With the wide-spread possibility of clinical applications of cell-based therapies, there is an obvious need to develop long-term storage strategies for these cell-based products. At present, cryopreservation is the only established long term preservation method for mammalian cells. This storage method requires cryogenic temperatures and for that reason it has practical problems related to transportation and distribution, and entails significant costs. Also cryopreservation techniques require that cryoprotectants are carefully loaded and unloaded under highly controlled conditions. This limits the field of utilization of cryopreserved biological samples.

Dry-preservation at ambient temperatures may be an alternative and more flexible strategy for long term mammalian cell preservation. Nature provides ample examples of organisms that can survive extended periods of drought in a suspended animation state, such as tardigrades, yeast, brine shrimp, and seeds. These desiccation tolerant species, called anhydrobiotes, are known to accumulate the glass-forming disaccharide trehalose in response to dehydration stress, and this is thought to play a major role in their ability to withstand storage in the dry state. By increasing the concentration of intracellular trehalose in mammalian cells improvements have been made in dehydration tolerance, but so far a long term dry preservation solution has not been possible. Even with intracellular trehalose, mammalian cells die at moisture contents well above the state where dry-preservation at ambient temperatures is theoretically possible.

Ultimately, to achieve a stable matrix suitable for long-term storage, the viscosity needs to approach a level that renders the sample 'glassy' or solid-like at the given storage temperature. For room temperature storage, a trehalose-based sample requires dehydration to below 0.1 gH₂O/gdw. Because water acts as a plasticizer in these storage formulations, wetter samples will have a lower glass transition temperature. The goal of this work was to advance towards dry preservation at room temperature by first achieving a level of dehydration that can enable storage at -80°C, a temperature that can be achieved with electric freezers, thus avoiding the need for expensive cryogens for long-term bio-banking. Advances were made that improved the limits of dehydration that can be tolerated by mammalian cells during processing for dry preservation. A cumulative osmotic stress model of drying injury was proposed and evaluated to enable the rationale design of drying protocols. Using this model as a guide, osmometric modifications were made to existing dry-preservation protocols to reduce the magnitude of cumulative osmotic stress experienced by cells. This improved the overall outcome, enabling full cell functionality to be retained at lower moisture contents. A novel microwave-based drying technique for mammalian cells was also developed to enable rapid dehydration of biological samples, thus reducing cumulative chemical stresses that occurred during processing. Finally a multiscale analysis of drying metrics was undertaken. Gravimetry based macroscale metrics were compared to the microscale measures obtained with time-resolved fluorescence spectroscopy techniques. The difference between these metrics highlighted the need to study drying characteristics at a microscopic level.

Through a systematic study of solution effect injury this body of work enabled significant advances towards the dry preservation of mammalian cells at ambient temperatures. The level of reversible dehydration achieved to date may be adequate to enable long-term storage at temperatures approaching -80°C, thus eliminating the need maintain storage conditions at -196°C.