Laboratory of Membrane and Liposome Research, The Hebrew University-Hadassah Medical School, IMRIC , Jerusalem, Israel.
School of Pharmacy, Shanghai Jiao Tong University , Shanghai, China.
Mol Pharm. 2017 Dec 4;14(12):4339-4345. doi: 10.1021/acs.molpharmaceut.6b00865. Epub 2017 Oct 30.
The effect of a lipidated prodrug of mitomycin C (MLP) on the membrane of a pegylated liposome formulation (PL-MLP), also known as Promitil, was characterized through high-sensitivity differential scanning calorimetry (DSC) and cryo-TEM. The thermodynamic analysis demonstrated that MLP led to the formation of heterogeneous domains in the membrane plane of PL-MLP. MLP concentrated in prodrug-rich domains, arranged in high-ordered crystal-like structures, as suggested by the sharp and high enthalpy endotherm in the first heating scanning. After thiolytic cleavage of mitomycin C from MLP by dithiothreitol (DTT) treatment, the crystal-like prodrug domain disappears and a homogeneous membrane with stronger lipid interactions and higher phase transition temperature compared with the blank (MLP-free) liposomes is observed by DSC. In parallel, the rod-like discoid liposomes and the "kissing liposomes" seen by cryo-TEM in the PL-MLP formulation disappear, and liposome mean size and polydispersity increase after DTT treatment. Both MLP and the residual postcleavage lipophilic moiety of the prodrug increased the rigidity of the liposome membrane as indicated by DSC. These results confirm that MLP is inserted in the PL-MLP liposome membrane via its lipophilic anchor, and its mitomycin C moiety located mainly at the region of the phospholipid glycerol backbone and polar headgroup. We hypothesize that π-π stacking between the planar aromatic rings of the mitomycin C moieties leads to the formation of prodrug-rich domains with highly ordered structure on the PL-MLP liposome membrane. This thermodynamically stable conformation may explain the high stability of the PL-MLP formulation. These results also provide us with an interesting example of the application of high sensitivity DSC in understanding the composition-structure-behavior dynamics of liposomal nanocarriers having a lipid-based drug as pharmaceutical ingredient.
通过高灵敏度差示扫描量热法（DSC）和冷冻透射电子显微镜（cryo-TEM）研究了米托霉素 C 的脂质前药（MLP）对聚乙二醇化脂质体制剂（PL-MLP）（也称为 Promitil）膜的影响。热力学分析表明，MLP 导致 PL-MLP 膜平面中形成不均匀的域。MLP 集中在富含前药的域中，排列成有序的晶体状结构，正如首次加热扫描中尖锐且高焓的吸热所表明的那样。用二硫苏糖醇（DTT）处理将米托霉素 C 从 MLP 中硫代裂解后，观察到 DSC 中无晶体状前药域，并且与空白（无 MLP）脂质体相比，具有更强脂质相互作用和更高相变温度的均匀膜。同时，在 PL-MLP 制剂中观察到棒状盘状脂质体和“亲吻脂质体”消失，并且 DTT 处理后脂质体平均尺寸和多分散性增加。正如 DSC 所表明的那样，MLP 和前药残留的亲脂部分都增加了脂质体膜的刚性。这些结果证实 MLP 通过其亲脂性锚定插入到 PL-MLP 脂质体膜中，其米托霉素 C 部分主要位于磷脂甘油骨架和极性头部基团的区域。我们假设米托霉素 C 部分的平面芳香环之间的π-π 堆积导致在 PL-MLP 脂质体膜上形成具有高度有序结构的富含前药的域。这种热力学稳定的构象可能解释了 PL-MLP 制剂的高稳定性。这些结果还为我们提供了一个有趣的例子，说明了高灵敏度 DSC 在理解具有基于脂质的药物作为药物成分的脂质体纳米载体的组成-结构-行为动力学方面的应用。
