Abstract
We have developed the novel cryoprotective agents of carboxylated poly-L-lysines (COOH-PLLs) for cell cryopreservation alternative to dimethyl sulfoxide. Here in order to study the mechanisms of the cryoprotection of these polyampholytes, we have measured ice including salt and agents by NMR and evaluated the amount and dynamics of the agents, water, and salt in a freezing state. The NMR measurements revealed that COOH-PLLs have a potential to increase residual water in the ice and change the state of sodium ions into distinctive two states. The one Na component rapidly broadened and disappeared upon cooling, indicating COOH-PLLs likely reduce the contribution of Na to the osmotic pressure. We propose the mechanism of cryoprotection of COOH-PLLs is to keep cells away from the stresses like the drastic changes in the size of soluble space and osmotic pressure.
