Liposomes from hydrogenated egg yolk lecithin

Egg yolk lecithin is a lipid, frequently been used for the liposome preparation. Such liposomes, however, are sensitive to oxidation and relatively permeable to encapsulated substances. The catalytic hydrogenation of egg yolk lecithin is one possibility to modify the properties mentioned. The authors deal with preparation and characterization of hydrogenated egg yolk lecithin. Liposomes from native and hydrogenated egg yolk lecithin--also in combination with cholesterol--are compared. Liposomes with hydrogenated egg yolk lecithin as phospholipid component exhibit a significantly increased encapsulation capacity and an essentially improved stability. The permeation of electrolytes, carboxyfluorescein and of the cytostatic drug daunorubicin is studied.     

The effect of ileal brake activators on the oral bioavailability of atenolol in man

The aims of this study were to develop novel liposome formulations for tranexamic acid (TA) from various lipid compositions [neutral (hydrogenated soya phosphatidylcholine and cholesterol), positive (stearylamine) or negative (dicetyl phosphate) charged lipid], and to investigate the effects of concentrations of TA (5 and 10% in DI water) and charges on the physicochemical properties of liposomes. Liposomes were prepared by chloroform film method with sonication. The physical (appearance, pH, size, morphology) and chemical (drug encapsulation efficiency, transition temperature, enthalpy of transition) properties of liposomes were characterized. The TA contents were determined spectrophotometrically at 415 nm, following derivatization with 2,4,6-trinitrobenzosulfonic acid. The charged liposomes demonstrated better physical stability than the neutral liposomes. The percentages of TA entrapped in all liposome formulations varied between 13.2 and 15.6%, and were independent of TA concentrations and charges of liposomes. Charges affected the physical stability, pH and size of liposomes. The particle sizes of negative blank and positive liposomes (with and without the entrapped drug) were approximately 10 times larger than the negative liposome with the entrapped TA. The multilamellar 7:2:1 molar ratio of hydrogenated soy phosphatidylcholine/cholesterol/dicetyl phosphate entrapped with 10% TA liposome (10%TA,-) was selected for further release study, due to its high physical stability, small particle size and relatively high drug encapsulation efficiency.     

Lack of effect of added liposomes on veratridine activation of 22Na+ uptake in rat brain synaptosomes

Partially purified egg yolk phospholipids in the form of both small and large unilamellar liposomes at lipid concentrations of 30 mg/ml and higher inhibited veratridine activation of sodium channel specific 22Na+ uptake by rat brain synaptosomes. Chromatographically purified egg yolk phosphatidyl choline liposomes did not show this inhibition even at lipid concentrations up to 125 mg/ml. This demonstrates that the inhibition of veratridine-activated 22Na+ uptake was due to an impurity in the lipid rather than an ability of the liposomes to absorb and immobilize the lipophilic veratridine molecule.     

Liposomes for Topical Use: A Physico-Chemical Comparison of Vesicles Prepared from Egg or Soy Lecithin

Developments in nanotechnology and in the formulation of liposomal systems provide the opportunity for cosmetic dermatology to design novel delivery systems. Determination of their physico-chemical parameters has importance when developing a nano-delivery system. The present study highlights some technological aspects/characteristics of liposomes formulated from egg or soy lecithins for topical use. Alterations in the pH, viscosity, surface tension, and microscopic/macroscopic appearance of these vesicular systems were investigated. The chemical composition of the two types of lecithin was checked by mass spectrometry. Caffeine, as a model molecule, was encapsulated into multilamellar vesicles prepared from the two types of lecithin: then zeta potential, membrane fluidity, and encapsulation efficiency were compared. According to our observations, samples prepared from the two lecithins altered the pH in opposite directions: egg lecithin increased it while soy lecithin decreased it with increased lipid concentration. Our EPR spectroscopic results showed that the binding of caffeine did not change the membrane fluidity in the temperature range of possible topical use (measured between 2 and 50 °C). Combining our results on encapsulation efficiency for caffeine (about 30% for both lecithins) with those on membrane fluidity data, we concluded that the interaction of caffeine with the liposomal membrane does not change the rotational motion of the lipid molecules close to the head group region. In conclusion, topical use of egg lecithin for liposomal formulations can be preferred if there are no differences in the physico-chemical properties due to the encapsulated drugs, because the physiological effects of egg lecithin vesicles on skin are significantly better than that of soy lecithin liposomes.     

Stability and drug release properties of liposomes containing cytarabine as a drug carrier

Liposomes were studied as a drug delivery system. Multilamellar vesicles, small unilamellar vesicles and large unilamellar vesicles containing cytarabine were prepared using egg yolk lecithin and cholesterol. Large unilamellar vesicles showed the highest encapsulation efficiency of all and their encapsulation efficiency increased as the buffer volume decreased. Cholesterol increased the stability of liposomal drug products as drug carriers and reduced the permeability of drug across the liposomal membrane. The release rate of cytarabine increased with incubation temperature and decreased with cholesterol incorporation in liposomal membrane. The release mechanism of cytarabine from large unilamellar vesicles in vitro was chiefly due to simple diffusion across the liposomal membrane rather than liposomal rupture.     

Preparation of liposome using egg yolk

In this study, 162 students in the 6 year Pharmacy Program at the School of Pharmacy, Iwate Medical University were asked to prepare liposomal preparations using chicken egg yolk and to evaluate their properties with the aim of developing novel liposomes. High-purity lecithins are generally used for preparing liposomes but they are expensive. On the other hand, egg yolk has various components, including lecithin and cholesterol, which are important components for the formation of liposomes, so it was hypothesized that liposomes prepared from egg yolk may participate in the formation of cell membrane in chicks. Both liposomes from egg yolk (YL) and from lecithin (LL) exhibited Malthesian crosses using a polarizing microscope and multilamellar vesicles were observed, confirming that liposomal preparations from egg yolk were useful. The particle size of YL was about 100 nm with one peak. Furthermore, the YL are believed to be viable under different conditions because the particle size did not change when they were prepared in buffers having different pH values. The results of these experiments indicate that liposomal preparations from egg yolk can serve as natural materials, although some obstacles remain. This is a unique approach for carrying out practical training in our 6 year pharmaceutical science program.     

去氢骆驼蓬碱脂质体制备工艺优化及抗肝癌活性

目的 制备去氢骆驼蓬碱脂质体并对其制备工艺进行优化，评价脂质体的相关表征及对肝癌细胞的毒性。方法 用薄膜水化法制备去氢骆驼蓬碱脂质体。以包封率作为评价指标，以大豆卵磷脂和药物的质量比、大豆卵磷脂与胆固醇的质量比和超声时间作为评价因素对脂质体包封率的影响。并对脂质体的粒径、Zeta电位、外观和稳定性进行评价。CCK-8法对比去氢骆驼蓬碱和去氢骆驼蓬碱脂质体的抗肝癌细胞增殖活性。结果 最优制备工艺：大豆卵磷脂和药物的质量比为11.4：1，大豆卵磷脂与胆固醇的质量比为4.4：1，超声时间为33 min。在此条件下制备的脂质体的包封率为81.88%，粒径为143.65 nm，Zeta电位为-12.68 mV，低温环境稳定性良好，具有缓释效应。去氢骆驼蓬碱脂质体的抗肝癌细胞增殖活性大于裸药。结论 所制得的去氢骆驼蓬碱脂质体包封率和稳定性均符合标准。将去氢骆驼蓬碱制备成为脂质体能提高其抗肝癌细胞增殖活性。     

Liposome–skin interactions and their effects on the skin permeation of drugs

The aim of the study was to evaluate the interaction of phospholipid liposomes with skin and stratum corneum lipid liposomes (SCLLs). The influence of phospholipid liposomes on the skin permeability of model drugs was also studied. The transdermal flux of the drugs applied in various phospholipid containing formulations through human epidermis was studied in diffusion chambers. Liposomes in water solutions did not enhance the skin permeability of the drugs, but when ethanol (32% w/v) was present in the donor with EPC (egg yolk lecithin), permeabilities of some model drugs were substantially increased. Confocal microscopy studies revealed that EPC do not penetrate into the skin from water solutions, while from ethanol solutions, EPC penetrates deeply into the stratum corneum. Also, resonance energy transfer between different liposome compositions and the release of calcein from SCLLs showed that interactions between phospholipid liposomes and SCLLs increased with increasing ethanol concentration in the liposome solutions.     

Effects of Linkers on the Development of Liposomal Formulation of Cholesterol Conjugated Cobalt Bis(dicarbollides)

Boron neutron capture therapy (BNCT) remains an important treatment arm for cancer patients with locally invasive malignant tumors. This therapy needs a significant amount of boron to deposit in cancer tissues selectively, sparing other healthy organs. Most of the liposomes contain water-soluble polyhedral boron salts stay in the core of the liposomes and have low encapsulation efficiency. Thus, modifying the polyhedral boron core to make it hydrophobic and incorporating those into the lipid layer could be one of the ways to increase drug loading and encapsulation efficiency. Additionally, a systematic study about the linker-dependent effect on drug encapsulation and drug-release is lacking, particularly for the liposomal formulation of hydrophobic-drugs. To achieve these goals, liposomal formulations of a series of lipid functionalized cobalt bis(dicarbollide) compounds have been prepared, with the linkers of different hydrophobicity. Hydrophobicity of the linkers have been evaluated through logP calculation and its effect on drug encapsulation and release have been investigated. The liposomes have shown high drug loading, excellent encapsulation efficiency, stability, and non-toxic behavior. Release experiment showed minimal release of drug from liposomes in phosphate buffer, ensuring some amount of drug, associated with liposomes, can be available to tumor tissues for Boron Neutron Capture Therapy.     

Solvent constraints on the property space of acetylcholine. 2. Ordered media

The objective of this study was to investigate the conformational and property spaces of acetylcholine in hydrated octanol and in a membrane model. Molecular dynamics simulations of long duration (15 ns) were carried out, yielding 3000 conformers. For each, we calculated N(+)-C8 distance, solvent-accessible surface area (SAS), polar surface area (PSA), dipole moment, and lipophilicity (virtual logP). Their variations as a function of the dihedral angles tau(2) and tau(3) remained unexpectedly broad and comparable to those seen previously in a vacuum, in water, and in chloroform.(12) Thus, each of the seven conformational clusters was able to access a marked proportion of the lipophilicity space accessible to acetylcholine (0.40 in the logP scale). Histograms of logP distributions revealed two overlapping populations, namely more lipophilic and more hydrophilic. Their deconvolution into two Gaussian curves demonstrated solvent-mediated constraints on the lipophilicity space of acetylcholine, clearly showing how a polar medium favors polar conformers, whereas the opposite is true for media of low polarity.     

Hydrophilic gels containing chlorophyllin-loaded liposomes: development and stability evaluation

The aim of this study was to develop and characterize hydrophilic gels containing chlorophyllin(CHL)-loaded liposomes as well as to evaluate their stability. Two different CHL-loaded liposome dispersions using non-hydrogenated and hydrogenated soybean lecithin were prepared, characterized for their particle size, polydispersity index and trapping efficiency and incorporated in Carbopol 940 NF hydrogel. The gels obtained were analyzed for flow properties, pH values and CHL content. The control liposome-free gel was obtained by incorporating the CHL solution in the hydrogel. The stability of the gels was evaluated in terms of rheological properties, pH values and CHL content during 6 months' storage at 20 +/- 2 degrees C. Suitable gel formulations for topical use were obtained revealing shear-thinning plastic flow behaviour without significant thixotropy during the whole period of examination. High yield values of the samples during the whole period indicated a long-term stability of the gel formulations. The gel formulations expressed a mild acid value acceptable for topical preparations. After 6 months' storage the CHL content was highest in the gel containing non-hydrogenated lecithin liposomes, followed by the gel containing hydrogenated lecithin liposomes and liposome-free gel, indicating that the encapsulation of CHL in liposomes led to a greater stability of CHL.     

A novel method to prepare liposomes containing amikacin.

This work describes a novel method to prepare liposomal amikacin composed of soyabean lecithin and cholesterol; these were also prepared using two other methods (cast film method and proliposome method). Encapsulation efficiency was evaluated. Liposomes prepared by the new method, which combines the method of preparing proliposomes with freeze-drying, had the highest encapsulation efficiency. The influence of drug to lipid ratio on the encapsulation efficiency was investigated. The in vitro efflux of amikacin from liposomes with different lecithin: cholesterol ratios was also investigated.     

In vivo study of liposomes as drug carriers to oral mucosa using EPR oximetry

The purpose of this study was to select the best types of liposomes for use as drug carriers for topical treatment of oral mucosal lesions. Electron paramagnetic resonance (EPR) oximetry, using the paramagnetic probe lithium phthalocyanine, was used in vivo to measure the effects of a hyperemic drug, benzyl nicotinate (BN) which was incorporated into liposomes of varying size and composition. The liposomes were made from either hydrogenated or non-hydrogenated soy lecithin and mixed with polymethyl methacrylate ointment for application. EPR oximetry was used to measure the partial pressure of oxygen (pO2) in the oral mucosa before and after application of liposomes. It was found that the most pronounced changes of pO2 in oral mucosa and also the longest action of the drug occurred after the topical application of BN in multi-lamellar liposomes made from hydrogenated soy lecithin (p<0.0001). When these liposomes were applied to oral mucosa over 3 successive days it was found that pO2 increased the most on the first day, the effect gradually decreased following application on the second and third days. The duration of the resulting hyperemia was the longest on the second day (p<0.01). Among the examined carriers, multi-lamellar liposomes made from hydrogenated soy lecithin appear to be the most appropriate for local drug delivery to oral mucosa.     

The binding of chlorpromazine to bilayer liposomes. Evaluation of stoichiometric constants from equilibrium and steady state studies

The binding of chlorpromazine to egg yolk lecithin bilayer liposomes has been studied with equilibrium dialysis as well as with a new steady state method.The influence of the cholesterol amount previously incorporated into the liposomes to the binding of chlorpromazine was examined. The binding of chlorpromazine was evaluated in terms of stoichiometric constants and shows a strong positive cooperative binding step, followed by an equally strong negative cooperative step.The first step, which is only detectable with the steady state method may be related to the partition of chlorpromazine into the lipophilic bilayer core, whereas the second and the following steps describe the overall saturation of the liposome membrane.The binding of chlorpromazine is attenuated by increasing amounts of cholesterol present in the bilayer liposomes.Investigating the binding to liposomes without cholesterol a saturation up to 75 per cent can be reached experimentally.     

克班宁长循环脂质体的制备工艺

目的:研究克班宁长循环脂质体的处方筛选和制备工艺。方法:采用硫酸铵梯度法制备克班宁长循环脂质体,以包封率和载药量为评价指标,采用葡聚糖凝胶过滤法分离脂质体,紫外分光光度法测定克班宁含量,采用正交设计优化制备工艺。结果:最佳工艺为:药脂比为1:6,胆固醇与磷脂比为9:12,0.15 mol·L^-1的硫酸铵溶液,以PBS液(pH7.4)为透析介质,在40 ℃水浴,40 r·min^-1条件下孵化20 min。结论:硫酸铵梯度法制备的克班宁长循环脂质体处方合理,工艺可行,包封率较高。     

正交试验优选哈西奈德脂质体制备工艺

目的优选哈西奈德脂质体的最佳制备工艺。方法以胆固醇、卵磷脂为载体,采用薄膜分散法制备哈西奈德脂质体,以包封率为评价指标,采用正交试验进行系统研究,筛选哈西奈德脂质体的最佳制备工艺。结果哈西奈德脂质体的最佳制备工艺为：卵磷脂与胆固醇质量之比为6：1,氯仿与甲醇体积之比为1：1,水化温度为60℃,磷酸盐缓冲液的pH为6．5。优化后制备3批脂质体,平均包封率为93．29％±0．77％,粒径范围为98．26～102．54nm。结论选工艺制备的脂质体包封率高,粒径较均匀,形态较好,结构完整,该方法简单可行。     

胸腺五肽脂质体的研制

目的:制备胸腺五肽脂质体并进行质量评价。方法:采用复乳法制备胸腺五肽脂质体,以聚乳酸-羟基乙酸共聚物(PLGA)及卵磷脂为成球材料、以胸腺五肽为主药制备脂质体。以明胶浓度、PLGA浓度和卵磷脂浓度为考察因素,以包封率和载药量为考察指标设计L(934)正交试验优化基质处方并进行验证试验。通过测定优化处方所制脂质体粒径、包封率、体外累积释放百分率等评价脂质体质量。结果:优化基质处方为明胶、PLGA和卵磷脂浓度分别为100、200、100mg.mL-1。所制脂质体形态完整,平均粒径为(9.03±0.83)μm,载药量与包封率分别为(1.81±0.03)与(74.4±1.4),20d的累积释药百分率达90以上。结论:所制胸腺五肽脂质体工艺简单、重现性好,包封率和载药量高,具有显著的缓释作用。     

正交试验优选盐酸川芎嗪脂质体的制备工艺

目的:优选盐酸川芎嗪脂质体的制备工艺。方法:以乙醚注入法制备川芎嗪脂质体,采用正交试验,以包封率为指标,以药物与大豆卵磷脂用量比、PBS缓冲液的pH值、胆固醇与大豆卵磷脂用量比、乙醚与PBS缓冲液用量比为考察因素,优选制备工艺。结果:最佳工艺条件为药物:大豆卵磷脂为1:12,PBS缓冲液pH为7.5,胆固醇:大豆卵磷脂为1:2,乙醚:PBS缓冲液为1:2。结论:该制备工艺可行、稳定、重现性好,可为工业化生产提供理论依据。     

Thermodynamic study of the transfer of acetanilide and phenacetin from water to different organic solvents

The molar (K(C)(o/w)) and rational (K(X)(o/w)) partition coefficients in the octanol/buffer, i-propyl myristate/buffer, chloroform/buffer, and cyclohexane/buffer systems were determined for acetanilide and phenacetin at 25.0, 30.0, 35.0, and 40.0 degrees C. In all cases except for cyclohexane, the K(C)(o/w) and K(X)(o/w) values were greater than unity. This demonstrates that these two drugs have predominantly lipophilic behavior. Gibbs and van't Hoff thermodynamic analyses have revealed that the transfer of these drugs from water to organic solvents is spontaneous and that it is mainly driven enthalpically for i-propyl myristate and chloroform, and entropy-driven for octanol and cyclohexane.     

Deformable liposomes for dermal administration of methotrexate

Deformable liposomes were prepared to investigate the effectiveness of dermal administration of methotrexate (MTX). The phospholipids used to prepare the liposomes were soybean lecithin (PC) or hydrogenated lecithin (HPC) and dipotassium glycyrrhizinate (KG) as surfactant. The lipid/KG ratio (w/w) was 2:1 and 4:1. Liposomes size, entrapment efficiency and MTX release through dialysis membrane were determined and the interaction between MTX and liposomes was investigated using differential scanning calorimetry. The MTX amount permeated through pig skin were three- to four-fold higher using liposomes containing KG compared to those from water solution or normal liposomes. No significant differences were observed between PC-KG liposomes and HPC-KG liposomes. At the end of the skin permeation assay using deformable liposomes, up to 50% of the administered dose was found in the skin. This capability depends on the self-regulating carrier deformability. These results suggest that liposomes containing KG may be of value for the topical administration of MTX in the treatment of psoriasis.