重酒石酸长春瑞滨脂质体包封率测定方法比较

目的制备重酒石酸长春瑞滨脂质体,比较葡聚糖凝胶微柱离心法和阳离子交换树脂离心法测定重酒石酸长春瑞滨脂质体包封率的差异。方法pH梯度法制备重酒石酸长春瑞滨脂质体,分别以葡聚糖凝胶Sephadex G-50和阳离子交换树脂装柱,离心分离脂质体和游离药物,采用HPLC法测定药物含量,计算包封率,并用SPSS软件进行t检验。结果两种方法测定不同载药量的脂质体包封率结果均无显著性差异(P>0.05)。结论葡聚糖凝胶微柱离心法和阳离子交换树脂离心法均可用来测定重酒石酸长春瑞滨脂质体包封率,优选阳离子交换树脂离心法。     

pH梯度法制备阿霉素脂质体

采用ｐＨ梯度法制备了阿霉素脂质体．用ＳｅｐｈａｄｅｘＧ－２５微型柱分离－紫外分光光度法测定阿霉素脂质体包封率．结果表明，当药物／磷脂重量比为０．０２～０．０５时，包封率均大于９０％；体外泄漏研究显示，２５℃时，２ｈ内泄漏百分率约为２．７％，保证了临床应用．     

Liposomal Formulation of a Cytokine Restraining Agent, (CRA)-HP 228: Encapsulation, Stability, and Release Characteristics

Cytokine restraining agents (CRAs) are a family of compounds having profound anti-inflammatory properties. Among them, HP 228 is a heptapeptide, containing some unnatural amino acids, with the unique ability to restrain the pathological effects of cytokines without interfering with their essential immune functions. A liposomal formulation of HP 228 was developed to protect the drug from proteolytic enzymes and to provide controlled release of the drug. The liposomes were prepared using either dimyristoyl phosphatidylcholine or dipalmitoyl phosphatidylcholine and cholesterol by the thin-film hydration method. Dicetyl phosphate was added to the lipids to provide negative charge to the liposomes. Homogeneous size distribution of multilamellar vesicles (MLVs) was achieved by extruding them through the 800-nm polycarbonate membranes. The size distribution was characterized using a submicrometer particle size analyzer. Encapsulation efficiency of HP 228 was determined by adding protamine to MLVs and separating the supernatant from the liposome protamine aggregate. Enzymatic stability of the drug was evaluated in phosphate-buffered saline, pH 7.0 and 37°C. The studies were conducted in the presence of trypsin and chymotrypsin. The encapsulation of HP 228 increased with the increase in fatty acid chain length. Encapsulation was further increased in negatively charged liposomes compared with neutral liposomes. The encapsulation efficiency was over 50%. Also, the negative charge helped in preventing the aggregation of the liposomes and promoted the electrostatic interaction between the lipid and the drug. Encapsulating the drug in the aqueous compartment of the liposomes completely protected HP 228 from trypsin and chymotrypsin. The rate of release of HP 228 was measured using a side-by-side diffusion chamber and was found to be drastically lower from the liposomes, as compared with the drug solution, making the formulation suitable for controlled release of HP 228.     

微柱离心结合双波长考马斯亮蓝法/酶标仪法测定牛血清白蛋白脂质体的包封率

目的:测定牛血清白蛋白(BSA)脂质体的包封率。方法:采用微柱离心结合双波长考马斯亮蓝法/酶标仪法测定,即先用葡聚糖凝胶DEAE-Sephadex A50微柱离心法将游离药物与脂质体进行分离,再筛选样品与染料体积比及反应时间,确定了双波长(595、450nm)考马斯亮蓝法/酶标仪法的测定条件并进行了方法学考察;考察了微柱对空白脂质体的回收率和微柱的分离效率;对BSA脂质体的包封率进行了测定。结果:确定的测定条件为样品与染料体积比为1∶3、反应时间10min,该法平均回收率为99.56%,RSD小于2.73%;微柱对空白脂质体的平均回收率为97.78%,分离效率大于90%;BSA脂质体的平均包封率为32.91%(n=3)。结论:本法实现了游离蛋白质与脂质体快速有效的分离,方法简单易行,与普通凝胶层析柱分离法相比,本法对样品的稀释倍率大大降低,适用于测定痕量大分子蛋白质脂质体的包封率。     

Development and Characterization of a Liposome Preparation by a pH-Gradient Method

Abstract— A pH gradient across liposome bilayers was established in order to load a model drug (orciprenaline sulphate) into liposome vesicles. This method of liposome loading resulted in yields as high as 80–85% encapsulation. An eight-step process was designed to scale-up the process and was evaluated. In this process a diafiltration technique was successfully used to remove the excess orciprenaline sulphate present in the external medium. Finally, drug-loaded liposomes were lyophilized using lactose as an internal and external liposomal cryoprotectant. Five-month stability data for the liposomes is reported. An HPLC technique was used to determine the drug concentration and a laser light-scattering technique was employed to determine the liposome vesicle size and polydispersity factor. Liposomes prepared by the pH-gradient method showed high encapsulation efficiency. Upon storage at 2–8°C the vesicle size increased and encapsulation efficiency decreased with time. These phenomena are attributed to gradual fusion of liposomes and loss of drug to the extra-liposomal media.     

西罗莫司脂质体的制备及处方因素考察

目的 制备西罗莫司脂质体并对处方进行筛选,以期得到高包封率的脂质体制剂.方法 选用乙醇注入法制备西罗莫司脂质体,微柱离心-HPLC法测定包封率,以包封率为评价指标,考察磷脂浓度、磷脂胆固醇质量比、药脂比、水相介质pH等因素对脂质体的影响,在此基础上运用正交设计对处方进行优化.结果 正交试验结果表明磷脂浓度为4%,磷脂与胆固醇质量比例为8:1,药物磷脂质量比为1:20,水相pH为7.4为最佳处方,制得的脂质体包封率为(82.11±2.13)%.结论 优选出最佳处方,制得的西罗莫司脂质体包封率高,重现性好.     

鱼精蛋白凝聚法测定和厚朴酚脂质体的包封率

目的:建立和厚朴酚脂质体包封率(EE)的测定方法。方法:以反相高效液相色谱法为分析手段,采用鱼精蛋白凝聚法测定和厚朴酚脂质体EE。结果:和厚朴酚检测浓度在2.006～160.512mg·L-1范围内与峰面积积分值呈良好的线性关系(r=0.9999),最低检测限和最低定量限分别为1.4、4.0ng;鱼精蛋白凝聚法的平均回收率为(95.70±2.07)%,RSD=1.71%(n=9);平均EE为85.87%。结论:鱼精蛋白凝聚法操作简单、可行、重现性好,适用于脂溶性药物和厚朴酚脂质体EE的测定。     

Pilocarpine hydrochloride liposomes: characterization in vitro and preliminary evaluation in vivo in rabbit eye

Liposomes containing either pilocarpine hydrochloride or pilocarpine free base were prepared by the sonication method. This manufacturing process yielded after removal of non-encapsulated solute, small multilamellar vesicles (MLV) as was confirmed by electron microscopy examinations. For an identical liposomal composition, the encapsulation capacity and the drug content of the liposomes were drastically higher for pilocarpine hydrochloride than for pilocarpine free base. Investigation of the preparative parameters revealed that increasing the initial amount of drug decreased the drug content and the encapsulation efficiency of the liposomes formed. Since fixed amounts of lipids were used, the volume sequestration rate decrease was attributed to a moderate viscosity increase of the dispersion medium. Increase of phospholipid concentration at a constant ratio of cholesterol and dicetylphosphate to phosphatidylcholine reduced the aqueous volume entrapped per mg of lipid and subsequently the pilocarpine content in the liposomes. Negatively charged liposomes gave larger rates of pilocarpine hydrochloride and aqueous volume encapsulation than neutral liposomes but, on the contrary, positively charged liposomes gave the lowest rates of pilocarpine hydrochloride and aqueous volume encapsulation. Thus, for drug carrying the same net charge as the phospholipids an increase in the surface charge density of the liposome was not only ineffective, but actually resulted in a lower drug encapsulation due to electrostatic repulsion. Preliminary in vivo results on rabbit eyes suggested that the liposomal vehicle was probably unable to improve sufficiently the corneal penetration of pilocarpine to reach satisfactory therapeutic levels when administered at lower concentrations than commonly used.     

盐酸伊立替康脂质体的制备

目的结合脂质体这种新型给药载体的特征将盐酸伊利替康(Irinotecan,OPT-11)制备成脂质体以解决喜树碱类药物在生理条件下其结果中的内酯环易发生水解反应转变为羟酸盐形式,从而失去活性这个难问题.方法以包封率为主要评价指标,比较了传统的脂质体制备方法(薄膜分散法、乙醇注入法、反向蒸发法等)与主动载药方法-硫酸铵梯度法对伊立替康脂质体制备的影响.结果采用硫酸铵梯度法制备伊立替康脂质体可以获得较高的包封率、较大的药酯比.结论硫酸铵溶液的浓度、孵育时间和温度空白脂质体的粒径大小等是影响伊立替康脂质体包封率的主要因素.     

微柱离心-药脂比测定脂质体药物包封率

目的建立一种准确测定脂质体包封率的方法。方法以氟吡洛芬、酮洛芬、拓扑替康为模型药物脂质体,通过葡聚糖凝胶(Sephadex G-50)微柱离心去除游离药物,以HPLC法测定药物含量,以定磷法测定磷脂含量,通过药脂比测定药物包封率。结果无需将脂质体完全洗脱,通过检测洗脱脂质体中的药脂比能够准确测定脂质体包封率;对于水溶性药物拓扑替康,若将脂质体完全洗脱,则可能无法将游离药物完全分离。结论在一定条件下微柱离心去除游离药物,通过药脂比测定包封率方便准确。     

正交试验优选硫酸铵梯度法制备苦参碱脂质体的工艺研究

目的 以包封率为指标优选苦参碱脂质体的制备工艺.方法 以氢化大豆卵磷脂(HSPC)和胆固醇(Ch)为膜材,采用薄膜超声-硫酸铵梯度法制备脂质体.通过正交设计优化处方工艺,葡聚糖凝胶法分离游离药物,HPLC法测定月旨质体中苦参碱的包封率.结果 最佳工艺为:HSPC:Ch=3∶1,探头超声10 min,药脂比为1:15,包封率均值为50.68％.结论 优化后的工艺可提高苦参碱脂质体的包封率,此工艺条件简单,可操作性强,适于实验室条件下制备苦参碱脂质体.     

高乌甲素脂质体凝胶制备工艺及体外释药性能研究

目的：制备高乌甲素脂质体（LA-LIP）经皮给药制剂，对其质量及透皮吸收性质进行考察。方法：采用薄膜分散法制备LA-LIP，以包封率与载药量为指标，运用正交试验法确定LA-LIP的优选处方；以卡波姆-940为基质制备LA-LIP凝胶，采用体外释放试验评估释放能力。结果：正交试验法确定LA-LIP最佳处方工艺组合为卵磷脂与胆固醇质量比为8：1、药脂比为1：8、水化温度为55℃。体外透析袋实验显示，LA-LIP凝胶慢释过程符合Higuchi方程，LA凝胶释放过程符合零级动力学方程；体外透皮结果显示，LA凝胶24 h内皮肤滞留量为8.39 μg·cm^-2，LA-LIP凝胶皮肤滞留量为15.17 μg·cm^-2。结论：本研究发现运用薄膜分散法制备LA-LIP工艺简单可靠，制备成脂质体凝胶剂时，具有缓释效果。     

头孢菌素类抗生素脂质体的包封率测定与渗漏研究

使用注射法和可控组装法制备了第三代头孢菌素类抗生素头孢曲松钠及头孢噻肟钠脂质体。平衡透析和微型柱－离心两种方法分离脂质体内外相中头孢菌素类抗生素,均具有良好的分离效果,且能得到较为相似的结果。建立的可控组装一紫外法可简便、准确地考察只具有紫外特性药物脂质体的效能。对它们的渗漏研究发现药物只能由脂质体内向外微量渗漏,而不被脂质体所摄取。     

Liposomes from hydrogenated soya lecithin formed in sintered glass pores

Possible complete closure of hydrophilic drug solutions in liposomes with required dimensions is the aim of variety liposome techniques. The ease of separating medication-loaded liposomes from liposome suspension to achieve an appropriate drug concentration in the final preparation is also desired. This paper describes the use of liposome preparation method, called reverse-phase evaporation, which leads to practical achievement of the earlier mentioned objectives. Preparation process is performed in an appropriately designed device. In optimal conditions of liposome preparation the final encapsulation efficiency of hydrophilic drug solution amounted to 50% in liposomes with a diameter in the range of a few micrometers up to 250 nm. The diameter of terminal liposomes is a simple function of relative amount of the lipid used and the degree of emulsion emulsification w/o at the beginning of liposome preparation. The density of the concentrated drug solution trapped in liposomes is usually higher than that of the buffer. Therefore, the loaded liposomes may be easily separated from non-trapped material by using of a simple sedimentation at 30000 x g. Density of aqueous drug solution insufficient to effective centrifugation can be magnified with an appropriate quantity of sucrose solution before encapsulation.     

Liposomal diclofenac eye drop formulations targeting the retina: Formulation stability improvement using surface modification of liposomes

An efficient liposomal formulation for targeting the retina was produced as an optimal means of distributing therapeutic agents to the retina. Diclofenac was used as a model compound for liposome encapsulation, and the release rate and distribution to the retina were investigated. The calcium acetate gradient method was found to be the optimal method for encapsulating diclofenac into liposomes. Entrapment efficiency using this method was greater than 97%, whereas conventional hydration method achieved 51.3%. The resultant formulation obtained with the gradient method caused aggregation and/or fusion of liposomes. To avoid inhibition of retinal delivery due to the aggregation of the carrier, surface modification was performed simultaneously with the gradient method. The increase in particle size of the liposomal formulation clearly was inhibited for a long time in the presence of polyvinyl alcohol or its derivative. This observation may be explained by surface modification of the liposomes by physisorption or anchoring effect of polymers on the surface of the lipid bilayer. Furthermore, the sustained release profile of the diclofenac formulation was retained after modification. An in vivo animal study revealed that concentration of the accumulated diclofenac in the retina-choroid was enhanced 1.8-fold by surface-modified liposome entrapment compared to that of the unaltered diclofenac solution.     

Effect of surface ligand density on cytotoxicity and pharmacokinetic profile of docetaxel loaded liposomes

Various biotin-modified liposomes incorporated with docetaxel (DTX) were prepared to study the effect of surface biotin density on the pharmacokinetic profile of the liposome. Four types of liposomes such as PEG modified liposome (PDL), 0.5% (mol) biotin modified liposome (0.5BDL), 1% (mol) biotin modified liposome (1BDL) and 2% (mol) biotin modified liposome (2BDL) were prepared using thin film dispersion method. The prepared liposomes were characterized by measuring encapsulation efficiency (EE), particle size, Zeta-potential, physical stability and drug release profiles in vitro. MTT assay was performed to elevate the cytotoxicity of liposomes on MCF-7 cells. In vivo evaluation was further performed to investigate the effect of biotin surface density on the pharmacokinetic profiles. All the prepared liposomes exhibited high encapsulation efficiency, small particle size, narrow particle distribution and sustained release profiles in vitro. In MTT assay, 0.5BDL showed largest tumor cell toxicity, compared with DTX solution. All liposomes containing DTX showed prolonged blood circulation in vivo, and 0.5BDL showed the longest circulation time among the biotin modified liposome. Surface modification of liposome had a negative impact on the circulation of liposomes in the blood, which needs to be considered when designing the ligand mediated targeting delivery systems. A proper amount of biotin liposome with 0.5% molar ratio is expected to produce the best anti-tumor effect.     

海参皂苷nobiliside A脂质体及其溶血行为的初步研究

本文旨在制备海参皂苷nobiliside A(Nob A)脂质体，建立脂质体中Nob A的含量和包封率的测定方法，考察该脂质体的体内外溶血行为。以高效液相色谱-蒸发光散射检测法(HPLC-ELSD)测定脂质体中Nob A含量，微柱离心法测定其包封率。以溶血率和包封率、粒径为指标，单因素考察了制备方法、磷脂用量、胆固醇用量和药脂比。根据单因素的考察结果，以薄膜超声法制备3批脂质体，与同浓度的药物溶液进行体内外溶血行为的比较。结果显示：用于含量测定和包封率测定的HPLC-ELSD和微柱离心法准确、快速，采用薄膜超声法制备的脂质体形态圆整，粒径较为均匀。当磷脂与胆固醇比例为2∶1，药脂比为1∶40时，Nob A脂质体的平均包封率为95.7%，平均粒径为87.6 nm。Nob A以脂质体作为给药载体，其体内外溶血行为大大降低，有望成为静脉注射用脂质体。     

主动载药法制备硫酸卷曲霉素脂质体及其质量评价

目的制备硫酸卷曲霉素脂质体,建立含量和包封率的测定方法,初步考察其体外释放规律。方法采用pH梯度法制备硫酸卷曲霉素脂质体,超滤法分离脂质体与游离药物,RP-HPLC测定脂质体的含量和包封率,透析法考察脂质体的体外释放行为。结果超滤法能很好地将脂质体与游离药物分离,测定硫酸卷曲霉素脂质体的含量为10.27mg/ml,包封率为47.8%,脂质体的体外释放规律符合一级动力学过程。结论pH梯度法适于制备硫酸卷曲霉素脂质体,超滤法可用于硫酸卷曲霉素脂质体包封率的测定,制备的脂质体具有一定的缓释效果。     

奥沙利铂长循环热敏脂质体及其药效学研究

目的制备奥沙利铂长循环热敏脂质体(oxaliplatinlong-circulating-thermosensitive liposomes,OLTL),并考察其性质及抑瘤作用。方法采用薄膜分散法制备OLTL;透析法考察OLTL在37℃和42℃下的体外释药;免疫抑制法建立荷Lewis肺癌小鼠模型,以瘤重为指标考察OLTL的抑瘤作用。结果带有蓝色乳光的OLTL粒径在100～130 nm之间,包封率大于90%;42℃条件下,OLTL释药率达90%以上;OLTL组抑瘤率为70.79%。结论 OLTL具有良好的热敏释药特性,可明显提高奥沙利铂(oxaliplatin)的抑瘤作用。     

Encapsulation,Stability and In-vitro Release Characteristics of Liposomal Formulations of Colchicine

The severe toxicity and low therapeutic index of colchicine limit its therapeutic use. Encapsulation in liposomes might reduce these toxic effects. The objective of this study was to determine the factors influencing encapsulation of colchicine in liposomes and to optimize the encapsulation parameters. Colchicine was encapsulated in multilamellar liposomes and large unilamellar liposomes prepared using various phospholipids. The effects of method of preparation, type of vesicle, charge, and concentration of cholesterol on encapsulation of colchicine in liposomes were investigated. Also, stability of colchicine under stress conditions and at various temperatures, and in-vitro release characteristics were determined. A significant difference in encapsulation of colchicine in multilamellar liposomes was observed when prepared by two different methods. Induction of charge on the liposome surface increased encapsulation of colchicine in multilamellar liposomes, but did not affect large unilamellar liposomes. The liposome preparations could withstand simulated transport conditions and frequent changes in temperature. Particle size and concentration of colchicine did not change significantly during storage at various temperatures for six months. In order to retain encapsulated colchicine in liposomes, storage at or below room temperature was found to be suitable. In-vitro release of colchicine from large unilamellar liposomes was biphasic and was influenced by two rate-limiting barriers, the dialysis membrane and the liposome bi-layers. For optimum encapsulation and stability of colchicine liposomes were prepared from a mixture of 1,2-distearoyl-sn-glycero-3-phosphocholine, cholesterol and either stearylamine or dicetyl phosphate.