盐酸表柔比星长循环热敏冻干脂质体的处方工艺研究与体外释药机制探讨

Formulation and preparation of epirubicin hydrochloride long-circulating thermosensitive freeze-dried liposomes and the drug release mechanism in vitro

目的研究盐酸表柔比星长循环热敏冻干脂质体(EPI-LTSL)的处方工艺,并探讨其体外释药机制。方法pH梯度法制备EPI-LTSL并进行冷冻干燥,正交试验优化处方,单因素试验优化工艺。通过观察不同温度下EPI在不同介质中形成沉淀的性状,探索EPI-LTSL的体外释药机制。结果最佳处方及工艺为药脂比1∶10,DPPC/MSPC为82∶8,水化介质为250mmol/L柠檬酸盐(pH4.0)。空白脂质体经15000psi(103MPa)高压均质循环5～6次,100nm聚碳酸酯膜挤压过膜3次;调节脂质体外相pH后,35℃水浴20min载药。冻干脂质体内外相乳糖浓度为9%,采用中速预冻(-65℃)及缓慢的解吸干燥可以制备较好的冻干品。EPI与柠檬酸盐形成的沉淀在42℃可以完全溶解,而在25℃成絮状或片状沉淀。结论制备的EPI-LTSL载药量和包封率较高,粒径较小。冻干脂质体外观平整,内部疏松多孔,色泽鲜亮,复水迅速且粒径变化较小。以柠檬酸盐为水化介质制备的EPI-LTSL,在25℃时包载于脂质体内相的EPI以沉淀稳定存在,而在42℃时可完全溶解释放出来。

Objective To study the formulation and preparation of epirubicin hydrochloride long-circulating thermosensitive freeze-dried liposomes（EPI-LTSL）and investigate the mechanism of drug release in vitro.Methods EPI-LTSL was prepared by pH gradients methods and lyophilization.The formulation and the preparation technique were polished using orthogonal experiment and single factor design,respectively.The properties of EPI in different media were observed to explore the drug release in vitro.Results The optimal formulations and preparation technique were as follows：drug∶lipid was 1∶10（w/w）,DPPC/MSPC was 82∶8（mol/mol）,and the hydration medium was 250 mmol/L（pH 4.0）citrate buffer solution.The blank liposomes were homogenated for 5-6 times at 15 000 psi,and then extruded through 100 nm membrane 3 times.After adjustment of the pH of liposome,the drug was loaded at 35℃ in a water bath for 20 min.The concentrations of lactose in both inner and outer phases of the freeze-drizd liposomes were 9%.Both medium speed pre-freezing（-65℃）and slow first-drying were beneficial to producing lyophilized liposomes with good morphology.At 42℃ the precipitate formed by the reaction of EPI and citrate buffer solution dissolved completely,but it was flocculent or flake-like at 25℃,which suggested incomplete dissolution at this low temperature.Conclusion EPI-LTSL is prepared using the optimized process and possesses excellent properties such as high drug-loading capability,high encapsulation efficiency and small sizes.The freeze-dried liposomes have smooth appearance,porous inner structure and are bright red in color.Only a small amount of drug is released during the fast rehydration of freeze-dried liposomes with water,while the particle size of liposomes remain rearly unaltered.The hydrated EPI-LTSL with citrate buffer are stable at 25℃ because the loaded drug is precipitated in liposomes.When the temperature is raised to 42℃,the encapsulated EPI precipitate is released completely with the aid of dissolution.