The Study On Thymopentin Liposomes

Liposome has been accepted into the family of drug delivery system recently with many advantages such as targeting specificity, sustained-release and low level of toxicity in biological systems. It has aroused a widespreaded interest and has many applications in the field of drug research.After a systematic evaluation, a reverse evaporation method was selected to prepare liposome vesicles, which was then used as blank and used in the studies of optimization and stability. The particle size and encapsulation efficacy were the factors considered for optimal prescription of Thymopentin (TP5) liposome. The final thymopentin liposome was found to have partical size of 1.1μm, and the encapsulation rate of 64.8%. Adding vitamin E and freeze-drying were found to improve the stability of thymopentin liposome in vitro. Microscopic observation on the dissoluted freeze-dried TP5 liposome showed a structural integrity.The results of UV evaluation on the concentration changes of TP5 during the prepartion process found no change in TP5 concentration under the conditions of pH 7.0 for 24 hours, or under the ultrasonic power of 200~500W within five minutes. TP5 liposome was found to be stable at 4℃for four days or 37℃for 24 hours in 0.1M PBS pH 7.0 buffer solution. Therefore, the preparation process under the condition of 25°C water bath, pH 7.0, ultrasonic power 300W for five minutes, and to complete the entire process within one hour will not disrupt thymopentin within liposome.In vivo studies indicated that the therapeutic efficacy in terms of leukocyte and percentage of CD3+ and CD4+ in immune defected mice was no significant difference among the group receiving thymopentin liposomes given by gavage ,the group receiving thymopentin given by peritoneal injections , or the group receiving thymopentin given by intra venous injections. This result suggested that the TP5 liposomes prepared was a bioactive formulation.Although the stability of the liposomes still needs to be improved further, our study implicated a favorable prospect in the application of liposomes as oral peptide delivery system.