Preparation Of Cisplantin Loaded Sterically Stabilized And Targeted Liposomes, And Its Study On Antitumor Activity

Cervical cancer is one of the most malignant tumors, which is mostly induced by persistent infection of human papillomavirus in cervical cells. Cisplatin(DDP) is a common anti-tumor drug used in the first-line chemotherapy for advanced cervical cancer. Due to its short half-life period cisplatin must be applied in high-dose that results accumulation of the toxicities.This study aims to design a new drug transfer system to increase the concentration of cisplatin in tumor cells and avoid the side effects for normal tissues. Together with estrogen receptors(ER), which are widely overexpressed on cervical cancer cells and act as a potential target for cancer targeted therapy, the modified drug loaded liposomes could specifically target tumor cells and further release chemotherapeutic drugs. Furthermore, the physicochemical characteristic, in vitro targeting and in vitro cytotoxicity of liposomes were investigated.Four types of cisplatin loaded liposomes(DDP loaded conventional liposomes L-DDP, cisplatin loaded targeted liposomes ES-L-DDP, cisplatin loaded sterically stabilized liposomes SSL-DDP and cis-platin loaded sterically stabilized and targeted liposomes ES-SSL-DDP) were prepared via thin film hydration method. The physicochemical characteristics of these four DDP loaded liposomes were investigated, including the morphological examination, particle size, zeta potential,encapsulation efficiency, drug-loading capacity and the stability at 4°C and 25°C. To evaluate the in vivo target effect, the fluorescence intensity of cervical cancer cells Hela treated with Rhodamine B(Rh B) loaded liposomes was measured by fluorescence microscope. By adding different inhibitory agents of endocytosis including sucrose, genistein, amiloride hydrochlorid and ES, the mechanism of cellular uptake was determined. Furthermore, the in vitro anti-tumor efficacy of DDP and the prepared DDP-loaded liposomes was investigated via MTT assay. In vivoimaging, we could observe the effect of sterically stabilized targeting liposome on the tumor location. Anti-tumor experiment was used to observe the tumor killing effect of different formations of cisplatin on tumor bearing nude mice.We observed that, the successfully prepared four types of DDP loaded liposomes obtained average particle sizes below 100 nm and PDI in the range of 0.1~0.2. The zeta potentials of the liposomes showed negative. After storing at 4°C for 48 h SSL-DDP and especially ES-SSL-DDP were obviously more stable than other liposomes. The in vitro targeting test revealed that, ES-L-Rh B and ES-SSL-Rh B were able to actively target to Hela cells, and that ES-SSL-Rh B showed sustainable release effect. The result of inhibition assay of cellular uptake confirmed that, the cellular uptake of liposomes mainly depended on caveolin mediated endocytosis and estrogen receptor-mediated endocytosis. Compare to free cisplatin and other DDP-loaded liposomes, ES-SSL-DDP, which benefited from its sterical stability and ER targeting speciality, obtained the greatest anti-tumor efficacy. In vivo fluorescent image indicated that sterically stabilized targeting liposome had high specificity and efficiency in tumor accumulation. sterically stabilized targeting liposome exhibited significantly higher anti-tumor efficiency in reducing tumor size compared with free drugs combination or single drug-loaded nanoparticles.In this study, we designed and successfully prepared a new type of cisplatin loaded sterically stabilized and ES-modified liposome ES-SSL-DDP, which was able to specifically target the cervical cancer cells and showed high anti-tumor efficiency. We expect that, in the near future this new cisplatin loaded liposome could be applied to clinical treatment and support the cervical cancer therapy.