树状大分子在生物医药领域中的应用

大量的末端官能团、紧密且精确控制的分子结构是树状大分子所具有的独特性质。这些特性使得树状大分子应用于生物医学领域，例如在分子水平上功效的增强，使药物在局部产生高浓度、分子标记及作为探针组件等。本文简要介绍树状大分子在这一领域的新动态，特别是树状大分子在诊断和治疗中的应用。在诊断方面，Gd^3 与树状大分子复合物可用作核磁共振成像造影剂，DNA树状大分子能用于常规的高效功能性基因检测及DNA生物传感器。在治疗方面，树状大分子可作为控释药物的载体、基因转染剂和硼中子俘获治疗剂等。研究表明，树状大分子还具有抗菌活性。     

树状大分子作为新型药物载体的研究进展

树状大分子是一类高度枝化的单分散性大分子，其内部结构呈疏水性，外表面呈亲水性，可称为“单分子胶束”。本文在简介树状大分子的发展及结构特点的基础上，阐述了树状大分子作为药物载体的作用特点及其与药物的结合方式。目前，树状大分子在介导药物靶向传递及基因转染等方面的应用也备受关注，是一种颇有发展潜力的新型载体。     

树状高分子介导的药物传输

研究报道单功能树状高分子（dendrimers）可通过自我封接寡核苷酸桥链形成具有多功能的树状高分子群，这意味着如果需要传输A药到含有X受体的细胞，只需将具有靶向该受体分子的树状高分子与载药树状高分子连接起来即可。     

树状聚合物纳米释药技术新平台

纳米生物技术(Nanobiotechnology)在生命科学中的应用相对较新。诸如碳布凯球(Buckyballs)、树状聚合物(Dendrimers)和金属纳米粒等纳米材料可用于体内和体外释药与诊断，有的产品接近上市。目前，纳米生物技术产品主要可分为3类：释药系统、显像剂和生物传感器。纳米生物技术市场出现仅几年，但可望得到迅速发展，预测至2008年其产品销售额可达30亿美元，全世界年增长率为28％。据估计，目前全球该市场份额划分：美国占65％，欧洲占20％，日本占10％，其他国家占5％。     

聚合物胶束在肿瘤治疗中的研究进展

聚合物胶束在肿瘤治疗方面具有高效、长效及高载药量等优势.本文简单比较了聚合物胶束与其它纳米级药物载体(如高分子直接键合药物、树枝状聚合物、脂质体)在临床应用上的优缺点.综述了聚合物胶束在肿瘤主动靶向性、环境刺激响应释药及医学成像等方面的研究进展.     

新型基因载体-聚酰胺-胺树状大分子聚合物

利用重组DNA技术进行疾病预防和治疗是近几年来的研究热点,如何提高重组DNA的转染效率一直是研究的难题之一,新型阳离子多聚物--聚酰胺-胺型树状大分子(Starburst PAMAM dendrimers,PAMAM-D)的出现为解决现存的难题带来希望.PAMAM-D最早由美国人Tomalia于1985年合成,目前已广泛应用于各个领域:药物载体、废水处理、催化剂、光电传感、基因载体等.由于PAMAM-D具有对称的刚性球体结构,表面带有大量正电荷,容易与带负电荷的核酸形成复合物,故作为基因载体具有许多优于其他现有转染试剂的优良特性.本文主要介绍了PAMAM-D的结构、性质、应用以及作为基因载体的优越性,并对今后的研究方向进行了概述.     

三嵌段聚合物在药物制剂中的应用研究进展

三嵌段聚合物系由2种或2种以上不同化合物通过聚合反应而合成的一种新型多功能两亲性载体材料,在水溶液中呈现优良的自组装性能。其用作药物载体时,可依据需求,通过改变其组成和结构而使其拥有温度敏感、pH敏感、磁敏感等多种特性,将其制成适宜剂型,能达到改善药物的溶解性等理化性质以及靶向性、缓控释性和生物利用度的目的,其在药物制剂领域具有广阔的应用前景。简介各种类型的三嵌段聚合物,着重概述近年来三嵌段聚合物在不同制剂剂型中的应用研究。     

阳离子聚合物在基因传递系统中的应用阳离子聚合物在基因传递系统中的应用

随着近代生物技术的发展与人类基因库的不断完善 ,各种与人类疾病相关基因逐步被揭晓 ,使人类从分子水平上认识某些疾病根源已逐步成为可能 ,为基因治疗提供了理论基础。基因治疗即ＤＮＡ给药系统 ,属于靶向给药系统 ,它不同于一般靶向药物作用于机体的某器官或某组织 ,它是细胞与分子水平上的靶向作用。基因治疗从 1980年第 1篇哺乳类基因转移公开报告[1]到 1994年 30 0余人接受临床基因治疗试验 ,整整花了 15年时间 ,1994年美国重组ＤＮＡ咨询委员会(ＲＡＣ)批准了人基因治疗方案。此后 ,许多分子疾病 (ｍｏｌｅｃｕｌａｒｄｉｓｅａｓｅ)…     

聚合物纳米粒子作为药物载体的研究与应用

目的:介绍聚合物纳米粒子作为药物载体的研究与应用现状。方法:参阅国内外文献,进行分析、归纳和总结。结果:聚合物纳米粒子可作为疏水药物、靶向药物和生物大分子药物的载体制备聚合物纳米粒的材料与方法具有多样性。结论:可生物降解的聚合物纳米粒载药系统具有可控释、靶向、保护生物大分子药物的活性等优势,是一个很有发展潜力的药物传递系统。     

Synthesis and Physicochemical Properties of Lipophilic Polyamide Dendrimers

Purpose. To synthesise symmetrical dendritic macromolecules with external lipid surfaces, to investigate their behaviour at the air-water interface and their ability to form supramolecular aggregates, and to gain an understanding of their potential as drug carriers. Methods. Dendrimeric compounds were synthesised with molecular weights ranging from 737 (1st generation dendrimer) to 25,246 (6th generation dendrimer) with carbon numbers ranging from 40 to 1404. The surface behaviour of these compounds was determined using spread films at the air/water interface on a Langmuir trough, and transmission electron microscopy was used to study the supramolecular aggregates formed by the more hydrophobic members of the series. Results. Dendrimers up to a maximum of 6 generations were synthesised. Surface saturation did not allow the completion of the synthesis of the 7th generation. The limiting surface areas at the air/water interface ranged from 0.4 nm² to 16.1 nm² values in good agreement with the areas derived from computer generated molecular models (0.5 nm² to 14 nm²). Conclusions. The synthesised dendrimers exhibited a linear relationship between area per molecule and the molecular weight of the compounds. A dendrimer with 16 lipoamino acid branches formed tubular supramolecular aggregates with a helical structure and dimensions in the long axis of 140–200 nm.     

PAMAM Dendrimers as Delivery Agents for Antisense Oligonucleotides

Purpose. To investigate the potential use of PAMAM dendrimers for the delivery of antisense oligonucleotides into cells under conditions that mimic the in vivo environment. Methods. We used HeLa cells stably transfected with plasmid pLuc/ 705 which has a luciferase gene interrupted by a human -globin intron mutated at nucleotide 705, thus causing incorrect splicing. An antisense oligonucleotide overlapping the 705 splice site, when delivered effectively, corrects splicing and allows luciferase expression. The ability of dendrimers to deliver oligonucleotides to HeLa Luc/705 cells was evaluated in the absence or presence of serum. Results. PAMAM dendrimers formed stable complexes with oligonucleotides that had modest cytotoxicity and showed substantial delivery activity. The dose of the oligonucleotide, the charge ratio of oligonucleotide to dendrimer, and the size (generation) of the dendrimers were all critical variables for the antisense effect. The physical properties of dendrimer/oligonucleotide complexes were further investigated using sedimentation and gel electrophoresis methods. Effective oligonucleo-tide/generation 5 dendrimer complexes were macromolecular rather than particulate in nature, and were not sedimented at 100,000 RPM. Compared to other types of delivery agents, PAMAM dendrimers were more effective in delivering oligonucleotides into the nucleus of cells in the presence of serum proteins. Conclusions. Our results suggest that PAMAM dendrimers form non-particulate delivery complexes that function in the presence of serum proteins and thus may be suited for in vivo therapeutic applications.     

The Lower-Generation Polypropylenimine Dendrimers Are Effective Gene-Transfer Agents

Objective. To evaluate polypropylenimine dendrimers (generations 1-5: DAB 4, DAB 8, DAB 16, DAB 32, and DAB 64) as gene delivery systems. Methods. DNA binding was evaluated by measuring the reduced fluorescence of ethidium bromide, and molecular modelling of dendrimer-DNA complexes also was performed. Cell cytotoxicity was evaluated against the A431 cell line using the MTT assay. In vitro transfection was evaluated against the A431 cell line using the -galactosidase reporter gene and N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methylsulphate (DOTAP) served as a positive control. Results. Molecular modeling and experimental data revealed that DNA binding increased with dendrimer generation. Cell cytotoxicity was largely generation dependent, and cytotoxicity followed the trend DAB 64 > DAB 32 > DAB 16 > DOTAP > DAB 4 > DAB 8, whereas transfection efficacy followed the trend DAB 8 = DOTAP = DAB 16 > DAB 4 > DAB 32 = DAB 64. Conclusion. The generation 2 polypropylenimine dendrimer combines a sufficient level of DNA binding with a low level of cell cytoxicity to give it optimum in vitro gene transfer activity.     

聚乙烯亚胺与壳聚糖在基因载体中的应用

基因治疗是攻克肿瘤最有潜力的方法之一,其关键是寻找可靠而有效的转基因载体。经过各种生物或化学修饰的聚乙烯亚胺和壳聚糖基因载体因转染效率高、细胞毒性低、靶向性强而成为研究热点。针对聚乙烯亚胺、壳聚糖及其衍生物应用于基因载体中存在的问题,将高转染效率的聚乙烯亚胺与高生物相容性的壳聚糖结合,可能得到兼具两者优点的新型基因载体。     

电致孔技术在透皮给药中的应用

电致孔可显著提高药物的经皮吸收,有望用于多肽和蛋白质类生物大分子药物的透皮给药.本文对电致孔法的透皮促渗机制、影响因素以及安全性进行了讨论,并介绍了有关实验装置及其在透皮给药中的应用.     

树枝状聚合物在靶向给药系统中的应用

树枝状聚合物(dendrimer)是一种新近发展起来的纳米级聚合物,具有树枝状的骨架和球状外形,树枝状分支的末端连接数目众多的活性官能团。药物既可以被包封在树枝状聚合物骨架内部的空腔,也可以化学偶联在树枝状聚合物表面的官能团上。表面的官能团还能同时连接多种对机体某些器官、组织和细胞有特异性相互作用的靶向配基,从而将包封的药物或者偶联的药物带到病变部位实现靶向治疗。同时,树枝状聚合物粒径很小,范围从G0代到G10代只有1～15 nm,偶联药物之后也不会超过30 nm,这样的粒径范围使得以树枝状聚合物为基础制备的纳米粒具有较强的高通透高滞留(enhanced permeability and retention,EPR)效应,从而对肿瘤组织实现被动靶向给药。本文旨在对树枝状聚合物的结构、性质及其在靶向给药系统中的应用作一简要综述。     

Endocytosis and Interaction of Poly (Amidoamine) Dendrimers with Caco-2 Cells

Purpose To investigate the internalization and subcellular trafficking of fluorescently labeled poly (amidoamine) (PAMAM) dendrimers in intestinal cell monolayers. Materials and methods PAMAM dendrimers with positive or negative surface charge were conjugated to fluorescein isothiocyanate (FITC) and visualized for colocalization with endocytosis markers using confocal microscopy. Effect of concentration, generation and charge on the morphology of microvilli was observed using transmission electron microscopy. Results Both cationic and anionic PAMAM dendrimers internalized within 20 min, and differentially colocalized with endocytosis markers clathrin, EEA-1, and LAMP-1. Transmission electron microscopy analysis showed a concentration-, generation- and surface charge-dependent effect on microvilli morphology. Conclusion These studies provide visual evidence that endocytic mechanism(s) contribute to the internalization and subcellular trafficking of PAMAM dendrimers across the intestinal cells, and that appropriate selection of PAMAM dendrimers based on surface charge, concentration and generation number allows the application of these polymers for oral drug delivery.     

微乳系统在透皮给药中的应用

概述了微乳透皮给药的渗透机制，微乳的各组分及结构对透皮渗透的影响和微乳中加入促渗剂的可行性。     

环糊精在鼻腔给药系统中的应用

综述了环糊精作为鼻腔给药系统赋形剂的应用及安全性.     

Transport of Poly(Amidoamine) Dendrimers across Caco-2 Cell Monolayers: Influence of Size, Charge and Fluorescent Labeling

Purpose To investigate the transport of poly(amidoamine) (PAMAM) dendrimers with positive, neutral and negatively charged surface groups across Caco-2 cell monolayers. Methods Cationic PAMAM-NH₂ (G2 and G4), neutral PAMAM-OH (G2), and anionic PAMAM-COOH (G1.5–G3.5) dendrimers were conjugated to fluorescein isothiocyanate (FITC). The permeability of fluorescently labeled PAMAM dendrimers was measured in the apical-to-basolateral direction. ¹⁴C-Mannitol permeability was measured in the presence of unlabeled and FITC labeled PAMAM dendrimers. Caco-2 cells were incubated with the dendrimers followed by mouse anti-occludin or rhodamine phalloidin, and visualized using confocal laser scanning microscopy to examine tight junction integrity. Results The overall rank order of PAMAM permeability was G3.5COOH > G2NH₂ > G2.5COOH > G1.5COOH > G2OH. ¹⁴C-Mannitol permeability significantly increased in the presence of cationic and anionic PAMAM dendrimers with significantly greater permeability in the presence of labeled dendrimers compared to unlabeled. PAMAM dendrimers had a significant influence on tight junction proteins occludin and actin, which was microscopically evidenced by disruption in the occludin and rhodamine phalloidin staining patterns. Conclusions These studies demonstrate that enhanced PAMAM permeability is in part due to opening of tight junctions, and that by appropriate engineering of PAMAM surface chemistry it is possible to increase polymer transepithelial transport for oral drug delivery applications.