Polymerization of cubosome and hexosome templates to produce complex microparticle shapes

Prismatic Block Copolymer Hexosomes

Cubosomes and hexosomes are recent solution morphologies with an ordered porous structure and are observed for lipids and amphiphilic block copolymers (BCPs) with high hydrophobic fractions. Whereas lipid hexosomes typically exhibit a prismatic shape, BCP hexosomes have so far only been observed as closed microspheres where inner channels are not connected to the surrounding medium. Here, we describe the formation of flat, prismatic BCP hexosomes with pronounced faceting and a highly ordered lattice of hexagonally packed channels. We assemble polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP or SV) into the hexosome framework using polystyrene-block-poly(4-vinylpyridine)-block-poly(tert-butyl methacrylate) (PS-b-P4VP-b-PT or SVT) as a macromolecular surfactant in low-χ solvents. During solvent exchange, SV-rich domains form through liquid-liquid phase separation, followed by solidification and confined assembly within these domains. Since the final solvent (acetone) has a very low χ parameter toward PS and P4VP (equaling low interfacial tension), solidification of the hexosome occurs under confinement conditions that we term "supersoft". The low interfacial tension allows the stabilization of the hexagonal-prismatic shape, which originates from the hexagonal lattice of channels. Increasing the interfacial tension with polar cosolvents at some point dominates the particle shape, resulting in deformation of prismatic BCP hexosomes into spinning-top structures. The use of low-χ solvents for confined assembly of BCPs may allow the formation of unusual particle shapes simply by tuning the polymer-solvent interaction.

A microfluidic platform for the controlled synthesis of architecturally complex liquid crystalline nanoparticles

Soft-matter nanoparticles are of great interest for their applications in biotechnology, therapeutic delivery, and in vivo imaging. Underpinning this is their biocompatibility, potential for selective targeting, attractive pharmacokinetic properties, and amenability to downstream functionalisation. Morphological diversity inherent to soft-matter particles can give rise to enhanced functionality. However, this diversity remains untapped in clinical and industrial settings, and only the simplest of particle architectures [spherical lipid vesicles and lipid/polymer nanoparticles (LNPs)] have been routinely exploited. This is partially due to a lack of appropriate methods for their synthesis. To address this, we have designed a scalable microfluidic hydrodynamic focusing (MHF) technology for the controllable, rapid, and continuous production of lyotropic liquid crystalline (LLC) nanoparticles (both cubosomes and hexosomes), colloidal dispersions of higher-order lipid assemblies with intricate internal structures of 3-D and 2-D symmetry. These particles have been proposed as the next generation of soft-matter nano-carriers, with unique fusogenic and physical properties. Crucially, unlike alternative approaches, our microfluidic method gives control over LLC size, a feature we go on to exploit in a fusogenic study with model cell membranes, where a dependency of fusion on particle diameter is evident. We believe our platform has the potential to serve as a tool for future studies involving non-lamellar soft nanoparticles, and anticipate it allowing for the rapid prototyping of LLC particles of diverse functionality, paving the way toward their eventual wide uptake at an industrial level.

Travoprost Liquid Nanocrystals: An Innovative Armamentarium for Effective Glaucoma Therapy

To date, the ophthalmic application of liquid crystalline nanostructures (LCNs) has not been thoroughly reconnoitered, yet they have been extensively used. LCNs are primarily made up of glyceryl monooleate (GMO) or phytantriol as a lipid, a stabilizing agent, and a penetration enhancer (PE). For optimization, the D-optimal design was exploited. A characterization using TEM and XRPD was conducted. Optimized LCNs were loaded with the anti-glaucoma drug Travoprost (TRAVO). Ex vivo permeation across the cornea, in vivo pharmacokinetics, and pharmacodynamic studies were performed along with ocular tolerability examinations. Optimized LCNs are constituted of GMO, Tween® 80 as a stabilizer, and either oleic acid or Captex® 8000 as PE at 25 mg each. TRAVO-LNCs, F-1-L and F-3-L, showed particle sizes of 216.20 ± 6.12 and 129.40 ± 11.73 nm, with EE% of 85.30 ± 4.29 and 82.54 ± 7.65%, respectively, revealing the highest drug permeation parameters. The bioavailability of both attained 106.1% and 322.82%, respectively, relative to the market product TRAVATAN®. They exhibited respective intraocular pressure reductions lasting for 48 and 72 h, compared to 36 h for TRAVATAN®. All LCNs exhibited no evidence of ocular injury in comparison to the control eye. The findings revealed the competence of TRAVO-tailored LCNs in glaucoma treatment and suggested the potential application of a novel platform in ocular delivery.

Recent advances in versatile inverse lyotropic liquid crystals

Owing to the rapid and significant progress in advanced materials and life sciences, nanotechnology is increasingly gaining in popularity. Among numerous bio-mimicking carriers, inverse lyotropic liquid crystals are known for their unique properties. These carriers make accommodation of molecules with varied characteristics achievable due to their complicated topologies. Besides, versatile symmetries of inverse LCNPs (lyotropic crystalline nanoparticles) and their aggregating bulk phases allow them to be applied in a wide range of fields including drug delivery, food, cosmetics, material sciences etc. In this review, in-depth summary, discussion and outlook for inverse lyotropic liquid crystals are provided.

Controlling phase and rheological behaviours of hexagonal lyotropic liquid crystalline templates for nanostructural administration and retention

Introducing polymerizable monomers into a binary hexagonal lyotropic liquid crystalline (LLC) template is a straightforward way for retaining the nanostructure but will decrease attractive intra- and inter- aggregate interactions. It is therefore crucial to understand the interfacial interactions at nanoscale after introducing the monomers but prior to polymerization. Herein, active species, poly (ethylene glycol) diacrylate (PEGDA) and 2-hydroxyethyl methacrylate (HEMA), were introduced into hexagonal LLC of dodecyl trimethylammonium bromide and water to explore the structural variables, dimensional stability, and dynamic property. At a proper volume ratio of PEGDA/HEMA (1/4), the system presents excellent homogeneity with a higher dimensional stability and lower dynamic property from rheological assessments, thereby achieving robust, free-standing, and transparent membranes after photo-polymerization. The unique property of the system also lies in the much lower order-disorder transition temperature (45 °C) that facilitates the reorientation of mesochannels. They are in contrast inaccessible for the ternary system only with PEGDA, though the nanostructure for both systems could be retained. An insight into subtle variations in these parameters allows us to prepare a polymerizable template possessing higher dimensional stability and suitable flexibility via molecular design, thereby enabling simultaneous structural alignment and retention for the development of functional nanomaterials.

Photo-crosslinked polymer cubosomes as a recyclable nanoreactor in organic solvents

Photo-crosslinked polymer cubosomes can work as robust nanoreactor under organic solvent condition without structural degradation.

Delineating penetration enhancer-enriched liquid crystalline nanostructures as novel platforms for improved ophthalmic delivery

Liquid crystalline nanostructures (LCNs), for instance cubosomes, have been widely used as a promising carrier for drug delivery through the last few years. To date, the ophthalmic application of these platforms was not well explored, and the effect of integrating penetration enhancers (PEs) into LCNs has not been investigated yet. Hence, the present work aimed coupling novel PEs into glyceryl monooleate-based cubosomes for ocular administration. Various enhancers viz, free fatty acids (oleic and linoleic acids), natural terpenes (D-limonene and cineole), medium-chain triglycerides (Captex® 1000 and Captex® 8000), mono-/di-glycerides (Capmul® MCM, Capmul® PG-8, and Capmul® PG-12) were tested at different amounts. The morphology of the formed LCNs was investigated using transmission electron microscopy (TEM). The crystallinity and thermal behavior studies were also conducted. The ocular safety of optimized formulae was tested via hen's egg test-chorioallantoic membrane (HET-CAM), rabbit eye Draize test, and histopathological examinations of ocular tissues. Confocal laser scanning microscopy (CLSM) was utilized to assess the enhanced permeation of fluorescently-labeled LCNs across corneal layers. The acceptable formulations exhibited relatively homogenous particle nano-sizes ranging from 139.26 ± 3.68 to 590.56 ± 24.86 nm carrying negative surface charges. TEM images, X-ray patterns and DSC thermograms demonstrated the influential effect of PEs in developing altered crystalline structures. The ocular compatibility of optimized LCNs was confirmed. The corneal distribution using CLSM proved the disseminated fluorescence intensity of LCNs enriched with oleic acid, Captex® 8000 and Capmul® MCM. Selected LCNs showed good physical stability upon storage and lyophilization. The results demonstrated the efficiency of tailored PE-modified LCNs in enhancing the ocular transport with no evidence of any irritation potential, and hence suggested their prospective applicability in ophthalmic drug delivery.

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

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