A new approach for freezing of aqueous solutions under active control of the nucleation temperature
A new approach for freezing of aqueous solutions under active control of the nucleation temperature
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DOI：
10.1016/j.cryobiol.2006.06.005
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发表时间：
2006-10-01
期刊：
影响因子：
2.7
通讯作者：
Glasmacher, Birgit
中科院分区：
文献类型：
--
作者：
Petersen, Ansgar;Schneider, Hendrik;Glasmacher, Birgit
介绍了一种水溶液控制冷冻的实验装置。其特点是通过电冷冻主动控制成核温度的机制：通过施加高压电脉冲在铂电极上产生的冰核引发样品的结晶。使用电冷冻，纯水中的成核温度可以在接近熔点的最高温度Tn（max）和自发成核温度之间的整个温度范围内精确地调节到期望值。然而，添加剂的存在会抑制成核。研究了羟乙基淀粉（HES）、葡萄糖、甘油、低温生物学常用添加剂和NaCl对T_n（max）的影响。虽然非离子添加剂的减少是适度的，但离子NaCl对成核的阻碍使得在具有生理盐浓度的溶液中直接应用电冷冻是不可能的。因此，在本文提出的多样品冷冻装置中，冰核在电极帽内的单独体积的纯水中产生。这样，成核变得与样品组成无关。使用电冷冻而不是传统的接种方法允许在相同条件下自动冷冻许多样品。使用模型溶液进行的实验表明，该方法在不同的规定温度下在供试品中开始结晶的可靠性和可重复性。该设置的目的是冻结小体积的样品在低温保存和冷冻干燥领域的基础研究，但操作模式可能是有趣的许多其他应用程序，其中控制成核的水溶液是很重要的。(c)2006年爱思唯尔公司All rights reserved.
An experimental setup for controlled freezing of aqueous solutions is introduced. The special feature is a mechanism to actively control the nucleation temperature via electrofreezing: an ice nucleus generated at a platinum electrode by the application of an electric high voltage pulse initiates the crystallization of the sample. Using electrofreezing, the nucleation temperature in pure water can be precisely adjusted to a desired value over the whole temperature range between a maximum temperature T-n(max) close to the melting point and the temperature of spontaneous nucleation. However, the presence of additives can inhibit the nucleus formation. The influence of hydroxyethylstarch (HES), glucose, glycerol, additives commonly used in cryobiology, and NaCl on T-n(max) were investigated. While the decrease showed to be moderate for the non-ionic additives, the hindrance of nucleation by ionic NaCl makes the direct application of electrofreezing in solutions with physiological salt concentrations impossible. Therefore, in the multi-sample freezing device presented in this paper, the ice nucleus is produced in a separate volume of pure water inside an electrode cap. This way, the nucleus formation becomes independent of the sample composition. Using electrofreezing rather than conventional seeding methods allows automated freezing of many samples under equal conditions. Experiments performed with model solutions show the reliability and repeatability of this method to start crystallization in the test samples at different specified temperatures. The setup was designed to freeze samples of small volume for basic investigations in the field of cryopreservation and freeze-drying, but the mode of operation might be interesting for many other applications where a controlled nucleation of aqueous solutions is of importance. (c) 2006 Elsevier Inc. All rights reserved.