Transdermal delivery of ultradeformable cationic liposomes complexed with miR211-5p (UCL-211) stabilizes BRAFV600E+ melanocytic nevi

Small non-coding RNAs (e.g., siRNA, miRNA) are involved in a variety of melanocyte-associated skin conditions and act as drivers for alterations in gene expression within melanocytes. These molecular changes can potentially affect the cellular stability of melanocytes and promote their oncogenic transformation. Thus, small RNAs can be considered as therapeutic targets for these conditions, however, their transdermal delivery to the melanocytes through the epidermal barrier is challenging. We synthesized and extensively evaluated ultradeformable cationic liposome (UCLs) carriers complexed with synthetic microRNAs (miR211-5p; UCL-211) for transdermal delivery to melanocytes. UCL-211 complexes were characterized for their physicochemical properties, encapsulation efficiency, and deformability, which revealed a significant advantage over conventional liposomal carriers. Increased expression of miR211-5p stabilizes melanocytic nevi and keeps them in a growth-arrested state. We did a comprehensive assessment of cellular delivery, and biological activity of the miR211-5p carried by UCL-211 in vitro and their permeation through the epidermis of intact skin using ex vivo human skin tissue explants. We also demonstrated, in vivo, that transdermal delivery of miR211-5p by topical application of UCL-211 stabilized BRAFV600E+ nevi melanocytes in a benign nevi state.

Multi spectroscopic investigation of maisine-based microemulsions as convenient carriers for co-delivery of anticancer and anti-inflammatory drugs

Lipid-based drug delivery systems are very promising in addressing critical medical needs associated with cancer because they are able to enhance the efficacy of the therapeutic agents loaded in. Yet, their transferability from bench to bedside is still a challenge as it hits many barriers. Among them, the absence of a clear design made on the deeper understanding of the intermolecular forces underlying the formation of the drug-carrier system and the controlled release of the drug is relevant. In this contribution, we rationally designed and prepared lipid-based formulations of an anticancer drug, fluorouracil (FU - hydrophilic) and an anti-inflammatory drug, ibuprofen (IBU - hydrophobic) to thoroughly characterize the specific intermolecular interactions between drugs and components of the carrier matrix. Microemulsions (ME) were selected as the main carriers for this study, but a comparison with liposomes was performed to observe if different organization of the lipophilic and hydrophilic compartments influences the loading capacity and controlled release of these two drugs. Using Maisine CC, a biocompatible oil, and Tween 20 as the surfactant, normal oil-in-water ME loaded with FU and IBU (1:1, 1:3, 1:6, wt:wt) were prepared by the water titration method. MEs were characterized by DLS, Zeta potential, and DOSY spectroscopies to assess their droplet size, surface charge, structure and type of emulsion. Intermolecular interactions between drugs and components of the ME's matrix were investigated by FT-IR, RAMAN and 1H-NMR spectroscopies. The experimental results of DOSY revealed that all components of MEs are gathered in normal oil-in-water ME. Due to their different affinities for the main components of the ME, FU, and IBU were mainly distributed in the aqueous and oily phases, respectively, as supported by the droplet size measured by DLS. It was observed that co-loading the two drugs impacted the release behavior, assessed by the dialysis bag method, as compared with the mono-drug formulations. Based on the findings of this work, a release mechanism for FU and IBU was proposed, as well. Overall, the ME proved to be more suitable nanocarriers since the drugs, which were loaded in higher amounts as compared to liposomes, followed a controlled and sustained release of at least 96 h.

A Coarse-Grained Molecular Dynamics Perspective on the Release of 5-Fluorouracil from Liposomes

Liposomes, small bilayer phospholipid-containing vesicles, are frequently used to ensure slow drug release for a prolonged and improved therapeutic effect. Nevertheless, current findings on the membrane affinity and permeability of the anticancer agent 5-fluorouracil (5-FU) are confounding, which leads to a lack of a clear understanding of how lipid composition impacts the distribution of 5-FU within liposomal structures and its delivery. In the current work, we report a comprehensive coarse-grained molecular dynamics (CGMD) investigation on the influence of cholesterol (CHOL) and the cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) on the partitioning of 5-FU in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) double-bilayer systems, as well as its in vitro release from liposomes with identical lipid compositions. Our results show that 5-FU tends to accumulate at the water-lipid interface, in the vicinity of polar headgroups, without partitioning in the hydrophobic tail region. At the same time, the presence of CHOL proportionally increases the distribution of this drug in the interbilayer aqueous space, decreasing the drug's affinity toward the membrane polar head region, while DOTAP has only a slight effect on drug distribution. Thus, it is expected that 5-FU will be released slower from CHOL-containing DPPC liposomes but not DOTAP-containing vesicles. However, in vitro release studies showed that the release kinetics of 5-FU from DPPC vesicles is not influenced by the presence of CHOL and that the incorporation of 10 mol % DOTAP leads to the best release profile for 5-FU, highlighting the complexity of nanocarrier drug release kinetics. We hypothesize that the initial rapid release seen in dialysis experiments is not related to drug membrane permeability but rather to 5-FU adsorbed on the outer surface of liposomes.

Calcein release from DPPC liposomes by phospholipase A2 activity: Effect of cholesterol and amphipathic copolymers

In this study, we evaluated the impact of incorporating diblock and triblock amphiphilic copolymers, as well as cholesterol into DPPC liposomes on the release of a model molecule, calcein, mediated by exogenous phospholipase A2 activity. Our findings show that calcein release slows down in the presence of copolymers at low concentration, while at high concentration, the calcein release profile resembles that of the DPPC control. Additionally, calcein release mediated by exogenous PLA2 decreases as the amount of solubilized cholesterol increases, with a maximum between 18 mol% and 20 mol%. At concentrations higher than 24 mol%, no calcein release was observed. Studies conducted on HEK-293 and HeLa cells revealed that DPPC liposomes reduced viability by only 5% and 12%, respectively, after 3 hours of incubation, while DPPC liposome in presence of 33 mol% of Cholesterol reduced viability by approximately 11% and 23%, respectively, during the same incubation period. For formulations containing copolymers at low and high concentrations, cell viability decreased by approximately 20% and 40%, respectively, after 3 hours of incubation. Based on these preliminary results, we can conclude that the presence of amphiphilic copolymers at low concentration can be used in the design of new DPPC liposomes, and together with cholesterol, they can modulate liposome stabilization. The new formulations showed low cytotoxicity in HEK-293 cells, and it was observed that calcein release depended entirely on PLA2 activity and the presence of calcium ions.

Transdermal Delivery of Ultradeformable Cationic Liposomes Complexed with miR211-5p (UCL-211) Stabilizes BRAFV600E+ Melanocytic Nevi

Small non-coding RNAs (e.g. siRNA, miRNA) are involved in a variety of melanocyte-associated skin conditions and act as drivers for alterations in gene expression within melanocytes. These molecular changes can potentially affect the cellular stability of melanocytes and promote their oncogenic transformation. Thus, small RNAs can be considered as therapeutic targets for these conditions, however, their topical delivery to the melanocytes through the epidermal barrier is challenging. We synthesized and extensively evaluated ultradeformable cationic liposome (UCLs) carriers complexed with synthetic microRNAs (miR211-5p; UCL-211) for transdermal delivery to melanocytes. UCL-211 complexes were characterized for their physicochemical properties, encapsulation efficiency, and deformability, which revealed a significant advantage over conventional liposomal carriers. Increased expression of miR211-5p stabilizes melanocytic nevi and keeps them in growth-arrested state. We did a comprehensive assessment of cellular delivery, and biological activity of the miR211-5p carried by UCL-211 in vitro and their permeation through the epidermis of intact skin using ex vivo human skin tissue explants. We also demonstrated, in vivo, that topical delivery of miR211-5p by UCL-211 stabilized BRAFV600E+ nevi melanocytes in a benign nevi state.

Cellular Uptake of Cell-Penetrating Peptides Activated by Amphiphilic p-Sulfonatocalix[4]arenes

We report the synthesis of a series of amphiphilic p-sulfonatocalix[4]arenes with varying alkyl chain lengths (CX4-Cn) and their application as efficient counterion activators for membrane transport of cell-penetrating peptides (CPPs). The enhanced membrane activity is confirmed with the carboxyfluorescein (CF) assay in vesicles and by the direct cytosolic delivery of CPPs into CHO-K1, HCT 116, and KTC-1 cells enabling excellent cellular uptake of the CPPs into two cancer cell lines. Intracellular delivery was confirmed by fluorescence microscopy after CPP entry into live cells mediated by CX4-Cn, which was also quantified after cell lysis by fluorescence spectroscopy. The results present the first systematic exploration of structure-activity relationships for calixarene-based counterion activators and show that CX4-Cn are exceptionally effective in cellular delivery of CPPs. The dodecyl derivative, CX4-C12, serves as best activator. A first mechanistic insight is provided by efficient CPP uptake at 4 °C and in the presence of the endocytosis inhibitor dynasore, which indicates a direct translocation of the CPP-counterion complexes into the cytosol and highlights the potential benefits of CX4-Cn for efficient and direct translocation of CPPs and CPP-conjugated cargo molecules into the cytosol of live cells.

Impact of Lipid Composition on Vesicle Protein Adsorption: A BSA Case Study

Investigating the interaction between liposomes and proteins is of paramount importance in the development of liposomal formulations with real potential for bench-to-bedside transfer. Upon entering the body, proteins are immediately adsorbed on the liposomal surface, changing the nanovehicles' biological identity, which has a significant impact on their biodistribution and pharmacokinetics and ultimately on their therapeutic effect. Albumin is the most abundant plasma protein and thus usually adsorbs immediately on the liposomal surface. We herein report a comprehensive investigation on the adsorption of model protein bovine serum albumin (BSA) onto liposomal vesicles containing the zwitterionic lipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), in combination with either cholesterol (CHOL) or the cationic lipid 1,2-dioleoyl-3-trimethylammoniumpropane (DOTAP). While many studies regarding protein adsorption on the surface of liposomes with different compositions have been performed, to the best of our knowledge, the differential responses of CHOL and DOTAP upon albumin adsorption on vesicles have not yet been investigated. UV-vis spectroscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed a strong influence of the phospholipid membrane composition on protein adsorption. Hence, it was found that DOTAP-containing vesicles adsorb proteins more robustly but also aggregate in the presence of BSA, as confirmed by DLS and TEM. Separation of liposome-protein complexes from unadsorbed proteins performed by means of centrifugation and size exclusion chromatography (SEC) was also investigated. Our results show that neither method can be regarded as a golden experimental setup to study the protein corona of liposomes. Yet, SEC proved to be more successful in the separation of unbound proteins, although the amount of lipid loss upon liposome elution was higher than expected. In addition, coarse-grained molecular dynamics simulations were employed to ascertain key membrane parameters, such as the membrane thickness and area per lipid. Overall, this study highlights the importance of surface charge and membrane fluidity in influencing the extent of protein adsorption. We hope that our investigation will be a valuable contribution to better understanding protein-vesicle interactions for improved nanocarrier design.

Co-encapsulation of fisetin and cisplatin into liposomes: Stability considerations and in vivo efficacy on lung cancer animal model

Lung cancer is a highly vascularized tumor for which a combination between an antitumor agent, cisplatin, and an antiangiogenic molecule, fisetin, appears a promising therapeutic approach. In order to deliver both chemotherapies within the tumor, to enhance fisetin solubility and decrease cisplatin toxicity, an encapsulation of both drugs into liposomes was developed. Purification and freeze-drying protocols were optimized to improve both the encapsulation and liposome storage. The cytotoxicity of the encapsulated chemotherapies was evaluated on Lewis lung carcinoma (3LL) cell lines. The antitumor effect of the combination was evaluated in vivo on an ectopic mouse model of Lewis Lung carcinoma. The results showed that fisetin and cisplatin co-loaded liposomes were successfully prepared. Freeze-drying allowed a 30 days storage limiting the release of both drugs. The combination index between liposomal fisetin and liposomal cisplatin on 3LL cell line after 24 h of exposure showed a clear synergism: CI = 0.7 for the co loaded liposomes and CI = 0.9 for the mixture of cisplatin loaded and fisetin loaded liposomes. The co-encapsulating formulation showed in vivo efficacy against an ectopic murine model of Lewis Lung carcinoma with a probable reduction in the toxicity of cisplatin through co-encapsulation with fisetin.

Evaluation of Quatsome Morphology, Composition, and Stability for Pseudomonas aeruginosa Biofilm Eradication

Biofilm infections are a major cause of food poisoning and hospital-acquired infections. Quaternary ammonium compounds are a group of effective disinfectants widely used in industry and households, yet their efficacy is lessened when used as antibiofilm agents compared to that against planktonic bacteria. It is therefore necessary to identify alternative formulations of quaternary ammonium compounds to achieve an effective biofilm dispersal. Quaternary ammonium amphiphiles can form vesicular structures termed "quatsomes" in the presence of cholesterol. In addition to their intrinsic antimicrobial properties, quatsomes can also be used for the delivery of other types of antibiotics or biomarkers. In this study, quatsomes were prepared from binary mixtures of cholesterol and mono- or dialkyl-quaternary ammonium compounds; then, the integrity and stability of their vesicular structure were assessed and related to monomer chain number and chain length. The quatsomes were used to treat Pseudomonas aeruginosa biofilms, showing effective antibiofilm abilities comparable to those of their monomers. A systematic liquid chromatography-mass spectrometry method for quantifying quatsome vesicle components was also developed and used to establish the significance of cholesterol in the quatsome self-assembly processes.

Dual-Color Real-Time Chemosensing of a Compartmentalized Reaction Network Involving Enzyme-Induced Membrane Permeation of Peptides

The design of synthetic systems with interrelated reaction sequences that model incipient biological complexity is limited by physicochemical tools that allow the direct monitoring of the individual processes in real-time. To mimic a simple digestion-resorption sequence, the authors have designed compartmentalized liposomal systems that incorporate extra- and intravesicular chemosensing ensembles. The extravesicular reporter pair consists of cucurbit[7]uril and methylene blue to monitor the enzymatic cleavage of short enkephalin-related peptides by thermolysin through a switch-off fluorescence response ("digestion"). Because the substrate is membrane-impermeable, but the dipeptide product is permeable, uptake of the latter into the pre-formed liposomes occurs as a follow-up process. The intravesicular chemosensing ensemble consists of i) cucurbit[8]uril, 2-anilinonaphthalene-6-sulfonic acid, and methyl viologen or ii) cucurbit[7]uril and berberine to monitor the uptake ("resorption") of the enzymatic products through the liposomal membranes by i) a switch-on or ii) a switch-off fluorescence response. The dyes are designed to allow selective optical excitation and read-out of the extra- and intravesicular dyes, which allow for dual-color chemosensing and, therefore, kinetic discrimination of the two sequential reactions.

A Biomimetic Multiparametric Assay to Characterise Anti-Amyloid Drugs

Alzheimer's disease (AD) is the most widespread form of senile dementia worldwide and represents a leading socioeconomic problem in healthcare. Although it is widely debated, the aggregation of the amyloid β peptide (Aβ) is linked to the onset and progression of this neurodegenerative disease. Molecules capable of interfering with specific steps in the fibrillation process remain of pharmacological interest. To identify such compounds, we have set up a small molecule screening process combining multiple experimental methods (UV and florescence spectrometry, ITC, and ATR-FTIR) to identify and characterise potential modulators of Aβ1-42 fibrillation through the description of the biochemical interactions (molecule-membrane Aβ peptide). Three known modulators, namely bexarotene, Chicago sky blue and indomethacin, have been evaluated through this process, and their modulation mechanism in the presence of a biomembrane has been described. Such a well-adapted physico-chemical approach to drug discovery proves to be an undeniable asset for the rapid characterisation of compounds of therapeutic interest for Alzheimer's disease. This strategy could be adapted and transposed to search for modulators of other amyloids such as tau protein.

Investigation into the mechanism of action of the antimicrobial peptide epilancin 15X

Addressing the current antibiotic-resistance challenge would be aided by the identification of compounds with novel mechanisms of action. Epilancin 15X, a lantibiotic produced by Staphylococcus epidermidis 15 × 154, displays antimicrobial activity in the submicromolar range against a subset of pathogenic Gram-positive bacteria. S. epidermidis is a common member of the human skin or mucosal microbiota. We here investigated the mechanism of action of epilancin 15X. The compound is bactericidal against Staphylococcus carnosus as well as Bacillus subtilis and appears to kill these bacteria by membrane disruption. Structure-activity relationship studies using engineered analogs show that its conserved positively charged residues and dehydroamino acids are important for bioactivity, but the N-terminal lactyl group is tolerant of changes. Epilancin 15X treatment negatively affects fatty acid synthesis, RNA translation, and DNA replication and transcription without affecting cell wall biosynthesis. The compound appears localized to the surface of bacteria and is most potent in disrupting the membranes of liposomes composed of negatively charged membrane lipids in a lipid II independent manner. Epilancin 15X does not elicit a LiaRS response in B. subtilis but did upregulate VraRS in S. carnosus. Treatment of S. carnosus or B. subtilis with epilancin 15X resulted in an aggregation phenotype in microscopy experiments. Collectively these studies provide new information on epilancin 15X activity.

Increased delivery and cytotoxicity of doxorubicin in HeLa cells using the synthetic cationic peptide pEM-2 functionalized liposomes

HYPOTHESIS

Due to the inability of nano-carriers to passively cross the cell membrane, cell penetration enhancers are used to accelerate cytoplasmic delivery of antineoplastic drugs. In this regard, snake venom phospholipase A2 peptides are known for their ability to destabilize natural and artificial membranes. In this context, functionalized liposomes with peptide pEM-2 should favor the incorporation of doxorubicin and increase its cytotoxicity in HeLa cells compared to free doxorubicin, and doxorubicin encapsulated in non-functionalized liposomes.

EXPERIMENTS

Several characteristics were monitored, including doxorubicin loading capacity of the liposomes, as well as the release and uptake before and after functionalization. Cell viability and half-maximal inhibition concentrations were determined in HeLa cells.

FINDINGS

In vitro studies showed that functionalization of doxorubicin-loaded PC-NG liposomes with pEM-2 not only improved the amount of doxorubicin delivered compared to free doxorubicin or other doxorubicin-containing formulations, but also showed enhanced cytotoxicity against HeLa cells. The PC-NG liposomes loaded with doxorubicin improved treatment efficacy by reducing the IC₅₀ value and incubation time. This increase in cell toxicity was directly related to the concentration of pEM-2 peptide bound to the liposomes. We conclude that the cytotoxicity observed in HeLa cells due to the action of doxorubicin was strongly favored when encapsulated in synthetic liposomes and functionalized with the pEM-2 peptide.

Skin drug delivery using lipid vesicles: A starting guideline for their development

Lipid vesicles can provide a cost-effective enhancement of skin drug absorption when vesicle production process is optimised. It is an important challenge to design the ideal vesicle, since their properties and features are related, as changes in one affect the others. Here, we review the main components, preparation and characterization methods commonly used, and the key properties that lead to highly efficient vesicles for transdermal drug delivery purposes. We stand by size, deformability degree and drug loading, as the most important vesicle features that determine the further transdermal drug absorption. The interest in this technology is increasing, as demonstrated by the exponential growth of publications on the topic. Although long-term preservation and scalability issues have limited the commercialization of lipid vesicle products, freeze-drying and modern escalation methods overcome these difficulties, thus predicting a higher use of these technologies in the market and clinical practice.

Encapsulation of Vitamin C by Glycerol-Derived Dendrimers, Their Interaction with Biomimetic Models of Stratum corneum and Their Cytotoxicity

Vitamin C is one of the most sensitive cosmetic active ingredients. To avoid its degradation, its encapsulation into biobased carriers such as dendrimers is one alternative of interest. In this work, we wanted to evaluate the potential of two biobased glycerodendrimer families (GlyceroDendrimers-Poly(AmidoAmine) (GD-PAMAMs) or GlyceroDendrimers-Poly(Propylene Imine) (GD-PPIs)) as a vitamin C carrier for topical application. The higher encapsulation capacity of GD-PAMAM-3 compared to commercial PAMAM-3 and different GD-PPIs, and its absence of cytotoxicity towards dermal cells, make it a good candidate. Investigation of its mechanism of action was done by using two kinds of biomimetic models of stratum corneum (SC), lipid monolayers and liposomes. GD-PAMAM-3 and VitC@GD-PAMAM-3 (GD-PAMAM-3 with encapsulated vitamin C) can both interact with the lipid representatives of the SC lipid matrix, whichever pH is considered. However, only pH 5.0 is suggested to be favorable to release vitamin C into the SC matrix. Their binding to SC-biomimetic liposomes revealed only a slight effect on membrane permeability in accordance with the absence of cytotoxicity but an increase in membrane rigidity, suggesting a reinforcement of the SC barrier property. Globally, our results suggest that the dendrimer GD-PAMAM-3 could be an efficient carrier for cosmetic applications.

Ultrafast water permeation through nanochannels with a densely fluorous interior surface

Ultrafast water permeation in aquaporins is promoted by their hydrophobic interior surface. Polytetrafluoroethylene has a dense fluorine surface, leading to its strong water repellence. We report a series of fluorous oligoamide nanorings with interior diameters ranging from 0.9 to 1.9 nanometers. These nanorings undergo supramolecular polymerization in phospholipid bilayer membranes to form fluorous nanochannels, the interior walls of which are densely covered with fluorine atoms. The nanochannel with the smallest diameter exhibits a water permeation flux that is two orders of magnitude greater than those of aquaporins and carbon nanotubes. The proposed nanochannel exhibits negligible chloride ion (Cl^-) permeability caused by a powerful electrostatic barrier provided by the electrostatically negative fluorous interior surface. Thus, this nanochannel is expected to show nearly perfect salt reflectance for desalination.

Formation of Oxidation- and Acid-Sensitive Assemblies from Sterols and a Quaternary Ammonium Ferrocene Derivative: Quatsome- and Onion-like Vesicles and Extended Nanoribbons

Quatsomes are a class of nonphospholipid vesicles in which bilayers are formed from mixtures of quaternary ammonium (QA) amphiphiles and sterols. We describe the formation of oxidation and acid-sensitive quatsome-like vesicles and other bilayer assemblies from mixtures of a ferrocenylated QA amphiphile (FTDMA) and several cholesterol derivatives. The influence of the sterol and the preparation method (extrusion or probe sonication) on the stability and morphology of the resulting vesicles is explored; a variety of structures can be obtained from small (ca. 30 nm) spherical unilamellar and oligolamellar quatsome-like vesicles to large (ca. 200 nm) multilamellar onion-like vesicles to extended nanoribbons many micrometers long. FTDMA-sterol vesicles undergo drastic shifts in vesicle and membrane structure when treated with a chemical oxidant (Frémy's salt), a feature previously observed in liposomes containing FTDMA and now confirmed in nonphospholipid vesicles. Size distributions of spherical quatsome-like vesicles obtained from cryo-TEM are examined to estimate the membrane bending rigidity, and a hypothesis is presented to explain the underlying mechanism of the profound membrane alterations observed as a consequence of ferrocene oxidation.

EDTA-Gradient Loading of Doxorubicin into Ferrocene-Containing Liposomes: Effect of Lipid Composition and Visualization of Triggered Release by Cryo-TEM

Efficient delivery of therapeutic compounds to their sites of action has been a ubiquitous concern throughout the history of human medicine. The tumor microenvironment offers a variety of endogenous stimuli that may be exploited by a responsive nanocarrier, including heterogeneities in redox potential. In the early stages of the design of such responsive delivery systems, it is necessary to develop a comprehensive understanding of the biophysical mechanism by which the stimulus response occurs, as well as how the response may change from the inclusion of cargo compounds. We describe the optimization of lipid compositions for liposomes containing synthetic ferrocene-appended lipids to achieve highly efficient loading of doxorubicin via an ethylenediaminetetraacetic acid (EDTA) gradient. Liposomes containing ferrocenylated phospholipid are shown to be unstable to the loading conditions, while those including a ferrocenylated alkylammonium amphiphile obtain a near-quantitative loading efficiency. Calorimetric studies demonstrate that this instability is the consequence of the relative degree of lipid hydrolysis that occurs under the acidic loading conditions. Drug-loaded liposomes of the optimized composition are studied by cryo-TEM; the presence of doxorubicin aggregates is observed inside vesicles, and doxorubicin release, as well as the changes in membrane structure resulting from oxidant treatment, is also observed by cryogenic transmission electron microscopy (cryo-TEM). These results further demonstrate the potential of ferrocene lipids in the design of redox-responsive nanocarriers and begin to explore their possible role as probes of membrane dynamics.

β-Amyloid peptide interactions with biomimetic membranes: A multiparametric characterization

Alzheimer's disease is the most common form of senile dementia in the world, and amyloid β peptide1-42 (Aβ_1-42) is one of its two principal biological hallmarks. While interactome concept was getting forward the scientific community, we proposed that the study of the molecular interactions of amyloid β peptide with the biological membranes will allow to highlight underlying mechanisms responsive of AD. We have developed two simple liposomal formulations (phosphatidylcholine, cholesterol, phosphatidylglycerol) mimicking neuronal cell membrane (composition, charge, curvature radius). Interactions with Aβ_1-42 and mutant oG37C, a stable oligomeric form of the peptide, were characterized according to a simple multiparametric procedure based on ThT fluorescence, liposome leakage assay, ATR-FTIR spectroscopy. Kinetic aggregation, membrane damage and peptide conformation provided our first methodologic bases to develop an original model to describe interactions of Aβ peptide and lipids.

Membrane Permeability and Its Activation Energies in Dependence on Analyte, Lipid, and Phase Type Obtained by the Fluorescent Artificial Receptor Membrane Assay

Time-resolved monitoring of the permeability of analytes is of utmost importance in membrane research. Existing methods are restricted to single-point determinations or flat synthetic membranes, limiting access to biologically relevant kinetic parameters (permeation rate constant, permeation coefficients). We now use the recently introduced fluorescent artificial receptor membrane assay (FARMA) as a method to monitor, in real time, the permeation of indole derivatives through liposomal membranes of different lipid compositions. This method is based on the liposomal encapsulation of a chemosensing ensemble or "fluorescent artificial receptor", consisting of 2,7-dimethyldiazapyrenium as a fluorescent dye and cucurbit[8]uril as the macrocyclic receptor, that responds to the complexation of a permeating aromatic analyte by fluorescence quenching. FARMA does not require a fluorescent labeling of the analytes and allows access to permeability coefficients in the range from 10^-8 to 10^-4 cm s^-1. The effect of temperature on the permeation rate of a series of indole derivatives across the phospholipid membranes was studied. The activation energies for permeation through POPC/POPS phospholipid membranes were in the range of 28-96 kJ mol^-1. To study the effect of different lipid phases on the membrane permeability, we performed experiments with DPPC/DOPS vesicles, which showed a phase transition from a gel phase to a liquid-crystalline phase, where the activation energies for the permeation process were expected to show a dramatic change. Accordingly, for the permeation of the indole derivatives into the DPPC/DOPS liposomes, discontinuities were observed in the Arrhenius plots, from which the permeation activation energies for the distinct phases could be determined, for example, for tryptamine 245 kJ mol^-1 in the gel phase and 47 kJ mol^-1 in the liquid-crystalline phase.

Non-disruptive uptake of anionic and cationic gold nanoparticles in neutral zwitterionic membranes

The potential toxicity of ligand-protected nanoparticles (NPs) on biological targets is crucial for their clinical translation. A number of studies are aimed at investigating the molecular mechanisms shaping the interactions between synthetic NPs and neutral plasma membranes. The role played by the NP surface charge is still widely debated. We compare, via liposome leakage assays, the perturbation induced by the penetration of sub-6 nm anionic and cationic Au NPs into model neutral lipid membranes composed of the zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Our charged Au NPs are functionalized by a mixture of the apolar 1-octanethiol and a ω-charged thiol which is either the anionic 11-mercapto-1-undecanesulfonate or the cationic (11-mercaptoundecyl)-N,N,N-trimethylammonium. In both cases, the NP uptake in the bilayer is confirmed by quartz crystal microbalance investigations. Our leakage assays show that both negatively and positively charged Au NPs do not induce significant membrane damage on POPC liposomes when penetrating into the bilayer. By means of molecular dynamics simulations, we show that the energy barrier for membrane penetration is the same for both NPs. These results suggest that the sign of the NP surface charge, per se, does not imply different physicochemical mechanisms of interaction with zwitterionic lipid membranes.

Molecular engineering of antibodies for site-specific conjugation to lipid polydopamine hybrid nanoparticles

Conjugation of antibodies to nanoparticles allows specific cancer targeting, but conventional conjugation methods generate heterogeneous conjugations that cannot guarantee the optimal orientation and functionality of the conjugated antibody. Here, a molecular engineering technique was used for site-specific conjugation of antibodies to nanoparticles. We designed an anti-claudin 3 (CLDN3) antibody containing a single cysteine residue, h4G3cys, then linked it to the maleimide group of lipid polydopamine hybrid nanoparticles (LPNs). Because of their negatively charged lipid coating, LPNs showed high colloidal stability and provided a functional surface for site-specific conjugation of h4G3cys. The activity of h4G3cys was tested by measuring the binding of h4G3cys-conjugated LPNs (C-LPNs) to CLDN3-positive tumor cells and assessing its subsequent photothermal effects. C-LPNsspecifically recognized CLDN3-overexpressing T47D breast cancer cells but not CLDN3-negative Hs578T breast cancer cells. High binding of C-LPNs to CLDN3-overexpressing T47D cells resulted in significantly higher temperature generation upon NIR irradiation and potent anticancer photothermal efficacy. Consistent with this, intravenous injection of C-LPNsin a T47D xenograft mouse model followed by NIR irradiation caused remarkable tumor ablation compared with other treatments through high temperature increases. Our results establish an accurate antibody-linking method and demonstrate the possibility of developing therapeutics using antibody-guided nanoparticles.

Light Scattering as an Easy Tool to Measure Vesicles Weight Concentration

Over the last few decades, liposomes have emerged as promising drug delivery systems and effective membrane models for studying biophysical and biological processes. For all applications, knowing their concentration after preparation is crucial. Thus, the development of methods for easily controlling vesicles concentration would be of great utility. A new assay is presented here, based on a suitable analysis of light scattering intensity from liposome dispersions. The method, tested for extrusion preparations, is precise, easy, fast, non-destructive and uses a tiny amount of sample. Furthermore, the scattering intensity can be measured indifferently at different angles, or even by using the elastic band obtained from a standard spectrofluorimeter. To validate the method, the measured concentrations of vesicles of different matrix compositions and sizes, measured by light scattering with different angles and instruments, were compared to the data obtained by the standard Stewart assay. Consistent results were obtained. The light scattering assay is based on the assessment of the mass fraction lost in the preparation, and can be applied for methods such as extrusion, homogenization, French press and other microfluidic procedures.

The Why, Where, Who, How, and What of the vesicular delivery systems

Though vesicular delivery systems have been widely explored and reviewed, no comprehensive review exists that covers their development from the inception of the concept to its culmination in the form of regulated marketed formulations. With the advancement of scientific research in the field of nanomedicine, certain category of vesicular delivery systems have successfully reached the global market. Despite extensive research and highly encouraging results in a plethora of pathological conditions in the preclinical studies, translation of these nanomedicines from laboratory to market has been very limited. Aim of this review is to describe comprehensively the various colloidal delivery systems, focusing mainly on their conventional and advanced methods of preparation, different characterization techniques and main success stories of their journey from bench to bedside of the patient. The review also touches the finer nuances of the use of modern formulation approach of DoE (Design of Experiments) in their formulation and the status of regulatory guidelines for the approval of these nanomedicines.

A selective calix[6]arene-based fluorescent chemosensor for phosphatidylcholine type lipids

The development of chemosensors that can selectively detect phosphatidylcholines (PCs) in biological samples is of medical relevance considering the importance of these phospholipids in cell growth and survival. Their selective sensing over phosphatidylethanolamines (PEs) is however a challenging task. We report here on the chemosensing capacities of calix[6]tris-pyrenylurea 1, which is able to selectively interact with phosphatidylcholine-type lipids in organic media. Host 1 also binds them in a biphasic chloroform/water solution, opening the way to the design of selective chemosensors for these lipids in biological media. The results obtained by NMR, fluorescence spectroscopy and modelling studies show that the selectivity is the result of the high degree of complementarity between the lipids' zwitterionic phosphatidylcholine headgroup and the receptor's H-bonding donor site and hydrophobic pocket. The mode of recognition is reminiscent of natural systems, such as human phosphatidylcholine transfer proteins (PC-TPs), validating the biomimetic approach adopted in our work.

Triggered Release from Lipid Bilayer Vesicles by an Artificial Transmembrane Signal Transduction System

The on-demand delivery of drug molecules from nanoscale carriers with spatiotemporal control is a key challenge in modern medicine. Here we show that lipid bilayer vesicles (liposomes) can be triggered to release an encapsulated molecular cargo in response to an external control signal by employing an artificial transmembrane signal transduction mechanism. A synthetic signal transducer embedded in the lipid bilayer membrane acts as a switchable catalyst, catalyzing the formation of surfactant molecules inside the vesicle in response to a change in external pH. The surfactant permeabilizes the lipid bilayer membrane to facilitate release of an encapsulated hydrophilic cargo. In the absence of the pH control signal, the catalyst is inactive, and the cargo remains encapsulated within the vesicle.

Liposome Disruption Assay to Examine Lytic Properties of Biomolecules

Proteins may have three dimensional structural or amino acid features that suggest a role in targeting and disrupting lipids within cell membranes. It is often necessary to experimentally investigate if these proteins and biomolecules are able to disrupt membranes in order to conclusively characterize the function of these biomolecules. Here, we describe an in vitro assay to evaluate the membrane lytic properties of proteins and biomolecules. Large unilamellar vesicles (liposomes) containing carboxyfluorescein at fluorescence-quenching concentrations are treated with the biomolecule of interest. A resulting increase in fluorescence due to leakage of the dye from liposomes and subsequent dilution in the buffer demonstrates that the biomolecule is sufficient for disrupting liposomes and membranes. Additionally, since liposome disruption may occur via pore-formation or via general solubilization of lipids similar to detergents, we provide a method to distinguish between these two mechanisms. Pore-formation can be identified and evaluated by examining the blockade of carboxyfluorescein release with dextran molecules that fit the pore. The methods described here were used to determine that the malaria vaccine candidate CelTOS and proapoptotic Bax disrupt liposomes by pore formation (Saito et al., 2000; Jimah et al., 2016). Since membrane lipid binding by a biomolecule precedes membrane disruption, we recommend the companion protocol: Jimah et al., 2017.