Freeze-Drying of Liposomes with Cryoprotectants and Its Effect on Retention Rate of Encapsulated Ftorafur and Vitamin A

Abstract

In this article, the glass transition temperature (T _g ) of liposomal suspensions, in which glucose, sucrose, mannitol, and trehalose are used as cryoprotectants, are measured by differential scanning calorimetry (DSC). The protective effect of the cryoprotectants added for liposomes during freeze-drying is investigated. 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 over a wider range during the process of freeze-drying. Water-soluble ftorafur and lipid-soluble vitamin A encapsulated in liposomes were freeze-dried. The retention rates of the encapsulated pharmaceuticals inside the liposomes are measured with high performance liquid chromatography. The results indicate that the retention rate for liposomes with trehalose is the highest, and the leakage of the pharmaceutical material is less than that with glucose used as a cryoprotectant. Through a series of experimental studies, trehalose is identified as a better cryoprotectant. An optimized freeze-drying procedure for liposomes is presented.

Keywords:

• Cryoprotectant
• DSC
• Freeze-drying
• Ftorafur
• Glass transition temperature
• HPLC
• Liposome
• Vitamin

Acknowledgments

This research has been supported by the key project (No. 59836340) of the National Natural Science Foundation of China.