Cao Li, Xiao Yi, Lu Wei, Liu Shiyuan, Gan Lin, Yu Jiahui, Huang Jin
1 Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, 12655 East China Normal University , Shanghai, China.
2 Department of Radiology and Nuclear Medicine, Changzheng Hospital, Naval Medical University, Shanghai, China.
J Biomater Appl. 2018 Jan;32(6):826-838. doi: 10.1177/0885328217741522. Epub 2017 Nov 13.
In order to achieve the passive tumor targeting and acid-triggered drugs release in lysosomes, optimized delivery system for doxorubicin based on pH-sensitive complex nanomicelles with suitable particle size was developed in this research. Particularly, poly(L-succinimide) was thoroughly ring-opened by ethylenediamine to give the poly(N-(2-aminoethyl)-L-aspartamide). Then, graft copolymer mPEG-graft-poly(N-(2-aminoethyl)-L-aspartamide)-hexahydrophthalic acid (mPEG-g-P(ae-Asp)-Hap) was synthesized by grafting mPEG-2000 and hexahydrophthalic anhydride onto poly(N-(2-aminoethyl)-L-aspartamide). In vitro studies revealed that mPEG-g-P(ae-Asp)-Hap copolymer was stable in neutral solutions but tend to be hydrolyzed under acidic condition, which was attributed to the acid-sensitive properties of hexahydrophthalic amides (β-carboxylic amides). MPEG-g-P(ae-Asp)-Hap copolymer with critical aggregation concentration of 0.166 mg·mL could self-assemble into stable blank nanomicelles with an average particle hydrodynamic diameter of 98.1 nm, but the hydrodynamic diameter of doxorubicin-loaded nanomicelles (mPEG-g-P(ae-Asp)-Hap·Dox) was smaller and approximately 77.5 nm. MPEG-g-P(ae-Asp)-Hap·Dox nanomicelles showed sustained drug release profiles over 34 h, and the cumulative drug release showed a tendency to increase from 25% to 62% with the pH value decreasing from 7.4 to 5.0 due to the acid-triggered disassembly of nanomicelles. The cytotoxicity of mPEG-g-P(ae-Asp)-Hap·Dox nanomicelles against A549 treated with 40 mM NHCl (lysosomotropic weak bases) was decreased significantly than that without NHCl treatment, further confirmed the drug release from the nanomicelles was triggered by the low pH value of lysosome (pH 5.0). Compared with doxorubicin HCl, mPEG-g-P(ae-Asp)-Hap·Dox nanomicelle drug showed enhanced cellular uptake ability during 2 or 4 h of incubation due to the endocytosis mechanism of nanomicelle drug. In summary, the cleavage of pH-sensitive β-carboxylic amides bonds on the hydrophobic branch of mPEG-g-P(ae-Asp)-Hap copolymer triggered the disassembly of the nanomicelles and release of doxorubicin in the acidic lysosomal compartments of cancer cells. These nanomicelles exhibited excellent potential for drug delivery due to their smart properties-PEGylation, suitable size, and acid-triggered drug release.
为了实现被动肿瘤靶向以及在溶酶体中酸触发的药物释放，本研究开发了一种基于具有合适粒径的pH敏感复合纳米胶束的阿霉素优化递送系统。具体而言，聚（L-琥珀酰亚胺）通过乙二胺完全开环得到聚（N-（2-氨基乙基）-L-天冬酰胺）。然后，通过将mPEG-2000和六氢邻苯二甲酸酐接枝到聚（N-（2-氨基乙基）-L-天冬酰胺）上合成了接枝共聚物mPEG-接枝-聚（N-（2-氨基乙基）-L-天冬酰胺）-六氢邻苯二甲酸（mPEG-g-P（ae-Asp）-Hap）。体外研究表明，mPEG-g-P（ae-Asp）-Hap共聚物在中性溶液中稳定，但在酸性条件下易于水解，这归因于六氢邻苯二甲酰胺（β-羧酰胺）的酸敏性质。临界聚集浓度为0.166 mg·mL的mPEG-g-P（ae-Asp）-Hap共聚物可以自组装成平均颗粒流体动力学直径为98.1 nm的稳定空白纳米胶束，但载阿霉素纳米胶束（mPEG-g-P（ae-Asp）-Hap·Dox）的流体动力学直径较小，约为77.5 nm。mPEG-g-P（ae-Asp）-Hap·Dox纳米胶束在34小时内呈现持续的药物释放曲线，并且由于纳米胶束的酸触发解离，随着pH值从7.4降至5.0，累积药物释放呈现从25%增加到62%的趋势。与未用40 mM NHCl（溶酶体促渗弱碱）处理的情况相比，mPEG-g-P（ae-Asp）-Hap·Dox纳米胶束对A549细胞的细胞毒性显著降低，进一步证实了纳米胶束中的药物释放是由溶酶体的低pH值（pH 5.0）触发的。与盐酸阿霉素相比，由于纳米胶束药物的内吞作用机制，mPEG-g-P（ae-Asp）-Hap·Dox纳米胶束药物在孵育2或4小时期间表现出增强的细胞摄取能力。总之，mPEG-g-P（ae-Asp）-Hap共聚物疏水支链上pH敏感的β-羧酰胺键的断裂触发了纳米胶束的解离以及阿霉素在癌细胞酸性溶酶体区室中的释放。由于其智能特性——聚乙二醇化、合适的尺寸和酸触发的药物释放，这些纳米胶束在药物递送方面展现出优异的潜力。
