Study On Foam Freeze Drying Of Vaccine

Vaccine is one of the most effective means to prevent diseases. Freeze drying is a common technology for vaccine production. Foam freeze drying is a new technology for vaccine drying, in which the sample is foamed before freezing by addition of foaming agent into the formulation. Compared with traditional freeze drying method, the specific surface area of material is significantly larger after foaming. Therefore the mass transfer velocity is improved, and the elapsed time of primary drying and second drying is shortened. The production efficiency is thus increased and the manufacturing cost is reduced. The heat-resistant property of vaccines made by foam freeze drying is very good, so their storage life is prolonged, and the device requirements for storage and transportation are lowered.To make the technology of foam freeze drying more practical, experiments were carried out on a self-made freeze dryer to study the protective agent formulation and the operation parameter. The impact significances of various factors were determined and optimal parameters were found out. As the results, the vacuum during foaming process was the most marked factor for foam height. The foam height was the highest when gelatin(3%wt/vol)+Pluronic F-68(3%wt/vol) was used as foaming agent, vacuum was kept at50Pa and shelf temperature was kept at15℃.On the basis of above mentioned studies, foam freeze drying was used to preserve Newcastle disease vaccine. The samples made by foam freeze drying were analyzed with thermal analysis and EID50test, and compared with live attenuated samples and heat-resistant samples which were prepared by traditional freeze drying. As the results, the cycle time of foam freeze dried (FFD) vaccine was27h, shorter than those of live attenuated and heat-resistant vaccines (72h). The glass transition temperatures of live attenuated vaccine, heat-resistant vaccine and FFD vaccine were32.0℃,40.1℃and33.9℃respectively. The titers decreased after aging test for FFD vaccine and heat-resistant vaccine were1.1and0.8respectively. It is shown that FFD vaccine has its own superiority on heat resistance. It is worthy to carry out further work on the foam freeze drying of vaccine.