Cationic hyperbranched poly(amino ester): A novel class of DNA condensing molecule with cationic surface, biodegradable three-dimensional structure, and tertiary amine groups in the interior
Cationic hyperbranched poly(amino ester): A novel class of DNA condensing molecule with cationic surface, biodegradable three-dimensional structure, and tertiary amine groups in the interior
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DOI：
10.1021/ja005715g
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发表时间：
2001-03-14
影响因子：
15
通讯作者：
Park, JS
中科院分区：
文献类型：
--
作者：
Lim, YB;Kim, SM;Park, JS
树枝状聚合物1和超支化聚合物2已经成为一个引人注目的研究领域。树枝状大分子具有精确定义的形状和分子量，然而，这是以迭代合成步骤为代价实现的。相反，超支化聚合物是通过一步聚合合成的，其形状不规则，分子量分布广泛。目前正在努力利用这些高度支化的分子在各种应用中，包括组合化学，表面涂层，光活性系统，以及基因或药物输送。在非病毒基因传递方面的最新进展表明，聚乙烯亚胺(PEI)和星状突变型PAMAM树状大分子是有效的基因转移分子。3人们普遍认为，与其他阳离子聚合物相比，PEI或PAMAM的高转染率是由于聚合物的“内体缓冲”或“质子海绵”效应。PEI或PAMAM内部的叔胺在酸性的内体pH下质子化，这要么直接由于阳离子聚合物的膜活性，要么可能由于机械膨胀或渗透作用而破坏内体。据报道，可生物降解的阳离子聚合物是无毒的，可以将DNA凝聚成致密的颗粒，可以转染哺乳动物细胞。4在此基础上，我们得出结论：具有三维结构和叔胺基团的可生物降解阳离子聚合物可能是一种无毒、高效的基因载体。本文描述了超支化聚氨基酯的合成和表征，这种超支化聚氨基酯具有一种新型的分子结构，它具有可生物降解的、三维的、含有叔胺基团的结构。通过合适的AB2单体设计和表面功能化，可以合成出符合我们最初设想的超支化聚(氨基酯)。乙醇胺2与丙烯酸甲酯通过Michael加成反应合成了分子中心含有一个羟基、两个甲酯基团和一个叔胺基团的单体1。聚合反应是在氨核星形爆裂PAMAM树枝状大分子-0.5代3为核部分(单体/核比为200/1)，Al(OIPR)3为催化剂(1mol%)的存在下进行的。添加核心部分以降低多分散性并防止形成交联型或过高分子量聚合物。5在没有核部分的情况下，高转化率导致聚合物的凝胶化，这些聚合物很难在任何溶剂中溶解。据报道，低分子量低聚物是在聚合的早期阶段形成的，同时耗尽了单体。5A，6在没有核心部分的情况下，在单体匮乏状态下，通过现有低聚物的偶联，分子量迅速增长，应该会导致凝胶。反应保持在相对较低的温度，140℃，以最大限度地减少单体的汽化和不必要的副反应。反应在减压下连续脱除生成的甲醇，反应时间优化，避免了聚合物凝胶化，反应向高转化率方向发展。反复沉淀到乙醚中导致聚合物4成为粘性油。相关的超支化含氨基聚酯衍生物已经在前面描述过了。7众所周知，尺寸排除层析(SEC)测量往往低估支化聚合物的真实分子质量。8因此，人们普遍认为支化聚合物的真分子质量应为3-5…。
Dendrimers1 and hyperbrached polymers2 have become an attractive field of research. Dendrimers have a precisely defined shape and molecular weight, which, however, is achieved at the cost of iterative synthetic steps. In contrast, hyperbranched polymers are synthesized in one-step polymerization resulting in irregular shape and broad molecular weight distribution. Efforts are currently in progress to utilize these highly branched molecules in a variety of applications involving combinatorial chemistry, surface coating, photoactive system, and gene or drug delivery. Recent advances in nonviral gene delivery have revealed polyethyleneimine (PEI) and starburst PAMAM dendrimers as effective gene transfer molecules. 3 It is generally accepted that the high transfection efficiency of PEI or PAMAM compared to that of other cationic polymers is due to the “endosome buffering” or “proton sponge” effect of the polymers. Tertiary amines in the interior of PEI or PAMAM are protonated at acidic endosomal pH, which disrupts the endosome either directly due to the membrane activity of the cationic polymers or possibly by mechanical swelling or osmotic effects. It has been reported that biodegradable cationic polymers are nontoxic and condense DNA into compact particles that can transfect mammalian cells. 4 On the basis of these findings, we concluded that biodegradable cationic polymer with threedimensional structure and interior tertiary amine groups would be a nontoxic and efficient gene carrier through the endosome buffering effect. In this paper, we describe the synthesis and characterization of hyperbranched poly (amino ester) with a novel molecular architecture in that it has a biodegradable, threedimensional, and interior tertiary amine group containing structure. With a suitable design of AB2 monomer and surface functionalization, hyperbranched poly (amino ester) could be synthesized conforming to our initial idea (Scheme 1). Monomer 1, bearing one hydroxyl group, two methyl ester groups, and one tertiary amine group in the center of the molecule, was synthesized by Michael addition of ethanolamine 2 with methyl acrylate. The polymerization reaction was carried out in the bulk in the presence of ammonia core starburst PAMAM dendrimer-0.5 generation 3 as a core moiety (monomer/core ratio, 200/1) and Al (OiPr) 3 as a catalyst (1 mol%). The core moiety was added to decrease polydispersity and prevent the formation of cross-linked or excessively high molecular weight polymers. 5 In the absence of the core moiety, high conversion resulted in gelation of polymers which were difficult to dissolve in any solvent. It is reported that low molecular weight oligomers are formed in the early stages of polymerization while depleting the monomers. 5a, 6 In the absence of the core moiety, the rapid growth of molecular weight via the coupling of existing oligomers in the monomer-starved state should result in gelation. The reaction was maintained at a relatively low temperature, 140 C, to minimize the vaporization of monomer and unwanted side reactions. The reaction was driven toward high conversion as the methanol formed was removed continuously under reduced pressure with an optimized reaction time to avoid polymer gelation. Repeated precipitation into diethyl ether resulted in polymer 4 as a viscous oil. Related hyperbranched aminecontaining polyester derivatives have been described previously. 7 It is well-known that size exclusion chromatography (SEC) measurement tends to underestimate the true molecular masses of branched polymers. 8 So it is generally accepted that true molecular masses of branched polymers should be three to five …