Preparation Of Medium-Chain Fatty Acid Liposomes

As an important delivery system, liposome can enhance the stability, the bioavailability and targeting of the preparation. Compared to long chain fatty acids, medium-chain fatty acids (MCFA) have the characteristics of fast resorption,no cumulation and almost all the acids as the energy sources,etc. This paper aimed at studying the preparation process of MCFA liposome and evaluate its quality.We used the particle size distribution ,the Zeta potential and the Entrapment Efficiency (EN%) as the main estimating indexes to evaluate thin film-supersonic method , reverse phase evaporation vesicle method, modified ethanol injection-extrude method and microemulsion cooling method . The experimental results indicated that the thin film-supersonic method was better than other methods. The optimal preparation conditions of MCFA liposome were as follows : the ratio of soybean phosphatidylcholine and cholesterol was 3:1; the proportion of medium-chain fatty acid and lipids in weight was 1:10 ; the ratio of Tween-80 and total lipids was 3:10 and the optimal temperature was 35℃. In the optimal condition ,the mean particle size of liposome was 240.4±20.3 nm, the Zeta potential was -52.27±3.2mV and the encapsulation efficiency could reach 82.90%.The process of the dynamic ultrahigh pressure microfluidizer method to prepare the MCFA liposomes was studied. The results indicated that the best preparation process of MCFA liposome was to homogen 2 times at 100MPa. The concentration of soybean phosphatidylcholine was 3%-4% and the proportion of medium-chain fatty acid and lipids in weight was 1:10. In the optimal condition , the encapsulation efficiency was 71.52%, the mean particle size of liposome was 85.0±36.3 nm and the Zeta potential was -57. 70±2.1mV.MCFA liposome was prepared by lyophilization, the freezing-dry processing techniques was studied on and the type and quantity of the cryoprotectant were sceened. The results indicated that the best preparation conditions of freezing-dry MCFA liposome were as follows : the sucrose and mannitol were used as cryoprotectant and the ratio of sucrose : mannitol : soybean phospholipid was 1.5:1:1, and 48h was chosen as the drying time at the temperature of -80℃and under the vacuum of 0.1mbar. The mean diameters were 250.1±13.2nm and 263.3±21.6nm, the Zeta potential was -44.93±2.5 mV and -43.02±1.2mV and the entrapment efficiencies were 81.3% and 79.2% for freshly prepared and reconstituted liposomes,respectively. It suggested that the freezing-dried liposome could keep the original property.