聚(2-乙基丙烯酸)脂质体的制体及其热敏性研究

采用插入法以脂肪酰胺修饰的聚(2-乙基丙烯酸)衍生物构建热敏递药的高分子脂质体.用荧光分析法,借助荧光分光光度仪和粒径仪系统地研究了高分子脂质体的热敏特性.结果发现,采用脂肪胺修饰的聚(2-乙基丙烯酸)制备的脂质体具有明显的热敏释药特性,其释药特性与插入的高分子结构有关,还与制备脂质体的磷脂组成有关,同时采用聚(2-乙基丙烯酸)制备的脂质体还具有显著的酸敏释药特性.以聚(2-乙基丙烯酸)为热敏诱导介质制备的脂质体在体外实验中呈现出良好的热敏释药特性,且制剂制备方法简便、可靠.     

聚(2-乙基丙烯酸)脂质体的制体及其热敏性研究

采用插入法以脂肪酰胺修饰的聚(2-乙基丙烯酸)衍生物构建热敏递药的高分子脂质体。用荧光分析法，借助荧光分光光度仪和粒径仪系统地研究了高分子脂质体的热敏特性。结果发现，采用脂肪胺修饰的聚(2-乙基丙烯酸)制备的脂质体具有明显的热敏释药特性，其释药特性与插入的高分子结构有关，还与制备脂质体的磷脂组成有关，同时采用聚(2-乙基丙烯酸)制备的脂质体还具有显著的酸敏释药特性。以聚(2-乙基丙烯酸)为热敏诱导介质制备的脂质体在体外实验中呈现出良好的热敏释药特性，且制剂制备方法简便、可靠。     

荧光素作为酸敏指示剂评价酸敏材料和脂质体酸敏性的方法研究

目的:建立一种简单而快速的评价酸敏材料和脂质体酸敏性的实验分析方法。方法:利用脂质体包裹的荧光素在高浓度环境的自屏蔽作用,以及从脂质体中释放后自屏蔽消失的特性,通过检测试样的荧光发射光信号,来评价酸敏物质诱发细胞膜融合通透性能的强弱和脂质体的酸敏释药性能。结果:选用不同磷脂组分制备的脂质体可以成功的包裹高浓度荧光素,被包裹的荧光素稳定并且能屏蔽自己的发射光;在酸性条件,酸敏物质破坏脂质体膜,荧光素可以从脂质体中释放出来。酸敏材料的酸敏能力、溶液酸度、脂质体磷脂组成都影响荧光素从脂质体中释放的能力和速度;酸度影响荧光素的荧光强度,但在 pH 6.5～10.0不受影响。结论:利用脂质体包裹高浓度荧光素的自我屏蔽性,建立一种简单而快速的实验方法,用来评价酸敏物质诱发细胞膜融合通透性能的强弱以及评价脂质体的酸敏释药性能。     

聚(2-乙基丙烯酸)脂肪酰胺衍生物构建的酸敏脂质体

本实验合成了系列聚(2-乙基丙烯酸)长链脂肪酰胺衍生物，并采用高分子插入法制备了聚(2-乙基丙烯酸)酸敏高分子脂质体。应用荧光指示剂、粒径仪、荧光显微镜及细胞实验，系统研究了高分子修饰和脂肪胺的链长对高分子衍生物嵌入脂质体的效率和质量的影响。结果表明，高分子插入法可以制备聚(2-乙基丙烯酸)酸敏高分子脂质体。(1) 高分子嵌入量与高分子脂肪胺的链长无关，但与高分子修饰度相关。(2) 高分子嵌入量与起始的高分子-脂质体比例成正比。(3) 在酸性条件下聚(2-乙基丙烯酸)脂质体可产生显著的脂质体融合及释药行为。(4) 聚(2-乙基丙烯酸)脂质体在细胞内呈现出良好的酸敏诱导释药特性。实验证明这种方法制备的脂质体具有良好的酸敏释药性能，并且制备方法简便，可控性好，实用性强。     

酸敏高分子诱导的脂质体膜融合性能研究

本文研究了具有酸敏特性的高分子聚(2-乙基丙烯酸)诱导的脂质体-脂质体及脂质体-细胞膜之间的融合特性。采用脂肪胺修饰的聚(2-乙基丙烯酸)制备酸敏高分子脂质体。用荧光共振能量转移法定量测定脂质体间的融合程度，采用粒径仪研究脂质体在发生膜融合时的粒径变化。结果显示，聚(2-乙基丙烯酸)酸敏高分子脂质体有很强的酸敏融合性能。在酸性条件下高分子酸敏脂质体之间可以相互融合，其程度与脂质体表面酸敏高分子聚(2-乙基丙烯酸)的分子质量成正比；高分子酸敏脂质体的酸敏融合性与构成其磷脂膜的磷脂种类有关，另外脂质体膜中加入胆固醇可降低高分子酸敏脂质体的膜融合性能；高分子酸敏脂质体与血红细胞膜影融合；酸敏高分子诱导的脂质体融合会引起脂质体膜通透性的增加。聚(2-乙基丙烯酸)诱导的酸敏高分子脂质体的膜融合特性说明其可用于制备酸敏控释脂质体。     

沙美特罗和布地奈德的脂质体/水分配系数测定及影响因素考察

目的测定沙美特罗和布地奈德的脂质体/水分配系数(P_L/w)，考察影响两种药物P_L/w的因素，揭示药物与磷脂双分子层的作用机制。方法用平衡透析法测定两种药物在不同脂质体组成和不同介质中的P_L/w。结果两种药物P_L/w随脂质体中胆固醇含量及磷脂饱和程度增加而减小；脂质体表面负电荷、介质pH值及离子强度增加，沙美特罗的P_L/w增加。脂质体表面电荷、介质pH值及离子强度对布地奈德的P_L/w影响较小。结论药物P_L/w受药物性质、脂质体磷脂种类、饱和程度、胆固醇含量和表面电荷以及介质pH和离子强度等因素影响，在测定时应选择与生物膜环境相近的P_L/w测定条件，以反映药物在生物膜中的分配。     

顺铂缓释多囊脂质体的制备和体外释放性能研究

目的 制备包封率高和缓释作用好的顺铂缓释多囊脂质体,并与反相蒸发法制备的顺铂普通脂质体比较其体外释药性能。方法 用复乳法制备顺铂多囊脂质体,非火焰原子吸收分光光度法测定顺铂含量,磷脂酶试剂法测定脂质体中磷脂的浓度。测定包封率和体外释药性。结果顺铂多囊脂质体平均粒径为16.6 μm,跨距为1.0。顺铂包封率可高达80%以上。顺铂缓释多囊脂质体的体外释药符合一级释药规律, 释药t_1/2为37.7 h,比反相蒸发法制备的顺铂普通脂质体延长8.4倍。经差示热分析发现辅助膜稳定剂有明显的膜稳定作用。结论顺铂多囊脂质体包封率高,并具有良好的缓释作用。     

荧光偏振法用于止血剂与脂质体及血液红细胞主-客体分子间作用机制的研究

以磷脂脂质体模拟血液细胞,用1,6-二苯基已三烯(DPH)为荧光探针,荧光偏振法研究了安络血、止血芳酸、维生素K₁和6-氨基已酸4种止血剂作为客体分子与脂质体及血液红细胞两类主体分子互相作用而形成的超分子化合物。利用偏振度(P)与微粘度(η)的定量关系,计算微粘度的变化,并以微粘度的变化推测止血剂与红细胞的作用机制。结果表明,止血剂与脂质体或血红细胞的相互作用力主要是超分子作用力。不同血凝机制的止血剂与红细胞作用方式也不尽相同。本文还对止血剂与红细胞的结合方式进行了探讨。     

乳糖化-去甲斑蝥素磷脂复合物及其pH敏感型脂质体的制备

目的:合成乳糖化-去甲斑蝥素磷脂复合物,并制备其pH敏感型脂质体。方法:将乳糖化-去甲斑蝥素与磷脂聚合成药物磷脂复合物,并采用FT-IR、DSC和1H-NMR对其进行表征。逆向蒸发法制备药物磷脂复合物脂质体;利用羧甲基壳聚糖与脂质体表面的静电吸附作用,使羧甲基壳聚糖吸附在脂质体表面,制备乳糖化-去甲斑蝥素磷脂复合物pH敏感型脂质体;考察了药物与磷脂的复合率,磷脂复合物脂质体的包封率,粒径大小和分布,以及体外释药特性。结果:药物磷脂复合率为(97.2±2.01)%,磷脂复合物脂质体的平均包封率为(70.00±1.30)%,平均粒径为(47.18±4.16)nm,粒径跨距为(0.70±0.07),电镜显示其形态圆整,体外释药符合Weibull方程。结论:乳糖化-去甲斑蝥素磷脂复合率高,制成的pH敏感型脂质体性质稳定,且具有缓释特性。     

PEG-I-dC16酸敏释药胶束的制备及体外释放研究

目的:构建酸敏释药胶束并考查其酸敏释药特性。方法:用亚胺键连接PEG和苯棕榈酸脂肪链,用透析法制备载阿霉素胶束,对其粒径,载药量和包封率进行考察,用紫外分光光度法测定载药胶束在不同pH值条件下的释放。结果:载药胶束粒径为60~70 nm,PEG相对分子质量为2000 Da的胶束载药量和包封率分别为(12.7±1.1)%和(49.8±2.2)%,PEG相对分子质量为5000 Da的胶束载药量和包封率分别为(10.7±0.3)%和(39.9±2.1)%。体外释放研究表明酸敏释药胶束在pH 6.5时的累积释放率比pH 7.4时大,但在pH 5.0条件下其累积释放较pH 7.4时还要小,可能原因是胶束解聚太快致药物与材料形成复合物沉淀所致。结论:以酸敏感亚胺键连接的两亲材料载药胶束具有一定的酸敏释药特性。     

非特异靶向荷正电高分子磷脂脂质体的构建和体外评价

采用一种新设计的末端带有枝状结构寡赖氨酸聚乙二醇高分子磷脂为主要功能性辅料, 依照常规薄膜-水合和后续高分子插入两种方法制备了系列外表面带正电荷的高分子脂质体。激光衍射粒径仪研究证明, 常规脂质体制备方法和后续高分子插入都可以制备纳米、粒径均匀、外表面携带不同密度正电荷的高分子磷脂脂质体, 正电荷密度不同并不影响脂质体的粒径和分布。后续高分子插入过程不影响脂质体的载药工艺, 不干扰脂质体的载药量, 不引起脂质体的形态和粒径变化, 也不诱发脂质体内部包裹的药物早期泄漏。体外细胞学实验证明这种荷正电高分子脂质体局部电荷密度高, 对细胞有显著非特异性靶向作用。     

Colloidal phase behavior of pH-responsive, amphiphilic PEGylated poly(carboxylic acid)s and effect on kinetic solubility under acidic conditions

PEGylated poly(carboxylic acid)s, PEG-b-PCAs, were evaluated as additives for solubilized oral formulations of weakly acidic compounds. Micelles of poly(ethylene glycol)-block-poly(acrylic acid), PEG-b-PAA, and poly(ethylene glycol)-block-poly(methacrylic acid), PEG-b-PMAA, were prepared. Fluorescence spectroscopy and dynamic light scattering revealed that both polymers assemble into nanoscopic structures (< 200?nm) in acidic media and exhibit pH-sensitive colloidal phase behavior. Using a solvent evaporation technique, the block copolymers and corresponding PCA homopolymers were incorporated into PEG3350-based solid dispersions. The kinetic solubility profile of a BMS compound, BMS-A (Seq ~ 12.5?μg/mL at pH 1.1) in 0.1 N HCl was monitored as a function of polymer composition. While BMS-A precipitated rapidly in 0.1 N HCl in the absence of PEG-b-PCAs, a supersaturated level of ca. 400 μg/mL was maintained for variable lengths of time in the presence of PEG-b-PCAs. Although the kinetic solubility of BMS-A was also enhanced in the presence of the PCA homopolymers, the relative magnitude and duration of supersaturation as a function of polymer composition suggests that micellar solubilization, rather than specific interaction, contributes to enhanced solubility of BMS-A in 0.1 N HCl. Under acidic conditions, pH-responsive PEG-b-PCAs may offer the kinetic supersaturation necessary to minimize precipitation of compounds which have limited solubility in acidic milieu.     

Prolonged systemic delivery of streptokinase using liposome

To prolong the biological half-life of streptokinase, a thrombolytic agent, streptokinase-bearing liposome with and distearolyphosphatidyl ethanolamine-N-poly (ethylene glycol) 2000 (DSPE-PEG 2000) was prepared and evaluated. Streptokinase-bearing liposomes composed of distearolyphosphatidylcholine (DSPC), cholesterol and cholesterol-3-sulfate with DSPE-PEG 2000 was prepared by the freeze-thawing method and administered via femoral vein to rats (15000 IU/kg). The activity of streptokinase in plasma was determined by the method based on the amidolytic activity of streptokinase-plasminogen complex. Pharmacokinetic parameters on streptokinase incorporated in liposomes were compared with those of streptokinase alone. The T_1/2 and AUC_∞ of streptokinase incorporated in DSPC-PEG liposome increased 16.3- and 6.1-fold, respectively, compared with those of streptokinase alone. Streptokinase-bearing long-circulating liposome could increase the circulation time of streptokinase in blood and expect longer thrombolytic activity compared with streptokinase alone.     

Acidic Microclimate pH Distribution in PLGA Microspheres Monitored by Confocal Laser Scanning Microscopy

PURPOSE: The acidic microclimate pH (micropH) distribution inside poly(lactic-co-glycolic acid) (PLGA) microspheres was monitored quantitatively as a function of several formulation variables. METHODS: A ratiometric method by confocal laser scanning microscopy with Lysosensor yellow/blue dextran was adapted from those previously reported, and micropH distribution kinetics inside microspheres was examined during incubation under physiologic conditions for 4 weeks. Effects of PLGA molecular weight (MW) and lactic/glycolic acid ratio, microspheres size and preparation method, and polymer blending with poly(ethylene glycol) (PEG) were evaluated. RESULTS: micropH kinetics was accurately sensed over a broadly acidic range (2.8 < micropH < 5.8) and was more acidic and variable inside PLGA with lower MW and lactic/glycolic acid ratio. Lower micropH was found in larger microspheres of lower MW polymers, but size effects for lactic-rich polymers were insignificant during 4 weeks. Microspheres prepared by the oil-in-oil emulsion method were less acidic than those prepared by double emulsion, and blending PLGA 50/50 with 20% PEG increased micropH significantly (micropH > 5 throughout incubation). CONCLUSIONS: Coupling this method with that previously developed (SNARF-1 dextran for micropH 5.8-8.0) should provide microclimate pH mapping over the entire useful pH range (2.8-8.0) for optimization of PLGA delivery of pH-sensitive bioactive substances.     

修饰脂质体的可断裂聚乙二醇脂质衍生物的研究进展

聚乙二醇脂质衍生物可增加脂质体的稳定性，延长其体内循环时间。传统的长循环材料由于连接聚乙二醇与脂质的化学键太稳定，导致脂质体内容物释放延迟而影响药效。近年来提出可断裂聚乙二醇脂质衍生物的概念，该类衍生物具有可以在人的生理或病理条件下断裂的性质，能够延长脂质体体内循环时间，在到达靶部位后由于聚乙二醇已经从脂质体表面脱落，脂质体可以与病变细胞结合，从而将药物送入细胞。本文综述了可断裂聚乙二醇脂质衍生物的种类、断裂类型、在脂质体中的应用概况及在应用中的优势和局限。     

N-terminal specificity of PEGylation of human bone morphogenetic protein-2 at acidic pH

Site-specific PEGylation offers the possibility to modify a therapeutic protein without interfering with its biological activity. Previously, a preferential N-terminal PEGylation has been reported for several proteins when the reaction was performed at acidic pH. In the present study it was explored if acidic pH favors N-terminal PEGylation of bone morphogenetic protein-2 (BMP-2). PEGylation by poly(ethylene glycol) aldehyde (PEG-AL) or poly(ethylene glycol) carboxymethyl succinimidyl ester (PEG-NHS) was performed at moderate acidic pH of 4. Comparing with PEG-NHS, PEG-AL converted more BMP-2 mainly to mono- or di-PEGylated derivatives at much less molar excess and shorter duration. Analysis of Tryptic fragments of the PEGylated derivatives indicated a partial N-terminal PEGylation specificity. PEG-AL exhibited higher specificity than PEG-NHS. UV spectrometry proved that PEGylation improved the solubility of BMP-2 in PBS. Surface plasmon resonance showed that PEGylation decreased the binding of BMP-2 proteins to a type II receptor. Remarkably, mono-PEGylated BMP-2 with PEG-AL showed higher cellular bioactivity than unmodified protein. Higher N-terminal PEGylation specificity correlates with higher receptor binding affinity and cellular activity. In summary, PEGylation of BMP-2 by PEG-AL and PEG-NHS at acidic pH exhibits a partial N-terminal specificity which however might be sufficient for an efficient site-specific PEGylation process.     

Polyelectrolyte complex micelles by self-assembly of polypeptide-based triblock copolymer for doxorubicin delivery

Polyelectrolyte complex micelles were prepared by self-assembly of polypeptide-based triblock copolymer as a new drug carrier for cancer chemotherapy. The triblock copolymer, poly(l-aspartic acid)-b-poly(ethylene glycol)-b-poly(l-aspartic acid) (PLD-b-PEG-b-PLD), spontaneously self-assembled with doxorubicin (DOX) via electrostatic interactions to form spherical micelles with a particle size of 60–80 nm (triblock ionomer complexes micelles, TBIC micelles). These micelles exhibited a high loading capacity of 70% (w/w) at a drug/polymer ratio of 0.5 at pH 7.0. They showed pH-responsive release patterns, with higher release at acidic pH than at physiological pH. Furthermore, DOX-loaded TBIC micelles exerted less cytotoxicity than free DOX in the A-549 human lung cancer cell line. Confocal microscopy in A-549 cells indicated that DOX-loaded TBIC micelles were transported into lysosomes via endocytosis. These micelles possessed favorable pharmacokinetic characteristics and showed sustained DOX release in rats. Overall, these findings indicate that PLD-b-PEG-b-PLD polypeptide micelles are a promising approach for anti-cancer drug delivery.