Introduction: Stabilization of Dry Biological Materials

Storage of biomaterials in a dry state is an attractive proposition economically since it obviates the need for freezers and it is much more convenient than maintaining a cold chain during shipping. Furthermore, materials stored in a dry state might be expected to show enhanced stability—provided the material can be successfully reduced to dryness without introducing irreparable damage during the process. A number of laboratories around the world have been attacking this problem by studying organisms that naturally survive dehydration in nature, a phenomenon known as “anhydrobiosis” (life without water). If an understanding of how such organisms survive drying can be achieved, that knowledge should be applicable to materials and even living cells that do not normally survive such harsh treatment. Indeed, some success has already been achieved in this regard. Early studies from my own laboratory on the chemistry of anhydrobiotic organisms suggest that the synthesis of large quantities of trehalose, a disaccharide of glucose, is a wide-spread adaptation of these organisms. It is already known from a series of studies over the past four decades that trehalose and some other sugars have the ability to stabilize biological membranes, proteins, and even human platelets in the dry state, ¹ findings that have led to many commercial applications. ²

Much has been made of the stabilizing properties of trehalose, but that is clearly not the entire story. In fact, it has become apparent in recent years that possibly the most celebrated of the anhydrobiotic organisms, the tardigrades, contain little or no trehalose. Thus, these organisms must employ alternative mechanisms for achieving stability. One might suppose that modern methods of genomics would be useful in identifying such mechanisms, and even though few and far between, such studies are beginning to appear. ³

The three reports that follow in this issue are based on presentations in a symposium on freeze drying and anhydrobiosis at the annual meeting of the Society for Cryobiology in 2011. These reports present results showing that trehalose does contribute to the preservation of dry DNA, proteins, and mammalian cells, but with distinctly novel extensions from the mechanisms currently regarded as folk wisdom. For example, both Oliver and Arav show that although trehalose can stabilize nucleated cells and human red blood cells, it alone is not sufficient for either long-term preservation or for preservation under physiological conditions after the cells are rehydrated. Both authors suggest new approaches to stabilizing such cells that are based on additional chemistry from anhydrobiotic organisms and are more complex than previously investigated techniques.In the third article, Muller and his colleagues report the use of a large library of molecules that share chemical characteristics with trehaloseto investigate efficacy in stabilizing DNA. They found that several of the molecules are at least as effective as trehalose, and a few are superior. These investigators are examining the application of such molecules in stabilizing more complex systems.

These reports and the work that is sure to follow are certain to find a prominent place in the world of biotechnology devoted to enhancing biomolecule stability. Further, the exciting work on the genomics of anhydrobiotic organisms ³ holds the promise of providing further refinements of this endeavor.