Adams Dana R, Toner Mehmet, Langer Robert
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Langmuir. 2008 Aug 5;24(15):7688-97. doi: 10.1021/la703835w. Epub 2008 Jul 10.
Anhydrobiotic preservation potentially provides a means of long-term storage of mammalian cells in carbohydrate glasses under ambient conditions. During desiccation, sessile droplets of glass-forming carbohydrate solutions exhibit complex phenomena, including fluid flow, droplet deformation, and crack formation, all of which may alter the cell preservation efficacy. Cell-sized liposomes were employed as a model system to explore these phenomena in diffusively dried sessile droplets of trehalose solutions. Two factors were identified that strongly influenced the features of the desiccated droplets: the underlying surface and the liposomes themselves. In particular, the surface altered the droplet shape as well as the microflow pattern and, in turn, the moisture conditions encountered by the liposomes during desiccation. A ring deposit formed when the droplets were dried on polystyrene, as would be expected owing to the capillary flow that generally occurs in pinned droplets. In contrast, when dried on the more hydrophilic glass slide, the resulting droplets were thinner, and the liposomes accumulated near their centers, which was an unexpected result likely owing to the glass-forming nature of trehalose solutions. As might be anticipated given the variations in liposome distribution, the choice of surface also influenced crack formation upon continued drying. In addition to providing a preferential path for drying, such cracks are relevant because they could inflict mechanical damage on cells. The liposomes themselves had an even more profound effect on crack formation; indeed, whereas cracks were found in all droplets containing liposomes, in their absence few of the droplets cracked at all, regardless of the surface type. These complex drying dynamics merit further investigation in the development of anhydrobiotic preservation protocols, particularly with regard to the role therein of surface hydrophobicity and the cells themselves.
无水生境保存可能提供一种在环境条件下将哺乳动物细胞长期储存在碳水化合物玻璃中的方法。在干燥过程中，形成玻璃的碳水化合物溶液的固定液滴会呈现出复杂的现象，包括流体流动、液滴变形和裂纹形成，所有这些都可能改变细胞保存效果。细胞大小的脂质体被用作模型系统，以探索海藻糖溶液扩散干燥固定液滴中的这些现象。确定了两个强烈影响干燥液滴特征的因素：底层表面和脂质体本身。特别是，表面改变了液滴形状以及微流模式，进而改变了脂质体在干燥过程中遇到的湿度条件。当液滴在聚苯乙烯上干燥时会形成环形沉积物，这是由于固定液滴中通常会发生的毛细管流动所预期的。相比之下，当在更亲水的载玻片上干燥时，形成的液滴更薄，脂质体在其中心附近聚集，这是一个意外结果，可能是由于海藻糖溶液的玻璃形成性质。鉴于脂质体分布的变化，可以预期表面的选择也会影响继续干燥时的裂纹形成。除了为干燥提供优先路径外，这些裂纹也很重要，因为它们可能对细胞造成机械损伤。脂质体本身对裂纹形成有更深远的影响；事实上，虽然在所有含有脂质体的液滴中都发现了裂纹，但在没有脂质体的情况下，无论表面类型如何，很少有液滴会开裂。在无水生境保存方案的开发中，特别是关于表面疏水性和细胞本身在其中的作用，这些复杂的干燥动力学值得进一步研究。
