Effect of pre-freezing rate on porosity ratio and mechanical property of pig aorta.

Vacuum freeze-dried blood is a good material for vascular grafts. However, studies on this technology are few, particularly on physical performance change of freeze-dried blood vessel at different pre-freezing rate. In our study, pig aortas were non-invasively scanned by micro-CT in each stage of freeze-drying at different pre-freezing rates, then comparing the porosity ratio and grey level under different conditions with each other to analysis the influence of different methods on the aorta. The mechanical properties of rehydrated pig aorta and fresh one were compared by texture profile analyzer to investigate the influence of different pre-freezing rates on mechanical properties in pig aorta. Our results showed that the proper pre-freezing rate for freeze-drying were 1 C/min. The changing rates of porosity rate and the average gray scale value were 16.6% and 3.64% respectively after freeze-dried. The puncture tolerance (PT) and circumferential tensile stress were increased about 20% and 30% respectively, and the axial tensile stress (ATS) were decreased about 20% in rehydrated aorta compared with fresh aorta. We otherwise conclude that under optimized process conditions, freeze-dried aorta with proper porosity rate and mechanical properties approximate fresh aorta could be preparation.