Study On Long - Circulating Liposomes Of Curcumin For Injection

Recent studies have revealed that curcumin（Cur） exhibited various pharmacological activities, which includes: anticarcinogenic effect, anti-inflammatory effect. anti-HIV activity, anti-oxidant activity and apoptosis induction. It has been reported that Cur can influence each phase of the tumor growth（initiation、promotion and progression） and has inhibitory effect on infiltration and metastasis by means of inhibition the tumor angiogenesis. However, Cur can not be dissolved in water and can also be oxidized easily in vitro, there has been few drug preparation with good stability. Besides, In vivo studies have revealed that small amount of Cur can be detected in plasma after oral administration. These bring difficulties in the clinical application of Cur. Our research focus on the preparation of the long-circulating liposome which can prolong the retention time of the Cur and enhance its therapeutic activity.Firstly, two analytical methods were founded to determine the drug content: the ultraviolet spectrophotometry （UV） and the high performance liquid chromatography （HPLC）. The UV spectrophotometry was selected to set out the drug content in the determination of the encapsulation efficiency; the HPLC was mainly used to set out the drug content in the study of the physicochemical properties of Cur and the release behavior of Cur liposome（Cur-L）. the liposome and the free drug was separated by mini-column centrifugation.Secondly, the research investigated three main physicochemical properties of Cur: the stability of Cur in different phosphate buffer solution （PBS） with various pH value revealed that the optimum pH value for Cur was below 7.0. The solubility and oil/water partition coefficietnt the oil/water partition coefficietnt of Cur in different PBS with various pH value showed that Cur was an anticancer drug with good liposolubility. Basing on its good liposolubility the Cur-L should have high encapsulation efficiency.Thirdly, on the basis of preliminary experiments, taking the encapsulation efficiency as index, determined Cur-L preparation methods and then adopted the single factor prescription for the identification of factors affecting Cur-L. The Cur-L was prepared by ethanol infusion. The weight ratio of Cur to SPC, the weight ratio of SPC to Chol, the pH of buffer solution and the iron strength of water phase were the main factors affecting the encapsulation efficiency. On this basis, four factors and three levels orthogonal design was employed to screen best prescription. As a result, the best prescription is: the weight ratio of Cur to SPC is 1:13, the weight ratio of SPC to Chol is 3:1, the pH of buffer solution is 5.0 and the iron strength of water phase is 20 mmol·L^-1. Though the same method we also gain the best prescription of the curcumin long-circulating liposome （Cur-PEG-L）: the weight ratio of Cur to SPC is1:13, the weight ratio of SPC to Chol is 5:1, the weight ratio of PEG2000-Chol to SPC is 5%（mol/mol）, the pH of buffer solution is 5.0 and the iron strength of water phase is 20mmol·L^-1.Finally, Cur concentration in plasma was determined after i.v. of Cur-injection, Cur-L and Cur-PEG-L in rats and Cur concentration in heart, liver, spleen, lung, kidney and brain were determined after i.v. of Cur-injection, Cur-L and Cur-PEG-L in mice. After i.v. injection into the tail vein of rats, Cur plasma concentration of Cur-L and Cur-PEG-L were higher than that of Cur-injection at each sampling time. Cur-PEG-L prolonged circulation time and increased bioactivity of Cur. MRT and AUC of it were 10.6 and 9.311 times higher than those of Cur-injection; after i.v. injection into tail vein of mice, Cur-L and Cur-PEG-L also showed longer elimination time in every tissue. Cur-L accumulated in endothelial system （RES）, r_e of it in liver and spleen significantly higher than Cur-PEG-L. Cur-PEG-L significantly reduced phagocytosis of RES and showed lung targeting effect. To summarize Cur-PEG-L could prolong the circulation time of Cur in vivo and had the lung targeting effect. It was a promising carrier to increase therapeutic effect of Cur in treating lung cancer.