Effects of low doses of essential oils on the antioxidant status of the erythrocytes, liver and the brain of mice

We studied the effects of essential oils from oregano and clove and a mixture of lemon essential oil and a ginger extract on the antioxidant state of organs in intact and three experimental groups of Balb/c mice. We found that in vivo essential oils were efficient bioantioxidants when mice were treated with it for 6 months even at very low doses, such as 300 ng/day. All studied essential oils inhibited lipid peroxidation (LPO) in the membranes of erythrocytes that resulted in increasing membrane resistance to spontaneous hemolysis, decreasing membrane microviscosity, maintenance of their integrity, and functional activity. The essential oil significantly decreased the LPO intensity in the liver and the brain of mice and increased the resistance of liver and brain lipids to oxidation and the activity of antioxidant enzymes in the liver. The most expressed bioantioxidant effect on erythrocytes was observed after clove oil treatment, whereas on the liver and brain, after treatment with a mixture of lemon essential oil and a ginger extract.     

The Structural State and Form of Free and Biopolymer-Encapsulated Phosphatidylcholine Liposomes in the Absence and Presence of Natural Plant Antioxidants

Electron spin resonance (ESR) and atomic force microscopy (AFM) were used to study liposomes that were prepared from soybean phosphatidylcholine (PC); they incorporated plant antioxidants (ginger, allspice, and black-pepper extracts; clove oil; etc.) that were encapsulated in biopolymers (sodium caseinate or sodium caseinate–maltodextrin covalent conjugates). Plant antioxidants were shown to cause a 15–25% decrease in the microviscosity of deep-lying regions of the liposome lipid bilayer by ESR with a 16-doxylstearic acid spin probe. A ginger extract exerted the greatest effect (24%). Sodium caseinate and its covalent conjugates with maltodextrins (dextrose equivalents (DEs) 2 and 10) increased the microviscosity by 30–35% as compared with free and antioxidant-incorporating liposomes. AFM showed that antioxidants increased the cross-sectional area and volume of liposomes and that the polymers made liposomes denser and their structure more compact.     

Effect of Macrophage Elimination Using Liposome-Encapsulated Dichloromethylene Diphosphonate on Tissue Distribution of Liposomes

Abstract

Effect of macrophage elimination using liposomal dichloromethylene diphosphonate (C1₂MDP)1 on tissue distribution of different types of liposomes was examined in mice. Intravenously administration into mice with CI2MDP encapsulated in liposomes composed of phosphatidylcholine, cholesterol and phosphatidylserine exhibits a temporary blockade of liver and spleen function for liposome uptake. At a low dose of 90 (ig/mouse, the liposome uptake by the liver was significantly decreased. Such decrease was accompanied by an increase in liposome accumulation in either spleen or blood depending on liposome composition and size. Direct correlation between the administration dose of liposomal CI2MDP and the liposome circulation time in blood was also obtained even for liposomes with an average diameter of more than 500 nm. These results indicate that temporary elimination of macrophages of the liver and spleen using liposomal CI2MDP may prove to be useful to enhance the drug delivery efficiency of liposomes.     

Biochemical aspects of the visual process XXXII. Movement of sodium ions through bilayers composed of retinal and rod outer segment lipids

The leakage of Na⁺ from sonicated liposomes, composed of rod outer segment lipids, retinal lipids and a 4 : 1 phosphatidylcholine/phosphatidylserine mixture, has been studied. Both retinal and rod outer segment lipid liposomes lose Na⁺ faster than Ca²⁺ which indicates that the observed leakage occurs from closed liposomal structures.Liposomes from rod outer segment lipids are extremely leaky, losing sodium about 10 times as fast as retinal lipid liposomes and twice as fast as the phosphatidylcholine/phosphatidylserine liposomes.This high permeability of rod outer segment lipid liposomes, as compared to retinal lipid liposomes, is probably due to both the higher degree of unsaturation of the fatty acid chains and their lower cholesterol content. In the rod outer segment lipid extract 48% of the fatty acid chains consists of docosahexaenoic acid (C_22:6) against only 24% in retinal lipid extract. Rod outer segment lipids contain 4.0% cholesterol against 12.3% in retinal lipids.The sodium leakage from rod outer segment lipid liposomes is little affected by the presence of 5 mM calcium in the external dialysis medium, but with the two other types of liposomes significant decreases in permeability of about 20% are observed.The results are discussed in connection with the role of cations in visual excitation.     

Conjugation of lipid and CpG-containing oligonucleotide yields an efficient method for liposome incorporation

For optimal stimulation of T cells, protein-based vaccines must deliver protein antigens to antigen-presenting cells while simultaneously providing immunostimulatory signals. Listeriolysin O (LLO)-containing liposomes have been utilized to efficiently deliver protein antigens to the cytosolic pathway for antigen processing and major histocompatibility complex class I-dependent presentation while codelivering immunostimulatory CpG-oligodeoxyribonuceotides (ODNs). In this report, we describe the synthesis of lipid-CpG-ODN conjugates utilizing maleimide-phosphatidylethanolamine (PE) lipids and 5'-sulfhdryl-containing CpG-ODNs as a method for facile incorporation of CpG-ODNs in liposomal vaccine carriers, an alternative to co-encapsulation inside liposomes and as a means to enhance delivery of CpG-ODNs to their major receptor, Toll-like receptor 9 (TLR9), in the endosome. The characterization and biological evaluation of the vaccine delivery system made of liposomes, which contain the lipid-CpG-ODN conjugates inserted in the liposomal membrane, is described. We demonstrate in vitro in bone marrow derived macrophages that the lipid-CpG-ODN conjugates incorporated onto the liposome bilayers interact with their receptor TLR9 as readily as liposome-encapsulated ODNs and exert their immunostimulatory capabilities. The liposomal vaccine delivery systems were evaluated in mice using ovalbumin (OVA) as a model antigen, and the results indicate equally robust OVA-specific cytotoxic T lymphocyte responses and similar Th1 immune skewing capabilities between liposomes containing lipid-conjugated or encapsulated CpG-ODNs. Overall, this work indicates that conjugating PE lipids and CpG-ODNs results in an efficient method that allows facile incorporation of CpG-ODNs into a liposome-based delivery platform while retaining the immune-stimulating capabilities of CpG-ODNs.     

Liposomal Drug with Carnosine and Lipoic Acid: Preparation,Antioxidant and Antiplatelet Properties

The conditions for producing phosphatidylcholine liposomes containing lipoic acid and carnosine together were determined. The obtained liposomes are 180–250-nm spherical particles with an efficiency of lipoic acid inclusion of 50–70% (for carnosine, 17–33%). Based on the model of the oxidation of phosphatidylcholine by hydrogen peroxide, an antioxidant effect of carnosine, lipoic acid or lipoic acid with carnosine together was demonstrated; it consisted in inhibition of lipid peroxidation process, which was manifested in a decrease in the formation of lipid peroxidation products that react with thiobarbituric acid. It was established that lipoic acid (5 mM) and carnosine (0.1–10 mM) in liposomes exhibit an antioxidant effect. At the same time, it was demonstrated that the content of the appropriate lipid peroxidation products in liposomes with antioxidants (lipoic acid + carnosine) was 15 times lower than in control liposomes (without antioxidants). The effect of the obtained liposomal drugs on the platelet aggregation induced by arachidonic acid was evaluated. It was found that the liposomal drug containing lipoic acid (1.5 mM) and carnosine (2.1 mM) inhibited platelet aggregation by 50–55% relative to the control (platelets and arachidonic acid), while liposomes without antioxidants and water-soluble forms of carnosine and lipoic acid had almost no effect on platelet aggregation caused by arachidonic acid.

     

Cytosolic delivery of macromolecules. II. Mechanistic studies with pH-sensitive morpholine lipids

Drug carriers containing weak acids or bases can promote cytosolic delivery of macromolecules by exploiting the acidic pH of the endosome. We have prepared two pH-sensitive mono-stearoyl derivatives of morpholine, one with a (2-hydroxy) propylene (ML1) linker and the other, an ethylene (ML2) linker. The pK(a) values of lipids ML1 and ML2, when incorporated into liposomes, are 6.12 and 5.91, respectively. Both lipids disrupt human erythrocytes at pH equal to or below their pK(a) but show no such activity at pH 7.4. Confocal microscopy studies suggest partial endosome-to-cytosol transfer of fluorescent dextran (MW 10 kDa) encapsulated in liposomes that contained 20 mol% of morpholine lipids. Interestingly, co-incubation of morpholine lipids in free or micellar form (without liposomal incorporation) with dextran resulted in efficient cytosolic delivery. Upon acidification to the endosomal pH, liposomes containing ML1 revealed: (a). leakage of entrapped solute that is independent of solute size; (b). lack of liposomal collapse into micelles as evidenced by photon correlation spectroscopy and UV light scattering; and (c). minimal inter-bilayer interactions as shown in a fluorescence resonance energy transfer assay. These observations are consistent with progressive intravesicular reorganization of lipids into stable liposomes of smaller size, but of more homogeneous distribution, upon acidification. The results emphasize a need to manipulate liposomal formulations containing ML1 such that ML1 will promote catastrophic collapse of liposomes to mixed micelles upon exposure to acidic pH. It is only then that micelle-mediated permeabilization of the endosomal membrane will lead to efficient cytosolic delivery of macromolecules originally loaded in liposomes.     

LIPOSOMES CONTAINING DOPAMINE ENTRAPPED IN RESPONSE TO TRANSMEMBRANE AMMONIUM SULFATE GRADIENT AS CARRIER SYSTEM FOR DOPAMINE DELIVERY INTO THE BRAIN OF PARKINSONIAN MICE

The active loading of liposomes with dopamine in response to an ammonium sulfate gradient was studied. This method can be regarded as a mean to more efficiently improve the liposomal dopamine/lipids ratio in comparison to conventional methods of liposome preparation. Trapping efficiency of dopamine into liposomes exhibiting a transmembrane ammonium sulfate gradient was shown to be dependent on liposome lipid composition, lipid concentration and temperature. Dopamine-containing liposomes with α-tocopherol in the lipid bilayer were shown to be stable at least for three weeks. It has been found that intraperitoneal (i.p.) administration of conventionally prepared dopamine-containing liposomes as well as liposomes with increased dopamine/lipid ratio may efficiently suppress the expression of parkinsonian symptoms in C57BL/6 mice with experimental parkinsonian syndrome. On the other hand, only through increasing of liposomal dopamine/lipid ratio the complete compensation of dopamine deficiency in the mice brain was achieved. The obtained data may be considered as biochemical evidence in favor of liposomes' ability to act as a carrier system for the delivery of dopamine into the brain.     

Tissue distribution of EDTA encapsulated within liposomes of varying surface properties

Liposomes containing ethylenediaminetetraacetic acid (EDTA) were prepared with different surface properties by varying the liposomal lipid constituents. Positively charged liposomes were prepared with a mixture of phosphatidylcholine, cholesterol, and stearylamine. Negatively charged liposomes were prepared with a mixture of phosphatidylcholine, cholesterol, and phosphatidylserine. Neutral liposomes were prepared with phosphatidylcholine alone, dipalmitoyl phosphatidylcholine alone, or with a mixture of phosphatidylcholine and cholesterol. Distributions of ¹⁴C-labeled EDTA were determined in mouse tissues from 5 min to 24 h after a single intravenous injection of liposome preparation. Differences in tissue distribution were produced by the different liposomal lipid compositions. Uptake of EDTA by spleen and marrow was highest from negatively charged liposomes. Uptake of EDTA by lungs was highest from positively charged liposomes; lungs and brain retained relatively high levels of EDTA from these liposomes between 1 and 6 h after injection. Liver uptake of EDTA from positively or negatively charged liposomes was similar; the highest EDTA uptake by liver was from the neutral liposomes composed of a mixture of phosphatidylcholine and cholesterol. Liposomes composed of dipalmitoyl phosphatidylcholine produced the lowest liposomal EDTA uptake observed in liver and marrow but modrate uptake by lungs. Tissue uptake and retention of EDTA from all of the liposome preparations were greater than those of non-encapsulated EDTA. The results presented demonstrate that the tissue distribution of a molecule can be modified by encapsulation of that substance into liposomes of different surface properties. Selective delivery of liposome-encapsulated drugs to specific tissues could be effectively used in chemotherapy and membrane biochemistry.     

Interaction of alpha-tocopherol with iron: antioxidant and prooxidant effects of alpha-tocopherol in the oxidation of lipids in aqueous dispersions in the presence of iron

The dual functions of alpha-tocopherol in the oxidation of lipids in aqueous dispersions in the presence of iron were studied, aiming specifically at elucidating the effect of interaction between alpha-tocopherol and iron. Ferrous ion decomposed hydroperoxide rapidly and induced the free radical chain oxidation of soybean phosphatidylcholine liposomes. alpha-Tocopherol acted primarily as a radical scavenger in the oxidation induced by ferrous ion and acted as an antioxidant. Ferric ion decomposed hydroperoxide much more slowly than ferrous ion, but it also induced the oxidation of liposomal membranes. alpha-Tocopherol incorporated into artificial liposomal membranes reduced ferric ion rapidly to give more reactive ferrous ion, and alpha-tocopherol acted either as an antioxidant or as a prooxidant depending on the experimental conditions. When alpha-tocopherol was depleted by the interaction with ferric ion, it acted solely as a prooxidant, whereas if some alpha-tocopherol remained, it acted as an antioxidant. On the other hand, alpha-tocopherol residing in the intact erythrocyte membranes did not reduce ferric ion in the aqueous region.     

THE ROLE OF LIPIDS IN THE OBSERVED LACK OF PHOSPHATIDYLCHOLINE EXCHANGE IN MYELIN

Abstract— When exchange between liposomal phosphatidylcholine and that in a whole myelin fraction from guinea-pig brain was studied, very little exchange was observed. In order to investigate the reason for this phenomenon, myelin lipids in the Ca²⁺ form were prepared and subjected to sonication under the same conditions usually used to study phosphatidylcholine exchange. Despite the high cholesterol content in these extracts, this treatment produced liposomes of a size (12 nm Stoke's radius) similar to that of pure phosphatidylcholine liposomes. In this form, myelin total lipids were capable of undergoing exchange, and this was only demonstrable in the fraction containing phosphatidylcholine and that containing phosphatidylinositol. Since the level of acidic phospholipids in these total lipid extracts is potentially capable of producing 40% inhibition of phosphatidylcholine exchange (H ellings et al , 1974; B rammer & S heltawy , 1975), control experiments were carried out to ensure that the observed phosphatidylcholine exchange in the myelin lipid extract was not due to the loss of phosphoinositides. This was found to be the case, and it was concluded therefore that total myelin lipids, in the Ca²⁺ form, are capable of phosphatidylcholine exchange and that the observed lack of it in the whole myelin is due either to the effect of myelin proteins or the compact structure of the myelin membrane.
Calculations based on the difference between the rate of phosphatidylcholine exchange in the myelin liposomes and in the sonicated phosphatidylcholine liposomes indicated that the phosphatidylcholine is asymmetrically distributed in the myelin liposomes. Almost all the phosphatidylcholine seems to be present in the outer half of the bilayer.     

The involvement of the lipid phase transition in the plasma-induced dissolution of multilamellar phosphatidylcholine vesicles

Unsonicated liposomes prepared from dimyristoyl phosphatidylcholine were nearly completely dissolved during a 3 h incubation with rat plasma at or close to the phase-transition temperature of 24°C. At 37 or 15°C virtually no liposomal disintegration was observed even after 24 h of incubation. The liposomal solubilization, which was monitored by turbidity measurements or by determination of phospholipid sedimentability, was accompanied by the formation of a phospholipid-protein complex similar or identical to the one we previously reported to be formed from sonicated liposomes of egg phosphatidylcholine (Scherphof, G., Roerdink, F., Waite, M. and Parks, J. (1978) Biochim. Biophys. Acta 542, 296–307). Unsonicated multilamellar liposomes made of egg phosphatidylcholine were completely resistant to the dissolving potency of plasma when incubated at 37°C. Liposomes from equimolar mixtures of dimyristoyl and dipalmitoyl phosphatidylcholine were only degraded by plasma in the temperature range between 30 and 35°C at which temperature this cocrystallizing phospholipid mixture undergoes a phase transition. However, even at these temperatures the rate of dissolution of this mixture was significantly lower than of dimyristoyl phosphatidylcholine at 24°C. In the dissolving process of this mixture a slight preference for the lower-melting component was observed.The ability of cholesterol to completely abolish the susceptibility of dimyristoyl phosphatidylcholine liposomes to plasma at a 1:2 molar ratio of cholesterol to phospholipid substantiates the essential role of the phase transition in the process of liposome solubilization.When liposomes of the monotectic mixtures dimyristoyl and distearoyl phosphatidylcholine or dilauroyl and distearoyl phosphatidylcholine were incubated with plasma at temperatures in between those at which the constituent lipids undergo a phase change in the mixture, the liposomes were slowly disolved. Under those conditions a selective removal of the lipids in the liquid-crystalline phase was observed.It is concluded that for the plasma-induced dissolution of unsonicated liposomes, which is most probably achieved by interaction with (apo)lipoproteins, the presence of phase boundaries is required in much the same way as was first reported for phospholipases by Op den Kamp, J.A.F., de Gier, J. and Van Deenen, L.L.M. (1974) Biochim. Biophys. Acta 345, 253–256).     

Simultaneous Determination of Polyethylene Glycol-Conjugated Liposome Components by Using Reversed-Phase High-Performance Liquid Chromatography with UV and Evaporative Light Scattering Detection

Liposomes incorporating polyethylene glycol (PEG)-conjugated lipids (PEGylated liposomes) have attracted attention as drug delivery carriers because they show good in vivo stability. The lipid component of PEGylated liposomal formulations needs to be quantified for quality control. In this study, a simple reversed-phase high-performance liquid chromatography (HPLC) method with an evaporative light-scattering detector (ELSD) was established for simultaneous determination of hydrogenated soy phosphatidylcholine, cholesterol, PEG-conjugated lipid, and hydrolysis products of phospholipid in PEGylated liposomal formulations. These lipids were separated using a C18 column with a gradient mobile phase consisting of ammonium acetate buffer and ammonium acetate in methanol at a flow rate of 1.0 ml/min. This method provided sufficient repeatability, linearity, and recovery rate for all lipids. However, the linearity and recovery rates of cholesterol achieved using a ultraviolet (UV) detector were better than those achieved using an ELSD. This validated method can be applied to assess the composition change during the preparation process of liposomes and to quantify lipid components and hydrolysis products contained in a commercially available liposomal formulation DOXIL®. Taken together, this reversed-phase HPLC-UV/ELSD method may be useful for the rapid or routine analysis of liposomal lipid components in process development and quality control.     

Complement-dependent phagocytosis of liposomes by macrophages: suppressive effects of "stealth" lipids

We have previously reported that complement-opsonized liposomes composed of dimyristoyl phosphatidylcholine and cholesterol are actively phagocytozed by murine peritoneal macrophages and that such complement-induced phagocytosis can be suppressed by the presence of liposomal phosphatidylinositol (Proc. Natl. Acad. Sci. USA 81, 1984). We now report suppressive effects of other liposomal lipids, including monosialoganglioside (GM1) and sulfogalactosylceramide. Complement-dependent phagocytosis was almost completely suppressed by liposomes containing GM1 or phosphatidylinositol and partially suppressed when liposomes contained sulfogalactosylceramide. Although the mechanism of suppression of complement-induced phagocytosis by these liposomal lipids is not yet completely understood, it does not seem to involve the early stages of complement activation resulting in opsonization of liposomes with complement. We conclude that suppression of complement-induced phagocytosis by phosphatidylinositol, GM1, or sulfogalactosylceramide occurs at a step after liposome opsonization.     

Cationic lipid-mediated nucleic acid delivery: beyond being cationic

Realization of the potential of nucleic acids as drugs is intricately linked to their in vivo delivery. Cationic lipids demonstrated tremendous potential as safe, efficient and scalable in vitro carriers of nucleic acids. For in vivo delivery of nucleic acids, the extant two component liposomal preparations consisting of cationic lipids and nucleic acids have been largely found to be insufficient. Being a soft matter, liposomes readily respond to many physiological variables leading to complex component and morphological changes, thus confounding the efforts in a priori identification of a “competent” formulation. In the recent past many chemical moieties that provide advantage in facing the challenges of barriers in vivo, were incorporated into cationic lipids to improve the transfection efficiency. The cationic lipids, essential for DNA condensation and protection, definitely require additional components to be efficient in vivo. In addition, formulations of cationic lipid carriers with non-lipidic components, mainly peptides, have demonstrated success in in vivo transfection. The present review describes some recent successes of in vivo nucleic acid delivery by cationic lipids.     

Effect of the antioxidant phenozan and neuropeptide adrenocorticotropic hormone on the structure of the liquid crystalline state of the lipid bilayer and thickness of the phosphatidylcholine membrane

By the methods of NMR, PMR and EPR spectrometry and X-ray diffaction, the occurrence of polymorphic liquid-crystalline transformations in phosphatidylcholine liposomes from the bovine brain and the influence of phenozan (sterically screened phenol antioxidant) and adrenocorticotropic hormone were shown in the temperature range 25-55 degrees C. Phenozan and the adrenocortcotropic hormone, which have a nootropic activity in vivo, change the phase transition temperatures, promote polymorphic transformations in lipids and increase the disordering of lipid bilayer and the thickness of phosphatidylcholine membranes. We assume that the lipid polymorphysm is a step of information recording and keeping processes in synapse membranes.     

Osmotic Dehydration of Liposomal Dispersions: Influence of Particle Size and Electrostatic Deposition of Cold Water Fish Skin Gelatin

Liposomes are a promising delivery system for bioactives in food and nutraceuticals. Their practical application is limited by their physical and chemical instability caused by extrinsic factors. The physical stability of liposomes of three different sizes coated with cold water fish skin gelatin was assessed during osmotic dehydration at 2, 21 and 70 °C. Soy lecithin was used to prepare 1 % liposomal dispersions. The size distribution was controlled with high pressure homogenization (1500 bar) and extrusion through polycarbonate membrane (3 and 0.8 μm). Fish gelatin was adsorbed to the interface to make secondary liposomes. Liposomal dispersions were osmotically dehydrated while monitoring the relative weight, size and rheological properties. The primary liposomes had an initial mean volume diameter (d_4,3) of 0.09, 0.40 and 2.7 μm and a ζ-potential of ?55 mV. Secondary liposomes were 0.11, 0.45 and 3.4 μm with a ζ-potential of 25 mV. The size of liposomes influenced the stability of liposomes, with the smallest liposomes being stable for 30 min, corresponding to 80 % of the initial weight, while the larger liposomes were already aggregated. Secondary liposomes were stable to 120 min for the smaller liposomes and to 150 min for the largest liposomes corresponding to 40 % of the initial weight. Stability increased during dehydration at 2 °C. Coating the liposomes increased the physical stability of the liposomal dispersions at all temperatures. The results show that cold water fish skin gelatin is a viable option to coat liposomes of a wide size range.     

Interaction of liposomes bearing a lipophilic doxorubicin prodrug with tumor cells

When used as nanosized carriers, liposomes enable targeted delivery and decrease systemic toxicity of antitumor agents significantly. However, slow unloading of liposomes inside cells diminishes the treatment efficiency. The problem could be overcome by the adoption of lipophilic prodrugs tailored for incorporation into lipid bilayer of liposomes. We prepared liposomes of egg yolk phosphatidylcholine and yeast phosphatidylinositol bearing a diglyceride conjugate of an antitumor antibiotic doxorubicin (a lipophilic prodrug, DOX-DG) in the membrane to study how these formulations interact with tumor cells. We also prepared liposomes of rigid bilayer-forming lipids, such as a mixture of dipalmitoylphosphatidylcholine and cholesterol, bearing DOX in the inner water volume, both pegylated (with polyethylene glycol (PEG) chains exposed to water phase) and non-pegylated. Efficiency of binding of free and liposomal doxorubicin with tumor cells was evaluated in vitro using spectrofluorimetry of cell extracts and flow cytometry. Intracellular traffic of the formulations was investigated by confocal microscopy; co-localization of DOX fluorescence with organelle trackers was estimated. All liposomal formulations of DOX were shown to distribute to organelles retarding its transport to nucleus. Intracellular distribution of liposomal DOX depended on liposome structure and pegylation. We conclude that the most probable mechanism of the lipophilic prodrug penetration into a cell is liposome-mediated endosomal pathway.     

Liposome preparation by a reverse-phase evaporation method and freezing-thawing

A method for preparing liposomes containing Na3Ca-14C-DTPA by means of phase-reverse evaporation and freezing-thawing is described. Freezing-thawing is required for transformation of the system formed after phase-reverse evaporation at a lipid concentration of over 20-30 mg/ml to liposomal suspension. Liposomes thus obtained contain 10-14 microliters aqueous phase per mumol phosphatidylcholine, their diameter varies between 0.2 and 1.5 micron (the mean value 0.45-0.54 micron). Increasing the concentration of lipids, it is possible to include into liposomes up to 70-80% of 14C-DTPA in solution. The method is believed to be fit for preparing the liposomal forms of other drug hydrophilic compounds.     

Liposomal delivery systems for encapsulation of ferrous sulfate: Preparation and characterization

Liposomal delivery systems for water-soluble bioactives were prepared using the pro-liposome and the microfluidization technologies. Iron, an essential micronutrient as ferrous sulfate and ascorbic acid, as an antioxidant for iron were encapsulated in the liposomes. Liposomes prepared by the microfluidization technology using 6% (w/w) concentration of the lipid encapsulated with ferrous sulfate and ascorbic acid had particle size distributions around 150 to 200 nm, whereas liposomes from the pro-liposome technology resulted in particle sizes of about 5 microm. The encapsulation efficiency of ferrous sulfate was 58% for the liposomes prepared by the microfluidization using 6% (w/w) lipid and 7.5% of ferrous sulfate concentrations, and it was 11% for the liposomes from pro-liposome technology using 1.5% (w/v) lipid and 15% of ferrous-sulfate concentration. Both the liposomes exhibited similar levels of oxidative stability, demonstrating the feasibility of microfluidization-based liposomal delivery systems for large-scale food/nutraceutical applications.