Encapsulation in cationic liposomes enhances antitumour efficacy and reduces the toxicity of etoposide, a topo-isomerase II inhibitor

Etoposide exerts its antineoplastic effect by forming a ternary complex with topo-isomerase II and DNA, leading to DNA breaks and cell death. However, it causes myelosuppression and its lipophilicity poses a major limitation during administration. Liposomes have been reported to increase the efficacy and reduce the toxicity of antineoplastic agents. Recent evidence suggests that cationic liposomes bind efficiently to tumours. The present study was thus designed to encapsulate etoposide in cationic liposomes and to evaluate its antitumour efficacy and systemic toxicity in comparison with a conventional parenteral formulation. Etoposide encapsulated in liposomes was synthesised by thin film hydration followed by an extrusion method. Fibrosarcoma was induced in mice by subcutaneous administration of 20-methylcholanthrene. Chemotherapy was started when the tumour reached 200 mm(3) in volume. Liposomal etoposide (10 mg/m(2)/day for 5 days) significantly delayed tumour growth as compared to non-liposomal etoposide. The median time of death was calculated to be 19.5, 26.25 and 56 days in vehicle-treated controls, non-liposomal-etoposide- and liposomal-etoposide-treated groups, respectively. A transient reduction in body weight was seen in both the liposomal- and non-liposomal-etoposide-treated groups. The maximum tolerated dose was however significantly higher in the group treated with liposomal etoposide, which also exhibited a lesser degree of myelosuppression than the animals treated with non-liposomal etoposide. The present findings suggest that cationic liposomes could be considered as potential for delivery of etoposide to tumours.     

Improved antitumor efficacy and reduced toxicity of liposomes containing bufadienolides

Long-circulating liposomes are used extensively nowadays for enhancing the therapeutic effect and reducing the toxicity of anticancer drugs. In this paper, a traditional Chinese medicine, toad venom, which has long been used in the clinic for tumor therapy with unpleasant side effects, was incorporated into poloxamer modified liposomes to increase its antitumor effect and reduce its toxicity. Our preparation of bufadienolides liposomes had a particle size of around 70 nm and an entrapment efficiency of about 87.6%. Lyophilized liposomes well retained their appearance, particle size and encapsulation efficiency for 3 months. The in vitro release results verified the sustained release properties of the bufadienolides liposomes. The concentration of bufadienolides in modified liposomes that caused 50% cell killing was much lower than that of free drug for both Lovo cells and NCI-H157 cells. Compared to the bufadienolides solution and the unmodified liposomes, the bufadienolides liposomes significantly prolonged the retention time and increased the area under the curve in vivo. The antitumor efficiency of the bufadienolides liposomes against mice bearing H22 liver cancer cells and Lewis pulmonary cancer cells were 2.15 and 2.96, respectively, times that of a bufadienolides solution at the same toxicity. The safety test results demonstrated that the bufadienolides liposomes had an LD₅₀ that was 3.5 times the LD₅₀ of bufadienolides solution and caused no allergen-related or blood vessel irritation effects. All these results proved that poloxamer modified bufadienolides liposomes have improved antitumor efficacy and safety.     

重组人生长激素脂质体的制备及载药研究

目的采用乙醇注入法结合反复冻融技术制备重组人生长激素脂质体,并考察影响包封率的主要因素。方法采用乙醇注入法制备空白脂质体,并通过反复冻融载药,采用葡聚糖凝胶柱分离结合CBB G-250染色法测定游离药物含量,计算包封率;考察孵化时间、孵化温度、冻融次数对包封率的影响;对冻干制品的外观、复溶速度、粒径及分布进行综合评分,优选冻干支持剂。结果孵化时间为40 min、孵化温度为10℃、冻融次数为3次时,能够获得较高包封率的脂质体,包封率为63.59%。海藻糖在脂质体冷冻干燥过程中具有最好的保护作用。结论乙醇注入法结合反复冻融可用于大分子蛋白质类脂质体的制备。     

Preparation,characterization and anticancer therapeutic efficacy of cisplatin-loaded niosomes

This study developed a carrier for anticancer drug, cisplatin. Cisplatin-loaded niosomes (CP-NMs) were prepared under optimized conditions with Span 40 and cholesterol as the excipients, and then lyophilized and characterized. Their anticancer efficacy was tested in rabbits bearing VX2 sarcoma. The obtained spherical-looking vesicles showed a diameter of 7.73?±?1.49?µm with a zeta-potential of 0?mV. The entrapment efficiency was 76.93?±?2.67%, and drug loading 2.96?±?0.10%. In vitro release tests gave a t_50% of 8.36?h. The rabbits locally injected with the CP-NMs gave significantly superior results of inhibition of tumour growth, much lower mortality and improved results of body weight change and inhibition of tumour metastasis to inguinal lymph nodes and liver compared to those treated in the same way with the drug solution. The inspiring anticancer results indicated that the CP-NMs might be developed as an effective anticancer preparation with low toxicity.     

Preparation and physicochemical characterization of atovaquone‐containing liposomes

This work describes the preparation and the physicochemical properties of atovaquone‐loaded liposomes. It also describes drug release from the liposomes. As many factors can influence liposome stability, we studied several formulations, including different concentrations of atovaquone, phospholipids, and cholesterol. The effect of atovaquone (ATV) concentration was also evaluated. The highest binding percentage (100±2.5%) was obtained under alkaline conditions for a 2 mg/ml concentration of ATV. The percentage of encapsulation decreased significantly when drug concentrations increased. Drug uptake (expressed per unit mass of phospholipids) was nonlinearly related to equilibrium ATV concentration. A Langmuir‐type sorption was suggested (r = 0.978). In acidic or neutral buffer, the binding percentage reached 42.1 ± 0.02%. The increase of phospholipids and cholesterol concentrations did not significantly improve the ATV binding yield for the lowest ATV concentration. Conversely, ATV binding was significantly increased for the highest ATV concentration. All the formulations tested gave monodispersed liposomes with a mean diameter around 260 nm. The dilution (1/5–1/20) of liposomes in alkaline conditions induced a significant release of ATV (74% release). In acidic or neutral buffer no release was observed, suggesting an encapsulation process. Drug Dev. Res. 47:155–161, 1999. © 1999 Wiley‐Liss, Inc.     

Preparation of microencapsulated liposomes, II. Systems containing nylon-gelatin and nylon-gelatin-acacia walling material

Liposome suspension was encapsulated and isolated in nylon-gelatin and nylon-gelatin-acacia walled microcapsules. The resulting liposomal microcapsules could be stored in the dry state as a free-flowing powder. Liposomes remained intact after the microencapsulation, and encapsulation efficiency was greater than 90 per cent. The release of drug from microcapsules was retarded in the presence of drug-loaded liposomes.     

Preparation,characterization and evaluation of multi-component-loaded liposomes containing Tat-TOS,phospholipase D inhibitor and doxorubicin

In the present study, we aimed to co-load the α-TOS conjugate Tat-TOS with the phospholipase D inhibitor FIPI and the antitumor drug doxorubicin (DOX) in a liposome delivery system for antitumor metastasis. Firstly, Tat-TOS was synthesized by solid-phase synthesis, and its structure was confirmed. The ability of free and liposomal Tat-TOS to induce apoptosis in vitro was evaluated by flow cytometry. Biodistribution of Tat-TOS-loaded liposomes was investigated by a molecular imaging system. Multi-component-loaded liposomes modified with Tat-TOS containing FIPI and DOX was prepared by thin film dispersion method in combination with pH gradient method and post-insertion method. Physicochemical properties were determined, and the in vitro uptake ability of the formulations was evaluated. The results showed that the prepared liposomes were characterized by a uniform particle size distribution and small particle size. The encapsulation efficiency of FIPI and DOX exceeded 85%. Both free and liposomal Tat-TOS significantly improved the activity of inducing apoptosis of tumor cells. The liposomes modified with Tat-TOS were apparently accumulated in normal lung tissue and tumor metastasized lung. Multi-component-loaded liposomes exhibited the strongest cell uptake capacity, suggesting a stronger anti-metastatic effect and anti-tumor activity in vivo.     

Preparation of microencapsulated liposomes,II. Systems containing nylon-gelatin and nylon-gelatin-acacia walling material

Abstract

Liposome suspension was encapsulated and isolated in nylon-gelatin and nylon-gelatin-acacia walled microcapsules. the resulting liposomal microcapsules could be stored in the dry state as a free-flowing powder. Liposomes remained intact after the microencapsulation, and encapsulation efficiency was greater than 90 per cent. the release of drug from microcapsules was retarded in the presence of drug-loaded liposomes.     

Liposomes as drug carrier systems. Preparation, classification and therapeutic advantages of liposomes]

Bangham et al. (1965) created first the concept of the liposome as a microparticulate lipoidal vesicle separated from its aqueous environment by one or more lipid bilayers. Later Gregoriadis and Ryman (1972) suggested to use liposomes as drug carrier systems. Nowadays liposomes are under extensive investigation for improving the delivery of therapeutic agents, enzymes, vaccines and genetic materials. Liposomes offer an excellent opportunity to selective targeting of drugs which is expected to optimize the pharmacokinetical parameters, the pharmacological effect and to reduce the toxicity of the encapsulated drugs. To understand the system it is important to know the basic properties of these lipoidal vesicles. Our aim was to focus on the lipid composition and the method of liposome preparation what determine the liposomal membrane fluidity, permeability, vesicle size, charge density, steric hindrance and stability of the liposomes as principle factors those influence the fate of liposomes, their interactions with the blood components and other tissues after systemic administration or local use.     

Preparation, properties and therapeutic effect of Daunorubicin-containing liposomes

Preparation and analytic characterization of uni- and multilamellar lipid vesicles with different lipid composition, charge and size, containing Daunorubicin are described. A critical review is given for the methods of preparation of lipids and other amphiphilic compounds. Variations of the lipid composition, charge and size of the liposomes do not alter the therapeutic effectiveness.     

Development of patient-friendly preparations(II): Preparation and characterization of carrageenan gel containing polyethylene (oxide)

The pharmaceutical utility of the allopurinol gel (APNgel) which consists of allopurinol (APN), carrageenan (kappa-CG or iota-CG) and polyethylene (oxide) (Alkox) was investigated as a possible material for an oral dosage preparation for ease in handling and/or swallowing. The gel formation was studied as a function of a variety of the concentration of Alkox and/or CG added. The APNgel gelled with kappa-CG was not appropriate to the oral dosage form because of its original taste and odor. In contrast, since iota-CG has no odor and/or taste, we added iota-CG as a gel material. From the investigation of the gelation behavior and the handling of the gelled material, the preferred composition of APNgel (Alkox: iota-CG% ratio) seemed to be that of 0.5:2.0, 1.0:2.0 and 2.0:2.0. The gel strength and the in vitro assessment of the adhesiveness of APNgels were evaluated using a creep meter. The gel strength of the APNgel was affected by the amount of the added Alkox. From the in vitro assessment of the adhesiveness of APNgels, the adhesiveness of APNgel increased with an increase in the amount of added Alkox. The release behavior of APN from APNgels was investigated by the paddle bead method, mimicking the chewing action in mouth. The APNgel was sheared by the beads and the release of APN completed within 480 s. From the results of the sensory test, APNgel consisting of 2.0% iota-CG and 1.0% Alkox seemed to be favorite to the jelly-like preparation.     

Preparation,characterization and in vitro efficacy of magnetic nanoliposomes containing the artemisinin and transferrin

Background

Artemisinin is the major sesquiterpene lactones in sweet wormwood (Artemisia annua L.), and its combination with transferrin exhibits versatile anti-cancer activities. Their non-selective targeting for cancer cells, however, limits their application. The aim of this study was to prepare the artemisinin and transferrin-loaded magnetic nanoliposomes in thermosensitive and non-thermosensitive forms and evaluate their antiproliferative activity against MCF-7 and MDA-MB-231 cells for better tumor-targeted therapy.

Methods

Artemisinin and transferrin-loaded magnetic nanoliposomes was prepared by extrusion method using various concentrations of lipids. These formulations were characterized for particle size, zeta potential, polydispersity index and shape morphology. The artemisinin and transferrin-loading efficiencies were determined using HPLC. The content of magnetic iron oxide in the nanoliposomes was analysed by spectrophotometry. The in vitro release of artemisinin, transferrin and magnetic iron oxide from vesicles was assessed by keeping of the nanoliposomes at 37°C for 12 h. The in vitro cytotoxicity of prepared nanoliposomes was investigated against MCF-7 and MDA-MB-231 cells using MTT assay.

Results

The entrapment efficiencies of artemisinin, transferrin and magnetic iron oxide in the non-thermosensitive nanoliposomes were 89.11% ± 0.23, 85.09% ± 0.31 and 78.10% ± 0.24, respectively. Moreover, the thermosensitive formulation showed a suitable condition for thermal drug release at 42°C and exhibited high antiproliferative activity against MCF-7 and MDA-MB-231 cells in the presence of a magnetic field.

Conclusions

Our results showed that the thermosensitive artemisinin and transferrin-loaded magnetic nanoliposomes would be an effective choice for tumor-targeted therapy, due to its suitable stability and high effectiveness.     

Preparation,characterization, photocytotoxicity assay of PLGA nanoparticles containing zinc (II) phthalocyanine for photodynamic therapy use

Nanoparticles containing Zinc (II) Phthalocyanine (ZnPc) were prepared by a spontaneous emulsification diffusion method utilizing poly-(D,L lactic-co-glycolic acid) (PLGA), characterized and available in cellular culture. The process yield and encapsulation efficiency were 60% and 80%, respectively. The nanoparticles have a mean diameter of 200?nm, a narrow size distribution with polydispersive index of 0.15, smooth surface and spherical shape. ZnPc loaded nanoparticles maintain their photophysical behaviour after the encapsulation process. Photosensitizer released from nanoparticles was sustained with a burst effect of 10% for 3 days. The photocytotoxicity was evaluated on P388-D1 cells. They were incubated with ZnPc loaded Np by 6?h and exposed to light (675?nm) for 120?s, and light dose of 30?J?cm^?2. After 24?h of incubation, the cellular viability was determined, obtaining 60% of cellular death. All the physical-chemical and photobiological measurements performed allowed one conclude that ZnPc loaded PLGA nanoparticles are a promising drug delivery system for PDT.     

Preparation, characterization, photocytotoxicity assay of PLGA nanoparticles containing zinc (II) phthalocyanine for photodynamic therapy use

Nanoparticles containing Zinc (II) Phthalocyanine (ZnPc) were prepared by a spontaneous emulsification diffusion method utilizing poly-(D,L lactic-co-glycolic acid) (PLGA), characterized and available in cellular culture. The process yield and encapsulation efficiency were 60% and 80%, respectively. The nanoparticles have a mean diameter of 200 nm, a narrow size distribution with polydispersive index of 0.15, smooth surface and spherical shape. ZnPc loaded nanoparticles maintain their photophysical behaviour after the encapsulation process. Photosensitizer released from nanoparticles was sustained with a burst effect of 10% for 3 days. The photocytotoxicity was evaluated on P388-D1 cells. They were incubated with ZnPc loaded Np by 6 h and exposed to light (675 nm) for 120 s, and light dose of 30 J cm-2. After 24 h of incubation, the cellular viability was determined, obtaining 60% of cellular death. All the physical-chemical and photobiological measurements performed allowed one conclude that ZnPc loaded PLGA nanoparticles are a promising drug delivery system for PDT.     

兰索拉唑脂质体的制备及性质考察

目的研究兰索拉唑阳离子脂质体的制备方法并考察其体外释放行为及稳定性等。方法采用正交设计筛选处方;采用乙醇注入法制备兰索拉唑脂质体;采用超滤法测定其包封率;采用透射电镜观察脂质体的外观形态;采用粒径分析仪和Zeta电位仪分别测定脂质体的粒径和Zeta电位;采用透析法考察脂质体的释放规律。结果制得的脂质体包封率约为(80±1.23)%(n=3);脂质体的形态为粒径均匀的球形和类球形;粒径为(184±21)nm(n=3),Zeta电位为(36.1±5)mV(n=3);脂质体的体外释放符合一级方程,具有较好的稳定性。结论优选得到的脂质体处方和制备工艺合理,制剂性质稳定,其体外释放具有缓释特点。     

氨溴索脂质体的制备及理化性质研究

目的制备氨溴索脂质体并考察其理化性质。方法采用硫酸铵梯度法制备氨溴索脂质体,在单因素考察基础上,采用正交试验设计优化脂质体的最佳处方和工艺;用透射电镜观察脂质体的外观形态,激光散射测定ξ电位和粒度分布,UV法测定脂质体的包封率,动态膜透析法探讨氨溴索脂质体体外释药特性。结果药物孵化时的形式、孵化温度、孵化时间是影响氨溴索脂质体包封率的主要的工艺因素,正交试验设计优化的最佳处方为磷脂与胆固醇之比8∶1、药脂比为1∶8、硫酸铵浓度为0.2 mol/L,最佳处方制备的脂质体为封闭的多层囊状或多层圆球体,大小均匀,平均粒径为7.189μm,ξ电位为+10.13 mv,包封率为80%,体外释放符合双向动力学方程(rα=0.998 1和rβ=0.992 3)。结论采用硫酸铵梯度法制备的氨溴索脂质体,包封率较高,体外释药有明显的缓释效果。     

多烯紫杉醇脂质体的制备及其性质考察

目的：制备多烯紫杉醇冻干脂质体并对其性质进行考察。方法：本实验采用改善的薄膜分散法制备了多烯紫杉醇脂质体并将其冻干制成多烯紫杉醇冻干粉，通过粒径测定、ζ电位的测定、包封率的测定、稳定性的考察等研究了多烯紫杉醇冻干脂质体的性质。结果：通过在脂质材料中加入聚山梨酯80可以较好地提高药物在其中的溶解能力，提高脂质体的载药量。采用蔗糖和甘露醇混合使用作为冻干保护剂可以使脂质体冻干粉具有较好的成形性和复溶能力。测得冻干前后多烯紫杉醇脂质体的包封率分别为98，6％和95．3％，粒径分别为136和152nm，ζ电位分别为一21．3和一20．8mV。脂质体在葡萄糖输液中6h内含量和粒径均无明显变化，而包封率有下降的趋势。结论：本实验所制得的多烯紫杉醇脂质体粒径分布范围窄，包封率较高，是很有应用前景的一种脂质体制剂。     

Development and characterization of multilamellar liposomes containing pyridostigmine

Abstract

Pyridostigmine has cardioprotective activity in both free and liposomal forms. This study aimed to develop and characterize liposomal formulations of pyridostigmine. For this, a spectrophotometric ultraviolet (UV) analytical method, at 270?nm, was developed and validated to quantify liposomal pyridostigmine. The method was linear in ranges from 0.02 to 0.09?mg/mL. The accuracy of this method was determined intra- and inter-day; the results of coefficient of variation were of 1.73–2.72% and 0.32–2.32%, respectively. The accuracy ranged between 99.45% and 101.12%. The method has not changed by influence of liposomal matrix and demonstrated being able to quantify pyridostigmine in liposomes. Two liposomal multilamellar formulations were developed: a constituted by dystearoyl-phosphatidylcholine (DSPC) and cholesterol (CHOL) other by dioleil-phosphatidylcholine (DOPC) and CHOL. The encapsulation efficiency was determined as 23.4% and 15.4%, respectively. Analyses of size and release of pyridostigmine from the formulations were made and the results showed that the formulations are viable for future studies in vivo.     

Preparation, characterization and biological evaluation of copper(II) and zinc(II) complexes with cephalexin.

Copper(II) and zinc(II) complexes of cephalexin have been prepared and characterized by microanalysis and by thermogravimetric, magnetic and spectroscopic analysis. The complexes were found to be five-coordinate, monohydrate, and ML2 type. The electron paramagnetic resonance spectral lines revealed rhombic distortion from axial symmetry, with g(parallel) > g(perpendicular) > g(e), in the elongated-tetragonal copper(II) complex. The geometry of the zinc(II) complex seems to be square-pyramidal. On complexation with copper and zinc the antimicrobial activity of cephalexin improved significantly. The copper complex was found to be active against kaolin paw oedema whereas the parent drug was inactive. These results suggest that the metallic elements should be seriously considered during drug design, and that complexes already reported should be subjected to clinical evaluation. Their use could provide an easy way of improving the activity and reducing the toxicity of drug substances.     

甘草酸二铵脂质体的制备及其性质的研究

目的:研究甘草酸二铵阳离子脂质体的制备方法和脂质体的性质。方法:采用均匀设计筛选最佳处方,逆相蒸发法制备甘草酸二铵脂质体;葡聚糖凝胶柱法测定其包封率;用透射电镜观察脂质体的外观形态,马尔文测定仪测定脂质体的粒径和Zeta电位;并用溶出度第3法考察了脂质体的释放规律。结果:制得脂质体的包封率约为(56±1．54)%(n=3);脂质体的形态为粒径均匀的球形或近球形,粒径为(183±9)nm(n=3),Zeta电位为(22．8±6)mV(n=3);脂质体的体外释药符合Higuchi方程;具有较好的稳定性。结论:采用逆相蒸发法,添加十八胺可制得具有较高包封率及稳定性的甘草酸二铵阳离子脂质体,制得脂质体的体外释放具有缓释特点。