Freeze-drying of Liposomes and Its Effect on Retention Rate of Encapsulated Pharmaceticals

The glass transition temperature (T g) of liposomal suspensions,in which glucose,sucrose,mannitol and trehalose are used as cryoprotectants respectively,are measured by differential scanning calorimetry (DSC),the protective effect of the cryoprotectants added for liposomes during freeze-drying is investigated.The results show that the T g of liposomal suspension with trehalose is the highest,while that with glucose is the lowest.Depending on the concentration,the vesicle size of liposomes with trehalose as cryoprotectant varies less,while the vesicle size of liposomes,with glucose as cryoprotectant varies bigger during the process of freeze-drying.The pharmaceuticals of water-soluble ftorafur and lipid-soluble vitamin A encapsulated in liposomes are freeze-dried.The retention rates of the encapsulated pharmaceuticals inside the liposomes are measured with a high performance liquid chromatography.The results indicate that the retention rate for liposomes with trehalose is the highest,and the leakage of the pharmaceuticals is less than that with glucose being cryoprotectant.Through a series of study,trehalose is identified as a better cryoprotectant and an optimized freeze-drying procedure for liposomes is obtained.