Study On The Drug Delivery System Of LHRHa Modified Liposomes Targeting To Human Ovarian Tumor Cells

Malignant ovarian cancer, with a very high motality, has been one of the three most dangerous ones. Inspite of the advanced surgical technology and new anti-tumor agents there are still 60 percent with bad prognosis or even recurrence. The ultimate success of chemotherapy depends on the prevention of adverse drug side effects to healthy organs, which may be solved by the presence of targeting drug delivery system.luteinizing hormone-releasing hormone (LHRH) is a linear hypothalamic decapeptide, the receptor of which expressed on 70 to 80 percent of ovarian tumor cells but rarely on normal tissues within body. In recent research LHRH and whose analogues LHRHa were found to combine specifically with LHRH receptors. The half life of LHRH within body was rather short to 2 to 3 minutes but if the 6^th and the 10^th amino acids in which were substituted or knocked down the result nonapeptide would possess a 5-hour-half life and an equal combine efficiency with the receptor. Thus recent research focused on the active targeting drug delivery system with LHRHa as targeting moiety, which may deliver chemotherapies specifically to ovarian tumors and eliminate adverse effects and surrounding toxicities.Strategies of drug targeting by targeting moieties may be: 1) combine targeting moiety covalently with drugs, the so called targeting prodrugs. 2) combine targeting moiety covalently with drug delivery systems, which would carry drugs loaded specifically to targeting organs. 3) targeting moiety being electrically adsorped on surface of drug delivery system, which could also deliver drugs or therapeutic gene to targeting organs.In the present study the negative charged lipid materials were involved to form anionic liposomes which can adsorp positively charged targeting moiety: LHRHa.Docetaxel is obtained by semisynthesis from a noncytotoxic precursor, the needles of the European yew tree. There is evidence that docetaxel is active in platinum-resistant and paclitaxel-resistant ovarian cancers. Docetaxel currently is being evaluated as a component of first line combination chemotherapy for ovarian cancer. In the present study docetaxel was chosen as candidate of the ovarian tumor cell targeting drug delivery system.In this research negatively charged cholesterol succinimide (CHS) was synthesized to substitute cholesterol in the preparation of docetaxel loaded liposomes. The film-ultrasonic method was chosen as preparation method and the entrapment efficiency was determined according to the method of dialysis. According to single-factor experiments factors influencing the preparation mostly were found out followed by a central component design to optimize the liposome preparation. The result optimum liposome was unique 342nm-diameter vesicas with an entrapment efficiency of 91.34%, a loading efficiency of 20.49%, a PDI of 0.255 and a zeta potential of -31.9mV. 1/2 amount to CHS (molar to molar) of LHRHa was involved in the formation of LHRHa-Doc-Lipo. In order to improve stability of the preparation 2% (m/V) of glucose, lactose and mannitol respectively were chosen as supporting agents to prepare lyophilized liposomes. According to a primary stability study the lyophilized liposome was stable for at least 3 months in condition of 4℃or -20℃.In-vitro cellular uptake study revealed that SKOV3 cell uptake of LHRHa-aided fluorescence liposome were of 1.5～2 times of normal fluorescence liposome but other tumor cells showed on difference according to the two. It can be verified that the targeting efficiency was unique for ovarian tumor cells.In order to do further research on targeting efficiency in-vivo evaluation was carried out and in-vivo docetaxel determination method was established. Results of in-vivo drug distribution, evaluated with total organ concentration percentage and total administration dosage percentage, indicated concentration of docetaxel in tumor via LHRHa-Doc-Lipo administration was higher than that of Doc-Lipo or docetaxel admistration and the concentration of docetaxel in liver and kidney had also been reduced.In conclusion the established LHRHa-Doc-Lipo drug delivery system with an improved drug loading efficiency revealed a high in-vitro and in-vivo targeting efficiency. In may prove to be a potential active targeting chemotherapy delivery system.