Dimethyl sulfoxide (DMSO) and several naturally occurring polyols or their derivatives (like glycerol) have been used as cryoprotective agents (CPAs) for many years. However DMSO shows high cytotoxicity and affects differentiation of cells, so it needs to be removed immediately after thawing, whereas polyols are comparatively weaker cryoprotective agents. Furthermore, some types of cells are extremely sensitive to damage during freezing and thawing, so cannot be cryopreserved properly using current CPAs. So there is a great need to develop newer cryoprotective agents with lower cytotoxicity and high efficiency for many biological and medical purposes.
Recently we showed that carboxylated poly-L-lysine, which is classified as a polyampholyte, has a cryoprotective effect on cells in solution without any other cryoprotectant. Polyampholytes are charged polymers with both positively and negatively charged groups.
Therefore, in this research, we are developing a completely synthetic polyampholytes by radical polymerization and will try to elucidate the key parameters of cryoprotective properties. Here we chose reversible addition fragmentation chain transfer (RAFT) polymerization as the mode of polymerization as it is a kind of living polymerization method and can give control over the molecular weight and composition of the copolymer. We evaluated the livingness of the 1:1 copolymer with methacrylic acid (MAA) and 2-Dimethylamino ethyl methacrylate (DMAEMA) with 2-(Dodecylthiocarbonothioylthio)-2-methylpropionic acid as the RAFT agent and the polymer solution showed good cell viability of L929 cells after cryopreservation at 15% copolymer concentration.