Abstract
We developed novel cryoprotective agents from carboxylated ε-poly-L-lysines (COOH-PLLs) for cell cryopreservation as alternatives to dimethyl sulfoxide (DMSO). The polymeric agents showed excellent cell viability profile for most cell types, including human mesenchymal stem cells. We investigated the molecular states and mobility of the solvents and solutes in ice at low temperatures by using solid-state nuclear magnetic resonance (NMR). The NMR data suggested that DMSO and COOH-PLLs differently affect the states and mobility of water and solutes in ice. The former retains the mobility at low temperature, while the latter restricts the mobility by trapping the molecules in soluble aggregates. We propose that cryoprotection of COOH-PLLs is exerted by protecting cells from stresses such as drastic changes in soluble space size and osmotic pressure during freezing.
