Osmolytes as Cryoprotectants Under Salt Stress

Cryoprotecting agent (CPAs)-guided preservation is essential for effective protection of cells from cryo-injuries. But current cryoprotecting technologies practised to cryopreserve cells for biomedical applications are met with extreme challenges due to associated toxicity of CPAs. Because of these limitations of present CPAs, the quest for nontoxic alternative for useful application in cell-based biomedicines is attracting growing interest. Towards this end, here we investigate naturally occurring osmolytes' scope as biocompatible cryoprotectant under cold-stress condition in high saline medium. Via a combination of simulation and experiment on charged silica nano-structures, we render first-hand evidence that a pair of archetypal osmolytes glycine and betaine would act as cryoprotectant by restoring indigenous inter-surface electrostatic interaction, which had been a priori screened due to cold-effect under salt stress. While these osmolytes' individual modes of action are sensitive to the subtle chemical variation, a uniform augmentation in the extent of osmolytic activity is observed with increase in temperature to counter the proportionately enhanced salt screening. The trend as noted in inorganic nano-structures is found to be recurrent and robustly transferrable in a charged protein interface. In hindsight, our observation justifies the sufficiency of reduced requirement of osmolytes in cells during critical cold condition and encourages their direct usage and biomimicry for cryopreservation.