Review of biomaterial thermal property measurements in the cryogenic regime and their use for prediction of equilibrium and non-equilibrium freezing applications in cryobiology.
Review of biomaterial thermal property measurements in the cryogenic regime and their use for prediction of equilibrium and non-equilibrium freezing applications in cryobiology.
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DOI：
10.1016/j.cryobiol.2009.11.004
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发表时间：
2010-02
期刊：
影响因子：
2.7
通讯作者：
Bischof, John C.
中科院分区：
文献类型：
--
作者：
Choi, Jeunghwan;Bischof, John C.
关键词：
在冷冻生物学中公认的是，生物材料在冷冻过程中经历的温度历史和冷却速率与生物学结果密切相关。因此，在低温状态下的传热测量和预测是该领域的核心。虽然可以直接测量热传递，但通常仅在给定系统内的局部测量中实现准确性，并且在没有预测模型的帮助下不能容易地推广到另一个系统。这些模型的准确性依赖于已知高度依赖于温度的热性质，并且在显著的冷冻保护剂加载的情况下，还依赖于结晶部分。在这项工作中，我们审查了生物材料在低温制度的可用热性能。该综述表明，许多生物材料在零度以下的温度域中缺乏性能，特别是对于具有低温保护剂的系统。不幸的是，使用有限的数据（通常仅低至-40 °C）导致低估了较低温度下的热性能变化（即由于冰结晶导致的电导率上升和比热降）。相反，使用替代值的基础上，冰的热性能导致高估的热性能变化的大多数生物材料。此外，最近的工作将可用的热性能范围扩展到−150 °C，表明由于生物材料的无定形/玻璃态（与冰相比），加入甘油等防冻添加剂，PBS和组织（肝脏）的热导率都会下降。因此，我们研究了使用近似或恒定的属性值与测量的温度依赖性值预测在PBS（磷酸盐缓冲盐水）和猪肝中的热传递和无冷冻保护剂（甘油）的影响。使用猪肝的测量属性值（导热系数、比热和相变潜热），创建了一个标准，该标准表明基于替代冰属性的值低于预测的冷却时间，而恒定属性（即基于冰点附近报告的有限数据）超过预测的冷却时间。此外，一种新的迭代数值方法，适应非平衡冷却效应作为时间和位置的函数（即结晶与非晶相）被用来预测在甘油加载系统的传热。结果表明，除了冷却时间的增加，由于热扩散率降低更多的甘油，非平衡效应，如防止最大结晶（即无定形相）将进一步增加所需的冷却时间。这些结果证实了需要使用精确的热性能，包括温度依赖性和结晶分数。需要进一步的研究，以提取其他重要的生物材料在零度以下的温度域的热性能，并开发精确的数值方法，考虑到非平衡冷却事件时，在低温生物学中遇到的部分或全部玻璃化发生。
It is well accepted in Cryobiology that the temperature history and cooling rates experienced in biomaterials during freezing procedures correlate strongly with biological outcome. Therefore, heat transfer measurement and prediction in the cryogenic regime is central to the field. Although direct measurement of heat transfer can be performed, accuracy is usually achieved only for local measurements within a given system and cannot be readily generalized to another system without the aid of predictive models. The accuracy of these models rely upon thermal properties which are known to be highly dependent on temperature, and in the case of significant cryoprotectant loading, also on crystallized fraction. In this work we review the available thermal properties of biomaterials in the cryogenic regime. The review shows a lack of properties for many biomaterials in the subzero temperature domain, and especially for systems with cryoprotective agents. Unfortunately, use of values from the limited data available (usually only down to −40 °C) lead to an underestimation of thermal property change (i.e. conductivity rise and specific heat drop due to ice crystallization) with lower temperatures. Conversely, use of surrogate values based solely on ice thermal properties lead to an overestimation of thermal property change for most biomaterials. Additionally, recent work extending the range of available thermal properties to −150 °C has shown that the thermal conductivity will drop in both PBS and tissue (liver) due to amorphous/glassy phases (vs. ice) of biomaterials with the addition of cryoprotective additives such as glycerol. Thus, we investigated the implications of using approximated or constant property values versus measured temperature-dependent values for predicting heat transfer in PBS (phosphate buffered saline) and porcine liver with and without cryoprotectants (glycerol). Using measured property values (thermal conductivity, specific heat, and latent heat of phase change) of porcine liver, a standard was created which showed that values based on surrogate ice properties under-predicted cooling times, while constant properties (i.e. based on limited data reported near the freezing point) over-predicted cooling times. Additionally, a new iterative numerical method that accommodates non-equilibrium cooling effects as a function of time and position (i.e. crystallization vs. amorphous phase) was used to predict heat transfer in glycerol loaded systems. Results indicate that in addition to the increase in cooling times due to the lowering of thermal diffusivity with more glycerol, non-equilibrium effects such as the prevention of maximal crystallization (i.e. amorphous phases) will further increase required cooling times. These results affirm the need to use accurate thermal properties that incorporate temperature dependence and crystallized fraction. Further studies are needed to extract thermal properties of other important biomaterials in the subzero temperature domain and to develop accurate numerical methods which take into account non-equilibrium cooling events encountered in cryobiology when partial or total vitrification occurs.
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影响因子：
--
作者：
BALASUBR.TA;BOWMAN, HF
通讯作者：
BOWMAN, HF
DOI：
10.1111/j.1749-6632.1980.tb50742.x
发表时间：
1980-01-01
影响因子：
5.2
作者：
Chen, M M;Holmes, K R
通讯作者：
Holmes, K R
DOI：
10.1115/1.2895422
发表时间：
1991-11-01
影响因子：
1.7
作者：
BAI, XM;PEGG, DE
通讯作者：
PEGG, DE
影响因子：
2.7
作者：
BOUTRON, P;DELAGE, D;KORBER, C
通讯作者：
KORBER, C
影响因子：
2.7
作者：
BOUTRON, P;KAUFMANN, A
通讯作者：
KAUFMANN, A