Towards storage of cells and gametes in dry form

• Liquid nitrogen is the current golden standard for cell and gamete preservation.
• Liquid nitrogen storage is effective, but costly, and presents some practical and safety concerns.
• Lyophilization has been successfully applied to mammalian spermatozoa.
• Dry storage is a promising approach for long-term preservation of cells and gametes.

We review published data on cell/gamete lyophilization. Most studies have utilized the same established protocols for cryopreservation (storage in liquid nitrogen) as for cell lyophilization (dehydration of frozen samples by water sublimation). Surveying natural lyoprotectants, we suggest trehalose and late embryogenesis abundant (LEA) proteins as ideal candidates for the reversible desiccation of mammalian cells/gametes. We find that despite the numerous water subtraction techniques, scientists have relied almost exclusively on lyophilization. There is thus room for improvement in both medium formulation and water subtraction strategies for dry cell/gamete storage. We believe the development of dry processing protocols for use in biobanks of cells/gametes, at reduced cost and with minimal carbon footprint, is within our grasp.