Preparation and Evaluation of Two Tumor Targeted Liposomal Chemotherapeutic Agents
|School||Huazhong University of Science and Technology|
|Keywords||Liposome Targeted efficiency Folate receptor Gefitinib Doxorubicin Pharmacokinetics|
Recently, liposomes have attracted considerable attention as a novel drug delivery. However, traditional liposomes have disadvantages in low encapsulation efficiency of hydrophobic drugs and easy elimination by reticuloendothelial system, which could reduce the drug efficiency. Therefore, it is one of the tendencies to develop novel liposomal therapeutic agents with high encapsulation efficiency and advanced targeting efficiency.The study includes two parts, which learned the effects of the two liposomal therapeutic agents on circulation time and tissue distribution. In the first part of the research, the effects of drugs-in-cyclodextrins-in-liposome technology on drug efficiency were investigated. Gefitinib (GEF) was chosen as the model drug, and GEF-in-cyclodextrins-in-liposome was prepared. Furthermore, the physical and chemical characteristics, in vitro release and pharmacokinetics of the liposomes were studied. In the second part, folate targeted liposomes were studied. A novel ligand, folate-CONH-PEG-NH-Cholesterol, has been synthesized. Doxorubicin was taken as the model drug, and a folate targeted doxorubicin liposome (F-DOX-L) with the novel ligand was prepared. Then, studies on the characteristics, in vitro release, pharmacokinetics and tissue distribution were carried on.In the first part, the methodologies of determining GEF in liposomes and plasma samples by UV-Vis spectrophotometry and fluorescence spectrophotometry were established separately. GEF liposomes were prepared and the effects on the encapsulation efficiency were investigated. The formulations of GEF liposomes preparation were EPC/Chol/mPEG-DSPE (55:40:5) and HSPC/Chol/mPEG-DSPE (55:40:5) followed by hydration with0.3M (NH4)2SO4and0.1M HPβCD. The encapsulation efficiency of two liposomes were98.1±0.8%and85.5±1.2%, respectively. And the particle size were136.2±12.4nm and155.4±14.9nm. The release amounts of two liposomes in72h were less than40%. The formulations were stable in4℃for30days. The results of cytotoxicity showed that the IC50of two liposomes were15and20times those of GEF solution.In the pharmacokinetics studies, GEF concentrations were determined after i.v. GEF solution and liposome. Ti/2β, MRT and AUC of GEF liposome were3.23,3.91,6.22times those of GEF solution, which indicated that drugs-in-cyclodextrins-in-liposome could extend the circulation time of the drug, and increase the drug concentration in plasma.In the second part, a novel ligand folate-CONH-PEG-NH-Cholesterol was synthesized followed the structure confirmed by MS. F-DOX-L/DOX-L and F-Calcein-L/Calcein-L were prepared with the novel ligand. And the uptake of calcein liposomes were studied in KB, Hela and SMMC-7721. The results of fluorescence microscope and flow cytometry showed that folate-targeted calcein liposomes were selectively uptake by KB and Hela, and the targeted efficiency could be eliminated by free folic acid. However, no difference was observed between the uptake of fo late-targeted calcein liposomes and calcein liposomes in SMMC-7721. In MTT assay, cytotoxicity of DOX formulations was determined in KB and Hela cells. The results showed that compared to free DOX solution, GEF liposomes showed much lower cytotoxicity.In the pharmacokinetics studies, DOX concentrations were determined after i.v. free DOX, DOX-L and F-DOX-L. It is found that drug concentration in plasma in liposome group was much higher than free DOX group. Furthermore, in the study of tissue distribution, the results showed that drug in liver in DOX liposome group was much less than in free DOX group in the first30min, and the liposome showed targeted efficiency to liver and spleen.