title: Characterization of Pegylated Liposomal Mitomycin C Lipid-Based Prodrug (Promitil) by High Sensitivity Differential Scanning Calorimetry and Cryogenic Transmission Electron Microscopy.
abstract: 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.
authors.affiliation: Laboratory of Membrane and Liposome Research, The Hebrew University-Hadassah Medical School, IMRIC , Jerusalem, Israel.|School of Pharmacy, Shanghai Jiao Tong University , Shanghai, China.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Wei
authors.affiliation: Oncology Institute, Shaare Zedek Medical Center , Jerusalem, Israel.|Hebrew University-School of Medicine , Jerusalem, Israel.
authors.forename: Yogita
authors.initials: Y
authors.lastname: Patil
authors.affiliation: Lipomedix Pharmaceuticals , Jerusalem, Israel.
authors.forename: Patricia
authors.initials: P
authors.lastname: Ohana
authors.affiliation: Lipomedix Pharmaceuticals , Jerusalem, Israel.
authors.forename: Yasmine
authors.initials: Y
authors.lastname: Amitay
authors.affiliation: Oncology Institute, Shaare Zedek Medical Center , Jerusalem, Israel.
authors.forename: Hilary
authors.initials: H
authors.lastname: Shmeeda
authors.affiliation: Oncology Institute, Shaare Zedek Medical Center , Jerusalem, Israel.|Hebrew University-School of Medicine , Jerusalem, Israel.|Lipomedix Pharmaceuticals , Jerusalem, Israel.
authors.forename: Alberto
authors.identifier: 0000-0001-9924-3149
authors.initials: A
authors.lastname: Gabizon
authors.affiliation: Laboratory of Membrane and Liposome Research, The Hebrew University-Hadassah Medical School, IMRIC , Jerusalem, Israel.
authors.forename: Yechezkel
authors.initials: Y
authors.lastname: Barenholz
mesh_terms: D002152:Calorimetry, Differential Scanning; D002626:Chemistry, Pharmaceutical; D004355:Drug Stability; D008081:Liposomes; D046529:Microscopy, Electron, Transmission; D016685:Mitomycin / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry; D044367:Phase Transition; D011092:Polyethylene Glycols / Q000737:chemistry; D011355:Prodrugs / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D008081:Liposomes; D011355:Prodrugs; D011092:Polyethylene Glycols; D016685:Mitomycin
keywords: DSC; lipophilic drug; liposome; mitomycin C; nanoparticle; phase transition; prodrug; thermodynamics