Ilpo Jääskeläinen

Interaction of liposomes with human skin in vitro — The influence of lipid composition and structure

Liposomes have been suggested as a vehicle for dermal and transdermal drug delivery, but the knowledge about the interaction between lipid vesicles and human skin is poor. Therefore, we visualized liposome penetration into the human skin by confocal laser scanning microscopy (CLSM) in vitro. Liposomes were prepared from phospholipids in different compositions and labeled with a fluorescent lipid bilayer marker, N-Rh-PE (L-alpha-phosphatidylethanolamine-N-lissamine rhodamine B sulfonyl). Fluorescently labelled liposomes were not able to penetrate into the granular layers of epidermis. However, the fluorescence from liposome compositions containing DOPE (dioleylphosphatidyl ethanolamine) was able to penetrate deeper into the stratum corneum than that from liposomes without DOPE. Pretreatment of skin with unlabeled liposomes containing DOPE or lyso-phosphatidyl choline (lyso-PC) enhanced the subsequent penetration of the fluorescent markers, N-Rh-PE and sulforhodamine B into the skin, suggesting possible enhancer activity, while most liposomes did not show such enhancement. Resonance energy transfer (RET) and calcein release assay between stratum corneum lipid liposomes (SCLLs) and the phospholipid vesicles suggested that the liposomes containing DOPE may fuse or mix with skin lipids in vitro and loosen the SCLL bilayers, respectively. Among the factors not affecting stratum corneum penetration were: negative charge, cholesterol inclusion and acyl chain length of the phospholipids. In conclusion, fusogenicity of the liposome composition appears to be a prerequisite for the skin penetration.

Comparison of Cell Proliferation and Toxicity Assays Using Two Cationic Liposomes

The present study compares different cytotoxicity and cell proliferation assays including cell morphology, mitochondrial activity, DNA synthesis, and cell viability and toxicity assays. CaSki cells were exposed to two cationic liposomal preparations containing dimethyldioctadecyl-ammonium bromide (DDAB), dioleoylphosphatidylethanolamine (DOPE) and a commercial transfection-reagent DOTAP(N[l-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium-methylsulfate). The results provided by these assays were similar. However, the lactate dehydrogenase assay was more sensitive in measuring early damages of cell membranes than the Trypan blue assay. Also, cell morphology showed early toxic changes, such as cytoplasmic vacuolization and cell shrinking, and it should be included with such toxicity evaluations. DDAB:DOPE was more toxic than DOTAP. The cells treated with DOTAP at 10 µM were surviving as well as the control cells, while DOTAP at 40 µM and DDAB: DOPE at 10 µM had slight toxic effects on CaSki cells. The most toxic effects were seen in CaSki cells after treatment with DDAB: DOPE at 40 µM.

Oligonucleotide-cationic liposome interactions. A physicochemical study

Cationic liposomes are effective in delivering antisense oligonucleotides into cells in culture, but their interactions with the oligonucleotides are poorly understood. We studied the aggregation and fusion reactions during the formation of cationic lipid/oligonucleotide complexes in solution and their interactions with lipid bilayers. Phosphorothioate oligonucleotides (15-mer) were complexed with cationic liposomes composed of dimethyldioctadecylammonium bromide (DDAB) and dioleoylphosphatidylethanolamine (DOPE) at 8:15 molar ratio or of a commercial formulation DOTAP (N-(1-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammoniummethylsul fate), at different ratios with apparent -/+ charge ratios of 0.03-5.6. Mean size of the complexes increased with -/+ ratio so that at charge ratios 0.4-2.0 the size increased by at least an order magnitude due to the oligonucleotide induced aggregation. Resonance energy transfer experiments showed that in addition to aggregation oligonucleotides induced fusion of cationic liposomes, but the fusion was rate-controlled by the initial aggregation step. Rate constants for oligonucleotide induced aggregation were dependent on lipid concentration and were in the range of (0.2-1).10(7) M-1 s-1 and (1-10).10(7) M-1 s-1 for DDAB/DOPE and DOTAP, respectively. Increase in oligonucleotide concentration induced the aggregation and fusion until at high -/+ ratios electrostatic repulsion of negative surfaces inhibited further aggregation and fusion. DOTAP/oligonucleotide complexes did not induce leakage of calcein from neutral EPC liposomes, but did cause leakage at -/+ charge ratios of < 0.7 and > 2.0 from EPC/DOPE liposomes. Also at -/+ charge ratios below 0.8 DOTAP/oligonucleotide complexes induced leaking from negatively charged DPPC/DPPG liposomes. These results indicate that either phosphatidylethanolamine or negative charge are required in the cell membrane for fusion of cationic liposome-oligonucleotide complexes. The ratio of oligonucleotide to cationic lipid is critical in determining the physicochemical properties of the mixture.

A lipid carrier with a membrane active component and a small complex size are required for efficient cellular delivery of anti-sense phosphorothioate oligonucleotides.

Anti-sense oligonucleotides are potential therapeutic agents that are used to block protein expression from mRNA. To assess the essential properties for an efficient cellular delivery system of phosphorothioate oligonucleotides (PS-ODNs), different cationic carriers were compared. The carriers were complexed with oligonucleotides at various +/- charge ratios in MES-Hepes buffer. Cationic polymers, polylysines (PLL, mean MWs 4000, 20000, 200000 kDa), polyethyleneimines (PEI, mean MWs 25 and 800 kDa) and fractured sixth-generation polyamidoamine dendrimer (PAMAM) were tested for ODN delivery into a D 407 cell line (human retinal pigment epithelial cells) with stably transfected luciferase gene. Anti-sense ODN was directed against the luciferase gene, and the anti-sense effect was determined using a luminometric method. Lipid-based vehicles included DOTAP, DOTAP/DOPE (1/1 by mol), DOTAP/Chol (1/1 by mol), DOTAP/DOPE/Chol (2/1/1 by mol), DOGS and Cytofectin GS/DOPE (2/1 by mol). Additionally a membrane-active peptide JTS-1 (NH(2) -GLFEALLELLESLWELLLEA-COOH) was added to the complexes containing DOTAP, PEI or PLL. In D 407 and CV-1 cells, the anti-sense effect was seen only with lipid-based carriers with a membrane-active component (DOPE or JTS-1). The polymeric systems were ineffective. The effect of the complexation medium was further studied on CV-1 cells. Complexes were prepared in either water, MES-Hepes buffer or cell growth medium (DMEM). Complexes prepared in water were generally most effective and the greater activity is probably due to the smaller complex size. Complex sizes differed greatly in buffer and DMEM, especially in the case of DOPE containing complexes. In conclusion, lipid carrier with a membrane active component and small complex size are required for an efficient cellular delivery of phosphorothioate oligonucleotides.

Intracellular Distribution of Oligonucleotides Delivered by Cationic Liposomes: Light and Electron Microscopic Study1

Synthesized oligonucleotides are used in anti-sense and anti-gene technology to control gene expression. Because cells do not easily take up oligonucleotides, cationic liposomes have been employed to facilitate their transport into cells. Athough cationic liposomes have been used in this way for several years, the precise mechanisms of the delivery of oligonucleotides into cells are not known. Because no earlier reports have been published on the liposomal delivery of oligonucleotides at the ultrastructural level, we performed a study, using electron microscopy, on the cellular uptake and intracellular distribution of liposomal digoxigenin-labeled oligodeoxynucleotides (ODNs) at several concentrations (0.1, 0.2, and 1.0 μM) in CaSki cells. Two cationic lipids (10 μM) were compared for transport efficiency: polycationic 2,3-dioleoyloxy-N-[2(sperminecarboxamido)ethyl]-N,N-dimethyl-1-propanaminium trifluoroacetate (DOSPA) and monocationic dimethyl-dioctadecylammonium bromide (DDAB). Both liposomes contained dioleoyl-phosphatidylethanolamine (DOPE) as a helper lipid. Endocytosis was found to be the main pathway of cellular uptake of liposomal ODNs. After release from intracellular vesicles, ODNs were carried into the perinuclear area. The nuclear membrane was found to be a barrier against the penetration of ODNs delivered by liposomes into the nucleus. Release from vesicles and transport into the nuclear area was faster when the oligo-DDAB/DOPE complex had a positive net charge (0.1 and 0.2 μM ODN concentrations), and only under this condition were some ODNs found in nucleoplasm. Although DOSPA/DOPE could also efficiently deliver ODNs into the cytosol, no ODNs were found in nucleoplasm. These findings suggest that both the type of liposome and the charge of the oligo-liposome complex are important for determination of the intracellular distribution of ODNs.

A novel drug-regulated gene expression system based on the nuclear receptor constitutive androstane receptor (CAR).

AbstractPurpose. To develop and characterize a new drug-regulated gene expression system based on the nuclear receptor constitutive androstane receptor (CAR). Methods. Both transient and stable transfection into HEK293 cells of luciferase plasmids under the control of either drug- and steroid-responsive nuclear receptor CAR or the tetracycline-sensitive transactivator tTA were used in development of stable cell lines. Results. A stable first-generation cell line that expresses luciferase gene under the control of nuclear receptor CAR was developed. The luciferase expression in CAR-producing cells could be suppressed by androstanes and reactivated by structurally unrelated drugs chlorpromazine, metyrapone, phenobarbital, and clotrimazole. The kinetics of luciferase expression in CAR-producing cells and the tTA system were comparable. The overall regulation of CAR system was improved by modifications to the DNA binding domain and site. Conclusions. Because of its wide ligand selectivity and transferable ligand binding domain, CAR expands the repertoire of regulated gene expression systems.

Physicochemical and morphological properties of complexes made of cationic liposomes and oligonucleotides

Abstract Cationic liposomes are a potential delivery system for antisense oligonucleotides, but physical chemistry of this system is still poorly understood. We studied physicochemical properties (size distribution, lipid mixing reactions) and the morphology of oligonucleotide–cationic lipid complexes in buffer and in cell culture medium using quasi-elastic light scattering (QELS), resonance energy transfer (RET) and freeze-fracture electron microscopy. In addition, interaction of the complexes with model membranes was studied at extracellular (pH 7.4), intracellular (pH 7.1) and endosomal (pH 5 and 6) conditions. Phosphorothioate oligonucleotides (ODN, 15 mer) were complexed with cationic liposomes composed of DOTAP, or DOTAP with DOPE at 1/1 and 1/2 molar ratios and investigated at different charge ratios (−/+, ODN–cationic lipid). The size of the complexes formed in water increased prominently in buffer and DMEM and it was maximal at charge ratio (−/+) of 1.2–1.5. In the case of sole DOTAP liposomes the complex sizes were smaller at −/+ ratios 1.7 in all media. In the presence of DMEM the DOPE-containing complexes gave average diameter in μm range irrespect of the charge ratio. Lipid mixing, in general, increased with increasing −/+ ratio and with DOPE in the presence of buffer or DMEM. Freeze-fracture electron micrographs showed cationic liposomes undergoing aggregation and fusion during interaction with ODNs. DOPE in cationic liposomes induced hexagonal lipid tubule formation that was most pronounced in cell culture medium. Upon incubation with endosomal model liposomes ODN was partly released from the complexes. The release was more pronounced when the liposomes contained DOPE. It appears that DOPE as a helper lipid affects the behaviour of ODN/lipid complexes at several stages.

Cell Membranes As Barriers for The Use of Antisense Therapeutic Agents

Antisense oligonucleotides are promising therapeutical agents for numerous diseases resulting from overexpression of genes, expression of mutant genes and viral infections. As most oligonucleotides are polyanions they can not readily pass cellular membranes in adequate amounts to show activity. Therefore, different types of carrier systems and modifications have been developed to enhance absorption and distribution at the level of tissues and cells. The current state of delivery systems will be reviewed with a major part devoted to the commonly used cationic lipids.

Liquid chromatography determination of liposome components using a light-scattering evaporative detector

Analysis of liposomal components is important in stability testing of formulations. An LC method for the analysis of liposomal components cholesterol, phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine and their lyso-forms was developed. The method uses a light-scattering evaporative detector and isocratic mobile phase. In addition, components of pH-sensitive liposomes, cholesterylhemisuccinate and cationic lipid dimethyldioctadecylammonium bromide used in transfections were determined by the method. The separations were carried out on a Spherisorb S5 NH2 cartridge column or Zorbax NH2 column (25 cm x 4.6 mm, 5 microns particle size). The mobile phase consisted of acetonitrile-methanol-ammonium acetate solution (pH 4.8, 0.1 M) (52:32:16, v/v/v) at a flow rate of 2 ml min-1. Detection limits were 1.3-8.0 micrograms ml-1 depending on the lipid. The precision (RSD) of the method was 1.5-3.3% for lipid standard solutions at 50 micrograms ml-1 concentration and 2.0-11.8% for lipids analyzed from liposome suspensions.

The stability and dissolution properties of solid glucagon/γ-cyclodextrin powder

In the present study, the solid-state stability and the dissolution of glucagon/gamma-cyclodextrin and glucagon/lactose powders were evaluated. Freeze-dried powders were stored at an increased temperature and/or humidity for up to 39 weeks. Pre-weighed samples were withdrawn at pre-determined intervals and analyzed with HPLC-UV (HPLC=high performance liquid chromatography, UV=ultraviolet), HPLC-ESI-MS (ESI-MS=electrospray ionization mass spectrometry), SEC (size-exclusion chromatography), turbidity measurements and solid-state FTIR (Fourier Transform Infrared Spectroscopy). Dissolution of glucagon was evaluated at pH 2.5, 5.0 and 7.0. In addition, before storage, proton rotating-frame relaxation experiments of solid glucagon/gamma-cyclodextrin powder were conducted with CPMAS ((13)C cross-polarization magic-angle spinning) NMR (nuclear magnetic resonance) spectroscopy. In the solid state, glucagon was degraded via oxidation and aggregation and in the presence of lactose via the Maillard reaction. The solid-state stability of glucagon/gamma-cyclodextrin powder was better than that of glucagon/lactose powder. In addition, gamma-cyclodextrin improved the dissolution of glucagon at pH 5.0 and 7.0 and delayed the aggregation of glucagon after its dissolution at pH 2.5, 5.0 and 7.0. There was no marked difference between the proton rotating-frame relaxation times of pure glucagon and gamma-cyclodextrin, and thus, the presence of inclusion complexes in the solid state could not be ascertained by CPMAS NMR. In conclusion, when compared to glucagon/lactose powder, glucagon/gamma-cyclodextrin powder exhibited better solid-state stability and more favorable dissolution properties.