Center of Drug Discovery, State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 210009, PR China.
Biomaterials. 2013 Apr;34(11):2773-86. doi: 10.1016/j.biomaterials.2013.01.030. Epub 2013 Jan 23.
pH-sensitive liposomes (HHG2C(18)-L and PEGHG2C(18)-L) based on zwitterionic oligopeptide lipids as anticancer drug carriers were developed and evaluated for effective intracellular delivery and enhanced antitumor activity. The amino acid-based lipids, 1,5-dioctadecyl-l-glutamyl 2-histidyl-hexahydrobenzoic acid (HHG2C(18)) and 1,5-distearyl N-(N-α-(4-mPEG2000) butanedione)-histidyl-l-glutamate (PEGHG2C(18)), were synthesized, which have the multistage pH-response to tumor microenvironmental pH (pH(e), pH 6.0-7.0) and endosomal/lysosomal pH (pH(i), pH 4.0-6.0) successively. HHG2C(18)-L contains HHG2C(18), while PEGHG2C(18)-L includes HHG2C(18) and PEGHG2C(18). Both of them displayed the capability of charge conversion to the surrounding pH. The zeta potentials of HHG2C(18)-L and PEGHG2C(18)-L were negative at pH 7.4, whereas positive at pH 6.5 and more positive at lower pH. Coumarin 6-loaded HHG2C(18)-L (C6/HHG2C(18)-L) and PEGHG2C(18)-L (C6/PEGHG2C(18)-L) showed higher tumor cellular uptake due to electrostatic absorptive endocytosis at pH(e) (pH 6.5), produced proton sponge effect for endo-lysosomal escape, and accumulated to the mitochondria based on stronger positive charge by the hydrolysis of a pH-sensitive linker at pH(i) (pH 5.5 and pH 4.5). Furthermore, temsirolimus (CCI-779)-loaded HHG2C(18)-L (CCI-779/HHG2C(18)-L) and PEGHG2C(18)-L (CCI-779/PEGHG2C(18)-L) had significantly higher antiproliferative and apoptosis inducing effects toward the human renal carcinoma (A498) cells at pH 6.5 relative to that at pH 7.4. The half maximal inhibitory concentration (IC50) of CCI-779/HHG2C(18)-L and CCI-779/PEGHG2C(18)-L were about 3 μg/mL and 5 μg/mL at pH 6.5, 1.67-fold and 1.60-fold improved relative to that at pH 7.4, respectively. The total apoptotic ratio of CCI-779/HHG2C(18)-L and CCI-779/PEGHG2C(18)-L increased from 9.90% and 7.78% at pH 7.4 to 19.53% and 12.10% at pH 6.5, respectively. In vivo, CCI-779/PEGHG2C(18)-L after intravenous administration presented remarkably higher bioavailability and blood persistence compared with unPEGylated CCI-779/HHG2C(18)-L, and had the strongest antitumor efficacy against xenograft renal cancer (Renca) tumor models. Accordingly, the results provide the feasibility of using pH-sensitive zwitterionic oligopeptide lipids to extend the applications of liposomes to efficient anticancer drug delivery in cancer therapy.
基于两性离子寡肽脂质的 pH 敏感脂质体（HHG2C(18)-L 和 PEGHG2C(18)-L）作为抗癌药物载体被开发和评估，以实现有效的细胞内递药和增强的抗肿瘤活性。基于氨基酸的脂质 1,5-二硬脂酰基-l-谷氨酰基-2-组氨酰基-六氢苯并酸（HHG2C(18)）和 1,5-二硬脂酰基 N-(N-α-(4-mPEG2000)丁二酮基)-组氨酰基-l-谷氨酸（PEGHG2C(18)）被合成，它们具有对肿瘤微环境 pH（pH(e)，pH 6.0-7.0）和内体/溶酶体 pH（pH(i)，pH 4.0-6.0）的多阶段 pH 响应。HHG2C(18)-L 含有 HHG2C(18)，而 PEGHG2C(18)-L 则包含 HHG2C(18)和 PEGHG2C(18)。两者均显示出对周围 pH 值进行电荷转换的能力。HHG2C(18)-L 和 PEGHG2C(18)-L 的 zeta 电位在 pH 7.4 时为负，而在 pH 6.5 时为正，在更低的 pH 值时更正。载香豆素 6 的 HHG2C(18)-L（C6/HHG2C(18)-L）和 PEGHG2C(18)-L（C6/PEGHG2C(18)-L）由于在 pH(e)（pH 6.5）时静电吸收内吞作用而具有更高的肿瘤细胞摄取率，通过内体/溶酶体逃逸的质子海绵效应，并在 pH(i)（pH 5.5 和 pH 4.5）时通过 pH 敏感连接体的水解积聚到线粒体上，基于更强的正电荷。此外，载替西罗莫司（CCI-779）的 HHG2C(18)-L（CCI-779/HHG2C(18)-L）和 PEGHG2C(18)-L（CCI-779/PEGHG2C(18)-L）在 pH 6.5 时对人肾癌细胞（A498）的增殖抑制和诱导凋亡作用明显高于 pH 7.4。CCI-779/HHG2C(18)-L 和 CCI-779/PEGHG2C(18)-L 的半最大抑制浓度（IC50）在 pH 6.5 时约为 3 μg/mL 和 5 μg/mL，分别比 pH 7.4 时提高了 1.67 倍和 1.60 倍。CCI-779/HHG2C(18)-L 和 CCI-779/PEGHG2C(18)-L 的总凋亡率分别从 pH 7.4 时的 9.90%和 7.78%增加到 pH 6.5 时的 19.53%和 12.10%。在体内，静脉注射 CCI-779/PEGHG2C(18)-L 后与未 PEG 化的 CCI-779/HHG2C(18)-L 相比，具有显著更高的生物利用度和血液持久性，并对异种移植肾癌细胞（Renca）肿瘤模型具有最强的抗肿瘤疗效。因此，这些结果提供了使用 pH 敏感两性离子寡肽脂质将脂质体的应用扩展到癌症治疗中高效抗癌药物递送的可行性。
