Grenke Julia H, Elliott Janet A W
Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada.
J Phys Chem B. 2025 Feb 20;129(7):2013-2029. doi: 10.1021/acs.jpcb.4c03915. Epub 2025 Feb 11.
Cryopreservation is the preservation and storage of biomaterials using low temperatures. There are several approaches to cryopreservation, and these often include the use of cryoprotectants, which are solutes used to lower the freezing point of water. Isochoric (constant-volume) cryopreservation is a form of cryopreservation that has been gaining interest over the past 18 years. This method utilizes the anomalous nature of water in that it expands as it freezes. The expansion of ice on freezing is used to induce a pressure in the system that limits ice growth. In this work, we use Gibbsian thermodynamics, the Elliott et al. multisolute osmotic virial equation, the Feistel and Wagner correlation for ice Ih, and the Grenke and Elliott correlation for the thermodynamic properties of liquid water at low temperatures and high pressures to predict how the pressure, volume fraction of ice, and solute concentration in the unfrozen fraction change as the solution is cooled isochorically. We then verified our model by predicting experimental results for saline solutions and ternary aqueous solutions containing NaCl and organic compounds commonly used as cryoprotectants: glycerol, ethylene glycol, propylene glycol, and dimethyl sulfoxide. We found that our model accurately predicts experimental data that were collected for cryoprotectant concentrations as high as 5 M, and temperatures as low as -25 °C. Since we have shown that our liquid water correlation, on which this work was based, makes accurate predictions to -70 °C, as long as the pressure is not higher than 400 MPa, we anticipate that the prediction methods presented in this work will be accurate down to -70 °C. In this work we also modeled how sealing the isochoric chamber at room temperature versus at the nucleation temperature impacts isochoric freezing. The prediction methods developed in this work can be used in the future design of isochoric cryopreservation experiments and protocols.
低温保存是利用低温对生物材料进行保存和储存。低温保存有多种方法，这些方法通常包括使用冷冻保护剂，冷冻保护剂是用于降低水冰点的溶质。等容（恒容）低温保存是过去18年来逐渐受到关注的一种低温保存形式。该方法利用了水的反常性质，即水在结冰时会膨胀。结冰时冰的膨胀用于在系统中产生压力，从而限制冰的生长。在这项工作中，我们使用吉布斯热力学、埃利奥特等人的多溶质渗透维里方程、冰Ih的费斯泰尔和瓦格纳相关性以及格林克和埃利奥特关于低温高压下液态水热力学性质的相关性，来预测在溶液等容冷却过程中压力、冰的体积分数以及未冻结部分的溶质浓度如何变化。然后，我们通过预测含有NaCl和常用冷冻保护剂（甘油、乙二醇、丙二醇和二甲基亚砜）的盐溶液和三元水溶液的实验结果来验证我们的模型。我们发现，我们的模型能够准确预测在高达5 M的冷冻保护剂浓度和低至-25°C的温度下收集的实验数据。由于我们已经表明，这项工作所基于的液态水相关性在压力不高于400 MPa的情况下，能够准确预测到-70°C，我们预计这项工作中提出的预测方法在低至-70°C时仍将是准确的。在这项工作中，我们还模拟了在室温与成核温度下密封等容腔室对等容冷冻的影响。这项工作中开发的预测方法可用于未来等容低温保存实验和方案的设计。
