Design and evaluation of pH-sensitive liposomes constructed by poly(2-ethyl-2-oxazoline)-cholesterol hemisuccinate for doxorubicin delivery

• Published in: European journal of pharmaceutics and biopharmaceutics 2015-04, Vol.91, p.66-74
• Main Authors: Xu, Huan, Hu, Meina, Yu, Xiu, Li, Yan, Fu, Yuanshan, Zhou, Xiaoxia, Zhang, Di, Li, Jianying
• Format: Article
• Language: English
• Subjects: Antibiotics, Antineoplastic - administration & dosage; Antibiotics, Antineoplastic - chemistry; Antibiotics, Antineoplastic - pharmacology; Biological Transport - drug effects; Cell Line, Tumor; Cell Nucleus - drug effects; Cell Nucleus - metabolism; Cell Nucleus - pathology; Cell Survival - drug effects; Cholesterol - analogs & derivatives; Cholesterol - chemistry; Cholesterol Esters - chemical synthesis; Cholesterol Esters - chemistry; Cholesterol hemisuccinate; Doxorubicin - administration & dosage; Doxorubicin - chemistry; Doxorubicin - pharmacology; Drug Delivery Systems; Drug Liberation; Endocytosis - drug effects; Endosomes - drug effects; Endosomes - metabolism; Endosomes - pathology; Humans; Hydrogen-Ion Concentration; Liposomes; Melanoma - drug therapy; Melanoma - metabolism; Melanoma - pathology; Membrane Fusion - drug effects; Microscopy, Confocal; Molecular Structure; Particle Size; PEG dilemma; PEGylation; pH-sensitive; Poly(2-ethyl-2-oxazoline); Polyamines - chemical synthesis; Polyamines - chemistry
• ISSN: 0939-6411; 1873-3441
• DOI: 10.1016/j.ejpb.2015.01.030

[Display omitted] •Poly(2-ethyl-2-oxazoline)-cholesterol hemisuccinate (PEtOz-CHEMS) was synthesized and characterized.•PEtOzylated liposomes showed good pH-sensitivity.•PEtOz can help liposomes achieve “endosomal escape”.•PEtOzylation can avoid the “PEG dilemma” of PEGylated liposomes to some extent. In this study, a novel material, poly(2-ethyl-2-oxazoline)-cholesterol hemisuccinate (PEtOz-CHEMS), was synthesized to construct pH-sensitive liposomes. The structure of PEtOz-CHEMS was confirmed by thin-layer chromatography, Fourier transform infrared spectroscopy, and 1H NMR. Anticancer fluorescent drug doxorubicin (DOX) was encapsulated into the liposomes. Compared with conventional liposomes (CL), CHEMS modified liposomes (CH-L) and PEGylated liposomes (PEG-L), the PEtOzylated liposomes (PEtOz-L) showed an acidic pH-induced increase in particle size. At pH 6.4, the heme release of PEtOz-L group was close to that of the positive control group, whereas that of CL, CH-L and PEG-L was close to that of the negative control group. In vitro drug release studies demonstrated that DOX was released from PEtOz-L in a pH-dependent manner, and the release of DOX from conventional DOX liposomes (CL-DOX), DOX loaded CH-L (CH-DOX-L) and PEGylated DOX liposomes (PEG-DOX-L) had no pronounced differences under each pH medium. In vitro cellular uptake assays showed that PEtOz-DOX-L indicated a significant fluorescence intensity at pH 6.4 compared with at pH 7.4. CL-DOX, CH-DOX-L and PEG-DOX-L did not achieve any obvious diversity at different pH conditions. Confocal laser scanning microscopy images showed that PEtOz-DOX-L can fuse with the endosomal membrane under acidic conditions of endosome, release DOX into the cytoplasm, then gather into the nucleus. Therefore, PEtOz can help liposomes achieve “endosomal escape”. The in vitro cytotoxicity experiment results on A375 cells showed that PEtOz-DOX-L resulted in lower cell viability than CL-DOX, CH-DOX-L and PEG-DOX-L under low pH conditions. These results confirm that the pH-responsive PEtOz was a promising material for intracellular targeted delivery system and might be used for overcoming the “PEG dilemma”.