Sol-gel processing of actin to obtain homogeneous glasses at low temperatures.

The lethal effects of freezing on cells are currently attributed to the crystallization of extracellular water which leaves concentrated solutions of salts, macromolecules and so forth in the extracellular space. This concentrated fluid establishes a strong osmotic gradient which draws water from the cells. Thus, a cell surrounded by ice can survive only if means can be found for reducing the osmotically driven outflow of cellular water. This is usually attempted through vitrification of the extracellular space, but may also be attained through suitable modifications of cellular plasms. Starting from microscopic observations on early rabbit embryos and related cryotolerance, we investigated purified actin solutions under similar conditions, and found that sol-gel processing could result in the formation of homogeneous glass, and through drying, give rise to monolithic solids, glasses and composites. The first process may be at least partially responsible for the induced cryotolerance of cells, while the second may be representative of new and useful biomaterials.