School of Pharmacy, Faculty of Medical and Health Sciences, The University of Auckland, Auckland 1142, New Zealand.
Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Auckland 1142, New Zealand.
Int J Pharm. 2018 Sep 5;548(1):288-296. doi: 10.1016/j.ijpharm.2018.07.009. Epub 2018 Jul 4.
To facilitate the development of PEG-cleavable pH-sensitive liposomes (CL-pPSL), this study aimed to fully characterize a new pH-sensitive polymer, PEG-Hz-CHEMS. Polyethylene glycol (PEG) functionalised with 4-carboxybenzaldehyde (PEG) was linked to cholesteryl hemisuccinate (CHEMS) via an acid labile hydrazide-hydrazone hybrid bond (CONHNCH) to form PEG-Hz-CHEMS. The polymer was post-inserted into DOPE/CHEMS liposomes to form CL-pPSL. A validated stability-indicating HPLC-UV method was developed with the aid of multiple linear regression for the mobile phase. The assay was used to evaluate the pH-sensitivity, pathways of cleavage of the polymer and the PEGylation degree of CL-pPSL. The pH-sensitivity of CL-pPSL was compared with conventional PEGylated pH-sensitive (pPSL) using a calcein leakage assay. At 37 °C, PEG-Hz-CHEMS was relatively stable at pH 7.4 with a half-life of 24 h. In comparison, at pH 5.5 and pH 6.5 PEG detachment within 1 h was determined as 80%, and 50%, respectively. PEG detachment of the polymer was through simultaneous cleavage of the hydrazine (CON) and hydrazone (NC) bonds, depending on pH, thus the polymer is more pH-sensitive than those with a hydrazine bond only. The grafting densities of PEG-Hz-CHEMS on CL-pPSL were optimised to achieve a PEG density of 1.7% (mol). The unilamellar CL-pPSL (123 nm) were shown to be sable at least for 3 months at 4 °C and have enhanced pH-sensitivity compared with pPSL in the calcein leakage assay. Therefore, the smart cleavable PEG polymer is promising in liposome formulation to overcome the PEG dilemma.
为了促进聚乙二醇（PEG）可切割的 pH 敏感脂质体（CL-pPSL）的发展，本研究旨在全面表征一种新的 pH 敏感聚合物，PEG-Hz-CHEMS。聚乙二醇（PEG）通过酸不稳定的腙-腙混合键（CONHNCH）与胆固醇半琥珀酸酯（CHEMS）连接，形成 PEG-Hz-CHEMS。将聚合物后插入 DOPE/CHEMS 脂质体中形成 CL-pPSL。在多线性回归的帮助下，建立了一种经验证的、适用于该移动相的稳定性指示 HPLC-UV 方法。该分析方法用于评估聚合物的 pH 敏感性、切割途径和 CL-pPSL 的 PEG 化程度。通过钙黄绿素渗漏试验比较了 CL-pPSL 与传统的 PEG 化 pH 敏感脂质体（pPSL）的 pH 敏感性。在 37°C 下，PEG-Hz-CHEMS 在 pH 7.4 时相对稳定，半衰期为 24 小时。相比之下，在 pH 5.5 和 pH 6.5 下，PEG 分别在 1 小时内的脱落率为 80%和 50%。聚合物的 PEG 脱落是通过同时切割腙（CON）和腙（NC）键完成的，这取决于 pH，因此该聚合物比仅具有腙键的聚合物更敏感。优化了 CL-pPSL 上 PEG-Hz-CHEMS 的接枝密度，以实现 PEG 密度为 1.7%（摩尔）。证明具有 123nm 平均粒径的单层 CL-pPSL 在 4°C 下至少稳定 3 个月，并且在钙黄绿素渗漏试验中与 pPSL 相比具有更高的 pH 敏感性。因此，智能可切割的 PEG 聚合物在脂质体配方中很有前景，可以克服 PEG 困境。
