可点击树型共聚物的分子设计及其复合功能纳米载体的肿瘤靶向性能研究

In this project, focused on the problems related to cancer targeting drug delivery, a series of novel tree-like amphiphilic polyester/hyperbranched polyglycerol diblock copolymer with tunable properties and clickable extremities will be designed and synthesized via living polymerization and 'click' chemistry. These copolymers not only possess preferred properties derived from polyester and polyether such as biocompatibility, biodegradable and long circulation time, but also allow the coupling reaction between drug carrier and targeting molecules take place in a mild and effective condition. Thus, the biological activity of the targeting molecules can be maximally reserved after the coupling process. As for these tree-like copolymers and their drug carriers, studies will be pursued mainly from three aspects. Firstly, the synthetic method will be studied to obtain the tree-like copolymers with designable and controllable structure. Secondly, the targeting abilities of these nano-carriers formed from the tree-like copolymers will be examined via varying the surface densities and steric hindrance of the targeting molecules. Thirdly, the morphology and the encapsulation efficiency of the nano-carriers will be studied by tuning the component of the tree-like copolymers. To achieve real-time monitor and quantitative detection for the targeted process, multifunctional nano-carriers based on these clickable tree-like copolymers will be further established, where functions including targeted drug delivery, magnetic response and fluorescent identification will be endowed. Considering the results of the above studies, the preferred nano-carriers for targeted drug delivery will be screened out and further evaluated with their biocompatability and tumor inhibition in animal experiments.

本课题针对肿瘤靶向给药的难题，通过可控活性聚合、点击化学等方法，设计合成一系列结构新颖的可点击树型聚酯/超支化聚缩水甘油醚两亲性嵌段共聚物。该共聚物不仅完全保留了聚酯、聚醚类材料所固有的良好生物相容性、可降解排除、长循环等优势，而且其亲水链段的超支化结构将提供较线性结构更多的可修饰端基，更长的体内循环时间。利用其可点击端基更可进一步实现在点击化学温和高效的条件下进行靶向分子的偶联，从而最大限度的保持偶联后靶向分子的生物活性。研究树型共聚物的可控合成方法；研究载体表面靶向分子密度及空间自由度对其靶向性能的影响，探寻其影响规律；研究树型共聚物分子组成对其载体结构及载药能力的影响规律。借助树型共聚物的结构特点和性能优势，构建集靶向给药、磁响应和荧光可视功能为一体的复合功能纳米载体，以实现对体内靶向过程的实时监控和定量检测。筛选适合靶向给药的纳米载体，通过动物实验评价其生物相容性和抑瘤效果。

在该项目的资助下，我们进行了聚酯聚缩水甘油醚嵌段共聚物的合成探索。但是在实际执行中我们发现有如下问题：1.聚酯端基的活性较低后修饰可点击基团的产率较低造成大部分聚酯链没有与缩水甘油相连接，无法形成预订的嵌段共聚物；2.两种大分子单体虽然是通过点击化学这种反应活性选择性都很高的化学反应进行偶合，但是由于高分子的分子量太高两种高分子的端基浓度相对较低，因此无法事先比较高的产率，这也导致我们无法得到这种树形结构的大分子。虽然如此，我们还将继续尝试通过别种方式来构建这种树型大分子，我们相关的努力仍在继续。由于聚合物的合成方面遇到较大难题，我们从以下方面进行了探索性研究。a. 超支化聚缩水甘油接枝的磁性Fe3O4纳米粒子的合成方法改进和核磁体内造影研究。我们首先对合成方法进行了改进，由原来的多步法，改为现在的一锅发。通过一锅法分别以乙酰丙酮铁，草酸铁为前体成功的合成出HPG-grafted MNPs。所合成的HPG-grafted MNPs的粒径可通过调节其前体的浓度进行调节。该HPG-grafted MNPs可高度分散于水相介质中，例如在细胞培养液和血清中都有极好分散性。尤其是平均粒径为8 nm的粒子更是能够以高达45mg/ml的浓度均匀稳定地分散在水相介质中。体外细胞毒性实验（MTT）表明HPG-grafted MNPs对于巨噬细胞和3T3成纤维细胞不具有显著毒性。最后，我们进行了该纳米粒子的初步的动物体内核磁造影实验，观察了HPG-grafted MNPs在白兔体内的分布情况和造影能力，发现这种粒子可以在家兔体内实现长循环。b.温敏性石墨烯的研制及其用于水中有机色素的清除。首先，我们通过ATRP反应，以N,N'-[6-(2-氯丙酰胺基)己基]苝-3,4,9,10-四羧酸酰亚胺（PBI-Cl）作为引发剂，以N-异丙基丙烯酰胺为单体，合成了PBI-PNIPAM。随后，我们将PBI-PNIPAM通过π-π共轭的方式分子级别的形式组装到GO薄片上，成功地制备出具有温度敏感性能氧化石墨烯材料。随后，我们又将这种材料应用于水中有机色素的清除，发现这种温敏石墨烯可有效吸附水中色素，并且可以方便的通过加热聚集而从水相中移除。