【作者】 孙冰冰；

【导师】 马学虎；

【作者基本信息】 大连理工大学 ， 化学工程， 2005， 硕士

【摘要】 低温保存技术是一种广泛采用的长时间保存细胞和组织的方法。在许多领域具有重要的应用价值,例如,用低温保存技术贮藏细胞和组织以建立便于临床应用的细胞和组织库,食品的保鲜和贮藏等。在低温保存过程中,在细胞及组织内部,存在复杂的质量传递和热量传递过程,而且是成功冻存成功与否的关键控制步骤。因此,研究细胞及组织在冷冻中的若干问题是优化冷冻方案,理解细胞及组织冻、融机理的关键步骤。本文通过推倒得到了纯水冻结时移动边界问题的解,然后利用流体工程仿真计算软件FLUENT来模拟复杂情况下冻结过程中的热量传递,计算得到冷冻过程中热量传递的情况以及温度和溶液推进的速度分布分布,研究结构对于大尺度组织的冷冻具有指导性的意义。本文还利用微胶珠的多孔结构和可准确测量孔隙率的特点,配制微胶珠悬浮液模拟组织和细胞悬液,实验测定了DMSO在微胶珠内的渗透特性;同时利用图像分析的方法测量了微胶珠的孔隙率。因为在冷冻过程中由于移动边界的存在,迫使保护剂溶液中DMSO溶质进行扩散。如果溶质的扩散速率大于冰晶前锋的推进速率,则在未冻结区域会存在一个浓度分布,反之如果溶质的扩散速率小于冰晶前锋的推进速率,溶质被包埋在冻结区域中并没有梯度存在。本文计算了DMSO在溶液中的扩散系数和温度的关系,并且得到了其在多孔介质内的扩散速率,为进一步研究其冷冻过程中在多孔介质内的输运过程提供了依据。CPA在组织内部的浓度测量一直是组织冷冻过程研究的难题之一。同时本文分别采用了渗透压仪测定不同浓度DMSO溶液的渗透压和色谱仪测量不同浓度DMSO溶液的吸收峰,绘制标准曲线,并进行显著性分析。以此达到间接测量未知DMSO溶液浓度的目的。经过对比分析,实验证明渗透压法是更有效、更方便的检测浓度的方法。对于冷冻过程中使用的其他保护剂都可以使用他们对浓度进行测量。两组实验解决了浓度测量对保护剂溶液性质研究的限制,是值得推荐的方法。本文初步设计和研制了用于大尺度组织低温冷冻保存系统,并使用人工智能调节器对温度和高度进行耦合控制,以此来实现程序降温仪的功能。实验测定了低温冷冻装置内的轴向温度分布,并对比了冷冻容器尺寸对温度分布的影响。实验表明如果容器直径太大,容器内由于自然对流会影响温度分布。由于消除了对流,降温容器内的温度分布更趋近于线性。根据研究结果对新系统进行了改进设计。此装置可以在实验过程中对大块生物组织进行冷冻,以达到快速冷冻的要求。更多还原

【Abstract】 Cryopreservation is a widely accepted method for the long-term preservation of cells and tissues. It has many potential applications in various fields. For example, it is used for the long-term storage of cells in laboratory and, for various diseases treatment in clinical medicine, and for the fresh foods storage. During the process of cryopreservation, there exists a complex mass and heat transfer process in tissue and cell. Moreover it has been proven to be the dominating controlling step for a successful preservation. Therefore, the studying of some problems before, during and after freezing processes is much more significant to optimize the cryopreserve protocol and to deeply understand the principle of the cryopreservation of tissues and cells.This paper calculates the problem of moving boundary of pure water, then it uses commercial FLUENT code to simulate the heat transfer during water freezing, and obtains the temperature and pushing velocity distribution in the structure. It is helpful for the future work to cryopreserve the large-scale tissues.At the same time, this paper measures the osmolalities of DMSO by osmometer and absorption areas of the DMSO by chromatogram, and plot standard curve and make the linear aggression. The aim of the process is to measure the concentration of DMSO indirectly. By comparison, the experiment proves that the osmometer method is a more effective and more convenient one to measure the concentration of DMSO solution. And the methods can also be used to measure the concentrations of other cryoprotectants.Meanwhile, the existing moving boundary in the freezing tissues and cells makes the DMSO to diffuse in solution or within the tissue matrix. The work contributes to the future work on the cryopreservation of large tissues. This paper uses microcapsule as porous media and measured the porosity of the microcapsule by physical method and the diffusion of DMSO in microcapsule. Because there exists a moving boundary in the freezing tissues and cells, the boundary forces the DMSO in solution to diffuse. If the diffusing rate is larger than the pushing rate of the ice boundary, there willproduce a concentration gradient in unfrozen zone. And if the diffusing rate is smaller than the pushing rate of the ice boundary, the solute will be trapped in the frozen area and no concentration gradient, not resulting in a concentrated solution in the unfrozen zone.This paper designs and studies the cryopreservation system for the large-scale tissues and use the artificial intelligence adjuster to control the temperature and height to achieve the function of the program freezing equipment. The paper measures the temperature distribution in cryopreservation equipment and compares the size effect to the temperature distribution. The paper verifies that if the vessel is too large, the natural convection will dominate the process and affect the temperature distribution. The temperature distribution in freezing vessel fit linear better. Based on the experiment result, the paper improved the system and it can use fast freezing rate to cryopreserve large-scale tissues.更多还原