However, it remains uncertain whether these nanosystems retain their original phase identity upon contact with blood circulating cells. This study highlights a novel biological cell flow-through approach at the synchrotron-based small angle X-ray scattering facility (bio-SAXS) to unravel their real-time phase evolution when incubated with human monocytic cells (THP-1) in suspension. Phytantriol-based cubosomes were identified to undergo monocytic cell-induced phase transformation from cubic to hexagonal phase periodicity. On the contrary, hexosomes exhibited time-dependent growth of a swollen hexagonal phase (i.e., larger lattice parameters) without displaying alternative phase characteristics. Similarly, liposomes remained undetectable for any newly evolved phase identity. Consequently, this novel in situ bio-SAXS study concept is valuable in delivering new important insights into the bio-fates of various lipid-based nanosystems under simulated human systemic conditions.

Engineering Swollen Cubosomes Using Cholesterol and Anionic Lipids

Dispersions of nonlamellar lipid membrane assemblies are gaining increasing interest for drug delivery and protein therapeutic application. A key bottleneck has been the lack of rational design rules for these systems linking different lipid species and conditions to defined lattice parameters and structures. We have developed robust methods to form cubosomes (nanoparticles with porous internal structures) with water channel diameters of up to 171 Å, which are over 4 times larger than archetypal cubosome structures. The water channel diameter can be tuned via the incorporation of cholesterol and the charged lipid DOPA, DOPG, or DOPS. We have found that large molecules can be incorporated into the porous cubosome structure and that these molecules can interact with the internal cubosome membrane. This offers huge potential for accessible encapsulation and protection of biomolecules and development of confined interfacial reaction environments.

Stimuli-Responsive Lyotropic Liquid Crystalline Nanosystems with Incorporated Poly(2-Dimethylamino Ethyl Methacrylate)-b-Poly(Lauryl Methacrylate) Amphiphilic Block Copolymer

There is an emerging need to evolve the conventional lyotropic liquid crystalline nanoparticles to advanced stimuli-responsive, therapeutic nanosystems with upgraded functionality. Towards this effort, typically used stabilizers, such as Pluronics^®, can be combined or replaced by smart, stimuli-responsive block copolymers. The aim of this study is to incorporate the stimuli-responsive amphiphilic block copolymer poly(2-(dimethylamino)ethyl methacrylate)-b-poly(lauryl methacrylate) (PDMAEMA-b-PLMA) as a stabilizer in lipidic liquid crystalline nanoparticles, in order to provide steric stabilization and simultaneous stimuli-responsiveness. The physicochemical and morphological characteristics of the prepared nanosystems were investigated by light scattering techniques, cryogenic-transmission electron microscopy (cryo-TEM), X-ray diffraction (XRD) and fluorescence spectroscopy. The PDMAEMA-b-PLMA, either individually or combined with Poloxamer 407, exhibited different modes of stabilization depending on the lipid used. Due to the protonation ability of PDMAEMA blocks in acidic pH, the nanoparticles exhibited high positive charge, as well as pH-responsive charge conversion, which can be exploited towards pharmaceutical applications. The ionic strength, temperature and serum proteins influenced the physicochemical behavior of the nanoparticles, while the polymer concentration differentiated their morphology; their micropolarity and microfluidity were also evaluated. The proposed liquid crystalline nanosystems can be considered as novel and attractive pH-responsive drug and gene delivery nanocarriers due to their polycationic content.

Janus particles: recent advances in the biomedical applications

Janus particles, which are named after the two-faced Roman god Janus, have two distinct sides with different surface features, structures, and compositions. This asymmetric structure enables the combination of different or even incompatible physical, chemical, and mechanical properties within a single particle. Much effort has been focused on the preparation of Janus particles with high homogeneity, tunable size and shape, combined functionalities, and scalability. With their unique features, Janus particles have attracted attention in a wide range of applications such as in optics, catalysis, and biomedicine. As a biomedical device, Janus particles offer opportunities to incorporate therapeutics, imaging, or sensing modalities in independent compartments of a single particle in a spatially controlled manner. This may result in synergistic actions of combined therapies and multi-level targeting not possible in isotropic systems. In this review, we summarize the latest advances in employing Janus particles as therapeutic delivery carriers, in vivo imaging probes, and biosensors. Challenges and future opportunities for these particles will also be discussed.

Nature-Inspired Design and Application of Lipidic Lyotropic Liquid Crystals

Amphiphilic lipids aggregate in aqueous solution into a variety of structural arrangements. Among the plethora of ordered structures that have been reported, many have also been observed in nature. In addition, due to their unique morphologies, the hydrophilic and hydrophobic domains, very high internal interfacial surface area, and the multitude of possible order-order transitions depending on environmental changes, very promising applications have been developed for these systems in recent years. These include crystallization in inverse bicontinuous cubic phases for membrane protein structure determination, generation of advanced materials, sustained release of bioactive molecules, and control of chemical reactions. The outstanding diverse functionalities of lyotropic liquid crystalline phases found in nature and industry are closely related to the topology, including how their nanoscopic domains are organized. This leads to notable examples of correlation between structure and macroscopic properties, which is itself central to the performance of materials in general. The physical origin of the formation of the known classes of lipidic lyotropic liquid crystalline phases, their structure, and their occurrence in nature are described, and their application in materials science and engineering, biology, medical, and pharmaceutical products, and food science and technology are exemplified.

Probing cell-nanoparticle (cubosome) interactions at the endothelial interface: do tissue dimension and flow matter?

In the research field of nanostructured systems for biomedical applications, increasing attention has been paid to using biomimetic, dynamic cellular models to adequately predict their bio-nano behaviours. This work specifically evaluates the biointeractions of nanostructured lipid-based particles (cubosomes) with human vascular cells from the aspects of tissue dimension (conventional 2D well plate versus 3D dynamic tubular vasculature) and shear flow effect (static, venous and arterial flow-mimicking conditions). A glass capillary-hosted, 3D tubular endothelial construct was coupled with circulating luminal fluid flow to simulate the human vascular systems. In the absence of fluid flow, the degree of cell-cubosome association was not significantly different between the 2D planar and the 3D tubular systems. Under flow conditions simulating venous (0.8 dynes per cm²) and arterial (10 dynes per cm²) shear stresses, the cell-cubosome association notably declined by 50% and 98%, respectively. This highlights the significance of shear-guided biointeractions of non-targeted nanoparticles in the circulation. Across all 2D and 3D cellular models with and without flow, cubosomes had little effect on the cell-cell contact based on the unchanged immunoexpression of the endothelial-specific intercellular junction marker PECAM-1. Interestingly, there were dissimilar nanoparticle distribution patterns between the 2D planar (showing discrete punctate staining) and the 3D tubular endothelium (with a more diffused, patchy fashion). Taken together, these findings highlight the importance of tissue dimension and shear flow in governing the magnitude and feature of cell-nanoparticle interactions.

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.

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.

Self-Assembled Nanostructured Lipid Systems: Is There a Link between Structure and Cytotoxicity?

Self-assembly of lipid-based liquid crystalline (LLC) nanoparticles is a formulation art arising from the hydrophilic-lipophilic qualities and the geometric packing of amphiphilic lipid molecules in an aqueous environment. The diversity of commercialized amphiphilic lipids and an increased understanding of the physicochemical factors dictating their membrane curvature has enabled versatile architectural design and engineering of LLC nanoparticles. While these exotic nanostructured materials are hypothesized to form the next generation of smart therapeutics for a broad field of biomedical applications, biological knowledge particularly on the systemic biocompatibility or cytotoxicity of LLC materials remains unclear. Here, an overview on the interactions between LLCs of different internal nanostructures and biological components (including soluble plasma constituents, blood cells, and isolated tissue cell lines) is provided. Factors affecting cell-nanoparticle tolerability such as the type of lipids, type of steric stabilizers, nanoparticle surface charges, and internal nanostructures (or lipid phase behaviors) are elucidated. The mechanisms of cellular uptake and lipid transfer between neighboring membrane domains are also reviewed. A critical analysis of these studies sheds light on future strategies to transform LLC materials into a viable therapeutic entity ideal for internal applications.

Preparation of Nanostructured Lipid Drug Delivery Particles Using Microfluidic Mixing

BACKGROUND

Cubosomes are highly ordered self-assembled lipid particles analogous to liposomes, but with internal liquid crystalline structure. They are receiving interest as stimuli responsive delivery particles, but their preparation typically requires high energy approaches such as sonication which is not favourable in many applications.

OBJECTIVE

Here we investigated the impact of microfluidic preparation on particle size distribution and internal structure of cubosomes prepared from two different lipid systems, phytantriol and glyceryl monooleate (GMO).

METHODS

The impact of relative flow rates of the aqueous and organic streams, the total flow rate and temperature were investigated in a commercial microfluidic system. The particle size distribution and structure were measured using dynamic light scattering and small angle X-ray scattering respectively.

RESULTS

Phytantriol based particles were robust to different processing conditions, while cubosomes formed using GMO were more sensitive to composition both locally and globally, which reflects their preparation using other techniques.

CONCLUSION

Thus, in summary microfluidics represents a reproducible and versatile method to prepare complex lipid particle dispersions such as cubosomes.

Monoolein-based nanoparticles for drug delivery to the central nervous system: A platform for lysosomal storage disorder treatment

Lysosomal Storage Disorders (LSDs) are characterized by an abnormal accumulation of substrates within the lysosome and comprise more than 50 genetic disorders with a frequency of 1:5000 live births. Nanotechnology may be a promising way to circumvent the drawbacks of the current therapies for lysosomal diseases. The blood circulation time and bioavailability of the enzymes or drugs could be improved by inserting them in nanocarriers, which could decrease and/or avoid the need of frequent intravenous infusions along with the minimization or elimination of associated immunogenic responses. Considering the exposed, we aimed to build monoolein-based nanoparticles stabilized by polysorbate 80 as a smart platform able to reach the central nervous system (CNS) to deliver drugs or enzymes inside lysosomes. We developed and characterized the nanoparticles by dynamic light scattering (DLS), small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (Cryo-TEM). The nanoparticles showed a diameter of 115 nm, which is compatible with in vivo application. The SAXS patterns of the formulations displayed a single broad correlation peak that was fitted to the Teubner-Strey model confirming that disordered bicontinuous structures were obtained. Cryo-TEM images corroborated this finding and showed nanoparticles with size values that are similar to those determined by DLS. Furthermore, the nanoparticles did not present cytotoxicity when they were incubated with human fibroblasts, and demonstrated hemolytic activity proportional to the negative control, proving to be safe for parenteral administration. Through the use of a fluorescent dye to track the nanoparticles inside the cell, we demonstrated that they reached lysosomes after 1 h of treatment. More interestingly, the fluorescent dye was detected in the CNS of mice just after 3 h of treatment. The nanoparticles show great potential to improve the treatment of LSDs with brain impairment, acting as a smart platform to targeted delivery of drugs or enzymes.

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.

Manipulating the Ordered Nanostructure of Self-Assembled Monoolein and Phytantriol Nanoparticles with Unsaturated Fatty Acids

Mesophase structures of self-assembled lyotropic liquid crystalline nanoparticles are important factors that directly influence their ability to encapsulate and release drugs and their biological activities. However, it is difficult to predict and precisely control the mesophase behavior of these materials, especially in complex systems with several components. In this study, we report the controlled manipulation of mesophase structures of monoolein (MO) and phytantriol (PHYT) nanoparticles by adding unsaturated fatty acids (FAs). By using high throughput formulation and small-angle X-ray scattering characterization methods, the effects of FAs chain length, cis-trans isomerism, double bond location, and level of chain unsaturation on self-assembled systems are determined. Additionally, the influence of temperature on the phase behavior of these nanoparticles is analyzed. We found that in general, the addition of unsaturated FAs to MO and PHYT induces the formation of mesophases with higher Gaussian surface curvatures. As a result, a rich variety of lipid polymorphs are found to correspond with the increasing amounts of FAs. These phases include inverse bicontinuous cubic, inverse hexagonal, and discrete micellar cubic phases and microemulsion. However, there are substantial differences between the phase behavior of nanoparticles with trans FA, cis FAs with one double bond, and cis FAs with multiple double bonds. Therefore, the material library produced in this study will assist the selection and development of nanoparticle-based drug delivery systems with desired mesophase.

Non-lamellar lyotropic liquid crystalline nanoparticles enhance the antibacterial effects of rifampicin against Staphylococcus aureus

The fight against infection in an era of emerging antibiotic resistant bacteria is one of the grandest scientific challenges facing society today. Nano-carriers show great promise in improving the antibacterial activity of antibiotics as they are able to enhance their solubility, provide sustained release and reduce toxic side effects via specifically targeting infection sites. Here, we investigate the antibacterial effect of two lipidic nano-carriers that contain the poorly soluble antibiotic rifampicin in their bilayers. One nanoparticle is assembled solely from the lipid monoolein, thus is neutral at physiological pH and the other contains a mixture of monoolein and the cationic lipid N-[1-(2,3-Dioleoyloxy)propyl]-N,N,N-trimethylammonium methyl-sulfate (DOTAP), thus is positively charged. Our results show that rifampicin-loaded nanoparticles reduce the minimum inhibitory concentration against Staphylococcus aureus compared to rifampicin alone, however this reduction was most pronounced for the positively charged nanoparticles. Fluorescent microscopy revealed binding of all nanoparticles to the bacteria and enhanced binding was observed for the charged nanoparticles. This suggests that the cationic lipids promote electrostatic interactions with the negatively charged bacterial membrane. Förster resonance energy transfer demonstrated that the cationic charged nanoparticles were able to fuse with bacterial membranes whilst atomic force microscopy and transmission electron microscopy revealed structural damage to the bacterial membranes caused by the nanoparticles. Significantly, we identified a concentration window in which the nanoparticles exhibited antibacterial activity while not affecting HeLa and CHO cell viability. This ability to improve the efficacy of antibiotics without affecting their eukaryotic cytotoxicity is of significant importance for future development of nanomedicine based strategies to combat infections.

Artificial cerium-based proenzymes confined in lyotropic liquid crystals: synthetic strategy and on-demand activation

The artificial proenzyme concept for ultra-small cerium-based nanoparticles: the on-demand activation of inactive nanoparticles to mimic the activity of superoxide dismutase.

Clickable Cubosomes for Antibody-Free Drug Targeting and Imaging Applications

The combination of copper-free click chemistry with metabolic labeling offers new opportunities in drug delivery. The objective of this study was to determine whether cubosomes functionalized with azide or dibenzocyclooctyne (DBCO) groups are able to undergo copper-free click chemistry with a strained cyclooctyne or azide, respectively. Phytantriol-based cubosomes were functionalized using phospholipids bearing an azide or DBCO group. The modified cubosome dispersions were characterized using dynamic light scattering, cryo-TEM, and small-angle X-ray scattering. The efficiency of "clickability" was assessed by reacting the cubosomes with a complementary dye and determining bound and unbound dye via size exclusion chromatography. The clickable cubosomes reacted specifically and efficiently with a click-Cy5 dye with minor changes to the size, shape, and structure of the cubosomes. This indicates that cubosomes can retain their unique internal structure while participating in copper-free click chemistry. This proof of concept study paves the way for the use of copper-free click chemistry and metabolic labeling with cubosomes for targeted drug delivery and imaging.

Self-assembled Lyotropic Liquid Crystalline Phase Behavior of Monoolein-Capric Acid-Phospholipid Nanoparticulate Systems

We report here the lyotropic liquid crystalline phase behavior of two lipid nanoparticulate systems containing mixtures of monoolein, capric acid, and saturated diacyl phosphatidylcholines dispersed by the Pluronic F127 block copolymer. Synchrotron small-angle X-ray scattering (SAXS) was used to screen the phase behavior of a library of lipid nanoparticles in a high-throughput manner. It was found that adding capric acid and phosphatidylcholines had opposing effects on the spontaneous membrane curvature of the monoolein lipid layer and hence the internal mesophase of the final nanoparticles. By varying the relative concentration of the three lipid components, we were able to establish a library of nanoparticles with a wide range of mesophases including at least the inverse bicontinuous primitive and double diamond cubic phases, the inverse hexagonal phase, the fluid lamellar phase, and possibly other phases. Furthermore, the in vitro cytotoxicity assay showed that the endogenous phospholipid-containing nanoparticles were less toxic to cultured cell lines compared to monoolein-based counterparts, improving the potential of the nonlamellar lipid nanoparticles for biomedical applications.

Dual-modality NIRF-MRI cubosomes and hexosomes: High throughput formulation and in vivo biodistribution

Engineered nanoparticles with multiple complementary imaging modalities are of great benefit to the rapid treatment and diagnosis of disease in various organs. Herein, we report the formulation of cubosomes and hexosomes that carry multiple amphiphilic imaging contrast agents in their self-assembled lipid bilayers. This is the first report of the use of both near infrared fluorescent (NIRF) imaging and gadolinium lipid based magnetic resonance (MR) imaging modalities in cubosomes and hexosomes. High-throughput screening was used to rapidly optimize formulations with desirable nano-architectures and low in vitro cytotoxicity. The dual-modal imaging nanoparticles in vivo biodistribution and organ specific contrast enhancement were then studied. The NIRF in vivo imaging results indicated accumulation of both cubosomes and hexosomes in the liver and spleen of mice up to 20h post-injection. Remarkably, the biodistribution of the nanoparticle formulations was affected by the mesophase (i.e. cubic or hexagonal), a finding of significant importance for the future use of these compounds, with hexosomes showing higher accumulation in the spleen than the liver compared to cubosomes. Furthermore, in vivo MRI data of animals injected with either type of lyotropic liquid crystal nanoparticle displayed enhanced contrast in the liver and spleen.