Modulating the lipid profile of blastocyst cell membrane with DPPC multilamellar vesicles

The aim of this study was to evaluate the effect of multilamellar vesicles (MLVs) of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in co-culture with in vitro-produced bovine embryos (IVPEs). The stability of five concentrations of MLVs (1.0, 1.25, 1.5, 1.75, and 2.0 mM) produced using ultrapure water or embryonic culture medium with 24 or 48 h of incubation at 38.5 °C with 5% CO₂ was assessed. In addition, the toxicity of MLVs and their modulation of the lipid profile of the plasma membrane of IVPEs were evaluated after 48 h of co-culture. Both media allowed the production of MLVs. Incubation (24 and 48 h) did not impair the MLV structure but affected the average diameter. The rate of blastocyst production was not reduced, demonstrating the nontoxicity of the MLVs even at 2.0 mmol/L. The lipid profile of the embryos was different depending on the MLV concentration. In comparison with control embryos, embryos cultured with MLVs at 2.0 mmol/L had a higher relative abundance of six lipid ions (m/z 720.6, 754.9, 759.0, 779.1, 781.2, and 797.3). This study sheds light on a new culture system in which the MLV concentration could change the lipid profile of the embryonic cell membrane in a dose-dependent manner.

Transferrin-functionalized liposomes loaded with vitamin VB12 for Alzheimer's disease therapy

Despite the efforts of the pharmaceutical and research sectors, Alzheimer's disease (AD) remains incurable, imposing the demand for new effective strategies. Vitamin B12 (VB12) has aroused interest due to its in vitro anti-amyloidogenic properties. However, the high molecular weight and hydrophilicity of VB12 are the main obstacles to its clinical application by hindering its passage through the blood-brain barrier (BBB). In recent years, drug delivery systems (DDSs) capable of transporting molecules across the BBB have gained attention for their effective brain delivery. In this work, VB12-loaded liposomes functionalized with transferrin (Tf) were produced, envisaging the dual-targeting of VB12 to the BBB and neuronal cells, due to the overexpression of Tf receptors in these cells. The produced liposomes presented sizes smaller than 200 nm, with low polydispersity and neutral zeta potential, being suitable for brain delivery. The nanoparticles exhibited an adequate encapsulation efficiency, a sustained release of VB12 for 9 days, and physical stability at storage conditions for up to 2 months. The developed nanosystem was capable of delaying the formation of Aβ fibrils and disrupting mature fibrils, highlighting its great potential for the prevention and treatment of AD.

Interaction of triblock copolymers (Pluronic®) with DMPC vesicles: a photophysical and computational study

Pluronic/lipid mix promises stealth liposomes with long circulation time and long-term stability for pharmaceutical applications. However, the influence of Pluronics on several aspects of lipid membranes has not been fully elucidated. Herein it was described the effect of Pluronics on the structured water, alkyl chain conformation, and kinetic stability of dimyristoylphosphatidylcholine (DMPC) liposomes using interfacial and deeper fluorescent probes along with computational molecular modeling data. Interfacial water changed as a function of Pluronics' hydrophobicity with polypropylene oxide (PPO) anchoring the copolymers in the lipid bilayer. Pluronics with more than 30-40 PO units had facilitated penetration at the bilayer while shorter PPO favored a more interfacial interaction. Low Pluronic concentrations provided long-term stability of vesicles by steric effects of polyethylene oxide (PEO), but high amounts destabilized the vesicles as a sum of water-bridge cleavage at the polar head group and the reduced alkyl-alkyl interactions among the lipids. The high kinetic stability of Pluronic/DMPC vesicles is a proof-of-concept of its advantages and applicability in nanotechnology over conventional liposome-based pharmaceutical products for future biomedical applications.

Influence of lipid bilayer composition on the activity of antimicrobial quaternary ammonium ionenes, the interplay of intrinsic lipid curvature and polymer hydrophobicity, the role of cardiolipin

Incorporation of hydrophobic component into amphiphilic polycations structure is frequently accompanied by an increase of antimicrobial activity. There is, however, a group of relatively hydrophilic polycations containing quaternary ammonium moieties along mainchain, ionenes, which also display strong antimicrobial and limited hemolytic properties. In this work, an influence of a hydrophobic side group length on antimicrobial mechanism of action is investigated in a series of novel amphiphilic ionenes. High antimicrobial activity was found by determination of minimum inhibitory concentration (MIC) and minimum bactericidal, and fungicidal concentration (MBC and MFC) in both growth media and a buffer. Biocompatibility was estimated by hemolytic and mammalian cells viability assays. Mechanistic studies were performed using large unilamellar vesicles (LUVs) with different lipid composition, as simplified models of cell membranes. The investigated ionenes are potent and selective antimicrobial molecules displaying a decrease of antimicrobial activity correlated with increase of hydrophobicity. Studies using LUVs revealed that the cardiolipin is an essential component responsible for the lipid bilayer permeabilization by investigated ionens. In contrast to relatively hydrophilic ionenes, more hydrophobic polymers showed an ability to stabilize membranes composed of lipids with negative spontaneous curvature in a certain range of polymer to lipid ratio. The results substantially contribute to the understanding of antimicrobial activity of the investigated class of polymers.

Investigation on drug entrapment location in liposomes and transfersomes based on molecular dynamics simulation

In this study, liposome and transfersome were successfully constructed using molecular dynamics simulation. Three drugs with different polarity, including 5-fluorouracil, ligustrazine, and osthole, were selected as model drugs to study the distribution of drugs in lipid vesicles by calculating the radial distribution function and the potential of mean force. The solubility parameters between drugs and different regions in lipid vesicles were calculated to characterize the compatibility of drugs in different regions in lipid vesicles, which provided the basis for the conclusion of this paper. It showed that the radial distribution function and the potential of mean force were consistent in the characterization of drug distribution in vesicles, and the drug distribution in vesicles was closely related to the compatibility between drugs and vesicles. Therefore, the radial distribution function and the potential of mean force can be used to characterize the distribution of drugs in vesicles, and molecular simulation technology has a great potential in studying the characteristics of vesicles. Graphical abstract.

Dual-targeting nanovesicles enhance specificity to dynamic tumor cells in vitro and in vivo via manipulation of αvβ3-ligand binding

The dynamic or flowing tumor cells just as leukemia cells and circulating tumor cells face a microenvironment difference from the solid tumors, and the related targeting nanomedicines are rarely reported. The existence of fluidic shear stress in blood circulation seems not favorable for the binding of ligand modified nanodrugs with their target receptor. Namely, the binding feature is very essential in this case. Herein, we utilized HSPC, PEG-DSPE, cholesterol and two αvβ3 ligands (RGDm7 and DT4) with different binding rates to build dual-targeting nanovesicles, in an effort to achieve a “fast-binding/slow-unbinding” function. It was demonstrated that the dual-targeting nanovesicles actualized efficient cellular uptake and antitumor effect in vitro both for static and dynamic tumor cells. Besides, the potency of the dual-targeting vesicles for flowing tumor cells was better than that for static tumor cells. Then, a tumor metastasis mice model and a leukemia mice model were established to detect the killing ability of the drug-loaded dual-targeting vesicles to dynamic tumor cells in vivo. The therapy efficacy of the dual-targeting system was higher than other controls including single-targeting ones. Generally, it seems possible to strengthen drug-targeting to dynamic tumor cells via the control of ligand–receptor interaction.

Ursolic acid loaded intra nasal nano lipid vesicles for brain tumour: Formulation, optimization, in-vivo brain/plasma distribution study and histopathological assessment

The aim was to formulate an optimized ursolic acid (UA) loaded lipid vesicle using formulation by design approach (FbD) for improving the drug targeting by nasal route for brain tumor. Three factors were evaluated at three different levels using anethole (terpene) (A), ethanol (B) and phospholipid90 G (C) as independent variables and their individual and combined effects were observed for PDI (Y1), vesicle size (Y2) and encapsulation efficiency (Y3) to select an optimal system (UALVopt). The optimized formulation was further converted into gel and evaluated for drug release, nasal permeation study, brain/plasma uptake and histopathology study. The UALVopt formulation containing anethole as terpene (1% as A), ethanol (2.6% as B) and phospholipid90 G (8.8 mg as C) showed low PDI (0.212), vesicle size (115.56 nm) and high entrapment efficiency (76.42%). The in-vitro drug release and ex-vivo permeation study results revealed prolonged drug release and permeation. The brain/blood ratio for UALVGopt remained significantly higher at all the time points with respect to UALVopt indicating higher and prolonged retention of drug at site of action. The histopathological study of the nasal mucosa and brain confirmed non-toxic nature of developed formulation. The formulation UALVGopt could serve as a better alternative for the brain targeting via the intranasal route which in turn could subsequently improve its efficacy.

Effects of mono- and di-valent metal cations on the morphology of lipid vesicles

Lipid vesicles are an attractive model membrane experimental platform that is widely used in a biological context. The stability of vesicles can affect their performance and depends on various experimental conditions. How bio-related ions affect vesicle morphology is poorly understood in some cases. Herein, we investigated changes in vesicle morphology influenced by cation in the static and flowing environments. The effects of different mono- and di-valent metal cations on the morphology of lipid vesicles were systematically studied using the various techniques. The results showed that divalent cations caused significant aggregation or fusion of lipid vesicles, but monovalent cations had little effect on the vesicle morphology. Cation binding increased the net surface potential of vesicles, leading to changes in the zeta potential. The same qualitative kinetics were observed for cations that had the same valence at the same ionic strength. However, different types of cations gave different quantitative effects. The order of the ability to destroy the vesicle morphology was Cu²⁺ > Mg²⁺ > Ca²⁺ > Na⁺ > K⁺. These results are of practical value in the use of lipid vesicles as a bionic model, and help to shed light on the role of ions at membrane surfaces and interfaces.

The effect of membrane softeners on rigidity of lipid vesicle bilayers: Derivation from vesicle size changes

Deformability is not just a fundamentally interesting vesicle characteristic; it is also the key determinant of vesicle ability to cross the skin barrier; i.e. skin penetrability. Development of bilayer vesicles for drug and vaccine delivery across the skin should hence involve optimization of this property, which is controllable by the concentration of bilayer softeners in or near the vesicle bilayers. To this end, we propose a simple method for quantifying the effect of bilayer softeners on deformability of bilayer vesicles. The method derives the bending rigidity of vesicle bilayers from vesicle size dependence on softener concentration. To exemplify the method, we studied mixtures of soybean phosphatidylcholine with anionic sodium deoxycholate, non-ionic polyoxyethylene (20) sorbitan oleyl ester (polysorbate 80), or non-ionic polyoxyethylene (20) oleyl ether (C18:1EO20, Brij® 98). With each of the tested bilayer softeners, the bending rigidity of the resulting mixed-amphipat vesicle bilayers decreased quasi-exponentially as the concentration of the bilayer softener increased, as one would expect on theoretical ground. The bilayer bending rigidity reached low values, near the thermal stability limit, i.e. kBT, before vesicle transformation into non-vesicular aggregates began. For a soybean phosphatidylcholine concentration of 5.0mmolkg-1, the bilayer bending rigidity reached 1.5kBT at the total deoxycholate concentration of 4.1mmolkg-1 and 3.4kBT at the total polysorbate 80 concentration of 2.0mmolkg-1. In the case of C18:1EO20, the bilayer bending rigidity reached 1.5kBT at the bilayer surface occupancy α=0.1. The dependence of vesicle size on bilayer softener concentration thus reveals vesicle transformation into different aggregate structures (such as mixed micelles with poor skin penetrability) and practically valuable information on vesicle deformability. Our results compare favorably with results of literature measurements. We provide practical guidance on using the new analytical method to optimize deformable vesicle formulations.

Lipid vesicles in pulsed electric fields: Fundamental principles of the membrane response and its biomedical applications

The present review focuses on the effects of pulsed electric fields on lipid vesicles ranging from giant unilamellar vesicles (GUVs) to small unilamellar vesicles (SUVs), from both fundamental and applicative perspectives. Lipid vesicles are the most popular model membrane systems for studying biophysical and biological processes in living cells. Furthermore, as vesicles are made from biocompatible and biodegradable materials, they provide a strategy to create safe and functionalized drug delivery systems in health-care applications. Exposure of lipid vesicles to pulsed electric fields is a common physical method to transiently increase the permeability of the lipid membrane. This method, termed electroporation, has shown many advantages for delivering exogenous molecules including drugs and genetic material into vesicles and living cells. In addition, electroporation can be applied to induce fusion between vesicles and/or cells. First, we discuss in detail how research on cell-size GUVs as model cell systems has provided novel insight into the basic mechanisms of cell electroporation and associated phenomena. Afterwards, we continue with a thorough overview how electroporation and electrofusion have been used as versatile methods to manipulate vesicles of all sizes in different biomedical applications. We conclude by summarizing the open questions in the field of electroporation and possible future directions for vesicles in the biomedical field.

Platelet microparticle-inspired clot-responsive nanomedicine for targeted fibrinolysis

Intravascular administration of plasminogen activators is a clinically important thrombolytic strategy to treat occlusive vascular conditions. A major issue with this strategy is the systemic off-target drug action, which affects hemostatic capabilities and causes substantial hemorrhagic risks. This issue can be potentially resolved by designing technologies that allow thrombus-targeted delivery and site-specific action of thrombolytic drugs. To this end, leveraging a liposomal platform, we have developed platelet microparticle (PMP)-inspired nanovesicles (PMINs), that can protect encapsulated thrombolytic drugs in circulation to prevent off-target uptake and action, anchor actively onto thrombus via PMP-relevant molecular mechanisms and allow drug release via thrombus-relevant enzymatic trigger. Specifically, the PMINs can anchor onto thrombus via heteromultivalent ligand-mediated binding to active platelet integrin GPIIb-IIIa and P-selectin, and release the thrombolytic payload due to vesicle destabilization triggered by clot-relevant enzyme phospholipase-A2. Here we report on the evaluation of clot-targeting efficacy, lipase-triggered drug release and resultant thrombolytic capability of the PMINs in vitro, and subsequently demonstrate that intravenous delivery of thrombolytic-loaded PMINs can render targeted fibrinolysis without affecting systemic hemostasis, in vivo, in a carotid artery thrombosis model in mice. Our studies establish significant promise of the PMIN technology for safe and site-targeted nanomedicine therapies in the vascular compartment.

Ion concentration effect (Na+ and Cl-) on lipid vesicle formation

Lipid vesicle formation is known to be suppressed in salt solutions, but the mechanism of this phenomenon remains unclear. In order to better understand this issue, the effect of salt concentrations (0-800mM) of sodium chloride on the behavior of L-α-phosphatidylcholine (PC) in aqueous solution was investigated in this work. The results showed that fusion among vesicles, micelles and bilayers may be essential for vesicle formation. With addition of ions and an increase in ion concentration, the lipids became constrained in lateral movement and packed increasingly tightly. The resulted hard supported phospholipid bilayers (SPBs) were thus more difficult to detach from the substrate to form vesicles. These phenomena were tried to be explained at molecular level. Hydrophobic effect is the original cause of lipid vesicle formation, which in fact is absence of attraction between the involved substances. That is to say, the stronger the 3D network was bounded in the medium, the stronger the hydrophobic repulsion on the lipids would be. This might be one reason for the suppression of vesicle formation in salt solution.

Liposome reconstitution and transport assay for recombinant transporters

Secondary active transporters are responsible for the cellular uptake of many biologically important molecules, including neurotransmitters, nutrients, and drugs. Because of their physiological and clinical importance, a method for assessing their transport activity in vitro is necessary to gain a better understanding of how these transporters function at the molecular level. In this chapter, we describe a protocol for reconstituting the concentrative nucleoside transporter from Vibrio cholerae into proteoliposomes. We then describe a radiolabeled substrate uptake assay that can be used to functionally characterize the transporter. These methods are relatively common and can be applied to other secondary active transporters, with or without some modification.