Bicelles: lipid nanostructured platforms with potential dermal applications

A new preparation method of covalent annular nanodiscs based on MTGase

The preservation of the native conformation and functionality of membrane proteins has posed considerable challenges. While detergents and liposome reconstitution have been traditional approaches, nanodiscs (NDs) offer a promising solution by embedding membrane proteins in phospholipids encircled by an amphipathic helical protein MSP belt. Nevertheless, a drawback of commonly used NDs is their limited homogeneity and stability. In this study, we present a novel approach to construct covalent annular nanodiscs (cNDs) by leveraging microbial transglutaminase (MTGase) to catalyze isopeptide bond formation between the side chains of terminal amino acids, specifically Lysine (K) and Glutamine (Q). This methodology significantly enhances the homogeneity and stability of NDs. Characterization of cNDs and the assembly of membrane proteins within them validate the successful reconstitution of membrane proteins with improved homogeneity and stability. Our findings suggest that cNDs represent a more suitable tool for investigating interactions between membrane proteins and lipids, as well as for analyzing membrane protein structures.

A dilute nematic gel produced by intramicellar segregation of two polyoxyethylene alkyl ether carboxylic acids

MOTIVATION

Surfactants like C8E8CH2COOH have such bulky headgroups that they cannot show the common sphere-to-cylinder transition, while surfactants like C18:1E2CH2COOH are mimicking lipids and form only bilayers. Mixing these two types of surfactants allows one to investigate the competition between intramicellar segregation leading to disc-like bicelles and the temperature dependent curvature constraints imposed by the mismatch between heads and tails.

EXPERIMENTS

We establish phase diagrams as a function of temperature, surfactant mole ratio, and active matter content. We locate the isotropic liquid-isotropic liquid phase separation common to all nonionic surfactant systems, as well as nematic and lamellar phases. The stability and rheology of the nematic phase is investigated. Texture determination by polarizing microscopy allows us to distinguish between the different phases. Finally, SANS and SAXS give intermicellar distances as well as micellar sizes and shapes present for different compositions in the phase diagrams.

FINDINGS

In a defined mole ratio between the two components, intramicellar segregation wins and a viscoelastic discotic nematic phase is present at low temperature. Partial intramicellar mixing upon heating leads to disc growth and eventually to a pseudo-lamellar phase. Further heating leads to complete random mixing and an isotropic phase, showing the common liquid-liquid miscibility gap. This uncommon phase sequence, bicelles, lamellar phase, micelles, and water-poor packed micelles, is due to temperature induced mixing combined with dehydration of the headgroups. This general molecular mechanism explains also why a metastable water-poor lamellar phase quenched by cooling can be easily and reproducibly transformed into a nematic phase by gentle hand shaking at room temperature, as well as the entrapment of air bubbles of any size without encapsulation by bilayers or polymers.

Efficient Drug Loading Method for Poorly Water-Soluble Drug into Bicelles through Passive Diffusion

The bicelle, a type of solid lipid nanoparticle, comprises phospholipids with varying alkyl chain lengths and possesses the ability to solubilize poorly water-soluble drugs. Bicelle preparation is complicated and time-consuming because conventional drug-loading methods in bicelles require multiple rounds of thermal cycling or co-grinding with drugs and lipids. In this study, we proposed a simple drug-loading method for bicelles that utilizes passive diffusion. Drug-unloaded bicelles were placed inside a dialysis device and incubated in a saturated solution of ketoconazole (KTZ), which is a model drug. KTZ was successfully loaded into bare bicelles over time with morphological changes, and the final encapsulated concentration was dependent on the lipid concentration of the bicelles. When polyethylene glycol (PEG) chains of two different lengths (PEG2K and 5K) were incorporated into bicelles, PEG2k and PEG5k bicelles mitigated the morphological changes and improved the encapsulation rate. This mitigation of morphological changes enhanced the encapsulated drug concentration. Specifically, PEG5k bicelles, which exhibited the greatest prevention of morphological changes, had a lower encapsulated concentration after 24 h than that of PEG2k bicelles, indicating that PEGylation with a longer PEG chain length improved the loading capacity but decreased the encapsulation rate owing to the presence of a hydration layer of PEG. Thus, PEG with a certain length is more suitable for passive loading. Moreover, loading factors, such as temperature and vehicles used in the encapsulation process, affected the encapsulation rate of the drug. Taken together, the passive loading method offers high throughput with minimal resources, making it a potentially valuable approach during early drug development phases.

Design of supramolecular nanosheets for drug delivery applications

Two specific concepts have emerged in the field of materials science over the last several decades: nanosheets and supramolecular polymers. More recently, supramolecular nanosheets, in which these two concepts are integrated, have attracted particular attention, and they exhibit many fascinating characteristics. This review focuses on the design and applications of supramolecular nanosheets consisting of tubulin proteins and phospholipid membranes.

Multilamellar ceramide core-structured microvehicles with substantial skin barrier function recovery

This study introduces a multilamellar ceramide core-structured microvehicle platform for substantial skin barrier function recovery. Our approach essentially focused on fabricating bacterial cellulose nanofiber (BCNF)-enveloped ceramide-rich lipid microparticles (CerMPs) by solidifying BCNF-armored oil-in-water Pickering emulsions. The oil drops consisted of Ceramide NP (a phytosphingosine backbone N-acylated with a saturated stearic acid) and fatty alcohols (FAs) with a designated stoichiometry. The thin BCNF shell layer completely blocked the growth of ceramide molecular crystals from the CerMPs for a long time. The CerMP cores displayed a multilamellar structure wherein the interlayer distance and lateral packing could be manipulated using FAs with different alkyl chain lengths. The CerMPs remarkably lowered the trans-epidermal water loss while restoring the structural integrity of the epidermis in damaged skin. The results obtained herein highlight that the CerMP system provides a practical methodology for developing various types of skin-friendly formulations that can strengthen the skin barrier function.

The Formation of Morphologically Stable Lipid Nanocarriers for Glioma Therapy

Cerasomes are a promising modification of liposomes with covalent siloxane networks on the surface that provide outstanding morphological stability while maintaining all the useful traits of liposomes. Herein, thin film hydration and ethanol sol injection methods were utilized to produce cerasomes of various composition, which were then evaluated for the purpose of drug delivery. The most promising nanoparticles obtained by the thin film method were studied closely using MTT assay, flow cytometry and fluorescence microscopy on T98G glioblastoma cell line and modified with surfactants to achieve stability and the ability to bypass the blood-brain barrier. An antitumor agent, paclitaxel, was loaded into cerasomes, which increased its potency and demonstrated increased ability to induce apoptosis in T98G glioblastoma cell culture. Cerasomes loaded with fluorescent dye rhodamine B demonstrated significantly increased fluorescence in brain slices of Wistar rats compared to free rhodamine B. Thin film hydration with Tween 80 addition was established as a more reliable and versatile method for cerasome preparation. Cerasomes increased the antitumor action of paclitaxel toward T98G cancer cells by a factor of 36 and were able to deliver rhodamine B over the blood-brain barrier in rats.

Anionic Technol PG-Based Nanoparticles Prepared Using Cholic Acid-Derived Surfactants

In this work, the dispersibility of Technol PG, composed of anionic phospholipids, was investigated in the presence of cholic acid-based surfactants.

Stabilization of bicelles using metal-binding peptide for extended blood circulation

A metal-binding peptide appending cholic acid, Chol-MBP, formed bicelles by mixing with 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine (DPPC). Coordination of Chol-MBP with Cu²⁺ stabilized DPPC bicelles against dilution and contamination of serum proteins, enabling extended blood circulation. This study demonstrates an effective supramolecular design of phospholipid bicelles with enhanced stability useful for membrane-based biomaterials.

Bicelle Composed of 1,2-Dipalmitoyl-sn-Glycero-3-Phosphatidylcholine and Sodium Cholate

A mixture of 1,2-dipalmitoyl- sn-glycero-3-phosphatidylcholine (DPPC) phospholipid and sodium chelate (SC) formed bicelles (DPPC–SC bicelle) at around 50 °C. In 2H nuclear magnetic resonance (NMR) measurement of the dispersion of DPPC–SC bicelle, quadrupole splitting of D2O, an index of the ability to orient molecules, was observed.

Bicelles as a carrier for bioactive compounds in beverages: application to nerolidol, an active sesquiterpene alcohol

ABSTRACT

Nerolidol is a natural sesquiterpene alcohol with promising but limited application in food and pharmaceutical fields due to several factors including low photostability and low aqueous solubility. Recently, several carriers loading nerolidol were prepared and tested in fresh orange juice. Lipid vesicles loading nerolidol did not exhibit satisfactory organoleptic properties in this beverage. Hence, DMPC/DHPC bicelles were prepared as a new phospholipid-based carrier for nerolidol at different molar ratios. The bicelle suspensions were characterized in terms of homogeneity, particles size, and morphology. The optimal formulation (phospholipid:nerolidol molar ratio 100:1) was selected based on transparent appearance, homogeneity, and particle size (~ 45 nm). Besides, it showed a high encapsulation efficiency of nerolidol and a high incorporation rate of phospholipids. Transmission electron microscopy analysis demonstrated the formation of bicelles. The bicelles membrane fluidity was assessed by 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy and differential scanning calorimetry analysis. The membrane fluidity of bicelles appeared to increase in the presence of nerolidol in a concentration dependent manner. To our knowledge this is the first study dealing with the encapsulation of an essential oil component in bicelles.

GRAPHIC ABSTRACT

Biomimetic lipid Nanocomplexes incorporating STAT3-inhibiting peptides effectively infiltrate the lung barrier and ameliorate pulmonary fibrosis

Activation of signal transducer and activator of transcription 3 (STAT3) under conditions of inflammation plays a crucial role in the pathogenesis of life-threatening pulmonary fibrosis (PF), initiating pro-fibrotic signaling following its phosphorylation. While there have been attempts to interfere with STAT3 activation and associated signaling as a strategy for ameliorating PF, potent inhibitors with minimal systemic toxicity have yet to be developed. Here, we assessed the in vitro and in vivo therapeutic effectiveness of a cell-permeable peptide inhibitor of STAT3 phosphorylation, designated APTstat3-9R, for ameliorating the indications of pulmonary fibrosis. Our results demonstrate that APTstat3-9R formulated with biomimetic disc-shaped lipid nanoparticles (DLNPs) markedly enhanced the penetration of pulmonary surfactant barrier and alleviated clinical symptoms of PF while causing negligible systemic cytotoxicity. Taken together, our findings suggest that biomimetic lipid nanoparticle-assisted pulmonary delivery of APTstat3-9R may be a feasible therapeutic option for PF in the clinic, and could be applied to treat other fibrotic diseases.

Versatile Phospholipid Assemblies for Functional Synthetic Cells and Artificial Tissues

The bottom-up construction of a synthetic cell from nonliving building blocks capable of mimicking cellular properties and behaviors helps to understand the particular biophysical properties and working mechanisms of a cell. A synthetic cell built in this way possesses defined chemical composition and structure. Since phospholipids are native biomembrane components, their assemblies are widely used to mimic cellular structures. Here, recent developments in the formation of versatile phospholipid assemblies are described, together with the applications of these assemblies for functional membranes (protein reconstituted giant unilamellar vesicles), spherical and nonspherical protoorganelles, and functional synthetic cells, as well as the high-order hierarchical structures of artificial tissues. Their biomedical applications are also briefly summarized. Finally, the challenges and future directions in the field of synthetic cells and artificial tissues based on phospholipid assemblies are proposed.

Physical Enhancement? Nanocarrier? Current Progress in Transdermal Drug Delivery

A transdermal drug delivery system (TDDS) is a method that provides drug adsorption via the skin. TDDS could replace conventional oral administration and blood administration because it is easily accessible. However, it is still difficult to design efficient TDDS due to the high barrier property of skin covered with stratum corneum, which inhibits the permeation of drug molecules. Thus far, TDDS methods by applying physical stimuli such as microneedles and chemical stimuli such as surfactants have been actively developed. However, it has been hard to avoid inflammation at the administration site because these methods partially destroy the skin tissue. On the other hand, TDDS with nanocarriers minimizing damage to the skin tissues has emerged together with the development of nanotechnology in recent years. This review focuses on current trends in TDDS.

Effects of fluidity and charge density on the morphology of a bicellar mixture - A SANS study

The spontaneously formed structures of physiologically relevant lipid model membranes made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) and 1,2-hexanoyl-sn-glycero-3-phosphocholine have been evaluated in depth using small angle neutron scattering. Although a common molar ratio of long- to short- chain phospholipids (~4) as reported in many bicellar mixtures was used, discoidal bicelles were not found as the major phase throughout the range of lipid concentration and temperature studied, indicating that the required condition for the formation of bicelle is the immiscibility between the long- and short- chain lipids, which were in the gel and L_α phases, respectively, in previous reports. In this study, all lipids are in the L_α phase. The characterization outcome suggests that the spontaneous structures tie strongly with the physical parameters of the system such as melting transition temperature of the long-chain lipid, total lipid concentration and charge density of the system. Multilamellar vesicles, unilamellar vesicles, ribbons and perforated lamellae can be obtained based on the analysis of the small angle neutron scattering results, leading to the construction of structural diagrams. This report provides the important map to choose suitable lipid systems for the structural study of membrane-associated proteins, design of theranostic nanocarriers or other related research fields.

Phospholipid Self-Assemblies Shaped Like Ancient Chinese Coins for Artificial Organelles

Phospholipid self-assemblies are ubiquitous in organisms. Nonspherical lipid-based proto-organelles bear the merits with structures similar to real organelles. It is still a challenge to mimic mass transport between organelles inside cells. Herein, unusual phospholipid self-assemblies shaped like ancient Chinese coins (ACC) were discovered by the recrystallization of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine in an ethanol/water solution from 50 to 25 °C with a certain cooling rate. Their diameter and the ratio of the square edge to the disk diameter were controlled by varying ethanol percentage, lipid concentration, and cooling rate. The ACC-shaped phospholipid bicelles expanded to stacked cisterna structures in pure water, which were regarded as artificial organelles. Mass transport among organelles in a cell was mimicked via the membrane fusion of vesicle shuttles and artificial organelles, which induced cascade enzyme reactions inside artificial organelles. The ACC-shaped phospholipid assemblies provide nice platforms for the studies of cell biology and bottom-up synthetic biology.

Anisotropic active ligandations in siRNA-Loaded hybrid nanodiscs lead to distinct carcinostatic outcomes by regulating nano-bio interactions

Active targeting modification is one of the foremost nanomedicine strategies for the efficacy improvement. Compared to the homogeneous ligandation on spherical nanocarriers, non-spherical nanomedicines usually make the ligand modification more complicated. The modified ligands always exhibit anisotropy and heterogeneity. However, there is very little systematic study on these diversified anisotropic modifications. The efficacy difference and underlying mechanism were still unclear. Here, we separately fabricated hybrid nanodiscs (NDs) conjugated with cRGD on the edge and plane surfaces to engineer two anisotropic targeting nanocarriers (E-cRGD-NDs and P-cRGD-NDs, respectively) for gene delivery. The ligand anisotropy endowed NDs with diversified cellular interactions, and caused different efficacies between E-cRGD-NDs and P-cRGD-NDs. Of note, E-cRGD-NDs showed significant superiority in siRNA loading, cellular uptake, silence efficiency, protein expression and even in vivo efficacy. The mechanism investigation revealed the functional anisotropy specifically for E-cRGD-NDs. The edge modification of cRGD efficiently separated the targeting and siRNA loading domains, maximizing their respective functions. These findings reflected the unique effect of ligand anisotropy, also provided a new strategy for the targeting screening of extensive nanomedicines.

Interplay between ligand mobility and nanoparticle geometry during cellular uptake of PEGylated liposomes and bicelles

We explore the cellular uptake process of PEGylated liposomes and bicelles by investigating their membrane wrapping process using large-scale molecular dynamics simulations. We find that due to the mobility of ligands on the liposome/bicelle, the membrane wrapping process of a PEGylated liposome/bicelle can be divided into two stages, whose transition is determined by a critical wrapping fraction fc; it is reached when all the ligands are exhausted and bound to receptors within the cell membrane. Before this critical scenario is approached, the grafted polyethylene glycol (PEG) polymers aggregate together within the membrane-wrapped region of the liposome/bicelle, driven by ligand-receptor binding. For wrapping fractions f > fc, membrane wrapping cannot proceed unless a compressive membrane tension is provided. By systematically varying the membrane tension and PEG molar ratio, we establish phase diagrams about wrapping states for both PEGylated liposomes and bicelles. According to these diagrams, we find that the absolute value of the compressive membrane tension required by a fully wrapped PEGylated bicelle is smaller than that of the PEGylated liposome, indicating that the PEGylated bicelle is easily internalized by cells. Further theoretical analysis reveals that compared to a liposome, the flatter surface at the top of a bicelle makes it energetically more favored beyond the critical wrapping fraction fc. Our simulations confirm that the interplay between ligand mobility and NP geometry can significantly change the understanding about the influence of NP geometry on the membrane wrapping process. It can help us to better understand the cellular uptake process of the PEGylated liposome/bicelle and to improve the design of lipid-like NPs for drug delivery.

Small-Angle X-ray Scattering Studies on the Structure of Disc-Shaped Bicelles Incorporated with Neutral PEGylated Lipids

In this study, small-angle X-ray scattering (SAXS) is successfully employed to investigate the structure of the DPPC/diC7PC disc-shaped bicelles incorporated with different amounts of C16-PEG2000-Ceramide lipids. The incorporation of the C16-PEG2000-Ceramide lipids could provide an antifouling capability to the bicelle for biomedical applications. However, traditionally it is believed that most of the incorporated PEGlylated lipids should lie in the rim of the disc-shaped bicelle. In this study, high sensitivity SAXS reveals the distribution of the added C16-PEG2000-Ceramide lipids in both the planar region and in the rim of the bicelle. The PEG brushes of C16-PEG2000-Ceramide lipids form a second shell outside the lipid headgroup shell of the bicelle. A double shell disc bicelle model is used in analyzing the SAXS data. The lipid density of C16-PEG2000-Ceramide in the rim is found to be about 1.7 times the C16-PEG2000-Ceramide lipid density in the planar region for all three C16-PEG2000-Ceramide concentrations, 1, 2, and 3 mM. Moreover, the bicelle core radius can be predicted well using the actual molecular ratio of lipids in the planar region to the lipids in the rim of the bicelles in the model calculation.

Combination of Roll Grinding and High-Pressure Homogenization Can Prepare Stable Bicelles for Drug Delivery

To improve the solubility of the drug nifedipine (NI), NI-encapsulated lipid-based nanoparticles (NI-LNs) have been prepared from neutral hydrogenated soybean phosphatidylcholine and negatively charged dipalmitoylphosphatidylglycerol at a molar ratio of 5/1 using by roll grinding and high-pressure homogenization. The NI-LNs exhibited high entrapment efficiency, long-term stability, and enhanced NI bioavailability. To better understand their structures, cryo transmission electron microscopy and atomic force microscopy were performed in the present study. Imaging from both instruments revealed that the NI-LNs were bicelles. Structures prepared with a different drug (phenytoin) or with phospholipids (dimyristoylphosphatidylcholine, dipalmitoylphosphatidylcholine, and distearoylphosphatidylcholine) were also bicelles. Long-term storage, freeze-drying, and high-pressure homogenization did not affect the structures; however, different lipid ratios, or the presence of cholesterol, did result in liposomes (5/0) or micelles (0/5) with different physicochemical properties and stabilities. Considering the result of long-term stability, standard NI-LN bicelles (5/1) showed the most long-term stabilities, providing a useful preparation method for stable bicelles for drug delivery.

Advancing the Pharmaceutical Potential of Bioinorganic Hybrid Lipid-Based Assemblies

Bioinspired lipid assemblies that mimic the elaborate architecture of natural membranes have fascinated researchers for a long time. These lipid assemblies have gone from being just an imperative platform for biophysical research to a pharmaceutical delivery system for biomedical applications. Despite success, these organized nanosystems are often subject to the mechanical instability and limited theranostic capability without adding any inconvenient modifications. To reach their advanced pharmaceutical potential, various bioinorganic hybrid lipid-based assembles, which provide new opportunities to synergistically complement and improve therapeutic/diagnostic potential of existing lipid-based nanomedicine with distinct mechanisms containing inorganic embedded surfactants, have recently been developed.

Kinetically Stable Bicelles with Dilution Tolerance, Size Tunability, and Thermoresponsiveness for Drug Delivery Applications

Mixtures of a phospholipid (1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine, DPPC) and a sodium-cholate-derived surfactant (SC-C₅ ) at room temperature formed phospholipid bilayer fragments that were edge-stabilized by SC-C₅ : so-called "bicelles". Because the bilayer melting point of DPPC (41 °C) is above room temperature and because SC-C₅ has an exceptionally low critical micelle concentration (<0.5 mm), the bicelles are kinetically frozen at room temperature. Consequently, they exist even when the mixture is diluted to a concentration of 0.04 wt %. In addition, the lateral size of the bicelles can be fine-tuned by altering the molar ratio of DPPC to SC-C₅ . On heating to ≈37 °C, the bicelles transformed into micelles composed of DPPC and SC-C₅ . By taking advantage of the dilution tolerance, size tunability, and thermoresponsiveness, we demonstrated in vitro drug delivery based on use of the bicelles as carriers, which suggests their potential utility in transdermal drug delivery.

Nanoparticle-Assisted Transcutaneous Delivery of a Signal Transducer and Activator of Transcription 3-Inhibiting Peptide Ameliorates Psoriasis-like Skin Inflammation

Signal transducer and activator of transcription 3 (STAT3) is constitutively activated in psoriatic skin inflammation and acts as a key player in the pathogenesis and progression of this autoimmune disease. Although numerous inhibitors that intervene in STAT3-associated pathways have been tested, an effective, highly specific inhibitor of STAT3 has yet to be identified. Here, we evaluated the in vitro and in vivo biological activity and therapeutic efficacy of a high-affinity peptide specific for STAT3 (APTstat3) after topical treatment via intradermal and transcutaneous delivery. Using a preclinical model of psoriasis, we show that intradermal injection of APTstat3 tagged with a 9-arginine cell-penetrating peptide (APTstat3-9R) reduced disease progression and modulated psoriasis-related cytokine signaling through inhibition of STAT3 phosphorylation. Furthermore, by complexing APTstat3-9R with specific lipid formulations led to formation of discoidal lipid nanoparticles (DLNPs), we were able to achieve efficient skin penetration of the STAT3-inhibiting peptide after transcutaneous administration, thereby effectively inhibiting psoriatic skin inflammation. Collectively, these findings suggest that DLNP-assisted transcutaneous delivery of a STAT3-inhibiting peptide could be a promising strategy for treating psoriatic skin inflammation without causing adverse systemic events. Moreover, the DLNP system could be used for transdermal delivery of other therapeutic peptides.

Electroporation of Skin Stratum Corneum Lipid Bilayer and Molecular Mechanism of Drug Transport: A Molecular Dynamics Study

The electroporation technique has been used significantly to increase drug permeation through the skin. This technique relies on the application of short-timed (microseconds to millisecond) electric fields (generally, order of 50--300 V) on the skin to create microscopic pores. However, the molecular mechanism of pore formation, resulting in an enhanced flux of active molecules through the skin, remains poorly understood. In this study, extensive atomistic molecular dynamics simulation of skin lipids [made up of ceramide (CER), cholesterol (CHOL), and free fatty acid (FFA)] has been performed at various external electric fields. We show for the first time the pore formation in the skin lipid bilayer during electroporation. We show the effect of the applied external electrical field (0.6-1.0 V/nm) on the pore formation dynamics in the lipid bilayer of different sizes (154, 616, and 2464 lipids) and compositions (CER/CHOL/FFA, 1:0:0, 1:0:1, 1:1:0, 1:1:1). The pore formation and resealing kinetics were different and were found to be highly dependent on the composition of the skin lipid bilayer. The pore formation time decreased with increase in the bilayer size. The pore sustaining electric field was found to be in the range of 0.20-0.25 V/nm for equimolar CER, CHOL, and FFA lipid bilayers. The skin lipid bilayer (1:1:1) sealed itself within 20 ns after the removal of the external electric field. We also present the molecular mechanism of enhancement of drug permeation in the presence of external field as compared to the passive diffusion. The molecular-level understanding obtained here could help in optimizing/designing the electroporation experiments for effective drug delivery. For a given skin composition and size of the drug molecule, the combination of pore formation time and pore growth model can be used to know a priori the desired electric field and time for the application of the electric field.

Cerasomes and Bicelles: Hybrid Bilayered Nanostructures With Silica-Like Surface in Cancer Theranostics

Over years, theranostic nanoplatforms have provided a new avenue for the diagnosis and treatment of various cancer types. To this end, a myriad of nanocarriers such as polymeric micelles, liposomes, and inorganic nanoparticles (NPs) with distinct physiochemical and biological properties are routinely investigated for preclinical and clinical studies. So far, liposomes have received great attention for various biomedical applications, however, it still suffers from insufficient morphological stability. On the other hand, inorganic NPs depicting excellent therapeutic ability have failed to address biocompatibility issues. This has raised a serious concern about the clinical approval of multifunctional organic or inorganic-based theranostic agents. Recently, partially silica coated nanohybrids such as cerasomes and bicelles demonstrating both diagnostic and therapeutic ability in a single system, have drawn profound attention as a fascinating novel drug delivery system. Compared with traditional liposomal or inorganic-based nanoformulations, this new and highly stable nanocarriers integrates the functional attributes of biomimetic liposomes and silica NPs, therefore, synergize strengths and functions, or even surpass weaknesses of individual components. This review at its best enlightens the emerging concept of such partially silica coated nanohybrids, fabrication strategies, and theranostic opportunities to combat cancer and related diseases.

Development of Smart Optical Gels with Highly Magnetically Responsive Bicelles

Hydrogels delivering on-demand tailorable optical properties are formidable smart materials with promising perspectives in numerous fields, including the development of modern sensors and switches, the essential quality criterion being a defined and readily measured response to environmental changes. Lanthanide ion (Ln³⁺)-chelating bicelles are interesting building blocks for such materials because of their magnetic responsive nature. Imbedding these phospholipid-based nanodiscs in a magnetically aligned state in gelatin permits an orientation-dependent retardation of polarized light. The resulting tailorable anisotropy gives the gel a well-defined optical signature observed as a birefringence signal. These phenomena were only reported for a single bicelle-gelatin pair and required high magnetic field strengths of 8 T. Herein, we demonstrate the versatility and enhance the viability of this technology with a new generation of aminocholesterol (Chol-NH₂)-doped bicelles imbedded in two different types of gelatin. The highly magnetically responsive nature of the bicelles allowed to gel the anisotropy at commercially viable magnetic field strengths between 1 and 3 T. Thermoreversible gels with a unique optical signature were generated by exposing the system to various temperature conditions and external magnetic field strengths. The resulting optical properties were a signature of the gel's environmental history, effectively acting as a sensor. Solutions containing the bicelles simultaneously aligning parallel and perpendicular to the magnetic field directions were obtained by mixing samples chelating Tm³⁺ and Dy³⁺. These systems were successfully gelled, providing a material with two distinct temperature-dependent optical characteristics. The high degree of tunability in the magnetic response of the bicelles enables encryption of the gel's optical properties. The proposed gels are viable candidates for temperature tracking of sensitive goods and provide numerous perspectives for future development of tomorrow's smart materials and technologies.

Molecular engineering of lanthanide ion chelating phospholipids generating assemblies with a switched magnetic susceptibility

Lanthanide ion (Ln³⁺) chelating amphiphiles are powerful molecules for tailoring the magnetic response of polymolecular assemblies. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA) complexed to Ln³⁺ deliver highly magnetically responsive bicelles. Their magnetic properties are readily tuned by changing the bicellar size or the magnetic susceptibility Δχ of the bilayer lipids. The former technique is intrinsically bound to the region of the phase diagram guarantying the formation of bicelles. Methods aiming towards manipulating the Δχ of the bilayer are comparatively more robust, flexible and lacking. Herein, we synthesized a new Ln³⁺ chelating phospholipid using glutamic acid as a backbone: DMPE-Glu-DTPA. The chelate polyhedron was specifically engineered to alter the Δχ, whilst remaining geometrically similar to DMPE-DTPA. Planar asymmetric assemblies hundreds of nanometers in size were achieved presenting unprecedented magnetic alignments. The DMPE-Glu-DTPA/Ln³⁺ complex switched the Δχ, achieving perpendicular alignment of assemblies containing Dy³⁺ and parallel alignment of those containing Tm³⁺. Moreover, samples with chelated Yb³⁺ were more alignable than the Tm³⁺ chelating counterparts. Such a possibility has never been demonstrated for planar Ln³⁺ chelating polymolecular assemblies. The physico-chemical properties of these novel assemblies were further studied by monitoring the alignment behavior at different temperatures and by including 16 mol% of cholesterol (Chol-OH) in the phospholipid bilayer. The DMPE-Glu-DTPA/Ln³⁺ complex and the resulting assemblies are promising candidates for applications in numerous fields including pharmaceutical technologies, structural characterization of membrane biomolecules by NMR spectroscopy, as contrasting agents for magnetic resonance imaging, and for the development of smart optical gels.

A lamellar body mimetic system for the treatment of oxazolone-induced atopic dermatitis in hairless mice

BACKGROUND

Atopic dermatitis is a common skin disease characterized by a Th2 cell-dominant inflammatory infiltrate, elevated serum IgE levels and impaired epidermal barrier function. It is associated to abnormal epidermal lamellar body secretion, producing alteration in lipid composition and extracellular lamellar membrane organization.

OBJECTIVES

The oxazolone-induced atopic dermatitis in hairless mice was used to evaluate in vivo the effect of the application of a lipid system that mimics the morphology, structure and composition of epidermal lamellar bodies.

METHODS

The skin barrier function was evaluated measuring TEWL and skin hydration in vivo. Inflammation was assessed by analysis of serum IgE levels and histological analysis. The microstructure of the intercellular lipid region was also evaluated before and after treatment.

RESULTS

The skin condition was improved after 10 days of treatment indicated by decreased TEWL, decreased serum IgE levels, reduced epidermal thickness and reduced lymphocyte-dominated infiltrate. However, the treatment did no improve skin hydration.

CONCLUSIONS

The treatment with this lipid system seems to improve the skin condition by reinforcing the barrier function and reducing the skin inflammation. Therefore, the present study provides evidence that this lipid system combining appropriate lipid composition and morphology could be of interest for the development of future treatments for atopic dermatitis.

Mastering the magnetic susceptibility of magnetically responsive bicelles with 3β-amino-5-cholestene and complexed lanthanide ions

The magnetic susceptibility of lanthanide-chelating bicelles was selectively enhanced by introducing 3β-amino-5-cholestene (aminocholesterol, Chol-NH₂) in the bilayer. Unprecedented magnetic alignment of the bicelles was achieved without altering their size. An aminocholesterol conjugate (Chol-C₂OC₂-NH₂), in combination with different lanthanide ions, offers the possibility of fine-tuning the bicelle's magnetic susceptibility.

Fabrication Procedures and Birefringence Measurements for Designing Magnetically Responsive Lanthanide Ion Chelating Phospholipid Assemblies

Bicelles are tunable disk-like polymolecular assemblies formed from a large variety of lipid mixtures. Applications range from membrane protein structural studies by nuclear magnetic resonance (NMR) to nanotechnological developments including the formation of optically active and magnetically switchable gels. Such technologies require high control of the assembly size, magnetic response and thermal resistance. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and its lanthanide ion (Ln³⁺) chelating phospholipid conjugate, 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA), assemble into highly magnetically responsive assemblies such as DMPC/DMPE-DTPA/Ln³⁺ (molar ratio 4:1:1) bicelles. Introduction of cholesterol (Chol-OH) and steroid derivatives in the bilayer results in another set of assemblies offering unique physico-chemical properties. For a given lipid composition, the magnetic alignability is proportional to the bicelle size. The complexation of Ln³⁺ results in unprecedented magnetic responses in terms of both magnitude and alignment direction. The thermo-reversible collapse of the disk-like structures into vesicles upon heating allows tailoring of the assemblies' dimensions by extrusion through membrane filters with defined pore sizes. The magnetically alignable bicelles are regenerated by cooling to 5 °C, resulting in assembly dimensions defined by the vesicle precursors. Herein, this fabrication procedure is explained and the magnetic alignability of the assemblies is quantified by birefringence measurements under a 5.5 T magnetic field. The birefringence signal, originating from the phospholipid bilayer, further enables monitoring of polymolecular changes occurring in the bilayer. This simple technique is complementary to NMR experiments that are commonly employed to characterize bicelles.

Topical Delivery of Coumestrol from Lipid Nanoemulsions Thickened with Hydroxyethylcellulose for Antiherpes Treatment

We have recently shown that coumestrol, an isoflavonoid-like compound naturally occurring in soybeans, alfafa, and red clover, inhibited Herpes Simplex Virus types 1 (HSV-1) and 2 (HSV-2) replication. In this study, we designed coumestrol formulations in an attempt to enable its topical delivery to mucosa tissues. Physicochemical and microscopic examinations suggested that coumestrol was efficiently incorporated in positively-charged nanoemulsions dispersed in a hydroxyethylcellulose gel. The higher coumestrol flux through excised porcine esophageal mucosa was detected from nanoemulsions composed by a fluid phospholipid (dioleylphosphocholine, DOPC) in comparison with that of a rigid one (distearoylphosphocholine, DSPC) in two mucosa conditions (intact and injured). Such results were supported by confocal fluorescence images. Furthermore, the low IC₅₀ values demonstrated an increasement in the antiviral inhibition against HSV-1 and HSV-2 after incorporation of coumestrol into nanoemulsions containing DOPC. Overall, coumestrol-loaded nanoemulsions proved to be beneficial for herpes simplex treatment.

Understanding the Enhanced Magnetic Response of Aminocholesterol Doped Lanthanide-Ion-Chelating Phospholipid Bicelles

Cholesterol (Chol-OH) and its conjugates are powerful molecules for engineering the physicochemical and magnetic properties of phospholipid bilayers in bicelles. Introduction of aminocholesterol (3β-amino-5-cholestene, Chol-NH₂) in bicelles composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and the thulium-ion-chelating phospholipid 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA/Tm³⁺) results in unprecedented high magnetic alignments by selectively tuning the magnetic susceptibility Δχ of the bilayer. However, little is known on the underlying mechanisms behind the magnetic response and, more generally, on the physicochemical forces governing a Chol-NH₂ doped DMPC bilayer. We tackled this shortcoming with a multiscale bottom-up comparative investigation of Chol-OH and Chol-NH₂ mixed with DMPC. First, simplified monolayer models on a Langmuir trough were employed to compare the two steroid molecules at various contents in DMPC. In a second step, a molecular dynamics (MD) simulation allowed for a more representative model of the bicelle bilayer while monitoring the amphiphiles and their interactions on the molecular level. In a final step, we moved away from the models and investigated the effect of temperature on the structure and magnetic alignment of Chol-NH₂ doped bicelles by SANS. The DMPC/steroid monolayer studies showed that Chol-OH induces a larger condensation effect than Chol-NH₂ at steroid contents of 16 and 20 mol %. However, this tendency was inversed at steroid contents of 10, 30, and 40 mol %. Although the MD simulation with 16 mol % steroid revealed that both compounds induce a liquid-ordered state in DMPC, the bilayer containing Chol-NH₂ was much less ordered than the analogous system containing Chol-OH. Chol-NH₂ underwent significantly more hydrogen bonding interactions with neighboring DMPC lipids than Chol-OH. It seems that, by altering the dynamics of the hydrophilic environment of the bicelle, Chol-NH₂ changes the crystal field and angle of the phospholipid-lanthanide DMPE-DTPA/Tm³⁺ complex. These parameters largely determine the magnetic susceptibility Δχ of the complex, explaining the SANS results, which show significant differences in magnetic alignment of the steroid doped bicelles. Highly magnetically alignable DMPC/Chol-NH₂/DMPE-DTPA/Tm³⁺ (molar ratio 16:4:5:5) bicelles were achieved up to temperatures of 35 °C before a thermoreversible rearrangement into nonalignable vesicles occurred. The results confirm the potential of Chol-NH₂ doped bicelles to act as building blocks for the development of the magnetically responsive soft materials of tomorrow.

Methods for Generating Highly Magnetically Responsive Lanthanide-Chelating Phospholipid Polymolecular Assemblies

Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and its lanthanide ion (Ln³⁺) chelating phospholipid conjugate, 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA), assemble into highly magnetically responsive polymolecular assemblies such as DMPC/DMPE-DTPA/Ln³⁺ (molar ratio 4:1:1) bicelles. Their geometry and magnetic alignability is enhanced by introducing cholesterol into the bilayer in DMPC/Cholesterol/DMPE-DTPA/Ln³⁺ (molar ratio 16:4:5:5). However, the reported fabrication procedures remain tedious and limit the generation of highly magnetically alignable species. Herein, a simplified procedure where freeze thawing cycles and extrusion are replaced by gentle heating and cooling cycles for the hydration of the dry lipid film was developed. Heating above the phase transition temperature T_m of the lipids composing the bilayer before cooling back below the T_m was essential to guarantee successful formation of the polymolecular assemblies composed of DMPC/DMPE-DTPA/Ln³⁺ (molar ratio 4:1:1). Planar polymolecular assemblies in the size range of hundreds of nanometers are achieved and deliver unprecedented gains in magnetic response. The proposed heating and cooling procedure further allowed to regenerate the highly magnetically alignable DMPC/Cholesterol/DMPE-DTPA/Ln³⁺ (molar ratio 16:4:5:5) species after storage for one month frozen at -18 °C. The simplicity and viability of the proposed fabrication procedure offers a new set of highly magnetically responsive lanthanide ion chelating phospholipid polymolecular assemblies as building blocks for the smart soft materials of tomorrow.

Structural and biochemical differences between the Notch and the amyloid precursor protein transmembrane domains

γ-Secretase cleavage of the Notch receptor transmembrane domain is a critical signaling event for various cellular processes. Efforts to develop inhibitors of γ-secretase cleavage of the amyloid-β precursor C99 protein as potential Alzheimer's disease therapeutics have been confounded by toxicity resulting from the inhibition of normal cleavage of Notch. We present biochemical and structural data for the combined transmembrane and juxtamembrane Notch domains (Notch-TMD) that illuminate Notch signaling and that can be compared and contrasted with the corresponding traits of C99. The Notch-TMD and C99 have very different conformations, adapt differently to changes in model membrane hydrophobic span, and exhibit different cholesterol-binding properties. These differences may be exploited in the design of agents that inhibit cleavage of C99 while allowing Notch cleavage.

Sorption-desorption test for functional assessment of skin treated with a lipid system that mimics epidermal lamellar bodies

BACKGROUND

Many skin diseases are associated with either increases or decreases in lamellar body secretion, or dysfunctional lamellar bodies. Consequently, diseased skin is characterized by reduced barrier function and altered lipid composition and organization. Human skin is commonly evaluated in vivo with non-invasive biophysical techniques. The dynamic functions of the skin are evaluated with repeat measurements such as the sorption-desorption test (SDT).

OBJECTIVES

The aim of this study was to evaluate in vivo skin hydration-dehydration kinetics after treatment with a lipid system that mimics the morphology, structure and composition of lamellar bodies in both healthy and irritated human skin.

METHODS

A patch with an aqueous solution of 2% sodium lauryl sulfate (SLS) was used to irritate the skin of the volunteers. The SDT was performed with the CM 820 corneometer.

RESULTS

After treatment with this system, both healthy and SLS-irritated skin increased their ability to retain water and to release water slowly during the desorption phase.

CONCLUSIONS

Treatment with this system seems to reinforce the barrier function in both healthy and SLS-irritated human skin. Therefore, the present study provides evidence that this system could be of interest for developing future treatments for protecting and repairing the skin.

Synthesis and characterization of pHLIP® coated gold nanoparticles

Novel approaches in synthesis of spherical and multispiked gold nanoparticles coated with polyethylene glycol (PEG) and pH Low Insertion Peptide (pHLIP^®) were introduced. The presence of a tumor-targeting pHLIP^® peptide in the nanoparticle coating enhances the stability of particles in solution and promotes a pH-dependent cellular uptake. The spherical particles were prepared with sodium citrate as a gold reducing agent to form particles of 7.0±2.5 nm in mean metallic core diameter and ∼43 nm in mean hydrodynamic diameter. The particles that were injected into tumors in mice (21 µg of gold) were homogeneously distributed within a tumor mass with no staining of the muscle tissue adjacent to the tumor. Up to 30% of the injected gold dose remained within the tumor one hour post-injection. The multispiked gold nanoparticles with a mean metallic core diameter of 146.0±50.4 nm and a mean hydrodynamic size of ~161 nm were prepared using ascorbic acid as a reducing agent and disk-like bicelles as a template. Only the presence of a soft template, like bicelles, ensured the appearance of spiked nanoparticles with resonance in the near infrared region. The irradiation of spiked gold nanoparticles by an 805 nm laser led to the time- and concentration-dependent increase of temperature. Both pHLIP^® and PEG coated gold spherical and multispiked nanoparticles might find application in radiation and thermal therapies of tumors.

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pHLIP^®-PEG coated pH-sensitive gold spherical nanoparticles were synthesized.

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30% of the injected gold dose remained within the tumor one hour post-injection.

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pHLIP^®-PEG coated pH-sensitive gold multispiked nanoparticles were synthesized.

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Bicelles were used as a soft template to obtain multispiked nanoparticles.

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Temperature increases after 805 nm irradiation of spiked gold nanoparticles.

Tailoring Bicelle Morphology and Thermal Stability with Lanthanide-Chelating Cholesterol Conjugates

Bicelles composed of DMPC and phospholipids capable of chelating lanthanide ions, such as 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA), are highly tunable magnetically responsive soft materials. Further doping of these systems with cholesterol-DTPA conjugates complexed to a lanthanide ion considerably enhances the bicelle's size and magnetic alignability. The high value of these cholesterol conjugates for bicelle design remains largely unexplored. Herein, we examine how molecular structural alterations within the cholesterol-DTPA conjugates lead to contrasting self-assembled polymolecular aggregate structures when incorporated into DMPC/DMPE-DTPA/Tm(3+) bilayers. The nature of the linker connecting the DTPA-chelating moiety to the sterol backbone is examined by synthesizing conjugates of various linker lengths and polarities. The incorporation of these compounds within the bilayer results in polymolecular aggregate geometries of higher curvature. The increasing degrees of freedom for conformational changes conveyed to the chelator headgroup with increasing linker atomic length reduce the cholesterol-DTPA conjugate's critical packing parameter. Consequently, an inverse correlation between the number of carbon atoms in the linker and the bicelle radius is established. The introduction of polarity into the carbon chain of the linker did not cause major changes in the polymolecular aggregate architecture. Under specific conditions, the additives permit the formation of remarkably temperature-resistant bicelles. The versatility of design offered by these amphiphiles gives rise to new and viable tools for the growing field of magnetically responsive soft materials.

Investigation of Binary Lipid Mixtures of a Three-Chain Cationic Lipid with Phospholipids Suitable for Gene Delivery

In the present work, we characterize binary lipid mixtures consisting of a three-chain amino-functionalized cationic lipid (DiTT4) with different phospholipids, namely, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE), or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The mixing behavior was investigated by differential scanning calorimetry (DSC). Additionally, aqueous dispersions of the binary mixtures were characterized by means of dynamic light scattering (DLS), laser Doppler electrophoresis, and transmission electron microscopy (TEM) to get further information about particle size, charge, and shape. The complex formation between different binary lipid mixtures and plasmid DNA (pDNA) was investigated by zeta-(ζ)-potential (laser Doppler electrophoresis) and DLS measurements, and the lipid/DNA complexes (lipoplexes) were screened for efficient DNA transfer (transfection) in cell culture. Finally, efficient lipid compositions were investigated with respect to serum stability. This work provides a detailed characterization of the cationic lipid mixtures as foundation for further research. Efficient gene transfer in the presence of serum was demonstrated for selected lipoplexes showing their capability to be used as high-potency gene delivery vehicles.

Single lipid bilayer deposition on polymer surfaces using bicelles

A lipid bilayer was deposited on a 3 μm diameter polystyrene (PS) bead via hydrophobic anchoring of bicelles containing oxyamine-bearing cholesteric moieties reacting with the aldehyde functionalized bead surface. Discoidal bicelles were formed by mixing dimyristoylphosphatidylcholine (DMPC), dihexanoylphosphatidylcholine (DHPC), dimyristoyltrimethylammonium propane (DMTAP), and the oxyamine-terminated cholesterol derivative, cholest-5-en-3β-oxy-oct-3,6-oxa-an-8-oxyamine (CHOLOA), in the molar ratio DMPC/DHCP/DMTAP/CHOLOA (1/0.5/0.01/0.05) in water. Upon exposure to aldehyde-bearing PS beads, a stable single lipid bilayer coating rapidly formed at the bead surface. Fluorescence recovery after photobleaching demonstrated that the deposited lipids fused into an encapsulating lipid bilayer. Electrospray ionization mass spectrometry showed that the short chain lipid DHPC was entirely absent from the PS adherent lipid coating. Fluorescence quenching measurements proved that the coating was a single lipid bilayer. The bicelle coating method is thus simple and robust, can be modified to include membrane-associated species, and can be adapted to coat any number of different surfaces.

Morphological characterization of DMPC/CHAPSO bicellar mixtures: a combined SANS and NMR study

Spontaneously forming structures of a system composed of dimyristoyl phosphatidylcholine (DMPC) and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate (CHAPSO) were studied by small-angle neutron scattering (SANS), (31)P NMR, and stimulated echo (STE) pulsed field gradient (PFG) (1)H NMR diffusion measurements. Charged lipid dimyristoyl phosphatidylglycerol (DMPG) was used to induce different surface charge densities. The structures adopted were investigated as a function of temperature and lipid concentration for samples with a constant molar ratio of long-chain to short-chain lipids (= 3). In the absence of DMPG, zwitterionic bicellar mixtures exhibited a phase transition from discoidal bicelles, or ribbons, to multilamellar vesicles either upon dilution or with increased temperature. CHAPSO-containing mixtures showed a higher thermal stability in morphology than DHPC-containing mixtures at the corresponding lipid concentrations. In the presence of DMPG, discoidal bicelles (or ribbons) were also found at low temperature and lower lipid concentration mixtures. At high temperature, perforated lamellae were observed in high-concentration mixtures (≥7.5 wt %) whereas uniform unilamellar vesicles and bicelles formed in low-concentration mixtures (≤2.5 wt %), respectively, when the mixtures were moderately and highly charged. From the results, spontaneous structural diagrams of the zwitterionic and charged systems were constructed.