聚乙二醇-聚谷氨酸-聚丙氨酸三嵌段共聚物的合成及其胶束的pH-响应性药物控制释放

通过大分子引发剂ω-胺基-α-甲氧基聚乙二醇引发N-羧基-α-氨基环内酸酐开环聚合和酸性水解制备了一种具有pH-响应性的三嵌段共聚物聚乙二醇-聚谷氨酸-聚丙氨酸(mPEG-PLGA-PLAA).通过核磁共振、ζ-电势、动态光散射、电子显微镜等手段表征了此类三嵌段共聚物的自组装过程及所形成胶束的pH-响应性.使用圆二色谱和红外光谱,分析了胶束结构随环境pH值转变过程中聚氨基酸链段二级结构的变化.以阿霉素作为模型药物,研究了三嵌段共聚物的载药能力和在不同pH条件下的药物释放能力.在碱性条件下,PLGA链段去质子化,链段从疏水性变为亲水性,胶束中间层由于水合作用变得松散,药物释放速率增加;在酸性条件下,PLGA链段质子化,不带电荷,与阿霉素药物分子间的静电相互作用消失.同时,PLGA链段α-螺旋含量增加,形成由链内氢键维持的刚性棒状结构,将链段周围包埋的药物分子"挤出",加速了药物的释放.     

乙二醇-聚(咪唑丙基-天冬酰胺)-聚丙氨酸三嵌段共聚物的合成及其pH-响应性药物控制释放性能的研究

聚天冬氨酸及其衍生物是一种具有良好生物相容性和可生物降解性的高分子材料, 被广泛应用于生物医药领域. 本研究通过大分子引发剂ω-胺基-α-甲氧基聚乙二醇引发N-羧基-α-氨基环内酸酐开环聚合和N-(3-氨丙基)咪唑侧基改性, 制备了一种侧链含有咪唑丙基的聚乙二醇-聚(咪唑丙基-天冬酰胺)-聚丙氨酸三嵌段共聚物. 在水溶液中, 此聚合物可自组装形成一种核-壳-冠型的三层共聚物胶束, 其中疏水性的聚丙氨酸链段自聚集形成胶束的核, 聚(咪唑丙基-天冬酰胺)链段形成具有pH-响应性的壳层, 用于包埋和释放药物, 外围的聚乙二醇链段可以提供一个稳定的水合冠层, 延长药物的体内循环时间. 利用咪唑环与游离阿霉素之间的π-π相互作用和疏水相互作用可以在自组装的过程中将阿霉素包埋到胶束内. 研究发现, 载药胶束随环境pH 值的降低药物的释放速率显著增加. 这主要是由于咪唑环在酸性条件下的质子化导致链段亲疏水性质发生明显变化.     

聚谷氨酸基双重响应性纳米胶束的制备及药物控释性能

首先制备端氨基聚(N-异丙基丙烯酰胺-co-聚乙二醇)大分子引发剂,再通过端氨基引发L-谷氨酸-γ-苄酯-N-羧酸酐开环聚合,制备了聚(N-异丙基丙烯酰胺-co-聚乙二醇)与聚(L-谷氨酸-γ-苄酯)的嵌段共聚物,将其中的γ-苄酯基团转化为酰肼基团后与阿霉素(DOX)共价结合,最后在水溶液中自组装成纳米胶束,制备了温度和pH值双重响应性纳米胶束。胶束外层由亲水性聚(N-异丙基丙烯酰胺-co-聚乙二醇)组成,具有温敏性,低临界溶液温度为38℃;胶束内层由聚(L-谷氨酸-γ-酰肼-阿霉素)组成。该胶束对于药物的释放具有温度和pH双重敏感性。     

聚L-丙氨酸-聚乙二醇嵌段共聚物纳米胶束的研究

分别以氨基聚乙二醇和氨基聚乙二醇单甲醚为大分子引发剂,采用开环聚合的方法合成了两亲性聚L-丙氨酸-聚乙二醇(PAE)和聚L-丙氨酸-聚乙二醇单甲醚(PAME)两种嵌段共聚物,其结构经1H NMR,IR,DSC,GPC等表征;利用园二色技术研究了其在水溶液中的二级结构,用芘荧光探针技术研究了其胶束的形成及其临界胶束浓度(CMC),利用透射电镜研究了胶束的形态。结果表明,在水溶液中共聚物链以α-螺旋构象形式存在,在一定条件下嵌段共聚物PAE-1,PAE-2,PAME-1和PAME-2能够形成球形的稳定胶束,PAE-1形成胶束的CMC为3.36×10-5mol.L-1,CMC值受嵌段类型和共聚物中聚L-丙氨酸链段含量的影响。     

聚L-丙氨酸-聚乙二醇嵌段共聚物的胶束化行为研究

以氨基聚乙二醇单甲醚(MPEG-NH₂)为大分子引发剂, 采用开环聚合方法合成了聚L-丙氨酸-聚乙二醇嵌段共聚物(PAME), 并对其结构进行了表征; 用圆二色谱(CD)研究了嵌段共聚物在水溶液中的二级结构, 用芘荧光探针技术研究了共聚物胶束的形成及其临界胶束浓度(CMC), 利用动态光散射(DLS)和透射电镜(TEM)研究了胶束的粒径分布和形态. 结果表明, 在水溶液中共聚物链以α-螺旋构象形式存在, 在一定条件下嵌段共聚物能够形成球形的稳定胶束, PAME-1形成胶束的CMC为1.99×10^-5 mol/L, CMC值受共聚物中聚L-丙氨酸(PLA)链段含量的影响.     

肽类树枝状大分子:自组装胶束及药物释放研究

本文以三代聚谷氨酸肽类树枝状分子(G3-Glu)为大分子引发剂,引发N-羧基-L-苯丙氨酸-环内酸酐(NCA-Phe)的开环聚合反应,制备聚谷氨酸树枝状大分子-聚苯丙氨酸嵌段共聚物.嵌段共聚物通过自组装形成以聚苯丙氨酸链段为核,聚谷氨酸树枝状大分子为壳的胶束.将抗肿瘤药物阿霉素负载到高分子胶束中,研究其药物释放性能及体外抗肿瘤效果.结果表明,共聚物胶束具有良好的生物相容性.载药胶束具有药物缓释效果,药物持续释放时间可达60h.载药胶束的体外抗肿瘤实验表明其对肝癌细胞HepG2具有很好的杀灭效果,共培养48h后对癌细胞的杀死率可高达75%.     

AB型聚乙二醇单甲醚-聚(L-丙氨酸)嵌段共聚物自组装过程的核磁共振研究

利用核磁共振方法研究了AB型双嵌段共聚物(MPEG45-b-PA32)在选择性溶剂中的自组装行为及胶束化过程.嵌段共聚物在三氟乙酸中聚氨基酸和聚乙二醇链段均处于自由运动状态,聚丙氨酸链段为无规线团结构.在向该溶液中逐渐加入氘代水的过程中,聚丙氨酸链段又重新聚集形成规整的二级结构.结合1H-NMR和COSY谱分析,结果显示这一自组装过程伴随着聚(L-丙氨酸)链段由无规线团向α-螺旋结构的构象转变,同时嵌段共聚物逐渐形成核-壳型胶束结构.利用透射电镜观察了所形成胶束的形态,嵌段共聚物主要形成粒径150 nm到220 nm的球形胶束.     

温度/pH响应性MPEG-b-PCL/PNVCL-b-PCL共聚物复合胶束的制备及载药性质

以基于亚胺键的嵌段共聚物为构筑单元的温度/pH响应性共聚物复合胶束(CMs), 由于具有亚胺键和核-壳-冠结构, 表现出较高的灵敏度和稳定性. 以聚乙二醇单甲醚(MPEG)、 N-乙烯基己内酰胺(NVCL)和ε-己内酯(ε-CL)为原料, 分别制备了端醛基聚乙二醇单甲醚(MPEG-CHO)、 端醛基聚N-乙烯基己内酰胺(PNVCL-CHO)和端氨基聚己内酯(H₂N-PCL), 利用希夫碱反应, 进一步制备了基于亚胺键的聚乙二醇单甲醚-b-聚己内酯(MPEG-b-PCL)和聚N-乙烯基己内酰胺-b-聚己内酯(PNVCL-b-PCL)嵌段共聚物, 对共聚物结构进行了确认. 以MPEG-b-PCL和PNVCL-b-PCL为构筑单元, 制备了共聚物复合胶束, 研究了复合胶束对阿霉素的包载、 释放性质和细胞毒性等. 研究结果表明, 室温下MPEG-b-PCL和PNVCL-b-PCL能够在水中自组装形成以PCL为核、 MPEG和PNVCL为混合壳的共聚物复合胶束, 在生理温度下, 温敏性PNVCL链段发生相变塌缩在PCL核表面, 能够防止药物扩散释放, 亲水性MPEG链段形成可控通道. 药物体外释放结果表明, 在弱酸性环境中, 亚胺键能够断裂, 胶束被破坏, 促进药物的释放, 噻唑蓝(MTT)实验表明, 复合胶束的细胞毒性较低.     

pH敏感型mPEG-Hz-PLA聚合物纳米载药胶束的制备

以合成的含有腙键的聚乙二醇大分子(mPEG-Hz-OH)为引发剂,以丙交酯为单体引发开环聚合反应,并通过调整投料比,制备出3种不同分子量的含腙键的生物可降解嵌段聚合物(mPEG-Hz-PLA).将腙键引入到聚合物的骨架中,以此构建聚合物胶束并作为pH敏感型纳米药物载体.制备的pH敏感型胶束的CMC值等于或低于5.46×10-4 mg/m L,DLS和TEM显示粒径均小于100 nm,且粒径分布均匀.非pH敏感型胶束在不同pH下的粒径变化不明显,而pH敏感型胶束在酸性环境下(pH=4.0和pH=5.0)胶束粒径出现了明显变化.以阿霉素为模型药物制备了pH敏感型载药胶束,其粒径比空白胶束大(100~200 nm),且粒径分布均匀.药物释放实验表明pH敏感型载药胶束随着释放介质pH降低累积释药量增高.MTT实验表明空白胶束对HeLa细胞和RAW264.7细胞几乎没有抑制作用,而载阿霉素的胶束对2种细胞的抑制作用都随着剂量的增大和时间的延长而增强.     

双重敏感mPEG-PDPA-P(AAm-co-AN)聚合物自组装体的药物递送

设计合成了一种新型两亲性三嵌段ABC聚合物聚乙二醇单甲醚-聚甲基丙烯酸二异丙胺基乙酯-聚(丙烯酰胺-co-丙烯腈)(mPEG-PDPA-P(AAm-co-AN))。该聚合物具有pH敏感嵌段PDPA和温度敏感嵌段P(AAm-co-AN)，临界溶解温度(UCST)较高，且可以通过改变单体比例来调节UCST。在室温、中性环境下，该聚合物通过自组装形成刺激响应型胶束，可用于抗肿瘤药物的控释研究。温度升高诱导聚合物胶束向不对称囊泡结构转变，pH降低促使聚合物形成更加松散的胶束。在体外释药探究中，聚合物胶束对亲水药物阿霉素(DOX)和疏水药物槲皮素都具有良好的载药效果，在37℃、pH=7.4的条件下泄漏量低，随着温度升高和pH降低，胶束释放药物的速率和释放量明显增加。     

Drug pH-sensitive release in vitro and targeting ability of polyamidoamine dendrimer complexes for tumor cells

Recently, dendrimers have been widely used in medical applications such as drug delivery and gene transfection. In this study, a pH-sensitive diblock copolymer of poly(methacryloyl sulfadimethoxine) (PSD) and polyethylene glycol (PEG) modified by lactose (LA-PEG-b-PSD) was synthesized. The pK(a) value of the LA-PEG-b-PSD was also measured. Then, polyamidoamine (PAMAM) complexes were prepared with PAMAM (G4.0) and LA-PEG-b-PSD by electrostatic interaction. To investigate drug pH-sensitive release in vitro, doxorubicin (DOX) was loaded in PAMAM. A higher drug cumulative release from LA-PEG-b-PSD/PAMAM complexes in phosphate buffered saline (PBS) was found at pH 6.5 than at pH 7.4. The cytotoxicity and cellular uptake of PAMAM complexes were investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and confocal microscopy. LA-PEG-b-PSD/PAMAM/DOX complexes were able to enhance the cytotoxicity of DOX against HepG2 cells at pH 7.4. Confocal microscopy showed a higher cellular uptake of PEG-b-PSD/PAMAM complexes at pH 6.5. PAMAM complexes modified by lactose showed a higher affinity for hepatic cancer cells than those without lactose at pH 7.4. These results suggest that LA-PEG-b-PSD/PAMAM complexes exhibit selective targeting and cytotoxicity against HepG2 cells. In vivo antitumor studies showed that the LA-PEG-b-PSD/PAMAM/DOX complexes displayed higher antitumor efficacy compared with non-targeted PAMAM/DOX and DOX solution. These results indicate that this strategy should be applicable to the treatment of liver cancers.     

NOVEL pH-SENSITIVE DRUG DELIVERY SYSTEM BASED ON NATURAL POLYSACCHARIDE FOR DOXORUBICIN RELEASE

A novel pH-sensitive nanoparticle drug delivery system (DDS) derived fl'om natural polysaccharide pullulan for doxorubicin (DOX) release was prepared.Pullulan was functionalized by successive carboxymethylization and amidation to introduce hydrazide groups.DOX was then grafted onto pullulan backbone through the pH-sensitive hydrazone bond to form a pullulan/DOX conjugate.This conjugate self-assembled to form nano-sized particles in aqueous solution as a result of the hydrophobic interaction of the DOX.Tr...     

Novel water-soluble and pH-responsive anticancer drug nanocarriers: doxorubicin-PAMAM dendrimer conjugates attached to superparamagnetic iron oxide nanoparticles (IONPs)

PH-responsive drug release system based on the conjugates of PAMAM dendrimers-doxorubicin (PAMAM-DOX) and superparamagnetic iron oxide (Fe(3)O(4)) nanoparticles (IONPs) has been constructed and characterized. The IONPs were stabilized by mPEG-G2.5 PAMAM dendrimers. The anticancer drug DOX was conjugated to the dendrimer segments of amino-stabilized IONPs using hydrazine as the linker via hydrazone bonds, which is acid cleavable and can be used as an ideal pH-responsive drug release system. The drug release profiles of DOX-PAMAM dendrimer conjugates were studied at pH 5.0 and 7.4. The results showed that the hydrolytic release profile can be obtained only at the condition of lysosomal pH (pH=5.0), and IONPs participated in carrying DOX to the tumor by the Enhanced Permeability and Retention (EPR) effect. These novel DOX-conjugated IONPs have the potential to enhance the effect of MRI contrast and cancer therapy in the course of delivering anticancer drugs to their target sites. Although the dendrimer-DOX-coated IONPs do not have any targeting ligands attached on their surface, they are potentially useful for cancer diagnosis in vivo.     

Dual‐responsive crosslinked micelles of a multifunctional graft copolymer for drug delivery applications

A novel multifunctional amphiphilic graft copolymer has been synthesized consisting of a biodegradable poly(l ‐aspartic acid) backbone that was decorated by water‐soluble poly(ethylene glycol) (PEG) and pH‐responsive poly(N,N‐diethylaminoethyl methacrylate) (PDEAEMA) side‐chains as well as thiol pendant groups. This graft copolymer together with doxorubicin (DOX) formed micelles in water at pH = 10.0 with PDEAEMA and DOX acting as the core and PEG serving as the micellar corona. Upon oxidation, the thiol groups dimerized to form disulfide bonds, thus “locking in” the micellar structure. These crosslinked micelles expanded as the pH was decreased from 7.4 to 5.0 or upon the addition, at pH = 7.4, of glutathione (GSH), a thiol‐containing oligopeptide that is present in cancerous cells and cleaves disulfide bonds. At pH = 5.0, GSH addition triggered the disassembly of the micelles. The expansion and disassembly of the micelles have been determined via in vitro experiments to evaluate their DOX release behavior. More importantly, the graft copolymer micelles could enter cells by means of endocytosis and deliver DOX to the nuclei of ovarian cancer BEL‐7402 cells. Thus, this polymer and its micelles are promising candidates for drug delivery applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1536–1546     

Monoclonal Antibody-conjugated Polyphosphoester-hyd-DOX Prodrug Nanoparticles for Targeted Chemotherapy of Liver Cancer Cells

In order to overcome the limitation of traditional active nano-therapeutic drugs on tumor targeting effciency which cannot reach the receptor/target in sufficient amount in the body,in this work,we developed a monoclonal antibody (mAb) and a polymer-hyd-doxorubicin prodrug conjugate,which enables the self-assembled nanoparticles to have precise targeting,tumor tissue aggregation and pH-sensitive drug release.We first prepared an amphiphilic polymer prodrug,abbreviated as H2N-PEEP-b-PBYP-hyd-DOX,via a combination of ring-opening polymerization (ROP) and "click" chemistry,in which PEEP and PBYP represent two kinds of phosphoester segmemts,-hyd-is hydrazone bond.After self-assembly into prodrug nanoparticles (PDNPs) with a diameter of about 93 nm,CD147 mAb was conjugated onto the PDNPs by EDC/NHS chemistry to form mAb-PDNPs.For the PDNPs and mAb-PDNPs,we also investigated their stability,in vitro drug release behavior and cellular uptake.The results showed that the pH-responsive PDNPs can remain relatively stable under the condition of PB 7.4 buffer solution.However,under acidic conditions or in the presence of phosphodiesterase I (PDE I),both the amount and rate of DOX release increased at the same incubation period.Cytotoxicity assay showed that mAb-PDNPs exhibited higher cytotoxicity (IC50:1.12 mg·L-1) against HepG2 cells than PDNPs (IC50:2.62 mg·L-1) without monoclonal antibody.The nanoparticles with antibodies mAb-PDNPs have relatively better stability and can directly achieve the targeting drug delivery through CD147 mAb.     

pH-Responsive Self-assembled Nanoparticles of Simulated P(AA-co-SA)-g-PEG for Drug Release

Simulated graft copolymer of poly(acrylic acid-co-stearyl acylate) [P(AA-co-SA)] and poly(ethylene glycol) (PEG) was synthesized, where acrylic acid, stearyl acylate and PEG was employed as the pH-sensitive, hydrophobic and hydrophilic segment, respectively. Polymeric nanoparticles prepared by the dialysis of simulated graft copolymer solution in dimethylformamide against citrate buffer solution with different pH values were characterized by transmission electron microscopy (TEM), fluorescence technique and laser light scattering (LLS). TEM image revealed the spherical shape of the self-aggregates, which was further confirmed by LLS measurements. The critical aggregation concentration increased markedly (10 to 150 mg/L) with increasing pH (4.6 to 7.0), consistent with the de-protonation of carboxylic groups at higher pH. The hydrodynamic radius of polymeric nanoparticles decreased from 118 nm at pH 3.4 to 90 nm at pH 7.0. The controlled release of indomethacin from those nanoparticles was investigated, and the self-assembled nanoparticles exhibited improved performance in controlled drug release.     

PtBA-g-PPEGMEMA接枝共聚物的合成及其包埋阿霉素的研究

通过可逆加成-裂解链转移聚合和原子转移自由基聚合,制备了以聚丙烯酸叔丁酯为主链、以聚(聚乙二醇单甲醚甲基丙烯酸酯)为侧链的两亲性接枝共聚物PtBA-g-PPEGMEMA,该方法克服了以往通过聚合物修饰来引入接枝点时所存在的接枝点密度不高和不可控的局限性.接着,以PtBA-g-PPEGMEMA为载体,对抗肿瘤药物阿霉素进行了负载,制备得到了尺寸为164.8nm的纳米载药胶束.其释放试验表明,该体系具有缓释特征.     

Synthesis and physicochemical characterization of amphiphilic triblock copolymer brush containing pH-sensitive linkage for oral drug delivery

A novel and well-defined pH-sensitive amphiphilic triblock copolymer brush poly(lactide)-b-poly(methacrylic acid)-b-poly(poly(ethylene glycol) methyl ether monomethacrylate) (PLA-b-PMAA-b-PPEGMA) and its self-assembled micelles were developed for oral administration of hydrophobic drugs. The copolymer and its precursors were synthesized by the combination of activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) and ring-opening polymerization (ROP) techniques. The molecular structures and characteristics were confirmed by GPC, (1)H NMR, and FT-IR. The critical micelle concentration (CMC) values of PLA-b-PMAA-b-PPEGMA in aqueous medium varied from 1.4 to 2.6 mg/L, and the partition equilibrium constant (K(v)) of pyrene in micellar solutions ranged from 2.873 × 10(5) to 3.312 × 10(5). The average sizes of the self-assembled blank and drug-loaded micelles were 140-250 nm determined by DLS in aqueous solution. The morphology of the micelles was found to be spherical by SEM. Nifedipine (NFD), a poorly water-soluble drug, was selected as the model drug and wrapped into the core of micelles via dialysis method. The in vitro release behavior of NFD from the micelles was pH-dependent. In simulated gastric fluid (SGF, pH 1.2), the cumulative release percent of NFD was relative low, while in simulated intestinal fluid (SIF, pH 7.4), more than 96% was released within 24 h. All the results showed that the pH-sensitive PLA-b-PMAA-b-PPEGMA micelle may be a prospective candidate as oral drug delivery carrier for hydrophobic drugs with controlled release behavior.