| The pre-formula study and screening of formula and preparation process were done to prepare docetaxol liposome which was then modified into long-circulation liposome by PEG2000-DSPE. By the adding of lyo-protectant, the two kinds of liposome were lyophilized. The object of this paper was to prepare docetaxol liposome with high drug-lipid ratio and encapsulation efficiency and with good stability. Besides, we modified the conventional liposome to improve its in-vivo stability.The in-vitro analyzing method of docetaxol liposome was established. The apparent solubility of docetaxol in pH 6.8 phosphate buffer solution was determined to be 10.23μg/mL and the lgP was determined to be about 2.6. The methods of ultra filtration and dialysis were developed to determine the encapsulation efficiency, which showed that both methods had been with high recovery and could be applied for the determination.Considering the properties of the drug, the methods of thin-film dispersion and alcohol injection were tried to prepare the liposome respectively and finally the former method was chosen for the preparation of both liposome. The optimized preparation process and formula were as follows: absolute alcohol was used as the solvent and the preparation temperature was 40℃; the ratio of HSPC to PC (w/w) was 2:1, while the ratio of cholesterol to lipid (w/w) was 1:8, the ratio of tween80 to lipid (molar ratio) was 1:100, the drug-lipid ratio (w/w) was 1:12; PEG2000-DSPE was chosen to be the long-circulation decorating material. The method of high pressure homogenizing was used to treat the liposome, which gave us liposome with narrow particle size distribution and small mean diameter.The characters of the prepared conventional liposome and long-circulation liposome were investigated, which gave us the mean diameter of 136 nm and 126 nm respectively,ζpotential of -7.3 mv and -18.1 mv respectively. The encapsulation efficiency of the two liposomes determined by ultra filtration was 98.6% and 99.3% respectively. The sudden-release effect and in-vitro release profile of conventional and long-circulation liposome were studied. The sudden-release effect of both liposomes was in line with the regulation of ChP. The in-vitro release of long-circulation liposome was slower than that of conventional liposome. The stability of both liposome suspensions was investigated, which indicated that it was necessary for them to be freeze-dried to get better in-vitro stability.The impacts of lyophilization process and lyo-protectant on the freeze-dried product were studied, with the appearance, particle size and encapsulation efficiency after reconstituted as index. Mannitol/ mycose (w/w, 1:1) was chosen as lyo-protectant and the ratio of lyo-protectant to lipid was 3:1 (w/w). The optimized freeze-drying process was as follows: freezing temperature was -70℃, freezing time was 2 h and drying time was 30 h. The investigation on both freeze-drying products showed that there were no obvious changes with both liposome in particle size,ζpotential, encapsulation efficiency and content before and after freeze-drying. Accelerating stability test show that both liposome freeze-drying products were stable at the temperature of 25℃±2℃and relative humidity of 60%±10% for 3 months.The method of HPLC was developed for the analyzing of drug in rat plasma. Through the investigation of liposomes’ in-vivo pharmacokinetics in rats, the ratio of PEG-DSPE to conventional lipid was obtained to be 4% (molar ratio). The pharmacokinetic parameters of docetaxol injection, conventional liposome and PEGylated liposome in rats were compared, which show that the pharmacokinetic parameters of PEGylated liposome were obviously different from that of the other two preparations. |
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