ABSTRACT
BACKGROUND:Mechanical properties of the blood vessels include axial and radial tension which is important to guarantee the tissue perfusion and its pressure. OBJECTIVE:To test and analyze stretching and puncture parameters that can ful y characterize the performance of blood vessels, so as to predict the health condition of the vessels transplanted into recipients. METHODS:Mechanical properties as circumferential tension, axial tension and puncture were tested on the porcine aorta, and then pathological and staining analysis was done to explore whether freeze-dried vessels can withstand the blood pressure in al directions after transplanted into the body. RESULTS AND CONCLUSION:Specific trend on the curves of freeze-dried vessels during circumferential tension, axial tension and puncture process was closer to that of fresh vessel curves, suggesting that structural components and arrangement of the freeze-dried vessels were not changed greatly. Meanwhile, the microscopic observations of slice and tensile section were taken into account so that the reason was studied and explained for the mechanical properties of the experimental data and results. The macroscopic mechanical result was analyzed based on the change of microstructure. These findings indicate that the vacuum freeze-drying is a better method to maintain the performance of blood vessels.
ABSTRACT
Pig aortic vessels were processed by vacuum freeze-drying and then the aotic vessels were scanned and compared by CT, microscopic and texture analyzer. These processes presented a new method for preserving the vessels. Morphological changes of the vessels were tracked by Micro-CT, and mechanical properties were compared by texture analyzer combining with microscopic observation for structures and tissues. Results showed that the wall of the vessels became thinner by freeze-drying. After rehydration, the membrane structure was generally maintained, and the elastic fibers were more orderly arranged so that they were close to fresh vessels. In the area of mechanical property, the maximum puncture stress and axial tensile stress of rehydrated blood vessels were stronger than that of the fresh, while circumferential tensile stress was weaker than that of the fresh. Finally, analysis also showed that the freeze-dried vessel was basically remained the original morphological structure. The pores in vessel fiber and stratification during drying may be beneficial to the host cell invasion and angiogenesis, so it is expected to be a new effective means to save the blood vessels. Currently, four pigs have been transplanted with the rehydrated vessels, and all of the four have survived for more than 3 weeks.
Subject(s)
Animals , Aorta , Freeze Drying , SwineABSTRACT
BACKGROUND: Previous studies demonstrated that freeze-drying had great influence on internal heat transfer, such as pore distribution and void connectivity, however, the mechanisms involved in heat and mass transfer during drying is poorly understood.OBJECTIVE: Based on the previous studies, micro CT was served as analytical tool, to observe the movement characteristics of sublimation interface in freeze-drying process.METHODS: With aorta of pig, micro-CT scanning, image reconstruction and the technique of grey value analysis were used to observe and analyze the sublimation process in freeze-drying. RESULTS AND CONCLUSION: The slope of freeze-drying temperature curve was large at first, causing quick sublimation rate. The grey value of freeze-drying and ice crystal area was very different in second-dimensional cross-sectional reconstructed image.Sublimation interface was clear and sublimation took place simultaneously both in the outer'surface and inner surface. The movement of sublimation interface was obvious at this time. Along with the time, the slope of freeze-drying temperature curve became small, leading to slow sublimation rate. The movement of sublimation interface turned unciearly.For the vertically placed artery, when heated at the bottom, the sublimation takes place both in the outer surface and inner surfaceat the same time. The sublimation interface slowly approaches to the middle of vessel wall. With time prolonged, resistance for heat and mass transfer in freeze-drying is increased, and the sublimation rate becomes slowly.
ABSTRACT
BACKGROUND: The freeze-drying blood vessel is an excellent material for vasotransplantation. However, the reports concerning freeze-drying are few, and the mechanical property changes of freeze-dried blood vessel remains poorly understood. OBJECTIVE: Using micro-CT to explore the morphological changes of blood vessel during procedure of freeze-drying. DESIGN, TIME AND SETTING: A single sample observation was performed at the Institute of Refrigeration and Cryogenics, University of Shanghai for Science and Technology. MATERIALS: Fresh pig aorta was obtained from Shanghai Slaughter House. The lyophilizer was produced by SP Industries (USA). TRAPEZIUM LITE texture analyzer was purchased from Shimadzu (Hong Kong) Co., Ltd.METHODS: The differences of mechanical property between fresh aorta and freeze-dried aorta were compared.MAIN OUTCOME MEASURES: ① Temperature curve of freeze-drying procedure. ②The reeze-drying procedure was scanned by micro-CT. ③ Changes of mechanical property were detected by TRAPEZIUM LITE texture analyzer and puncture experiments.RESULTS: During freeze-drying procedure, there were presented layer phenomenon in pig aorta. Compared to the fresh aorta, the freeze-dried aorta after recover water would reduce 40% axial tensile force, increase 45% circumferential tensile force, with 75% puncture stress.CONCLUSION: The freeze-dried blood vessel maintains mechanical property as fresh vessel, thus, freeze-drying can be used for vascular preservation.