受体介导长循环脂质体的制备及其研究进展

受体介导长循环脂质体,具有延长脂质体在血液循环中的半衰期、提高其稳定性、改变脂质体在体内的生物学分布,赋予脂质体主动靶向性的优点。本文主要综述了受体介导长循环脂质体的制备、研究进展及其在核医学中的应用。     

聚乙二醇双官能基异端修饰的研究进展

正聚乙二醇(PEG)是一种惰性、非致癌性聚合物,目前是修饰生物活性分子和纳米粒子表面的首选聚合物之一~([1-2])。聚乙二醇已被证明可以增强疏水性药物、蛋白质、核酸、脂质体的溶解性、提高稳定性和延长循环时间~([3-4])。此外,PEG还能通过增强渗透和保留(EPR)效应实现特异性肿瘤靶向治疗~([5-6])。PEG现已成为生物技术和生物医学界关注的焦点,广泛应用于大分子与表面的连接、药物和脂质体的靶向性、纳米颗粒功能化等诸多领域~([7-11])。     

卵磷脂和氢化卵磷脂长循环阿霉素脂质体的制备及缓释研究

采用薄膜超声法制备卵磷脂(EPC)和氢化卵磷脂(HEPC)长循环阿霉素脂质体,研究比较EPC和HEPC长循环阿霉素脂质体在大鼠体内释药的差异,选择良好的靶向性药物载体.用高效液相色谱法研究EPC和HEPC长循环阿霉素脂质体在大鼠体内的药物动力学.大鼠体内药物动力学研究结果表明,HEPC长循环阿霉素脂质体在血中平均驻留时间(MRT)为23.3h,EPC长循环阿霉素脂质体在血中MRT为12.0h.HEPC长循环阿霉素脂质体是更好的靶向性药物载体.     

卵磷脂和氢化卵磷脂长循环阿霉素脂质体的制备及大鼠体内释药研究

研究比较卵磷脂(Egg phosphatidylcholine,EPC)和氢化卵磷脂(Hydrogenated egg phosphatidylcholine,HEPC)长循环阿霉素脂质体在大鼠体内释药的差异,选择良好的靶向性药物载体.用高效液相色谱法研究EPC和HEPC长循环阿霉素脂质体在大鼠体内的药物动力学.结果表明,HEPC长循环阿霉素脂质体在血中平均驻留时间(MRT)为23.3 h,EPC长循环阿霉素脂质体在血中平均驻留时间(MRT)为12.0 h.HEPC长循环阿霉素脂质体是更好的靶向性药物载体.     

免疫脂质体与临床

将特异性抗体粘附于脂质体上形成免疫脂质体,它能特异性识别表达具有某种抗原的细胞或组织.由它携带药物具有靶向性强,毒副作用小,半衰期长等优点.针对其特点,临床应用免疫脂质体开展了对多种疾病的治疗.根据免疫脂质体携带药物对疾病治疗的优缺点,本文综述了近几年的临床观察和研究的进展.     

磷脂酰聚乙二醇单甲醚脂质体的制备及其载药性能

目的 制备新型磷脂酰聚乙二醇单甲醚脂质体,并初步考察其载药性能和对人肺腺癌A549细胞的抗肿瘤效果.方法 化学合成一系列磷脂酰聚乙二醇单甲醚,应用超声薄膜法制备脂质体和载药脂质体,测定它们的药物包封率和粒径;采用MTT法考察磷脂酰聚乙二醇单甲醚脂质体和载药磷脂酰聚乙二醇单甲醚脂质体对A549细胞增殖的影响;采用共聚焦显微镜观察脂质体在细胞中的定位.结果 载紫杉醇脂质体的药物包封率约为83％;粒径范围在100～200 nm;MTT实验显示载紫杉醇脂质体能显著抑制A549细胞的增殖并有长循环效果,而脂质体本身并无抑制作用.结论 载药磷脂酰聚乙二醇单甲醚脂质体有缓释作用,可以开发成为新型的抗肿瘤药物载体.     

PreS1多肽(2-21Aa)介导肝脏靶向脂质体的制备及其靶向性研究

目的以来源于乙肝病毒(hepatitis B virus,HBV)PreS1抗原2~21 Aa多肽(HBVpreS/2-21myr)为导向的肝细胞靶向长效循环脂质体(long circulating liposome,LCL),通过体外细胞学实验验证其靶向性。方法固相合成HBVpreS/2-21myr多肽,化学偶联Mal-PEG2000-DSPE(马来酰亚胺-聚乙二醇2000-硬脂酰基磷脂酰乙醇胺)生成HBVpreS/2-21myr-PEG2000-DSPE;采用乙醇注入法制备脂质体,包裹荧光素钠(fluorescein sodium,FS)形成HBVpreS/2-21myr-FS-LCL;激光粒度仪、透射电镜、高效液相色谱检测和观察脂质体的粒径、超微形态及包封率;以稳定表达NTCP的HepG2为细胞模型,分析纳米脂质体靶向性。结果合成的靶向脂质体,呈类圆形,大小均匀,粒径为(94.09±9.2)nm,达到纳米级别;有效包裹荧光素钠,包封率为(89.32±1.02)%;与无靶向修饰脂质体相比,可递送更多的荧光素钠进入细胞内。结论 HBVpreS/2-21myr修饰的靶向脂质体,有较高的包封率,为纳米脂质体,能特异性地通过NTCP靶向肝细胞,有望成为一种新型的肝细胞靶向给药系统。     

整合素αvβ3受体靶向载药脂质体的制备及体外靶向性

背景:含RGD序列的多肽是多种整合素的识别位点,以其相对分子质量小、稳定、易于制备,且无免疫原性等优点被广泛用于纳米靶向药物传递系统的设计。目的:制备以RGD环五肽为配基的整合素αvβ3载药脂质体,通过体外细胞学实验证实其受体靶向性。方法:使用人工合成的RGD环五肽作为靶向分子探针,通过高压均质法制备靶向整合素αvβ3载药脂质体,采用扫描电镜和激光粒度分析仪检测纳米颗粒形态和粒径;以流式细胞分析观察其对血管平滑肌细胞的特异性标记,并考察荷载药物的离体缓释能力以及体外靶向能力。结果与结论:合成的靶向载药脂质体粒径为(175±6)nm,包封率为(96.33±1.02)%,体外溶出时间超过5d。靶向载药脂质体对整合素αvβ3具有较高的特异性亲和力,可通过受体介导的内吞作用进入细胞内。提示制备的靶向整合素αvβ3载药脂质体,具有较高的药物包封率及缓释性,能与整合素αvβ3受体特异性结合,是一种新型的受体介导靶向制剂。     

脂质体在基因治疗中的应用研究及进展***

背景：脂质体是常用的安全的基因载体,然而由于其本身组成及结构的原因,应用和发展受到了限制,其转染效率和治疗效果成为基因治疗研究中最为重要的参考因素。 目的：回顾脂质体在基因治疗中的应用以及研究进展。 方法：由第一作者计算机检索1995/2011中国期刊全文数据库、CALIS全国医学文献/服务系统以及康健循证医学知识仓库,中英文检索词分别为“脂质体、基因、转染”和“liposome、gene、transfection”。 结果与结论：脂质体作为基因载体较病毒载体具有安全性高,免疫原性小,毒性小,容易制备等优点已成功应用于很多体外及动物体内实验,但由于其转染效率低,靶向性低等缺点使其发展受到了很大限制,所以目前脂质体在基因治疗中的研究热点在于提高脂质体的转染效率,在靶细胞和靶器官达到治疗浓度才能有更好的治疗效果。     

脂质体携载抗HIV-1药物

由于HIV耐药株的产生、特殊器官和细胞中HIV的隐匿、抗HIV药物的毒副反应及半衰期短等问题的出现,促使人们寻找高效低毒和具有靶向性的抗HIV药物.脂质体具有被动或主动靶向病毒复制活跃和贮存区、细胞内靶向和控制药物释放、延长药物半衰期、提高药效和降低毒副作用等优点,是潜在携载抗HIV药物的良好载体.     

Liposome-oriented transport of therapeutic drugs

The attempts to use liposomes as containers for the transport of therapeutic drugs have been undertaken during the recent 40 years. However, the first success was achieved only in the 80-ies, when the sterically stabilized liposomes were invented. It was found that the liposome biological layer modified through, adding to it, certain polymers prolonged the blood circulation and reduced the capture of liposomes by RES cells. Elaboration of immunoliposomes, i.e. those conjugated with antibodies, was the next step in the path of perfecting the liposomes as a transport tool for the sake of binding with target-cells and to ensure the address-oriented delivery of drugs to a pathology focus. Preclinical and clinical testing of liposome-form of antitumor drugs witnessed to their lower toxicity and better pharmacokinetic indices; besides, they selectively accumulate themselves in tumor cells and have a more pronounced therapeutic effect even at lower doses of drugs in case of tumors resistant to the already made chemotherapy.     

Liposomes: applications in medicine

Liposomes are spherical lipid bilayers from 50 nm to 1000 nm in diameter that serve as convenient delivery vehicles for biologically active compounds. The field of liposome research has expanded considerably over the last 30 years. It is now possible to engineer a wide range of liposomes varying in size, phospholipid composition and surface characteristics to suit the specific application for which they are intended. This paper gives an overview of the main advances in liposome research from a point of view of their applications in medicine. Aqueous contrast enhancing agents entrapped in liposomal carriers can be targeted to the liver and spleen and distinctions can be made between normal and tumorous tissue using computed tomography. Topical application of liposomes has great potential in dermatology. Liposomes have been used to deliver anticancer agents in order to reduce the toxic effects of the drugs when given alone or to increase the circulation time and effectiveness of the drugs. From the original concept of encapsulating hemoglobin in an inert shell, liposome-encapsulated hemoglobin (LEH) has evolved into a fluid proven to carry oxygen, capable of surviving for reasonable periods in the circulation and amenable to large-scale production. Liposomes may be used to target specific cells by attaching amino acid fragments such as antibodies or proteins or appropriate fragments that target specific receptor sites. Liposomal DNA delivery vectors and further enhancements in the forms of LPDI and LPDII are some of the safest and potentially most versatile transfer vectors used to date. DNA vaccination and improved efficiency of gene therapy are just a few of the upcoming applications of liposomes.     

Enhanced retention and anti-tumor efficacy of liposomes by changing their cellular uptake and pharmacokinetics behavior

Although PEGylated liposome-based drug delivery systems hold great promising applications for cancer therapy due to their prolonged blood circulation time, PEGylation significantly reduces their cellular uptake, which markedly impairs the in vivo tumor retention and antitumor efficiency of drug-loaded liposomes. Most importantly, it has been proved that repeated injections of PEGylated liposomes with cell cycle specific drug such as topotecan (TPT) in the same animal at certain time intervals will induce “accelerated blood clearance” (ABC) phenomenon, which decreases the tumor accumulation of drug-loaded liposomes and presents a tremendous challenge to the clinical use of liposome-based drug delivery systems. Herein, we developed a zwitterionic poly(carboxybetaine) (PCB) modified liposome-based drug delivery system. The presence of PCB could avoid protein adsorption and enhance the stability of liposomes as that for PEG. Quite different from the PEGylated liposomes, the pH-sensitive PCBylated liposomes were internalized into cells via endocytosis with excellent cellular uptake and drug release ability. Furthermore, the PCBylated liposomes would avoid ABC phenomenon, which promoted the tumor accumulation of drug-loaded liposomes in vivo. With higher tumor accumulation and cellular uptake, the PCBylated drug-loaded liposomes significantly inhibited tumor growth and provided a promising approach for cancer therapy.     

叶酸修饰聚合物和脂质体药物载体及其靶向治疗的研究现状*

背景：叶酸介导的靶向药物载体被广泛研究。 目的：总结叶酸修饰靶向聚合物和脂质体药物载体的研究现状。 方法：由作者应用计算机检索2000-01/2010-12 Web of Science和CNKI数据库,选择叶酸修饰靶向聚合物和脂质体药物载体的相关文章,英文检索词为“folic acid, drug carriers, targeted delivery system, polymer, liposome”,中文检索词为“叶酸,药物载体,靶向,聚合物,脂质体”。共纳入相关文献19 篇进行综述。 结果与结论：叶酸受体在多种肿瘤细胞表面过度表达,而在多数正常组织中的表达仅限于一些难于进入血液循环的上皮细胞顶膜。正因为叶酸受体表达的特性,叶酸受体天然配体——叶酸成为将药物靶向到肿瘤细胞的重要分子。叶酸具有与叶酸受体的高亲和力、低免疫原性等优点,这使得叶酸介导肿瘤靶向的研究得到迅速发展。含叶酸靶向的药物载体体系中,主要分为3大类：即人工合成高分子载体体系、脂质体和天然高分子载体体系。      

Microfabricated Drug Delivery Systems: Concepts to Improve Clinical Benefit

Important classes of drugs have yet to benefit from advances in drug delivery technology. Strategies to provide reasonable oral bioavailability of peptide and proteins drugs remain elusive, for example. Systemic cancer drugs produce dose-limiting toxicities largely due to their lack of selectivity. Although delivery systems such as immunotoxins and liposomes improve selectivity of a few cancer drugs, current technology is not suitable for the vast majority of such molecules. Systems able to mimic the body's natural feedback mechanisms for secretion of hormones such as insulin represents yet another unmet medical need. Microfabrication techniques may permit the creation of drug delivery systems that possess a combination of structural, mechanical, and perhaps electronic features which may surmount some of these challenges. In this review, drug delivery concepts are presented which capitalize on the strengths of microfabrication. Possible applications include micromachined silicon membranes to create implantable biocapsules for the immunoisolation of pancreatic islet cells—as a possible treatment for diabetes—and sustained release of injectable drugs needed over long time periods. Asymmetrical, drug-loaded microfabricated particles with specific ligands linked to the surface are proposed for improving oral bioavailability of peptide (and perhaps protein) drugs. Similarly designed particles with sizes in the 2–10 m range may be safe to administer intravenously and a clinical strategy is suggested for using such microparticles for treating solid tumors. Although hypothetical now, work is in progress to prove the concepts presented here and to validate the intuitive belief that there is an important place for microfabricated systems in drug delivery.     

Bioadhesive Microdevices for Drug Delivery: A Feasibility Study

A variety of delivery systems have been devised to improve the oral bioavailability of drugs including enterically coated tablets, capsules, particles, liposomes, and others. Microfabrication technology, however, may offer some potential advantages over conventional drug delivery technologies. This technology, combined with appropriate surface chemistry, may permit the highly localized and unidirectional release of drugs, permeation enhancers, and/or promoters. In this study, we demonstrate the fabrication of prototype reservoir containing microparticles and a surface chemistry protocol that can be used to bind lectin via avidin-biotin interactions to silicon microparticles. In vitro studies show enhanced bioadhesion of these lectin conjugated microparticles. Such an approach can be used to improve the absorption of pharmacologically active biopolymers such as peptides, proteins and oligonucleotides into circulation at targeted sights in the GI system. Moreover, the use of microfabrication allows one to tailor the size, shape, reservoir volume, and surface characteristics of the drug delivery vehicle.     

A Novel Liposome Surface Modification Agent that Prolongs Blood Circulation and Retains Surface Ligand Reactivity

Abstract

Liposomes are recognized as potentially useful drug carriers but many problems preclude practical medical application. Liposomes bind with serum proteins (opsonization) and are captured by the reticuloendothelial system cells in the liver and spleen, which limits their ability to deliver drugs to other target sites. Modification of lipids with flexible, hydrophilic polymers such as poly(ethylene glycol) (PEG) to yield sterically stabilized liposomes is one approach to improve liposome blood circulation and tissue distribution properties. In this study, we examined liposomes prepared using lipids modified with a new branched oligoglycerol (BGL) moiety for steric stabilization. This novel BGL comprised 14 glycerol units (termed BGL014) connected with flexible ether linkages, resulting in a branched cascade-like structure that is highly expanded in aqueous solution. BGL014 was coupled to 1,2-distearoylphosphatidylethanolamine to yield BGL014-modified lipids. Incorporation of BGL014 into liposomes (BGL014L) resulted in long blood circulation times, despite a much thinner fixed aqueous layer thickness compared to PEG formulations. BGL014 produced a liposome surface coating that appears to function through steric inhibition of non-specific protein binding without strong interference of specific protein-binding reactions. Liposome structure and functionality was maintained following BGL014-modification, as the incorporation ratio of drug remained high. These results suggest that the BGL014 modification of liposomes is a promising approach to produce stable and long circulating drug carriers capable of selective binding to specific proteins.     

不同脂质体透皮机制的研究进展

脂质体作为药物载体进行透皮给药是一种很有发展前途的给药方式.目前常用的有普通脂质体、变形脂质体、乙醇脂质体等.脂质体促透的机理主要是影响皮肤角质层.作用于皮肤附属器以及改变药物的外在特性使之透过皮肤,从而提高药物透皮吸收的速率和总量.其促透机理有水合作用、穿透作用、变形作用和渗透压驱动作用等.脂质体在透皮方面有着广泛的应用前景.     

Liposome mediated affection of monocytes.

Dichloromethylene diphosphonate (Cl2MDP) enclosed in liposomes, when injected intravenously, selectively eliminates all phagocytizing macrophages that are in direct contact with the blood circulation of the spleen and the liver. We examined whether Cl2MDP containing liposomes affect, in addition, rat monocytes and bone marrow macrophage precursors (BMMP's). In addition to Phosphatidylcholine-Cholesterol liposomes (PC liposomes), we also used mannosylated PC liposomes (PCMAN liposomes), which are reported to bind more efficiently to macrophages. Monocytes appeared to be affected 24 h after injections of 2 ml of Cl2MDP containing PC as well as PCMAN liposomes. In addition, almost no macrophages could be detected in one week cultures of blood leukocytes isolated from these animals; cultures from control animals contained +/- 50% macrophages. Bone marrow macrophage precursors did not appear to be affected.     

Reduction-sensitive polymers and bioconjugates for biomedical applications

Reduction-sensitive biodegradable polymers and conjugates have emerged as a fascinating class of biomedical materials that can be elegantly applied for intracellular triggered gene and drug delivery. The design rationale of reduction-sensitive polymers and conjugates usually involves incorporation of disulfide linkage(s) in the main chain, at the side chain, or in the cross-linker. Reduction-sensitive polymers and conjugates are characterized by an excellent stability in the circulation and in extracellular fluids, whereas they are prone to rapid degradation under a reductive environment present in intracellular compartments such as the cytoplasm and the cell nucleus. This remarkable feature renders them distinct from their hydrolytically degradable counterparts and extremely intriguing for the controlled cytoplasmic delivery of a variety of bioactive molecules including DNA, siRNA, antisense oligonucleotide (asODN), proteins, drugs, etc. This review presents recent advances in the development of reduction-sensitive biodegradable polymers and conjugates, with particular focus on the up-to-date design and chemistry of various reduction-sensitive delivery systems including liposomes, polymersomes, polymeric micelles, DNA containing nanoparticles, polyion complex micelles, nano- and micro-gels, nanotubes, and multi-layered thin films. It is evident that reduction-sensitive biodegradable polymers and conjugates are highly promising functional biomaterials that have enormous potential in formulating sophisticated drug and gene delivery systems.