Cationic triple-chain amphiphiles facilitate vesicle fusion compared to double-chain or single-chain analogues

Effective mRNA transfection of tumor cells using cationic triacyl lipid‑based mRNA lipoplexes

Previously, it was reported that mRNA/cationic liposome complexes (mRNA lipoplexes) composed of the cationic triacyl lipid, 11-((1,3-bis(dodecanoyloxy)-2-((dodecanoyloxy)methyl)propan-2-yl)amino)-N,N,N- trimethyl-11-oxoundecan-1-aminium bromide (TC-1-12), with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine and poly(ethylene glycol) cholesteryl ether, induce high protein expression in human cervical carcinoma HeLa cells. In the present study, the authors aimed to optimize mRNA transfection using TC-1-12-based mRNA lipoplexes. mRNA lipoplexes were prepared at various charge ratios (+:-) using modified ethanol injection (MEI) and thin-film hydration (TFH) methods and compared the protein expression efficiency after transfection of HeLa cells with the developed mRNA lipoplexes. Firefly luciferase (FLuc) and enhanced green fluorescent protein (EGFP) mRNA lipoplexes prepared using the MEI method exhibited higher Luc and EGFP expression levels in cells than those prepared using the TFH method. Moreover, FLuc mRNA lipoplexes prepared using the MEI and TFH methods at charge ratios of 3:1 and 4:1, respectively, exhibited the highest Luc expression in cells. However, transfection with mRNA lipoplexes using the MEI and TFH methods induced moderate cytotoxicity in HeLa cells (46 and 57% cell viability, respectively). Furthermore, Cy5-labeled mRNA lipoplexes, which were prepared using the MEI method, showed higher cellular uptake of mRNA than those prepared using the TFH method. In the transfection of FLuc mRNA lipoplexes prepared using the MEI method, the storage of the lipid-ethanol solution at 37˚C for 4 months did not decrease Luc expression in HeLa cells. Additionally, FLuc mRNA lipoplexes prepared using the MEI method, induced relatively high Luc expression in human prostate carcinoma PC-3 and human liver cancer HepG2 cells with low cytotoxicity (103 and 81% cell viability, respectively). Overall, the results highlighted the potential of TC-1-12-based mRNA lipoplexes prepared using the MEI method for efficient mRNA delivery to cells.

Efficient mRNA Delivery with mRNA Lipoplexes Prepared Using a Modified Ethanol Injection Method

Messenger RNA (mRNA)-based therapies are a novel class of therapeutics used in vaccination and protein replacement therapies for monogenic diseases. Previously, we developed a modified ethanol injection (MEI) method for small interfering RNA (siRNA) transfection, in which cationic liposome/siRNA complexes (siRNA lipoplexes) were prepared by mixing a lipid-ethanol solution with a siRNA solution. In this study, we applied the MEI method to prepare mRNA lipoplexes and evaluated the in vitro and in vivo protein expression efficiencies. We selected six cationic lipids and three neutral helper lipids to generate 18 mRNA lipoplexes. These were composed of cationic lipids, neutral helper lipids, and polyethylene glycol-cholesteryl ether (PEG-Chol). Among them, mRNA lipoplexes containing N-hexadecyl-N,N-dimethylhexadecan-1-aminium bromide (DC-1-16) or 11-((1,3-bis(dodecanoyloxy)-2-((dodecanoyloxy)methyl) propan-2-yl) amino)-N,N,N-trimethyl-11-oxoundecan-1-aminium bromide (TC-1-12) with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) and PEG-Chol exhibited high protein expression in cells. Furthermore, mRNA lipoplexes composed of DC-1-16, DOPE, and PEG-Chol exhibited high protein expression in the lungs and spleen of mice after systemic injection and induced high antigen-specific IgG1 levels upon immunization. These results suggest that the MEI method can potentially increase the efficiency of mRNA transfection, both in vitro and in vivo.

Palladium responsive liposomes for triggered release of aqueous contents

Palladium (Pd) is a promising metal catalyst for novel bioorthogonal chemistry and prodrug activation. This report describes the first example of palladium responsive liposomes. The key molecule is a new caged phospholipid called Alloc-PE that forms stable liposomes (large unilamellar vesicles, ∼220 nm diameter). Liposome treatment with PdCl2 removes the chemical cage, liberates membrane destabilizing dioleoylphosphoethanolamine (DOPE), and triggers liposome leakage of encapsulated aqueous contents. The results indicate a path towards liposomal drug delivery technologies that exploit transition metal triggered leakage.

Optimal combination of cationic lipid and phospholipid in cationic liposomes for gene knockdown in breast cancer cells and mouse lung using siRNA lipoplexes

Formulation of cationic liposomes is a key factor that determine the gene knockdown efficiency by cationic liposomes/siRNA complexes (siRNA lipoplexes). Here, to determine the optimal combination of cationic lipid and phospholipid in cationic liposomes for in vitro and in vivo gene knockdown using siRNA lipoplexes, three types of cationic lipid were used, namely 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), dimethyldioctadecylammonium bromide (DDAB) and 11-[(1,3-bis(dodecanoyloxy)-2-((dodecanoyloxy)methyl)propan-2-yl)amino]-N,N,N-trimethyl-11-oxoundecan-1-aminium bromide (TC-1-12). Thereafter, 30 types of cationic liposome composed of each cationic lipid with phosphatidylcholine or phosphatidylethanolamine containing saturated or unsaturated dialkyl chains (C14, C16, or C18) were prepared. The inclusion of phosphatidylethanolamine containing unsaturated and long dialkyl chains with DOTAP- or DDAB-based cationic liposomes induced strong luciferase gene knockdown in human breast cancer MCF-7-Luc cells stably expressing luciferase gene. Furthermore, the inclusion of phosphatidylcholine or phosphatidylethanolamine containing saturated and short dialkyl chains or unsaturated and long dialkyl chains into TC-1-12-based cationic liposomes resulted in high gene knockdown efficacy. When cationic liposomes composed of DDAB/1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), TC-1-12/DOPE and TC-1-12/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine were used, significant gene knockdown occurred in the lungs of mice following systemic injection of siRNA lipoplexes. Overall, the present findings indicated that optimal phospholipids in cationic liposome for in vitro and in vivo siRNA transfection were affected by the types of cationic lipid used.

Reactivity and fusion between cationic vesicles and fatty acid anionic vesicles

The fusion between synthetic vesicles is an interesting mechanism for the stepwise construction of vesicle compartments for origins of life models and synthetic biology. In this communication, we report an innovative study on the not well-known case of fusion between oppositely charged vesicles, in particular by using fatty acid vesicles and DDAB as cationic surfactant. By combining fluorescence, turbidity vs. time profiles and vesicle size distribution obtained by dynamic light scattering, we show that POPC/oleate 1/4 mol/mol anionic vesicles can be fused with POPC/DDAB 1/1 mol/mol cationic vesicles with about 20% yield. Other non-fusion processes also occur, vesicle fusion being more effective by reducing the ionic strength of the buffer. This study also contributes to clarify the term "vesicle fusion", which is not always properly used in describing reactivity among vesicles.

pH-sensitive vesicles containing a lipidic beta-amino acid with two hydrophobic chains

The lipidic beta-amino acid 2-(aminomethyl)-2-pentadecylheptadecanoic acid (1) was synthesized via the alkylation of the C(alpha)-atom of fully protected beta-alanine. Mixed large unilamellar vesicles with a diameter between 100 and 200 nm containing POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and 1 at a molar ratio of 9 : 1 were prepared and found to have a surface charge which is dependent on pH. At slightly acidic pH, the vesicles were positively charged, and at alkaline pH negatively charged. Dynamic light scattering, zeta potential, and cryo-transmission electron-microscopy measurements indicated that the mixed vesicles fused at pH 4-5 with negatively charged mixed vesicles composed of POPC and POPG (9.8 : 1, molar ratio), POPG being 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)].

[Positively charged acyl derivatives of carbohydrates as promising transfection agents]

A convenient approach to the synthesis of mono- and polycationic glycolipid amphiphiles is suggested. The compounds obtained can be used for study of the structure-activity relationship and determination of the effect of hydrophobic and cationic domains on transfection efficiency.

The effect of PS content on the ability of natural membranes to fuse with positively charged liposomes and lipoplexes

Supramolecular aggregates containing cationic lipids have been widely used as transfection mediators due to their ability to interact with negatively charged DNA molecules and biological membranes. First steps of the process leading to transfection are partly electrostatic, partly hydrophobic interactions of liposomes/lipoplexes with cell and/or endosomal membrane. Negatively charged compounds of biological membranes, namely glycolipids, glycoproteins and phosphatidylserine (PS), are responsible for such events as adsorption, hemifusion, fusion, poration and destabilization of natural membranes upon contact with cationic liposomes/lipoplexes. The present communication describes the dependence of interaction of cationic liposomes with natural and artificial membranes on the negative charge of the target membrane, charges which in most cases were generated by charging the PS content or its exposure. The model for the target membranes were liposomes of variable content of PS or PG (phosphatidylglycerol) and erythrocyte membranes in which the PS and other anionic compound content/exposure was modified in several ways. Membranes of increased anionic phospholipid content displayed increased fusion with DOTAP (1,2-dioleoyl-3-trimethylammoniumpropane) liposomes, while erythrocyte membranes partly depleted of glycocalix, its sialic acid, in particular, showed a decreased fusion ability. The role of the anionic component is also supported by the fact that erythrocyte membrane inside-out vesicles fused easily with cationic liposomes. The data obtained on erythrocyte ghosts of normal and disrupted asymmetry, in particular, those obtained in the presence of Ca(2+), indicate the role of lipid flip-flop movement catalyzed by scramblase. The ATP-depletion of erythrocytes also induced an increased sensitivity to hemoglobin leakage upon interactions with DOTAP liposomes. Calcein leakage from anionic liposomes incubated with DOTAP liposomes was also dependent on surface charge of the target membranes. In all experiments with the asymmetric membranes the fusion level markedly increased with an increase of temperature, which supports the role of membrane lipid mobility. The decrease in positive charge by binding of plasmid DNA and the increase in ionic strength decreased the ability of DOTAP liposomes/lipoplexes to fuse with erythrocyte ghosts. Lower pH promotes fusion between erythrocyte ghosts and DOTAP liposomes and lipoplexes. The obtained results indicate that electrostatic interactions together with increased mobility of membrane lipids and susceptibility to form structures of negative curvature play a major role in the fusion of DOTAP liposomes with natural and artificial membranes.

Synthesis and supramolecular properties of conformationally restricted and flexible phospholipids

Short synthetic routes are described to produce structurally related phospholipids that are either conformationally restricted or flexible. The conformationally restricted structures have a cyclopropyl ring in the interfacial region of the phospholipid. The key synthetic step is a cyclopropanation reaction between 2(5H)-furanone and a stabilized chloroallylic phosphonate anion. The synthetic routes enable the incorporation of different polar headgroups as well as nonpolar tails at late stages in the sequence. The phosphoethanolamine derivatives 1b and 2b readily form encapsulating vesicles, however, dye leakage from vesicles composed of the restricted phospholipid 1b is significantly slower than from vesicles composed of flexible analogue 2b. Physicochemical analyses using 31P NMR, differential scanning calorimetry, fluorescence anisotropy, and Langmuir-Blodgett films suggest that the decreased permeability of membranes composed of conformationally restricted 1b is due to its ability to pack more closely in a bilayer assembly.

Interaction of the water-soluble protein aprotinin with liposomes: gel-filtration, turbidity studies, and 31P NMR studies

The interactions of a water-soluble nonmembrane protein aprotinin with multilamellar vesicles (MLV) and small unilamellar vesicles (SUV) from soybean phospholipids were studied using Sephadex G-75 gel chromatography combined with different methods of the analysis of the eluate fractions (fluorescence, light-scattering, turbidity; 31P NMR spectroscopy). The composition of the liposomes mainly containing soybean phosphatidylcholine (PC) was varied by the addition of phosphatidylethanolamine (PE), phosphatidylinositol (PI) and lyso-phosphatidylcholine (lyso-PC). To evaluate the lipid-protein interactions, the amount of aprotinin in the MLV-aprotinin complexes was determined. Lipid-protein interactions were found to strongly depend on the liposome composition, medium pH and ionic strength. These dependencies point to the electrostatic nature of the aprotinin-lipid interactions. 31P NMR spectroscopy of the MLV-aprotinin complexes indicated that aprotinin influences the phospholipid structure in MLV at pH 3.0. In the case of PC:PE:PI and PC:PE:PI:lyso-PC vesicles, aprotinin induced liposome aggregation and a lamellar-to-isotropic phase transition of the phospholipids.