Chen Peipei, Qiu Min, Deng Chao, Meng Fenghua, Zhang Jian, Cheng Ru, Zhong Zhiyuan
Biomedical Polymers Laboratory, and Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, People's Republic of China.
Biomacromolecules. 2015 Apr 13;16(4):1322-30. doi: 10.1021/acs.biomac.5b00113. Epub 2015 Mar 19.
pH-Responsive chimaeric polypeptide-based polymersomes (refer to as pepsomes) were designed and developed from asymmetric poly(ethylene glycol)-b-poly(l-leucine)-b-poly(l-glutamic acid) (PEG-PLeu-PGA, PEG is longer than PGA) triblock copolymers for efficient encapsulation and triggered intracellular delivery of doxorubicin hydrochloride (DOX·HCl). PEG-PLeu-PGA was conveniently prepared by sequential ring-opening polymerization of l-leucine N-carboxyanhydride and γ-benzyl-l-glutamate N-carboxyanhydride using PEG-NH2 as an initiator followed by deprotection. Pepsomes formed from PEG-PLeu-PGA had unimodal distribution and small sizes of 64-71 nm depending on PLeu block lengths. Interestingly, these chimaeric pepsomes while stable at pH 7.4 were quickly disrupted at pH 5.0, likely due to alternation of ionization state of the carboxylic groups in PGA that shifts PGA blocks from hydrophilic and random coil structure into hydrophobic and α-helical structure. DOX·HCl could be actively loaded into the watery core of pepsomes with a high loading efficiency. Remarkably, the in vitro release studies revealed that release of DOX·HCl was highly dependent on pH, in which about 24.0% and 75.7% of drug was released at pH 7.4 and 5.0, respectively, at 37 °C in 24 h. MTT assays demonstrated that DOX·HCl-loaded pepsomes exhibited high antitumor activity, similar to free DOX·HCl in RAW 264.7 cells. Moreover, they were also potent toward drug-resistant MCF-7 cancer cells (MCF-7/ADR). Confocal microscopy studies showed that DOX·HCl-loaded pepsomes delivered and released drug into the cell nuclei of MCF-7/ADR cells in 4 h, while little DOX·HCl fluorescence was observed in MCF-7/ADR cells treated with free drug under otherwise the same conditions. These chimaeric pepsomes with facile synthesis, efficient drug loading, and pH-triggered drug release behavior are an attractive alternative to liposomes for targeted cancer chemotherapy.
基于pH响应性嵌合多肽的聚合物囊泡（称为胃蛋白酶体）由不对称聚（乙二醇）-b-聚（L-亮氨酸）-b-聚（L-谷氨酸）（PEG-PLeu-PGA，PEG长于PGA）三嵌段共聚物设计并开发而成，用于高效封装和触发盐酸多柔比星（DOX·HCl）的细胞内递送。PEG-PLeu-PGA通过使用PEG-NH2作为引发剂依次进行L-亮氨酸N-羧基环内酸酐和γ-苄基-L-谷氨酸N-羧基环内酸酐的开环聚合，随后进行脱保护方便地制备而成。由PEG-PLeu-PGA形成的胃蛋白酶体具有单峰分布，并且根据PLeu嵌段长度，尺寸为64 - 71 nm。有趣的是，这些嵌合胃蛋白酶体在pH 7.4时稳定，但在pH 5.0时迅速破坏，这可能是由于PGA中羧基的电离状态改变，使PGA嵌段从亲水性无规卷曲结构转变为疏水性α-螺旋结构。DOX·HCl可以以高负载效率主动装载到胃蛋白酶体的水核中。值得注意的是，体外释放研究表明，DOX·HCl的释放高度依赖于pH，在37℃下24小时内，在pH 7.4和pH 5.0时分别释放约24.0%和75.7%的药物。MTT分析表明，负载DOX·HCl的胃蛋白酶体表现出高抗肿瘤活性，类似于RAW 264.7细胞中的游离DOX·HCl。此外，它们对耐药MCF-7癌细胞（MCF-7/ADR）也有效。共聚焦显微镜研究表明，负载DOX·HCl的胃蛋白酶体在4小时内将药物递送并释放到MCF-7/ADR细胞的细胞核中，而在相同条件下用游离药物处理的MCF-7/ADR细胞中几乎观察不到DOX·HCl荧光。这些嵌合胃蛋白酶体具有合成简便、药物负载效率高和pH触发药物释放行为，是用于靶向癌症化疗的脂质体的有吸引力的替代物。
