Twofold light and magnetic responsive behavior in nanoparticle-lyotropic liquid crystal systems

Alignment of lyotropic liquid crystals using magnetic nanoparticles improves ionic transport through built-in peptide ion channels

HYPOTHESIS

We hypothesize that simultaneous incorporation of ion channel peptides (in this case, potassium channel as a model) and hydrophobic magnetite Fe3O4 nanoparticles (hFe3O4NPs) within lipidic hexagonal mesophases, and aligning them using an external magnetic field can significantly enhance ion transport through lipid membranes.

EXPERIMENTS

In this study, we successfully characterized the incorporation of gramicidin membrane ion channels and hFe3O4NPs in the lipidic hexagonal structure using SAXS and cryo-TEM methods. Additionally, we thoroughly investigated the conductive characteristics of freestanding films of lipidic hexagonal mesophases, both with and without gramicidin potassium channels, utilizing a range of electrochemical techniques, including impedance spectroscopy, normal pulse voltammetry, and chronoamperometry.

FINDINGS

Our research reveals a state-of-the-art breakthrough in enhancing ion transport in lyotropic liquid crystals as matrices for integral proteins and peptides. We demonstrate the remarkable efficacy of membranes composed of hexagonal lipid mesophases embedded with K+ transporting peptides. This enhancement is achieved through doping with hFe3O4NPs and exposure to a magnetic field. We investigate the intricate interplay between the conductive properties of the lipidic hexagonal structure, hFe3O4NPs, gramicidin incorporation, and the influence of Ca2+ on K+ channels. Furthermore, our study unveils a new direction in ion channel studies and biomimetic membrane investigations, presenting a versatile model for biomimetic membranes with unprecedented ion transport capabilities under an appropriately oriented magnetic field. These findings hold promise for advancing membrane technology and various biotechnological and biomedical applications of membrane proteins.

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.

Vancomycin Loaded Glycerol Monooleate Liquid Crystalline Phases Modified with Surfactants

The influence of two tuning agents, polyglycerol ester (PE) and triblock copolymer (TC), on the properties of glycerol monooleate (MO) liquid crystalline phase (LCP) was investigated to achieve the therapeutic concentration of vancomycin hydrochloride (VHCl) into the eye, topically during 60 min (1 h) and intravitreally during 2880 min (48 h). Different techniques were used to elucidate the impact of surfactants on the structure of the LCP: polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), and in vitro release tests I and II (simulating local and intravitreal application in the eye). The structure analysis by SAXS depicts that the inclusion of PE into the MO LCP provided partial transition of a hexagonal phase into a lamellar phase, and TC induced a partial transition of a hexagonal phase into an LCP which identification was difficult. The LCP modulated with PE and TC demonstrated different VHCl's release patterns and were evaluated by comparing our release data with the literature data. The comparison indicated that the LCP modulated with 30% w/w PE could be a promising VHCl delivery system intravitreally during 2880 min.

Nanoparticles and organized lipid assemblies: from interaction to design of hybrid soft devices

This contribution reviews the state of art on hybrid soft matter assemblies composed of inorganic nanoparticles (NP) and lamellar or non-lamellar lipid bilayers. After a short outline of the relevant energetic contributions, we address the interaction of NPs with synthetic lamellar bilayers, meant as cell membrane mimics. We then review the design of hybrid nanostructured materials composed of lipid bilayers and some classes of inorganic NPs, with particular emphasis on the effects on the amphiphilic phase diagram and on the additional properties contributed by the NPs. Then, we present the latest developments on the use of lipid bilayers as coating agents for inorganic NPs. Finally, we remark on the main achievements of the last years and our vision for the development of the field.

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.

Impact of Molecular Partitioning and Partial Equilibration on the Estimation of Diffusion Coefficients from Release Experiments

The present work addresses the effect of partial equilibration and molecular partitioning on the interpretation of release experiments. In this regard, it is shown how release profiles and the values of extracted transport parameters are affected by the time protocol chosen for sample collection by considering a series of experiments where the latter is systematically varied. Caffeine is investigated as a main model drug because of its similar affinity for water and lipids, while monolinolein-based lipid cubic phases are chosen as host matrices because of their wide employment in release studies. Our findings point to a progressive decline in diffusion rate upon increasing the time step, that is, the gap in time between two consecutive pickups, which is a signature of increasing equilibration of caffeine concentration between the lipidic mesophase and the water phase. Furthermore, the amount of released molecules at the first pickup displays negligible changes for large time steps, indicating complete equilibration in such cases. A model is introduced based on Fick's diffusion which goes beyond the assumption of perfect-sink conditions, a common feature of the typical theoretical approaches hitherto developed. The model is shown to account quantitatively for the experimental data and is subsequently employed to clarify the interplay of the adopted release protocol with the various transport parameters in determining the final outcome of the release process. Particularly, two additional molecular drugs are considered, namely glucose and proflavine, which are, respectively, more hydrophilic and hydrophobic than caffeine, thus allowing elucidating the role of molecular partitioning.

Reversible Switching of the Magnetic Orientation of Titanate Nanosheets by Photochemical Reduction and Autoxidation

Optical properties of aqueous colloidal dispersions of 2D electrolytes, if their aspect ratios are extra-large, can be determined by their orientation preferences. Recently, we reported that a colloidal dispersion of diamagnetic titanate(IV) nanosheets (Ti^IVNSs), when placed in a magnetic field, is highly anisotropic because Ti^IVNS anomalously orients its 2D plane orthogonal to the magnetic flux lines due to its large anisotropic magnetic susceptibility. Herein, we report a serendipitous finding that Ti^IVNSs can be in situ photochemically reduced into a paramagnetic species (Ti^IV/IIINSs), so that their preference of magnetic orientation changes from orthogonal to parallel. This transition distinctly alters the structural anisotropy and therefore optical appearance of the colloidal dispersion in a magnetic field. We also found that Ti^IV/IIINSs is autoxidized back to Ti^IVNSs under non-deaerated conditions. By using an elaborate setup, the dispersion of Ti^IVNSs serves as an optical switch remotely operable by magnet and light.

On the thermotropic and magnetotropic phase behavior of lipid liquid crystals containing magnetic nanoparticles

The inclusion of superparamagnetic iron oxide nanoparticles (SPIONs) in lipid mesophases is a promising strategy for drug-delivery applications, combining the innate biocompatibility of lipid architectures with SPIONs' response to external magnetic fields. Moreover, the organization of SPIONs within the lipid scaffold can lead to locally enhanced SPIONs concentration and improved magnetic response, which is key to overcome the current limitations of hyperthermic treatments. Here we present a Small-Angle X-ray Scattering (SAXS) structural investigation of the thermotropic and magnetotropic behavior of glyceryl monooleate (GMO)/water mesophases, loaded with hydrophobic SPIONs. We prove that even very low amounts of SPIONs deeply alter the phase behavior and thermotropic properties of the mesophases, promoting a cubic to hexagonal phase transition, which is similarly induced upon application of an Alternating Magnetic Field (AMF). Moreover, in the hexagonal phase SPIONs spontaneously self-assemble within the lipid scaffold into a linear supraparticle. This phase behavior is interpreted in the framework of the Helfrich's theory, which shows that SPIONs affect the mesophase both from a viscoelastic and from a structural standpoint. Finally, the dispersion of these cubic phases into stable magnetic colloidal particles, which retain their liquid crystalline internal structure, is addressed as a promising route towards magneto-responsive drug-delivery systems (DDS).

Monoolein Cubic Phase Gels and Cubosomes Doped with Magnetic Nanoparticles-Hybrid Materials for Controlled Drug Release

Hybrid materials consisting of a monoolein lipidic cubic phase (LCP) incorporating two types of magnetic nanoparticles (NP) were designed as addressable drug delivery systems. The materials, prepared in the form of a gel, were subsequently used as a macroscopic layer modifying an electrode and, after dispersion to nanoscale, as magnetocubosomes. These two LCPs were characterized by small-angle X-ray scattering (SAXS), cross-polarized microscopy, magnetic measurements, and phase diagrams. The magnetic dopants were hydrophobic NP_oleic and hydrophilic NP_citric, characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM), and their influence on the properties of the cubic phases was investigated. The removal of the anticancer drug, Doxorubicin (Dox) from the hybrid cubic phase gels was studied by electrochemical methods. The advantages of incorporating magnetic nanoparticles into the self-assembled lipid liquid crystalline phases include the ability to address the cubic phase nanoparticle containing large amounts of drug and to control the kinetics of the drug release.

Dynamic formation of nanostructured particles from vesicles via invertase hydrolysis for on-demand delivery

Controlled hydrolysis via invertase action alters molecular shape and therefore lipid curvature, consequently triggering the release of encapsulated drug.

Temperature responsive lipid liquid crystal layers with embedded nanogels

Polymer nanogels are embedded within layers consisting of a nonlamellar liquid crystalline lipid phase to act as thermoresponsive controllers of layer compactness and hydration.

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

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

Magnetic actuation of a thermodynamically stable colloid of ferromagnetic nanoparticles in a liquid crystal

We report the development of a highly stable nanomaterial based on ferromagnetic nanoparticles dispersed in a thermotropic liquid crystal. The long-term colloidal stability and homogeneity were achieved through surface modification of the nanoparticles with a mixture of a dendritic oligomesogenic surfactant and hexylphosphonic acid and confirmed by optical and electron microscopy. The nanomaterial has an increased sensitivity to the magnetic field possessing collective and non-collective magneto-optical responses in contrast to the undoped LC. The effective coupling of the spherical particles with the LC director is due to the arrangement of the nanoparticles in chains.

Lyotropic La-containing lamellar liquid crystals: phase behaviour, thermal and structural properties

This paper provides the results of POM, DSC and XRPD methods characterizing the liquid crystalline behaviour, thermal properties and structural parameters of lyotropic systems based on a nonionic surfactant and lanthanum nitrate (La(3+)). The systems based on tetraethylene glycol monododecyl ether (C12EO4) and lanthanum nitrate have been demonstrated to form a lamellar phase. The concentration and temperature ranges of the existence of mesophases as well as thermodynamic parameters of phase transitions have been estimated. The structural parameters of the lamellar phase of the C12EO4/La(3+)/water systems have been determined using X-ray diffraction. The model of molecular packing in lamellar lanthanide-containing lyotropic mesophases was proposed for the observed patterns of structural parameters obtained at various water contents. NMR (1)H with a pulsed magnetic field gradient has been used to characterize molecular motions in the C12EO4/La(3+)/H2O systems with different water contents.

Liquid crystalline thermotropic and lyotropic nanohybrids

This review is meant to give the reader an insight into hybrids incorporating different types of nanoparticles, e.g. metallic or metal oxides, within different types of lyotropic and thermotropic liquid crystals, from relatively small calamitic molecules to the larger discotics and polymers. In particular, this review highlights the importance of nanoparticle-liquid crystal interactions in accessing hybrid materials that exhibit synergetic properties.

Tunable morphology and mesophase formation by naphthalene-containing poly(aryl ether) dendron-based low-molecular-weight fluorescent gels

Novel poly(aryl ether) dendron-based low-molecular-weight organogelaters (LMWG) containing naphthalene units at the core have been synthesized, and the self-assembly of the system has been examined in a variety of solvents and solvent mixtures. The compounds readily form gels with attractive critical gel concentration values associated with gelation-induced enhanced emission (GIEE). In addition to the remarkable properties of the previously reported anthracene and pyrene analogues (Rajamalli, P.; Prasad, E. Org. Lett.2011, 13, 3714 and Rajamalli, P.; Prasad, E. Soft Matter2012, 8, 8896), the self-assembled systems exhibit distinctly different structure-property relationships. Unlike the reported ones, the present system forms sheetlike morphology in nonpolar solvent mixtures, giant vesicles in polar solvent mixtures, and lamellar or hexagonal columnar phases in single solvents. The unique properties of the self-assembled systems, which were analyzed through electron microscopic (SEM, TEM, AFM) and spectroscopic techniques (POM, fluorescence), are attributed to the replacement of anthracene/pyrene units by naphthalene units. The present work unravels the subtle role of minute structural change in altering the properties of LMWGs based on poly(aryl ether) dendrons.

Controlling anisotropic drug diffusion in lipid-Fe3O4 nanoparticle hybrid mesophases by magnetic alignment

We present a new strategy to control the anisotropic diffusion of hydrophilic drugs in lyotropic liquid crystals via the dispersion of magnetic nanoparticles in the mesophase, followed by reorientation of the mesophase domains via an external magnetic field. We select a lipid reverse hexagonal phase doped with magnetic iron oxide nanoparticles and glucose and caffeine as model hybrid mesophase and hydrophilic drugs, respectively. Upon cooling through the disorder-order phase transition of the hexagonal phase and under exposure to an external moderate magnetic field (1.1 T), both the nanoparticles and the hexagonal domains align with their columnar axes along the field direction. As a result, the water nanochannels of the inverted hexagonal domains also align parallel to the field direction, leading to a drug diffusion coefficient parallel to the field direction much larger than what was measured perpendicularly: in the case of glucose, for example, this difference in diffusion coefficients approaches 1 order of magnitude. Drug diffusion of the unaligned reverse hexagonal phase, which consists of randomly distributed domains, shows values in between the parallel and transversal diffusion values. This study shows that modifying the overall alignment of anisotropic mesophases via moderate external fields is a valuable means to control the corresponding transport tensor of the mesophase and demonstrates that the orientation of the domains plays an important role in the diffusion process of foreign hydrophilic molecules.

Diffusion, molecular separation, and drug delivery from lipid mesophases with tunable water channels

Lyotropic liquid crystals characterized by a bicontinuous cubic phase (BCP) have a structure characterized by interpenetrated water channels following triply periodic minimal surfaces, which can be stable in excess water conditions and thus suitable in a multitude of applications. The control of the water channels size in these systems has a direct impact on their use for drug delivery, crystallization, and membrane separation processes. In this work we carry out systematic diffusion studies to show how the control on the water channel dimensions directly correlates with the release and separation performance of bicontinuous cubic phases. Specifically, we tune the water channels diameter of the monolinolein/water system by adding different amounts of sucrose stearate, which, having hydration-enhancing properties, can shift the boundaries of the phase diagram. We then design a model bicontinuous cubic phase lipidic membrane of the Im3m space group, having a sugar ester to monolinolein ratio of 20%, and we follow the diffusion within its water channels, by using molecules that differ systematically in size and molecular conformation, and we demonstrate, for each class of molecules, a diffusion-enhanced process upon increase of the water channel diameter. Finally, we also show the ability of the bicontinuous cubic phase to efficiently and selectively separate nanoparticles of a target size, by choosing an amount of sucrose stearate for which the water channel diameter and the nanoparticle dimensions match, demonstrating the possible use of these systems as filtering membranes of tunable molecular cutoff.

Controlling the nanostructure of gold nanorod-lyotropic liquid-crystalline hybrid materials using near-infrared laser irradiation

Lipid-based liquid-crystalline matrixes provide a unique prospect for stimuli-responsive nanomaterials, attributed to the ability to effect self-assembly of the lipids at the molecular level. Differences in liquid crystal nanostructure have previously been shown to change drug diffusion and hence release, with research progressing toward the use of in situ changes to nanostructure to control drug release. Toward this goal, we have previously communicated the ability to switch between nonlamellar structures using gold nanorod (GNR)-phytantriol-based liquid-crystalline hybrid nanomaterials as near-infrared light responsive systems (Fong et al. Langmuir 2010, 26, 6136-6139). In this study, the effect of laser activation on matrix nanostructure with changes in a number of system variables including lipid composition, GNR aspect ratio, GNR concentration, and laser pulse time were investigated. The nanostructure of the matrix was followed using small-angle X-ray scattering, while both cryoFESEM and cryoTEM were used to visualize the effect of GNR incorporation into the liquid crystal nanostructure. The system response was found to be dependent on all variables, thus demonstrating the potential of these nanocomposite materials as reversible "on-demand" drug delivery applications.

Local switching of chemical patterns through light-triggered unfolding of creased hydrogel surfaces

Visible light induces switching of surface chemical patterns based on hybrid gels of thermally responsive poly(N-isopropyl acrylamide) copolymer networks containing iron oxide nanoparticles. The swelling of these hybrid gels is reduced upon illumination (see picture), allowing controlled unfolding of creased features formed owing to an elastic surface instability.