Distearoylphosphatidylglycerol Research Articles

Development of Microbubbles for Theranostics and Its Application in Brain Targeted Drug Delivery

Theranostics, a new medical term that combines therapeutics and diagnostics is considered an ideal system for medical care. Ultrasound is considered one of the most reasonable energies for the development of theranostics. Additionally, microbubbles, which are ultrasound contrast agents, have received considerable attention for their effectiveness in diagnosis and therapy. Microbubbles are composed of an inner gas and an outer shell composed of proteins or phospholipids. Under ultrasound exposure, the oscillation or collapse of microbubbles is induced depending on the intensity of the ultrasound. These mechanical effects are important for imaging, drug delivery, and ablation therapies. Therefore, it is essential that microbubbles reach the targeted site and induce mechanical effects to achieve effective and efficient diagnosis and therapy. We have previously developed novel microbubbles with high stability by optimizing the outer shell composition. Recently, microbubbles containing distearoylphosphatidyl glycerol showed high stability and prolonged circulation in the blood. These novel microbubbles may be useful for diagnosis and therapy. The combination of microbubbles and ultrasound has received considerable attention for brain-targeted drug delivery applications. We examined whether microbubbles can be used for brain-targeted drug delivery and evaluated the effect of the encapsulated gas on drug delivery. Thus, novel microbubbles combined with ultrasound can deliver molecules to the brain. Microbubbles containing perfluoropropane or perfluorobutane could efficiently deliver molecules to the brain. The novel microbubbles have long-circulating properties in the blood and could deliver molecules to the brain. The combination of novel microbubbles and ultrasound would contribute to the development of efficient thranostic systems.

Method Development and Characterization of Liposomal Formulation of Isotretinoin

This study aims to develop a liposomal drug delivery system of isotretinoin, an acne drug-using spray drying, as a cost-effective and time-effective technique. The liposomal formulation was prepared by using spray drying; three different strategies were adopted: suspension spray drying (SSD), thin-film hydration and spray drying (TFHSD), and emulsion spray drying (ESD). Isotretinoin was 99% bound with lipid, so lipids hydrogenated soy phosphatidylcholine (HSPC), distearoyl phosphatidylglycerol (DSPG), and cholesterol were selected for the formulation development. The HSPC, DSPG, cholesterol, and isotretinoin were taken in the ratio 4 : 1 : 0.16 : 3.1 mmol. In vitro drug release studies, microscopy, drug content, and related substance characterizations were done to formulate each strategy of spray drying prepared dry liposomes of isotretinoin. Results were compared with the USP monograph of isotretinoin. It was revealed that isotretinoin's liposomal formulation using ESD was having drug release according to the USP limits. Drug content was also according to the USP requirement; no free drug crystals were found in microscopy, multivesicular vesicles were found in shape, a particle size of up 60 µ was found. The ESD technique was a successful, time-effective, and cost-effective technique for preparing a liposomal drug delivery system for isotretinoin.

Negatively charged liposomes of sertraline hydrochloride: Formulation, characterization and pharmacokinetic studies

The present study was carried out with an objective to study the extent of delivery of negatively charged liposomes of sertraline hydrochloride to brain via intravenous route for treatment of depressive –like symptoms. Liposomes of sertraline hydrochloride were formulated by film hydration technique using cholesterol, hydrogenated soya phosphatidylcholine-l-α-phosphatidylcholine, and distearoyl phosphatidyl glycerol sodium. Uniform sized vesicles with porous surface morphology with vesicle size of 151.59 nm were prepared. Radioactive imaging performed using 99mTcO4 showed ~5% of uptake of labelled liposomes in brain within 2 h of administration. On administration of liposomes and free drug suspension, approximately, 205.06 ng/ml and 87.18 ng/ml of sertraline were estimated in brain at 36 h. The liposomes can be transported by transcelluar transport which includes phagocytosis and the use of phosphatidylcholine enhances macrophage internalization and delivery to brain. The study indicated significantly higher concentration of sertraline in brain after 36 h, on administration of liposomes as compared to free sertraline suspension.

Preparation, Statistical Optimization and In-vitro Characterization of a Dry Powder Inhaler (DPI) Containing Solid Lipid Nanoparticles Encapsulating Amphotericin B: Ion Paired Complexes with Distearoyl Phosphatidylglycerol.

The aim of this study was to prepare dry powder inhalers (DPIs) containing amphotericin B-loaded solid lipid nanoparticles (AMB-SLNs) as an alternative approach for prevention of pulmonary aspergillosis. For solubilizing AMB in small amounts of organic solvents ion paired complexes were firstly formed by establishing electrostatic interaction between AMB and distearoyl phosphatidylglycerol (DSPG). The SLN formulations containing AMB-DSPG complexes were prepared using glycerol monostearate (GMS) as the lipid matrix and soybean lecithin and tween 80 as the surfactants by solvent emulsification-evaporation technique. The nanoparticles were optimized through a fractional factorial design. DPIs were prepared by lyophilization technique using lactose as the inhalational carrier and then after, the formulations were evaluated in terms of aerodynamic particle size distribution using an Andersen cascade impactor. The morphology of the particles was examined using scanning electron microscopy (SEM) and in-vitro drug release profiles were evaluated. Following the statistical results, the particle size, Poly dispersity index (PdI), zeta potential, entrapment efficiency (EE%), and drug loading (DL%) of the optimized SLNs were 187.04 ± 11.97 nm, 0.188 ± 0.028, -30.16 ± 1.6 mV, 89.3 ± 3.47 % and 2.76 ± 0.32 %, respectively. Formulation containing 10% w/v of lactose with the calculated fine particle fraction value as 72.57 ± 4.33% exhibited the appropriate aerodynamic characteristics for pulmonary drug delivery. SEM images revealed de-agglomerated particles. In-vitro release studies showed sustained release of AMB from the carriers and the release kinetics were best fitted to the first order kinetic model.

The Role of Temperature and Lipid Charge on Intake/Uptake of Cationic Gold Nanoparticles into Lipid Bilayers.

Understanding the molecular mechanisms governing nanoparticle-membrane interactions is of prime importance for drug delivery and biomedical applications. Neutron reflectometry (NR) experiments are combined with atomistic and coarse-grained molecular dynamics (MD) simulations to study the interaction between cationic gold nanoparticles (AuNPs) and model lipid membranes composed of a mixture of zwitterionic di-stearoyl-phosphatidylcholine (DSPC) and anionic di-stearoyl-phosphatidylglycerol (DSPG). MD simulations show that the interaction between AuNPs and a pure DSPC lipid bilayer is modulated by a free energy barrier. This can be overcome by increasing temperature, which promotes an irreversible AuNP incorporation into the lipid bilayer. NR experiments confirm the encapsulation of the AuNPs within the lipid bilayer at temperatures around 55 °C. In contrast, the AuNP adsorption is weak and impaired by heating for a DSPC-DSPG (3:1) lipid bilayer. These results demonstrate that both the lipid charge and the temperature play pivotal roles in AuNP-membrane interactions. Furthermore, NR experiments indicate that the (negative) DSPG lipids are associated with lipid extraction upon AuNP adsorption, which is confirmed by coarse-grained MD simulations as a lipid-crawling effect driving further AuNP aggregation. Overall, the obtained detailed molecular view of the interaction mechanisms sheds light on AuNP incorporation and membrane destabilization.

Combination of cyclic voltammetry and single-particle Brownian dynamics methodology to evaluate the fluidity of phospholipid monolayers at polarized liquid/liquid interfaces

The present work shows, for the first time, the use of single-particle Brownian dynamics methodology, followed by optical microscopy, coupled with electrochemistry techniques to evaluate the fluidity of phospholipid films adsorbed at liquid/liquid interfaces. The combination of the two methods allows observing the movement of latex beads at the liquid/liquid interface modified by a phospholipid monolayer, with and without polarization by linear potential scans or potential steps. In this way, the effect of polarization on distearoylphosphatidylglycerol (DSPG), dimyristoylphosphatidylcholine (DMPC), and distearoylphosphatidylcholine (DSPC) monolayers, adsorbed at the water/1,2-dichloroethane interface, could be directly observed and diffusion coefficient values were derived. Lateral motilities of these particles can be correlated with the monolayer fluidity and solid character. A comparison with the behavior of the lipids at air/water interfaces is also included.

Anionic nanoliposomes reduced atherosclerosis progression in Low Density Lipoprotein Receptor (LDLR) deficient mice fed a high fat diet.

Atherosclerosis is a systemic disease characterized by the deposition of cholesterol and inflammatory cells within the arterial wall. Removal of cholesterol from the vessel wall may have an impact on the size and composition of atherosclerotic lesions. Anionic phospholipids or liposome vesicles composed of a lipid bilayer such as nanoliposomes have been suggested as treatments for dyslipidemia. In this study, we investigated the effect of anionic nanoliposomes on atherosclerosis in a mouse model. Low-density lipoprotein receptor knockout mice (Ldlr-/- ) were fed with an atherosclerosis promoting high fat and cholesterol (HFC) diet for 12 weeks. Anionic nanoliposomes including hydrogenated soy phosphatidylcholine (HSPC) and distearoyl phosphatidylglycerol (DSPG) (molar ratio: 1:3) were injected intravenously into HFC-fed Ldlr-/- mice once a week for 4 weeks. Mice receiving nanoliposomes had significantly reduced atherosclerosis within the aortic arch as assessed by Sudan IV staining area (p = 0.007), and reduced intima/media ratio (p = 0.030) and greater collagen deposition within atherosclerosis plaques within the brachiocephalic artery (p = 0.007), compared to control mice. Administration of nanoliposomes enhanced markers of reverse cholesterol transport (RCT) and increased markers of plaque stability in HFC-fed Ldlr-/- mice. Reduced cholesterol accumulation was observed in the liver along with the up-regulation of the major genes involved in the efflux of cholesterol such as hepatic ATP-binding cassette transporters (ABC) including Abc-a1, Abc-g1, Abc-g5, and Abc-g8, Scavenger receptor class B, member 1 (Scarb1), and Liver X receptor alpha (Lxr)-α. Lecithin Cholesterol Acyltransferase activity within the plasma was also increased in mice receiving nanoliposomes. Anionic nanoliposome administration reduced atherosclerosis in HFC-fed Ldlr-/- mice by promoting RCT and upregulating the ABC-A1/ABC-G1 pathway.

Development of separation technology for the removal of radium-223 from decayed thorium-227 in drug formulations. Material screening and method development

Targeted thorium conjugates are currently being investigated as a new class of alpha-radiopharmaceuticals. The natural decay of thorium-227 (227Th) results in the ingrowth of radium-223 (223Ra). Consideration must, therefore, be given to define acceptable limits of 223Ra in the drug product at the time of dose administration. By effective sequestration of 223Ra, we aim to improve the radiochemical purity and extend the effective user window of drug products containing 227Th. 223Ra is the first progeny of 227Th and the only one with a long half-life (days). We have, therefore, focused on the removal of this specific species since the progenies of 223Ra will have a very limited lifetime in the formulation once 223Ra is removed. In this study, we investigated a multitude of materials for their ability to reduce the 223Ra level by: (1) passive diffusion or (2) by cartridge filtration on gravity columns. In addition, we probe the compatibility of these materials in the presence of antibody trastuzumab to assess the level of protein binding and estimate the quenching of radiolysis by binding of radionuclides. A screening matrix of organic and inorganic materials was established, i.e. strontium and calcium alginate gel beads, distearoyl phosphatidylglycerol (DSPG) liposomes, ceramic hydroxyapatite, Zeolite UOP type 4A and cation exchange resins AG50W-X8 and SOURCE 30S. First, passive diffusional uptake of 223Ra by suspended materials present in the formulation was measured as a decrease in sample radioactivity after separation. Second, selected materials were packed on gravity columns in order to evaluate the efficiency of column separation versus diffusional adsorption. The retention of 223Ra and 227Th were characterized by measuring the radioactivity in the eluate and on the columns. Finally, the compatibility between trastuzumab, as a selected model antibody, and suspensions of the binding materials was analyzed during storage of the drug product in the presence of adsorbent. The formation of H2O2 was evaluated to measure the influence of radionuclide binding material on radiolysis in the formulation. All the materials bound 223Ra by passive diffusional uptake ranging from 31% to 95% with DSPG liposomes demonstrating superiority at 95% efficiency. All materials suitable for assessment by gravity column filtration bound 223Ra almost quantitatively (∼100%) and with minimal variation (relative standard deviation <1%). The uptake was significantly higher compared to passive diffusional uptake. Alginate gel beads, ceramic hydroxyapatite and SOURCE 30S reduced the antibody concentration in solution to 40–50% while the Zeolite UOP type 4A, AG50W-X8 resin and DSPG liposomes showed ≤10% reduction of antibody concentration. Ceramic hydroxyapatite significantly reduced H2O2 formed by radionuclide initiated radiolysis.

Evaluation of the potential of doxorubicin loaded microbubbles as a theranostic modality using a murine tumor model

In this study, a novel phospholipid-based microbubble formulation containing doxorubicin and perfluoropropane gas (DLMB) was developed. The DLMBs were prepared by mechanical agitation of a phospholipid dispersion in the presence of perfluoropropane (PFP) gas. An anionic phospholipid, distearoyl phosphatidylglycerol (DSPG) was selected to load doxorubicin in the microbubbles by means of electrostatic interaction. The particle size, zeta potential, echogenicity and stability of the DLMBs were measured. Drug loading was ⩾92%. The potential of the DLMBs for use as a theranostic modality was evaluated in tumor bearing mice. Gas chromatography analysis of PFP showed significant enhancement of PFP retention when doxorubicin was used at concentrations of 10–82% equivalent to DSPG. The inhibitory effects on the proliferation of B16BL6 melanoma murine cells in vitro were enhanced using a combination of ultrasound (US) irradiation and DLMBs. Moreover, in vivo DLMBs in combination with (US) irradiation significantly inhibited the growth of B16BL6 melanoma tumor in mice. Additionally, US echo imaging showed high contrast enhancement of the DLMBs in the tumor vasculature. These results suggest that DLMBs could serve as US triggered carriers of doxorubicin as well as tumor imaging agents in cancer therapy.

Apolipoprotein B-100-targeted negatively charged nanoliposomes for the treatment of dyslipidemia

BackgroundAnionic nanoliposomes can interact with serum lipoproteins and regulate lipid metabolism through several mechanisms. This study aimed to evaluate the lipid-modifying effects of anionic immunoliposomes targeted against apoB, an important component of atherogenic lipoproteins. MethodsTwo sets of nanoliposomes (20mM) were prepared with low (including soy phosphatidylcholine [SPC] and egg phosphatidylglycerol [EPG]) and high (including hydrogenated soy phosphatidylcholine [HSPC] and distearoyl phosphatidylglycerol [DSPG]) phase transition temperature values without cholesterol. In each set, the anionic phospholipid (EPG or DSPG) constituted 75% of total phospholipid content. Immunoliposomes were prepared by conjugating a monoclonal antibody against apoB-100 to the liposomal surface using a post-insertion technique. Fluorescently-labeled immunoliposomes were assessed for their uptake by J774.A1 macrophages. Lipid-modifying effects of immunoliposomes were tested at different doses (50, 100 or 200μmole/g weight) using a tyloxapol-induced hyperlipidemic mouse model. Blood sampling was performed 1h after the injection of each immunoliposomal formulation. ResultsApoB-targeted HSPC/DSPG and SPC/EPG nanoliposomes were both taken up by cultured macrophages but the uptake rate was higher with the former formulation. Both immunoliposomal formulations significantly reduced serum LDL-cholesterol concentrations of hyperlipidemic animals at all tested doses (p<0.001) and this effect lasted for at least 48h. Significant reductions of serum levels of apoB, non-HDL-C, total cholesterol and triglycerides, and elevations of HDL-C levels were also observed. ConclusionIntravenous injection of a single dose of apoB-targeted anionic nanoliposomes improves serum lipid profile parameters. These findings might have implications for the treatment of patients with severe dyslipidemias or statin intolerance.

Requirement of charged lipids for the hexadecanol-induced gelation in the phospholipid bilayer system

We investigated the formation mechanism of the new type of hydrogel we found previously in the lipid system composed of a crude lecithin mixture (PC70) and hexadecanol (HD) [1] by examining purified lipid systems systematically and quantitatively. On the basis of a working hypothesis that the charged lipids included in PC70 play a crucial role in the formation of the homogeneous hydrogel, we analyzed the physicochemical properties and structures of the simplified ternary bilayer system composed of HD, distearoylphosphatidylcholine (DSPC) and distearoylphosphatidylglycerol (DSPG) as a negatively charged lipid by rheometry, freeze-fracture electron microscopy, synchrotron X-ray diffraction and differential scanning calorimetry. We found that the simplified system is able to form a hydrogel though the composition of the system must fall in a fairly narrow range. Structural analyses suggested that the necessary conditions for the gelation are that the fairly rigid bilayer sheets or vesicles with a flat shape are homogeneously distributed in the aqueous solution under an interaction potential without a secondary minimum.

Potential-mediated interaction between dextran sulfate and negatively charged phospholipids films at air/water and liquid/liquid interfaces

Abstract The effect of dextran sulfate (DS) on distearoyl phosphatidyl glycerol (DSPG) and distearoyl phosphatidic acid (DSPA) films formed in the presence of Ca2Cl, LiCl or KCl as aqueous electrolytes, was analyzed by cyclic voltammetry, surface pressure-area and surface potential-area isotherms and Brewster angle microscopy. Experiments of cyclic voltammetry at the water/1,2-dichloroethane interface showed an interfacial adsorption/desorption process in the presence of DSPG, or DSPA, DS and LiCl. It is suggested that this process could correspond to the formation of an interfacial complex DS–Li+–DSPG or DS–Li+–DSPA at positive potentials with respect to the potential of zero charge (pzc) and its desorption from the interface towards the aqueous phase, by complex dissociation, at potentials below pzc. The voltammetric analysis of tetraethylammonium (TEA+) cation transfer, from the aqueous to the organic phase, evidenced a blocking effect of DSPG and DSPA films on that process, whose magnitude depends on both the nature of the phospholipids and the cation forming the aqueous electrolyte. The structure and permeability of those films were altered by the presence of DS, by formation of the complex DS–cation–phospholipid, which produces an expansion of the monolayer, whose extent depends on the cation present in water, and the polar head group of the phospholipid. Electrochemical experiments were completed with compression isotherms for DSPG and DSPA monolayers both in the absence and in the presence of DS. In this case, as opposed to the voltammetric results, a negligible effect of DS was observed in the isotherms. This apparent contradiction could be explained considering the effect of polarization, which enables the accumulation of cations at the interface, favouring the formation of the DS–cation–phospholipid complex which is responsible for the increase in the film permeability. Similarly, the thickness values for phospholipid films obtained from the Brewster angle microscopy experiments were the same either in the absence or in the presence of DS at any lateral pressure value, which is a direct evidence of lack of interaction between DS and DSPA or DSPG molecules at open circuit. Therefore, it was concluded that the formation of the complex DS–cation–phosholipid, responsible for the increase in permeability observed in voltammetric experiments, must be attributed to the polarization of the interface. The application of high positive potentials at the interface promotes cations accumulation, which neutralize the negative charge in phosphate groups and in DS and allows their interaction.

Effect of chitosan on distearoylphosphatidylglycerol films at air/water and liquid/liquid interfaces

The effect of chitosan on distearoylphosphatidylglycerol (DSPG) films was analyzed by cyclic voltammetry, surface pressure-area and surface potential-area isotherm and Brewster Angle Microscopy. Experiments of cyclic voltammetry at a liquid/liquid interface demonstrated a blocking effect of DSPG to tetraethylammonium (TEA+) cation transfer from the aqueous to the organic phase. This effect was reversed by the presence of chitosan, which modifies the film structure. Special emphasis was placed on the nature of the supporting aqueous electrolyte (LiCl or CaCl2). In the presence of LiCl the permeability of the film increases when chitosan is present in the aqueous phase, minimizing the blocking effect of the film on TEA+ transfer probably due to the presence of bare zones at the interface. Oppositely, in presence of Ca2+, the enhancement of permeability was not observed, probably due to the impediment of chitosan to penetrate into the very tightly compacted film of DSPG. Electrochemical experiments were completed with viscosity measurements to explain the variation of diffusion coefficients for TEA+. Isotherms of compression for DSPG monolayers modified with chitosan, demonstrate that this polymer produces an expansion of the DSPG film and modifies the compression factor, for both electrolytes studied. Images of Brewster angle microscopy evidence an increase in the optical thickness of the DSPG films in presence of chitosan indicating that the polymer interacts with DSPG molecules at low and high molecular areas.

Interaction of triflupromazine with distearoylphosphatidylglycerol films studied by surface pressure isotherms and cyclic voltammetry at a 1,2-dichloroethane/water interface

The effect of triflupromazine (TFP) on molecular packing of distearoylphosphatidylglycerol (DSPG), adsorbed at the water/1,2-dichloroethane interface, was investigated using cyclic voltammetry (CV) and surface pressure–molecular area isotherm. TFP partition in the DSPG monolayer changes the structure of the film. The results indicate that a fluidizing effect, dependent on the time and the drug concentration, takes place leading to an increase in the permeability of the film. This effect is produced by TFP either from the organic or from the aqueous phase due to the amphiphilic nature of this drug. Nevertheless, the expansion of the film is enhanced when TFP acts from the aqueous phase.

Association of Acenaphthoporphyrins with Liposomes for the Photodynamic Treatment of Leishmaniasis

Acenaphthoporphyrins are potential photosensitizers for photodynamic therapy, but their hydrophobicity limits their potential. Liposomes have been widely investigated as delivery vehicles that can transport hydrophobic drugs in biological systems. Here we study the association of acenaphthoporphyrins with liposomes made up of dimyristoyl phosphatidylcholine (DMPC), and to liposomes made up of a mixture of DMPC, cholesterol (Chol) and distearoyl phosphatidylglycerol (DSPG) in a 2:1:0.8 molar ratio to evaluate how liposome composition affects association constants. In liposomes consisting only of DMPC, the smaller monoacenaphthoporphyrin had the largest association constant of 5.5 x 10(4) m(-1) while the larger adj-diacenaphthoporphyrin and opp-diacenaphthoporphyrin (ODP) had smaller association constants at 1.8 x 10(4) and 1.5 x 10(4) m(-1), respectively. The addition of liposomal Chol and DSPG has little effect on the magnitudes of the association constants. Polarization studies show that the acenaphthoporphyrins are driven far into the lipid bilayer to minimize polar-nonpolar interactions. Confocal microscopy confirms that the DMPC liposomes transport the porphyrins into promastigotes of Leishmania tarentolae. The compounds associated with DMPC:Chol:DSPG liposomes are effective in vitro against axenic and intracellular amastigotes of the pathogenic Leishmania panamensis. The effectiveness of the compounds is enhanced upon exposure of cultures to visible light.

Evaluation of phospholipid and liposomal S-adenosyl methionine for the treatment of liver injury in a murine model

We have used a murine model of Acetaminophen induced hepatoxicity to determine if S-adenosyl methionine 1,4 butanedisulfonate (SD4) in liposomes can prevent liver injury when administered immediately prior to acetaminophen, as judged by serum aspartate aminotransferase and alanine aminotransferase levels, and histological evidence of liver necrosis. No protection was observed when mice received 1 g/kg unencapsulated SD4. Partial protection was observed with 5 or 0.5 mg/kg SD4 in unextruded distearoylphosphatidylglycerol (DSPG) liposomes. Protection comparable to that seen in mice receiving encapsulated SD4 is achieved when mice received lipid alone in equivalent amounts, suggesting that the contribution of encapsulated SD4 to the efficacy of the liposomes may be minimal. Unextruded distearoylphosphatidylcholine (DSPC) liposomes show only slight effects even at 50 mg/kg SD4. This is likely caused by the size of unextruded DSPC lipsomes, because extruded DSPC liposomes, whose size is smaller, are of comparable efficacy to unextruded DSPG liposomes. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1800–1809, 2010

A novel and simple type of liposome carrier for recombinant interleukin-2

The strong interaction between recombinant interleukin-2 (IL-2) and liposome was characterized and its possible application to drug-delivery control considered. The liposomes were prepared with egg phosphatidylcholine, distearoyl-phosphatidylglycerol (DSPG), dipalmitoyl-phosphatidylcholine, dipalmitoyl-phosphatidylglycerol or distearoyl-phosphatidylcholine (DSPC). Small and hydrophobic liposomes were selected, which were composed of saturated and long-fatty-acid-chain phospholipids. When the composition and the mixture ratio of IL-2 and the liposomewere optimized, morethan 95% ofthe lyophilized IL-2 (Imunace, 350000 JRU) was adsorbed consistently onto the DSPC-DSPG liposome (molar ratio, 10:1; 25 micromol mL(-1); 30 nm in size). Merely mixing IL-2 lyophilized with liposome suspension is convenient pharmaceutically. After intravenous administration to mice, liposomal IL-2 was eliminated half as slowly from the systemic circulation as free IL-2, with more than 13 and 18 times more IL-2 being delivered to the liver and spleen, respectively. After subcutaneous administration of liposomal IL-2 to mice, the mean residence time of IL-2 in the systemic circulation was 8 times that of free IL-2. These results show that IL-2 consistently adsorbs onto the surface of liposomes after optimization of its composition and mixing ratio. Intravenous and subcutaneous administration to mice demonstrates the gradual release of IL-2. Further trials are warranted using these liposomes.

Investigation on the interactions between pirarubicin and phospholipids

Differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and quantum calculation based on molecular modeling were applied to investigate the interaction between pirarubicin (THP), an anthracycline antibiotic frequently used in chemotherapy, and zwitterionic distearoylphosphatidylcholine (DSPC) or anionic distearoylphosphatidylglycerol (DSPG). DSC and FTIR studies suggested that DSPG bilayers were less perturbed by THP than those of DSPC, and this might be due to the strong interactions between NH 3 + of THP and the phosphate (PO 2 − ) group in the polar head of DSPG, which limit the further access of THP into its bilayers. Quantum calculation results based on molecular modeling could further confirm the DSC and FTIR conclusions. Meanwhile, it could well translate the calorimetric and spectroscopic phenomena into the underlying physical knowledge. Interactions between THP and phospholipids can play a critical role in the liposomal drug delivery system, especially in the safety mechanism elucidation and rational formulation design.

Morphology modifications in negatively charged lipid monolayers upon mitochondrial creatine kinase binding

Mitochondrial creatine kinase (mtCK) may participate to membrane organization at the mitochondrial level by modulating lipid state and fluidity. The effect of the protein on lipid phase behaviour of different acyl chain length phosphatidylglycerol monolayers was analyzed from pressure-area isotherms and from the compressional modulus variation with respect to the surface pressure. Monolayer morphology was visualized by Brewster angle microscopy. No condensation effect was visible on dimyristoylphosphatidylglycerol (DMPG). For the other PG monolayers tested, dipalmitoylphosphatidylglycerol (DPPG) and distearoylphosphatidylglycerol (DSPG), mtCK facilitated the formation of a liquid condensed phase. The effect depended on the surface pressure at which transition phase occurred. The effect of mtCK was more pronounced for tetramyristoylcardiolipin (TMCL) monolayers, as liquid condensed regions appeared 10 mN/m below the transition phase of the pure TMCL monolayer. The observed domains were circular and rather uniform, indicating a stabilization of the condensed phase. The same effect, namely an overall condensation of the monolayer with formation of circular domains, was observed upon protein injection beneath TMCL monolayers in different condensation states at constant area. MtCK ability to induce and stabilize a LC phase on monolayers could have important consequences in membrane organization and emphasize its structural role at mitochondrial level.

Preparation, Optimization, and Characterization of Topotecan Loaded PEGylated Liposomes Using Factorial Design

This study reports the development of liposomal system for a potent antitumor drug, topotecan. To achieve this goal conventional and PEGylated liposomes were prepared according to a factorial design by hydration method followed by extrusion. Parameters such as type of lipid, percentage of cholesterol, percentage of phosphatidylglycerols, percentage of polyethylene glycol (PEG)-lipids, and drug to lipid molar ratio were considered as important factors for the optimizing the entrapment and retention of topotecan inside the liposomes. The size and zeta-potential of the PEGylated and conventional liposomes were measured by particle size analyzer and zeta-potentiometer, respectively. The stability and release characteristics of PEGylated liposome loaded topotecan were compared with conventional liposomes and free topotecan.The optimized PEGylated [distearoyl phosphatidylcholine (DSPC)/cholesterol/ distearoyl phosphatidylglycerol (DSPG)/ distearoyl phosphatidylethanolamine-PEG2000 (DSPE-PEG2000); 7:7:3:1.28] and related conventional [DSPC/cholesterol/DSPG; 7:7:3] liposomes showed a narrow size distribution with a polydipersity index of 0.15 and 0.10, an average diameter of 103.0 ± 13.1 and 95.2 ± 11.10 nm, and with drug loading of 11.44 and 6.21%, respectively. Zeta-potential was −10 ± 2.3 and −22 ± 2.8 mV for PEGylated and conventional liposomes, respectively. The results of stability evaluation showed that the lactone ring of topotecan was notably preserved upon liposome encapsulation. PEGylated liposomes containing topotecan showed a significant decrease (P < 0.001) in release rate in comparison with conventional leptosomes. These results indicate the suitability of PEGylated liposomes in controlling topotecan release.The prepared liposomes (especially PEGylated liposomes) as those described here may be clinically useful to stabilize and deliver topotecan for the treatment of cancer.