【作者】 郑程；

【导师】 朱康杰； 邱利焱；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2009， 博士

【摘要】 本文选择聚膦腈作为聚合物主链，以不同分子量的聚乙二醇为亲水性的侧链，尝试使用甘氨酸乙酯、对氨基苯甲酸乙酯和氨基胆固醇三种不同的化合物作为疏水取代基，合成了一系列具有不同物化性能的两亲接枝聚膦腈。确立了取代基比例可控、聚合产率高的两亲接枝聚膦腈合成方法，通过核磁共振、紫外光谱、凝胶渗透色谱和差示扫描量热法分析表征了共聚物结构。对两亲接枝聚膦腈在水溶液中的自组装行为进行了系统研究。通过芘荧光探针法测定了共聚物在水溶液中的临界胶束浓度，结果表明随着共聚物中疏水取代基团含量的增大临界胶束浓度逐渐降低。共聚物组装体的形态主要采用透射电子显微镜来观察，结果表明以聚乙二醇为亲水链的两亲共聚物在水溶液中能够自发组装形成不同结构的聚集体：对于以甘氨酸乙酯为疏水基团的两亲接枝聚膦腈，当甘氨酸乙酯取代度较高时，其胶束呈现为棒状，随着共聚物中甘氨酸乙酯的含量逐渐降低，胶束体系中同时出现有棒状和球形两种形态的胶束，进一步减少甘氨酸乙酯基团的含量则共聚物胶束只剩下球形一种形态。对于以对氨基苯甲酸乙酯为疏水基团的两亲接枝聚膦腈，当亲水链含量较高时，共聚物胶束的形态呈现为球形；当亲水链含量下降到一定值时两亲共聚物会形成聚合物囊泡。对于以分子量1100的PEG为亲水链的对氨基苯甲酸乙酯取代的两亲接枝聚膦腈，当PEG含量为某一特定水平时其在水中形成的自组装体的形态会变得不稳定，在不同浓度下使用不同溶剂透析得到的组装体形态有所区别，提高聚合物浓度则组装体结构会发生由网状结构向球形粒子的转变。氨基胆固醇的疏水性很强，因此以氨基胆固醇为疏水取代基的两亲接枝聚膦腈只有在亲水链段含量很高时才能在水中形成稳定的球形胶束。两亲接枝聚膦腈胶束能够增溶疏水性药物，胶束对疏水药物的负载能力受到共聚物的组成、药物的种类以及载药胶束制备方法的影响；以甘氨酸乙酯为疏水基团的两亲接枝聚膦腈胶束在包载药物后形态会发生显著变化，其中甘氨酸乙酯含量较低的共聚物空白胶束在载药后原先具有的棒状胶束全部转变成球形纳米载药胶束，而甘氨酸乙酯含量较高的共聚物载药胶束的形态则与载药量有关，当载药量较低时载药胶束依然呈现与空白胶束一致的球形，而当载药量增加到一定程度后载药胶束就转变为空心球状。载药胶束在具有不同pH值的释放介质中的体外释药研究结果说明载药胶束具备缓释特征，在较低的pH值下释放速度会明显加快。由对氨基苯甲酸乙酯取代的两亲接枝聚膦腈形成的聚合物囊泡可以用来运载水溶性的抗癌药物，对装载水溶性药物的聚合物囊泡体外释药行为的研究结果说明囊泡中药物释放过程遵循Fickian扩散机理。对载药胶束和囊泡抗肿瘤能力的体外评价实验结果显示，两亲接枝聚膦腈载药胶束能有效抑制肿瘤细胞的生长，以甘氨酸乙酯为疏水基团的两亲聚膦腈载药胶束对阿霉素耐药型MCF-7乳腺癌细胞的半数抑制浓度IC50是未包封的游离药物对照组的三分之一；而包载水溶性抗肿瘤药物的两亲聚膦腈共聚物囊泡对肝癌细胞HepG2的半数抑制浓度IC50要比直接使用原料药的对照组低17倍。通过研究肿瘤细胞对两亲接枝聚膦腈载药胶束的摄取，我们发现阿霉素耐药型MCF-7乳腺癌细胞摄取载药胶束的效率比其摄取游离药物的效率高出很多，4小时时与载药胶束一起孵育的细胞中阿霉素的荧光强度可达相同浓度游离药物对照组的3倍。载药胶束能显著改变阿霉素在阿霉素耐药MCF-7细胞中的分布，由胶束运载的阿霉素更容易进入到细胞核中；此外，实验结果表明载药胶束的粒径能显著影响胶束被细胞摄取的速率，孵育4小时时粒径小的胶束被肿瘤细胞摄取的量是粒径大的胶束的1．9倍。利用大鼠角叉菜胶诱导的急性炎症模型考察了以氨基胆固醇为取代基的两亲聚膦腈载药胶束的炎症治疗性能。与相同剂量的药物溶液对照组相比，共聚物载药胶束组的治疗效果明显优于相应的对照组。总之，两亲接枝聚膦腈胶束药物传递系统在药物控释领域特别是在抗肿瘤药物传递方面具有很强的应用潜力和广阔的发展前景，值得进行深入研究。更多还原

【Abstract】 In this study,a new series of amphiphilic methoxy-poly（ethylene glycol）graftedpolyphosphazenes with different side groups including glycine ethyl ester（GlyEt）,ethyl 4-aminobenzoate（EAB）and Cholesterol （Chol）were synthesized andcharacterized.Differential synthesis strategies of amphiphilic graft polyphosphazeneswere established to achieve controlled hydrophilic ratio of each copolymer withrelatively high product yield.Copolymer structure was characterized by NMR,UV,DSC and GPC.Fluorescence probe was adopted to determine the critical micelle concentration（CMC）of amphiphilic copolymers,and the results revealed that the CMC willdecrease with the increasing hydrophobic content of amphiphilic copolymers.Themorphology of assemblies was observed by TEM,it was found that aggregates withvarious shaps can be formed in aqueous sulution.For the amphipHilic graftpolyphosphazenes that using GlyEt as hydrophobic groups,rod-like micelles wereobserved when copolymer has high GlyEt content,as the weight ratio of hydrophobicgroups decreased,micelles with multiple morphology obtained,where the rods andspherical micelles are coexistent,micelles of copolymer with low GlyEt content are allin spherical shape.For copolymers with EAB as hydrophobic groups,thesecopolymers could self-assemble into distinct aggregates in aqueous solutions. Spherical micelles were observed for the copolymer sample with higher hydrophilicweight fraction.However,when the hydrophilic weight fractions decreased to less than0.50,vesicle-like polymersomes were formed.Noteworthy,micelles derived fromcopolymer with high EAB content and PEG₁₁₀₀as hydrophilic chains are not quitestable,depending on the type of co-solvent and the copolymer concentrations,the shapof aggregates altered between network aand spherical micelles.It was also found thatcholesterol group is quite hydrophobic,cholesterol substituted amphiphilicpolyphosphazenes can not dissolved in water and form micelles until the weightcontent ofhydrophilic PEG side chains reach to a relatively high level.Different hydrophobic drugs were encapsulated into polymeric micelles derivedfrom those copolymers;the size,drug-loading content and entrapment efficiency aredetermined by several factors including physicochemical characteristics of copolymer,structure of drug molecular and the preparation parameters.Drug loading exhibitedconsiderably strong impact on the morphology of micelles derived from GlyEtsubstituted polyphosphazenes:turned the rod-like and spherical drug free micelles intospheres and vesicles respectively.Drug-loaded micelles are quite stable and can befreeze-dried for long-term storage,in vitro release behavior of those drug-loadedmicelles exhibits a sustained release manner and a pH-related drug release wasconfirmed.Water-soluble anti-cancer drug was successfully loaded into the aqueous core ofpolymersome derived from copolymers with EAB as hydrophobic groups,which wasclearly observed by transmission electron microscopy.Drug release profile of thisdrug-loaded polymersome provided linear relationships for Higuchi plotting,indicatingthat Fickian diffusion played an important role during this release period.In vitro cytotoxicity assay revealed that drug-loaded micelles of amphiphilicpolyphosphazenes can effectively suppress proliferation of tumor cells,drug-loadedmicelles based on GlyEt substituted polyphosphazenes have enhanced cytotoxicity on adriamycin-resistant MCF-7 cell line,the 72h IC50 reduced 3 fold comparaed to freedrug formulation;The cytotoxicity against HepG2 cells of drug-loaded polymersomesbased on copolymers with EAB as hydrophobic groups was significantly enhancedcomparaed to free drug formulation,and the 24h IC50 reduced 17 fold by usingpolymersome carrier.Moreover,flow cytometry results revealed that the drug-loaded micelles havehigher cell internalization efficiency,fluorescence intensity of drug in theadriamycin-resistant MCF-7 cells incubate with drug-loaded micelles can be 3 foldhigher than that of free drug parallel,it was also found that smaller size favored theinternalization of micelles by adriamycin-resistant MCF-7 cells,cell up-take efficiencyof drug-loaded micelles with particale size of 147nm is 1.9 fold higher comparaed todrug-loaded micelles with particale size of 279nm.carrageenan-induced acute arthritis was employed to evaluate the therapeutic effectof indomethacin-loaded amphiphilic polyphosphazene micelles,and the resultsindicated that drug-loaded polymeric micelles exhibit more significant therapeuticeffect than that of control group.In summary,the present novel amphiphilic polyphosphazene copolymers have highpotentials on drug delivery applications especially on anti-tumor drug delivery systems.More extensive studies are definitely needed.更多还原