The Importance of Heat Flow Direction for Reproducible and Homogeneous Freezing of Bulk Protein Solutions
The Importance of Heat Flow Direction for Reproducible and Homogeneous Freezing of Bulk Protein Solutions
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DOI：
10.1002/btpr.1771
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发表时间：
2013-09-01
影响因子：
2.9
通讯作者：
Geraldes, Vitor
中科院分区：
文献类型：
--
作者：
Rodrigues, Miguel A.;Balzan, Gustavo;Geraldes, Vitor
冷冻是生物治疗行业的重要操作。然而，在含有电解质、糖和蛋白质的溶液中，水结晶是难以控制的，并且通常导致实质性的空间溶质异质性。在这里，我们解决的冻结方向（轴向或径向）的几何形状的冻结基质的异质性的影响，在局部浓度的溶质和热历史。血红蛋白溶液的径向和轴向冷冻使用小规模和中试规模的冷冻系统。通过冰芯取样测量了血红蛋白、蔗糖和pH值的浓度，并在几个地点测量了温度分布。结果表明，自然对流是溶质在容器几何形状上的低温浓缩不均匀性的主要来源。当冻结几何形状为非对流时，即，冻结锋从底部到顶部是单向的。使用这种几何形状，在整个冷冻溶液中获得小于10%的溶质浓度变化。即使当体积增加两个数量级（从30 mL到3 L）时，该结果也是可重现的。使用一个相对简单的计算流体动力学模型的非对流冻结几何形状的温度分布进行了预测。可再现的溶质分布、可预测的温度曲线和可扩展性表明，从底部到顶部的冷冻几何形状能够对冷冻过程进行扩展控制。因此，这种几何形状显示出有助于更好地理解和控制冷冻储存固有风险的潜力。(c)2013年美国化学工程师学会生物技术。程序，29：1212-1221，2013
Freezing is an important operation in biotherapeutics industry. However, water crystallization in solution, containing electrolytes, sugars and proteins, is difficult to control and usually leads to substantial spatial solute heterogeneity. Herein, we address the influence of the geometry of freezing direction (axial or radial) on the heterogeneity of the frozen matrix, in terms of local concentration of solutes and thermal history. Solutions of hemoglobin were frozen radially and axially using small-scale and pilot-scale freezing systems. Concentration of hemoglobin, sucrose and pH values were measured by ice-core sampling and temperature profiles were measured at several locations. The results showed that natural convection is the major source for the cryoconcentration heterogeneity of solutes over the geometry of the container. A significant improvement in this spatial heterogeneity was observed when the freezing geometry was nonconvective, i.e., the freezing front progression was unidirectional from bottom to top. Using this geometry, less than 10% variation in solutes concentration was obtained throughout the frozen solutions. This result was reproducible, even when the volume was increased by two orders of magnitude (from 30 mL to 3 L). The temperature profiles obtained for the nonconvective freezing geometry were predicted using a relatively simple computational fluid dynamics model. The reproducible solutes distribution, predictable temperature profiles, and scalability demonstrate that the bottom to top freezing geometry enables an extended control over the freezing process. This geometry has therefore shown the potential to contribute to a better understanding and control of the risks inherent to frozen storage. (c) 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1212-1221, 2013