Experimental study on improvement of freeze-drying process for porcine aorta

Freeze-drying is an effective method for preservation of aortas. In order to maintain the original properties of aortas, the sublimation drying process requires accurate monitoring. In this study, we used a contactless mass measurement device to monitor drying process, porcine aortic segments were divided into four series for freeze-drying, then relevant experiments and calculations were carried out to evaluate the quality of lyophilized samples. The study found that the sublimation process could not be accurately monitored by measured temperature, however, the real-time weighing could do it well, and was suitable to judge the endpoint of primary drying. Meanwhile, the change law of sublimation temperature was obtained by quasi-steady heat transfer equations. The removal ratio of free water during the primary drying greatly affected the properties of lyophilized samples, thorough sublimation had contributed to better performance of products, especially in mechanical properties. In addition, compared with annular aortic segments, the flaky samples had better heat transfer and performed better in histological scanning.