超高速冷冻过程中的细薄膜蒸发传热及其强化机理和细胞玻璃化冷冻研究

Cell cryopreservation is essential to many areas such as biodiversity conservation, improvement of livestock species, and human assisted reproduction. Cell vitrification based on cryogenic thin film evaporation of liquid nitrogen is one of the efficient cell cryopreservation approaches because it only requires relatively simple operations and has low damage to cell. Scientific problems in the novel approach, such as cryogenic thin film evaporation of liquid nitrogen and vitrification of the solution on the condition of ultra-fast cooling are investigated. On the one hand, the distribution of liquid nitrogen on the surface of the cooling container and the microscopic relation between the effects of liquid-vapor/solid- liquid interface and the distribution is paid our attention, and the mechanism of the cryogenic thin film evaporation heat transfer on the condition of high superheat. On the other hand, the migration behavior of water in the solutions inside and outside the cells, the forming and growth behavior of ice crystal is investigated from microscopic and macroscopic angles. The model of the vitrification of the solutions inside and outside the cells is developed. On the base of the fore investigations, the ultro-fast cooling and the vitrification of cells is optimized to improve the cooling rate in the vitrification. As a result, the vitrification of cell suspensions without cryoprotective agents or with relatively low concentrations of cryoprotective agents (<1mol/l) is expected.

细胞的超低温保存在生物多样性保护,家畜物种改良,人类辅助生殖等诸多领域有着广泛的应用。而基于液氮细薄膜蒸发的超高速细胞玻璃化冷冻新方法操作简单，对细胞损伤小，是实现细胞超低温保存的有效途径之一。本项目针对这种新方法中存在的超低温条件下细薄膜蒸发、超高速降温条件下的溶液玻璃化等基础科学问题开展研究。一方面关注液氮在冷冻载体毛细结构表面的分布行为及其与液固、汽液界面作用的微观联系，研究在超低温，大过热度条件下的细薄膜蒸发传热及强化机理；另一方面从微观与宏观两个角度，认识超高速冷冻过程中细胞内外溶液中水分的迁移行为，冰晶核的形成及成长行为，构建超高速降温条件下细胞内外溶液玻璃化转变的模型；最终两者结合，优化超高速细胞玻璃化冷冻过程，提高细胞冷冻过程中的降温速率。优化后的新方法可望实现无低温保护剂或者低浓度（<1mol/l）低温保护剂条件下细胞高效玻璃化冷冻保存。

细胞的超低温保存在生物多样性保护,家畜物种改良,人类辅助生殖等诸多领域有着广泛的应用。而基于液氮细薄膜蒸发的超高速细胞玻璃化冷冻新方法操作简单，对细胞损伤小，是实现细胞超低温保存的有效途径之一。本项目针对这种新方法中存在的超低温条件下细薄膜蒸发、超高速降温条件下的溶液玻璃化等基础科学问题开展了系统的实验与理论研究工作。研究取得的重要进展如下：1. 掌握了此种发生在微细结构表面的超大过热度的非稳态传热过程中的热流通量、总传热热阻、液氮蒸发传热系数的变化规律。以此为指导，优化了液氮细薄膜蒸发过程，获得了细胞玻璃化冷冻所需要的超高冷却速率。2. 认识了细胞溶液的物性、低温保护剂浓度、冷却速率等参数对溶液玻璃化趋势的影响规律，建立了超高速条件下细胞溶液玻璃化的数学模型。3.构建了基于液氮细薄膜蒸发的冷冻新装置，实现了细胞的超高速玻璃化冻存。新方法可以获得80%以上的细胞存活率，证实了超高速冷冻新方法用于细胞超低温保存的可行性。本项目的研究将为基于液氮细薄膜蒸发的超高速细胞玻璃化冷冻新方法走向实用化提供有力的技术支持。